Sample records for vadose zone hydrology

  1. Vadose Zone Hydrology and Eco-hydrology in China

    NASA Astrophysics Data System (ADS)

    Wang, Wenke

    2016-04-01

    Vadose zone hydrology has long been a concern regarding groundwater recharge, evaporation, pollution, and the ecological effects induced by groundwater and water & salt contents in the unsaturated zone. The greater difference between day and night temperatures in arid and semi-arid areas influences water movement and heat transport in the vadose zone, and further influences the water and heat fluxes between the water table and the atmosphere as well as ecological environment. Unfortunately, these studies are lack in a systematic viewpoint in China. One of the main reasons is that the movement of water, vapor and heat from the surface to the water table is very complex in the arid and semi-arid areas. Another reason is lack of long term field observations for water content, vapor, heat, and soil matrix potential in the vadose zone. Three field observation sites, designed by the author, were set up to measure the changes in climate, water content , temperature and soil matrix potential of the unsaturated zone and groundwater level under the different conditions of climate and soil types over the period of 1-5 years. They are located at the Zhunngger Basin of Xinjing Uygur Autonomous Region in northwestern China, the Guanzhong Basin of Shaanxi Province in central China, and the Ordos Basin of the Inner Monggol Autonomous Region in north China, respectively. These three field observation sites have different climate and soil types in the vadose zone and the water table depth are also varied. Based on the observation data of climate, groundwater level, water content, temperature and soil matrix potential in the vadose zone from the three sites in associated with the field survey and numerical simulation method, the water movement and heat transport in the vadose zone, and the evaporation of phreatic water for different groundwater depths and soil types have been well explored. The differences in water movement of unsaturated zone between the bare surface soil and

  2. Hydrologic processes in deep vadose zones in interdrainage arid environments

    USGS Publications Warehouse

    Walvoord, Michelle Ann; Scanlon, Bridget R.; Hogan, James F.; Phillips, Fred M.; Scanlon, Bridget R.

    2004-01-01

    A unifying theory for the hydrology of desert vadose zones is particularly timely considering the rising population and water stresses in arid and semiarid regions. Conventional models cannot reconcile the apparent discrepancy between upward flow indicated by hydraulic gradient data and downward flow suggested by environmental tracer data in deep vadose zone profiles. A conceptual model described here explains both hydraulic and tracer data remarkably well by incorporating the hydrologic role of desert plants that encroached former juniper woodland 10 to 15 thousand years ago in the southwestern United States. Vapor transport also plays an important role in redistributing moisture through deep soils, particularly in coarse-grained sediments. Application of the conceptual model to several interdrainage arid settings reproduces measured matric potentials and chloride accumulation by simulating the transition from downward flow to upward flow just below the root zone initiated by climate and vegetation change. Model results indicate a slow hydraulic drying response in deep vadose zones that enables matric potential profiles to be used to distinguish whether precipitation episodically percolated below the root zone or was completely removed via evapotranspiration during the majority of the Holocene. Recharge declined dramatically during the Holocene in interdrainage basin floor settings of arid and semiarid basins. Current flux estimates across the water table in these environmental settings, are on the order of 0.01 to 0.1 mm yr-1 and may be recharge (downward) or discharge (upward) depending on vadose zone characteristics, such as soil texture, geothermal gradient, and water table depth. In summary, diffuse recharge through the basin floor probably contributes only minimally to the total recharge in arid and semiarid basins.

  3. Optimization of remediation strategies using vadose zone monitoring systems

    NASA Astrophysics Data System (ADS)

    Dahan, Ofer

    2016-04-01

    In-situ bio-remediation of the vadose zone depends mainly on the ability to change the subsurface hydrological, physical and chemical conditions in order to enable development of specific, indigenous, pollutants degrading bacteria. As such the remediation efficiency is much dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. These conditions are usually determined in laboratory experiments where parameters such as the chemical composition of the soil water solution, redox potential and water content of the sediment are fully controlled. Usually, implementation of desired optimal degradation conditions in deep vadose zone at full scale field setups is achieved through infiltration of water enriched with chemical additives on the land surface. It is assumed that deep percolation into the vadose zone would create chemical conditions that promote biodegradation of specific compounds. However, application of water with specific chemical conditions near land surface dose not necessarily results in promoting of desired chemical and hydraulic conditions in deep sections of the vadose zone. A vadose-zone monitoring system (VMS) that was recently developed allows continuous monitoring of the hydrological and chemical properties of deep sections of the unsaturated zone. The VMS includes flexible time-domain reflectometry (FTDR) probes which allow continuous monitoring of the temporal variation of the vadose zone water content, and vadose-zone sampling ports (VSPs) which are designed to allow frequent sampling of the sediment pore-water and gas at multiple depths. Implementation of the vadose zone monitoring system in sites that undergoes active remediation provides real time information on the actual chemical and hydrological conditions in the vadose zone as the remediation process progresses. Up-to-date the system has been successfully implemented in several studies on water flow and contaminant transport in

  4. Wildfire effects on vadose zone hydrology in forested boreal peatland microforms

    NASA Astrophysics Data System (ADS)

    Thompson, Dan K.; Waddington, James M.

    2013-04-01

    SummaryPeatland vulnerability to wildfire disturbance has been shown to vary as a function of hummock and hollow microforms and vadose zone hydrology, with low-lying hollow microforms most susceptible to deep combustion of peat. To better understand how this microform induced pattern of burning alters vadose water storage, pore-water pressure, and water table relationships, we examined a paired burned and unburned peatland in the boreal plain region of north central Alberta. Water table response to rain events increased significantly after wildfire, resulting in a more variable unsaturated zone thickness that was more responsive to smaller rain events. Water storage losses in the vadose zone occurred primarily at depths greater than 15 cm. Large peat surface water loss occurred in hummock microforms in the early spring due to the presence of unsaturated frozen peat at depth, likely a result of a vapour gradient from the unfrozen peat into the frozen peat underneath. During this period, the loss of water storage in the vadose zone satisfied up to 25% of daily evaporative demand, compared to only 3-5% during ice-free periods. A similar but less severe drying was observed late in summer, with burned hummocks the most vulnerable with high pore-water pressures. The enhanced surface drying observed is a precursor to high pore-water pressure conditions that inhibit Sphagnum regeneration. Our observations point to a paradox where the hummocks, being most resistant to combustion, are themselves most prone to high pore-water pressures following wildfire. The harsher hummock environment may contribute to the observed delay in post-fire Sphagnum regeneration in hummocks compared to hollows.

  5. Optimization of Remediation Conditions using Vadose Zone Monitoring Technology

    NASA Astrophysics Data System (ADS)

    Dahan, O.; Mandelbaum, R.; Ronen, Z.

    2010-12-01

    Success of in-situ bio-remediation of the vadose zone depends mainly on the ability to change and control hydrological, physical and chemical conditions of subsurface. These manipulations enables the development of specific, indigenous, pollutants degrading bacteria or set the environmental conditions for seeded bacteria. As such, the remediation efficiency is dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. Enhanced bioremediation of the vadose zone is achieved under field conditions through infiltration of water enriched with chemical additives. Yet, water percolation and solute transport in unsaturated conditions is a complex process and application of water with specific chemical conditions near land surface dose not necessarily result in promoting of desired chemical and hydraulic conditions in deeper sections of the vadose zone. A newly developed vadose-zone monitoring system (VMS) allows continuous monitoring of the hydrological and chemical properties of the percolating water along deep sections of the vadose zone. Implementation of the VMS at sites that undergoes active remediation provides real time information on the chemical and hydrological conditions in the vadose zone as the remediation process progresses. Manipulating subsurface conditions for optimal biodegradation of hydrocarbons is demonstrated through enhanced bio-remediation of the vadose zone at a site that has been contaminated with gasoline products in Tel Aviv. The vadose zone at the site is composed of 6 m clay layer overlying a sandy formation extending to the water table at depth of 20 m bls. The upper 5 m of contaminated soil were removed for ex-situ treatment, and the remaining 15 m vadose zone is treated in-situ through enhanced bioremedaition. Underground drip irrigation system was installed below the surface on the bottom of the excavation. Oxygen and nutrients releasing powder (EHCO, Adventus) was spread below the

  6. Linking river, floodplain, and vadose zone hydrology to improve restoration of a coastal river affected by saltwater intrusion.

    PubMed

    Kaplan, D; Muñoz-Carpena, R; Wan, Y; Hedgepeth, M; Zheng, F; Roberts, R; Rossmanith, R

    2010-01-01

    Floodplain forests provide unique ecological structure and function, which are often degraded or lost when watershed hydrology is modified. Restoration of damaged ecosystems requires an understanding of surface water, groundwater, and vadose (unsaturated) zone hydrology in the floodplain. Soil moisture and porewater salinity are of particular importance for seed germination and seedling survival in systems affected by saltwater intrusion but are difficult to monitor and often overlooked. This study contributes to the understanding of floodplain hydrology in one of the last bald cypress [Taxodium distichum (L.) Rich.] floodplain swamps in southeast Florida. We investigated soil moisture and porewater salinity dynamics in the floodplain of the Loxahatchee River, where reduced freshwater flow has led to saltwater intrusion and a transition to salt-tolerant, mangrove-dominated communities. Twenty-four dielectric probes measuring soil moisture and porewater salinity every 30 min were installed along two transects-one in an upstream, freshwater location and one in a downstream tidal area. Complemented by surface water, groundwater, and meteorological data, these unique 4-yr datasets quantified the spatial variability and temporal dynamics of vadose zone hydrology. Results showed that soil moisture can be closely predicted based on river stage and topographic elevation (overall Nash-Sutcliffe coefficient of efficiency = 0.83). Porewater salinity rarely exceeded tolerance thresholds (0.3125 S m(-1)) for bald cypress upstream but did so in some downstream areas. This provided an explanation for observed vegetation changes that both surface water and groundwater salinity failed to explain. The results offer a methodological and analytical framework for floodplain monitoring in locations where restoration success depends on vadose zone hydrology and provide relationships for evaluating proposed restoration and management scenarios for the Loxahatchee River.

  7. Evidence of linked biogeochemical and hydrological processes in homogeneous and layered vadose zone systems

    NASA Astrophysics Data System (ADS)

    McGuire, J. T.; Hansen, D. J.; Mohanty, B. P.

    2010-12-01

    Understanding chemical fate and transport in the vadose zone is critical to protect groundwater resources and preserve ecosystem health. However, prediction can be challenging due to the dynamic hydrologic and biogeochemical nature of the vadose zone. Additional controls on hydrobiogeochemical processes are added by subsurface structural heterogeneity. This study uses repacked soil column experiments to quantify linkages between microbial activity, geochemical cycling and hydrologic flow. Three “short” laboratory soil columns were constructed to evaluate the effects of soil layering: a homogenized medium-grained sand, homogenized organic-rich loam, and a sand-over-loam layered column. In addition, two “long” columns were constructed using either gamma-irradiated (sterilized) or untreated sediments to evaluate the effects of both soil layers and the presence of microorganisms. The long columns were packed identically; a medium-grained sand matrix with two vertically separated and horizontally offset lenses of organic-rich loam. In all 5 columns, downward and upward infiltration of water was evaluated to simulate rainfall and rising water table events respectively. In-situ colocated probes were used to measure soil water content, matric potential, Eh, major anions, ammonium, Fe2+, and total sulfide. Enhanced biogeochemical cycling was observed in the short layered column versus the short, homogeneous columns, and enumerations of iron and sulfate reducing bacteria were 1-2 orders of magnitude greater. In the long columns, microbial activity caused mineral bands and produced insoluble gases that impeded water flow through the pores of the sediment. Capillary barriers, formed around the lenses due to soil textural differences, retarded water flow rates through the lenses. This allowed reducing conditions to develop, evidenced by the production of Fe2+ and S2-. At the fringes of the lenses, Fe2+ oxidized to form Fe(III)-oxide bands that further retarded water

  8. Continuous monitoring of water flow and solute transport using vadose zone monitoring technology

    NASA Astrophysics Data System (ADS)

    Dahan, O.

    2009-04-01

    Groundwater contamination is usually attributed to pollution events that initiate on land surface. These may be related to various sources such as industrial, urban or agricultural, and may appear as point or non point sources, through a single accidental event or a continuous pollution process. In all cases, groundwater pollution is a consequence of pollutant transport processes that take place in the vadose zone above the water table. Attempts to control pollution events and prevent groundwater contamination usually involve groundwater monitoring programs. This, however, can not provide any protection against contamination since pollution identification in groundwater is clear evidence that the groundwater is already polluted and contaminants have already traversed the entire vadose zone. Accordingly, an efficient monitoring program that aims at providing information that may prevent groundwater pollution has to include vadose-zone monitoring systems. Such system should provide real-time information on the hydrological and chemical properties of the percolating water and serve as an early warning system capable of detecting pollution events in their early stages before arrival of contaminants to groundwater. Recently, a vadose-zone monitoring system (VMS) was developed to allow continuous monitoring of the hydrological and chemical properties of percolating water in the deep vadose zone. The VMS includes flexible time-domain reflectometry (FTDR) probes for continuous tracking of water content profiles, and vadose-zone sampling ports (VSPs) for frequent sampling of the deep vadose pore water at multiple depths. The monitoring probes and sampling ports are installed through uncased slanted boreholes using a flexible sleeve that allows attachment of the monitoring devices to the borehole walls while achieving good contact between the sensors and the undisturbed sediment column. The system has been successfully implemented in several studies on water flow and

  9. Limited hydrologic response to Pleistocene climate change in deep vadose zones - Yucca Mountain, Nevada

    USGS Publications Warehouse

    Paces, J.B.; Neymark, L.A.; Whelan, J.F.; Wooden, J.L.; Lund, S.P.; Marshall, B.D.

    2010-01-01

    Understanding the movement of water through thick vadose zones, especially on time scales encompassing long-term climate change, is increasingly important as societies utilize semi-arid environments for both water resources and sites viewed as favorable for long-term disposal or storage of hazardous waste. Hydrologic responses to Pleistocene climate change within a deep vadose zone in the eastern Mojave Desert at Yucca Mountain, Nevada, were evaluated by uranium-series dating of finely layered hyalitic opal using secondary ion mass spectrometry. Opal is present within cm-thick secondary hydrogenic mineral crusts coating floors of lithophysal cavities in fractured volcanic rocks at depths of 200 to 300 m below land surface. Uranium concentrations in opal fluctuate systematically between 5 and 550 μg/g. Age-calibrated profiles of uranium concentration correlate with regional climate records over the last 300,000 years and produce time-series spectral peaks that have distinct periodicities of 100- and 41-ka, consistent with planetary orbital parameters. These results indicate that the chemical compositions of percolating solutions varied in response to near-surface, climate-driven processes. However, slow (micrometers per thousand years), relatively uniform growth rates of secondary opal and calcite deposition spanning several glacial–interglacial climate cycles imply that water fluxes in the deep vadose zone remained low and generally buffered from the large fluctuations in available surface moisture during different climates.

  10. Vadose zone microbiology

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kieft, Thomas L.; Brockman, Fred J.

    2001-01-17

    The vadose zone is defined as the portion of the terrestrial subsurface that extends from the land surface downward to the water table. As such, it comprises the surface soil (the rooting zone), the underlying subsoil, and the capillary fringe that directly overlies the water table. The unsaturated zone between the rooting zone and the capillary fringe is termed the "intermediate zone" (Chapelle, 1993). The vadose zone has also been defined as the unsaturated zone, since the sediment pores and/or rock fractures are generally not completely water filled, but instead contain both water and air. The latter characteristic results inmore » the term "zone of aeration" to describe the vadose zone. The terms "vadose zone," "unsaturated zone", and "zone of aeration" are nearly synonymous, except that the vadose zone may contain regions of perched water that are actually saturated. The term "subsoil" has also been used for studies of shallow areas of the subsurface immediately below the rooting zone. This review focuses almost exclusively on the unsaturated region beneath the soil layer since there is already an extensive body of literature on surface soil microbial communities and process, e.g., Paul and Clark (1989), Metting (1993), Richter and Markowitz, (1995), and Sylvia et al. (1998); whereas the deeper strata of the unsaturated zone have only recently come under scrutiny for their microbiological properties.« less

  11. Tracing long-term vadose zone processes at the Nevada Test Site, USA

    PubMed Central

    Hunt, James R.; Tompson, Andrew F. B.

    2010-01-01

    The nuclear weapons testing programme of the USA has released radionuclides to the subsurface at the Nevada Test Site. One of these tests has been used to study the hydrological transport of radionuclides for over 25 years in groundwater and the deep unsaturated zone. Ten years after the weapon’s test, a 16 year groundwater pumping experiment was initiated to study the mobility of radionuclides from that test in an alluvial aquifer. The continuously pumped groundwater was released into an unlined ditch where some of the water infiltrated into the 200 m deep vadose zone. The pumped groundwater had well-characterized tritium activities that were utilized to trace water migration in the shallow and deep vadose zones. Within the near-surface vadose zone, tritium levels in the soil water are modelled by a simple one-dimensional, analytical wetting front model. In the case of the near-surface soils at the Cambric Ditch experimental site, water flow and salt accumulation appear to be dominated by rooted vegetation, a mechanism not included within the wetting front model. Simulation results from a two-dimensional vadose groundwater flow model illustrate the dominance of vertical flow in the vadose zone and the recharge of the aquifer with the pumped groundwater. The long-time series of hydrological data provides opportunities to understand contaminant transport processes better in the vadose zone with an appropriate level of modelling. PMID:21785525

  12. Idaho National Laboratory Vadose Zone Research Park Geohydrological Monitoring Results

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kristine Baker

    2006-01-01

    Vadose zone lithology, hydrological characterization of interbed sediments, and hydrological data from subsurface monitoring of Idaho Nuclear Technology and Engineering Center wastewater infiltration are presented. Three-dimensional subsurface lithology of the vadose zone beneath the Vadose Zone Research Park is represented in a 2 dimensional (2 D) diagram showing interpolated lithology between monitoring wells. Laboratory-measured values for saturated hydraulic conductivity and porosity are given for three major interbeds, denoted as the B BC interbed (20 to 35 m bls), the C D interbed (40 to 45 m bls), and the DE 1 2 interbed (55 to 65 m bls), along withmore » an overall physical description of the sediments and geologic depositional environments. Pre-operational pore water pressure conditions are presented to show the presence and location of perched water zones before pond discharge at the New Percolation Ponds. Subsurface infiltration conditions during initial high-volume discharge are presented to show water arrival times and arrival sequences. Steady-state conditions are then presented to show formation and locations of perched water zones and recharge sources after several months of discharge to the New Percolation Ponds.« less

  13. Karst system vadose zone hydrodynamics highlighted by an integrative geophysical and hydrogeological monitoring

    NASA Astrophysics Data System (ADS)

    Watlet, A.; Van Camp, M. J.; Francis, O.; Poulain, A.; Hallet, V.; Rochez, G.; Kaufmann, O.

    2015-12-01

    The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of climate conditions, diminished evapotranspiration and differences of porosity relative to deeper layers. It is therefore crucial, but challenging, to separate the hydrological signature of the vadose zone from the one of the saturated zone for understanding hydrological processes that occur in the vadose zone. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside with various techniques. We present results covering two years of hydrogeological and geophysical monitoring at the Rochefort Cave Laboratory (RCL), located in the Variscan fold-and-thrust belt (Belgium), a region that shows many karstic networks within Devonian limestone units. Hydrogeological data such as flows and levels monitoring or tracer tests performed in both vadose and saturated zones bring valuable information on the hydrological context of the studied area. Combining those results with geophysical measurements allows validating and imaging them with more integrative techniques. A microgravimetric monitoring involves a superconducting gravimeter continuously measuring at the surface of the RCL. Early in 2015, a second relative gravimeter was installed in the underlying cave system located 35 meters below the surface. This set up allows highlighting vadose gravity changes. These relative measurements are calibrated using an absolute gravimeter. 12 additional stations (7 at the surface, 5 in the cave) are monitored on a monthly basis by a spring gravimeter. To complete these gravimetric measurements, the site has been equipped with a permanent Electrical Resistivity Tomography (ERT) monitoring system comprising an uncommon array of surface, borehole and cave electrodes. Although such

  14. Multi-scale hydrogeological and hydrogeophysical approach to monitor vadose zone hydrodynamics of a karst system

    NASA Astrophysics Data System (ADS)

    Watlet, Arnaud; Poulain, Amaël; Van Camp, Michel; Francis, Olivier; Triantafyllou, Antoine; Rochez, Gaëtan; Hallet, Vincent; Kaufmann, Olivier

    2016-04-01

    The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of weather conditions, reduced evapotranspiration and the vertical gradients of porosity and permeability. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside. We present a multi-scale study covering two years of hydrogeological and geophysical monitoring of the Lomme Karst System (LKS) located in the Variscan fold-and-thrust belt (Belgium), a region (~ 3000 ha) that shows many karstic networks within Devonian limestone units. Hydrogeological data cover the whole LKS and involve e.g. flows and levels monitoring or tracer tests performed in both vadose and saturated zones. Such data bring valuable information on the hydrological context of the studied area at the catchment scale. Combining those results with geophysical measurements allows validating and imaging them at a smaller scale, with more integrative techniques. Hydrogeophysical measurements are focused on only one cave system of the LKS, at the Rochefort site (~ 40 ha), taking benefit of the Rochefort Cave Laboratory (RCL) infrastructures. In this study, a microgravimetric monitoring and an Electrical Resistivity Tomography (ERT) monitoring are involved. The microgravimetric monitoring consists in a superconducting gravimeter continuously measuring gravity changes at the surface of the RCL and an additional relative gravimeter installed in the underlying cave located 35 meters below the surface. While gravimeters are sensible to changes that occur in both the vadose zone and the saturated zone of the whole cave system, combining their recorded signals allows enhancing vadose zone's gravity changes. Finally, the surface ERT monitoring provide valuable information at the (sub)-meter scale on the

  15. Which key properties controls the preferential transport in the vadose zone under transient hydrological conditions

    NASA Astrophysics Data System (ADS)

    Groh, J.; Vanderborght, J.; Puetz, T.; Gerke, H. H.; Rupp, H.; Wollschlaeger, U.; Stumpp, C.; Priesack, E.; Vereecken, H.

    2015-12-01

    Understanding water flow and solute transport in the unsaturated zone is of great importance for an appropriate land use management strategy. The quantification and prediction of water and solute fluxes through the vadose zone can help to improve management practices in order to limit potential risk on our fresh water resources. Water related solute transport and residence time is strongly affected by preferential flow paths in the soil. Water flow in soils depends on soil properties and site factors (climate or experiment conditions, land use) and are therefore important factors to understand preferential solute transport in the unsaturated zone. However our understanding and knowledge of which on-site properties or conditions define and enhance preferential flow and transport is still poor and mostly limited onto laboratory experimental conditions (small column length and steady state boundary conditions). Within the TERENO SOILCan lysimeter network, which was designed to study the effects of climate change on soil functions, a bromide tracer was applied on 62 lysimeter at eight different test sites between Dec. 2013 and Jan. 2014. The TERENO SOILCan infrastructure offers the unique possibility to study the occurrence of preferential flow and transport of various soil types under different natural transient hydrological conditions and land use (crop, bare and grassland) at eight TERENO SOILCan observatories. Working with lysimeter replicates at each observatory allows defining the spatial variability of preferential transport and flow. Additionally lysimeters in the network were transferred within and between observatories in order to subject them to different rainfall and temperature regimes and enable us to relate the soil type susceptibility of preferential flow and transport not only to site specific physical and land use properties, but also to different transient boundary conditions. Comparison and statistical analysis between preferential flow indicators 5

  16. Vadose Zone Monitoring as a Key to Groundwater Protection from Pollution Hazard

    NASA Astrophysics Data System (ADS)

    Dahan, Ofer

    2016-04-01

    Minimization subsurface pollution is much dependent on the capability to provide real-time information on the chemical and hydrological properties of the percolating water. Today, most monitoring programs are based on observation wells that enable data acquisitions from the saturated part of the subsurface. Unfortunately, identification of pollutants in well water is clear evidence that the contaminants already crossed the entire vadose-zone and accumulated in the aquifer water to detectable concentration. Therefore, effective monitoring programs that aim at protecting groundwater from pollution hazard should include vadose zone monitoring technologies that are capable to provide real-time information on the chemical composition of the percolating water. Obviously, identification of pollution process in the vadose zone may provide an early warning on potential risk to groundwater quality, long before contaminates reach the water-table and accumulate in the aquifers. Since productive agriculture must inherently include down leaching of excess lower quality water, understanding the mechanisms controlling transport and degradation of pollutants in the unsaturated is crucial for water resources management. A vadose-zone monitoring system (VMS), which was specially developed to enable continuous measurements of the hydrological and chemical properties of percolating water, was used to assess the impact of various agricultural setups on groundwater quality, including: (a) intensive organic and conventional greenhouses, (b) citrus orchard and open field crops , and (c) dairy farms. In these applications frequent sampling of vadose zone water for chemical and isotopic analysis along with continuous measurement of water content was used to assess the link between agricultural setups and groundwater pollution potential. Transient data on variation in water content along with solute breakthrough at multiple depths were used to calibrate flow and transport models. These models

  17. Vadose zone studies at an industrial contaminated site: the vadose zone monitoring system and cross-hole geophysics

    NASA Astrophysics Data System (ADS)

    Fernandez de Vera, Natalia; Beaujean, Jean; Jamin, Pierre; Nguyen, Frédéric; Dahan, Ofer; Vanclooster, Marnik; Brouyère, Serge

    2014-05-01

    In order to improve risk characterization and remediation measures for soil and groundwater contamination, there is a need to improve in situ vadose zone characterization. However, most available technologies have been developed in the context of agricultural soils. Such methodologies are not applicable at industrial sites, where soils and contamination differ in origin and composition. In addition, most technologies are applicable only in the first meters of soils, leaving deeper vadose zones with lack of information, in particular on field scale heterogeneity. In order to overcome such difficulties, a vadose zone experiment has been setup at a former industrial site in Belgium. Industrial activities carried out on site left a legacy of soil and groundwater contamination in BTEX, PAH, cyanide and heavy metals. The experiment comprises the combination of two techniques: the Vadose Zone Monitoring System (VMS) and cross-hole geophysics. The VMS allows continuous measurements of water content and temperature at different depths of the vadose zone. In addition, it provides the possibility of pore water sampling at different depths. The system is formed by a flexible sleeve containing monitoring units along its depth which is installed in a slanted borehole. The flexible sleeve contains three types of monitoring units in the vadose zone: Time Domain Transmissometry (TDT), which allows water content measurements; Vadose Sampling Ports (VSP), used for collecting water samples coming from the matrix; the Fracture Samplers (FS), which are used for retrieving water samples from the fractures. Cross-hole geophysics techniques consist in the injection of an electrical current using electrodes installed in vertical boreholes. From measured potential differences, detailed spatial patterns about electrical properties of the subsurface can be inferred. Such spatial patterns are related with subsurface heterogeneities, water content and solute concentrations. Two VMS were

  18. Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring

    NASA Astrophysics Data System (ADS)

    Watlet, Arnaud; Kaufmann, Olivier; Triantafyllou, Antoine; Poulain, Amaël; Chambers, Jonathan E.; Meldrum, Philip I.; Wilkinson, Paul B.; Hallet, Vincent; Quinif, Yves; Van Ruymbeke, Michel; Van Camp, Michel

    2018-03-01

    Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. In particular, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of 3 years at the Rochefort Cave Laboratory (RCL) site in south Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography (ERT) monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring and summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; and (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip

  19. Vadose zone transport field study: Detailed test plan for simulated leak tests

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    AL Ward; GW Gee

    2000-06-23

    The US Department of Energy (DOE) Groundwater/Vadose Zone Integration Project Science and Technology initiative was created in FY 1999 to reduce the uncertainty associated with vadose zone transport processes beneath waste sites at DOE's Hanford Site near Richland, Washington. This information is needed not only to evaluate the risks from transport, but also to support the adoption of measures for minimizing impacts to the groundwater and surrounding environment. The principal uncertainties in vadose zone transport are the current distribution of source contaminants and the natural heterogeneity of the soil in which the contaminants reside. Oversimplified conceptual models resulting from thesemore » uncertainties and limited use of hydrologic characterization and monitoring technologies have hampered the understanding contaminant migration through Hanford's vadose zone. Essential prerequisites for reducing vadose transport uncertainly include the development of accurate conceptual models and the development or adoption of monitoring techniques capable of delineating the current distributions of source contaminants and characterizing natural site heterogeneity. The Vadose Zone Transport Field Study (VZTFS) was conceived as part of the initiative to address the major uncertainties confronting vadose zone fate and transport predictions at the Hanford Site and to overcome the limitations of previous characterization attempts. Pacific Northwest National Laboratory (PNNL) is managing the VZTFS for DOE. The VZTFS will conduct field investigations that will improve the understanding of field-scale transport and lead to the development or identification of efficient and cost-effective characterization methods. Ideally, these methods will capture the extent of contaminant plumes using existing infrastructure (i.e., more than 1,300 steel-cased boreholes). The objectives of the VZTFS are to conduct controlled transport experiments at well-instrumented field sites at Hanford

  20. Borehole Time Domain Reflectometry in Layered Sandstone: Impact of Measurement Technique on Vadose Zone Process Identification

    NASA Astrophysics Data System (ADS)

    West, J.; Truss, S. W.

    2004-12-01

    An investigation is reported into the hydraulic behaviour of the vadose zone of a layered sandstone aquifer using borehole-based Time Domain Reflectometry (TDR). TDR has been widely applied to shallow soils but has seen limited application at greater depth and in cemented lithologies due to the difficulty of installing conventional TDR probes in rock and from boreholes. Here, flat TDR probes that are simply in contact with, rather than inserted within the medium under investigation, have been developed and applied in a field study. Both a commercially available portable packer TDR system (TRIME-B3L Borehole Packer Probe) and specially designed TDR probes, permanently installed in boreholes on grouted-in packers were used to monitor seasonal fluctuations in moisture content in the vadose zone of a layered sandstone over one year under natural rainfall loading. The data show that the vadose zone contains seasonal perched water tables that form when downward percolating moisture reaches layers of fine grained sandstone and siltstone and causes local saturation. The formation of perched water tables is likely to lead to lateral flow bypassing the less permeable, finer layers. This contrasts with behaviour inferred from previous studies of the same aquifer that used borehole radar and resistivity, which suggested its vadose zone behaviour was characterized by uniform downwards migration of wetting fronts. To investigate the impact of measurement technique on observed response, the TDR data reported here were used to produce simulated zero offset profile (ZOP) borehole radar responses. This simulation confirmed the limited ability of ZOP borehole radar to detect key vadose zone processes, because the phenomenon of critical refraction minimizes the sensitivity of the results to high moisture content layers. The study illustrates that inappropriate technique selection results in hydrological process mis-identification, with serious consequences for the usefulness of data

  1. Sensitivity of Vadose Zone Water Fluxes to Climate Shifts in Arid Settings

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pfletschinger, H.; Prömmel, K.; Schüth, C.

    2014-01-01

    Vadose zone water fluxes in arid settings are investigated regarding their sensitivity to hydraulic soil parameters and meteorological data. The study is based on the inverse modeling of highly defined soil column experiments and subsequent scenario modeling comparing different climate projections for a defined arid region. In arid regions, groundwater resources are prone to depletion due to excessive water use and little recharge potential. Especially in sand dune areas, groundwater recharge is highly dependent on vadose zone properties and corresponding water fluxes. Nevertheless, vadose zone water fluxes under arid conditions are hard to determine owing to, among other reasons, deepmore » vadose zones with generally low fluxes and only sporadic high infiltration events. In this study, we present an inverse model of infiltration experiments accounting for variable saturated nonisothermal water fluxes to estimate effective hydraulic and thermal parameters of dune sands. A subsequent scenario modeling links the results of the inverse model with projections of a global climate model until 2100. The scenario modeling clearly showed the high dependency of groundwater recharge on precipitation amounts and intensities, whereas temperature increases are only of minor importance for deep infiltration. However, simulated precipitation rates are still affected by high uncertainties in the response to the hydrological input data of the climate model. Thus, higher certainty in the prediction of precipitation pattern is a major future goal for climate modeling to constrain future groundwater management strategies in arid regions.« less

  2. Vadose Zone Transport Field Study: Status Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gee, Glendon W.; Ward, Anderson L.

    2001-11-30

    Studies were initiated at the Hanford Site to evaluate the process controlling the transport of fluids in the vadose zone and to develop a reliable database upon which vadose-zone transport models can be calibrated. These models are needed to evaluate contaminant migration through the vadose zone to underlying groundwaters at Hanford. A study site that had previously been extensively characterized using geophysical monitoring techniques was selected in the 200 E Area. Techniques used previously included neutron probe for water content, spectral gamma logging for radionuclide tracers, and gamma scattering for wet bulk density. Building on the characterization efforts of themore » past 20 years, the site was instrumented to facilitate the comparison of nine vadose-zone characterization methods: advanced tensiometers, neutron probe, electrical resistance tomography (ERT), high-resolution resistivity (HRR), electromagnetic induction imaging (EMI), cross-borehole radar (XBR), and cross-borehole seismic (XBS). Soil coring was used to obtain soil samples for analyzing ionic and isotopic tracers.« less

  3. Vadose zone water fluxmeter

    DOEpatents

    Faybishenko, Boris A.

    2005-10-25

    A Vadose Zone Water Fluxmeter (WFM) or Direct Measurement WFM provides direct measurement of unsaturated water flow in the vadose zone. The fluxmeter is a cylindrical device that fits in a borehole or can be installed near the surface, or in pits, or in pile structures. The fluxmeter is primarily a combination of tensiometers and a porous element or plate in a water cell that is used for water injection or extraction under field conditions. The same water pressure measured outside and inside of the soil sheltered by the lower cylinder of the fluxmeter indicates that the water flux through the lower cylinder is similar to the water flux in the surrounding soil. The fluxmeter provides direct measurement of the water flow rate in the unsaturated soils and then determines the water flux, i.e. the water flow rate per unit area.

  4. Vadose Zone Transport Field Study: Summary Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ward, Andy L.; Conrad, Mark E.; Daily, William D.

    2006-07-31

    From FY 2000 through FY 2003, a series of vadose zone transport field experiments were conducted as part of the U.S. Department of Energy’s Groundwater/Vadose Zone Integration Project Science and Technology Project, now known as the Remediation and Closure Science Project, and managed by the Pacific Northwest National Laboratory (PNNL). The series of experiments included two major field campaigns, one at a 299-E24-11 injection test site near PUREX and a second at a clastic dike site off Army Loop Road. The goals of these experiments were to improve our understanding of vadose zone transport processes; to develop data sets tomore » validate and calibrate vadose zone flow and transport models; and to identify advanced monitoring techniques useful for evaluating flow-and-transport mechanisms and delineating contaminant plumes in the vadose zone at the Hanford Site. This report summarizes the key findings from the field studies and demonstrates how data collected from these studies are being used to improve conceptual models and develop numerical models of flow and transport in Hanford’s vadose zone. Results of these tests have led to a better understanding of the vadose zone. Fine-scale geologic heterogeneities, including grain fabric and lamination, were observed to have a strong effect on the large-scale behavior of contaminant plumes, primarily through increased lateral spreading resulting from anisotropy. Conceptual models have been updated to include lateral spreading and numerical models of unsaturated flow and transport have revised accordingly. A new robust model based on the concept of a connectivity tensor was developed to describe saturation-dependent anisotropy in strongly heterogeneous soils and has been incorporated into PNNL’s Subsurface Transport Over Multiple Phases (STOMP) simulator. Application to field-scale transport problems have led to a better understanding plume behavior at a number of sites where lateral spreading may have dominated

  5. Global Patterns of Legacy Nitrate Storage in the Vadose Zone

    NASA Astrophysics Data System (ADS)

    Ascott, M.; Gooddy, D.; Wang, L.; Stuart, M.; Lewis, M.; Ward, R.; Binley, A. M.

    2017-12-01

    Global-scale nitrogen (N) budgets have been developed to quantify the impact of man's influence on the nitrogen cycle. However, these budgets often do not consider legacy effects such as accumulation of nitrate in the deep vadose zone. In this presentation we show that the vadose zone is an important store of nitrate which should be considered in future nitrogen budgets for effective policymaking. Using estimates of depth to groundwater and nitrate leaching for 1900-2000, we quantify for the first time the peak global storage of nitrate in the vadose zone, estimated as 605 - 1814 Teragrams (Tg). Estimates of nitrate storage are validated using previous national and basin scale estimates of N storage and observed groundwater nitrate data for North America and Europe. Nitrate accumulation per unit area is greatest in North America, China and Central and Eastern Europe where thick vadose zones are present and there is an extensive history of agriculture. In these areas the long solute travel time in the vadose zone means that the anticipated impact of changes in agricultural practices on groundwater quality may be substantially delayed. We argue that in these areas use of conventional nitrogen budget approaches is inappropriate and their continued use will lead to significant errors.

  6. Effects of remediation amendments on vadose zone microorganisms

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Miller, Hannah M.; Tilton, Fred A.

    2012-08-10

    Surfactant-based foam delivery technology has been studied to remediate Hanford 200 area deep vadose zone sediment. However, the surfactants and remediation amendments have an unknown effect on indigenous subsurface microorganisms. Microbial populations are important factors to consider in remediation efforts due to their potential to alter soil geochemistry. This project focuses on measuring microbial metabolic responses to remediation amendments in batch and column studies using Deep Vadose Zone Sediments. Initial studies of the microbes from Hanford 200 area deep vadose zone sediment showed surfactants sodium dodecyl sulfate (SDS) and cocamidopropyl betaine (CAPB) and remediation amendment calcium polysulfide (CPS) had nomore » affect on microbial growth using BiologTM Ecoplates. To move towards a more realistic field analog, soil columns were packed with Hanford 200 Area sediment. Once microbial growth in the column was verified by observing growth of the effluent solution on tryptic soy agar plates, remedial surfactants were injected into the columns, and the resulting metabolic diversity was measured. Results suggest surfactant sodium dodecyl sulfate (SDS) stimulates microbial growth. The soil columns were also visualized using X-ray microtomography to inspect soil packing and possibly probe for evidence of biofilms. Overall, BiologTM Ecoplates provide a rapid assay to predict effects of remediation amendments on Hanford 200 area deep vadose zone microorganisms.« less

  7. Vadose zone process that control landslide initiation and debris flow propagation

    NASA Astrophysics Data System (ADS)

    Sidle, Roy C.

    2015-04-01

    Advances in the areas of geotechnical engineering, hydrology, mineralogy, geomorphology, geology, and biology have individually advanced our understanding of factors affecting slope stability; however, the interactions among these processes and attributes as they affect the initiation and propagation of landslides and debris flows are not well understood. Here the importance of interactive vadose zone processes is emphasized related to the mechanisms, initiation, mode, and timing of rainfall-initiated landslides that are triggered by positive pore water accretion, loss of soil suction and increase in overburden weight, and long-term cumulative rain water infiltration. Both large- and small-scale preferential flow pathways can both contribute to and mitigate instability, by respectively concentrating and dispersing subsurface flow. These mechanisms are influenced by soil structure, lithology, landforms, and biota. Conditions conducive to landslide initiation by infiltration versus exfiltration are discussed relative to bedrock structure and joints. The effects of rhizosphere processes on slope stability are examined, including root reinforcement of soil mantles, evapotranspiration, and how root structures affect preferential flow paths. At a larger scale, the nexus between hillslope landslides and in-channel debris flows is examined with emphasis on understanding the timing of debris flows relative to chronic and episodic infilling processes, as well as the episodic nature of large rainfall and related stormflow generation in headwater streams. The hydrogeomorphic processes and conditions that determine whether or not landslides immediately mobilize into debris flows is important for predicting the timing and extent of devastating debris flow runout in steep terrain. Given the spatial footprint of individual landslides, it is necessary to assess vadose zone processes at appropriate scales to ascertain impacts on mass wasting phenomena. Articulating the appropriate

  8. Model Package Report: Central Plateau Vadose Zone Geoframework Version 1.0

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Springer, Sarah D.

    The purpose of the Central Plateau Vadose Zone (CPVZ) Geoframework model (GFM) is to provide a reasonable, consistent, and defensible three-dimensional (3D) representation of the vadose zone beneath the Central Plateau at the Hanford Site to support the Composite Analysis (CA) vadose zone contaminant fate and transport models. The GFM is a 3D representation of the subsurface geologic structure. From this 3D geologic model, exported results in the form of point, surface, and/or volumes are used as inputs to populate and assemble the various numerical model architectures, providing a 3D-layered grid that is consistent with the GFM. The objective ofmore » this report is to define the process used to produce a hydrostratigraphic model for the vadose zone beneath the Hanford Site Central Plateau and the corresponding CA domain.« less

  9. Identification of dominating factors affecting vadose zone vulnerability by a simulation method

    PubMed Central

    Li, Juan; Xi, Beidou; Cai, Wutian; Yang, Yang; Jia, Yongfeng; Li, Xiang; Lv, Yonggao; Lv, Ningqing; Huan, Huan; Yang, Jinjin

    2017-01-01

    The characteristics of vadose zone vulnerability dominating factors (VDFs) are closely related to the migration and transformation mechanisms of contaminants in the vadose zone, which directly affect the state of the contaminants percolating to the groundwater. This study analyzes the hydrogeological profile of the pore water regions in the vadose zone, and conceptualizes the vadose zone as single lithologic, double lithologic, or multi lithologic. To accurately determine how the location of the pollution source influences the groundwater, we classify the permeabilities (thicknesses) of different media into clay-layer and non-clay-layer permeabilities (thicknesses), and introduce the maximum pollution thickness. Meanwhile, the physicochemical reactions of the contaminants in the vadose zone are represented by the soil adsorption and soil degradability. The VDFs are determined from the factors and parameters in groundwater vulnerability assessment. The VDFs are identified and sequenced in simulations and a sensitivity analysis. When applied to three polluted sites in China, the method improved the weighting of factors in groundwater vulnerability assessment, and increased the reliability of predicting groundwater vulnerability to contaminants. PMID:28387232

  10. Surface and subsurface continuous gravimetric monitoring of groundwater recharge processes through the karst vadose zone at Rochefort Cave (Belgium)

    NASA Astrophysics Data System (ADS)

    Watlet, A.; Van Camp, M. J.; Francis, O.; Poulain, A.; Hallet, V.; Triantafyllou, A.; Delforge, D.; Quinif, Y.; Van Ruymbeke, M.; Kaufmann, O.

    2017-12-01

    Ground-based gravimetry is a non-invasive and integrated tool to characterize hydrological processes in complex environments such as karsts or volcanoes. A problem in ground-based gravity measurements however concerns the lack of sensitivity in the first meters below the topographical surface, added to limited infiltration below the gravimeter building (umbrella effect). Such limitations disappear when measuring underground. Coupling surface and subsurface gravity measurements therefore allow isolating hydrological signals occurring in the zone between the two gravimeters. We present a coupled surface/subsurface continuous gravimetric monitoring of 2 years at the Rochefort Cave Laboratory (Belgium). The gravity record includes surface measurements of a GWR superconducting gravimeter and subsurface measurements of a Micro-g LaCoste gPhone gravimeter, installed in a cave 35 m below the surface station. The recharge of karstic aquifers is extremely complex to model, mostly because karst hydrological systems are composed of strongly heterogeneous flows. Most of the problem comes from the inadequacy of conventional measuring tools to correctly sample such heterogeneous media, and particularly the existence of a duality of flow types infiltrating the vadose zone: from rapid flows via open conduits to slow seepage through porous matrix. Using the surface/subsurface gravity difference, we were able to identify a significant seasonal groundwater recharge within the karst vadose zone. Seasonal or perennial perched reservoirs have already been proven to exist in several karst areas due to the heterogeneity of the porosity and permeability gradient in karstified carbonated rocks. Our gravimetric experiment allows assessing more precisely the recharge processes of such reservoirs. The gravity variations were also compared with surface and in-cave hydrogeological monitoring (i.e. soil moisture, in-cave percolating water discharges, water levels of the saturated zone). Combined

  11. Bioremediation of RDX in the vadose zone beneath the Pantex Plant

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shull, T.L.; Speitel, G.E. Jr.; McKinney, D.C.

    1999-01-01

    The presence of dissolved high explosives (HE), in particular RDX and HMX, is well documented in the perched aquifer beneath the Pantex Plant, but the distribution of HE in the vadose zone has not yet been well defined. Although current remediation activities focus on the contamination in the perched aquifer, eventually regulatory concern is likely to turn to the residual contamination in the vadose zone. Sources of HE include the infiltration of past wastewater discharges from several HE-processing facilities through the ditch drainage system and leachate from former Landfill 3. With limited existing data on the HE distribution in themore » vadose zone and without preventive action, it must be assumed that residual HE could be leached into infiltrating water, providing a continuing supply of contamination to the perched aquifer. The purpose of this project was to more closely examine the fate and transport of HE in the vadose zone through mathematical modeling and laboratory experimentation. In particular, this report focuses on biodegradation as one possible fate of HE. Biodegradation of RDX in the vadose zone was studied because it is both present in highest concentration and is likely to be of the greatest regulatory concern. This study had several objectives: determine if indigenous soil organisms are capable of RDX biodegradation; determine the impact of electron acceptor availability and nutrient addition on RDX biodegradation; determine the extent of RDX mineralization (i.e., conversion to inorganic carbon) during biodegradation; and estimate the kinetics of RDX biodegradation to provide information for mathematical modeling of fate and transport.« less

  12. Deep Vadose Zone Treatability Test of Soil Desiccation for the Hanford Central Plateau: Final Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Chronister, Glen B.; Strickland, Christopher E.

    Some of the inorganic and radionuclide contaminants in the deep vadose zone at the Hanford Site are at depths where direct exposure pathways are not of concern, but may need to be remediated to protect groundwater. The Department of Energy developed a treatability test program for technologies to address Tc-99 and uranium in the deep vadose zone. These contaminants are mobile in the subsurface environment, have been detected at high concentrations deep in the vadose zone, and at some locations have reached groundwater. The treatability test of desiccation described herein was conducted as an element of the deep vadose zonemore » treatability test program. Desiccation was shown to be a potentially effective vadose zone remediation technology to protect groundwater when used in conjunction with a surface infiltration barrier.« less

  13. EVALUATION OF VADOSE ZONE TREATMENT TECHNOLOGIES TO IMMOBILIZE TECHNETIUM-99

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    PETERSEN, S.W.

    2006-03-15

    The Hanford Site End State Vision document (DOE/RL-2003-59) states: ''There should be an aggressive plan to develop technology for remediation of the contamination that could get to the groundwater (particularly the technetium [{sup 99}Tc])''. In addition, there is strong support from the public and regulatory agencies for the above statement, with emphasis on investigation of treatment alternatives. In July 2004, PNNL completed a preliminary evaluation of remediation technologies with respect to their effectiveness and implementability for immobilization of {sup 99}Tc beneath the BC Cribs in the 200 West Area (Truex, 2004). As a result of this evaluation, PNNL recommended treatabilitymore » testing of in situ soil desiccation, because it has the least uncertainty of those technologies evaluated in July 2004 (Treatability Test Outline, September 30, 2004). In 2005, DOE-RL and Fluor Hanford convened an independent technical panel to review alternative remediation technologies, including desiccation, at a three-day workshop in Richland, Washington. The panel was composed of experts in vadose-zone transport, infiltration control, hydrology, geochemistry, environmental engineering, and geology. Their backgrounds include employment in academia, government laboratories, industry, and consulting. Their review, presented in this document, is based upon written reports from Hanford, oral presentations from Hanford staff, and each panel members' years of experience in their particular field of expertise. The purpose of this report is to document the panel's evaluation of various treatment alternatives with potential for minimizing contaminant migration in the deep vadose zone at the Department of Energy Hanford Site. The panel was tasked with assessing the most viable and practical approach and making recommendations for testing. The evaluation of vadose-zone treatment alternatives was conducted to be broadly applicable at a variety of locations at Hanford. However

  14. E-Area Low-Level Waste Facility Vadose Zone Model: Confirmation of Water Mass Balance for Subsidence Scenarios

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dyer, J. A.

    In preparation for the next revision of the E-Area Low-Level Waste Facility (LLWF) Performance Assessment (PA), a mass balance model was developed in Microsoft Excel to confirm correct implementation of intact- and subsided-area infiltration profiles for the proposed closure cap in the PORFLOW vadose-zone model. The infiltration profiles are based on the results of Hydrologic Evaluation of Landfill Performance (HELP) model simulations for both intact and subsided cases.

  15. Climate variability and vadose zone controls on damping of transient recharge

    USGS Publications Warehouse

    Corona, Claudia R.; Gurdak, Jason J.; Dickinson, Jesse; Ferré, T.P.A.; Maurer, Edwin P.

    2018-01-01

    Increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve. Here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global-scale climate variability and fluctuations in groundwater levels. We use hundreds of HYDRUS-1D simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous United States (U.S). Although the models were parameterized based on U.S. aquifers, findings from this study are applicable elsewhere that have mean recharge rates between 3.65 and 730 mm yr–1. We find that mean infiltration flux, period of time varying infiltration, and hydraulic conductivity are statistically significant predictors of damping depth. The resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone, resulting in steady-state recharge, while other periodic surface fluxes do not dampen with depth, resulting in transient recharge. We find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most U.S. aquifers. Our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations. The implications are that relatively simple, homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate-varying transient recharge in some complex, layered vadose zone profiles.

  16. HEAT AND MASS TRANSFER IN THE VADOSE ZONE WITH PLANT ROOTS. (R825414)

    EPA Science Inventory

    Abstract

    The vadose zone is the intermediate medium between the atmosphere and groundwater. The modeling of the processes taking place in the vadose zone needs different approaches to those needed for groundwater transport problems because of the marked changes in envi...

  17. SENSITIVE PARAMETER EVALUATION FOR A VADOSE ZONE FATE AND TRANSPORT MODEL

    EPA Science Inventory

    This report presents information pertaining to quantitative evaluation of the potential impact of selected parameters on output of vadose zone transport and fate models used to describe the behavior of hazardous chemicals in soil. The Vadose 2one Interactive Processes (VIP) model...

  18. Tackling the Challenge of Deep Vadose Zone Remediation at the Hanford Site

    NASA Astrophysics Data System (ADS)

    Morse, J. G.; Wellman, D. M.; Gephart, R.

    2010-12-01

    The Central Plateau of the Hanford Site in Washington State contains some 800 waste disposal sites where 1.7 trillion liters of contaminated water was once discharged into the subsurface. Most of these sites received liquids from the chemical reprocessing of spent uranium fuel to recover plutonium. In addition, 67 single shell tanks have leaked or are suspected to have leaked 3.8 million liters of high alkali and aluminate rich cesium-contaminated liquids into the sediment. Today, this inventory of subsurface contamination contains an estimated 550,000 curies of radioactivity and 150 million kg (165,000 tons) of metals and hazardous chemicals. Radionuclides range from mobile 99Tc to more immobilized 137Cs, 241Am, uranium, and plutonium. A significant fraction of these contaminants likely remain within the deep vadose zone. Plumes of groundwater containing tritium, nitrate, 129I and other contaminants have migrated through the vadose zone and now extend outward from the Central Plateau to the Columbia River. During most of Hanford Site history, subsurface studies focused on groundwater monitoring and characterization to support waste management decisions. Deep vadose zone studies were not a priority because waste practices relied upon that zone to buffer contaminant releases into the underlying aquifer. Remediation of the deep vadose zone is now central to Hanford Site cleanup because these sediments can provide an ongoing source of contamination to the aquifer and therefore to the Columbia River. However, characterization and remediation of the deep vadose zone pose some unique challenges. These include sediment thickness; contaminant depth; coupled geohydrologic, geochemical, and microbial processes controlling contaminant spread; limited availability and effectiveness of traditional characterization tools and cleanup remedies; and predicting contaminant behavior and remediation performance over long time periods and across molecular to field scales. The U

  19. Evaluation of deep vadose zone contaminant flux into groundwater: Approach and case study

    NASA Astrophysics Data System (ADS)

    Oostrom, M.; Truex, M. J.; Last, G. V.; Strickland, C. E.; Tartakovsky, G. D.

    2016-06-01

    For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a case study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into account a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone.

  20. Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Oostrom, Martinus; Truex, Michael J.; Last, George V.

    For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a casemore » study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into account a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone.« less

  1. The role of rock moisture on regulating hydrologic and solute fluxes in the critical zone

    NASA Astrophysics Data System (ADS)

    Rempe, D. M.; Druhan, J. L.; Hahm, W. J.; Wang, J.; Murphy, C.; Cargill, S.; Dietrich, W. E.; Tune, A. K.

    2017-12-01

    In environments where the vadose zone extends below the soil layer into underlying weathered bedrock, the water held in the weathering -generated pores can be an important source of moisture to vegetation. The heterogeneous distribution of pore space in weathered bedrock, furthermore, controls the subsurface water flowpaths that dictate how water is partitioned in the critical zone (CZ) and evolves geochemically. Here, we present the results of direct monitoring of the fluxes of water and solutes through the deep CZ using a novel vadose zone monitoring system (VMS) as well as geophysical logging and sampling in a network of deep wells across a steep hillslope in Northern California. At our study site (Eel River CZO), multi-year monitoring reveals that a significant fraction of incoming rainfall (up to 30%) is seasonally stored in the fractures and matrix of the upper 12 m of weathered bedrock as rock moisture. Intensive geochemical and geophysical observations distributed from the surface to the depth of unweathered bedrock indicate that the seasonal addition and depletion of rock moisture has key implications for hydrologic and geochemical processes. First, rock moisture storage provides an annually consistent water storage reservoir for use by vegetation during the summer, which buffers transpiration fluxes against variability in seasonal precipitation. Second, because the timing and magnitude of groundwater recharge and streamflow are controlled by the annual filling and drainage of the rock moisture, rock moisture regulates the partitioning of hydrologic fluxes. Third, we find that rock moisture dynamics—which influence the myriad geochemical and microbial processes that weather bedrock—strongly correspond with the observed vertical weathering profile. As a result of the coupling between chemical weathering reactions and hydrologic fluxes, the geochemical composition of groundwater and streamflow is influenced by the temporal dynamics of rock moisture. Our

  2. Evaluation of deep vadose zone contaminant flux into groundwater: Approach and case study.

    PubMed

    Oostrom, M; Truex, M J; Last, G V; Strickland, C E; Tartakovsky, G D

    2016-06-01

    For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a case study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into account a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Soil Flushing Through a Thick Vadose Zone: Perchlorate Removal Documented at Edwards AFB, California

    NASA Astrophysics Data System (ADS)

    Battey, T. F.; Shepard, A. J.; Tait, R. J.

    2007-12-01

    There are currently few viable alternatives for perchlorate remediation in the vadose zone, particularly for the relatively thick vadose zones that are typical in the arid southwest where many perchlorate sites occur. Perchlorate in the vadose zone occurs in the form of highly soluble salts that may represent a risk to human or ecological receptors, and may also represent a threat to the underlying groundwater. A soil flushing treatability study was conducted at Edwards Air Force Base in the Mojave Desert of southern California at a site with a 129-foot thick vadose zone consisting primarily of clayey sand. This study utilized an infiltration gallery in conjunction with extraction, treatment, and re-injection of groundwater at the site, which contained perchlorate-contaminated soil and groundwater. The study objective was to evaluate the effectiveness of the infiltration gallery to 1) introduce treated groundwater back into the aquifer and 2) wash the perchlorate from the vadose zone soils to the aquifer. The infiltration gallery consisted of slotted PVC pipes within a highly permeable engineered bed of washed gravel. The initial water introduced into the gallery was amended with potassium bromide tracer. A downhole neutron probe was used to track the movement of the wetting front downward and outward from the gallery. Successive neutron measurements in vertical access tubes revealed that the introduced water reached the 125-foot bottom of the access tubes 14 weeks after the water was introduced into the gallery. The bromide tracer was detected in groundwater immediately below the gallery approximately 1 week later. The infiltration gallery was able to sustain an average flow rate of 2.3 gallons per minute. Prior to infiltration, the perchlorate concentration in groundwater below the gallery was 4,500 µg/L. Approximately 18 weeks after the start of infiltration, a perchlorate spike of 72,400 µg/L was detected below the gallery. The increase in perchlorate

  4. Impact of switching crop type on water and solute fluxes in deep vadose zone

    NASA Astrophysics Data System (ADS)

    Turkeltaub, T.; Kurtzman, D.; Russak, E. E.; Dahan, O.

    2015-12-01

    Switching crop type and consequently changing irrigation and fertilization regimes lead to alterations in deep percolation and solute concentrations of pore water. Herein, observations from the deep vadose zone and model simulations demonstrate the changes in water, chloride, and nitrate fluxes under a commercial greenhouse following the change from tomato to lettuce cropping. The site, located above a phreatic aquifer, was monitored for 5 years. A vadose-zone monitoring system was implemented under the greenhouse and provided continuous data on both temporal variations in water content and chemical composition of the pore water at multiple depths in the deep vadose zone (up to 20 m). Following crop switching, a significant reduction in chloride concentration and dramatic increase in nitrate were observed across the unsaturated zone. The changes in chemical composition of the vadose-zone pore water appeared as sequential breakthroughs across the unsaturated zone, initiating at land surface and propagating down toward the water table. Today, 3 years after switching the crops, penetration of the impact exceeds 10 m depth. Variations in the isotopic composition of nitrate (18O and 15N) in water samples obtained from the entire vadose zone clearly support a fast leaching process and mobilization of solutes across the unsaturated zone following the change in crop type. Water flow and chloride transport models were calibrated to observations acquired during an enhanced infiltration experiment. Forward simulation runs were performed with the calibrated models, constrained to tomato and lettuce cultivation regimes as surface boundary conditions. Predicted chloride and nitrate concentrations were in agreement with the observed concentrations. The simulated water drainage and nitrogen leaching implied that the observed changes are an outcome of recommended agricultural management practices.

  5. Tank 241-AX-104 upper vadose zone cone penetrometer demonstration sampling and analysis plan

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    FIELD, J.G.

    1999-02-02

    This sampling and analysis plan (SAP) is the primary document describing field and laboratory activities and requirements for the tank 241-AX-104 upper vadose zone cone penetrometer (CP) demonstration. It is written in accordance with Hanford Tank Initiative Tank 241-AX-104 Upper Vadose Zone Demonstration Data Quality Objective (Banning 1999). This technology demonstration, to be conducted at tank 241-AX-104, is being performed by the Hanford Tanks Initiative (HTI) Project as a part of Tank Waste Remediation System (TWRS) Retrieval Program (EM-30) and the Office of Science and Technology (EM-50) Tanks Focus Area. Sample results obtained as part of this demonstration will providemore » additional information for subsequent revisions to the Retrieval Performance Evaluation (RPE) report (Jacobs 1998). The RPE Report is the result of an evaluation of a single tank farm (AX Tank Farm) used as the basis for demonstrating a methodology for developing the data and analyses necessary to support making tank waste retrieval decisions within the context of tank farm closure requirements. The RPE includes a study of vadose zone contaminant transport mechanisms, including analysis of projected tank leak characteristics, hydrogeologic characteristics of tank farm soils, and the observed distribution of contaminants in the vadose zone in the tank farms. With limited characterization information available, large uncertainties exist as to the nature and extent of contaminants that may exist in the upper vadose zone in the AX Tank Farm. Traditionally, data has been collected from soils in the vadose zone through the installation of boreholes and wells. Soil samples are collected as the bore hole is advanced and samples are screened on site and/or sent to a laboratory for analysis. Some in-situ geophysical methods of contaminant analysis can be used to evaluate radionuclide levels in the soils adjacent to an existing borehole. However, geophysical methods require compensation for

  6. Development of the INEEL Site Wide Vadose Zone Roadmap

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yonk, Alan Keith

    2001-09-01

    The INEEL Vadose Zone Roadmap was developed to identify inadquacies in current knowledge, to assist in contaminant management capabilities relative to the INEEL vadose zone, and to ensure that ongoing and planned Science and Technology developments will meet the risk management challenges facing the INEEL in coming years. The primary objective of the Roadmap is to determine the S&T needs that will facilitate monitoring, characterization, prediction, and assessment activities necessary to support INEEL risk management decisions and to ensure that long-term stewardship of contaminated sites at the INEEL is achieved. The mission of the Roadmap is to insure that themore » long-term S&T strategy is aligned with site programs, that it takes advantage of progress made to date, and that it can assist in meeting the milestones and budgets of operations.« less

  7. TWRS vadose zone contamination issue expert panel report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shafer, D.S.

    1997-05-01

    When members were first canvassed for participation in the Vadose Zone Expert Panel the stated purpose for convening the Panel was to review a controversial draft report, the SX Tank Farm Report. This report was produced by a DOE Grand Junction Project Office (GJPO) contractor, RUST Geotech, now MACTEC-ERS, for the DOE Richland Office (DOERL). Three meetings were planned for June, July and August, 1995 to review the draft report and to complete a Panel report by mid-September. The Expert Panel has found its efforts confounded by various non-technical issues. The Expert Panel has chosen to address some of themore » non-technical issues in this Preface rather than to dilute the technical discussion that follows in the body of this independent expert panel status report (Panel Report). Rather than performing a straightforward manuscript review, the Panel was asked to resolve conflicting interpretations of gamma-ray logging measurements performed in vadose zone boreholes (drywells) surrounding the high-level radioactive wastes of the SX tank farm. There are numerous and complex technical issues that must be evaluated before the vertical and radial extent of contaminant migration at the SX tank farm can be accurately assessed. When the Panel first met in early June, 1996, it quickly became apparent that the scientific and technical issues were obscured by policy and institutional affairs which have polarized discussion among various segments of the Hanford organization. This situation reflects the kinds of institutional problems described separately in reports by the National Research Council of the National Academy of Sciences (NAS/NRC), The Hanford Tanks Environmental Impacts and Policy Choices and BmTiers to Science: Technical Management of the Department of Energy Environmental Remediation Program. The Vadose Zone Characterization Program, appears to be caught between conflicting pressures and organizational mandates, some imposed from outside DOE-RL and some self

  8. Atrazine retention and degradation in the vadose zone at a till plain site in central Indiana

    USGS Publications Warehouse

    Bayless, E.R.

    2001-01-01

    The vadose zone was examined as an environmental compartment where significant quantities of atrazine and its degradation compounds may be stored and transformed. The vadose zone was targeted because regional studies in the White River Basin indicated a large discrepancy between the mass of atrazine applied to fields and the amount of the pesticide and its degradation compounds that are measured in ground and surface water. A study site was established in a rotationally cropped field in the till plain of central Indiana. Data were gathered during the 1994 growing season to characterize the site hydrogeology and the distribution of atrazine, desethylatrazine, deisopropylatrazine, didealkylatrazine and hydroxyatrazine in runoff, pore water, and ground water. The data indicated that atrazine and its degradation compounds were transported from land surface to a depth of 1.5 m within 60 days of application, but were undetected in the saturated zone at nearby monitoring wells. A numerical model was developed, based on the field data, to provide information about processes that could retain and degrade atrazine in the vadose zone. Simulations indicated that evapotranspiration is responsible for surface directed soil-moisture flow during much of the growing season. This process causes retention and degradation of atrazine in the vadose zone. Increased residence time in the vadose zone leads to nearly complete transformation of atrazine and its degradation products to unquantified degradation compounds. As a result of mascropore flow, small quantities of atrazine and its degradation compounds may reach the saturated zone.

  9. Vadose Zone Transport Field Study: Detailed Test Plan for Simulated Leak Tests

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ward, Anderson L.; Gee, Glendon W.

    2000-06-23

    This report describes controlled transport experiments at well-instrumented field tests to be conducted during FY 2000 in support of DOE?s Vadose Zone Transport Field Study (VZTFS). The VZTFS supports the Groundwater/Vadose Zone Integration Project Science and Technology Initiative. The field tests will improve understanding of field-scale transport and lead to the development or identification of efficient and cost-effective characterization methods. These methods will capture the extent of contaminant plumes using existing steel-cased boreholes. Specific objectives are to 1) identify mechanisms controlling transport processes in soils typical of the hydrogeologic conditions of Hanford?s waste disposal sites; 2) reduce uncertainty in conceptualmore » models; 3) develop a detailed and accurate data base of hydraulic and transport parameters for validation of three-dimensional numerical models; and 4) identify and evaluate advanced, cost-effective characterization methods with the potential to assess changing conditions in the vadose zone, particularly as surrogates of currently undetectable high-risk contaminants. Pacific Northwest National Laboratory (PNNL) manages the VZTFS for DOE.« less

  10. Estimating the Impact of Vadose Zone Sources on Groundwater to Support Performance Assessment of Soil Vapor Extraction

    EPA Science Inventory

    Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. To support selection of an appropriate endpoint for the SVE remedy, an evaluation is needed to determine whether vadose zone contamination has been diminished sufficient...

  11. Soil Moisture Flow and Nitrate Movement Simulation through Deep and Heterogeneous Vadose Zone using Dual-porosity Approach

    NASA Astrophysics Data System (ADS)

    Yadav, B. K.; Tomar, J.; Harter, T.

    2014-12-01

    We investigate nitrate movement from non-point sources in deep, heterogeneous vadose zones, using multi-dimensional variably saturated flow and transport simulations. We hypothesize that porous media heterogeneity causes saturation variability that leads to preferential flow systems such that a significant portion of the vadose zone does not significantly contribute to flow. We solve Richards' equation and the advection-dispersion equation to simulate soil moisture and nitrate transport regimes in plot-scale experiments conducted in the San Joaquin Valley, California. We compare equilibrium against non-equilibrium (dual-porosity) approaches. In the equilibrium approach we consider each soil layer to have unique hydraulic properties as a whole, while in the dual-porosity approach we assume that large fractions of the porous flow domain are immobile. However we consider exchange of water and solute between mobile and immobile zone using the appropriate mass transfer terms. The results indicate that flow and transport in a nearly 16 m deep stratified vadose zone comprised of eight layers of unconsolidated alluvium experiences highly non-uniform, localized preferential flow and transport patterns leading to accelerated nitrate transfer. The equilibrium approach largely under-predicted the leaching of nitrate to groundwater while the dual-porosity approach showed higher rates of nitrate leaching, consistent with field observations. The dual-porosity approach slightly over-predicted nitrogen storage in the vadose zone, which may be the result of limited matrix flow or denitrification not accounted for in the model. Results of this study may be helpful to better predict fertilizer and pesticide retention times in deep vadose zone, prior to recharge into the groundwater flow system. Keywords: Nitrate, Preferential flow, Heterogeneous vadose zone, Dual-porosity approach

  12. CMI Remedy Selection for HE- and Barium-Contaminated Vadose Zone and Alluvium at LANL

    NASA Astrophysics Data System (ADS)

    Hickmott, D.; Reid, K.; Pietz, J.; Ware, D.

    2008-12-01

    A high explosives (HE) machining building outfall at Los Alamos National Laboratory's Technical Area 16 discharged millions of gallons of HE- and barium-contaminated water into the Canon de Valle watershed. The effluent contaminated surface soils, the alluvial aquifer, vadose zone waters, and deep-perched and regional groundwaters with HE and barium, frequently at levels greater than regulatory standards. Site characterization studies began in 1995 and included extensive monitoring of surface water, groundwater, soils, and subsurface solid media. Hydrogeologic and geophysical studies were conducted to help understand contaminant transport mechanisms and pathways. Results from the characterization studies were used to develop a site conceptual model. In 2000 the principal source area was removed. The ongoing Corrective Measure Study (CMS) and Corrective Measure Implementation (CMI) focus on residual vadose zone contamination and on the contaminated alluvial system. Regulators recently selected a CMI remedy that combined: 1) augmented source removal; 2) grouting of an HE- contaminated surge bed; 3) deployment of Stormwater Management System (SMS) stormfilters in contaminated springs; and 4) permeable reactive barriers (PRBs) in contaminated alluvium. The hydrogeologic conceptual model for the vadose zone and alluvial system as well as the status of the canyon as habitat for the Mexican Spotted Owl were key factors in selection of these minimal-environmental-impact remedies. The heterogeneous vadose zone, characterized by flow and contaminant transport in fractures and in surge beds, requires contaminant treatment at a point of discharge. The canyon PRB is being installed to capture water and contaminants prior to infiltration into the vadose zone. Pilot-scale testing of the SMS and lab-scale batch and column tests of a range of media suggest that granular activated carbon, zeolite, and gypsum may be effective media for removal of HE and/or barium from contaminated

  13. Evaluating Contaminant Flux from the Vadose Zone to the Groundwater in the Hanford Central Plateau. SX Tank Farms Case Study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Oostrom, Martinus; Last, George V.

    At the DOE Hanford Site, contaminants were discharged to the subsurface through engineered waste sites in the Hanford Central Plateau. Additional waste was released through waste storage tank leaks. Much of the contaminant inventory is still present within the unsaturated vadose zone sediments. The nature and extent of future groundwater contaminant plumes and the growth or decline of current groundwater plumes beneath the Hanford Central Plateau are a function of the contaminant flux from the vadose zone to the groundwater. In general, contaminant transport is slow through the vadose zone and it is difficult to directly measure contaminant flux inmore » the vadose zone. Predictive analysis, supported by site characterization and monitoring data, was applied using a structured, systems-based approach to estimate the future contaminant flux to groundwater in support of remediation decisions for the vadose zone and groundwater (Truex and Carroll 2013). The SX Tank Farm was used as a case study because of the existing contaminant inventory in the vadose zone, observations of elevated moisture content in portions of the vadose zone, presence of a limited-extent groundwater plume, and the relatively large amount and wide variety of data available for the site. Although the SX Tank Farm case study is most representative of conditions at tank farm sites, the study has elements that are also relevant to other types of disposal sites in the Hanford Central Plateau.« less

  14. Deep arid system hydrodynamics 1. Equilibrium states and response times in thick desert vadose zones

    USGS Publications Warehouse

    Walvoord, Michelle Ann; Plummer, Mitchell A.; Phillips, Fred M.; Wolfsberg, Andrew V.

    2002-01-01

    Quantifying moisture fluxes through deep desert soils remains difficult because of the small magnitude of the fluxes and the lack of a comprehensive model to describe flow and transport through such dry material. A particular challenge for such a model is reproducing both observed matric potential and chloride profiles. We propose a conceptual model for flow in desert vadose zones that includes isothermal and nonisothermal vapor transport and the role of desert vegetation in supporting a net upward moisture flux below the root zone. Numerical simulations incorporating this conceptual model match typical matric potential and chloride profiles. The modeling approach thereby reconciles the paradox between the recognized importance of plants, upward driving forces, and vapor flow processes in desert vadose zones and the inadequacy of the downward‐only liquid flow assumption of the conventional chloride mass balance approach. Our work shows that water transport in thick desert vadose zones at steady state is usually dominated by upward vapor flow and that long response times, of the order of 104–105 years, are required to equilibrate to existing arid surface conditions. Simulation results indicate that most thick desert vadose zones have been locked in slow drying transients that began in response to a climate shift and establishment of desert vegetation many thousands of years ago.

  15. Depth of the vadose zone controls aquifer biogeochemical conditions and extent of anthropogenic nitrogen removal

    USGS Publications Warehouse

    Szymczycha, Beata; Kroeger, Kevin D.; Crusius, John; Bratton, John F.

    2017-01-01

    We investigated biogeochemical conditions and watershed features controlling the extent of nitrate removal through microbial dinitrogen (N2) production within the surficial glacial aquifer located on the north and south shores of Long Island, NY, USA. The extent of N2 production differs within portions of the aquifer, with greatest N2 production observed at the south shore of Long Island where the vadose zone is thinnest, while limited N2production occurred under the thick vadose zones on the north shore. In areas with a shallow water table and thin vadose zone, low oxygen concentrations and sufficient DOC concentrations are conducive to N2production. Results support the hypothesis that in aquifers without a significant supply of sediment-bound reducing potential, vadose zone thickness exerts an important control of the extent of N2 production. Since quantification of excess N2 relies on knowledge of equilibrium N2concentration at recharge, calculated based on temperature at recharge, we further identify several features, such as land use and cover, seasonality of recharge, and climate change that should be considered to refine estimation of recharge temperature, its deviation from mean annual air temperature, and resulting deviation from expected equilibrium gas concentrations.

  16. Approach to the vadose zone monitoring in hazardous and solid waste disposal facilities

    NASA Astrophysics Data System (ADS)

    Twardowska, Irena

    2004-03-01

    In the solid waste (SW)disposal sites, in particular at the unlined facilities, at the remediated or newly-constructed units equipped with novel protective/reactive permeable barriers or at lined facilities with leachate collection systems that are prone to failure, the vadose zone monitoring should comprise besides the natural soil layer beneath the landfill, also the anthropogenic vadose zone, i.e. the waste layer and pore solutions in the landfill. The vadose zone screening along the vertical profile of SW facilities with use of direct invasive soil-core and soil-pore liquid techniques shows vertical downward redistribution of inorganic (macroconstituents and heavy metals) and organic (PAHs) contaminant loads in water infiltrating through the waste layer. These loads can make ground water down-gradient of the dump unfit for any use. To avoid damage of protective/reactive permeable barriers and liners, an installation of stationary monitoring systems along the waste layer profile during the construction of a landfill, which are amenable to generate accurate data and information in a near-real time should be considered including:(i) permanent samplers of pore solution, with a periodic pump-induced transport of collected solution to the surface, preferably with instant field measurements;(ii)chemical sensors with continuous registration of critical parameters. These techniques would definitely provide an early alert in case when the chemical composition of pore solution percolating downward the waste profile shows unfavorable transformations, which indicate an excessive contaminant load approaching ground water. The problems concerning invasive and stationary monitoring of the vadose zone in SW disposal facilities will be discussed at the background of results of monitoring data and properties of permeable protective/reactive barriers considered for use.

  17. The Mojave vadose zone: a subsurface biosphere analogue for Mars.

    PubMed

    Abbey, William; Salas, Everett; Bhartia, Rohit; Beegle, Luther W

    2013-07-01

    If life ever evolved on the surface of Mars, it is unlikely that it would still survive there today, but as Mars evolved from a wet planet to an arid one, the subsurface environment may have presented a refuge from increasingly hostile surface conditions. Since the last glacial maximum, the Mojave Desert has experienced a similar shift from a wet to a dry environment, giving us the opportunity to study here on Earth how subsurface ecosystems in an arid environment adapt to increasingly barren surface conditions. In this paper, we advocate studying the vadose zone ecosystem of the Mojave Desert as an analogue for possible subsurface biospheres on Mars. We also describe several examples of Mars-like terrain found in the Mojave region and discuss ecological insights that might be gained by a thorough examination of the vadose zone in these specific terrains. Examples described include distributary fans (deltas, alluvial fans, etc.), paleosols overlain by basaltic lava flows, and evaporite deposits.

  18. Measurement and partitioning of evapotranspiration for application to vadose zone studies

    USDA-ARS?s Scientific Manuscript database

    Partitioning evapotranspiration (ET) into its constituent components, soil evaporation (E) and plant transpiration (T), is important for vadose zone studies because E and T are often parameterized separately. However, partitioning ET is challenging, and many longstanding approaches have significant ...

  19. Effect of soil moisture on the sorption of trichloroethene vapor to vadose-zone soil at picatinny arsenal, New Jersey

    USGS Publications Warehouse

    Smith, J.A.; Chiou, C.T.; Kammer, J.A.; Kile, D.E.

    1990-01-01

    This report presents data on the sorption of trichloroethene (TCE) vapor to vadose-zone soil above a contaminated water-table aquifer at Picatinny Arsenal in Morris County, NJ. To assess the impact of moisture on TCE sorption, batch experiments on the sorption of TCE vapor by the field soil were carried out as a function of relative humidity. The TCE sorption decreases as soil moisture content increases from zero to saturation soil moisture content (the soil moisture content in equilibrium with 100% relative humidity). The moisture content of soil samples collected from the vadose zone was found to be greater than the saturation soil-moisture content, suggesting that adsorption of TCE by the mineral fraction of the vadose-zone soil should be minimal relative to the partition uptake by soil organic matter. Analyses of soil and soil-gas samples collected from the field indicate that the ratio of the concentration of TCE on the vadose-zone soil to its concentration in the soil gas is 1-3 orders of magnitude greater than the ratio predicted by using an assumption of equilibrium conditions. This apparent disequilibrium presumably results from the slow desorption of TCE from the organic matter of the vadose-zone soil relative to the dissipation of TCE vapor from the soil gas.

  20. Deep Vadose Zone Treatability Test for the Hanford Central Plateau: Interim Post-Desiccation Monitoring Results, Fiscal Year 2014

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Strickland, Christopher E.; Johnson, Christian D.

    Over decades of operation, the U.S. Department of Energy (DOE) and its predecessors have released nearly 2 trillion L (450 billion gal.) of liquid into the vadose zone at the Hanford Site. Much of this discharge of liquid waste into the vadose zone occurred in the Central Plateau, a 200 km 2 (75 mi 2) area that includes approximately 800 waste sites. Some of the inorganic and radionuclide contaminants in the deep vadose zone at the Hanford Site are at depths below the limit of direct exposure pathways, but may need to be remediated to protect groundwater. The Tri-Party Agenciesmore » (DOE, U.S. Environmental Protection Agency, and Washington State Department of Ecology) established Milestone M 015 50, which directed DOE to submit a treatability test plan for remediation of technetium-99 (Tc-99) and uranium in the deep vadose zone. These contaminants are mobile in the subsurface environment and have been detected at high concentrations deep in the vadose zone, and at some locations have reached groundwater. Testing technologies for remediating Tc-99 and uranium will also provide information relevant for remediating other contaminants in the vadose zone. A field test of desiccation is being conducted as an element of the DOE test plan published in March 2008 to meet Milestone M 015 50. The active desiccation portion of the test has been completed. Monitoring data have been collected at the field test site during the post-desiccation period and are reported herein. This is an interim data summary report that includes about 3 years of post-desiccation monitoring data. The DOE field test plan proscribes a total of 5 years of post-desiccation monitoring.« less

  1. Time lag estimates for nitrate travel through the vadose zone in Southland, New Zealand

    NASA Astrophysics Data System (ADS)

    Wilson, Scott; Chanut, Pierre; Ledgard, George; Rissmann, Clint

    2014-05-01

    A regional-scale study was carried out to calculate the travel time of a nitrate particle from the ground surface into shallow groundwater. The aim of the study was to obtain preliminary answers to two questions. Firstly, if leaching limits are set, how long would it take to see an improvement in shallow groundwater quality? Secondly, have groundwater nitrate concentrations reached equilibrium from recent dairy expansion in the region, or could we expect future increases? We applied a methodology that provides a balance between the detail and generalisation that is required for a regional-scale study. Steady-state advective transport through the vadose zone was modelled with water retention curves. These curves enable an estimate of the average volumetric water content of the vadose zone. The percentage saturation can then be used to calculate the vadose zone transit time if effective porosity, depth to the water table and annual average soil drainage are known. A time for mixing in the uppermost part of the aquifer has also been calculated. Two different vadose zone water retention curve models were used for comparison, the Brooks-Corey (1964), and the Van Genuchten (1980) methods. The water retention curves were parameterised by sediment texture via the Rawls and Brakensiek (1985) pedotransfer functions. Hydraulic properties were derived by positioning sediment textural descriptions on the Folk textural triangle, estimates of effective porosity from literature, and hydraulic conductivity values from aquifer tests. Uncertainty of parameter estimates was included by assigning standard deviations and appropriate probability distributions. Vadose zone saturation was modelled at 6,450 sites across the region with a Monte Carlo simulation involving 10,000 realisations. This generated a probability distribution of saturation for each site. Average volumetric water content of the vadose zone ranged from 8.5 to 40.7 % for the Brooks-Corey model and 12.9 to 36.3% for the

  2. Uncertainty assessment and implications for data acquisition in support of integrated hydrologic models

    NASA Astrophysics Data System (ADS)

    Brunner, Philip; Doherty, J.; Simmons, Craig T.

    2012-07-01

    The data set used for calibration of regional numerical models which simulate groundwater flow and vadose zone processes is often dominated by head observations. It is to be expected therefore, that parameters describing vadose zone processes are poorly constrained. A number of studies on small spatial scales explored how additional data types used in calibration constrain vadose zone parameters or reduce predictive uncertainty. However, available studies focused on subsets of observation types and did not jointly account for different measurement accuracies or different hydrologic conditions. In this study, parameter identifiability and predictive uncertainty are quantified in simulation of a 1-D vadose zone soil system driven by infiltration, evaporation and transpiration. The worth of different types of observation data (employed individually, in combination, and with different measurement accuracies) is evaluated by using a linear methodology and a nonlinear Pareto-based methodology under different hydrological conditions. Our main conclusions are (1) Linear analysis provides valuable information on comparative parameter and predictive uncertainty reduction accrued through acquisition of different data types. Its use can be supplemented by nonlinear methods. (2) Measurements of water table elevation can support future water table predictions, even if such measurements inform the individual parameters of vadose zone models to only a small degree. (3) The benefits of including ET and soil moisture observations in the calibration data set are heavily dependent on depth to groundwater. (4) Measurements of groundwater levels, measurements of vadose ET or soil moisture poorly constrain regional groundwater system forcing functions.

  3. COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES THROUGH THE VADOSE ZONE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Flury, Markus

    2003-09-14

    Contaminants have leaked into the vadose zone at the USDOE Hanford reservation. It is important to understand the fate and transport of these contaminants to design remediation strategies and long-term waste management plans at the Hanford reservation. Colloids may play an important role in fate and transport of strongly sorbing contaminants, such as Cs or Pu. This project seeks to improve the basic understanding of colloid and colloid-facilitated transport of contaminants in the vadose zone. The specific objectives addressed are: (1) Determine the structure, composition, and surface charge characteristics of colloidal particles formed under conditions similar to those occurring duringmore » leakage of waste typical of Hanford tank supernatants into soils and sediments surrounding the tanks. (2) Characterize the mutual interactions between colloids, contaminant, and soil matrix in batch experiments under various ionic strength and pH conditions. We will investigate the nature of the solid-liquid interactions and the kinetics of the reactions. (3) Evaluate mobility of colloids through soil under different degrees of water saturation and solution chemistry (ionic strength and pH). (4) Determine the potential of colloids to act as carriers to transport the contaminant through the vadose zone and verify the results through comparison with field samples collected under leaking tanks. (5) Improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facilitated transport for implementation into reactive chemical transport models. This project was in part supported by an NSF-IGERT grant to Washington State University. The IGERT grant provided funding for graduate student research and education, and two graduate students were involved in the EMSP project. The IGERT program also supported undergraduate internships. The project is part of a larger EMSP program to study fate and transport of contaminants under leaking Hanford waste tanks. The

  4. Transport and degradation of perchlorate in deep vadose zone: implications from direct observations during bioremediation treatment

    NASA Astrophysics Data System (ADS)

    Dahan, Ofer; Katz, Idan; Avishai, Lior; Ronen, Zeev

    2017-08-01

    An in situ bioremediation experiment of a deep vadose zone ( ˜ 40 m) contaminated with a high concentration of perchlorate (> 25 000 mg L-1) was conducted through a full-scale field operation. Favourable environmental conditions for microbiological reduction of perchlorate were sought by infiltrating an electron donor-enriched water solution using drip irrigation underlying an airtight sealing liner. A vadose zone monitoring system (VMS) was used for real-time tracking of the percolation process, the penetration depth of dissolved organic carbon (DOC), and the variation in perchlorate concentration across the entire soil depth. The experimental conditions for each infiltration event were adjusted according to insight gained from data obtained by the VMS in previous stages. Continuous monitoring of the vadose zone indicated that in the top 13 m of the cross section, perchlorate concentration is dramatically reduced from thousands of milligrams per litre to near-detection limits with a concurrent increase in chloride concentration. Nevertheless, in the deeper parts of the vadose zone (< 17 m), perchlorate concentration increased, suggesting its mobilization down through the cross section. Breakthrough of DOC and bromide at different depths across the unsaturated zone showed limited migration capacity of biologically consumable carbon and energy sources due to their enhanced biodegradation in the upper soil layers. Nevertheless, the increased DOC concentration with concurrent reduction in perchlorate and increase in the chloride-to-perchlorate ratio in the top 13 m indicate partial degradation of perchlorate in this zone. There was no evidence of improved degradation conditions in the deeper parts where the initial concentrations of perchlorate were significantly higher.

  5. Water recharge and solute transport through the vadose zone of fractured chalk under desert conditions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nativ, R.; Dahan, O.; Adar, E.

    In the present study the inferred mechanism of groundwater recharge and contamination was studied using tracer concentrations in the fractured vadose zone of the Avdat chalk. The results of this study are important for an evaluation of groundwater contamination from existing and planned facilities in the northern Negev desert in Israel. This study focused on the vicinity of the Ramat Hovav industrial chemical complex in the northern Negev, which also includes the national site for hazardous waste. Water recharge and solute migration rates were examined in five core holes and one borehole which penetrate the entire vadose zone and enabledmore » the collection of rock samples for chemical and isotopic analyses, and an observation of fracture distribution with depth. Tritium profiles were used to estimate water percolation rates through the vadose zone, chloride profiles were used to assess the migration rate of nonreactive solutes, and bromide profiles were also used to evaluate the migration rate of nonreactive contaminants. Deuterium and oxygen 18 profiles were used to assess the evaporation of the infiltrating water at and near land surface.« less

  6. Modeling non-steady state radioisotope transport in the vadose zone--A case study using uranium isotopes at Pena Blanca, Mexico

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ku, T. L.; Luo, S.; Goldstein, S. J.

    2009-06-01

    Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leadsmore » to a linear relationship between reciprocal U concentration and {sup 234}U/{sup 238}U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and {alpha}-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Pena Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced {sup 234}U/{sup 238}U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using {sup 234}U/{sup 238}U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.« less

  7. Application of Vadose Zone Monitoring Technology for Characterization of Leachate Generation in Landfills

    NASA Astrophysics Data System (ADS)

    aharoni, imri; dahan, ofer

    2016-04-01

    Ground water contamination due to landfill leachate percolation is considered the most severe environmental threat related to municipal solid waste landfills. Natural waste degradation processes in landfills normally produce contaminated leachates up to decades after the waste has been buried. Studies have shown that understanding the mechanisms which govern attenuation processes and the fate of pollutants in the waste and in the underlying unsaturated zone is crucial for evaluation of environmental risks and selection of a restoration strategy. This work focuses on a closed landfill in the coastal plain of Israel that was active until 2002 without any lining infrastructure. A vadose zone monitoring system (VMS) that was implemented at the site enables continuous measurements across the waste body (15 m thick) and underlying sandy vadose zone (16 m thick). Data collected by the VMS included continuous measurements of water content as well as chemical composition of the leachates across the entire waste and vadose zone cross section. Results indicated that winter rain percolated through the waste, generating wetting waves which were observed across the waste and unsaturated sediment from land surface until groundwater at 31 m bls. Quick percolation and high fluxes were observed in spite of the clay cover that was implemented at the site as part of the rehabilitation scheme. The results show that the flow pattern is controlled by a preferential mechanism within the waste body. Specific sections showed rapid fluxes in response to rain events, while other sections remained unaffected. In the underlying sandy vadose zone the flow pattern exhibited characteristics of matrix flow. Yet, some sections received higher fluxes due to the uneven discharge of leachates from the overlying waste body. Water samples collected from the waste layer indicate production of highly polluted leachates over 14 years after the landfill was closed. The chemical composition within the waste

  8. Vadose zone controls on damping of climate-induced transient recharge fluxes in U.S. agroecosystems

    NASA Astrophysics Data System (ADS)

    Gurdak, Jason

    2017-04-01

    Understanding the physical processes in the vadose zone that link climate variability with transient recharge fluxes has particular relevance for the sustainability of groundwater-supported irrigated agriculture and other groundwater-dependent ecosystems. Natural climate variability on interannual to multidecadal timescales has well-documented influence on precipitation, evapotranspiration, soil moisture, infiltration flux, and can augment or diminish human stresses on water resources. Here the behavior and damping depth of climate-induced transient water flux in the vadose zone is explored. The damping depth is the depth in the vadose zone that the flux variation damps to 5% of the land surface variation. Steady-state recharge occurs when the damping depth is above the water table, and transient recharge occurs when the damping depth is below the water table. Findings are presented from major agroecosystems of the United States (U.S.), including the High Plains, Central Valley, California Coastal Basin, and Mississippi Embayment aquifer systems. Singular spectrum analysis (SSA) is used to identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). SSA results indicate that nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. Results from HYDRUS-1D simulations indicate that transient water flux through the vadose zone are controlled by highly nonlinear interactions between mean infiltration flux and infiltration period related to the modes of climate

  9. Hydraulic and geochemical framework of the Idaho National Engineering and Environmental Laboratory vadose zone

    USGS Publications Warehouse

    Nimmo, John R.; Rousseau, Joseph P.; Perkins, Kim S.; Stollenwerk, Kenneth G.; Glynn, Pierre D.; Bartholomay, Roy C.; Knobel, LeRoy L.

    2004-01-01

    Questions of major importance for subsurface contaminant transport at the Idaho National Engineering and Environmental Laboratory (INEEL) include (i) travel times to the aquifer, both average or typical values and the range of values to be expected, and (ii) modes of contaminant transport, especially sorption processes. The hydraulic and geochemical framework within which these questions are addressed is dominated by extreme heterogeneity in a vadose zone and aquifer consisting of interbedded basalts and sediments. Hydraulically, major issues include diverse possible types of flow pathways, extreme anisotropy, preferential flow, combined vertical and horizontal flow, and temporary saturation or perching. Geochemically, major issues include contaminant mobility as influenced by redox conditions, the concentration of organic and inorganic complexing solutes and other local variables, the interaction with infiltrating waters and with the contaminant source environment, and the aqueous speciation of contaminants such as actinides. Another major issue is the possibility of colloid transport, which inverts some of the traditional concepts of mobility, as sorbed contaminants on mobile colloids may be transported with ease compared with contaminants that are not sorbed. With respect to the goal of minimizing aquifer concentrations of contaminants, some characteristics of the vadose zone are essentially completely favorable. Examples include the great thickness (200 m) of the vadose zone, and the presence of substantial quantities of fine sediments that can retard contaminant transport both hydraulically and chemically. Most characteristics, however, have both favorable and unfavorable aspects. For example, preferential flow, as promoted by several notable features of the vadose zone at the INEEL, can provide fast, minimally sorbing pathways for contaminants to reach the aquifer easily, but it also leads to a wide dispersal of contaminants in a large volume of subsurface

  10. Vadose zone attenuation of organic compounds at a crude oil spill site - interactions between biogeochemical reactions and multicomponent gas transport.

    PubMed

    Molins, S; Mayer, K U; Amos, R T; Bekins, B A

    2010-03-01

    Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation coupled with sequential electron acceptor consumption, ingress of atmospheric O(2), and the release of CH(4) and CO(2) from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O(2), CH(4), and CO(2)) and non-reactive (Ar and N(2)) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH(4) concentrations. In accordance with field observations, zones of volatilization and CH(4) generation are correlated to slightly elevated total gas pressures and low partial pressures of N(2) and Ar, while zones of aerobic CH(4) oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N(2) and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH(4), and to a more limited extent to O(2) ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions

  11. Vadose zone attenuation of organic compounds at a crude oil spill site - Interactions between biogeochemical reactions and multicomponent gas transport

    USGS Publications Warehouse

    Molins, S.; Mayer, K.U.; Amos, R.T.; Bekins, B.A.

    2010-01-01

    Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation coupled with sequential electron acceptor consumption, ingress of atmospheric O2, and the release of CH4 and CO2 from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O2, CH4, and CO2) and non-reactive (Ar and N2) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH4 concentrations. In accordance with field observations, zones of volatilization and CH4 generation are correlated to slightly elevated total gas pressures and low partial pressures of N2 and Ar, while zones of aerobic CH4 oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N2 and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH4, and to a more limited extent to O2 ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon

  12. The vadose zone as a geoindicator of environmental change and groundwater quality in water-scarce areas

    NASA Astrophysics Data System (ADS)

    Edmunds, W. M.; Baba Goni, I.; Gaye, C. B.; Jin, L.

    2013-12-01

    Inert and reactive tracers in moisture profiles provide considerable potential for the vadose zone to be used as an indicator of rapid environmental change. This indicator is particularly applicable in areas of water stress where long term (decade to century) scale records may be found in deep unsaturated zones in low rainfall areas and provide insights into recent recharge, climate variation and water-rock interactions which generate groundwater quality. Unsaturated zone Cl records obtained by elutriation of moisture are used widely for estimating recharge and water balance studies; isotope profiles (3H, δ2H, δ18O) from total water extraction procedures are used for investigation of residence times and hydrological processes. Apart from water taken using lysimeters, little work has been conducted directly on the geochemistry of pore fluids. This is mainly due to the difficulties of extraction of moisture from unsaturated material with low water contents (typically 2-6 wt%) and since dilution methods can create artifacts. Using immiscible liquid displacement techniques it is now possible to directly investigate the geochemistry of moisture from unsaturated zone materials. Profiles up to 35m from Quaternary sediments from dryland areas of the African Sahel (Nigeria, Senegal) as well as Inner Mongolia, China are used to illustrate the breadth of information obtainable from vadose zone profiles. Using pH, major and trace elements and comparing with isotopic data, a better understanding is gained of timescales of water movement, aquifer recharge, environmental records and climate history as well as water-rock interaction and contaminant behaviour. The usefulness of tritium as residence time indicator has now expired following cessation of atmospheric thermonuclear testing and through radioactive decay. Providing the rainfall Cl, moisture contents and bulk densities of the sediments are known, then Cl accumulation can be substituted to estimate timescales. Profiles

  13. Role of the sedimentary structure of the urban vadose zone (URVAZO) on the transfer of heavy metals of an urban stormwater basin

    NASA Astrophysics Data System (ADS)

    Angulo-Jaramillo, R.; Winiarski, T.; Goutaland, D.; Lassabatere, L.

    2009-12-01

    Stormwater infiltration basins have become a common alternative practice to traditional stormwater pipe networks in urban areas. They are often built in permeable subsurface soils (Urban Vadose Zone, URVAZO), such as alluvial deposits. These sedimentary deposits are highly heterogeneous and generate preferential flow paths that may cause either rapid or non-uniform transport of contaminants at great depths. The understanding of how subsurface vadose zone heterogeneities transfer contaminant and fluid flow to the aquifer still remains a challenge in urban hydrology. Indeed, urban stormwater may contain pollutants that can contaminate either soil or groundwater. The aim of this study is to evaluate the role of the lithological heterogeneity of a glaciofluvial deposit underlying an urban infiltration basin on the link between water flow and heavy metals retention. A trench wall (14m length x 3m depth) was exposed by excavating the glaciofluvial formation. By a hydrogeophysical approach based on a sedimentary structural units and in situ hydraulic characterization (Beerkan tests), a realistic hydrostratigraphic 2D model was defined. The trench was sampled on nine vertical sections of 1.5m length, with ten samples per vertical section following each lithofacies. A total of 90 samples were analyzed. Coarse (mechanical sieving) and fine (laser diffraction) particle size distribution analysis, as well as the concentration of three replicates of Pb, Cu, Zn and organic matter (OM) was measured for each sample. The principal component analysis shows a strong correlation between metal concentration and the lithofacies. This hydrostratigraphic model was implemented in the finite element program Hydrus2D. The soil heterogeneity exerts an impact on the heterogeneity of the water content field under slightly saturated conditions, as they induce capillary barrier effects. These capillary barrier effects may generate water accumulation in some lithofacies overlying matrix

  14. Evaluating Transport and Attenuation of Inorganic Contaminants in the Vadose Zone for Aqueous Waste Disposal Sites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Oostrom, Martinus; Tartakovsky, Guzel D.

    An approach was developed for evaluating vadose zone transport and attenuation of aqueous wastes containing inorganic (non-volatile) contaminants that were disposed of at the land surface (i.e., directly to the ground in cribs, trenches, tile fields, etc.) and their effect on the underlying groundwater. The approach provides a structured method for estimating transport of contaminants through the vadose zone and the resulting temporal profile of groundwater contaminant concentrations. The intent of the approach is also to provide a means for presenting and explaining the results of the transport analysis in the context of the site-specific waste disposal conditions and sitemore » properties, including heterogeneities and other complexities. The document includes considerations related to identifying appropriate monitoring to verify the estimated contaminant transport and associated predictions of groundwater contaminant concentrations. While primarily intended for evaluating contaminant transport under natural attenuation conditions, the approach can also be applied to identify types of, and targets for, mitigation approaches in the vadose zone that would reduce the temporal profile of contaminant concentrations in groundwater, if needed.« less

  15. Modeling non-steady state radioisotope transport in the vadose zone - A case study using uranium isotopes at Peña Blanca, Mexico

    NASA Astrophysics Data System (ADS)

    Ku, T. L.; Luo, S.; Goldstein, S. J.; Murrell, M. T.; Chu, W. L.; Dobson, P. F.

    2009-10-01

    Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leads to a linear relationship between reciprocal U concentration and 234U/ 238U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and α-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Peña Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced 234U/ 238U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using 234U/ 238U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.

  16. Linking carbon and hydrologic fluxes in the critical zone: Observations from high-frequency monitoring of a weathered bedrock vadose zone

    NASA Astrophysics Data System (ADS)

    Tune, A. K.; Druhan, J. L.; Wang, J.; Cargill, S.; Murphy, C.; Rempe, D. M.

    2017-12-01

    A principle challenge in quantifying feedbacks between continental weathering and atmospheric CO2 is to improve understanding of how biogeochemical processes in the critical zone influence the distribution and mobility of organic and inorganic carbon. In particular, in landscapes characterized by thin soils and heterogeneous weathered and fractured bedrock, little data exist to inform and constrain predictive models for carbon dynamics. Here, we present the results of an intensive water and gas sampling campaign across an 18 m thick, variably saturated argillite weathering profile in the Eel River CZO. We monitor water content in situ and regularly collect samples of freely-draining water, tightly-held water, and gas through wet and dry seasons using a novel Vadose-zone Monitoring System (VMS) consisting of sensors and samplers distributed across a 20 m long inclined borehole. This novel approach facilitates the interception of gas and water during transport across the entire variably saturated weathering profile. The data demonstrate that seasonal changes in saturation control the vertical distribution and mobility of carbon in the fractured critical zone. Concentrations of gaseous CO2, O2, and dissolved organic and inorganic carbon fluctuate significantly and repeatably with seasonal additions of water infiltrating the weathered bedrock. A persistent vertical structure in the concentrations of dissolved phases and gas concentrations broadly corresponds to depths associated with unsaturated, seasonally saturated, and chronically saturated zones. Associated variations in the vertical structure of mineralogy and elemental composition, including solid phase organic carbon content, are observed in core obtained during drilling. Together, our observations indicate significant respiration of organic carbon at depths greater than the base of the soil, and thus motivate further investigation of the role of heterogeneous weathered, bedrock environments, which are needed to

  17. Aquifer recharge with stormwater runoff in urban areas: Influence of vadose zone thickness on nutrient and bacterial transfers from the surface of infiltration basins to groundwater.

    PubMed

    Voisin, Jérémy; Cournoyer, Benoit; Vienney, Antonin; Mermillod-Blondin, Florian

    2018-10-01

    Stormwater infiltration systems (SIS) have been built in urban areas to reduce the environmental impacts of stormwater runoff. Infiltration basins allow the transfer of stormwater runoff to aquifers but their abilities to retain contaminants depend on vadose zone properties. This study assessed the influence of vadose zone thickness (VZT) on the transfer of inorganic nutrients (PO 4 3- , NO 3 - , NH 4 + ), dissolved organic carbon (total -DOC- and biodegradable -BDOC-) and bacteria. A field experiment was conducted on three SIS with a thin vadose zone (<3 m) and three SIS with a thick vadose zone (>10 m). Water samples were collected at three times during a rainy period of 10 days in each infiltration basin (stormwater runoff), in the aquifer impacted by infiltration (impacted groundwater) and in the same aquifer but upstream of the infiltration area (non-impacted groundwater). Inorganic nutrients, organic matter, and dissolved oxygen (DO) were measured on all water samples. Bacterial community structures were investigated on water samples through a next-generation sequencing (NGS) scheme of 16S rRNA gene amplicons (V5-V6). The concentrations of DO and phosphate measured in SIS-impacted groundwaters were significantly influenced by VZT due to distinct biogeochemical processes occurring in the vadose zone. DOC and BDOC were efficiently retained in the vadose zone, regardless of its thickness. Bacterial transfers to the aquifer were overall low, but data obtained on day 10 indicated a significant bacterial transfer in SIS with a thin vadose zone. Water transit time and water saturation of the vadose zone were found important parameters for bacterial transfers. Most bacterial taxa (>60%) from impacted groundwaters were not detected in stormwater runoff and in non-impacted groundwaters, indicating that groundwater bacterial communities were significantly modified by processes associated with infiltration (remobilization of bacteria from vadose zone and/or species

  18. Conceptual Model of Uranium in the Vadose Zone for Acidic and Alkaline Wastes Discharged at the Hanford Site Central Plateau

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Szecsody, James E.; Qafoku, Nikolla

    2014-09-01

    Historically, uranium was disposed in waste solutions of varying waste chemistry at the Hanford Site Central Plateau. The character of how uranium was distributed in the vadose zone during disposal, how it has continued to migrate through the vadose zone, and the magnitude of potential impacts on groundwater are strongly influenced by geochemical reactions in the vadose zone. These geochemical reactions can be significantly influenced by the disposed-waste chemistry near the disposal location. This report provides conceptual models and supporting information to describe uranium fate and transport in the vadose zone for both acidic and alkaline wastes discharged at amore » substantial number of waste sites in the Hanford Site Central Plateau. The conceptual models include consideration of how co-disposed acidic or alkaline fluids influence uranium mobility in terms of induced dissolution/precipitation reactions and changes in uranium sorption with a focus on the conditions near the disposal site. This information, when combined with the extensive information describing uranium fate and transport at near background pH conditions, enables focused characterization to support effective fate and transport estimates for uranium in the subsurface.« less

  19. Changes in water and solute fluxes in the vadose zone after switching crops

    NASA Astrophysics Data System (ADS)

    Turkeltaub, Tuvia; Dahan, Ofer; Kurtzman, Daniel

    2015-04-01

    Switching crop type and therefore changing irrigation and fertilization regimes leads to alternation in deep percolation and concentrations of solutes in pore water. Changes of fluxes of water, chloride and nitrate under a commercial greenhouse due to a change from tomato to green spices were observed. The site, located above the a coastal aquifer, was monitored for the last four years. A vadose-zone monitoring system (VMS) was implemented under the greenhouse and provided continuous data on both the temporal variation in water content and the chemical composition of pore water at multiple depths in the deep vadose zone (~20 m). Chloride and nitrate profiles, before and after the crop type switching, indicate on a clear alternation in soil water solutes concentrations. Before the switching of the crop type, the average chloride profile ranged from ~130 to ~210, while after the switching, the average profile ranged from ~34 to ~203 mg L-1, 22% reduction in chloride mass. Counter trend was observed for the nitrate concentrations, the average nitrate profile before switching ranged from ~11 to ~44 mg L-1, and after switching, the average profile ranged from ~500 to ~75 mg L-1, 400% increase in nitrate mass. A one dimensional unsaturated water flow and chloride transport model was calibrated to transient deep vadose zone data. A comparison between the simulation results under each of the surface boundary conditions of the vegetables and spices cultivation regime, clearly show a distinct alternation in the quantity and quality of groundwater recharge.

  20. Impact of CO2 Intrusion into USDWs, the Vadose Zone, and Indoor Air

    EPA Science Inventory

    The U.S. Environmental Protection Agency’s (EPA) Water Research Program in the Office of Research and Development is conducting research to better detect and quantify leakage into USDWs, the vadose zone, the atmosphere, and buildings. Research in this initiative is focused in thr...

  1. Hydrologic and geochemical dynamics of vadose zone recharge in a mantled karst aquifer: Results of monitoring drip waters in Mystery Cave, Minnesota

    USGS Publications Warehouse

    Doctor, Daniel H.; Alexander, E. Calvin; Jameson, Roy A.; Alexander, Scott C.

    2015-01-01

    Caves provide direct access to flows through the vadose zone that recharge karst aquifers. Although many recent studies have documented the highly dynamic processes associated with vadose zone flows in karst settings, few have been conducted in mantled karst settings, such as that of southeastern Minnesota. Here we present some results of a long-term program of cave drip monitoring conducted within Mystery Cave, Minnesota. In this study, two perennial ceiling drip sites were monitored between 1997 and 2001. The sites were located about 90 m (300 ft) apart along the same cave passage approximately 18 m (60 ft) below the surface; 7 to 9 m (20 to 30 ft) of loess and 12 m (40 ft) of flat-lying carbonate bedrock strata overlie the cave. Records of drip rate, electrical conductivity, and water temperature were obtained at 15 minute intervals, and supplemented with periodic sampling for major ion chemistry and water stable isotopes. Patterns in flow and geochemistry emerged at each of the two drip sites that were repeated year after year. Although one site responded relatively quickly (within 2-7 hours) to surface recharge events while the other responded more slowly (within 2-5 days), thresholds of antecedent moisture needed to be overcome in order to produce a discharge response at both sites. The greatest amount of flow was observed at both sites during the spring snowmelt period. Rainfall events less than 10 mm (0.4 in) during the summer months generally did not produce a drip discharge response, yet rapid drip responses were observed following intense storm events after periods of prolonged rainfall. The chemical data from both sites indicate that reservoirs of vadose zone water with distinct chemical signatures mixed during recharge events, and drip chemistry returned to a baseline composition during low flow periods. A reservoir with elevated chloride and sulfate concentrations impacts the slow-response drip site with each recharge event, but does not similarly

  2. Characterization and Remediation of Chlorinated Volatile Organic Contaminants in the Vadose Zone: An Overview of Issues and Approaches

    PubMed Central

    Brusseau, Mark L.; Carroll, Kenneth C.; Truex, Michael J.; Becker, David J.

    2014-01-01

    Contamination of vadose-zone systems by chlorinated solvents is widespread, and poses significant potential risk to human health through impacts on groundwater quality and vapor intrusion. Soil vapor extraction (SVE) is the presumptive remedy for such contamination, and has been used successfully for innumerable sites. However, SVE operations typically exhibit reduced mass-removal effectiveness at some point due to the impact of poorly accessible contaminant mass and associated mass-transfer limitations. Assessment of SVE performance and closure is currently based on characterizing contaminant mass discharge associated with the vadose-zone source, and its impact on groundwater or vapor intrusion. These issues are addressed in this overview, with a focus on summarizing recent advances in our understanding of the transport, characterization, and remediation of chlorinated solvents in the vadose zone. The evolution of contaminant distribution over time and the associated impacts on remediation efficiency will be discussed, as will the potential impact of persistent sources on groundwater quality and vapor intrusion. In addition, alternative methods for site characterization and remediation will be addressed. PMID:25383058

  3. Arid Zone Hydrology

    USDA-ARS?s Scientific Manuscript database

    Arid zone hydrology encompasses a wide range of topics and hydro-meteorological and ecological characteristics. Although arid and semi-arid watersheds perform the same functions as those in humid environments, their hydrology and sediment transport characteristics cannot be readily predicted by inf...

  4. Monitoring the Vadose Zone Moisture Regime Below a Surface Barrier

    NASA Astrophysics Data System (ADS)

    Zhang, Z. F.; Strickland, C. E.; Field, J. G.

    2009-12-01

    A 6000 m2 interim surface barrier has been constructed over a portion of the T Tank Farm in the Depart of Energy’s Hanford site. The purpose of using a surface barrier was to reduce or eliminate the infiltration of meteoric precipitation into the contaminated soil zone due to past leaks from Tank T-106 and hence to reduce the rate of movement of the plume. As part of the demonstration effort, vadose zone moisture is being monitored to assess the effectiveness of the barrier on the reduction of soil moisture flow. A vadose zone monitoring system was installed to measure soil water conditions at four horizontal locations (i.e., instrument Nests A, B, C, and D) outside, near the edge of, and beneath the barrier. Each instrument nest consists of a capacitance probe with multiple sensors, multiple heat-dissipation units, and a neutron probe access tube used to measure soil-water content and soil-water pressure. Nest A serves as a control by providing subsurface conditions outside the influence of the surface barrier. Nest B provides subsurface measurements to assess barrier edge effects. Nests C and D are used to assess the impact of the surface barrier on soil-moisture conditions beneath it. Monitoring began in September 2006 and continues to the present. To date, the monitoring system has provided high-quality data. Results show that the soil beneath the barrier has been draining from the shallower depth. The lack of climate-caused seasonal variation of soil water condition beneath the barrier indicates that the surface barrier has minimized water exchange between the soil and the atmosphere.

  5. Analysis of Vadose Hydrology at Jinapsan Cave, Guam, Mariana Islands

    NASA Astrophysics Data System (ADS)

    Bautista, K. K.; Jenson, J. W.; Lander, M.; Noronha, A. L.; Righetti, T.

    2016-12-01

    Six years of monthly data were analyzed from an active tropical limestone cave in Guam, the southernmost of the Mariana Islands, in the western Pacific Ocean. The purpose of this study was to characterize vadose processes of aquifer recharge in the Plio-Pleistocene Mariana Limestone, which occupies about 75% of the surface of the Northern Guam Lens Aquifer, which produces 90% of the island's drinking water. This hydrogeologic study was conducted concurrent with paleoclimate research, in which correlative data on CO2 and other cave meteorological parameters are also collected. For this study, a ground survey grid was established on the surface above the cave, a vegetated talus slope at the foot of the >150-m cliff in the Mariana Limestone behind the cave. Cave and vadose zone 3-D models were constructed from the surface survey and an interior cave survey. Cross sections display talus slope features (33°), notational talus grain size distribution, inferred epikarst and vadose layer dimensions, cave slope (-34°) and structural and geomorphic features of the cave, including a brackish sea-level pool at the cave bottom. GIS products include georeferenced cave boundary and cave room shapefiles. A plan-view map displays significant boulder talus and limestone forest trees, cave entrance location and the underlying cave boundary and fractures mapped on the cave ceiling. Thicknesses of the talus and vadose bedrock sections range from 1.3 to 17.0 meters and 1.7 to 46.4 meters, respectively. Drip rate and discharge rate data from 7 cave stations are presented in graphs showing varying responses between percolation and changes in rainfall during wet (Jul-Dec) and dry (Jan-Jun) seasons. Three stations exhibited fast responses to wet season rainfall, which gradually dropped during the dry season. Two of these stations are at separate cave ceiling fractures. The third is indiscernible from its distance (>4m) above the floor. Three stations exhibited slow responses in both wet

  6. Model Fit to Experimental Data for Foam-Assisted Deep Vadose Zone Remediation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roostapour, A.; Lee, G.; Zhong, Lirong

    2014-01-15

    Foam has been regarded as a promising means of remeidal amendment delivery to overcome subsurface heterogeneity in subsurface remediation processes. This study investigates how a foam model, developed by Method of Characteristics and fractional flow analysis in the companion paper of Roostapour and Kam (2012), can be applied to make a fit to a set of existing laboratory flow experiments (Zhong et al., 2009) in an application relevant to deep vadose zone remediation. This study reveals a few important insights regarding foam-assisted deep vadose zone remediation: (i) the mathematical framework established for foam modeling can fit typical flow experiments matchingmore » wave velocities, saturation history , and pressure responses; (ii) the set of input parameters may not be unique for the fit, and therefore conducting experiments to measure basic model parameters related to relative permeability, initial and residual saturations, surfactant adsorption and so on should not be overlooked; and (iii) gas compressibility plays an important role for data analysis, thus should be handled carefully in laboratory flow experiments. Foam kinetics, causing foam texture to reach its steady-state value slowly, may impose additional complications.« less

  7. Automated Passive Capillary Lysimeters for Estimating Water Drainage in the Vadose Zone

    NASA Astrophysics Data System (ADS)

    Jabro, J.; Evans, R.

    2009-04-01

    In this study, we demonstrated and evaluated the performance and accuracy of an automated PCAP lysimeters that we designed for in-situ continuous measuring and estimating of drainage water below the rootzone of a sugarbeet-potato-barley rotation under two irrigation frequencies. Twelve automated PCAPs with sampling surface dimensions of 31 cm width * 91 cm long and 87 cm in height were placed 90 cm below the soil surface in a Lihen sandy loam. Our state-of-the-art design incorporated Bluetooth wireless technology to enable an automated datalogger to transmit drainage water data simultaneously every 15 minutes to a remote host and had a greater efficiency than other types of lysimeters. It also offered a significantly larger coverage area (2700 cm2) than similarly designed vadose zone lysimeters. The cumulative manually extracted drainage water was compared with the cumulative volume of drainage water recorded by the datalogger from the tipping bucket using several statistical methods. Our results indicated that our automated PCAPs are accurate and provided convenient means for estimating water drainage in the vadose zone without the need for costly and manually time-consuming supportive systems.

  8. An Experimental Study of Diffusivity of Technetium-99 in Hanford Vadose Zone Sediments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mattigod, Shas V.; Bovaird, Chase C.; Wellman, Dawn M.

    2012-11-01

    One of the methods being considered at the Hanford site in Washington for safely disposing of low-level radioactive wastes (LLW) is to encase the waste in concrete and entomb the packages in the Hanford vadose zone sediments. The current plan for waste isolation consists of stacking low-level waste packages on a trench floor, surrounding the stacks with reinforced steel, and encasing these packages with concrete. Any failure of the concrete encasement may result in water intrusion and consequent mobilization of radionuclides from the waste packages. The mobilized radionuclides may escape from the encased concrete by mass flow and/or diffusion andmore » move into the surrounding subsurface sediments. It is therefore necessary to conduct an assessment of the performance of the concrete encasement structure and the surrounding soil’s ability to retard radionuclide migration. The retardation factors for radionuclides contained in the waste packages can be determined from measurements of diffusion coefficients for these contaminants through concrete and fill material. Because of their anionic nature in aqueous solutions, the radionuclides, 99Tc and 129I were identified as long-term dose contributors in LLW. The leachability and/or diffusion of these radionuclide species must be measured in order to assess the long-term performance of waste grouts when contacted with vadose-zone porewater or groundwater. To measure the diffusivity, a set of experiments were conducted using 99Tc-spiked concrete (with 0 and 4% metallic iron additions) in contact with unsaturated soil half-cells that reflected the typical moisture contents of Hanford vadose zone sediments. The 99Tc diffusion profiles in the soil half cells were measured after a time lapse of ~1.9 yr. Using the concentration profiles, the 99Tc diffusivity coefficients were calculated based on Fick’s Second Law.« less

  9. Remediation of Deep Vadose Zone Radionuclide and Metal Contamination: Status and Issues

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dresel, P. Evan; Truex, Michael J.; Cantrell, Keri

    2008-12-30

    This report documents the results of a PNNL literature review to report on the state of maturity of deep vadose zone remediation technologies for metal contaminants including some radionuclides. Its recommendations feed into decisionmakers need for scientific information and cost-effective in situ remediation technlogies needed under DOE's Environmental Management initiative Enhanced Remediation Methods: Scientific & Technical Basis for In Stu Treatment Systems for Metals and Radionuclides.

  10. ESTIMATION OF INFILTRATION RATE IN THE VADOSE ZONE: COMPILATION OF SIMPLE MATHEMATICAL MODELS - VOLUME I

    EPA Science Inventory

    The unsaturated or vadose zone provides a complex system for the simulation of water movement and contaminant transport and fate. Numerous models are available for performing simulations related to the movement of water. There exists extensive documentation of these models. Ho...

  11. Impact of Heterogeneity on Vadose Zone Drainage During Pumping: Numerical Simulations of the Borden Aquifer

    NASA Astrophysics Data System (ADS)

    Bunn, M. I.; Jones, J.; Endres, A. L.

    2009-05-01

    Unconfined aquifers are in direct contact with the earth's surface; hence, they are an important focus in groundwater recharge and contaminant transport studies. While pumping tests have long been used to quantify aquifer properties, the contribution of drainage from the vadose zone during pumping has been the subject of debate for decades. In 2001, a highly detailed data set was collected during a seven-day pumping test in the unconfined aquifer at CFB Borden, Ontario (Bevan et al., 2005). The frequent observation of moisture content profiles during the test has initiated a closer examination of the vadose zone response to pumping. The moisture profiles collected during the test were obtained using a neutron probe. The neutron data depicts a capillary fringe thickness that increases with both proximity to the pumping well and duration of pumping. This capillary fringe extension results in delayed drainage that persists to the end of the seven-day test with the shape of the transition zone remaining constant (Bevan et al., 2005). Simulations of the pumping test were conducted using Hydrogeosphere (Therrien et al., 2006). Initial simulations were completed based on the conceptual model of a homogeneous and slightly anisotropic aquifer. The simulation results replicated the observed piezometric response, but were unable to produce any change in the thickness of the capillary fringe. It was hypothesized that the discrepancy between observations and simulation results may be the result of assumptions such as the homogeneity of the hydraulic conductivity field. In an effort to replicate this potential mechanism for the observed extension, the conceptual model was updated to better reflect the mildly heterogeneous hydraulic conductivity field of the Borden aquifer. Conductivity fields were generated using the statistical description of the Borden aquifer given by Sudicky (1986) with an adjusted mean log conductivity to better approximate the observed piezometric response

  12. ESTIMATION OF INFILTRATION RATE IN THE VADOSE ZONE: APPLICATION OF SELECTED MATHEMATICAL MODELS - VOLUME II

    EPA Science Inventory

    Movement of water into and through the vadose zone is of great importance to the assessment of contaminant fate and transport, agricultural management, and natural resource protection. The process of water movement is very dynamic, changing dramatically over time and space. Inf...

  13. Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cantrell, Kirk J.; Zachara, John M.; Dresel, P. Evan

    This data package discusses the geochemistry of vadose zone sediments beneath the single-shell tank farms at the U.S. Department of Energy’s (DOE’s) Hanford Site. The purpose of the report is to provide a review of the most recent and relevant geochemical process information available for the vadose zone beneath the single-shell tank farms and the Integrated Disposal Facility. Two companion reports to this one were recently published which discuss the geology of the farms (Reidel and Chamness 2007) and groundwater flow and contamination beneath the farms (Horton 2007).

  14. Unintentional contaminant transfer from groundwater to the vadose zone during source zone remediation of volatile organic compounds.

    PubMed

    Chong, Andrea D; Mayer, K Ulrich

    2017-09-01

    Historical heavy use of chlorinated solvents in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater in North America and worldwide. As a result, remediation of chlorinated solvents is required at many sites. For source zone treatment, common remediation strategies include in-situ chemical oxidation (ISCO) using potassium or sodium permanganate, and the enhancement of biodegradation by primary substrate addition. It is well known that these remediation methods tend to generate gas (carbon dioxide (CO 2 ) in the case of ISCO using permanganate, CO 2 and methane (CH 4 ) in the case of bioremediation). Vigorous gas generation in the presence of chlorinated solvents, which are categorized as volatile organic contaminants (VOCs), may cause gas exsolution, ebullition and stripping of the contaminants from the treatment zone. This process may lead to unintentional 'compartment transfer', whereby VOCs are transported away from the contaminated zone into overlying clean sediments and into the vadose zone. To this extent, benchtop column experiments were conducted to quantify the effect of gas generation during remediation of the common chlorinated solvent trichloroethylene (TCE/C 2 Cl 3 H). Both ISCO and enhanced bioremediation were considered as treatment methods. Results show that gas exsolution and ebullition occurs for both remediation technologies. Facilitated by ebullition, TCE was transported from the source zone into overlying clean groundwater and was subsequently released into the column headspace. For the case of enhanced bioremediation, the intermediate degradation product vinyl chloride (VC) was also stripped from the treatment zone. The concentrations measured in the headspace of the columns (TCE ∼300ppm in the ISCO column, TCE ∼500ppm and VC ∼1380ppm in the bioremediation column) indicate that substantial transfer of VOCs to the vadose zone is possible. These findings

  15. Performance Evaluation of Automated Passive Capillary Sampler for Estimating Water Drainage in the Vadose Zone

    USDA-ARS?s Scientific Manuscript database

    Passive capillary samplers (PCAPs) are widely used to monitor, measure and sample drainage water under saturated and unsaturated soil conditions in the vadose zone. The objective of this study was to evaluate the performance and accuracy of automated passive capillary sampler for estimating drainage...

  16. Aerosol Delivery for Amendment Distribution in Contaminated Vadose Zones

    NASA Astrophysics Data System (ADS)

    Hall, R. J.; Murdoch, L.; Riha, B.; Looney, B.

    2011-12-01

    Remediation of contaminated vadose zones is often hindered by an inability to effectively distribute amendments. Many amendment-based approaches have been successful in saturated formations, however, have not been widely pursued when treating contaminated unsaturated materials due to amendment distribution limitations. Aerosol delivery is a promising new approach for distributing amendments in contaminated vadose zones. Amendments are aerosolized and injected through well screens. During injection the aerosol particles are transported with the gas and deposited on the surfaces of soil grains. Resulting distributions are radially and vertically broad, which could not be achieved by injecting pure liquid-phase solutions. The objectives of this work were A) to characterize transport and deposition behaviors of aerosols; and B) to develop capabilities for predicting results of aerosol injection scenarios. Aerosol transport and deposition processes were investigated by conducting lab-scale injection experiments. These experiments involved injection of aerosols through a 2m radius, sand-filled wedge. A particle analyzer was used to measure aerosol particle distributions with time, and sand samples were taken for amendment content analysis. Predictive capabilities were obtained by constructing a numerical model capable of simulating aerosol transport and deposition in porous media. Results from tests involving vegetable oil aerosol injection show that liquid contents appropriate for remedial applications could be readily achieved throughout the sand-filled wedge. Lab-scale tests conducted with aqueous aerosols show that liquid accumulation only occurs near the point of injection. Tests were also conducted using 200 g/L salt water as the aerosolized liquid. Liquid accumulations observed during salt water tests were minimal and similar to aqueous aerosol results. However, particles were measured, and salt deposited distal to the point of injection. Differences between

  17. Experimental and modeling of the unsaturated transports of S-metolachlor and its metabolites in glaciofluvial vadose zone solids.

    PubMed

    Sidoli, Pauline; Lassabatere, Laurent; Angulo-Jaramillo, Rafael; Baran, Nicole

    2016-07-01

    The transport of pesticides to groundwater is assumed to be impacted by flow processes and geochemical interactions occurring in the vadose zone. In this study, the transport of S-metolachlor (SMOC) and its two metabolites ESA-metolachlor (MESA) and OXA-metolachlor (MOXA) in vadose zone materials of a glaciofluvial aquifer is studied at laboratory scale. Column experiments are used to study the leaching of a conservative tracer (bromide) and SMOC, MESA and MOXA under unsaturated conditions in two lithofacies, a bimodal gravel (Gcm,b) and a sand (S-x). Tracer experiments showed water fractionation into mobile and immobile compartments more pronounced in bimodal gravel columns. In both lithofacies columns, SMOC outflow is delayed (retardation factor>2) and mass balance reveals depletion (mass balance of 0.59 and 0.77 in bimodal gravel and sand, respectively). However, complete mass elution associated with retardation factors close to unity shows that there is no adsorption of MESA and MOXA in either lithofacies. SMOC transport is characterized by non-equilibrium sorption and sink term in both bimodal gravel and sand columns. Batch experiments carried out using agitation times consistent with column water residence times confirmed a time-dependence of SMOC sorption and high adsorption rates (>80%) of applied concentrations. Desorption experiments confirm the irreversibility of a major part of the SMOC adsorption onto particles, corresponding to the sink term in columns. In the bimodal gravel column, SMOC adsorption occurs mainly on reactive particles in contact with mobile water because of flow regionalization whereas in the sand column, there is pesticide diffusion to the immobile water. Such results clearly show that sorption mechanisms in the vadose zone solids below the soil are both solute and contact-time-dependent and are impacted by hydrodynamic conditions. The more rapid transport of MESA and MOXA to the aquifer would be controlled mainly by water flow

  18. Vertical Extent of 100 Area Vadose Zone Contamination of Metals at the Hanford Site

    NASA Astrophysics Data System (ADS)

    Khaleel, R.; Mehta, S.

    2012-12-01

    The 100 Area is part of the U.S. Department of Energy Hanford Site in southeastern Washington and borders the Columbia River. The primary sources of contamination in the area are associated with the operation of nine former production reactors, the last one shutting down in 1988. The area is undergoing a CERCLA remedial investigation (RI) that will provide data to support final cleanup decisions. During reactor operations, cooling water contaminated with radioactive and hazardous chemicals was discharged to both the adjacent Columbia River and infiltration cribs and trenches. Contaminated solid wastes were disposed of in burial grounds; the estimated Lead-Cadmium used as "reactor poison" and disposed of in 100 Area burial grounds is 1103 metric tons, of which up to 1059 metric tons are Lead and 44 metric tons are Cadmium. We summarize vadose zone site characterization data for the recently drilled boreholes, including the vertical distribution of concentration profiles for metals (i.e., Lead, Arsenic and Mercury) under the near neutral pH and oxygenated conditions. The deep borehole measurements targeted in the RI work plan were identified with a bias towards locating contaminants throughout the vadose zone and targeted areas at or near the waste sites; i.e., the drilling as well as the sampling was biased towards capturing contamination within the "hot spots." Unlike non-reactive contaminants such as tritium, Arsenic, Mercury and Lead are known to have a higher distribution coefficient (Kd), expected to be relatively immobile, and have a long residence time within the vadose zone. However, a number of sediment samples located close to the water table exceed the background concentrations for Lead and Arsenic. Three conceptual models are postulated to explain the deeper than expected penetration for the metals.

  19. Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

    NASA Astrophysics Data System (ADS)

    Batukaev, Abdul-Malik A.; Endovitsky, Anatoly P.; Andreev, Andrey G.; Kalinichenko, Valery P.; Minkina, Tatiana M.; Dikaev, Zaurbek S.; Mandzhieva, Saglara S.; Sushkova, Svetlana N.

    2016-03-01

    The assessment of soil and vadose zone as the drains for carbon sink and proper modeling of the effects and extremes of biogeochemical cycles in the terrestrial biosphere are the key components to understanding the carbon cycle, global climate system, and aquatic and terrestrial system uncertainties. Calcium carbonate equilibrium causes saturation of solution with CaCO3, and it determines its material composition, migration and accumulation of salts. In a solution electrically neutral ion pairs are formed: CaCO30, CaSO40, MgCO30, and MgSO40, as well as charged ion pairs CaHCO3+, MgHCO3+, NaCO3-, NaSO4-, CaOH+, and MgOH+. The calcium carbonate equilibrium algorithm, mathematical model and original software to calculate the real equilibrium forms of ions and to determine the nature of calcium carbonate balance in a solution were developed. This approach conducts the quantitative assessment of real ion forms of solution in solonetz soil and vadose zone of dry steppe taking into account the ion association at high ionic strength of saline soil solution. The concentrations of free and associated ion form were calculated according to analytical ion concentration in real solution. In the iteration procedure, the equations were used to find the following: ion material balance, a linear interpolation of equilibrium constants, a method of ionic pairs, the laws of initial concentration preservation, operating masses of equilibrium system, and the concentration constants of ion pair dissociation. The coefficient of ion association γe was determined as the ratio of ions free form to analytical content of ion γe = Cass/Can. Depending on soil and vadose zone layer, concentration and composition of solution in the ionic pair's form are 11-52 % Ca2+; 22.2-54.6 % Mg2+; 1.1-10.5 % Na+; 3.7-23.8 HCO3-, 23.3-61.6 % SO42-, and up to 85.7 % CO32-. The carbonate system of soil and vadose zone water solution helps to explain the evolution of salted soils, vadose and saturation zones, and

  20. Application of vadose-zone monitoring system for real-time characterization of leachate percolation in and under a municipal landfill.

    PubMed

    Aharoni, Imri; Siebner, Hagar; Dahan, Ofer

    2017-09-01

    Leachates from solid-waste landfills are considered a severe threat to groundwater quality. The fate of pollutants in the waste and underlying unsaturated zone is crucial for evaluating environmental risks and selecting a restoration strategy. In this study, a vadose-zone monitoring system (VMS) installed in a municipal landfill was used, for the first time, to continuously track leachates percolation dynamics and assess their chemical transformation across the entire thickness of the waste body (15m) and underlying unsaturated zone (16m) to the water table. Winter rains were found to quickly infiltrate through the waste and underlying vadose zone despite a clay cover that was implemented as part of a restoration and leachate-prevention strategy. Within the waste body, the flow pattern was controlled by preferential flow paths, which changed frequently. It is hypothesized that ongoing decomposition of the waste creates dynamic variations in the waste's physical structure and flow pattern. Water samples collected from the waste layer indicated the formation of highly polluted leachates. The chemical composition in the waste body showed extreme variability between sampling points with respect to DOC (407-31,464mg/L), BOD/COD ratios (0.07-0.55), Fe 2+ (6.8-1154mg/L), ammonium (68-2924mg/L) and heavy metal concentrations. Environmental hot spots creating concentrated, aggressive, "acid-phase" leachates still exist in the waste more than 13years after closing the landfill. However, continuous changes in the flow pattern and moisture distribution affected the creation and decay of such environments. In the underlying sandy vadose zone, some sections repeatedly exhibited stronger and faster flow characteristics than others. These local fluxes of concentrated leachates rapidly transported heavy contaminant loads toward the groundwater. However results showed evidence of continual attenuation processes in the deep vadose zone, with the anaerobic digestion of organic matter

  1. AN EXACT SOLUTION FOR THE ASSESSMENT OF NONEQUILIBRIUM SORPTION OF RADIONUCLIDES IN THE VADOSE ZONE

    EPA Science Inventory

    In a report on model evaluation, the authors ran the HYDRUS Code, among other transport codes, to evaluate the impacts of nonequilibrium sorption sites on the time-evolution of 99Tc and 90Sr through the vadose zone. Since our evaluation was based on a rather low, annual recharge...

  2. Summary of Uranium Solubility Studies in Concrete Waste Forms and Vadose Zone Environments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Golovich, Elizabeth C.; Wellman, Dawn M.; Serne, R. Jeffrey

    2011-09-30

    One of the methods being considered for safely disposing of Category 3 low-level radioactive wastes is to encase the waste in concrete. Concrete encasement would contain and isolate the waste packages from the hydrologic environment and act as an intrusion barrier. The current plan for waste isolation consists of stacking low-level waste packages on a trench floor, surrounding the stacks with reinforced steel, and encasing these packages in concrete. These concrete-encased waste stacks are expected to vary in size with maximum dimensions of 6.4 m long, 2.7 m wide, and 4 m high. The waste stacks are expected to havemore » a surrounding minimum thickness of 15 cm of concrete encasement. These concrete-encased waste packages are expected to withstand environmental exposure (solar radiation, temperature variations, and precipitation) until an interim soil cover or permanent closure cover is installed and to remain largely intact thereafter. Any failure of concrete encasement may result in water intrusion and consequent mobilization of radionuclides from the waste packages. This report presents the results of investigations elucidating the uranium mineral phases controlling the long-term fate of uranium within concrete waste forms and the solubility of these phases in concrete pore waters and alkaline, circum-neutral vadose zone environments.« less

  3. Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Szecsody, James E.; Zhong, Lirong

    Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of thismore » technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of the ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.« less

  4. Foam, a promising vehicle to deliver nanoparticles for vadose zone remediation.

    PubMed

    Shen, Xin; Zhao, Lin; Ding, Yuanzhao; Liu, Bo; Zeng, Hui; Zhong, Lirong; Li, Xiqing

    2011-02-28

    Foam delivery of remedial amendments for in situ immobilization of deep vadose zone contaminants can overcome the intrinsic problems associated with solution-based delivery, such as preferential flow and contaminant mobilization. In this work, the feasibility of using foam to deliver nanoparticles in unsaturated porous media was investigated. Carboxyl-modified polystyrene latex microspheres were used as surrogates for nanoparticles of remediation purposes. Foams generated from the solutions of six commonly available surfactants all had excellent abilities to carry the microspheres. The presence of the microspheres did not reduce the stabilities of the foams. When microsphere-laden foam was injected through the unsaturated columns, the fractions of microspheres exiting the column were much higher than that when the microsphere water suspensions were injected through the columns. The enhanced microsphere transport implies that foam delivery could significantly increase the radius of influence of injected nanoparticles of remediation purposes. Reduced tension at air-water interfaces by the surfactant and increased driving forces imparted on the microspheres at the interfaces by the flowing foam bubbles may have both contributed to the enhanced transport. Preliminary tests also demonstrated that foam can carry significant fractions of zero valent iron nanoparticles at concentrations relevant to field remediation conditions (up to 5.3 g L(-1)). As such, this study demonstrates that surfactant foam is potentially a promising vehicle to deliver nanoparticles for vadose zone remediation. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Implementation of Solute Transport in the Vadose Zone into the `HYDRUS Package for MODFLOW'

    NASA Astrophysics Data System (ADS)

    Simunek, J.; Beegum, S.; Szymkiewicz, A.; Sudheer, K. P.

    2017-12-01

    The 'HYDRUS package for MODFLOW' was developed by Seo et al. (2007) and Twarakavi et al. (2008) to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package, which is based on the HYDRUS-1D model (Šimůnek et al., 2016) simulating unsaturated water flow in the vadose zone, was incorporated into MODFLOW (Harbaugh et al., 2000) simulating saturated groundwater flow. The HYDRUS package in the coupled model can be used to represent the effects of various unsaturated zone processes, including infiltration, evaporation, root water uptake, capillary rise, and recharge in homogeneous or layered soil profiles. The coupled model is effective in addressing spatially-variable saturated-unsaturated hydrological processes at the regional scale, allowing for complex layering in the unsaturated zone, spatially and temporarily variable water fluxes at the soil surface and in the root zone, and with alternating recharge and discharge fluxes (Twarakavi et al., 2008). One of the major limitations of the coupled model was that it could not be used to simulate at the same time solute transport. However, solute transport is highly dependent on water table fluctuations due to temporal and spatial variations in groundwater recharge. This is an important concern when the coupled model is used for analyzing groundwater contamination due to transport through the unsaturated zone. The objective of this study is to integrate the solute transport model (the solute transport part of HYDRUS-1D for the unsaturated zone and MT3DMS (Zheng and Wang, 1999; Zheng, 2009) for the saturated zone) into an existing coupled water flow model. The unsaturated zone component of the coupled model can consider solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption (Šimůnek and van Genuchten, 2008

  6. Analysing the mechanisms of soil water and vapour transport in the desert vadose zone of the extremely arid region of northern China

    NASA Astrophysics Data System (ADS)

    Du, Chaoyang; Yu, Jingjie; Wang, Ping; Zhang, Yichi

    2018-03-01

    The transport of water and vapour in the desert vadose zone plays a critical role in the overall water and energy balances of near-surface environments in arid regions. However, field measurements in extremely dry environments face many difficulties and challenges, so few studies have examined water and vapour transport processes in the desert vadose zone. The main objective of this study is to analyse the mechanisms of soil water and vapour transport in the desert vadose zone (depth of ∼350 cm) by using measured and modelled data in an extremely arid environment. The field experiments are implemented in an area of the Gobi desert in northwestern China to measure the soil properties, daily soil moisture and temperature, daily water-table depth and temperature, and daily meteorological records from DOYs (Days of Year) 114-212 in 2014 (growing season). The Hydrus-1D model, which simulates the coupled transport of water, vapour and heat in the vadose zone, is employed to simulate the layered soil moisture and temperature regimes and analyse the transport processes of soil water and vapour. The measured results show that the soil water and temperatures near the land surface have visible daily fluctuations across the entire soil profile. Thermal vapour movement is the most important component of the total water flux and the soil temperature gradient is the major driving factor that affects vapour transport in the desert vadose zone. The most active water and heat exchange occurs in the upper soil layer (depths of 0-25 cm). The matric potential change from the precipitation mainly re-draws the spatio-temporal distribution of the isothermal liquid water in the soil near the land surface. The matric potential has little effect on the isothermal vapour and thermal liquid water flux. These findings offer new insights into the liquid water and vapour movement processes in the extremely arid environment.

  7. Evaluating the role of soil variability on groundwater pollution and recharge at regional scale by integrating a process-based vadose zone model in a stochastic approach

    NASA Astrophysics Data System (ADS)

    Coppola, Antonio; Comegna, Alessandro; Dragonetti, Giovanna; Lamaddalena, Nicola; Zdruli, Pandi

    2013-04-01

    Interpreting and predicting the evolution of water resources and soils at regional scale are continuing challenges for natural scientists. Examples include non-point source (NPS) pollution of soil and surface and subsurface water from agricultural chemicals and pathogens, as well as overexploitation of groundwater resources. The presence and build up of NPS pollutants may be harmful for both soil and groundwater resources. The accumulation of salts and trace elements in soils can significantly impact crop productivity, while loading of salts, nitrates, trace elements and pesticides into groundwater supplies can deteriorate a source of drinking and irrigation water. Consequently, predicting the spatial distribution and fate of NPS pollutants in soils at applicative scales is now considered crucial for maintaining the fragile balance between crop productivity and the negative environmental impacts of NPS pollutants, which is a basis of sustainable agriculture. Soil scientists and hydrologists are regularly asked to assist state agencies to understand these critical environmental issues. The most frequent inquiries are related to the development of mathematical models needed for analyzing the impacts of alternative land-use and best management use and management of soil and water resources. Different modelling solutions exist, mainly differing on the role of the vadose zone and its horizontal and vertical variability in the predictive models. The vadose zone (the region from the soil surface to the groundwater surface) is a complex physical, chemical and biological ecosystem that controls the passage of NPS pollutants from the soil surface where they have been deposited or accumulated due to agricultural activities, to groundwater. Physically based distributed hydrological models require the internal variability of the vadose zone be explored at a variety of scales. The equations describing fluxes and storage of water and solutes in the unsaturated zone used in these

  8. Preferential Flow and Transport of Cryptosporidium Parvum Oocysts Through Vadose Zone: Experiments and Modeling

    NASA Astrophysics Data System (ADS)

    Darnault, C. J.; Darnault, C. J.; Garnier, P.; Kim, Y.; Oveson, K.; Jenkins, M.; Ghiorse, W.; Baveye, P.; Parlange, J.; Steenhuis, T.

    2001-12-01

    Oocysts of the protozoan Cryptosporidium parvum, when they contaminate drinking water supplies, can cause outbreaks of Cryptosporidiosis, a common waterborne disease. Of the different pathways by which oocysts can wind up in drinking water, one has received very little attention to date; because soils are often considered to be perfect filters, the transport of oocysts through the subsoil to groundwater by preferential flow is generally ignored. To evaluate its significance, three set of laboratory experiments investigated transport of oocysts through vadose zone. Experiment set I was carried out in a vertical 50 cm-long column filled with silica sand, under conditions known to foster fingered flow. Experiment set II investigates the effect of gas-water interfaces by modifying the hydrodynamical conditions in the sand columns with water-repellent sand barriers. Experiment III involved undisturbed soil columns subjected to macropores flow. The sand and soil columns were subjected to artificial rainfall and were allowed to reach steady-state. At that point, feces of contaminated calves were applied at the surface, along with a known amount of KCl to serve as tracer, and rainfall was continued at the same rate. The breakthrough of oocysts and Cl-, monitored in the effluent, demonstrate the importance of preferential flow - fingered flow and macropore flow - on the transport of oocysts through vadose zone. Peak oocyst concentrations were not appreciably delayed, compared to Cl-, and in some cases, occurred even before the Cl- peak. However, the numbers of oocysts present in the effluents were still orders of magnitude higher than the 5 to 10 oocysts per liter that are considerable sufficient to cause cryptosporidiosis in healthy adults. The transport of oocysts was simulated based on a partitioning the soil profile in both a distribution zone and a preferential zone, In particular, the model simulates accurately the markedly asymmetric breakthrough patterns, and the

  9. An isotopic view of water and nitrate transport through the vadose zone in Oregon's southern Willamette Valley's Groundwater Management Area

    NASA Astrophysics Data System (ADS)

    Brooks, J. R.; Pearlstein, S.; Hutchins, S.; Faulkner, B. R.; Rugh, W.; Willard, K.; Coulombe, R.; Compton, J.

    2017-12-01

    Groundwater nitrate contamination affects thousands of households in Oregon's southern Willamette Valley and many more across the USA. The southern Willamette Valley Groundwater Management Area (GWMA) was established in 2004 due to nitrate levels in the groundwater exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen (N) inputs to the GWMA comes from agricultural fertilizers, and thus efforts to reduce N inputs to groundwater are focused upon improving N management. However, the effectiveness of these improvements on groundwater quality is unclear because of the complexity of nutrient transport through the vadose zone and long groundwater residence times. Our objective was to focus on vadose zone transport and understand the dynamics and timing of N and water movement below the rooting zone in relation to N management and water inputs. Stable isotopes are a powerful tool for tracking water movement, and understanding N transformations. In partnership with local farmers and state agencies, we established lysimeters and groundwater wells in multiple agricultural fields in the GWMA, and have monitored nitrate, nitrate isotopes, and water isotopes weekly for multiple years. Our results indicate that vadose zone transport is highly complex, and the residence time of water collected in lysimeters was much longer than expected. While input precipitation water isotopes were highly variable over time, lysimeter water isotopes were surprisingly consistent, more closely resembling long-term precipitation isotope means rather than recent precipitation isotopic signatures. However, some particularly large precipitation events with unique isotopic signatures revealed high spatial variability in transport, with some lysimeters showing greater proportions of recent precipitation inputs than others. In one installation where we have groundwater wells and lysimeters at multiple depths, nitrate/nitrite concentrations decreased with depth. N concentrations

  10. The role of fluid mobility in the development of shale weathering profiles: Direct observations from a vadose zone monitoring system

    NASA Astrophysics Data System (ADS)

    Druhan, J. L.; Wang, J.; Cargill, S.; Murphy, C.; Tune, A. K.; Dietrich, W. E.; Rempe, D.

    2017-12-01

    Extensive effort has focused on resolving the contribution of weathering reactions to the transfer of mass over scales ranging from individual hillslope weathering profiles, across local watersheds, to continental drainage networks. A persistent limitation in quantifying these fluxes is the variability in fluid flowpaths through the subsurface, which may alter the extent of chemical weathering relative to that expected from idealized homogenous conditions. In the past decade, the consequence of fluid travel time on solute flux has been recognized as a key complexity in the interpretation of solute concentrations, particularly in upland watersheds characterized by fracture flowpaths, as is typical of shale-dominated landscapes. Though recent studies have suggested a variety of models for solute generation in such dual (matrix and fracture flow) domain systems, a central impediment to advancing prediction is the lack of direct observations. Here, we report solute chemistry as a function of depth across an 18 m thick vadose zone of weathered argillite (shale) in the Eel River Critical Zone Observatory (ERCZO) using novel sub-horizontal distributed samplers (Vadose Zone Monitoring System). We contrast a year of major and trace ion chemistry obtained from water samples collected approximately biweekly using two complementary sampling systems, one applying active pressure to extract matrix-bound pore fluid, and the other using a passive collection method to extract freely draining water. Precipitation falling during the winter rainy season passes through this vadose zone, causing increased rock moisture that is subsequently depleted by transpiring trees. Solute concentrations reflect these seasonal changes, and, surprisingly, normalized ion ratios span the full range of values reported for the world's largest rivers. Notably, for some major cations, freely draining water is consistently less concentrated than matrix-bound water, and the composition of vadose zone water

  11. Stochastic inversion of time-lapse geophysical data to characterize the vadose zone at the Arrenaes field site (Denmark)

    NASA Astrophysics Data System (ADS)

    Marie, S.; Irving, J. D.; Looms, M. C.; Nielsen, L.; Holliger, K.

    2011-12-01

    Geophysical methods such as ground-penetrating radar (GPR) can provide valuable information on the hydrological properties of the vadose zone. In particular, there is evidence to suggest that the stochastic inversion of such data may allow for significant reductions in uncertainty regarding subsurface van-Genuchten-Mualem (VGM) parameters, which characterize unsaturated hydrodynamic behaviour as defined by the combination of the water retention and hydraulic conductivity functions. A significant challenge associated with the use of geophysical methods in a hydrological context is that they generally exhibit an indirect and/or weak sensitivity to the hydraulic parameters of interest. A novel and increasingly popular means of addressing this issue involves the acquisition of geophysical data in a time-lapse fashion while changes occur in the hydrological condition of the probed subsurface region. Another significant challenge when attempting to use geophysical data for the estimation of subsurface hydrological properties is the inherent non-linearity and non-uniqueness of the corresponding inverse problems. Stochastic inversion approaches have the advantage of providing a comprehensive exploration of the model space, which makes them ideally suited for addressing such issues. In this work, we present the stochastic inversion of time-lapse zero-offset-profile (ZOP) crosshole GPR traveltime data, collected during a forced infiltration experiment at the Arreneas field site in Denmark, in order to estimate subsurface VGM parameters and their corresponding uncertainties. We do this using a Bayesian Markov-chain-Monte-Carlo (MCMC) inversion approach. We find that the Bayesian-MCMC methodology indeed allows for a substantial refinement in the inferred posterior parameter distributions of the VGM parameters as compared to the corresponding priors. To further understand the potential impact on capturing the underlying hydrological behaviour, we also explore how the posterior

  12. Engineering report single-shell tank farms interim measures to limit infiltration through the vadose zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    HAASS, C.C.

    1999-10-14

    Identifies, evaluates and recommends interim measures for reducing or eliminating water sources and preferential pathways within the vadose zone of the single-shell tank farms. Features studied: surface water infiltration and leaking water lines that provide recharge moisture, and wells that could provide pathways for contaminant migration. An extensive data base, maps, recommended mitigations, and rough order of magnitude costs are included.

  13. Vadose zone processes delay groundwater nitrate reduction response to BMP implementation as observed in paired cultivated vs. uncultivated potato rotation fields

    NASA Astrophysics Data System (ADS)

    Jiang, Y.; Nyiraneza, J.; Murray, B. J.; Chapman, S.; Malenica, A.; Parker, B.

    2017-12-01

    Nitrate leaching from crop production contributes to groundwater contamination and subsequent eutrophication of the receiving surface water. A study was conducted in a 7-ha potato-grain-forages rotation field in Prince Edward Island (PEI), Canada during 2011-2016 to link potato rotation practices and groundwater quality. The field consists of fine sandy loam soil and is underlain by 7-9 m of glacial till, which overlies the regional fractured ;red-bed; sandstone aquifer. The water table is generally located in overburden close to the bedrock interface. Field treatments included one field zone taken out of production in 2011 with the remaining zones kept under a conventional potato rotation. Agronomy data including crop tissue, soil, and tile-drain water quality were collected. Hydrogeology data including multilevel monitoring of groundwater nitrate and hydraulic head and data from rock coring for nitrate distribution in overburden and bedrock matrix were also collected. A significant amount of nitrate leached below the soil profile after potato plant kill (referred to as topkill) in 2011, most of it from fertilizer N. A high level of nitrate was also detected in the till vadose zone through coring in December 2012 and through multilevel groundwater sampling from January to May 2014 in both cultivated and uncultivated field zones. Groundwater nitrate concentrations increased for about 2.5 years after the overlying potato field was removed from production. Pressure-driven uniform flow processes dominate water and nitrate transport in the vadose zone, producing an apparently instant water table response but a delayed groundwater quality response to nitrate leaching events. These data suggest that the uniform flow dominated vadose zone in agricultural landscapes can cause the accumulation of a significant amount of nitrate originated from previous farming activities, and the long travel time of this legacy nitrate in the vadose zone can result in substantially delayed

  14. Are faults preferential flow paths through semiarid and arid vadose zones?

    NASA Astrophysics Data System (ADS)

    Sigda, John M.; Wilson, John L.

    2003-08-01

    Numerous faults crosscut the poorly lithified, basin-fill sands found in New Mexico's Rio Grande rift and in other extensional regimes. The deformational processes that created these faults sharply reduced both fault porosity and fault saturated hydraulic conductivity by altering grains and pores, particularly in structures referred to as deformation bands. The resulting pore distribution changes, which create barriers to saturated flow, should enhance fault unsaturated flow relative to parent sand under the relatively dry conditions of the semiarid southwest. We report the first measurements of unsaturated hydraulic properties for undisturbed fault materials, using samples from a small-displacement normal fault and parent sands in the Bosque del Apache Wildlife Refuge, central New Mexico. Fault samples were taken from a narrow zone of deformation bands. The unsaturated flow apparatus (UFA) centrifuge system was used to measure both relative permeability and moisture retention curves. We compared these relations and fitted hydraulic conductivity-matric potential models to test whether the fault has significantly different unsaturated hydraulic properties than its parent sand. Saturated conductivity is 3 orders of magnitude less in the fault than the undeformed sand. As matric potential decreases from 0 to -200 cm, unsaturated conductivity decreases roughly 1 order of magnitude in the fault but 5-6 orders of magnitude in undeformed sands. Fault conductivity is greater by 2-6 orders of magnitude at matric potentials between -200 and -1000 cm, which are typical potentials for semiarid and arid vadose zones. Fault deformation bands have much higher air-entry matric potential values than parent sands and remain close to saturation well after the parent sands have begun to approach residual moisture content. Under steady state, one-dimensional, gravity-driven flow conditions, moisture transport and solute advection is 102-106 times larger in the fault material than

  15. Vadose zone dynamics governing snowmelt infiltration and groundwater recharge in a seasonally frozen, semi-arid landscape

    NASA Astrophysics Data System (ADS)

    Mohammed, A.; LeBlanc, F.; Cey, E. E.; Hayashi, M.

    2016-12-01

    Snowmelt infiltration and vadose zone fluxes in seasonally frozen soils are strongly affected by meteorological and soil moisture dynamics occurring during the preceding fall and winter, and complex processes controlling soil hydraulic and thermal regimes. In order to predict their effects on hydrologic processes such as run-off generation, groundwater recharge and plant-water availability in cold regions, an improved understanding of the mechanisms governing coupled water and heat fluxes in the unsaturated zone is needed. Field and laboratory studies were conducted to investigate snowmelt infiltration and groundwater recharge through partially frozen ground over a range of climate and soil conditions in the Canadian Prairies. Meteorological and subsurface field measurements at three sites were combined with laboratory infiltration experiments on frozen undisturbed soil-columns to provide insights into the hydraulic and thermal processes governing water movement. Analysis reveals that antecedent moisture content and thermal profiles both strongly affect subsurface dynamics during infiltration of snowmelt. Preferential flow is also a critical parameter, as both thermal and hydraulic responses were observed at depth prior to complete ground thaw in the field; as well as drainage outflow from the frozen soil column experiments under certain conditions. Results indicate that both diffuse (matrix) and preferential (macropore) flow play significant roles in the infiltration and redistribution of snowmelt water under frozen soil conditions, and shallow groundwater recharge. This study highlights the critical subsurface factors and processes that control infiltration and groundwater recharge in these seasonally frozen landscapes.

  16. Natural analogues for processes affecting disposal of high-level radioactive waste in the vadose zone

    NASA Astrophysics Data System (ADS)

    Stuckless, J. S.

    2003-04-01

    Natural analogues can contribute to understanding and predicting the performance of subsystems and processes affecting a mined geologic repository for high-level radioactive waste in several ways. Most importantly, analogues provide tests for various aspects of systems of a repository at dimensional scales and time spans that cannot be attained by experimental study. In addition, they provide a means for the general public to judge the predicted performance of a potential high-level nuclear waste repository in familiar terms such that the average person can assess the anticipated long-term performance and other scientific conclusions. Hydrologists working on the Yucca Mountain Project (currently the U.S. Department of Energy's Office of Repository Development) have modeled the flow of water through the vadose zone at Yucca Mountain, Nevada and particularly the interaction of vadose-zone water with mined openings. Analogues from both natural and anthropogenic examples confirm the prediction that most of the water moving through the vadose zone will move through the host rock and around tunnels. This can be seen both quantitatively where direct comparison between seepage and net infiltration has been made and qualitatively by the excellent degree of preservation of archaeologic artifacts in underground openings. The latter include Paleolithic cave paintings in southwestern Europe, murals and artifacts in Egyptian tombs, painted subterranean Buddhist temples in India and China, and painted underground churches in Cappadocia, Turkey. Natural analogues also suggest that this diversion mechanism is more effective in porous media than in fractured media. Observations from natural analogues are also consistent with the modeled decrease in the percentage of infiltration that becomes seepage with a decrease in amount of infiltration. Finally, analogues, such as tombs that have ben partially filled by mud flows, suggest that the same capillary forces that keep water in the

  17. Observation of flow processes in the vadose zone using ERT on different space and time scales: results, obstacles, and suggestions

    NASA Astrophysics Data System (ADS)

    Noell, Ursula; Ganz, Christina; Lamparter, Axel; Duijnisveld, Wilhelmus; Bachmann, Jörg

    2013-04-01

    Electrical resistivity tomography (ERT) observes the flow processes in the vadose zone indirectly. ERT has been used to estimate water flow in different soil types and under different flow conditions using active experiments or monitoring the natural process in many cases. Our experiments in sand and loess soil connected ERT with local soil probing using TDR devices and tensiometers in order to proof the reliability of the ERT inversion results in terms of infiltration velocity. Additionally, a colour tracer was used and sections through the infiltration zones were excavated in order to compare the shape of the dye -stained infiltration zone with the results of the ERT inversion. The data revealed the complicated infiltration pattern with a higher transport velocity in sand and a different shape than expected by classical soil hydraulic models. These results indicate the need for independent observations in order to correctly assess the water storage in the vadose zone with its hydrological consequences, the groundwater recharge and the contamination risk caused by rapid movement of water. ERT can be used for this purpose on different spatial- and time scales but for reliable results various obstacles need to be dealt with. Firstly, the ambiguity of the resistivity because soil resistivity depends on both, soil water content and electrical soil/water conductivity. This obstacle is less severe when the infiltration velocity is investigated, because then only the first onset of resistivity change is interpreted as the water arrival time. Our results show that the arrival of the water front as well as the final infiltration depth can be reliably detected. In contrast, this obstacle is very severe when the amount of water stored is observed using conductive tracer. The problem is not critical during a passive experiment when the natural rain fall and the waters fate through the vadose zone is monitored. The second obstacle is the limited resolution of ERT which

  18. SCREENING MODEL FOR NONAQUEOUS PHASE-LIQUID TRANSPORT IN THE VADOSE ZONE USING GREEN-AMPT AND KINEMATIC WAVE THEORY

    EPA Science Inventory

    In this paper, a screening model for flow of a nonaqueous phase liquid (NAPL) and associated chemical transport in the vadose zone is developed. he model is based on kinematic approximation of the governing equations for both the NAPL and a partitionable chemical constituent. he ...

  19. PRODUCTION AND TRANSPORT OF CARBON DIOXIDE IN A CONTAMINATED VADOSE ZONE: A STABLE AND RADIOACTIVE CARBON ISOTOPE STUDY

    EPA Science Inventory

    Analyses of soil gas compositions and stable and radioactive carbon isotopes in the vadose zone above an alluvial aquifer were conducted at an organic solvent disposal site in southeast Phoenix, AZ. The study investigated the source and movement of carbon dioxide above a plume of...

  20. Quantifying Seasonal Dynamic Water Storage in a Fractured Bedrock Vadose Zone With Borehole Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Schmidt, L.; Minton, B.; Soto-Kerans, N.; Rempe, D.; Heidari, Z.

    2017-12-01

    In many uplands landscapes, water is transiently stored in the weathered and fractured bedrock that underlies soils. The timing and spatial pattern of this "rock moisture" has strong implications for ecological and biogeochemical processes that influence global cycling of water and solutes. However, available technologies for direct monitoring of rock moisture are limited. Here, we quantify temporal and spatial changes in rock moisture at the field scale across thick (up to 20 m) fractured vadose zone profiles using a novel narrow diameter borehole nuclear magnetic resonance system (BNMR). Successive BNMR surveys were performed using the Vista Clara Inc. Dart system in a network of boreholes within two steep, intensively hydrologically monitored hillslopes associated with the Eel River Critical Zone Observatory (ERCZO) in Northern California. BNMR data showed agreement with estimates of the temporal and spatial pattern of rock moisture depletion over the dry season via downhole neutron and gamma density surveys, as well as permanently installed continuous time domain reflectometry. Observable shifts in the BNMR-derived T2 distribution over time provide a direct measure of changes in the amount of water held within different pore sizes (large vs. small) in fractured rock. Analysis of both BNMR and laboratory-scale NMR (using a 2MHz benchtop NMR spectrometer) measurements of ERCZO core samples at variable saturation suggest that rock moisture changes associated with summer depletion occur within both large (fracture) and small (matrix) pore sizes. Collectively, our multi-method field- and laboratory- scale measurements highlight the potential for BNMR to improve quantification of rock moisture storage for better understanding of the biogeochemical and ecohydrological implications of rock moisture circulation in the Critical Zone.

  1. Delivery and Establishing Slow Release Carbon Source to the Hanford Vadose Zone Using Colloidal Silica Suspension Injection and Subsequent Gelation - Laboratory Study

    NASA Astrophysics Data System (ADS)

    Zhong, L.; Lee, M. H.; Lee, B.; Yang, S.

    2016-12-01

    Delivery of nutrient to and establish a slow release carbon source in the vadose zone and capillary fringe zone is essential for setting up of a long-lasting bioremediation of contaminations in those zones. Conventional solution-based injection and infiltration approaches are facing challenges to achieve the delivery and remedial goals. Aqueous silica suspensions undergo a delayed gelation process under favorite geochemical conditions. The delay in gelation provides a time window for the injection of the suspension into the subsurface; and the gelation of the amendment-silica suspension enables the amendment-laden gel to stay in the target zone and slowly release the constituents for contaminant remediation. This approach can potentially be applied to deliver bio-nutrients to the vadose zone and capillary fringe zone for enhanced bioremediation and achieve remedial goals. This research was conducted to demonstrate delayed gelation of colloidal silica suspensions when carbon sources were added and to prove the gelation occurs in sediments under vadose conditions. Sodium lactate, vegetable oil, ethanol, and molasses were tested as the examples of carbon source (or nutrient) amendments. The rheological properties of the silica suspensions during the gelation were characterized. The influence of silica, salinity, nutrient concentrations, and the type of nutrients was studied. The kinetics of nutrient release from silica-nutrient gel was quantified using molasses as the example, and the influence of suspension gelation time was evaluated. The injection behavior of the suspensions was investigated by monitoring their viscosity changes and the injection pressures when the suspensions were delivered into sediment columns.

  2. A vadose zone water fluxmeter with divergence control

    NASA Astrophysics Data System (ADS)

    Gee, G. W.; Ward, A. L.; Caldwell, T. G.; Ritter, J. C.

    2002-08-01

    Unsaturated water flux densities are needed to quantify water and contaminant transfer within the vadose zone. However, water flux densities are seldom measured directly and often are predicted with uncertainties of an order or magnitude or more. A water fluxmeter was designed, constructed, and tested to directly measure drainage fluxes in field soils. The fluxmeter was designed to minimize divergence. It concentrates flow into a narrow sensing region filled with a fiberglass wick. The wick applies suction, proportional to its length, and passively drains the meter. The meter can be installed in an augured borehole at almost any depth below the root zone. Water flux through the meter is measured with a self-calibrating tipping bucket, with a sensitivity of ~4 mL tip-1. For our meter this is equivalent to detection limit of ~0.1 mm. Passive-wick devices previously have not properly corrected for flow divergence. Laboratory measurements supported predictions of a two-dimensional (2-D) numerical model, which showed that control of the collector height H and knowledge of soil hydraulic properties are required for improving divergence control, particularly at fluxes below 1000 mm yr-1. The water fluxmeter is simple in concept, is inexpensive, and has the capability of providing continuous and reliable monitoring of unsaturated water fluxes ranging from less than 1 mm yr-1 to more than 1000 mm yr-1.

  3. Enhanced biogeochemical cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone

    PubMed Central

    Hansen, David J.; McGuire, Jennifer T.; Mohanty, Binayak P.

    2013-01-01

    Biogeochemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events respectively. In-situ collocated probes measured soil water content, matric potential, and Eh while water samples collected from the same locations were analyzed for Br−, Cl−, NO3−, SO42−, NH4+, Fe2+, and total sulfide. Compared to homogenous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced biogeochemical cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron and sulfate reducing bacteria showed 1-2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface; the presence of which, likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying coupled hydrologic-biogeochemical processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. Findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation and/or slow the rate of transport of contaminants. PMID:22031578

  4. Groundwater response to leakage of surface water through a thick vadose zone in the middle reaches area of Heihe River Basin, in China

    NASA Astrophysics Data System (ADS)

    Wang, X.-S.; Ma, M.-G.; Li, X.; Zhao, J.; Dong, P.; Zhou, J.

    2009-12-01

    The behavior of groundwater response to leakage of surface water in the middle reaches area of Heihe River Basin is significantly influenced by a thick vadose zone. The variation of groundwater level is a result of two recharge events corresponding to leakage of Heihe River and irrigation water with different delay time. A nonlinear leakage model is developed to calculate the monthly leakage of Heihe River in considering changes of streamflow, river stage and agricultural water utilization. Numerical modeling of variable saturated flow is carried out to investigate the general behaviors of leakage-recharge conversion through a thick vadose zone. It is found that the variable recharge can be approximated by simple reservoir models for both leakage under a river and leakage under an irrigation district but with different delay-time and recession coefficient. A triple-reservoir model of relationship between surface water, vadose zone and groundwater is developed. It reproduces the in situ water table movement during 1989-2006 with variable streamflow of Heihe River and agricultural water utilization. The model is applied to interpret groundwater dynamics during 2007-2008 that observed in the Watershed Airborne Telemetry Experimental Research (WATER).

  5. Groundwater response to leakage of surface water through a thick vadose zone in the middle reaches area of Heihe River Basin, in China

    NASA Astrophysics Data System (ADS)

    Wang, X.-S.; Ma, M.-G.; Li, X.; Zhao, J.; Dong, P.; Zhou, J.

    2010-04-01

    The behavior of groundwater response to leakage of surface water in the middle reaches area of Heihe River Basin is significantly influenced by a thick vadose zone. The groundwater regime is a result of two recharge events due to leakage of Heihe River and irrigation water with different delay time. A nonlinear leakage model is developed to calculate the monthly leakage of Heihe River in considering changes of streamflow, river stage and agricultural water utilization. Numerical modeling of variable saturated flow is carried out to investigate the general behaviors of leakage-recharge conversion through a thick vadose zone. It is found that the recharge pattern can be approximated by simple reservoir models of leakages under a river and under an irrigation district with different delay-time and recession coefficient. A triple-reservoir model of relationship between surface water, vadose zone and groundwater is developed. It reproduces the groundwater regime during 1989-2006 with variable streamflow of Heihe River and agricultural water utilization. The model is applied to interpret changes of groundwater level during 2007-2008 that observed in the Watershed Airborne Telemetry Experimental Research (WATER).

  6. Development and assessment of an efficient vadose zone module solving the 1D Richards' equation and including root extraction by plants

    NASA Astrophysics Data System (ADS)

    Varado, N.; Braud, I.; Ross, P. J.

    2006-05-01

    From the non iterative numerical method proposed by [Ross, P.J., 2003. Modeling soil water and solute transport—fast, simplified numerical solutions. Agronomy Journal 95, 1352-1361] for solving the 1D Richards' equation, an unsaturated zone module for large scale hydrological model is developed by the inclusion of a root extraction module and a formulation of interception. Two root water uptake modules, first proposed by [Lai, C.-T. and Katul, G., 2000. The dynamic role of rott-water uptake in coupling potential to actual transpiration. Adv. Water Res. 23: 427-439; Li, K.Y., De Jong, R. and Boisvert, J.B., 2001. An exponential root-water-uptake model with water stress compensation. J. Hydrol. 252: 189-204], were included as the sink term in the Richards' equation. They express root extraction as a linear function of potential transpiration and take into account water stress and compensation mechanism allowing water to be extracted in wetter layers. The vadose zone module is tested in a systematic way with synthetic data sets covering a wide range of soil characteristics, climate forcing, and vegetation cover. A detailed SVAT model providing an accurate solution of the coupled heat and water transfer in the soil and the surface energy balance is used as a reference. The accuracy of the numerical solution using only the SVAT soil module, and the loss of accuracy when using a potential evapotranspiration instead of solving the energy budget are both investigated. The vadose zone module is very accurate with errors of less than a few percent for cumulative transpiration. Soil evaporation is less accurately simulated as it leads to a systematic underestimation of soil evaporation amounts. The [Lai, C.-T. and Katul, G., 2000. The dynamic role of rott-water uptake in coupling potential to actual transpiration. Adv. Water Res. 23: 427-439] module is not adapted for sandy soils, due to a weakness in the compensation term formulation. When using a potential

  7. Vadose Zone Monitoring of Dairy Green Water Lagoons using Soil Solution Samplers.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brainard, James R.; Coplen, Amy K

    2005-11-01

    Over the last decade, dairy farms in New Mexico have become an important component to the economy of many rural ranching and farming communities. Dairy operations are water intensive and use groundwater that otherwise would be used for irrigation purposes. Most dairies reuse their process/green water three times and utilize lined lagoons for temporary storage of green water. Leakage of water from lagoons can pose a risk to groundwater quality. Groundwater resource protection infrastructures at dairies are regulated by the New Mexico Environment Department which currently relies on monitoring wells installed in the saturated zone for detecting leakage of wastemore » water lagoon liners. Here we present a proposal to monitor the unsaturated zone beneath the lagoons with soil water solution samplers to provide early detection of leaking liners. Early detection of leaking liners along with rapid repair can minimize contamination of aquifers and reduce dairy liability for aquifer remediation. Additionally, acceptance of vadose zone monitoring as a NMED requirement over saturated zone monitoring would very likely significantly reduce dairy startup and expansion costs. Acknowledgment Funding for this project was provided by the Sandia National Laboratories Small Business Assistance Program« less

  8. Transport Studies at the Vadose Zone Research Park, Idaho National Engineering and Environmental Laboratory: Results of Initial Tests

    NASA Astrophysics Data System (ADS)

    Roback, R. C.; Jones, C. L.; Hull, L. C.; McLing, T. L.; Baker, K. E.; Abdel-Fattah, A. I.; Adams, J. D.; Nichols, E. M.

    2003-12-01

    The Vadose Zone Research Park (VZRP) provides a unique opportunity to investigate flow and transport in a thick, fractured and layered vadose zone. The VZRP includes two newly constructed percolation ponds each approximately 160000 square ft in area, which receive roughly 1.0 to 1.5 million gallons/day of uncontaminated process water. Monitoring wells and instrumented boreholes surround the percolation ponds. These are distributed in nested sets that allow continuous monitoring and sample collection along two important hydrologic contacts; one located at roughly 60' bls along a contact between alluvium and basalt and the other at 125' bls, along a sedimentary interbed in basalt. Both of these contacts support perched water zones. Hydraulic data have been collected nearly continuously since the first use of the percolation ponds in August 2002. Samples for geochemical studies were also collected during the first few weeks of discharge to the south pond to observe geochemical trends during initial wetting of the subsurface. During the summer of 2003, two tracer tests were performed. The first test consisted of injecting a conservative tracer (2,4,5-trifluorobenzoic acid) into the south pond, which had been receiving water for almost 10 months prior and for which hydraulic data indicated a steady state hydraulic system. The second tracer test was conducted in the north pond and consisted of simultaneous injection of two conservative tracers with different diffusion coefficients (2,4-difluorobenzoic acid, and Br- ion). Tracer injection coincided with the switching of water from the south to the north pond, which had been dry for 10 months prior. Thus, this test afforded us the opportunity to evaluate transport behavior in a relatively dry vadose zone, and to compare this to observed transport behavior under the earlier steady state, more saturated flow condition. Results from the first tracer test show tracer breakthrough in a shallow well, close to the south pond

  9. SCREENING MODEL FOR NONAQUEOUS PHASE LIQUID TRANS- PORT IN THE VADOSE ZONE USING GREEN-AMPT AND KINEMATIC WAVE THEORY

    EPA Science Inventory

    In this paper, a screening model for flow of a nonaqueous phase liquid (NAPL) and associated chemical transport in the vadose zone is developed. The model is based on kinematic approximation of the governing equations for both the NAPL and a partitionable chemical constituent. Th...

  10. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA

    2008-05-12

    There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of themore » most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H{sub 2}S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H{sub 2}S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H{sub 2}S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H{sub 2}S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The

  11. A vadose zone water fluxmeter with divergence control

    USGS Publications Warehouse

    Gee, G.W.; Ward, A.L.; Caldwell, T.G.; Ritter, J.C.

    2002-01-01

    Unsaturated water flux densities are needed to quantify water and contaminant transfer within the vadose zone. However, water flux densities are seldom measured directly and often are predicted with uncertainties of an order or magnitude or more. A water fluxmeter was designed, constructed, and tested to directly measure drainage fluxes in field soils. The fluxmeter was designed to minimize divergence. It concentrates flow into a narrow sensing region filled with a fiberglass wick. The wick applies suction, proportional to its length, and passively drains the meter. The meter can be installed in an augured borehole at almost any depth below the root zone. Water flux through the meter is measured with a self‐calibrating tipping bucket, with a sensitivity of ∼4 mL tip−1. For our meter this is equivalent to detection limit of ∼0.1 mm. Passive‐wick devices previously have not properly corrected for flow divergence. Laboratory measurements supported predictions of a two‐dimensional (2‐D) numerical model, which showed that control of the collector height H and knowledge of soil hydraulic properties are required for improving divergence control, particularly at fluxes below 1000 mm yr−1. The water fluxmeter is simple in concept, is inexpensive, and has the capability of providing continuous and reliable monitoring of unsaturated water fluxes ranging from less than 1 mm yr−1 to more than 1000 mm yr−1.

  12. An alternative tensiometer design for deep vadose zone monitoring

    NASA Astrophysics Data System (ADS)

    Moradi, A. B.; Kandelous, M. M.; Hopmans, J. W.

    2015-12-01

    The conventional tensiometer is among the most accurate devices for soil water matric potential measurements, as well as for estimations of soil water flux from soil water potential gradients. Uncertainties associated with conventional tensiometers such as caused by ambient temperature effects and the draining of the tensiometer tube, as well as their limitation for deep soil monitoring has prevented their widespread use for vadose zone monitoring, despite their superior accuracy, in general. We introduce an alternative tensiometer design that offers the accuracy of the conventional tensiometer, while minimizing afore-mentioned uncertainties and limitations. The proposed alternative tensiometer largely eliminates temperature-induced diurnal fluctuations and uncertainties associated with the draining of the tensiometer tube, and removes the limitation in installation depth. In addition, the manufacturing costs of this alternative tensiometer design is close to that of the conventional tensiometer, while it is especially suited for monitoring of soil water potential gradients as required for soil water flux measurements.

  13. Modeling Subsurface Hydrology in Floodplains

    NASA Astrophysics Data System (ADS)

    Evans, Cristina M.; Dritschel, David G.; Singer, Michael B.

    2018-03-01

    Soil-moisture patterns in floodplains are highly dynamic, owing to the complex relationships between soil properties, climatic conditions at the surface, and the position of the water table. Given this complexity, along with climate change scenarios in many regions, there is a need for a model to investigate the implications of different conditions on water availability to riparian vegetation. We present a model, HaughFlow, which is able to predict coupled water movement in the vadose and phreatic zones of hydraulically connected floodplains. Model output was calibrated and evaluated at six sites in Australia to identify key patterns in subsurface hydrology. This study identifies the importance of the capillary fringe in vadose zone hydrology due to its water storage capacity and creation of conductive pathways. Following peaks in water table elevation, water can be stored in the capillary fringe for up to months (depending on the soil properties). This water can provide a critical resource for vegetation that is unable to access the water table. When water table peaks coincide with heavy rainfall events, the capillary fringe can support saturation of the entire soil profile. HaughFlow is used to investigate the water availability to riparian vegetation, producing daily output of water content in the soil over decadal time periods within different depth ranges. These outputs can be summarized to support scientific investigations of plant-water relations, as well as in management applications.

  14. THE DOE COMPLEX-WIDE VADOSE ZONE SCIENCE AND TECHNOLOGY ROADMAP: CHARACTERIZATION MODELING AND SIMULATION OF SUBSURFACE CONTAMINANT FATE AND TRANSPORT

    EPA Science Inventory

    The Idaho National Engineering & Environmental Lab (INEEL) was charged by DOE EM to develop a complex-wide science and technology roadmap for the characterization, modeling and simulation of the fate and transport of contamination in the vadose zone. Various types of hazardous, r...

  15. Coupled effects of solution chemistry and hydrodynamics on the mobility and transport of quantum dot nanomaterials in the Vadose Zone

    USDA-ARS?s Scientific Manuscript database

    To investigate the coupled effects of solution chemistry and vadose zone processes on the mobility of quantum dot (QD) nanoparticles, laboratory scale transport experiments were performed. The complex coupled effects of ionic strength, size of QD aggregates, surface tension, contact angle, infiltrat...

  16. Managed aquifer recharge of treated wastewater: water quality changes resulting from infiltration through the vadose zone.

    PubMed

    Bekele, Elise; Toze, Simon; Patterson, Bradley; Higginson, Simon

    2011-11-01

    Secondary treated wastewater was infiltrated through a 9 m-thick calcareous vadose zone during a 39 month managed aquifer recharge (MAR) field trial to determine potential improvements in the recycled water quality. The water quality improvements of the recycled water were based on changes in the chemistry and microbiology of (i) the recycled water prior to infiltration relative to (ii) groundwater immediately down-gradient from the infiltration gallery. Changes in the average concentrations of several constituents in the recycled water were identified with reductions of 30% for phosphorous, 66% for fluoride, 62% for iron and 51% for total organic carbon when the secondary treated wastewater was infiltrated at an applied rate of 17.5 L per minute with a residence time of approximately four days in the vadose zone and less than two days in the aquifer. Reductions were also noted for oxazepam and temazepam among the pharmaceuticals tested and for a range of microbial pathogens, but reductions were harder to quantify as their magnitudes varied over time. Total nitrogen and carbamazepine persisted in groundwater down-gradient from the infiltration galleries. Infiltration does potentially offer a range of water quality improvements over direct injection to the water table without passage through the unsaturated zone; however, additional treatment options for the non-potable water may still need to be considered, depending on the receiving environment or the end use of the recovered water. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  17. Understanding the rapidity of subsurface storm flow response from a fracture-oriented shallow vadose through a new perspective

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Zhao, Pei; Liang, Chuan; Li, Tianyang; Zhou, Baojia

    2017-01-01

    Velocity and celerity in hydrologic systems are controlled by different mechanisms. Efforts were made through joint sample collection and the use of hydrographs and tracers to understand the rapidity of the subsurface flow response to rainstorms on hourly time scales. Three deep subsurface flows during four natural rainstorm events were monitored. The results show that (1) deeper discharge was observed early in responding rainfall events and yielded a high hydrograph amplitude; (2) a ratio index, k, reflecting the dynamic change of the rainfall perturbation intensity in subsurface flow, might reveal inner causal relationships between the flow index and the tracer signal index. Most values of k were larger than 1 at the perturbation stage but approximated 1 at the no-perturbation stage; and (3) for statistical analysis of tracer signals in subsurface flows, the total standard deviation was 17.2, 11.9, 7.4 and 3.5 at perturbation stages and 4.4, 2.5, 1.1, and 0.95 at the non-perturbation stage for observed events. These events were 3-7 times higher in the former rather than the later, reflecting that the variation of tracer signals primarily occurred under rainfall perturbation. Thus, we affirmed that the dynamic features of rainfall have a key effect on rapid processes because, besides the gravity, mechanical waves originating from dynamic rainfall features are another driving factor for conversion between different types of rainfall mechanical energy. A conceptual model for pressure wave propagation was proposed, in which virtual subsurface flow processes in a heterogeneous vadose zone under rainfall are analogous to the water hammer phenomenon in complex conduit systems. Such an analogy can allow pressure in a shallow vadose to increase and decrease and directly influence the velocity and celerity of the flow reflecting a mechanism for rapid subsurface hydrologic response processes in the shallow vadose zone.

  18. Hydrological partitioning in the critical zone: Recent advances and opportunities for developing transferable understanding of water cycle dynamics: CRITICAL ZONE HYDROLOGY

    DOE PAGES

    Brooks, Paul D.; Chorover, Jon; Fan, Ying; ...

    2015-09-01

    Hydrology is an integrative discipline linking the broad array of water‐related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy to themore » base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross‐site focus on “critical zone hydrology” has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: “how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?” Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning.« less

  19. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, Robert W.

    2005-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center [INTEC] at the Idaho National Laboratory [INL]). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate (primarily calcite) in groundwater and vadosemore » zone systems. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by (a) increasing pH and alkalinity and (b) liberating cations from the aquifer matrix by cation exchange reactions. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which is produced in situ by native urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long term. We are currently conducting field based activities at both the INL Vadose Zone Research Park (VZRP), an uncontaminated surrogate site for the strontium-90 contaminated vadose zone at INTEC and at the strontium-90 contaminated aquifer of 100-N area of the Hanford site.« less

  20. Three-dimensional modeling of nitrate-N transport in vadose zone: Roles of soil heterogeneity and groundwater flux.

    PubMed

    Akbariyeh, Simin; Bartelt-Hunt, Shannon; Snow, Daniel; Li, Xu; Tang, Zhenghong; Li, Yusong

    2018-04-01

    Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone. In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center pivot-irrigated corn field on Nebraska Management System Evaluation area over a three-year period. The model was based on a realistic three-dimensional sediment lithology, as well as carefully controlled irrigation and fertilizer application plans. In parallel, a homogeneous soil domain, containing the major sediment type of the site (i.e. sandy loam), was developed to conduct the same water flow and nitrate-N leaching simulations. Simulated nitrate-N concentrations were compared with the monitored nitrate-N concentrations in 10 multi-level sampling wells over a three-year period. Although soil heterogeneity was mainly observed from top soil to 3 m below the surface, heterogeneity controlled the spatial distribution of nitrate-N concentration. Soil heterogeneity, however, has minimal impact on the total mass of nitrate-N in the domain. In the deeper saturated zone, short-term variations of nitrate-N concentration correlated with the groundwater level fluctuations. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Three-dimensional modeling of nitrate-N transport in vadose zone: Roles of soil heterogeneity and groundwater flux

    NASA Astrophysics Data System (ADS)

    Akbariyeh, Simin; Bartelt-Hunt, Shannon; Snow, Daniel; Li, Xu; Tang, Zhenghong; Li, Yusong

    2018-04-01

    Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone. In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center pivot-irrigated corn field on Nebraska Management System Evaluation area over a three-year period. The model was based on a realistic three-dimensional sediment lithology, as well as carefully controlled irrigation and fertilizer application plans. In parallel, a homogeneous soil domain, containing the major sediment type of the site (i.e. sandy loam), was developed to conduct the same water flow and nitrate-N leaching simulations. Simulated nitrate-N concentrations were compared with the monitored nitrate-N concentrations in 10 multi-level sampling wells over a three-year period. Although soil heterogeneity was mainly observed from top soil to 3 m below the surface, heterogeneity controlled the spatial distribution of nitrate-N concentration. Soil heterogeneity, however, has minimal impact on the total mass of nitrate-N in the domain. In the deeper saturated zone, short-term variations of nitrate-N concentration correlated with the groundwater level fluctuations.

  2. H51E-1535: Biogeochemical factors influencing the transport and fate of colloids and colloid-associated contaminants in the vadose zone

    USDA-ARS?s Scientific Manuscript database

    The vadose zone exhibits large spatial and temporal variability in many physical, chemical, and biological factors that strongly influence the transport and fate of colloids (e.g., microbes, nanoparticles, clays, and dissolved organic matter) and colloid-associated contaminants (e.g., heavy metals, ...

  3. Water movement and solute transport in deep vadose zone under four irrigated agricultural land-use types in the North China Plain

    NASA Astrophysics Data System (ADS)

    Min, Leilei; Shen, Yanjun; Pei, Hongwei; Wang, Ping

    2018-04-01

    Groundwater-fed agriculture has caused water table declines and groundwater quality degradation in the North China Plain. Based on sediment sampling in deep vadose zone (with a maximum depth of 11.0 m), groundwater recharge, seepage velocity, solute inventory and transport under four typical irrigated agricultural land-use types (winter wheat and summer maize, WM; pear orchards, PO; outdoor vegetables, VE; and cotton, CO) were investigated in this study. The results reveal that there are many solutes stored in the vadose zone. Nitrate storage per unit depth in the vadose zone is highest under PO (1703 kg/ha), followed by VE (970 kg/ha), WM (736 kg/ha) and CO (727 kg/ha). However, the amount of annual leached nitrate under the four land-use types results in a different order (VE, 404 kg/ha; WM, 108 kg/ha; PO, 23 kg/ha; CO, 13 kg/ha). The estimated average recharge rates are 180 mm/yr for WM, 27 mm/yr for CO, 320 mm/yr for VE and 49 mm/yr for PO. The seepage velocity under VE (2.22 m/yr) exceeds the values under the other three land-use types (WM, 0.85 m/yr; PO, 0.49 m/yr; CO, 0.09 m/yr). The highest seepage velocity under VE caused significant nitrate contamination in groundwater, whereas the other two land-use types (WM and PO) had no direct influence on groundwater quality. The results of this work could be used for groundwater resources management.

  4. Electrical Resistivity Tomography monitoring reveals groundwater storage in a karst vadose zone

    NASA Astrophysics Data System (ADS)

    Watlet, A.; Kaufmann, O.; Van Camp, M. J.; Triantafyllou, A.; Cisse, M. F.; Quinif, Y.; Meldrum, P.; Wilkinson, P. B.; Chambers, J. E.

    2016-12-01

    Karst systems are among the most difficult aquifers to characterize, due to their high heterogeneity. In particular, temporary groundwater storage that occurs in the unsaturated zone and the discharge to deeper layers are difficult processes to identify and estimate with in-situ measurements. Electrical Resistivity Tomography (ERT) monitoring is meant to track changes in the electrical properties of the subsurface and has proved to be applicable to evidence and quantify hydrological processes in several types of environments. Applied to karst systems, it has particularly highlighted the challenges in linking electrical resistivity changes to groundwater content with usual approaches of petrophysical relationships, given the high heterogeneity of the subsurface. However, taking up the challenge, we undertook an ERT monitoring at the Rochefort Cave Laboratory (Belgium) lasting from Spring 2014 to Winter 2016. This includes 3 main periods of several months with daily measurements, from which seasonal groundwater content changes in the first meters of the vadose zone were successfully imaged. The monitoring concentrates on a 48 electrodes profile that goes from a limestone plateau to the bottom of a sinkhole. 3D UAV photoscans of the surveyed sinkhole and of the main chamber of the nearby cave were performed. Combined with lithological observations from a borehole drilled next to the ERT profile, the 3D information made it possible to project karstified layers visible in the cave to the surface and assess their potential locations along the ERT profile. Overall, this helped determining more realistic local petrophysical properties in the surveyed area, and improving the ERT data inversion by adding structural constraints. Given a strong air temperature gradient in the sinkhole, we also developed a new approach of temperature correction of the raw ERT data. This goes through the solving (using pyGIMLI package) of the 2D ground temperature field and its temporal

  5. Influence of colloids on the attenuation and transport of phosphorus in alluvial gravel aquifer and vadose zone media.

    PubMed

    Pang, Liping; Lafogler, Mark; Knorr, Bastian; McGill, Erin; Saunders, Darren; Baumann, Thomas; Abraham, Phillip; Close, Murray

    2016-04-15

    Phosphorous (P) leaching (e.g., from effluents, fertilizers) and transport in highly permeable subsurface media can be an important pathway that contributes to eutrophication of receiving surface waters as groundwater recharges the base-flow of surface waters. Here we investigated attenuation and transport of orthophosphate-P in gravel aquifer and vadose zone media in the presence and absence of model colloids (Escherichia coli, kaolinite, goethite). Experiments were conducted using repacked aquifer media in a large column (2m long, 0.19m in diameter) and intact cores (0.4m long, 0.24m in diameter) of vadose zone media under typical field flow rates. In the absence of the model colloids, P was readily traveled through the aquifer media with little attenuation (up to 100% recovery) and retardation, and P adsorption was highly reversible. Conversely, addition of the model colloids generally resulted in reduced P concentration and mass recovery (down to 28% recovery), and increased retardation and adsorption irreversibility in both aquifer and vadose zone media. The degree of colloid-assisted P attenuation was most significant in the presence of fine material and Fe-containing colloids at low flow rate but was least significant in the presence of coarse gravels and E. coli at high flow rate. Based on the experimental results, setback distances of 49-53m were estimated to allow a reduction of P concentrations in groundwater to acceptable levels in the receiving water. These estimates were consistent with field observations in the same aquifer media. Colloid-assisted P attenuation can be utilized to develop mitigation strategies to better manage effluent applications in gravelly soils. To efficiently retain P within soil matrix and reduce P leaching to groundwater, it is recommended to select soils that are rich in iron oxides, to periodically disturb soil preferential flow paths by tillage, and to apply a low irrigation rate. Copyright © 2016 Elsevier B.V. All rights

  6. Alternative Methods for Assessing Contaminant Transport from the Vadose Zone to Indoor Air

    NASA Astrophysics Data System (ADS)

    Baylor, K. J.; Lee, A.; Reddy, P.; Plate, M.

    2010-12-01

    Vapor intrusion, which is the transport of contaminant vapors from groundwater and the vadose zone to indoor air, has emerged as a significant human health risk near hazardous waste sites. Volatile organic compounds (VOCs) such as trichloroethylene (TCE) and tetrachloroethylene (PCE) can volatilize from groundwater and from residual sources in the vadose zone and enter homes and commercial buildings through cracks in the slab, plumbing conduits, or other preferential pathways. Assessment of the vapor intrusion pathway typically requires collection of groundwater, soil gas, and indoor air samples, a process which can be expensive and time-consuming. We evaluated three alternative vapor intrusion assessment methods, including 1) use of radon as a surrogate for vapor intrusion, 2) use of pressure differential measurements between indoor/outdoor and indoor/subslab to assess the potential for vapor intrusion, and 3) use of passive, longer-duration sorbent methods to measure indoor air VOC concentrations. The primary test site, located approximately 30 miles south of San Francisco, was selected due to the presence of TCE (10 - 300 ug/L) in shallow groundwater (5 to 10 feet bgs). At this test site, we found that radon was not a suitable surrogate to asses vapor intrusion and that pressure differential measurements are challenging to implement and equipment-intensive. More significantly, we found that the passive, longer-duration sorbent methods are easy to deploy and compared well quantitatively with standard indoor air sampling methods. The sorbent technique is less than half the cost of typical indoor air methods, and also provides a longer duration sample, typically 3 to 14 days rather than 8 to 24 hours for standard methods. The passive sorbent methods can be a reliable, cost-effective, and easy way to sample for TCE, PCE and other VOCs as part of a vapor intrusion investigation.

  7. Spatially resolved U(VI) partitioning and speciation: implications for plume scale behavior of contaminant U in the Hanford vadose zone.

    PubMed

    Wan, Jiamin; Kim, Yongman; Tokunaga, Tetsu K; Wang, Zheming; Dixit, Suvasis; Steefel, Carl I; Saiz, Eduardo; Kunz, Martin; Tamura, Nobumichi

    2009-04-01

    A saline-alkaline brine containing high concentration of U(VI) was accidentally spilled at the Hanford Site in 1951, introducing 10 tons of U into sediments under storage tank BX-102. U concentrations in the deep vadose zone and groundwater plumes increase with time, yet how the U has been migrating is not fully understood. We simulated the spill event in laboratory soil columns, followed by aging, and obtained spatially resolved U partitioning and speciation along simulated plumes. We found after aging, at apparent steady state, that the pore aqueous phase U concentrations remained surprisingly high (up to 0.022 M), in close agreement with the recently reported high U concentrations (up to 0.027 M) in the vadose zone plume (1). The pH values of aged pore liquids varying from 10 to 7, consistent with the measured pH of the field borehole sediments varying from 9.5 to 7.4 (2), from near the plume source to the plume front. The direct measurements of aged pore liquids together with thermodynamic calculations using a Pitzer approach revealed that UO2(CO3)3(4-) is the dominant aqueous U species within the plume body (pH 8-10), whereas Ca2UO2(CO3)3 and CaUO2(CO3)32- are also significant in the plume frontvicinity (pH 7-8), consistent with that measured from field borehole pore-waters (3). U solid phase speciation varies at different locations along the plume flow path and even within single sediment grains, because of location dependent pore and micropore solution chemistry. Our results suggest that continuous gravity-driven migration of the highly stable U02(CO3)34 in the residual carbonate and sodium rich tank waste solution is likely responsible for the detected growing U concentrations in the vadose zone and groundwater.

  8. Hydrologic Evaluation of a Humid Climate Poplar Phytoremediation Barrier

    NASA Astrophysics Data System (ADS)

    Swensen, K.; Rabideau, A. J.

    2016-12-01

    The emplacement of hybrid poplar trees to function as phytoremediation barriers is an appealing and sustainable groundwater management strategy because of low maintenance costs and the potential to extract large amounts of groundwater without pumping. While the effectiveness of poplar barriers has been assessed by groundwater quality monitoring, less attention has been given to physical hydrologic evaluations needed to improve barrier designs. In this research, a five year hydrologic evaluation was conducted at a poplar phytoremediation site in western NY, with the goal of quantifying ETg (evapotranspiration from groundwater) as a measure of the barrier's effectiveness in a humid climate. To consider transpiration from both vadose zone and groundwater, the hydrologic evaluation included four components: physical ET measurements, theoretical ET calculations, analysis of diurnal groundwater table fluctuations, and vadose zone modeling. The direct measurements of ETT (total) were obtained using sap flow meters installed on multiple trees within the barrier. These data were interpreted using a regression model that included theoretical ET calculations and site-specific measurements of weather parameters and poplar trunk area. Application of this model was challenged by the spatial variation in rooting depth as determined by tree excavations. To further quantify the removal of groundwater by the phytobarrier (ETg), the White Method was applied to interpret diurnal groundwater fluctuations from monitoring wells located within the barrier, in conjunction with a variably saturated-saturated flow model configured to confirm water extraction from ETg. Taken together, the results of this five year hydrologic evaluation highlight the complexity in quantifying humid climate groundwater extraction, as a large number of variables were found to influence these rates. Improved understanding of these controls will contribute to improved barrier designs that maximize ETg.

  9. Plutonium Particle Migration in the Shallow Vadose Zone: The Nevada Test Site as an Analog Site

    NASA Astrophysics Data System (ADS)

    Hunt, J. R.; Smith, D. K.

    2004-12-01

    The upper meter of the vadose zone in desert environments is the horizon where wastes have been released and human exposure is determined through dermal, inhalation, and food uptake pathways. This region is also characterized by numerous coupled processes that determine contaminant transport, including precipitation infiltration, evapotranspiration, daily and annual temperature cycling, dust resuspension, animal burrowing, and geochemical weathering reactions. While there is considerable interest in colloidal transport of minerals, pathogenic organisms, and contaminants in the vadose zone, there are limited field sites where the actual occurrence of contaminant migration can be quantified over the appropriate spatial and temporal scales of interest. At the US Department of Energy Nevada Test Site, there have been numerous releases of radionuclides since the 1950's that have become field-scale tracer tests. One series of tests was the four safety shots conducted in an alluvial valley of Area 11 in the 1950's. These experiments tested the ability of nuclear materials to survive chemical explosions without initiating fission reactions. Four above-ground tests were conducted and they released plutonium and uranium on the desert valley floor with only one of the tests undergoing some fission. Shortly after the tests, the sites were surveyed for radionuclide distribution on the land surface using aerial surveys and with depth. Additional studies were conducted in the 1970's to better understand the fate of plutonium in the desert that included studies of depth distribution and dust resuspension. More recently, plutonium particle distribution in the soil profile was detected using autoradiography. The results to date demonstrate the vertical migration of plutonium particles to depths in excess of 30 cm in this arid vadose zone. While plutonium migration at the Nevada Test Site has been and continues to be a concern, these field experiments have become analog sites for the

  10. A BENCHMARKING ANALYSIS FOR FIVE RADIONUCLIDE VADOSE ZONE MODELS (CHAIN, MULTIMED_DP, FECTUZ, HYDRUS, AND CHAIN 2D) IN SOIL SCREENING LEVEL CALCULATIONS

    EPA Science Inventory

    Five radionuclide vadose zone models with different degrees of complexity (CHAIN, MULTIMED_DP, FECTUZ, HYDRUS, and CHAIN 2D) were selected for use in soil screening level (SSL) calculations. A benchmarking analysis between the models was conducted for a radionuclide (99Tc) rele...

  11. SP Response to a Line Source Infiltration for Characterizing the Vadose Zone: Forward Modeling and Inversion

    NASA Astrophysics Data System (ADS)

    Sailhac, P.

    2004-05-01

    Field estimation of soil water flux has direct application for water resource management. Standard hydrologic methods like tensiometry or TDR are often difficult to apply because of the heterogeneity of the subsurface, and non invasive tools like ERT, NMR or GPR are limited to the estimation of the water content. Electrical Streaming Potential (SP) monitoring can provide a cost-effective tool to help estimate the nature of the hydraulic transfers (infiltration or evaporation) in the vadose zone. Indeed this technique has improved during the last decade and has been shown to be a useful tool for quantitative groundwater flow characterization (see the poster of Marquis et al. for a review). We now account for our latest development on the possibility of using SP for estimating hydraulic parameters of unsaturated soils from in situ SP measurements during infiltration experiments. The proposed method consists in SP profiling perpendicularly to a line source of steady-state infiltration. Analytic expressions for the forward modeling show a sensitivity to six parameters: the electrokinetic coupling parameter at saturation CS, the soil sorptive number α , the ratio of the constant source strength to the hydraulic conductivity at saturation q/KS, the soil effective water saturation prior to the infiltration experiment Se0, Mualem parameter m, and Archie law exponent n. In applications, all these parameters could be constrained by inverting electrokinetic data obtained during a series of infiltration experiments with varying source strength q.

  12. Vapor-phase transport of trichloroethene in an intermediate-scale vadose-zone system: retention processes and tracer-based prediction.

    PubMed

    Costanza-Robinson, Molly S; Carlson, Tyson D; Brusseau, Mark L

    2013-02-01

    Gas-phase transport experiments were conducted using a large weighing lysimeter to evaluate retention processes for volatile organic compounds (VOCs) in water-unsaturated (vadose-zone) systems, and to test the utility of gas-phase tracers for predicting VOC retardation. Trichloroethene (TCE) served as a model VOC, while trichlorofluoromethane (CFM) and heptane were used as partitioning tracers to independently characterize retention by water and the air-water interface, respectively. Retardation factors for TCE ranged between 1.9 and 3.5, depending on water content. The results indicate that dissolution into the bulk water was the primary retention mechanism for TCE under all conditions studied, contributing approximately two-thirds of the total measured retention. Accumulation at the air-water interface comprised a significant fraction of the observed retention for all experiments, with an average contribution of approximately 24%. Sorption to the solid phase contributed approximately 10% to retention. Water contents and air-water interfacial areas estimated based on the CFM and heptane tracer data, respectively, were similar to independently measured values. Retardation factors for TCE predicted using the partitioning-tracer data were in reasonable agreement with the measured values. These results suggest that gas-phase tracer tests hold promise for characterizing the retention and transport of VOCs in the vadose-zone. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Using the natural biodegradation potential of shallow soils for in-situ remediation of deep vadose zone and groundwater.

    PubMed

    Avishai, Lior; Siebner, Hagar; Dahan, Ofer; Ronen, Zeev

    2017-02-15

    In this study, we examined the ability of top soil to degrade perchlorate from infiltrating polluted groundwater under unsaturated conditions. Column experiments designed to simulate typical remediation operation of daily wetting and draining cycles of contaminated water amended with an electron donor. Covering the infiltration area with bentonite ensured anaerobic conditions. The soil remained unsaturated, and redox potential dropped to less than -200mV. Perchlorate was reduced continuously from ∼1150mg/L at the inlet to ∼300mg/L at the outlet in daily cycles. Removal efficiency was between 60 and 84%. No signs of bioclogging were observed during three operation months although occasional iron reduction observed due to excess electron donor. Changes in perchlorate reducing bacteria numbers were inferred from an increased in pcrA gene abundances from ∼10 5 to 10 7 copied per gram at the end of the experiment indicating the growth of perchlorate-reducing bacteria. We proposed that the topsoil may serve as a bioreactor to treat high concentrations of perchlorate from the contaminated groundwater. The treated water that infiltrates from the topsoil through the vadose zone could be used to flush perchlorate from the deep vadose zone into the groundwater where it is retrieved again for treatment in the topsoil. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Deep Vadose Zone Treatability Test for the Hanford Central Plateau. Interim Post-Desiccation Monitoring Results, Fiscal Year 2015

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Strickland, Christopher E.; Oostrom, Martinus

    A field test of desiccation is being conducted as an element of the Deep Vadose Zone Treatability Test Program. The active desiccation portion of the test has been completed. Monitoring data have been collected at the field test site during the post-desiccation period and are reported herein. This is an interim data summary report that includes about 4 years of post-desiccation monitoring data. The DOE field test plan proscribes a total of 5 years of post-desiccation monitoring.

  15. Ecological functions of riparian zones in Oregon hydrological landscapes

    EPA Science Inventory

    The ecological functions of streams and associated riparian zones are strongly influenced by the hydrological attributes of watersheds and landscapes in which they occur. Oregon hydrologic landscape regions (HLRs) have been defined based on four types of GIS data: 1) climate, 2) ...

  16. Assessing the impact of dairy waste lagoons on groundwater quality using a spatial analysis of vadose zone and groundwater information in a coastal phreatic aquifer.

    PubMed

    Baram, S; Kurtzman, D; Ronen, Z; Peeters, A; Dahan, O

    2014-01-01

    Dairy waste lagoons are considered to be point sources of groundwater contamination by chloride (Cl(-)), different nitrogen-species and pathogens/microorganisms. The objective of this work is to introduce a methodology to assess the past and future impacts of such lagoons on regional groundwater quality. The method is based on a spatial statistical analysis of Cl(-) and total nitrogen (TN) concentration distributions in the saturated and the vadose (unsaturated) zones. The method provides quantitative data on the relation between the locations of dairy lagoons and the spatial variability in Cl(-) and TN concentrations in groundwater. The method was applied to the Beer-Tuvia region, Israel, where intensive dairy farming has been practiced for over 50 years above the local phreatic aquifer. Mass balance calculations accounted for the various groundwater recharge and abstraction sources and sinks in the entire region. The mass balances showed that despite the small surface area covered by the dairy lagoons in this region (0.8%), leachates from lagoons have contributed 6.0% and 12.6% of the total mass of Cl(-) and TN (mainly as NO3(-)-N) added to the aquifer. The chemical composition of the aquifer and vadose zone water suggested that irrigated agricultural activity in the region is the main contributor of Cl(-) and TN to the groundwater. A low spatial correlation between the Cl(-) and NO3(-)-N concentrations in the groundwater and the on-land location of the dairy farms strengthened this assumption, despite the dairy waste lagoon being a point source for groundwater contamination by Cl(-) and NO3(-)-N. Mass balance calculations, for the vadose zone of the entire region, indicated that drying of the lagoons would decrease the regional groundwater salinization process (11% of the total Cl(-) load is stored under lagoons). A more considerable reduction in the groundwater contamination by NO3(-)-N is expected (25% of the NO3(-)-N load is stored under lagoons). Results

  17. Nitrate fluxes to groundwater under citrus orchards in a Mediterranean climate: Observations, calibrated models, simulations and agro-hydrological conclusions

    NASA Astrophysics Data System (ADS)

    Kurtzman, Daniel; Shapira, Roi H.; Bar-Tal, Asher; Fine, Pinchas; Russo, David

    2013-08-01

    Nitrate contamination of groundwater under land used for intensive-agriculture is probably the most worrisome agro-hydrological sustainability problem worldwide. Vadose-zone samples from 0 to 9 m depth under citrus orchards overlying an unconfined aquifer were analyzed for variables controlling water flow and the fate and transport of nitrogen fertilizers. Steady-state estimates of water and NO3-N fluxes to groundwater were found to vary spatially in the ranges of 90-330 mm yr- 1 and 50-220 kg ha- 1 yr- 1, respectively. Calibration of transient models to two selected vadose-zone profiles required limiting the concentration of NO3-N in the solution that is taken up by the roots to 30 mg L- 1. Results of an independent lysimeter experiment showed a similar nitrogen-uptake regime. Simulations of past conditions revealed a significant correlation between NO3-N flux to groundwater and the previous year's precipitation. Simulations of different nitrogen-application rates showed that using half of the nitrogen fertilizer added to the irrigation water by farmers would reduce average NO3-N flux to groundwater by 70%, decrease root nitrogen uptake by 20% and reduce the average pore water NO3-N concentration in the deep vadose zone to below the Israeli drinking water standard; hence this rate of nitrogen application was found to be agro-hydrologically sustainable. Beyond the investigation of nitrate fluxes to groundwater under citrus orchards and the interesting case-study aspects, this work demonstrates a methodology that enables skillful decisions concerning joint sustainability of both the water resource and agricultural production in a common environmental setting.

  18. Spectroscopic evidence for uranium bearing precipitates in vadose zone sediments at the Hanford 300-area site

    USGS Publications Warehouse

    Arai, Y.; Marcus, M.A.; Tamura, N.; Davis, J.A.; Zachara, J.M.

    2007-01-01

    Uranium (U) solid-state speciation in vadose zone sediments collected beneath the former North Process Pond (NPP) in the 300 Area of the Hanford site (Washington) was investigated using multi-scale techniques. In 30 day batch experiments, only a small fraction of total U (???7.4%) was released to artificial groundwater solutions equilibrated with 1% pCO2. Synchrotron-based micro-X-ray fluorescence spectroscopy analyses showed that U was distributed among at least two types of species: (i) U discrete grains associated with Cu and (ii) areas with intermediate U concentrations on grains and grain coatings. Metatorbernite (Cu[UO2]2[PO 4]2??8H2O) and uranophane (Ca[UO 2]2[SiO3(OH)]2?? 5H 2O) at some U discrete grains, and muscovite at U intermediate concentration areas, were identified in synchrotron-based micro-X-ray diffraction. Scanning electron microscopy/energy dispersive X-ray analyses revealed 8-10 ??m size metatorbernite particles that were embedded in C-, Al-, and Si-rich coatings on quartz and albite grains. In ??- and bulk-X-ray absorption structure (??-XAS and XAS) spectroscopy analyses, the structure of metatorbernite with additional U-C and U-U coordination environments was consistently observed at U discrete grains with high U concentrations. The consistency of the ??- and bulk-XAS analyses suggests that metatorbernite may comprise a significant fraction of the total U in the sample. The entrapped, micrometer-sized metatorbernite particles in C-, Al-, and Si-rich coatings, along with the more soluble precipitated uranyl carbonates and uranophane, likely control the long-term release of U to water associated with the vadose zone sediments. ?? 2007 American Chemical Society.

  19. Modeling vadose zone processes during land application of food-processing waste water in California's Central Valley.

    PubMed

    Miller, Gretchen R; Rubin, Yoram; Mayer, K Ulrich; Benito, Pascual H

    2008-01-01

    Land application of food-processing waste water occurs throughout California's Central Valley and may be degrading local ground water quality, primarily by increasing salinity and nitrogen levels. Natural attenuation is considered a treatment strategy for the waste, which often contains elevated levels of easily degradable organic carbon. Several key biogeochemical processes in the vadose zone alter the characteristics of the waste water before it reaches the ground water table, including microbial degradation, crop nutrient uptake, mineral precipitation, and ion exchange. This study used a process-based, multi-component reactive flow and transport model (MIN3P) to numerically simulate waste water migration in the vadose zone and to estimate its attenuation capacity. To address the high variability in site conditions and waste-stream characteristics, four food-processing industries were coupled with three site scenarios to simulate a range of land application outcomes. The simulations estimated that typically between 30 and 150% of the salt loading to the land surface reaches the ground water, resulting in dissolved solids concentrations up to sixteen times larger than the 500 mg L(-1) water quality objective. Site conditions, namely the ratio of hydraulic conductivity to the application rate, strongly influenced the amount of nitrate reaching the ground water, which ranged from zero to nine times the total loading applied. Rock-water interaction and nitrification explain salt and nitrate concentrations that exceed the levels present in the waste water. While source control remains the only method to prevent ground water degradation from saline wastes, proper site selection and waste application methods can reduce the risk of ground water degradation from nitrogen compounds.

  20. Vadose Zone Fate and Transport Simulation of Chemicals Associated with Coal Seam Gas Extraction

    NASA Astrophysics Data System (ADS)

    Simunek, J.; Mallants, D.; Jacques, D.; Van Genuchten, M.

    2017-12-01

    The HYDRUS-1D and HYDRUS (2D/3D) computer software packages are widely used finite element models for simulating the one-, and two- or three-dimensional movement of water, heat, and multiple solutes in variably-saturated media, respectively. While the standard HYDRUS models consider only the fate and transport of individual solutes or solutes subject to first-order degradation reactions, several specialized HYDRUS add-on modules can simulate far more complex biogeochemical processes. The objective of this presentation is to provide an overview of the HYDRUS models and their add-on modules, and to demonstrate applications of the software to the subsurface fate and transport of chemicals involved in coal seam gas extraction and water management operations. One application uses the standard HYDRUS model to evaluate the natural soil attenuation potential of hydraulic fracturing chemicals and their transformation products in case of an accidental release. By coupling the processes of retardation, first-order degradation and convective-dispersive transport of the biocide bronopol and its degradation products, we demonstrated how natural attenuation reduces initial concentrations by more than a factor of hundred in the top 5 cm of the vadose zone. A second application uses the UnsatChem module to explore the possible use of coal seam gas produced water for sustainable irrigation. Simulations with different irrigation waters (untreated, amended with surface water, and reverse osmosis treated) provided detailed results regarding chemical indicators of soil and plant health, notably SAR, EC and sodium concentrations. A third application uses the coupled HYDRUS-PHREEQC module to analyze trace metal transport involving cation exchange and surface complexation sorption reactions in the vadose zone leached with coal seam gas produced water following some accidental water release scenario. Results show that the main process responsible for trace metal migration is complexation of

  1. Vadose Zone Nitrate Transport Dynamics Resulting from Agricultural Groundwater Banking

    NASA Astrophysics Data System (ADS)

    Murphy, N. P.; McLaughlin, S.; Dahlke, H. E.

    2017-12-01

    In recent years, California's increased reliance on groundwater resources to meet agricultural and municipal demands has resulted in significant overdraft and water quality issues. Agricultural groundwater banking (AGB) has emerged as a promising groundwater replenishment opportunity in California; AGB is a form of managed aquifer recharge where farmland is flooded during the winter using excess surface water in order to recharge the underlying groundwater. Suitable farmland that is connected to water delivery systems is available for AGB throughout the Central Valley. However, questions remain how AGB could be implemented on fertilized agricultural fields such that nitrate leaching from the root zone is minimized. Here, we present results from field and soil column studies that investigate the transport dynamics of nitrogen in the root and deeper vadose zone during flooding events. We are specifically interested in estimating how timing and duration of flooding events affect percolation rates, leaching and nitrification/denitrification processes in three soil types within the Central Valley. Laboratory and field measurements include nitrogen (NO3-, NH4+, NO2-, N2O), redox potentials, total organic carbon, dissolved oxygen, moisture content and EC. Soil cores are collected in the field before and after recharge events up to a depth of 4m, while other sensors monitor field conditions continuously. Preliminary results from the three field sites show that significant portions of the applied floodwater (12-62 cm) infiltrated below the root zone: 96.1% (Delhi), 88.6% (Modesto) and 76.8% (Orland). Analysis of the soil cores indicate that 70% of the residual nitrate was flushed from the sandy soil, while the fine sandy loam showed only a 5% loss and in some cores even an increase in soil nitrate (in the upper 20cm). Column experiments support these trends and indicate that increases in soil nitrate in the upper root zone might be due to organic nitrogen mineralization and

  2. Quasi 3D modeling of water flow and solute transport in vadose zone and groundwater

    NASA Astrophysics Data System (ADS)

    Yakirevich, A.; Kuznetsov, M.; Weisbrod, N.; Pachepsky, Y. A.

    2013-12-01

    The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One commonly used simplification is based on the assumption that lateral flow and transport in unsaturated zone is insignificant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas through groundwater they are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow and transport is presented. A Quasi-3D approach allows representing flow in the 'vadose zone - aquifer' system by a series of 1D Richards' equations solved in variably-saturated zone and by 3D-saturated flow equation in groundwater (modified MODFLOW code). The 1D and 3D equations are coupled at the phreatic surface in a way that aquifer replenishment is calculated using the Richards' equation, and solving for the moving water table does not require definition of the specific yield parameter. The 3D advection-dispersion equation is solved in the entire domain by the MT3D code. Using implicit finite differences approximation to couple processes in the vadose zone and groundwater provides mass conservation and increase of computational efficiency. The above model was applied to simulate the impact of irrigation on groundwater salinity in the Alto Piura aquifer (Northern Peru). Studies on changing groundwater quality in arid and semi-arid lands show that irrigation return flow is one of the major factors contributing to aquifer salinization. Existing mathematical models do not account explicitly for the solute recycling during irrigation on a daily scale. Recycling occurs throughout the unsaturated and saturated zones, as function of the solute mass extracted from pumping wells. Salt concentration in irrigation water is calculated at each time step as a function of concentration of both surface water and groundwater

  3. Investigating In-Situ Mass Transfer Processes in a Groundwater U Plume Influenced by Groundwater-River Hydrologic and Geochemical Coupling (Invited)

    NASA Astrophysics Data System (ADS)

    Zachara, J. M.

    2009-12-01

    The Hanford Integrated Field Research Challenge (IFRC) site is a DOE/BER-supported experimental and monitoring facility focused on multi-scale mass transfer processes (hanfordifc@pnl.gov). It is located within the footprint of a historic uranium (U) waste disposal pond that overlies a contaminated vadose zone and a 1 km+ groundwater U plume. The plume is under a regulatory clean-up mandate. The site is in hydraulic connectivity with the Columbia River that is located approximately 300 m distant. Dramatic seasonal variations in Columbia River stage cause 2m+ variations in water table and associated changes in groundwater flow directions and composition that are believed to recharge contaminant U to the plume through lower vadose zone pumping. The 60 m triangular shaped facility contains 37 monitoring wells equipped with down-hole electrical resistance tomography electrode and thermistor arrays, pressure transducers for continual water level monitoring, and specific conductance electrodes. Well spacings allow cross-hole geophysical interrogation and dynamic plume monitoring. Various geophysical and hydrologic field characterizations were performed during and after well installation, and retrieved sediments are being subjected to a hierarchal laboratory characterization process to support geostatistical models of hydrologic properties, U(VI) distribution and speciation, and equilibrium and kinetic reaction parameters for robust but tractable field-scale reactive transport calculations. Three large scale (10,000 gal+), non-reactive tracer experiments have been performed to evaluate groundwater flowpaths and velocities, facies scale mass transfer, and subsurface heterogeneity effects under different hydrologic conditions (e.g., flow vectors toward or away from the river). A passive monitoring experiment was completed during spring and summer of 2009 that documents spatially variable U(VI) release and plume recharge from the contaminated lower vadose zone during

  4. Accounting for Ecohydrologic Separation Alters Interpreted Catchment Hydrology

    NASA Astrophysics Data System (ADS)

    Cain, M. R.; Ward, A. S.; Hrachowitz, M.

    2017-12-01

    Recent studies have demonstrated that in in some catchments, compartmentalized pools of water supply either plant transpiration (poorly mobile water) or streamflow and groundwater (highly mobile water), a phenomenon referred to as ecohydrologic separation. Although the literature has acknowledged that omission of ecohydrologic separation in hydrological models may influence estimates of residence times of water and solutes, no study has investigated how and when this compartmentalization might alter interpretations of fluxes and storages within a catchment. In this study, we develop two hydrochemical lumped rainfall-runoff models, one which incorporates ecohydrologic separation and one which does not for a watershed at the H.J. Andrews Experimental Forest (Oregon, USA), the study site where ecohydrologic separation was first observed. The models are calibrated against stream discharge, as well as stream chloride concentration. The objectives of this study are (1) to compare calibrated parameters and identifiability across models, (2) to determine how and when compartmentalization of water in the vadose zone might alter interpretations of fluxes and stores within the catchment, and (3) to identify how and when these changes alter residence times. Preliminary results suggest that compartmentalization of the vadose zone alters interpretations of fluxes and storages in the catchment and improves our ability to simulate solute transport.

  5. Emerging organic pollutants in the vadose zone of a soil aquifer treatment system: Pore water extraction using positive displacement.

    PubMed

    Sopilniak, Alexander; Elkayam, Roy; Rossin, Anna Voloshenko; Lev, Ovadia

    2018-01-01

    Trace organic compounds in effluents, water streams and aquifers are amply reported. However, the mobile pool of Emerging Organic Contaminants (EOCs) in the deep parts of the vadose zone is hard to estimate, due to difficulties in extraction of sufficient quantity of pore water. Here, we present a new methodology for depth profiling of EOCs in pore water by Positive Displacement Extraction (PDE): Pore water extraction from unsaturated soil samples is carried out by withdrawal of soil cores by direct-push drilling and infiltrating the core by organics free water. We show that EOC concentrations in the water eluted in the plateau region of the inverse breakthrough curve is equal to their pore water concentrations. The method was previously validated for DOC extraction, and here the scope of the methodology is extended to pore water extraction for organic pollutants analysis. Method characteristics and validation were carried out with atrazine, simazine, carbamazepine, venlafaxine, O-desmethylvenlafaxine and caffeine in the concentration range of several ng to several μg/liter. Validation was carried out by laboratory experiments on three different soils (sandy, sandy-clayey and clayey). Field studies in the vadose zone of a SAT system provided 27 m deep EOC profiles with less than 1.5 m spatial resolution. During the percolation treatment, carbamazepine remained persistent, while the other studied EOCs were attenuated to the extent of 50-99%.The highest degradation rate of all studied EOCs was in the aerobic zone. EOC levels based on PDE and extraction by centrifugation were compared, showing a positive bias for centrifugation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Vadose Zone and Surficial Monitoring a Controlled Release of Methane in the Borden Aquifer, Ontario.

    NASA Astrophysics Data System (ADS)

    Forde, O.; Mayer, K. U.; Cahill, A.; Parker, B. L.; Cherry, J. A.

    2015-12-01

    Development of shale gas resources and potential impacts on groundwater and fugitive gas emissions necessitates further research on subsurface methane gas (CH4) migration and fate. To address this issue, a controlled release experiment is undertaken at the Borden research aquifer, Ontario, Canada. Due to low solubility, it is expected that the injection will lead to gas exsolution and ebullition. Gas migration is expected to extend to the unsaturated zone and towards the ground surface, and may possibly be affected by CH4 oxidation. The project consists of multiple components targeting the saturated zone, unsaturated zone, and gas emissions at the ground surface. This presentation will focus on the analysis of surficial CO2 and CH4 effluxes and vadose zone gas composition to track the temporal and spatial evolution of fugitive gas. Surface effluxes are measured with flux chambers connected to a laser-based gas analyzer, and subsurface gas samples are being collected via monitoring wells equipped with sensors for oxygen, volumetric water content, electrical conductivity, and temperature to correlate with changes in gas composition. First results indicate rapid migration of CH4 to the ground surface in the vicinity of the injection locations. We will present preliminary data from this experiment and evaluate the distribution and rate of gas migration. This research specifically assesses environmental risks associated with fugitive gas emissions related to shale gas resource development.

  7. Water and vapor transfer in vadose zone of Gobi desert and riparian in the hyper arid environment of Ejina, China

    NASA Astrophysics Data System (ADS)

    Du, C.; Yu, J.; Sun, F.; Liu, X.

    2015-12-01

    To reveal how water and vapor transfer in vadose zone affect evapotranspiration in Gobi desert and riparian in hyper arid region is important for understanding eco-hydrological process. Field studies and numerical simulations were imported to evaluate the water and vapor movement processes under non isothermal and lower water content conditions. The soil profiles (12 layers) in Gobi desert and riparian sites of Ejina were installed with sensors to monitor soil moisture and temperature for 1 year. The meteorological conditions and water table were measured by micro weather stations and mini-Divers respectively in the two sites. Soil properties, including particles composition, moisture, bulk density, water retention curve, and saturated hydraulic conductivity of two site soil profiles, was measured. The observations showed that soil temperatures for the two sites displayed large diurnal and seasonal fluctuations. Temperature gradients with depth resulted in a downward in summer and upward in winter and became driving force for thermal vapor movement. Soil moistures in Gobi desert site were very low and varied slowly with time. While the soil moistures in riparian site were complicated due to root distribution but water potentials remained uniform with time. The hydrus-1D was employed to simulate evapotranspiration processes. The simulation results showed the significant difference of evaporation rate in the Gobi desert and riparian sites.

  8. You Don't Need Richards'... A New General 1-D Vadose Zone Solution Method that is Reliable

    NASA Astrophysics Data System (ADS)

    Ogden, F. L.; Lai, W.; Zhu, J.; Steinke, R. C.; Talbot, C. A.

    2015-12-01

    Hydrologic modelers and mathematicians have strived to improve 1-D Richards' equation (RE) solution reliability for predicting vadose zone fluxes. Despite advances in computing power and the numerical solution of partial differential equations since Richards first published the RE in 1931, the solution remains unreliable. That is to say that there is no guarantee that for a particular set of soil constitutive relations, moisture profile conditions, or forcing input that a numerical RE solver will converge to an answer. This risk of non-convergence renders prohibitive the use of RE solvers in hydrological models that need perhaps millions of infiltration solutions. In lieu of using unreliable numerical RE solutions, researchers have developed a wide array of approximate solutions that more-or-less mimic the behavior of the RE, with some notable deficiencies such as parameter insensitivity or divergence over time. The improved Talbot-Ogden (T-O) finite water-content scheme was shown by Ogden et al. (2015) to be an extremely good approximation of the 1-D RE solution, with a difference in cumulative infiltration of only 0.2 percent over an 8 month simulation comparing the improved T-O scheme with a RE numerical solver. The reason is that the newly-derived fundamental flow equation that underpins the improved T-O method is equivalent to the RE minus a term that is equal to the diffusive flux divided by the slope of the wetting front. Because the diffusive flux has zero mean, this term is not important in calculating the mean flux. The wetting front slope is near infinite (sharp) in coarser soils that produce more significant hydrological interactions between surface and ground waters, which also makes this missing term 1) disappear in the limit, and, 2) create stability challenges for the numerical solution of RE. The improved T-O method is a replacement for the 1-D RE in soils that can be simulated as homogeneous layers, where the user is willing to neglect the effects

  9. Deep Vadose Zone Treatability Test for the Hanford Central Plateau: Interim Post-Desiccation Monitoring Results

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Truex, Michael J.; Oostrom, Martinus; Strickland, Christopher E.

    2013-09-01

    A field test of desiccation is being conducted as an element of the deep vadose zone treatability test program. Desiccation technology relies on removal of water from a portion of the subsurface such that the resultant low moisture conditions inhibit downward movement of water and dissolved contaminants. Previously, a field test report (Truex et al. 2012a) was prepared describing the active desiccation portion of the test and initial post-desiccation monitoring data. Additional monitoring data have been collected at the field test site during the post-desiccation period and is reported herein along with interpretation with respect to desiccation performance. This ismore » an interim report including about 2 years of post-desiccation monitoring data.« less

  10. Development of Hydrologic Characterization Technology of Fault Zones (in Japanese; English)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karasaki, Kenzi; Onishi, Tiemi; Wu, Yu-Shu

    2008-03-31

    Through an extensive literature survey we find that there is very limited amount of work on fault zone hydrology, particularly in the field using borehole testing. The common elements of a fault include a core, and damage zones. The core usually acts as a barrier to the flow across it, whereas the damage zone controls the flow either parallel to the strike or dip of a fault. In most of cases the damage zone isthe one that is controlling the flow in the fault zone and the surroundings. The permeability of damage zone is in the range of two tomore » three orders of magnitude higher than the protolith. The fault core can have permeability up to seven orders of magnitude lower than the damage zone. The fault types (normal, reverse, and strike-slip) by themselves do not appear to be a clear classifier of the hydrology of fault zones. However, there still remains a possibility that other additional geologic attributes and scaling relationships can be used to predict or bracket the range of hydrologic behavior of fault zones. AMT (Audio frequency Magneto Telluric) and seismic reflection techniques are often used to locate faults. Geochemical signatures and temperature distributions are often used to identify flow domains and/or directions. ALSM (Airborne Laser Swath Mapping) or LIDAR (Light Detection and Ranging) method may prove to be a powerful tool for identifying lineaments in place of the traditional photogrammetry. Nonetheless not much work has been done to characterize the hydrologic properties of faults by directly testing them using pump tests. There are some uncertainties involved in analyzing pressure transients of pump tests: both low permeability and high permeability faults exhibit similar pressure responses. A physically based conceptual and numerical model is presented for simulating fluid and heat flow and solute transport through fractured fault zones using a multiple-continuum medium approach. Data from the Horonobe URL site are analyzed to

  11. Formation and transport of deethylatrazine in the soil and vadose zone

    USGS Publications Warehouse

    Adams, C.D.; Thurman, E.M.

    1991-01-01

    Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and two degradation products were monitored at seven depths in the soil and vadose zone throughout the growing season in two experimental plots in which corn (Zea mays L.) was grown. The soils in these plots were a Kimo silty clay loam (clayey over loamy, montmorillonitic, mesic, Fluvaquentic Hapludoll) and a Eudora silt loam (course, silty, mixed, mesic, Fluventic Hapludoll). The purpose this field study was to identify and quantify the mobile and persistent degradation products of atrazine that comprise the input, or “source term,” to groundwater resulting from the application of atrazine to the soils. The formation of deethylatrazine (2-amino-4-chloro-6-isopropylamino-s-triazine) and deisopropylatrazine (2-amino-4-chloro-6-ethylamino-s-triazine) was monitored at vurious depths using suction lysimeters to determine the relative proportions at which these compounds enter the aquifer. Deethylatrazine was the major degradation product of atrazine identified in the soil water and appeared to enter the underlying aquifer at a concentration of 5.0 µg/L, which was greater than the concentration of atrazine entering the aquifer. Deisopropylatrazine also was detected in the soil water, bnt only in minor concentrations relative to atrazine and deethylatrazine. Because deethylatrazine was the major degradation product in the unsaturated zone, the deethylatrazine-to-atrazine ratio (DAR) may be a good indicator of transport of atrazine through the soil. The hypothesis is proposed that the DAR may be used to distinguish point-source from nonpoint-source contamination of an aquifer.

  12. Enhanced vadose zone nitrogen removal by poplar during dormancy.

    PubMed

    Ausland, Hayden; Ward, Adam; Licht, Louis; Just, Craig

    2015-01-01

    A pilot-scale, engineered poplar tree vadose zone system was utilized to determine effluent nitrate (NO3(-)) and ammonium concentrations resulting from intermittent dosing of a synthetic wastewater onto sandy soils at 4.5°C. The synthetic wastewater replicated that of an industrial food processor that irrigates onto sandy soils even during dormancy which can leave groundwater vulnerable to NO3(-) contamination. Data from a 21-day experiment was used to assess various Hydrus model parameterizations that simulated the impact of dormant roots. Bromide tracer data indicated that roots impacted the hydraulic properties of the packed sand by increasing effective dispersion, water content and residence time. The simulated effluent NO3(-) concentration on day 21 was 1.2 mg-N L(-1) in the rooted treatments compared to a measured value of 1.0 ± 0.72 mg-N L(-1). For the non-rooted treatment, the simulated NO3(-) concentration was 4.7 mg-N L(-1) compared to 5.1 ± 3.5 mg-N L(-1) measured on day 21. The model predicted a substantial "root benefit" toward protecting groundwater through increased denitrification in rooted treatments during a 21-day simulation with 8% of dosed nitrogen converted to N2 compared to 3.3% converted in the non-rooted test cells. Simulations at the 90-day timescale provided similar results, indicating increased denitrification in rooted treatments.

  13. Laboratory investigations of the effects of nitrification-induced acidification on Cr cycling in vadose zone material partially derived from ultramafic rocks

    USGS Publications Warehouse

    Mills, Christopher T.; Goldhaber, Martin B.

    2012-01-01

    Sacramento Valley (California, USA) soils and sediments have high concentrations of Cr(III) because they are partially derived from ultramafic material. Some Cr(III) is oxidized to more toxic and mobile Cr(VI) by soil Mn oxides. Valley soils typically have neutral to alkaline pH at which Cr(III) is highly immobile. Much of the valley is under cultivation and is both fertilized and irrigated. A series of laboratory incubation experiments were conducted to assess how cultivation might impact Cr cycling in shallow vadose zone material from the valley. The first experiments employed low (7.1 mmol N per kg soil) and high (35 mmol N kg− 1) concentrations of applied (NH4)2SO4. Initially, Cr(VI) concentrations were up to 45 and 60% greater than controls in low and high incubations, respectively. After microbially-mediated oxidation of all NH4+, Cr(VI) concentrations dropped below control values. Increased nitrifying bacterial populations (estimated by measurement of phospholipid fatty acids) may have increased the Cr(VI) reduction capacity of the vadose zone material resulting in the observed decreases in Cr(VI). Another series of incubations employed vadose zone material from a different location to which low (45 meq kg− 1) and high (128 meq kg− 1) amounts of NH4Cl, KCl, and CaCl2 were applied. All treatments, except high concentration KCl, resulted in mean soil Cr(VI) concentrations that were greater than the control. High concentrations of water-leachable Ba2 + (mean 38 μmol kg− 1) in this treatment may have limited Cr(VI) solubility. A final set of incubations were amended with low (7.1 mmol N kg− 1) and high (35 mmol N kg− 1) concentrations of commercial liquid ammonium polyphosphate (APP) fertilizer which contained high concentrations of Cr(III). Soil Cr(VI) in the low APP incubations increased to a concentration of 1.8 μmol kg− 1 (5 × control) over 109 days suggesting that Cr(III) added with the APP fertilizer was more

  14. Characterization of Vadose Zone Sediment: Borehole 299-E33-46 Near Tank B-110 in the B-BX-BY Waste Management Area.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Gee, Glendon W.

    2002-12-15

    This report presents vadose sediment characterization data that improves understanding of the nature and extent of past releases in the B tank farm. A vertical borehole, located approximately 15 ft (5 m) from the northeast edge of single-shell tank 241-B-110 was drilled to a total depth of 264.4 ft bgs, the groundwater table was encountered at 255.8 ft bgs. During drilling, a total of 3 two-ft long, 4-inch diameter split-spoon core samples were collected between 10 and 254 ft bgs-an average of every 7.5 ft. Grab samples were collected between these core sample intervals to yield near continuous samples tomore » a depth of 78.3 m (257 ft). Geologic logging occurred after each core segment was emptied into an open plastic container, followed by photographing and sub-sampling for physical and chemical characterization. In addition, 54 out of a total of 120 composite grab samples were opened, sub-sampled, logged, and photographed. Immediately following the geologic examination, the core and selected grab samples were sub-sampled for moisture content, gamma-emission radiocounting, tritium and strontium-90 determinations, total carbon and inorganic carbon content, and 8 M nitric acid extracts (which provide a measure of the total leachable sediment content of contaminants) and one-to-one sediment to water extracts (which provide soil pH, electrical conductivity, cation, and anion data and water soluble contaminant data. Later, additional aliquots of selected sleeves or grab samples were removed to measure particle size distribution and mineralogy and to squeeze porewater. Major conclusions follow. Vadose zone contamination levels were lower than generally anticipated prior to the initiation of the field investigation. Strong evidence of extensive vadose zone lateral migration in WMA BBXBY exists. There are indications that such lateral migration may have extended into WMA B-BX-BY from adjacent past practice discharge sites. Ponding of runoff from natural precipitation

  15. Seasonal Variability in Vadose zone biodegradation at a crude oil pipeline rupture site

    USGS Publications Warehouse

    Sihota, Natasha J.; Trost, Jared J.; Bekins, Barbara; Berg, Andrew M.; Delin, Geoffrey N.; Mason, Brent E.; Warren, Ean; Mayer, K. Ulrich

    2016-01-01

    Understanding seasonal changes in natural attenuation processes is critical for evaluating source-zone longevity and informing management decisions. The seasonal variations of natural attenuation were investigated through measurements of surficial CO2 effluxes, shallow soil CO2 radiocarbon contents, subsurface gas concentrations, soil temperature, and volumetric water contents during a 2-yr period. Surficial CO2 effluxes varied seasonally, with peak values of total soil respiration (TSR) occurring in the late spring and summer. Efflux and radiocarbon data indicated that the fractional contributions of natural soil respiration (NSR) and contaminant soil respiration (CSR) to TSR varied seasonally. The NSR dominated in the spring and summer, and CSR dominated in the fall and winter. Subsurface gas concentrations also varied seasonally, with peak values of CO2 and CH4 occurring in the fall and winter. Vadose zone temperatures and subsurface CO2 concentrations revealed a correlation between contaminant respiration and temperature. A time lag of 5 to 7 mo between peak subsurface CO2 concentrations and peak surface efflux is consistent with travel-time estimates for subsurface gas migration. Periods of frozen soils coincided with depressed surface CO2 effluxes and elevated CO2 concentrations, pointing to the temporary presence of an ice layer that inhibited gas transport. Quantitative reactive transport simulations demonstrated aspects of the conceptual model developed from field measurements. Overall, results indicated that source-zone natural attenuation (SZNA) rates and gas transport processes varied seasonally and that the average annual SZNA rate estimated from periodic surface efflux measurements is 60% lower than rates determined from measurements during the summer.

  16. Measuring Spatial Variability of Vapor Flux to Characterize Vadose-zone VOC Sources: Flow-cell Experiments

    DOE PAGES

    Mainhagu, Jon; Morrison, C.; Truex, Michael J.; ...

    2014-08-05

    A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. Amore » well-defined source zone was created by injection and extraction of a non-reactive gas (SF6). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local–extraction point, whereas increases were observed for monitoring points located between the local–extraction point and the source zone. We found that the results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.« less

  17. CO2 migration in the vadose zone: experimental and numerical modelling of controlled gas injection

    NASA Astrophysics Data System (ADS)

    gasparini, andrea; credoz, anthony; grandia, fidel; garcia, david angel; bruno, jordi

    2014-05-01

    The mobility of CO2 in the vadose zone and its subsequent transfer to the atmosphere is a matter of concern in the risk assessment of the geological storage of CO2. In this study the experimental and modelling results of controlled CO2 injection are reported to better understanding of the physical processes affecting CO2 and transport in the vadose zone. CO2 was injected through 16 micro-injectors during 49 days of experiments in a 35 m3 experimental unit filled with sandy material, in the PISCO2 facilities at the ES.CO2 centre in Ponferrada (North Spain). Surface CO2 flux were monitored and mapped periodically to assess the evolution of CO2 migration through the soil and to the atmosphere. Numerical simulations were run to reproduce the experimental results, using TOUGH2 code with EOS7CA research module considering two phases (gas and liquid) and three components (H2O, CO2, air). Five numerical models were developed following step by step the injection procedure done at PISCO2. The reference case (Model A) simulates the injection into a homogeneous soil(homogeneous distribution of permeability and porosity in the near-surface area, 0.8 to 0.3 m deep from the atmosphere). In another model (Model B), four additional soil layers with four specific permeabilities and porosities were included to predict the effect of differential compaction on soil. To account for the effect of higher soil temperature, an isothermal simulation called Model C was also performed. Finally, the assessment of the rainfall effects (soil water saturation) on CO2 emission on surface was performed in models called Model D and E. The combined experimental and modelling approach shows that CO2 leakage in the vadose zone quickly comes out through preferential migration pathways and spots with the ranges of fluxes in the ground/surface interface from 2.5 to 600 g·m-2·day-1. This gas channelling is mainly related to soil compaction and climatic perturbation. This has significant implications to

  18. Parallel inversion of a massive ERT data set to characterize deep vadose zone contamination beneath former nuclear waste infiltration galleries at the Hanford Site B-Complex (Invited)

    NASA Astrophysics Data System (ADS)

    Johnson, T.; Rucker, D. F.; Wellman, D.

    2013-12-01

    The Hanford Site, located in south-central Washington, USA, originated in the early 1940's as part of the Manhattan Project and produced plutonium used to build the United States nuclear weapons stockpile. In accordance with accepted industrial practice of that time, a substantial portion of relatively low-activity liquid radioactive waste was disposed of by direct discharge to either surface soil or into near-surface infiltration galleries such as cribs and trenches. This practice was supported by early investigations beginning in the 1940s, including studies by Geological Survey (USGS) experts, whose investigations found vadose zone soils at the site suitable for retaining radionuclides to the extent necessary to protect workers and members of the general public based on the standards of that time. That general disposal practice has long since been discontinued, and the US Department of Energy (USDOE) is now investigating residual contamination at former infiltration galleries as part of its overall environmental management and remediation program. Most of the liquid wastes released into the subsurface were highly ionic and electrically conductive, and therefore present an excellent target for imaging by Electrical Resistivity Tomography (ERT) within the low-conductivity sands and gravels comprising Hanford's vadose zone. In 2006, USDOE commissioned a large scale surface ERT survey to characterize vadose zone contamination beneath the Hanford Site B-Complex, which contained 8 infiltration trenches, 12 cribs, and one tile field. The ERT data were collected in a pole-pole configuration with 18 north-south trending lines, and 18 east-west trending lines ranging from 417m to 816m in length. The final data set consisted of 208,411 measurements collected on 4859 electrodes, covering an area of 600m x 600m. Given the computational demands of inverting this massive data set as a whole, the data were initially inverted in parts with a shared memory inversion code, which

  19. Final Technical Report for "High-resolution temporal variations in groundwater chemistry: Tracing the links between climate, hydrology, and element mobility in the vadose zone"

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jay L. Banner

    2002-04-23

    In spite of a developing emphasis on geochemical methods in studies of modern hydrologic systems, there have been few attempts to examine temporal fluctuations in groundwater chemistry and element mobility in the near-surface environment. Relatively little is known regarding how groundwaters evolve over 10 to 10,000 year scales, yet this knowledge provides a critical framework for understanding the links between climate and hydrology, the evolution of soils, and element migration in the vadose environment. Recent analytical advances allow U-series measurements to be applied to developing high-resolution chronologies of Pleistocene and Holocene carbonates. The potential of these new tools is examinedmore » through an analysis of two well-defined, active karst systems in (1) Barbados and (2) Texas. (1) The research effort on Barbados has developed methods of estimating recharge and inferring the spatial and seasonal distribution of recharge to the Pleistocene limestone aquifer on Barbados. A new method has been developed to estimate recharge based on oxygen isotope variations in rainwater and groundwater. Inter-annual recharge variations indicate that recharge is dependent on the distribution of rainfall throughout the year rather than total annual rainfall. Consequently, a year when rainfall occurs primarily during the peak wet season months (August through November) may have more recharge than a year when rainfall is more evenly distributed through the year. These results lay important groundwork for analysis of rainfall/recharge variations over different time scales based on isotopic records presently being constructed using Barbados speleothems from the same aquifer. (2) The chronology of speleothems (cave calcite deposits) from three caves across 130 kilometers in central Texas provides a 71,000-year record of temporal changes in hydrology and climate. Fifty-three ages were determined by mass spectrometric 238U - 230Th and 235U - 231Pa analyses. The accuracy

  20. Cost of riparian buffer zones: A comparison of hydrologically adapted site-specific riparian buffers with traditional fixed widths

    NASA Astrophysics Data System (ADS)

    Tiwari, T.; Lundström, J.; Kuglerová, L.; Laudon, H.; Öhman, K.; Ågren, A. M.

    2016-02-01

    Traditional approaches aiming at protecting surface waters from the negative impacts of forestry often focus on retaining fixed width buffer zones around waterways. While this method is relatively simple to design and implement, it has been criticized for ignoring the spatial heterogeneity of biogeochemical processes and biodiversity in the riparian zone. Alternatively, a variable width buffer zone adapted to site-specific hydrological conditions has been suggested to improve the protection of biogeochemical and ecological functions of the riparian zone. However, little is known about the monetary value of maintaining hydrologically adapted buffer zones compared to the traditionally used fixed width ones. In this study, we created a hydrologically adapted buffer zone by identifying wet areas and groundwater discharge hotspots in the riparian zone. The opportunity cost of the hydrologically adapted riparian buffer zones was then compared to that of the fixed width zones in a meso-scale boreal catchment to determine the most economical option of designing riparian buffers. The results show that hydrologically adapted buffer zones were cheaper per hectare than the fixed width ones when comparing the total cost. This was because the hydrologically adapted buffers included more wetlands and low productive forest areas than the fixed widths. As such, the hydrologically adapted buffer zones allows more effective protection of the parts of the riparian zones that are ecologically and biogeochemically important and more sensitive to disturbances without forest landowners incurring any additional cost than fixed width buffers.

  1. Newly recognized hosts for uranium in the Hanford Site vadose zone

    USGS Publications Warehouse

    Stubbs, J.E.; Veblen, L.A.; Elbert, D.C.; Zachara, J.M.; Davis, J.A.; Veblen, D.R.

    2009-01-01

    Uranium contaminated sediments from the U.S. Department of Energy's Hanford Site have been investigated using electron microscopy. Six classes of solid hosts for uranium were identified. Preliminary sediment characterization was carried out using optical petrography, and electron microprobe analysis (EMPA) was used to locate materials that host uranium. All of the hosts are fine-grained and intergrown with other materials at spatial scales smaller than the analytical volume of the electron microprobe. A focused ion beam (FIB) was used to prepare electron-transparent specimens of each host for the transmission electron microscope (TEM). The hosts were identified as: (1) metatorbernite [Cu(UO2)2(PO4)2??8H2O]; (2) coatings on sediment clasts comprised mainly of phyllosilicates; (3) an amorphous zirconium (oxyhydr)oxide found in clast coatings; (4) amorphous and poorly crystalline materials that line voids within basalt lithic fragments; (5) amorphous palagonite surrounding fragments of basaltic glass; and (6) Fe- and Mn-oxides. These findings demonstrate the effectiveness of combining EMPA, FIB, and TEM to identify solid-phase contaminant hosts. Furthermore, they highlight the complexity of U geochemistry in the Hanford vadose zone, and illustrate the importance of microscopic transport in controlling the fate of contaminant metals in the environment. ?? 2008 Elsevier Ltd.

  2. Characterizing Hydrological Processes in Vadose Zone by Direct Infiltration Water Sampling.

    NASA Astrophysics Data System (ADS)

    Mori, Y.; Higashi, N.; Somura, H.; Takeda, I.; Inoue, M.

    2007-12-01

    These days, planted forest mountainside was roughly maintained due to the population descent and small birth rate. Because thinning operation would delayed, forest was always dark and floor weed was rare. Management induced non point source pollution like surface soil erosion was suspected, however, we could not approach to the source with the stream water analysis. Therefore, direct soil water sampling device using glass fiber capillary force was developed to examine hydrological processes in watershed. In our design, water was collected just by the capillary force and let the excess water down through so that infiltration water was truly sampled and solute concentration kept the same quality as in soil water. The experiment was conducted at two neighboring Japanese cedar planted forest under different management, i.e., south slope was roughly maintained and west slope was well maintained by thinning operation. Load discharges were higher in south slope and lower in west slope. Infiltration water analysis revealed that ion concentration was gradually decreased at west slope, however in south slope, it dropped to lower level in soil water and increased again in stream water. The trend showed that soil buffering function was poor in south slope. Actually, disk permeameter survey revealed that hydraulic conductivity was small in south slope; TOC and biological activity were lower. This entire soil environment explained the water environmental differences in stream water. Because changes in soil environment affects water environment in the future, monitoring or examination of soil environment was considered as preventive measure for environmentally sound water and solute circulation in watershed.

  3. Hyporheic zone hydrologic science: A historical account of its emergence and a prospectus

    NASA Astrophysics Data System (ADS)

    Cardenas, M. Bayani

    2015-05-01

    The hyporheic zone, defined by shallow subsurface pathways through river beds and banks beginning and ending at the river, is an integral and unique component of fluvial systems. It hosts myriad hydrologically controlled processes that are potentially coupled in complex ways. Understanding these processes and the connections between them is critical since these processes are not only important locally but integrate to impact increasingly larger scale biogeochemical functioning of the river corridor up to the river network scale. Thus, the hyporheic zone continues to be a growing research focus for many hydrologists for more than half the history of Water Resources Research. This manuscript partly summarizes the historical development of hyporheic zone hydrologic science as gleaned from papers published in Water Resources Research, from the birth of the concept of the hyporheic zone as a hydrologic black box (sometimes referred to as transient storage zone), to its adolescent years of being torn between occasionally competing research perspectives of interrogating the hyporheic zone from a surface or subsurface view, to its mature emergence as an interdisciplinary research field that employs the wide array of state-of-the-art tools available to the modern hydrologist. The field is vibrant and moving in the right direction of addressing critical fundamental and applied questions with no clear end in sight in its growth. There are exciting opportunities for scientists that are able to tightly link the allied fields of geology, geomorphology, hydrology, geochemistry, and ecology to tackle the many open problems in hyporheic zone science.

  4. Hydropedology: Synergistic integration of soil science and hydrology in the Critical Zone

    USGS Publications Warehouse

    Lin, H.S.; McDonnell, J.J.; Nimmo, John R.; Pachepsky, Y. A.

    2016-01-01

    Soil and water are the two critical components of theEarth’s Critical Zone (Figure 1): Soil modulates the connection between bedrock and the atmospheric boundary layer and water is a major driving force and transport agent between these two zones. The interactions between soil and water are so intimate and complex that they cannot be effectively studied in a piecemeal manner; they require a systems approach. In this spirit, hydropedology has emerged in recent years as a synergistic integration of soil science and hydrology that offers a renewed perspective and an integrated approach to understanding interactive pedologic and hydrologic processes and their properties in the Critical Zone.

  5. System-Scale Model of Aquifer, Vadose Zone, and River Interactions for the Hanford 300 Area - Application to Uranium Reactive Transport

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rockhold, Mark L.; Bacon, Diana H.; Freedman, Vicky L.

    2013-10-01

    This report represents a synthesis and integration of basic and applied research into a system-scale model of the Hanford 300 Area groundwater uranium plume, supported by the U.S. Department of Energy’s Richland Operations (DOE-RL) office. The report integrates research findings and data from DOE Office of Science (DOE-SC), Office of Environmental Management (DOE-EM), and DOE-RL projects, and from the site remediation and closure contractor, Washington Closure Hanford, LLC (WCH). The three-dimensional, system-scale model addresses water flow and reactive transport of uranium for the coupled vadose zone, unconfined aquifer, and Columbia River shoreline of the Hanford 300 Area. The system-scale modelmore » of the 300 Area was developed to be a decision-support tool to evaluate processes of the total system affecting the groundwater uranium plume. The model can also be used to address “what if” questions regarding different remediation endpoints, and to assist in design and evaluation of field remediation efforts. For example, the proposed cleanup plan for the Hanford 300 Area includes removal, treatment, and disposal of contaminated sediments from known waste sites, enhanced attenuation of uranium hot spots in the vadose and periodically rewetted zone, and continued monitoring of groundwater with institutional controls. Illustrative simulations of polyphosphate infiltration were performed to demonstrate the ability of the system-scale model to address these types of questions. The use of this model in conjunction with continued field monitoring is expected to provide a rigorous basis for developing operational strategies for field remediation and for defining defensible remediation endpoints.« less

  6. Numerical model of water flow in a fractured basalt vadose zone: Box Canyon Site, Idaho

    NASA Astrophysics Data System (ADS)

    Doughty, Christine

    2000-12-01

    A numerical model of a fractured basalt vadose zone has been developed on the basis of the conceptual model described by Faybishenko et al. [[his issue]. The model has been used to simulate a ponded infiltration test in order to investigate infiltration through partially saturated fractured basalt. A key question addressed is how the fracture pattern geometry and fracture connectivity within a single basalt flow of the Snake River Plain basalt affect water infiltration. The two-dimensional numerical model extends from the ground surface to a perched water body 20 m below and uses an unconventional quasi-deterministic approach with explicit but highly simplified representation of major fractures and other important hydrogeologic features. The model adequately reproduces the majority of the field observation and provides insights into the infiltration process that cannot be obtained by data collection alone, demonstrating its value as a component of field studies.

  7. Using vadose zone data and spatial statistics to assess the impact of cultivated land and dairy waste lagoons on groundwater contamination

    NASA Astrophysics Data System (ADS)

    Baram, S.; Ronen, Z.; Kurtzman, D.; Peeters, A.; Dahan, O.

    2013-12-01

    Land cultivation and dairy waste lagoons are considered to be nonpoint and point sources of groundwater contamination by chloride (Cl-) and nitrate (NO3-). The objective of this work is to introduce a methodology to assess the past and future impacts of such agricultural activities on regional groundwater quality. The method is based on mass balances and on spatial statistical analysis of Cl- and NO3-concentration distributions in the saturated and unsaturated zones. The method enables quantitative analysis of the relation between the locations of pollution point sources and the spatial variability in Cl- and NO3- concentrations in groundwater. The method was applied to the Beer-Tuvia region, Israel, where intensive dairy farming along with land cultivation has been practiced for over 50 years above the local phreatic aquifer. Mass balance calculations accounted for the various groundwater recharge and abstraction sources and sinks in the entire region. The mass balances showed that leachates from lagoons and the cultivated land have contributed 6.0 and 89.4 % of the total mass of Cl- added to the aquifer and 12.6 and 77.4 % of the total mass of NO3-. The chemical composition of the aquifer and vadose zone water suggested that irrigated agricultural activity in the region is the main contributor of Cl- and NO3- to the groundwater. A low spatial correlation between the Cl- and NO3- concentrations in the groundwater and the on-land location of the dairy farms strengthened this assumption, despite the dairy waste lagoon being a point source for groundwater contamination by Cl- and NO3-. Results demonstrate that analyzing vadose zone and groundwater data by spatial statistical analysis methods can significantly contribute to the understanding of the relations between groundwater contaminating sources, and to assessing appropriate remediation steps.

  8. The evolution of root-zone moisture capacities after deforestation: a step towards hydrological predictions under change?

    NASA Astrophysics Data System (ADS)

    Nijzink, Remko; Hutton, Christopher; Pechlivanidis, Ilias; Capell, René; Arheimer, Berit; Freer, Jim; Han, Dawei; Wagener, Thorsten; McGuire, Kevin; Savenije, Hubert; Hrachowitz, Markus

    2016-12-01

    The core component of many hydrological systems, the moisture storage capacity available to vegetation, is impossible to observe directly at the catchment scale and is typically treated as a calibration parameter or obtained from a priori available soil characteristics combined with estimates of rooting depth. Often this parameter is considered to remain constant in time. Using long-term data (30-40 years) from three experimental catchments that underwent significant land cover change, we tested the hypotheses that: (1) the root-zone storage capacity significantly changes after deforestation, (2) changes in the root-zone storage capacity can to a large extent explain post-treatment changes to the hydrological regimes and that (3) a time-dynamic formulation of the root-zone storage can improve the performance of a hydrological model.A recently introduced method to estimate catchment-scale root-zone storage capacities based on climate data (i.e. observed rainfall and an estimate of transpiration) was used to reproduce the temporal evolution of root-zone storage capacity under change. Briefly, the maximum deficit that arises from the difference between cumulative daily precipitation and transpiration can be considered as a proxy for root-zone storage capacity. This value was compared to the value obtained from four different conceptual hydrological models that were calibrated for consecutive 2-year windows.It was found that water-balance-derived root-zone storage capacities were similar to the values obtained from calibration of the hydrological models. A sharp decline in root-zone storage capacity was observed after deforestation, followed by a gradual recovery, for two of the three catchments. Trend analysis suggested hydrological recovery periods between 5 and 13 years after deforestation. In a proof-of-concept analysis, one of the hydrological models was adapted to allow dynamically changing root-zone storage capacities, following the observed changes due to

  9. Vegetation root zone storage and rooting depth, derived from local calibration of a global hydrological model

    NASA Astrophysics Data System (ADS)

    van der Ent, R.; Van Beek, R.; Sutanudjaja, E.; Wang-Erlandsson, L.; Hessels, T.; Bastiaanssen, W.; Bierkens, M. F.

    2017-12-01

    The storage and dynamics of water in the root zone control many important hydrological processes such as saturation excess overland flow, interflow, recharge, capillary rise, soil evaporation and transpiration. These processes are parameterized in hydrological models or land-surface schemes and the effect on runoff prediction can be large. Root zone parameters in global hydrological models are very uncertain as they cannot be measured directly at the scale on which these models operate. In this paper we calibrate the global hydrological model PCR-GLOBWB using a state-of-the-art ensemble of evaporation fields derived by solving the energy balance for satellite observations. We focus our calibration on the root zone parameters of PCR-GLOBWB and derive spatial patterns of maximum root zone storage. We find these patterns to correspond well with previous research. The parameterization of our model allows for the conversion of maximum root zone storage to root zone depth and we find that these correspond quite well to the point observations where available. We conclude that climate and soil type should be taken into account when regionalizing measured root depth for a certain vegetation type. We equally find that using evaporation rather than discharge better allows for local adjustment of root zone parameters within a basin and thus provides orthogonal data to diagnose and optimize hydrological models and land surface schemes.

  10. Vegetation root zone storage and rooting depth, derived from local calibration of a global hydrological model

    NASA Astrophysics Data System (ADS)

    van der Ent, Ruud; van Beek, Rens; Sutanudjaja, Edwin; Wang-Erlandsson, Lan; Hessels, Tim; Bastiaanssen, Wim; Bierkens, Marc

    2017-04-01

    The storage and dynamics of water in the root zone control many important hydrological processes such as saturation excess overland flow, interflow, recharge, capillary rise, soil evaporation and transpiration. These processes are parameterized in hydrological models or land-surface schemes and the effect on runoff prediction can be large. For root zone parameters in global hydrological models are very uncertain as they cannot be measured directly at the scale on which these models operate. In this paper we calibrate the global hydrological model PCR-GLOBWB using a state-of-the-art ensemble of evaporation fields derived by solving the energy balance for satellite observations. We focus our calibration on the root zone parameters of PCR-GLOBWB and derive spatial patterns of maximum root zone storage. We find these patterns to correspond well with previous research. The parameterization of our model allows for the conversion of maximum root zone storage to root zone depth and we find that these correspond quite well to the point observations where available. We conclude that climate and soil type should be taken into account when regionalizing measured root depth for a certain vegetation type. We equally find that using evaporation rather than discharge better allows for local adjustment of root zone parameters within a basin and thus provides orthogonal data to diagnose and optimize hydrological models and land surface schemes.

  11. Using Wavelets to Evaluate Persistence of High Frequency Hydrologic and Hydrochemistry Signals

    NASA Astrophysics Data System (ADS)

    Koirala, S. R.; Gentry, R. W.

    2009-12-01

    In the area of sustainability science, it is becoming increasingly important to understand the basal condition of a natural system, and its long-term behavior. Research is needed to better understand the temporal scaling of hydrochemistry in streams and watersheds and its relationship to the hydrologic factors that influence its behavior. Persistence of dissolved chemicals in streams has been demonstrated to be linked to certain hydrologic processes, such as interactions between hydrologic units and storage in surface or sub-surface systems. In this study, wavelet analyses provided a novel theoretical basis for insights into long-term hydrochemistry behavior in an east Tennessee watershed. Temporal analyses were conducted on weekly time series data of hydrochemistry (nitrate, chloride, sulfate and calcium concentrations) collected from November 1995 to December 2005 at the West Fork of Walker Branch in Oak Ridge, Tennessee. Hydrochemistry plays an important role in ecosystem services, particularly nitrate, and in general the signal responses can be complex. The signals in this study were modeled using a wavelet approach as a mechanism for evaluating short-and long term temporal effects. The Walker Branch conceptual hydrology model is augmented by these results that show characteristic periodicities or structures for flowpath lengths in the vadose zone (< 20 week period), saturated zone (20 to 50 week period) and bedrock zone (> 50 week period) with implications for hydrochemistry within the watershed. In general, time series signals of watershed hydrochemistry may provide clues as to broad environmental, ecological and economic impacts at the basin scale.

  12. New Hydrologic Insights to Advance Geophysical Investigation of the Unsaturated Zone

    NASA Astrophysics Data System (ADS)

    Nimmo, J. R.; Perkins, K. S.

    2015-12-01

    Advances in hydrology require information from the unsaturated zone, especially for problems related to groundwater contamination, water-supply sustainability, and ecohydrology. Unsaturated-zone processes are notoriously difficult to quantify; soils and rocks are visually opaque, spatially variable in the extreme, and easily disturbed by instrument installation. Thus there is great value in noninvasive techniques that produce water-related data of high density in space and time. Methods based on resistivity and electromagnetic waves have already produced significant new understanding of percolation processes, root-zone water retention, influences of evapotranspiration on soil-water, and effects of preferential flow. Further developments are underway for such purposes as noninvasive application to greater depths, increased resolution, adaptation for lab-scale experiments, and calibration in heterogeneous media. Beyond these, however, there is need for a stronger marriage of hydrologic and geophysical knowledge and perspective. Possible means to greater and faster progress include: Apply the latest hydrologic understanding, both pore-scale and macroscopic, to the detection of preferential flow paths and their degree of activation. In the continuing advancement of hardware and techniques, draw creatively from developments in such fields as high-energy physics, medical imaging, astrogeology, high-tech semiconductors, and bioinstrumentation. Sidestep the imaging process where possible to measure essential properties and fluxes more directly. Pose questions that have a strong end-use character, like "how does storm intensity relate to aquifer recharge rate" rather than "what is the shape of the wetting front". The greatest advances in geophysical investigation of the unsaturated zone will come from methods informed by the latest understanding of unsaturated systems and processes, and aimed as directly as possible at the answers to important hydrologic questions.

  13. Diagnosing scaling behavior of groundwater with a fully-integrated, high resolution hydrologic model simulated over the continental US (Invited)

    NASA Astrophysics Data System (ADS)

    Maxwell, R. M.; Condon, L. E.; Kollet, S. J.

    2013-12-01

    Groundwater is an important component of the hydrologic cycle yet its importance is often overlooked. Aquifers are a critical water resource, particularly in irrigation, but also participates in moderating the land-energy balance over the so-called critical zone of 2-10m in water table depth. Yet,the scaling behavior of groundwater is not well known. Here, we present the results of a fully-integrated hydrologic model run over a 6.3M km2 domain that covers much of North America focused on the continental United States. This model encompasses both the Mississippi and Colorado River watersheds in their entirety at 1km resolution and is constructed using the fully-integrated groundwater-vadose zone-surface water-land surface model, ParFlow. Results from this work are compared to observations (both of surface water flow and groundwater depths) and approaches are presented for observing of these integrated systems. Furthermore, results are used to understand the scaling behavior of groundwater over the continent at high resolution. Implications for understanding dominant hydrological processes at large scales will be discussed.

  14. Hydrologic Synthesis Across the Critical Zone Observatory Network: A Step Towards Understanding the Coevolution of Critical Zone Function and Structure

    NASA Astrophysics Data System (ADS)

    Wlostowski, A. N.; Harman, C. J.; Molotch, N. P.

    2017-12-01

    The physical and biological architecture of the Earth's Critical Zone controls hydrologic partitioning, storage, and chemical evolution of precipitated water. The Critical Zone Observatory (CZO) Network provides an ideal platform to explore linkages between catchment structure and hydrologic function across a gradient of geologic and climatic settings. A legacy of hypothesis-motivated research at each site has generated a wealth of data characterizing the architecture and hydrologic function of the critical zone. We will present a synthesis of this data that aims to elucidate and explain (in the sense of making mutually intelligible) variations in hydrologic function across the CZO network. Top-down quantitative signatures of the storage and partitioning of water at catchment scales extracted from precipitation, streamflow, and meteorological data will be compared with each other, and provide quantitative benchmarks to assess differences in perceptual models of hydrologic function at each CZO site. Annual water balance analyses show that CZO sites span a wide gradient of aridity and evaporative partitioning. The aridity index (PET/P) ranges from 0.3 at Luquillo to 4.3 at Reynolds Creek, while the evaporative index (E/P) ranges from 0.3 at Luquillo (Rio Mamayes) to 0.9 at Reynolds Creek (Reynolds Creek Outlet). Snow depth and SWE observations reveal that snowpack is an important seasonal storage reservoir at three sites: Boulder, Jemez, Reynolds Creek and Southern Sierra. Simple dynamical models are also used to infer seasonal patterns of subsurface catchment storage. A root-zone water balance model reveals unique seasonal variations in plant-available water storage. Seasonal patterns of plant-available storage are driven by the asynchronicity of seasonal precipitation and evaporation cycles. Catchment sensitivity functions are derived at each site to infer relative changes in hydraulic storage (the apparent storage reservoir responsible for modulating streamflow

  15. A model for microbially induced precipitation of vadose-zone calcites in fractures at LOS Alamos, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Newman, Brent D.; Campbell, Andrew R.; Norman, David I.; Ringelberg, David B.

    1997-05-01

    Fractures are unique environments that can concentrate the flow of water, nutrients, and contaminants. As such, fractures play an important role in controlling the flux of various substances into and through the vadose zone. Calcite fracture fillings are present in the near surface in the Bandelier Tuff Formation at Los Alamos, New Mexico, and provide a record of the geochemical and hydrologic processes that have occurred in fractures. The objective of this study was to examine calcite fracture fills in order to improve understanding of processes within fractures, and in particular those that lead to precipitation of calcite. Samples of calcite fillings were collected from vertical and horizontal fractures exposed in a shallow waste-burial pit. Scanning electron microscopy show morphologies which suggest that plants, fungi, and bacteria were important in the precipitation process. Quadrupole mass spectrometric analyses of fluid inclusion gases show predominantly methane (17-99%) and little to no oxygen (0-8%), suggesting the development of anaerobic conditions in the fractures. Ester-linked phospholipid biomarkers are evidence for a diverse microbial community in the fractures, and the presence of di-ether lipids indicate that the methane was generated by anaerobic bacteria. The calcite fillings apparently resulted from multiple biological and chemical processes in which plant roots in the fractures were converted to calcite. Roots grew into the fractures, eventually died, and were decomposed by bacteria and fungi. Anaerobic gases were generated from encapsulated organic material within the calcite via microbial decomposition, or were generated by microbes simultaneously with calcite precipitation. It is likely that the biological controls on calcite formation that occurred in the Los Alamos fractures also occurs in soils, and may explain the occurrence of other types of pedogenic calcites.

  16. Evaluating BTEX concentration in soil using a simple one-dimensional vado zone model: application to a new fuel station in Valencia (Spain)

    NASA Astrophysics Data System (ADS)

    Rodrigo-Ilarri, Javier; Rodrigo-Clavero, María-Elena

    2017-04-01

    Specific studies of the impact of fuel spills on the vadose zone are currently required when trying to obtain the environmental permits for new fuel stations. The development of One-Dimensional mathematical models of fate and transport of BTEX on the vadose zone can therefore be used to understand the behavior of the pollutants under different scenarios. VLEACH - a simple One-Dimensional Finite Different Vadose Zone Leaching Model - uses an numerical approximation of the Millington Equation, a theoretical based model for gaseous diffusion in porous media. This equation has been widely used in the fields of soil physics and hydrology to calculate the gaseous or vapor diffusion in porous media. The model describes the movement of organic contaminants within and between three different phases: (1) as a solute dissolved in water, (2) as a gas in the vapor phase, and (3) as an absorbed compound in the soil phase. Initially, the equilibrium distribution of contaminant mass between liquid, gas and sorbed phases is calculated. Transport processes are then simulated. Liquid advective transport is calculated based on values defined by the user for infiltration and soil water content. The contaminant in the vapor phase migrates into or out of adjacent cells based on the calculated concentration gradients that exist between adjacent cells. After the mass is exchanged between the cells, the total mass in each cell is recalculated and re-equilibrated between the different phases. At the end of the simulation, (1) an overall area-weighted groundwater impact for the entire modeled area and (2) the concentration profile of BTEX on the vadose zone are calculated. This work shows the results obtained when applying VLEACH to analyze the contamination scenario caused by a BTEX spill coming from a set of future underground storage tanks located on a new fuel station in Aldaia (Valencia region - Spain).

  17. A Dynamic Hydrology-Critical Zone Framework for Rainfall-triggered Landslide Hazard Prediction

    NASA Astrophysics Data System (ADS)

    Dialynas, Y. G.; Foufoula-Georgiou, E.; Dietrich, W. E.; Bras, R. L.

    2017-12-01

    Watershed-scale coupled hydrologic-stability models are still in their early stages, and are characterized by important limitations: (a) either they assume steady-state or quasi-dynamic watershed hydrology, or (b) they simulate landslide occurrence based on a simple one-dimensional stability criterion. Here we develop a three-dimensional landslide prediction framework, based on a coupled hydrologic-slope stability model and incorporation of the influence of deep critical zone processes (i.e., flow through weathered bedrock and exfiltration to the colluvium) for more accurate prediction of the timing, location, and extent of landslides. Specifically, a watershed-scale slope stability model that systematically accounts for the contribution of driving and resisting forces in three-dimensional hillslope segments was coupled with a spatially-explicit and physically-based hydrologic model. The landslide prediction framework considers critical zone processes and structure, and explicitly accounts for the spatial heterogeneity of surface and subsurface properties that control slope stability, including soil and weathered bedrock hydrological and mechanical characteristics, vegetation, and slope morphology. To test performance, the model was applied in landslide-prone sites in the US, the hydrology of which has been extensively studied. Results showed that both rainfall infiltration in the soil and groundwater exfiltration exert a strong control on the timing and magnitude of landslide occurrence. We demonstrate the extent to which three-dimensional slope destabilizing factors, which are modulated by dynamic hydrologic conditions in the soil-bedrock column, control landslide initiation at the watershed scale.

  18. Efficient Bayesian parameter estimation with implicit sampling and surrogate modeling for a vadose zone hydrological problem

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Pau, G. S. H.; Finsterle, S.

    2015-12-01

    Parameter inversion involves inferring the model parameter values based on sparse observations of some observables. To infer the posterior probability distributions of the parameters, Markov chain Monte Carlo (MCMC) methods are typically used. However, the large number of forward simulations needed and limited computational resources limit the complexity of the hydrological model we can use in these methods. In view of this, we studied the implicit sampling (IS) method, an efficient importance sampling technique that generates samples in the high-probability region of the posterior distribution and thus reduces the number of forward simulations that we need to run. For a pilot-point inversion of a heterogeneous permeability field based on a synthetic ponded infiltration experiment simu­lated with TOUGH2 (a subsurface modeling code), we showed that IS with linear map provides an accurate Bayesian description of the parameterized permeability field at the pilot points with just approximately 500 forward simulations. We further studied the use of surrogate models to improve the computational efficiency of parameter inversion. We implemented two reduced-order models (ROMs) for the TOUGH2 forward model. One is based on polynomial chaos expansion (PCE), of which the coefficients are obtained using the sparse Bayesian learning technique to mitigate the "curse of dimensionality" of the PCE terms. The other model is Gaussian process regression (GPR) for which different covariance, likelihood and inference models are considered. Preliminary results indicate that ROMs constructed based on the prior parameter space perform poorly. It is thus impractical to replace this hydrological model by a ROM directly in a MCMC method. However, the IS method can work with a ROM constructed for parameters in the close vicinity of the maximum a posteriori probability (MAP) estimate. We will discuss the accuracy and computational efficiency of using ROMs in the implicit sampling procedure

  19. ENVIRONMENTALMANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACEMETALS INGROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 ANDOTHER DIVALENT METALS AND RADIONUCLIDES AT ARIDWESTERN DOE SITES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface ureamore » hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.« less

  20. Hydrology and Nitrogen Biogeochemistry in the Hyporheic Zone of a Geomorphically Degraded Urban Stream

    EPA Science Inventory

    Few studies have investigated the relationship between hydrology and nitrogen biogeochemistry in hyporheic zones of degraded urban streams despite significant national efforts to restore such streams. We examined relationships between hydrology and biogeochemistry in Minebank Ru...

  1. Monitoring and Data Analysis for the Vadose Zone Monitoring System (VZMS), McClellan AFB. Quarterly Status Report (2/20/98 - 5/20/98)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zawislanski, P.T.; Mountford, H.S.Monitoring and Data Analysis; for the Vadose Zone Monitoring System

    1998-06-18

    This report contains information on field and laboratory work performed between February 20th, 1998 and May 20th, 1998, at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) (LBNL, 1996) is currently being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature. This report describes: moisture content changes, based on neutron logging; gas-phase VOC concentrations; aqueous-phase VOC concentrations; temperature profiles; and installation of new instrument cluster.

  2. Current challenges in quantifying preferential flow through the vadose zone

    NASA Astrophysics Data System (ADS)

    Koestel, John; Larsbo, Mats; Jarvis, Nick

    2017-04-01

    In this presentation, we give an overview of current challenges in quantifying preferential flow through the vadose zone. A review of the literature suggests that current generation models do not fully reflect the present state of process understanding and empirical knowledge of preferential flow. We believe that the development of improved models will be stimulated by the increasingly widespread application of novel imaging technologies as well as future advances in computational power and numerical techniques. One of the main challenges in this respect is to bridge the large gap between the scales at which preferential flow occurs (pore to Darcy scales) and the scale of interest for management (fields, catchments, regions). Studies at the pore scale are being supported by the development of 3-D non-invasive imaging and numerical simulation techniques. These studies are leading to a better understanding of how macropore network topology and initial/boundary conditions control key state variables like matric potential and thus the strength of preferential flow. Extrapolation of this knowledge to larger scales would require support from theoretical frameworks such as key concepts from percolation and network theory, since we lack measurement technologies to quantify macropore networks at these large scales. Linked hydro-geophysical measurement techniques that produce highly spatially and temporally resolved data enable investigation of the larger-scale heterogeneities that can generate preferential flow patterns at pedon, hillslope and field scales. At larger regional and global scales, improved methods of data-mining and analyses of large datasets (machine learning) may help in parameterizing models as well as lead to new insights into the relationships between soil susceptibility to preferential flow and site attributes (climate, land uses, soil types).

  3. Scientific realism and wishful thinking in soil hydrology

    NASA Astrophysics Data System (ADS)

    Flühler, H.

    2009-04-01

    In our field we often learn - or could have learned - more from failures than from successes provided we had postulated testable hypotheses to be accepted or rejected. In soil hydrology, hypotheses are testable if independent information quantifying the pertinent system features is at hand. This view on how to operate is an idealized concept of how we could or should have worked. In reality, the path to success is more tortuous and we usually progress differently obeying to other professional musts. Although we missed some shortcuts over the past few decades, we definitely made significant progress in understanding vadose zone progresses, but we could have advanced our system understanding faster by more rigorously questioning the fundamental assumptions. I will try to illustrate the tortuous path of learning and identify some causes of the slowed-down learning curve. In the pioneering phase of vadose zone research many models have been mapped in our minds and implemented on our computers. Many of them are now well established, powerful and represent the state-of-the-art even when they do not work. Some of them are based on erroneous or misleading concepts. Even when based on adequate concepts they might have been applied in the wrong context or inadequate models may have lead to apparent success. I address this process of collective learning with the intention that we spend more time and efforts to find the right question instead of improving tools, which are questionably suitable for solving the main problems.

  4. Transport of europium colloids in vadose zone lysimeters at the semiarid Hanford site.

    PubMed

    Liu, Ziru; Flury, Markus; Zhang, Z Fred; Harsh, James B; Gee, Glendon W; Strickland, Chris E; Clayton, Ray E

    2013-03-05

    The objective of this study was to quantify transport of Eu colloids in the vadose zone at the semiarid Hanford site. Eu-hydroxy-carbonate colloids, Eu(OH)(CO3), were applied to the surface of field lysimeters, and migration of the colloids through the sediments was monitored using wick samplers. The lysimeters were exposed to natural precipitation (145-231 mm/year) or artificial irrigation (124-348 mm/year). Wick outflow was analyzed for Eu concentrations, supplemented by electron microscopy and energy-dispersive X-ray analysis. Small amounts of Eu colloids (<1%) were detected in the deepest wick sampler (2.14 m depth) 2.5 months after application and cumulative precipitation of only 20 mm. We observed rapid transport of Eu colloids under both natural precipitation and artificial irrigation; that is, the leading edge of the Eu colloids moved at a velocity of 3 cm/day within the first 2 months after application. Episodic infiltration (e.g., Chinook snowmelt events) caused peaks of Eu in the wick outflow. While a fraction of Eu moved consistent with long-term recharge estimates at the site, the main mass of Eu remained in the top 30 cm of the sediments. This study illustrates that, under field conditions, near-surface colloid mobilization and transport occurred in Hanford sediments.

  5. An integrated monitoring network for hydrologic, geochemical, and sediment fluxes to characterize carbon-mineral fate in the Christina River Basin Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Karwan, D. L.; Lazareva, O.

    2011-12-01

    Organic carbon (C) -mineral complexation mechanism plays an important role in C sequestration within watersheds. The primary goal of the Christina River Basin Critical Zone Observatory in SE Pennsylvania and N Delaware, USA (one of six National Science Foundation-funded observatories) is to quantify net carbon sink or source due to mineral production and transport and its dependence on land use. This effort requires an interdisciplinary understanding of carbon and mineral fluxes across interfaces between soil, aquifer, floodplain, and river. We have established a monitoring network that targets hydrologic, geochemical, and sedimentological transport processes across channel-floodplain-aquifer interfaces within White Clay Creek Watershed. Within the channel, suspended material is sampled and analyzed for organic and mineral composition as well as geochemical fingerprints. Surface water and groundwater are analyzed for C, Fe, and Mn chemistry. Within the floodplain, in-situ sensors monitor soil moisture, pressure, temperature, conductivity, and redox potential. Integrated data analysis should yield estimates of water and solute fluxes between the vadose zone, riparian aquifer, and stream. Our preliminary data show that storm events are important for carbon and mineral fluxes-suspended material in surface water changes in source and composition throughout the storm. Meanwhile, the variation in stream stage drives surface water-groundwater exchange, facilitating changes in redox potential and providing opportunity for enhanced transport and reactions involving C, Fe, and Mn in the riparian aquifer.

  6. Pedotransfer functions for isoproturon sorption on soils and vadose zone materials.

    PubMed

    Moeys, Julien; Bergheaud, Valérie; Coquet, Yves

    2011-10-01

    Sorption coefficients (the linear K(D) or the non-linear K(F) and N(F)) are critical parameters in models of pesticide transport to groundwater or surface water. In this work, a dataset of isoproturon sorption coefficients and corresponding soil properties (264 K(D) and 55 K(F)) was compiled, and pedotransfer functions were built for predicting isoproturon sorption in soils and vadose zone materials. These were benchmarked against various other prediction methods. The results show that the organic carbon content (OC) and pH are the two main soil properties influencing isoproturon K(D) . The pedotransfer function is K(D) = 1.7822 + 0.0162 OC(1.5) - 0.1958 pH (K(D) in L kg(-1) and OC in g kg(-1)). For low-OC soils (OC < 6.15 g kg(-1)), clay and pH are most influential. The pedotransfer function is then K(D) = 0.9980 + 0.0002 clay - 0.0990 pH (clay in g kg(-1)). Benchmarking K(D) estimations showed that functions calibrated on more specific subsets of the data perform better on these subsets than functions calibrated on larger subsets. Predicting isoproturon sorption in soils in unsampled locations should rely, whenever possible, and by order of preference, on (a) site- or soil-specific pedotransfer functions, (b) pedotransfer functions calibrated on a large dataset, (c) K(OC) values calculated on a large dataset or (d) K(OC) values taken from existing pesticide properties databases. Copyright © 2011 Society of Chemical Industry.

  7. The evolution of root zone moisture storage capacities after deforestation: a step towards hydrological predictions under change?

    NASA Astrophysics Data System (ADS)

    Nijzink, Remko C.; Hutton, Christopher; Pechlivanidis, Ilias; Capell, René; Arheimer, Berit; Freer, Jim; Han, Dawei; Wagener, Thorsten; McGuire, Kevin; Savenije, Hubert; Hrachowitz, Markus

    2017-04-01

    The moisture storage available to vegetation is a key parameter in the hydrological functioning of ecosystems. This parameter, the root zone storage capacity, determines the partitioning between runoff and transpiration, but is impossible to observe at the catchment scale. In this research, data from the experimental forests of HJ Andrews (Oregon, USA) and Hubbard Brook (New Hampshire, USA) was used to test the hypotheses that: (1) the root zone storage capacity significantly changes after deforestation, (2) changes in the root zone storage capacity can to a large extent explain post-treatment changes to the hydrological regimes and that (3) a time-dynamic formulation of the root zone storage can improve the performance of a hydrological model. At first, root zone storage capacities were estimated based on a simple, water-balance based method. Briefly, the maximum difference between cumulative rainfall and estimated transpiration was determined, which could be considered a proxy for root zone storage capacity. These values were compared with root zone storage capacities obtained from four conceptual models (HYPE, HYMOD, FLEX, TUW), calibrated for consecutive 2-year windows. Both methods showed a sharp decline in root zone storage capacity after deforestation, which was followed by a gradual recovery signal. It was found in a trend analysis that these recovery periods took between 5 and 13 years for the different catchments. Eventually, one of the models was adjusted to allow for a time-dynamic formulation of root zone storage capacity. This adjusted model showed improvements in model performance as evaluated by 28 hydrological signatures, such as rising limb density or peak flows. Thus, this research clearly shows the time-dynamic character of a crucial parameter, which is often considered to remain constant in time. Root zone storage capacities are strongly affected by deforestation, leading to changes in hydrological regimes, and time-dynamic formulations of root

  8. Hydrologically Controlled Arsenic Release in Deltaic Wetlands and Coastal Riparian Zones

    NASA Astrophysics Data System (ADS)

    Stuckey, J.; LeMonte, J. J.; Yu, X.; Schaefer, M.; Kocar, B. D.; Benner, S. G.; Rinklebe, J.; Tappero, R.; Michael, H. A.; Fendorf, S. E.; Sparks, D. L.

    2016-12-01

    Wetland and riparian zone hydrology exerts critical controls on the biogeochemical cycling of metal contaminants including arsenic. The role of wetlands in driving geogenic arsenic release to groundwater has been debated in the deltas of South and Southeast Asia where the largest impacted human population resides. In addition, groundwater in coastal areas worldwide, such as those in South and Southeast Asia and the Mid-Atlantic of the U.S., is at risk to largely unexplored biogeochemical and hydrologic impacts of projected sea level rise. First, we present data from fresh-sediment incubations, in situ model sediment incubations and a controlled field experiment with manipulated wetland hydrology and organic carbon inputs in the minimally disturbed upper Mekong Delta. Here we show that arsenic release is limited to near-surface sediments of permanently saturated wetlands where both organic carbon and arsenic-bearing solids are sufficiently reactive for microbial oxidation of organic carbon and reduction of arsenic-bearing iron oxides. In contrast, within the deeper aquifer or seasonally saturated sediments, reductive dissolution of iron oxides is observed only when either more reactive exogenous forms of iron oxides or organic carbon are added, revealing a potential thermodynamic restriction to microbial metabolism. Second, in order to assess the potential impacts of sea level rise on arsenic release to groundwater, we determined the changes in arsenic speciation and partitioning in sediment collected from an anthropogenically contaminated coastal riparian zone under controlled Eh regimes in both seawater and freshwater systems. Here we show greater arsenic release under anoxic/suboxic conditions in the freshwater system than in the seawater system, potentially due to high salinity induced microbial inhibition. Collectively, our work shows that shifting hydrologic conditions in deltaic wetlands and tidally influenced zones impacts the extent of arsenic release to

  9. Persistence of Hydrologic Variables and Reactive Stream Solute Concentrations in an East Tennessee Watershed

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koirala, Shesh R; Gentry, Randall W; Mulholland, Patrick J

    2011-01-01

    Time and frequency domain analyses were conducted on weekly time series of water chemistry (nitrate, sulfate and calcium concentrations) collected from November 1995 to December 2005 at the West Fork of Walker Branch in Oak Ridge, Tennessee to evaluate the extent of their persistence and the relationship of this persistence to discharge and rainfall. In this study, spectral and wavelet analyses provided a theoretical basis for insights into long-term water chemistry behavior. All water chemistry parameters showed some level of persistence that was influenced by rainfall and/or discharge. Short-term persistence (less than a year) was related to the persistence ofmore » rainfall and discharge, whereas long-term persistence (more than a year) was related to the persistence of discharge. The Walker Branch conceptual hydrology model is augmented by these results that relate characteristic periodicities with flowpaths through different zones: the vadose zone (< 20 week period), saturated zone (20-50 week period) and bedrock zone (> 50 week period) with implications for reactive chemistries within the watershed. (C) 2011 Elsevier B.V. All rights reserved.« less

  10. Biogeochemical Factors Influencing the Transport and Fate of Colloids and Colloid-Associated Contaminants in the Vadose Zone

    NASA Astrophysics Data System (ADS)

    Bradford, S. A.

    2016-12-01

    The vadose zone exhibits large spatial and temporal variability in many physical, chemical, and biological factors that strongly influence the transport and fate of colloids (e.g., microbes, nanoparticles, clays, and dissolved organic matter) and colloid-associated contaminants (e.g., heavy metals, radionuclides, pesticides, and antibiotics). This presentation highlights our research activities to better understand and predict the influence of specific biogeochemical processes on colloid and colloid-facilitated transport. Results demonstrate the sensitivity of colloid transport, retention, release, and clogging to transients in solution chemistry (e.g., ionic strength, pH, cation and anion type, and surfactants), water velocity and saturation, and preferential flow. Mathematical modeling at interface-, pore-, and continuum-scales is shown to be a critical tool to quantify the relative importance and coupling of these biogeochemical factors on colloid and contaminant transport and fate, which otherwise might be experimentally intractable. Existing gaps in knowledge and model limitations are identified.

  11. Effects of agricultural practices and vadose zone stratigraphy on nitrate concentration in ground water in Kansas, USA

    USGS Publications Warehouse

    Townsend, M.A.; Sleezer, R.O.; Macko, S.A.; ,

    1996-01-01

    Differences in nitrate-N concentrations in,around water in Kansas can be explained by variations in agricultural practices and vadose-zone stratigraphy. In northwestern Kansas, past use of a local stream for tailwater runoff from irrigation and high fertilizer applications for sugar-beet farming resulted in high nitrate-N concentrations (12-60 mg L-1; in both soil and ground water. Nitrogen isotope values from the soil and ground water range from +4 to +8? which is typical for a fertilizer source. In parts of south-central Kansas, the use of crop rotation and the presence of both continuous fine-textured layers and a reducing ground-water chemistry resulted in ground-water nitrate-N values of 10 mg L-1; in both soil and grounwater. Nitrogen isotope values of +3 to +7? indicate a fertilizer source. Crop rotation decreased nitrate-N values in the shallow ground water (9 m). However, deeper ground water showed increasing nitrate-N concentrations as a result of past farming practices.

  12. Remediation of Uranium in the Hanford Vadose Zone Using Gas-Transported Reactants: Laboratory Scale Experiments in Support of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szecsody, James E.; Truex, Michael J.; Zhong, Lirong

    2010-01-04

    This laboratory-scale investigation is focused on decreasing mobility of uranium in subsurface contaminated sediments in the vadose zone by in situ geochemical manipulation at low water content. This geochemical manipulation of the sediment surface phases included reduction, pH change (acidic and alkaline), and additions of chemicals (phosphate, ferric iron) to form specific precipitates. Reactants were advected into 1-D columns packed with Hanford 200 area U-contaminated sediment as a reactive gas (for CO2, NH3, H2S, SO2), with a 0.1% water content mist (for NaOH, Fe(III), HCl, PO4) and with a 1% water content foam (for PO4). Uranium is present in themore » sediment in multiple phases that include (in decreasing mobility): aqueous U(VI) complexes, adsorbed U, reduced U(IV) precipitates, rind-carbonates, total carbonates, oxides, silicates, phosphates, and in vanadate minerals. Geochemical changes were evaluated in the ability to change the mixture of surface U phases to less mobile forms, as defined by a series of liquid extractions that dissolve progressively less soluble phases. Although liquid extractions provide some useful information as to the generalized uranium surface phases (and are considered operational definitions of extracted phases), positive identification (by x-ray diffraction, electron microprobe, other techniques) was also used to positively identify U phases and effects of treatment. Some of the changes in U mobility directly involve U phases, whereas other changes result in precipitate coatings on U surface phases. The long-term implication of the U surface phase changes to alter U mass mobility in the vadose zone was then investigated using simulations of 1-D infiltration and downward migration of six U phases to the water table. In terms of the short-term decrease in U mobility (in decreasing order), NH3, NaOH mist, CO2, HCl mist, and Fe(III) mist showed 20% to 35% change in U surface phases. Phosphate addition (mist or foam advected

  13. Hydrological partitioning in the critical zone: Recent advances and opportunities for developing transferable understanding of water cycle dynamics

    NASA Astrophysics Data System (ADS)

    Brooks, Paul D.; Chorover, Jon; Fan, Ying; Godsey, Sarah E.; Maxwell, Reed M.; McNamara, James P.; Tague, Christina

    2015-09-01

    Hydrology is an integrative discipline linking the broad array of water-related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy to the base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross-site focus on "critical zone hydrology" has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: "how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?" Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning.

  14. Hydrological partitioning in the critical zone: Recent advances and opportunities for developing transferable understanding of water cycle dynamics

    DOE PAGES

    Brooks, Paul D.; Chorover, Jon; Fan, Ying; ...

    2015-08-07

    Here, hydrology is an integrative discipline linking the broad array of water–related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy tomore » the base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross–site focus on “critical zone hydrology” has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: “how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?” Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning.« less

  15. VAPOR-PHASE TRANSPORT OF TRICHLOROETHENE IN AN INTERMEDIATE-SCALE VADOSE-ZONE SYSTEM: RETENTION PROCESSES AND TRACER-BASED PREDICTION

    PubMed Central

    Costanza-Robinson, Molly S.; Carlson, Tyson D.; Brusseau, Mark L.

    2013-01-01

    Gas-phase miscible-displacement experiments were conducted using a large weighing lysimeter to evaluate retention processes for volatile organic compounds (VOCs) in water-unsaturated (vadoze-zone) systems, and to test the utility of gas-phase tracers for predicting VOC retardation. Trichloroethene (TCE) served as a model VOC, while trichlorofluoromethane (CFM) and heptane were used as partitioning tracers to independently characterize retention by water and the air-water interface, respectively. Retardation factors for TCE ranged between 1.9 and 3.5, depending on water content. The results indicate that dissolution into the bulk water was the primary retention mechanism for TCE under all conditions studied, contributing approximately two thirds of the total measured retention. Accumulation at the air-water interface comprised a significant fraction of the observed retention for all experiments, with an average contribution of approximately 24%. Sorption to the solid phase contributed approximately 10% to retention. Water contents and air-water interfacial areas estimated based on the CFM and heptane tracer data, respectively, were similar to independently measured values. Retardation factors for TCE predicted using the partitioning-tracer data were in reasonable agreement with the measured values. These results suggest that gas-phase tracer tests hold promise for characterizing the retention and transport of VOCs in the vadose-zone. PMID:23333418

  16. Superfund Record of Decision (EPA Region 9): El Toro Marine Corps Air Station, Operable Unit 2A (Site 24-VOC source area vadose zone), El Toro, CA, September 29, 1997

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    This Interim Record of Decision (ROD) presents the selected remedial action for vadose zone soil at Site 24 at Marine Corps Air Station (MCAS) El Toro, located in El Toro, California. The selected remedy for remediation of soil at Site 24 is soil vapor extraction (SVE), the US EPA presumptive remedy for VOC-contaminated soil. The process uses a vacuum to pull VOC-contaminated vapors from the soil through SVE wells.

  17. Vadose zone monitoring strategies to control water flux dynamics and changes in soil hydraulic properties.

    NASA Astrophysics Data System (ADS)

    Valdes-Abellan, Javier; Jiménez-Martínez, Joaquin; Candela, Lucila

    2013-04-01

    For monitoring the vadose zone, different strategies can be chosen, depending on the objectives and scale of observation. The effects of non-conventional water use on the vadose zone might produce impacts in porous media which could lead to changes in soil hydraulic properties, among others. Controlling these possible effects requires an accurate monitoring strategy that controls the volumetric water content, θ, and soil pressure, h, along the studied profile. According to the available literature, different monitoring systems have been carried out independently, however less attention has received comparative studies between different techniques. An experimental plot of 9x5 m2 was set with automatic and non-automatic sensors to control θ and h up to 1.5m depth. The non-automatic system consisted of ten Jet Fill tensiometers at 30, 45, 60, 90 and 120 cm (Soil Moisture®) and a polycarbonate access tube of 44 mm (i.d) for soil moisture measurements with a TRIME FM TDR portable probe (IMKO®). Vertical installation was carefully performed; measurements with this system were manual, twice a week for θ and three times per week for h. The automatic system composed of five 5TE sensors (Decagon Devices®) installed at 20, 40, 60, 90 and 120 cm for θ measurements and one MPS1 sensor (Decagon Devices®) at 60 cm depth for h. Installation took place laterally in a 40-50 cm length hole bored in a side of a trench that was excavated. All automatic sensors hourly recorded and stored in a data-logger. Boundary conditions were controlled with a volume-meter and with a meteorological station. ET was modelled with Penman-Monteith equation. Soil characterization include bulk density, gravimetric water content, grain size distribution, saturated hydraulic conductivity and soil water retention curves determined following laboratory standards. Soil mineralogy was determined by X-Ray difractometry. Unsaturated soil hydraulic parameters were model-fitted through SWRC-fit code and

  18. ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface ureamore » hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.« less

  19. Persistence of uranium groundwater plumes: contrasting mechanisms at two DOE sites in the groundwater-river interaction zone.

    PubMed

    Zachara, John M; Long, Philip E; Bargar, John; Davis, James A; Fox, Patricia; Fredrickson, Jim K; Freshley, Mark D; Konopka, Allan E; Liu, Chongxuan; McKinley, James P; Rockhold, Mark L; Williams, Kenneth H; Yabusaki, Steve B

    2013-04-01

    We examine subsurface uranium (U) plumes at two U.S. Department of Energy sites that are located near large river systems and are influenced by groundwater-river hydrologic interaction. Following surface excavation of contaminated materials, both sites were projected to naturally flush remnant uranium contamination to levels below regulatory limits (e.g., 30 μg/L or 0.126 μmol/L; U.S. EPA drinking water standard), with 10 years projected for the Hanford 300 Area (Columbia River) and 12 years for the Rifle site (Colorado River). The rate of observed uranium decrease was much lower than expected at both sites. While uncertainty remains, a comparison of current understanding suggests that the two sites have common, but also different mechanisms controlling plume persistence. At the Hanford 300 A, the persistent source is adsorbed U(VI) in the vadose zone that is released to the aquifer during spring water table excursions. The release of U(VI) from the vadose zone and its transport within the oxic, coarse-textured aquifer sediments is dominated by kinetically-limited surface complexation. Modeling implies that annual plume discharge volumes to the Columbia River are small (zone and a continuous influx of U(VI) from natural, up-gradient sources influence plume persistence. Rate-limited mass transfer and surface complexation also control U(VI) migration velocity in the sub-oxic Rifle groundwater. Flux of U(VI) from the vadose zone at the Rifle site may be locally important, but it is not the dominant process that sustains the plume. A wide range in microbiologic functional diversity exists at both sites. Strains of Geobacter and other metal reducing bacteria are present at low natural abundance that are capable of enzymatic U(VI) reduction in localized zones of accumulated detrital organic carbon or after organic carbon amendment. Major differences between the

  20. Persistence of uranium groundwater plumes: Contrasting mechanisms at two DOE sites in the groundwater-river interaction zone

    NASA Astrophysics Data System (ADS)

    Zachara, John M.; Long, Philip E.; Bargar, John; Davis, James A.; Fox, Patricia; Fredrickson, Jim K.; Freshley, Mark D.; Konopka, Allan E.; Liu, Chongxuan; McKinley, James P.; Rockhold, Mark L.; Williams, Kenneth H.; Yabusaki, Steve B.

    2013-04-01

    We examine subsurface uranium (U) plumes at two U.S. Department of Energy sites that are located near large river systems and are influenced by groundwater-river hydrologic interaction. Following surface excavation of contaminated materials, both sites were projected to naturally flush remnant uranium contamination to levels below regulatory limits (e.g., 30 μg/L or 0.126 μmol/L; U.S. EPA drinking water standard), with 10 years projected for the Hanford 300 Area (Columbia River) and 12 years for the Rifle site (Colorado River). The rate of observed uranium decrease was much lower than expected at both sites. While uncertainty remains, a comparison of current understanding suggests that the two sites have common, but also different mechanisms controlling plume persistence. At the Hanford 300 A, the persistent source is adsorbed U(VI) in the vadose zone that is released to the aquifer during spring water table excursions. The release of U(VI) from the vadose zone and its transport within the oxic, coarse-textured aquifer sediments is dominated by kinetically-limited surface complexation. Modeling implies that annual plume discharge volumes to the Columbia River are small (< one pore volume). At the Rifle site, slow oxidation of naturally reduced, contaminant U(IV) in the saturated zone and a continuous influx of U(VI) from natural, up-gradient sources influence plume persistence. Rate-limited mass transfer and surface complexation also control U(VI) migration velocity in the sub-oxic Rifle groundwater. Flux of U(VI) from the vadose zone at the Rifle site may be locally important, but it is not the dominant process that sustains the plume. A wide range in microbiologic functional diversity exists at both sites. Strains of Geobacter and other metal reducing bacteria are present at low natural abundance that are capable of enzymatic U(VI) reduction in localized zones of accumulated detrital organic carbon or after organic carbon amendment. Major differences between

  1. Sr-90 Immobilization by Infiltration of a Ca-Citrate-PO4 Solution into the Hanford 100-N Area Vadose Zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szecsody, Jim E.; Fruchter, Jonathan S.; Burns, Carolyn A.

    This project was initiated to develop a strategy for infiltration of a Ca-citrate-PO4 solution in order to precipitate apatite [Ca6(PO4)10(OH)2] in desired locations in the vadose zone for Sr-90 remediation. Laboratory experiments have demonstrated that infiltration of a Ca-citrate-PO4 solution into sediments at low and high water saturation results in citrate biodegradation and formation of apatite. The citrate biodegradation rate was relatively uniform, in spite of the spatial variability of sediment microbial biomass, likely because of microbial transport processes that occur during solution infiltration. The precipitate was characterized as hydroxyapatite, and the Sr-90 substitution into apatite was shown to havemore » a half-life of 5.5 to 16 months. 1-D and 2-D laboratory infiltration experiments quantified the spatial distribution of apatite that formed during solution infiltration. Slow infiltration in 2-D experiments at low water saturation show the apatite precipitate concentrated in the upper third of the infiltration zone. More rapid 1-D infiltration studies show the apatite precipitate concentrated at greater depth.« less

  2. Vapor Intrusion Estimation Tool for Unsaturated Zone Contaminant Sources. User’s Guide

    DTIC Science & Technology

    2016-08-30

    324449 Page Intentionally Left Blank iii Executive Summary Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants...strength and location, vadose zone transport, and a model for estimating movement of soil -gas vapor contamination into buildings. The tool may be...framework for estimating the impact of a vadose zone contaminant source on soil gas concentrations and vapor intrusion into a building

  3. From the surface to the deep critical zone: Linking soil carbon, fluid saturation and weathering rate

    NASA Astrophysics Data System (ADS)

    Druhan, Jennifer; Lawrence, Corey; Oster, Jessica; Rempe, Daniella; Dietrich, William

    2017-04-01

    Shallow soils from a wide range of ecosystems demonstrate a clear and consistent relationship between effective fluid saturation and the rate at which organic carbon is converted to CO2. While the underlying mechanisms contributing to this dependence are diverse, a consistent pattern of maximum CO2 production at intermediate soil moisture supports a generalized functional relationship, which may be incorporated into a quantitative reactive transport framework. A key result of this model development is a prediction of the extent to which the inorganic carbon content of water in biologically active soils varies as a function of hydrologic parameters (i.e. moisture content and residence time), and in turn influences weathering reactions. Deeper in the CZ, the consistency of this relationship and the influence of hydrologically - regulated CO2 production on the rates of water - rock interaction are largely unknown. Here, we use a novel reactive transport model incorporating this functional relationship to consider how variations in the reactive potential of water entering the vadose zone influences subsurface weathering rates. We leverage two examples of variably saturated natural systems to consider (1) CO2 production and associated weathering potential regulated by seasonal hydrologic shifts and (2) the preservation of soil carbon signatures in the deep CZ over millennial timescales. First, at the Eel River CZ Observatory in Northern California, USA, a novel Vadose Zone Monitoring System (VMS) installed in a 14 - 20 m thick unsaturated section offers an unprecedented view into the physical, chemical and biological behavior of the depth profile separating soils from groundwater. Based on soil moisture, gas and fluid phase samples, we demonstrate a predictive relationship between seasonal hydrologic variations and the location and magnitude of geochemical weathering rates. Second, an environmental monitoring project in the Blue Springs Cave, Sparta, TN, USA, provides

  4. Geomorphological control on variably saturated hillslope hydrology and slope instability

    USGS Publications Warehouse

    Giuseppe, Formetta; Simoni, Silvia; Godt, Jonathan W.; Lu, Ning; Rigon, Riccardo

    2016-01-01

    In steep topography, the processes governing variably saturated subsurface hydrologic response and the interparticle stresses leading to shallow landslide initiation are physically linked. However, these processes are usually analyzed separately. Here, we take a combined approach, simultaneously analyzing the influence of topography on both hillslope hydrology and the effective stress fields within the hillslope itself. Clearly, runoff and saturated groundwater flow are dominated by gravity and, ultimately, by topography. Less clear is how landscape morphology influences flows in the vadose zone, where transient fluxes are usually taken to be vertical. We aim to assess and quantify the impact of topography on both saturated and unsaturated hillslope hydrology and its effects on shallow slope stability. Three real hillslope morphologies (concave, convex, and planar) are analyzed using a 3-D, physically based, distributed model coupled with a module for computation of the probability of failure, based on the infinite slope assumption. The results of the analyses, which included parameter uncertainty analysis of the results themselves, show that convex and planar slopes are more stable than concave slopes. Specifically, under the same initial, boundary, and infiltration conditions, the percentage of unstable areas ranges from 1.3% for the planar hillslope, 21% for convex, to a maximum value of 33% for the concave morphology. The results are supported by a sensitivity analysis carried out to examine the effect of initial conditions and rainfall intensity.

  5. Sr-90 Immobilization by Infiltration of a Ca-Citrate-PO{sub 4} Solution into the Hanford 100-N Area Vadose Zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szecsody, J.E.; Fruchter, J.S.; Burns, C.A.

    This project was initiated to develop a strategy for infiltration of a Ca-citrate-PO{sub 4} solution in order to precipitate apatite [Ca{sub 6}(PO{sub 4}){sub 10}(OH){sub 2}] in desired locations in the vadose zone for Sr-90 remediation. Laboratory experiments have demonstrated that infiltration of a Ca-citrate-PO{sub 4} solution into sediments at low and high water saturation results in citrate biodegradation and formation of apatite. The citrate biodegradation rate was relatively uniform, in spite of the spatial variability of sediment microbial biomass, likely because of microbial transport processes that occur during solution infiltration. The precipitate was characterized as hydroxyapatite, and the Sr-90 substitutionmore » into apatite was shown to have an incorporation half-life of 5.5 to 16 months. One and two dimensional (1-D and 2-D) laboratory infiltration experiments quantified the spatial distribution of apatite that formed during solution infiltration. Slow infiltration in 2-D experiments at low water saturation show the apatite precipitate concentrated in the upper third of the infiltration zone. More rapid 1-D infiltration studies show the apatite precipitate concentrated at greater depth. (authors)« less

  6. Fate of trace organic compounds during vadose zone soil treatment in an onsite wastewater system

    USGS Publications Warehouse

    Conn, K.E.; Siegrist, R.L.; Barber, L.B.; Meyer, M.T.

    2010-01-01

    During onsite wastewater treatment, trace organic compounds are often present in the effluents applied to subsurface soils for advanced treatment during vadose zone percolation and groundwater recharge. The fate of the endocrine-disrupting surfactant metabolites 4-nonylphenol (NP), 4-nonylphenolmonoethoxylate (NP1EO), and 4-nonylphenolmonoethoxycarboxylate (NP1EC), metal-chelating agents ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), antimicrobial agent triclosan, stimulant caffeine, and antibiotic sulfamethoxazole during transport through an unsaturated sandy loam soil was studied at a field-scale test site. To assess the effects of effluent quality and hydraulic loading rate (HLR) on compound fate in the soil profile, two effluents (septic tank or textile biofilter) were applied at two design HLRs (2 or 8 cm/d). Chemical concentrations were determined in the two effluents and soil pore water at 60, 120, and 240 cm below the soil infiltrative surface. Concentrations of trace organic compounds in septic tank effluent were reduced by more than 90% during transport through 240 cm (often within 60 cm) of soil, likely due to sorption and biotransformation. However, the concentration of NP increased with depth in the shallow soil profile. Additional treatment of anaerobic septic tank effluent with an aerobic textile biofilter reduced effluent concentrations of many compounds, but generally did not affect any changes in pore water concentrations. The soil profile receiving septic tank effluent (vs. textile biofilter effluent) generally had greater percent removal efficiencies. EDTA, NP, NP1EC, and sulfamethoxazole were measured in soil pore water, indicating the ability of some trace organic compounds to reach shallow groundwater. Risk is highly dependent on the degree of further treatment in the saturated zone and the types and proximity of uses for the receiving groundwater environment. ?? 2009 SETAC.

  7. Fate of trace organic compounds during vadose zone soil treatment in an onsite wastewater system.

    PubMed

    Conn, Kathleen E; Siegrist, Robert L; Barber, Larry B; Meyer, Michael T

    2010-02-01

    During onsite wastewater treatment, trace organic compounds are often present in the effluents applied to subsurface soils for advanced treatment during vadose zone percolation and groundwater recharge. The fate of the endocrine-disrupting surfactant metabolites 4-nonylphenol (NP), 4-nonylphenolmonoethoxylate (NP1EO), and 4-nonylphenolmonoethoxycarboxylate (NP1EC), metal-chelating agents ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), antimicrobial agent triclosan, stimulant caffeine, and antibiotic sulfamethoxazole during transport through an unsaturated sandy loam soil was studied at a field-scale test site. To assess the effects of effluent quality and hydraulic loading rate (HLR) on compound fate in the soil profile, two effluents (septic tank or textile biofilter) were applied at two design HLRs (2 or 8 cm/d). Chemical concentrations were determined in the two effluents and soil pore water at 60, 120, and 240 cm below the soil infiltrative surface. Concentrations of trace organic compounds in septic tank effluent were reduced by more than 90% during transport through 240 cm (often within 60 cm) of soil, likely due to sorption and biotransformation. However, the concentration of NP increased with depth in the shallow soil profile. Additional treatment of anaerobic septic tank effluent with an aerobic textile biofilter reduced effluent concentrations of many compounds, but generally did not affect any changes in pore water concentrations. The soil profile receiving septic tank effluent (vs. textile biofilter effluent) generally had greater percent removal efficiencies. EDTA, NP, NP1EC, and sulfamethoxazole were measured in soil pore water, indicating the ability of some trace organic compounds to reach shallow groundwater. Risk is highly dependent on the degree of further treatment in the saturated zone and the types and proximity of uses for the receiving groundwater environment. Copyright 2009 SETAC.

  8. The Impact of Biochar on Bioretention Nitrogen Removal and Hydrologic Performance

    NASA Astrophysics Data System (ADS)

    Tian, J.; Jin, J.; Chiu, P.; Guo, M.; Imhoff, P. T.

    2016-12-01

    Poor nitrate removal and substantial land occupation are two factors that limit the application of bioretention facilities. Biochar was evaluated in this study as an amendment of bioretention media to enhance nitrogen removal from runoff as well as improve hydrologic performance. Two pilot-scale bioretention cells (91 cm dia., 1.2 m deep) were constructed in parallel, and both contained 20 cm saturation zone with coarse sand, 76 cm vadose zone with treatment medium, and 5 cm of triple-shredded wood mulch from bottom to top. Treatment medium in the control cell was a mixture of 88% sand, 8% clay, and 4% sawdust by mass, while the biochar cell amended 4% commercial biochar pyrolyzed from Southern Yellow Pine at 550°. Both cells were instrumented with soil moisture sensors, soil potential sensors and temperature sensors. A field infiltration test was conducted in each cell using a tension disc infiltrometer directly on the treatment media to obtain soil hydraulic parameters, then three 24-36-hour tracer tests containing bromide and nitrate pollutant were conducted over a five-month period. Influent, effluent and pore water were continuously sampled for bromide and nitrogen analysis during these tests. In addition, hydrologic performance of the two cells under various conditions of rainfall recurrence interval and duration were simulated using HYDRUS-1D after verification with tracer test data. Results showed that the biochar cell reduced NO3-N concentrations by 30.6-84.7%, while the control cell only reduced NO3-N by -6-43.5%, depending on the storm. Biochar amendment slightly increased the average pH of the vadose zone from 6.3 to 7.3, decreased the average dissolve oxygen content by 43%, and decreased the average oxidation-reduction potential from 22 mV to -115 mV, which contributed to the enhanced nitrate removal. Biochar-amended medium increased saturated hydraulic conductivity by 1.5 times, and increased cell residence time and water retention by 12.6% and 15

  9. Water, heat, and vapor flow in a deep vadose zone under arid and hyper-arid conditions: a numerical study.

    NASA Astrophysics Data System (ADS)

    Madi, Raneem; de Rooij, Gerrit H.

    2017-04-01

    Groundwater recharge in arid regions is notoriously difficult to quantify. One reason is data scarcity: reliable weather records (rainfall, potential evapotranspiration rate, temperature) are typically lacking, the soil properties over the entire extent of the often very deep vadose zone are usually unknown, and the effect of sparse vegetation, wadis, (biological) soil crusts, and hard pans on infiltration and evaporation is difficult to quantify. Another reason is the difficulty of modeling the intricately coupled relevant processes over extended periods of time: coupled flow of liquid water, water vapor, and heat in a very deep soil in view of considerable uncertainty at the soil surface as indicated above, and over large spatial extents. In view of this myriad of problems, we limited ourselves to the simulation of 1-dimensional coupled flow of water, heat, and vapor in an unvegetated deep vadose zone. The conventional parameterizations of the soil hydraulic properties perform poorly under very dry conditions. We therefore selected an alternative that was developed specifically for dry circumstances and modified another to eliminate the physically implausible residual water content that rendered it of limited use for desert environments. The issue of data scarcity was resolved by using numerically generated rainfall records combined with a simple model for annual and daily temperature fluctuations. The soil was uniform, and the groundwater depth was constant at 100 m depth, which provided the lower boundary condition. The geothermal gradient determined the temperature at the groundwater level. We generated two scenarios with 120 years of weather in an arid and a hyper-arid climate. The initial condition was established by first starting with a somewhat arbitrary unit gradient initial condition corresponding to a small fraction of the annual average rainfall and let the model run through the 120-year atmospheric forcing. The resulting profile of matric potential

  10. Merging Hydrologic, Geochemical, and Geophysical Approaches to Understand the Regolith Architecture of a Deeply Weathered Piedmont Critical Zone

    NASA Astrophysics Data System (ADS)

    Cosans, C.; Moore, J.; Harman, C. J.

    2017-12-01

    Located in the deeply weathered Piedmont in Maryland, Pond Branch has a rich legacy of hydrological and geochemical research dating back to the first geochemical mass balance study published in 1970. More recently, geophysical investigations including seismic and electrical resistivity tomography have characterized the subsurface at Pond Branch and contributed to new hypotheses about critical zone evolution. Heterogeneity in electrical resistivity in the shallow subsurface may suggest disparate flow paths for recharge, with some regions with low hydraulic conductivity generating perched flow, while other hillslope sections recharge to the much deeper regolith boundary. These shallow and deep flow paths are hypothesized to be somewhat hydrologically and chemically connected, with the spatially and temporally discontinuous connections resulting in different hydraulic responses to recharge and different concentrations of weathering solutes. To test this hypothesis, we combined modeling and field approaches. We modeled weathering solutes along the hypothesized flow paths using PFLOTRAN. We measured hydrologic gradients in the hillslopes and riparian zone using piezometer water levels. We collected geochemical data including major ions and silica. Weathering solute concentrations were measured directly in the precipitation, hillslope springs, and the riparian zone for comparison to modeled concentration values. End member mixing methods were used to determine contributions of precipitation, hillslopes, and riparian zone to the stream. Combining geophysical, geochemical, and hydrological methods may offer insights into the source of stream water and controls on chemical weathering. Previous hypotheses that Piedmont critical zone architecture results from a balance of erosion, soil, and weathering front advance rates cannot account for the inverted regolith structure observed through seismic investigations at Pond Branch. Recent alternative hypotheses including weathering

  11. An analytical solution to assess the SH seismoelectric response of the vadose zone

    NASA Astrophysics Data System (ADS)

    Monachesi, L. B.; Zyserman, F. I.; Jouniaux, L.

    2018-03-01

    We derive an analytical solution of the seismoelectric conversions generated in the vadose zone, when this region is crossed by a pure shear horizontal (SH) wave. Seismoelectric conversions are induced by electrokinetic effects linked to relative motions between fluid and porous media. The considered model assumes a one-dimensional soil constituted by a single layer on top of a half space in contact at the water table, and a shearing force located at the earth's surface as the wave source. The water table is an interface expected to induce a seismoelectric interfacial response (IR). The top layer represents a porous rock which porous space is partially saturated by water and air, while the half-space is completely saturated with water, representing the saturated zone. The analytical expressions for the coseismic fields and the interface responses, both electric and magnetic, are derived by solving Pride's equations with proper boundary conditions. An approximate analytical expression of the solution is also obtained, which is very simple and applicable in a fairly broad set of situations. Hypothetical scenarios are proposed to study and analyse the dependence of the electromagnetic fields on various parameters of the medium. An analysis of the approximate solution is also made together with a comparison to the exact solution. The main result of the present analysis is that the amplitude of the interface response generated at the water table is found to be proportional to the jump in the electric current density, which in turn depends on the saturation contrast, poro-mechanical and electrical properties of the medium and on the amplitude of the solid displacement produced by the source. This result is in agreement with the one numerically obtained by the authors, which has been published in a recent work. We also predict the existence of an interface response located at the surface, and that the electric interface response is several orders of magnitude bigger than

  12. An analytical solution to assess the SH seismoelectric response of the vadose zone

    NASA Astrophysics Data System (ADS)

    Monachesi, L. B.; Zyserman, F. I.; Jouniaux, L.

    2018-06-01

    We derive an analytical solution of the seismoelectric conversions generated in the vadose zone, when this region is crossed by a pure shear horizontal (SH) wave. Seismoelectric conversions are induced by electrokinetic effects linked to relative motions between fluid and porous media. The considered model assumes a 1D soil constituted by a single layer on top of a half-space in contact at the water table, and a shearing force located at the earth's surface as the wave source. The water table is an interface expected to induce a seismoelectric interfacial response (IR). The top layer represents a porous rock in which porous space is partially saturated by water and air, while the half-space is completely saturated with water, representing the saturated zone. The analytical expressions for the coseismic fields and the interface responses, both electric and magnetic, are derived by solving Pride's equations with proper boundary conditions. An approximate analytical expression of the solution is also obtained, which is very simple and applicable in a fairly broad set of situations. Hypothetical scenarios are proposed to study and analyse the dependence of the electromagnetic fields on various parameters of the medium. An analysis of the approximate solution is also made together with a comparison to the exact solution. The main result of the present analysis is that the amplitude of the interface response generated at the water table is found to be proportional to the jump in the electric current density, which in turn depends on the saturation contrast, poro-mechanical and electrical properties of the medium and on the amplitude of the solid displacement produced by the source. This result is in agreement with the one numerically obtained by the authors, which has been published in a recent work. We also predict the existence of an interface response located at the surface, and that the electric interface response is several orders of magnitude bigger than the

  13. UZIG USGS research: Advances through interdisciplinary interaction

    USGS Publications Warehouse

    Nimmo, J.R.; Andraski, Brian J.; Rafael, M.-C.

    2009-01-01

    BBecause vadose zone research relates to diverse disciplines, applications, and modes of research, collaboration across traditional operational and topical divisions is especially likely to yield major advances in understanding. The Unsaturated Zone Interest Group (UZIG) is an informal organization sponsored by the USGS to encourage and support interdisciplinary collaboration in vadose or unsaturated zone hydrologic research across organizational boundaries. It includes both USGS and non-USGS scientists. Formed in 1987, the UZIG operates to promote communication, especially through periodic meetings with presentations, discussions, and field trips. The 10th meeting of the UZIG at Los Alamos, NM, in August 2007 was jointly sponsored by the USGS and Los Alamos National Laboratory. Presentations at this meeting served as the initial basis for selecting papers for this special section of Vadose Zone Journal, the purpose of which is to present noteworthy cutting-edge unsaturated zone research promoted by, facilitated by, or presented in connection with the UZIG.

  14. Long-term tillage and crop rotation effects on residual nitrate in the crop root zone and nitrate accumulation in the intermediate vadose zone

    USGS Publications Warehouse

    Katupitiya, A.; Eisenhauer, D.E.; Ferguson, R.B.; Spalding, R.F.; Roeth, F.W.; Bobier, M.W.

    1997-01-01

    Tillage influences the physical and biological environment of soil. Rotation of crops with a legume affects the soil N status. A furrow irrigated site was investigated for long-term tillage and crop rotation effects on leaching of nitrate from the root zone and accumulation in the intermediate vadose zone (IVZ). The investigated tillage systems were disk-plant (DP), ridge-till (RT) and slot-plant (SP). These tillage treatments have been maintained on the Hastings silt loam (Udic Argiustoll) and Crete silt loam (Pachic Argiustoll) soils since 1976. Continuous corn (CC) and corn soybean (CS) rotations were the subtreatments. Since 1984, soybeans have been grown in CS plots in even calendar years. All tillage treatments received the same N rate. The N rate varied annually depending on the root zone residual N. Soybeans were not fertilized with N-fertilizer. Samples for residual nitrate in the root zone were taken in 8 of the 15 year study while the IVZ was only sampled at the end of the study. In seven of eight years, root zone residual soil nitrate-N levels were greater with DP than RT and SP. Residual nitrate-N amounts were similar in RT and SP in all years. Despite high residual nitrate-N with DP and the same N application rate, crop yields were higher in RT and SP except when DP had an extremely high root zone nitrate level. By applying the same N rates on all tillage treatments, DP may have been fertilized in excess of crop need. Higher residual nitrate-N in DP was most likely due to a combination of increased mineralization with tillage and lower yield compared to RT and SP. Because of higher nitrate availability with DP, the potential for nitrate leaching from the root zone was greater with DP as compared to the RT and SP tillage systems. Spring residual nitrate-N contents of DP were larger than RT and SP in both crop rotations. Ridge till and SP systems had greater nitrate-N with CS than CC rotations. Nitrate accumulation in IVZ at the upstream end of the

  15. A chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1997 progress report and presentations at the annual meeting, Ernest Orlando Lawrence Berkeley National Laboratory, December 3--4, 1997

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Faybishenko, B.; Doughty, C.; Geller, J.

    1998-07-01

    Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to developmore » a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies. View-graphs from ten presentations made at the annual meeting held December 3--4, 1997 are included in an appendix to this report.« less

  16. Elucidating Critical Zone Process Interactions with an Integrated Hydrology Model in a Headwaters Research Catchment

    NASA Astrophysics Data System (ADS)

    Collins, C.; Maxwell, R. M.

    2017-12-01

    Providence Creek (P300) watershed is an alpine headwaters catchment located at the Southern Sierra Critical Zone Observatory (SSCZO). Evidence of groundwater-dependent vegetation and drought-induced tree mortality at P300 along with the effect of subsurface characterization on mountain ecohydrology motivates this study. A hyper resolution integrated hydrology model of this site, along with extensive instrumentation, provides an opportunity to study the effects of lateral groundwater flow on vegetation's tolerance to drought. ParFlow-CLM is a fully integrated surface-subsurface model that is driven with reconstructed meteorology, such as the North American Land Data Assimilation System project phase 2 (NLDAS-2) dataset. However, large-scale data products mute orographic effects on climate at smaller scales. Climate variables often do not behave uniformly in highly heterogeneous mountain regions. Therefore, forcing physically-based integrated hydrologic models—especially of mountain headwaters catchments—with a large-scale data product is a major challenge. Obtaining reliable observations in complex terrain is challenging and while climate data products introduce uncertainties likewise, documented discrepancies between several data products and P300 observations suggest these data products may suffice. To tackle these issues, a suite of simulations was run to parse out (1) the effects of climate data source (data products versus observations) and (2) the effects of climate data spatial variability. One tool for evaluating the effect of climate data on model outputs is the relationship between latent head flux (LH) and evapotranspiration (ET) partitioning with water table depth (WTD). This zone of LH sensitivity to WTD is referred to as the "critical zone." Preliminary results suggest that these critical zone relationships are preserved despite forcing albeit significant shifts in magnitude. These results demonstrate that integrated hydrology models are sensitive

  17. Analysis of hydrologic and geochemical time-series data at James Cave, Virginia: Implications for epikarst influence on recharge in Appalachian karst aquifers

    USGS Publications Warehouse

    Eagle, Sarah D.; Orndorff, William; Schwartz, Benjamin F.; Doctor, Daniel H.; Gerst, Jonathan D.; Schreiber, Madeline E.

    2016-01-01

    The epikarst, which consists of highly weathered rock in the upper vadose zone of exposed karst systems, plays a critical role in determining the hydrologic and geochemical characteristics of recharge to an underlying karst aquifer. This study utilized time series (2007–2014) of hydrologic and geochemical data of drip water collected within James Cave, Virginia, to examine the influence of epikarst on the quantity and quality of recharge in a mature, doline-dominated karst terrain. Results show a strong seasonality of both hydrology and geochemistry of recharge, which has implications for management of karst aquifers in temperate climatic zones. First, recharge (discharge from the epikarst to the underlying aquifer) reaches a maximum between late winter and early spring, with the onset of the recharge season ranging from as early as December to as late as March during the study period. The timing and duration of the recharge season were found to be a function of precipitation in excess of evapotranspiration on a seasonal time scale. Secondly, seasonally variable residence times for water in the epikarst influence rock-water interaction and, hence, the geochemical characteristics of recharge. Overall, results highlight the strong and complex influence that the epikarst has on karst recharge, which requires long-term and high-resolution data sets to accurately understand and quantify.

  18. Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater

    USGS Publications Warehouse

    Mills, Christopher T.; Morrison, Jean M.; Goldhaber, Martin B.; Ellefsen, Karl J.

    2011-01-01

    Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacramento Valley of California where Cr(VI) concentrations in groundwater can approach or exceed 50 μg L−1. To characterize Cr geochemistry in the area, samples from several soil auger cores (approximately 4 m deep) and drill cores (approximately 25 m deep) were analyzed for total concentrations of 44 major, minor and trace elements, Cr associated with labile Mn and Fe oxides, and Cr(VI). Total concentrations of Cr in these samples ranged from 140 to 2220 mg per kg soil. Between 9 and 70 mg per kg soil was released by selective extractions that target Fe oxides, but essentially no Cr was associated with the abundant reactive Mn oxides (up to ~1000 mg hydroxylamine-reducible Mn per kg soil was present). Both borehole magnetic susceptibility surveys performed at some of the drill core sites and relative differences between Cr released in a 4-acid digestion versus total Cr (lithium metaborate fusion digestion) suggest that the majority of total Cr in the samples is present in refractory chromite minerals transported from ultramafic exposures in the Coast Range Mountains. Chromium(VI) in the samples studied ranged from 0 to 42 μg kg−1, representing a minute fraction of total Cr. Chromium(VI) content was typically below detection in surface soils (top 10 cm) where soil organic matter was high, and increased with increasing depth in the soil auger cores as organic matter decreased. Maximum concentrations of Cr(VI) were up to 3 times greater in the deeper drill core samples than the shallow auger cores. Although Cr(VI) in these vadose zone soils and sediments was only a

  19. Processes and Parameters Controlling the Extent of Methanogenic Conditions in the Unsaturated Zone of a Crude Oil Spill Site

    NASA Astrophysics Data System (ADS)

    Molins, S.; Mayer, K.

    2007-12-01

    Gas concentrations measured in the vadose zone at a crude oil spill site near Bemidji, MN, show that a large area near the oil body is currently dominated by methanogenic conditions. Away from the oil body methane concentrations decrease as it is degraded by methanotrophic bacteria under aerobic conditions. Numerical simulations have been conducted to quantify the contributions of the relevant transport and reaction processes to the production and attenuation of methane in the vadose zone. Methane is generated in the vadose zone by anaerobic degradation of oil and is also added by fluxes from the capillary fringe and the saturated zone. Gas diffusion and advection contribute to the transport of methane in the lateral direction and towards the ground surface. Attenuation of methane concentrations occurs through aerobic oxidation in the presence of methanotrophic bacteria. Critical parameters were varied within bounds provided by field data and previous studies. Simulation results confirm that the layered sediment structure present at the site plays a significant role in explaining the observed distribution of gases in the vadose zone. The presence of a low permeability lens in the area upgradient from the source results in higher moisture contents, limiting diffusion of oxygen into the zone of methane production, and contributes to the spread of methane. Diffusion was identified as the most significant transport mechanism for gases in the vadose zone. However, field-observed zones of depleted and enriched N2 and Ar concentrations could only be explained by the development of advective fluxes induced by reactive processes (methanogenesis and methanotrophy). The zones of gas production are characterized by slightly increased total gas pressures and low concentrations of N2 and Ar, while zones of gas consumption show slightly depressed total gas pressures and high concentrations of N2 and Ar. The simulations suggest that the advective flux that develops between these

  20. Trace Metals in Groundwater & the Vadose Zone Calcite: In Situ Containment & Stabilization of Strontium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, Robert W.

    2004-12-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zonemore » systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).« less

  1. Dependence of shear wave seismoelectrics on soil textures: a numerical study in the vadose zone

    NASA Astrophysics Data System (ADS)

    Zyserman, F. I.; Monachesi, L. B.; Jouniaux, L.

    2017-02-01

    In this work, we study seismoelectric conversions generated in the vadose zone, when this region is traversed by a pure SH wave. We assume that the soil is a 1-D partially saturated lossy porous medium and we use the van Genuchten's constitutive model to describe the water saturation profile. Correspondingly, we extend Pride's formulation to deal with partially saturated media. In order to evaluate the influence of different soil textures we perform a numerical analysis considering, among other relevant properties, the electrokinetic coupling, coseismic responses and interface responses (IRs). We propose new analytical transfer functions for the electric and magnetic field as a function of the water saturation, modifying those of Bordes et al. and Garambois & Dietrich, respectively. Further, we introduce two substantially different saturation-dependent functions into the electrokinetic (EK) coupling linking the poroelastic and the electromagnetic wave equations. The numerical results show that the electric field IRs markedly depend on the soil texture and the chosen EK coupling model, and are several orders of magnitude stronger than the electric field coseismic ones. We also found that the IRs of the water table for the silty and clayey soils are stronger than those for the sandy soils, assuming a non-monotonous saturation dependence of the EK coupling, which takes into account the charged air-water interface. These IRs have been interpreted as the result of the jump in the viscous electric current density at the water table. The amplitude of the IR is obtained using a plane SH wave, neglecting both the spherical spreading and the restriction of its origin to the first Fresnel zone, effects that could lower the predicted values. However, we made an estimation of the expected electric field IR amplitudes detectable in the field by means of the analytical transfer functions, accounting for spherical spreading of the SH seismic waves. This prediction yields a value

  2. Effectiveness of Hydraulic Parameterization Strategies for Simulating Moisture Dynamics in a Deep Semi-Arid Vadose Zone

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Schaap, M. G.

    2012-12-01

    Over the past fifteen years, the University of Arizona has carried out four controlled infiltration experiments in a 3600 m2, 15 meter deep vadose zone (Maricopa, Arizona) in which the evolution of moisture content (9 wells, 25 cm resolution), and matric potential (27 locations) was monitored and the subsurface stratigraphy, texture (1042 samples), and bulk density (251 samples) was characterized. In order to simulate the subsurface moisture dynamics it is necessary to define the 3D structure of the subsurface hydraulic characteristics (i.e. moisture retention and hydraulic functions). Several simple to complex strategies are possible ranging from stratigraphy based layering using hydraulic parameters derived from core samples to sophisticated numerical inversions based on 3D geostatistics and site-specific pedotransfer functions. A range of approaches will be evaluated on objective metrics that quantify how well the observed moisture dynamics are matched by simulations. We will evaluate the worth of auxiliary data such as observed matric potentials and quantity the number of texture samples needed to arrive at effective descriptions of subsurface structure. In addition, we will discuss more subjective metrics that evaluate the relative effort involved and estimate monetary cost of each method. While some of the results will only be valid for the studied site, some general conclusions will be possible about the effectiveness of particular methods for other semi-arid sites.

  3. Advective removal of intraparticle uranium from contaminated vadose zone sediments, Hanford, U.S.

    PubMed

    Ilton, Eugene S; Qafoku, Nikolla P; Liu, Chongxuan; Moore, Dean A; Zachara, John M

    2008-03-01

    A column study on U(VI)-contaminated vadose zone sediments from the Hanford Site, WA, was performed to investigate U(VI) release kinetics with water advection and variable geochemical conditions. The sediments were collected from an area adjacent to and below tank BX-102 that was contaminated as a result of a radioactive tank waste overfill event. The primary reservoir for U(VI) in the sediments are micrometer-size precipitates composed of nanocrystallite aggregates of a Na-U-Silicate phase, most likely Na-boltwoodite, that nucleated and grew within microfractures of the plagioclase component of sand-sized granitic clasts. Two sediment samples, with different U(VI) concentrations and intraparticle mass transfer properties, were leached with advective flows of three different solutions. The influent solutions were all calcite-saturated and in equilibrium with atmospheric CO2. One solution was prepared from DI water, the second was a synthetic groundwater (SGW) with elevated Na that mimicked groundwater at the Hanford site, and the third was the same SGW but with both elevated Na and Si. The latter two solutions were employed, in part, to test the effect of saturation state on U(VI) release. For both sediments, and all three electrolytes, there was an initial rapid release of U(VI) to the advecting solution followed by slower near steady-state release. U(VI)aq concentrations increased during subsequent stop-flow events. The electrolytes with elevated Na and Si depressed U(VL)aq concentrations in effluent solutions. Effluent U(VI)aq concentrations for both sediments and all three electrolytes were simulated reasonably well by a three domain model (the advecting fluid, fractures, and matrix) that coupled U(VI) dissolution, intraparticle U(VI)aq diffusion, and interparticle advection, where diffusion and dissolution properties were parameterized in a previous batch study.

  4. Hydrological connectivity in the karst critical zone: an integrated approach

    NASA Astrophysics Data System (ADS)

    Chen, X.; Zhang, Z.; Soulsby, C.; Cheng, Q.; Binley, A. M.; Tao, M.

    2017-12-01

    Spatial heterogeneity in the subsurface is high, evidenced by specific landform features (sinkholes, caves etc.) and resulting in high variability of hydrological processes in space and time. This includes complex exchange of various flow sources (e.g. hillslope springs and depression aquifers) and fast conduit flow and slow fracture flow. In this paper we integrate various "state-of-the-art" methods to understand the structure and function of this understudied critical zone environment. Geophysical, hydrometric and hydrogeochemical tools are used to characterize the hydrological connectivity of the cockpit karst critical zone in a small catchment of Chenqi, Guizhou province, China. Geophysical surveys, using electrical resistivity tomography (ERT), identified the complex conduit networks that link flows between hillslopes and depressions. Statistical time series analysis of water tables and discharge responses at hillslope springs and in depression wells and underground channels showed different threshold responses of hillslope and depression flows. This reflected the differing relative contribution of fast and slow flow paths during rainfall events of varying magnitude in the hillslope epikarst and depression aquifer in dry and wet periods. This showed that the hillslope epikarst receives a high proportion of rainfall recharge and is thus a main water resource in the catchment during the drought period. In contrast, the depression aquifer receives fast, concentrated hillslope flows during large rainfall events during the wet period, resulting in the filling of depression conduits and frequent flooding. Hydrological tracer studies using water temperatures and stable water isotopes (δD and δ18O) corroborated this and provided quantitative information of the mixing proportions of various flow sources and insights into water travel times. This revealed how higher contributions of event "new" water (from hillslope springs and depression conduits displaces "old" pre

  5. Understanding Dynamic Soil Water Repellency and its Hydrological Implications

    NASA Astrophysics Data System (ADS)

    Beatty, S. M.; Smith, J. E.

    2009-05-01

    The adverse effects of water repellent soils on vadose zone hydrology are being increasingly identified worldwide in both rural and urban landscapes. Among the affected landscapes are agricultural fields, forests, effluent application sites, golf greens, wetlands, and wildfire sites. In spite of cross-discipline research efforts put forth in recent years, understanding of fundamental parameters controlling soil water behaviour in these systems is lacking. This is due, in part, to inherent complexities of water repellent soil systems and logistical shortcomings of methods commonly used by researchers in-situ and in the lab. As a result, modeling flow in these systems has further proven to be a difficult task. The objectives of our study were 1) to systematically measure and quantify water infiltration and distribution in dynamic water repellent systems and 2) to identify fundamental hydraulic behaviours that lead to the expression of changes in soil water repellency. To achieve this, we combined techniques to elucidate soil- water interactions at a post-wildfire site. Field tests and subsequent lab work reveal essential hydrological information on fire-affected water repellent soils at variable scales and under different burn conditions. Through the use of traditional and newer techniques, our work shows unique and previously unreported behaviour of soil water in these systems. We also address limitations of current field methods used to study repellency and associated infiltration behaviours.

  6. Transport of Nitrogen and Phosphorus from Onsite Wastewater Treatment Systems to Shallow Groundwater

    NASA Astrophysics Data System (ADS)

    Toor, G.

    2014-12-01

    The knowledge about the nutrients transport from the vadose zone of onsite wastewater treatment systems (commonly called septic systems) is crucial to protect groundwater quality as 25% of US population uses septic systems to discharge household wastewater. For example, our preliminary data showed that about 47% of applied water was recovered at 60-cm below drainfield of septic systems. This implies that contaminants present in wastewater, if not attenuated in the vadose zone, can be transported to shallow groundwater. This presentation will focus on the biophysical and hydrologic controls on the transport of nitrogen (N) and phosphorus (P) from the vadose of two conventional (drip dispersal, gravel trench) and an advanced (with aerobic and anaerobic medias) system. These systems were constructed using two rows of drip pipe (37 emitters/mound) placed 0.3 m apart in the center of 6 m x 0.6 m drainfield. Each system received 120 L of wastewater per day. During 20-month period (May 2012 to December 2013), soil-water samples were collected from the vadose zone using suction cup lysimeters installed at 0.30, 0.60, and 1.05 m depth and groundwater samples were collected from piezometers installed at 3-3.30 m depth below the drainfield. A complimentary 1-year study using smaller drainfields (0.5 m long, 0.9 m wide, 0.9 m high) was conducted to obtain better insights in the vadose zone. A variety of instruments (multi-probe sensors, suction cup lysimeters, piezometers, tensiometers) were installed in the vadose zones. Results showed that nitrification controlled N evolution in drainfield and subsequent transport of N plumes (>10 mg/L) into groundwater. Most of the wastewater applied soluble inorganic P (>10 mg/L) was quickly attenuated in the drainfield due to fixation (sorption, precipitation) in the vadose zone (<0.10 mg/L), which was further reduced to <0.05 mg/L in groundwater. The hydrologic controls (primarily rainfall during June-September) facilitated transport of

  7. The impact of hydrologic segmentation on the Critical Zone water fluxes of headwater catchments

    NASA Astrophysics Data System (ADS)

    Gutierrez-Jurado, H. A.; Dominguez, M.; Guan, H.

    2017-12-01

    Headwater catchments are usually located on areas with complex terrain, where variability in aspect and microclimate give rise to contrasting vegetation cover and soil properties. This fine-scale variability in land surface conditions within a catchment is usually overlooked in hydrologic models, and the resulting differences in hydrologic dynamics across the slopes neglected. In this work we evaluate the impact of the differential hydrologic response, or as we define it here, "hydrologic segmentation" on the partition of water fluxes of contrasting slopes within a series of headwater catchments across a latitudinal gradient. Our aim is to investigate the effect of hydrologically segmenting the slopes of headwater catchments as a function of their unique aspect-vegetation-soils associations, on the water fluxes of the catchments and their potential consequences on the water balance at a regional scale. Using a distributed hydrologic model and data from a series of catchments with varying land cover and climatic conditions, we run a set of simulations with and without hydrologic segmentation to assess the effect of changing the architecture of the top part of the critical zone on the evaporation, transpiration, infiltration and runoff fluxes of each catchment slope. We calibrate and compare the simulation results with observations from a network of hydrologic sensors and independent field estimates of the various water fluxes. Our results suggest that hydrologic segmentation will significantly affect both the timing and partition of evapotranspiration fluxes with direct impacts on soil moisture residence times and the potential for deep infiltration and aquifer recharge.

  8. Water table dynamics and biogeochemical cycling in a shallow, variably-saturated floodplain

    DOE PAGES

    Yabusaki, Steven B.; Wilkins, Michael J.; Fang, Yilin; ...

    2017-02-20

    Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system, aerobic respiration generally maintains anoxic groundwater below an oxic vadose zone until seasonal snowmelt-driven water table peaking transports dissolved oxygen (DO) and nitrate from the vadose zone into the alluvial aquifer. The response to this perturbation is localized due to distinct physico-biogeochemical environments and relatively long time scales for transport through the floodplainmore » aquifer and vadose zone. Naturally reduced zones (NRZs) containing sediments higher in organic matter, iron sulfides, and non-crystalline U(IV) rapidly consume DO and nitrate to maintain anoxic conditions, yielding Fe(II) from FeS oxidative dissolution, nitrite from denitrification, and U(VI) from nitrite-promoted U(IV) oxidation. Redox cycling is a key factor for sustaining the observed aquifer behaviors despite continuous oxygen influx and the annual hydrologically induced oxidation event. Furthermore, depth-dependent activity of fermenters, aerobes, nitrate reducers, sulfate reducers, and chemolithoautotrophs (e.g., oxidizing Fe(II), S compounds, and ammonium) is linked to the presence of DO, which has higher concentrations near the water table.« less

  9. Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Flint, Alan L.; Flint, Lorraine E.; Bodvarsson, Gudmundur S.; Kwicklis, Edward M.; Fabryka-Martin, June

    2001-06-01

    Yucca Mountain is an arid site proposed for consideration as the United States' first underground high-level radioactive waste repository. Low rainfall (approximately 170 mm/yr) and a thick unsaturated zone (500-1000 m) are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment. The framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr. Early conceptual models assumed that very small volumes of water infiltrated into the bedrock (0.5-4.5 mm/yr, or 2-3 percent of rainfall), that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects, and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded, fractured rocks. It was believed that the matrix had to be saturated for fractures to flow. However, accumulating evidence indicated that infiltration rates were higher than initially estimated, such as infiltration modeling based on neutron borehole data, bomb-pulse isotopes deep in the mountain, perched water analyses and thermal analyses. Mechanisms supporting lateral diversion did not apply at these higher fluxes, and the flux calculated in the lower welded unit exceeded the conductivity of the matrix, implying vertical flow of water in the high permeability fractures of the potential repository host rock, and disequilibrium between matrix and fracture water potentials. The development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data

  10. Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada

    USGS Publications Warehouse

    Flint, Alan L.; Flint, Lorraine E.; Bodvarsson, Gudmundur S.; Kwicklis, Edward M.; Fabryka-Martin, June

    2001-01-01

    Yucca Mountain is an arid site proposed for consideration as the United States’ first underground high-level radioactive waste repository. Low rainfall (approximately 170 mm/yr) and a thick unsaturated zone (500–1000 m) are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment. The framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr. Early conceptual models assumed that very small volumes of water infiltrated into the bedrock (0.5–4.5 mm/yr, or 2–3 percent of rainfall), that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects, and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded, fractured rocks. It was believed that the matrix had to be saturated for fractures to flow. However, accumulating evidence indicated that infiltration rates were higher than initially estimated, such as infiltration modeling based on neutron borehole data, bomb-pulse isotopes deep in the mountain, perched water analyses and thermal analyses. Mechanisms supporting lateral diversion did not apply at these higher fluxes, and the flux calculated in the lower welded unit exceeded the conductivity of the matrix, implying vertical flow of water in the high permeability fractures of the potential repository host rock, and disequilibrium between matrix and fracture water potentials. The development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data

  11. Characterization and Extraction of Uranium Contamination Perched within the Deep Vadose Zone at the Hanford Site, Washington State

    NASA Astrophysics Data System (ADS)

    Williams, B. A.; Rohay, V. J.; Benecke, M. W.; Chronister, G. B.; Doornbos, M. H.; Morse, J.

    2012-12-01

    A highly contaminated perched water zone has been discovered in the deep vadose zone above the unconfined aquifer during drilling of wells to characterize groundwater contamination within the 200 East Area of the U.S. Department of Energy's Hanford Site in southeast Washington. The perched water, which contains nitrate, uranium, and technetium-99 at concentrations that have exceeded 100,000 μg/L, 70,000 μg/L, and 45,000 pCi/L respectively, is providing contamination to the underlying unconfined aquifer. A perched zone extraction well has been installed and is successfully recovering the contaminated perched water as an early remedial measure to reduce impacts to the unconfined aquifer. The integration and interpretation of various borehole hydrogeologic, geochemical, and geophysical data sets obtained during drilling facilitated the delineation of the perching horizon and determination of the nature and extent of the perched contamination. Integration of the borehole geologic and geophysical logs defined the structural elevation and thickness of the perching low permeability silt interval. Borehole geophysical moisture logs, gamma logs, and sample data allowed detailed determination of the elevation and thickness of the oversaturated zone above the perching horizon, and the extent and magnitude of the radiological uranium contamination within the perching interval. Together, these data sets resolved the nature of the perching horizon and the location and extent of the contaminated perched water within the perching zone, allowing an estimation of remaining contaminant extent. The resulting conceptual model indicates that the contaminated perched water is contained within a localized sand lens deposited in a structural low on top of a semi-regional low-permeability silt layer. The top of the sand lens is approximately 72 m (235 ft) below ground surface; the maximum thickness of the sand lens is approximately 3 m (10 ft). The lateral and vertical extent of the

  12. Hydrogeophysical Cyberinfrastructure For Real-Time Interactive Browser Controlled Monitoring Of Near Surface Hydrology: Results Of A 13 Month Monitoring Effort At The Hanford 300 Area

    NASA Astrophysics Data System (ADS)

    Versteeg, R. J.; Johnson, T.; Henrie, A.; Johnson, D.

    2013-12-01

    The Hanford 300 Area, located adjacent to the Columbia River in south-central Washington, USA, is the site of former research and uranium fuel rod fabrication facilities. Waste disposal practices at the site included discharging between 33 and 59 metric tons of uranium over a 40 year period into shallow infiltration galleries, resulting in persistent uranium contamination within the vadose and saturated zones. Uranium transport from the vadose zone to the saturated zone is intimately linked with water table fluctuations and river water driven by upstream dam operations. Different remedial efforts have occurred at the site to address uranium contamination. Numerous investigations are occurring at the site, both to investigate remedial performance and to increase the understanding of uranium dynamics. Several of these studies include acquisition of large hydrological and time lapse electrical geophysical data sets. Such datasets contain large amounts of information on hydrological processes. There are substantial challenges in how to effectively deal with the data volumes of such datasets, how to process such datasets and how to provide users with the ability to effectively access and synergize the hydrological information contained in raw and processed data. These challenges motivated the development of a cloud based cyberinfrastructure for dealing with large electrical hydrogeophysical datasets. This cyberinfrastructure is modular and extensible and includes datamanagement, data processing, visualization and result mining capabilities. Specifically, it provides for data transmission to a central server, data parsing in a relational database and processing of the data using a PNNL developed parallel inversion code on either dedicated or commodity compute clusters. Access to results is done through a browser with interactive tools allowing for generation of on demand visualization of the inversion results as well as interactive data mining and statistical calculation

  13. Development of a Hydrologic Characterization Technology for Fault Zones Phase II 2nd Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karasaki, Kenzi; Doughty, Christine; Gasperikova, Erika

    2011-03-31

    This is the 2nd report on the three-year program of the 2nd phase of the NUMO-LBNL collaborative project: Development of Hydrologic Characterization Technology for Fault Zones under NUMO-DOE/LBNL collaboration agreement. As such, this report is a compendium of the results by Kiho et al. (2011) and those by LBNL.

  14. Climate variability controls on unsaturated water and chemical movement, High Plains aquifer, USA

    USGS Publications Warehouse

    Gurdak, J.J.; Hanson, R.T.; McMahon, P.B.; Bruce, B.W.; McCray, J.E.; Thyne, G.D.; Reedy, R.C.

    2007-01-01

    Responses in the vadose zone and groundwater to interannual, interdecadal, and multidecadal climate variability have important implications for groundwater resource sustainability, yet they are poorly documented and not well understood in most aquifers of the USA. This investigation systematically examines the role of interannual to multidecadal climate variability on groundwater levels, deep infiltration (3-23 m) events, and downward displacement (>1 m) of chloride and nitrate reservoirs in thick (15-50 m) vadose zones across the regionally extensive High Plains aquifer. Such vadose zone responses are unexpected across much of the aquifer given a priori that unsaturated total-potential profiles indicate upward water movement from the water table toward the root zone, mean annual potential evapotranspiration exceeds mean annual precipitation, and millennia-scale evapoconcentration results in substantial vadose zone chloride and nitrate reservoirs. Using singular spectrum analysis (SSA) to reconstruct precipitation and groundwater level time-series components, variability was identified in all time series as partially coincident with known climate cycles, such as the Pacific Decadal Oscillation (PDO) (10-25 yr) and the El Nin??o/Southern Oscillation (ENSO) (2-6 yr). Using these lag-correlated hydrologic time series, a new method is demonstrated to estimate climate-varying unsaturated water flux. The results suggest the importance of interannual to interdecadal climate variability on water-flux estimation in thick vadose zones and provide better understanding of the climate-induced transients responsible for the observed deep infiltration and chemical-mobilization events. Based on these results, we discuss implications for climate-related sustainability of the High Plains aquifer. ?? Soil Science Society of America.

  15. Parameterization and Modeling of Coupled Heat and Mass Transport in the Vadose Zone

    NASA Astrophysics Data System (ADS)

    Mohanty, B.; Yang, Z.

    2016-12-01

    The coupled heat and mass transport in the vadose zone is essentially a multiphysics issue. Addressing this issue appropriately has remarkable impacts on soil physical, chemical and biological processes. To data, most coupled heat and water transport modeling has focused on the interactions between liquid water, water vapor and heat transport in homogeneous and layered soils. Comparatively little work has been done on structured soils where preferential infiltration and evaporation flow occurs. Moreover, the traditional coupled heat and water model usually neglects the nonwetting phase air flow, which was found to be significant in the state-of-the-art modeling framework for coupled heat and water transport investigation. However, the parameterizations for the nonwetting phase air permeability largely remain elusive so far. In order to address the above mentioned limitations, this study aims to develop and validate a predictive multiphysics modeling framework for coupled soil heat and water transport in the heterogeneous shallow subsurface. To this end, the following research work is specifically conducted: (a) propose an improved parameterization to better predict the nonwetting phase relative permeability; (b) determine the dynamics, characteristics and processes of simultaneous soil moisture and heat movement in homogeneous and layered soils; and (c) develop a nonisothermal dual permeability model for heterogeneous structured soils. The results of our studies showed that: (a) the proposed modified nonwetting phase relative permeability models are much more accurate, which can be adopted for better parameterization in the subsequent nonisothermal two phase flow models; (b) the isothermal liquid film flow, nonwetting phase gas flow and liquid-vapor phase change non-equilibrium effects are significant in the arid and semiarid environments (Riverside, California and Audubon, Arizona); and (c) the developed nonisothermal dual permeability model is capable of

  16. Fluid inclusions in vadose cement with consistent vapor to liquid ratios, Pleistocene Miami Limestone, southeastern Florida

    USGS Publications Warehouse

    Barker, C.E.; Halley, R.B.

    1988-01-01

    Vadose cements in the Late Pleistocene Miami Limestone contain regions with two-phase aqueous fluid inclusions that have consistent vapor to liquid (V-L) ratios. When heated, these seemingly primary inclusions homogenize to a liquid phase in a range between 75??C and 130??C (mean = 100??C) and have final melting temperatures between -0.3?? and 0.0??C. The original distribution of Th was broadened during measurements because of fluid inclusion reequilibration. The narrow range of Th in these fluid inclusions suggest unusually consistent V-L ratios. They occur with small, obscure, single phase liquid-filled inclusions, which infer a low temperature origin (less than 60??C), and contradict the higher temperature origin implied by the two phase inclusions. The diagenetic environment producing these seemingly primary fluid inclusions can be inferred from the origin of the host calcite enclosing them. The ??18O composition of these cements (-4 to-5.5%., PDB) and the fresh water in the fluid inclusions are consistent with precipitation from low-temperature meteoric water. The carbon-isotope composition of the vadose cements that contain only rare two-phase fluid inclusions are comparable to the host rock matrix (??13C between 0 and +4%., PDB). Cements that contain common two-phase fluid-inclusions have a distinctly lighter carbon isotopic composition of -3 to -5%.. The carbon isotope composition of cements that contain common two-phase inclusions are about 6%. lighter than those of other vadose cements; models of early meteoric diagenesis indicate that this is the result of precipitation from water that has been influenced by soil gas CO2. Our hypothesis is that the primary fluid inclusions, those with consistent V-L ratios and the single-phase liquid inclusions, form at near-surface temperature (25??C) and pressure when consistent proportions of soil gas and meteoric water percolating through the vadose zone are trapped within elongate vacuoles. This study corroborates

  17. DIN retention-transport through four hydrologically connected zones in a headwater catchment of the Upper Mississippi River

    USGS Publications Warehouse

    Triska, F.J.; Duff, J.H.; Sheibley, R.W.; Jackman, A.P.; Avanzino, R.J.

    2007-01-01

    Dissolved inorganic nitrogen (DIN) retention-transport through a headwater catchment was synthesized from studies encompassing four distinct hydrologic zones of the Shingobee River Headwaters near the origin of the Mississippi River. The hydrologic zones included: (1) hillslope ground water (ridge to bankside riparian); (2) alluvial riparian ground water; (3) ground water discharged through subchannel sediments (hyporheic zone); and (4) channel surface water. During subsurface hillslope transport through Zone 1, DIN, primarily nitrate, decreased from ???3 mg-N/l to <0.1 mg-N/l. Ambient seasonal nitrate:chloride ratios in hillslope flow paths indicated both dilution and biotic processing caused nitrate loss. Biologically available organic carbon controlled biotic nitrate retention during hillslope transport. In the alluvial riparian zone (Zone 2) biologically available organic carbon controlled nitrate depletion although processing of both ambient and amended nitrate was faster during the summer than winter. In the hyporheic zone (Zone 3) and stream surface water (Zone 4) DIN retention was primarily controlled by temperature. Perfusion core studies using hyporheic sediment indicated sufficient organic carbon in bed sediments to retain ground water DIN via coupled nitrification-denitrification. Numerical simulations of seasonal hyporheic sediment nitrification-denitrification rates from perfusion cores adequately predicted surface water ammonium but not nitrate when compared to 5 years of monthly field data (1989-93). Mass balance studies in stream surface water indicated proportionally higher summer than winter N retention. Watershed DIN retention was effective during summer under the current land use of intermittently grazed pasture. However, more intensive land use such as row crop agriculture would decrease nitrate retention efficiency and increase loads to surface water. Understanding DIN retention capacity throughout the system, including special channel

  18. Seasonal Hydrologic Controls on Uranium and Iron Biogeochemistry in a Riparian Aquifer

    NASA Astrophysics Data System (ADS)

    Wilkins, M.; Williams, K. H.; Danczak, R. E.; Yabusaki, S.; Fang, Y.; Hobson, C.

    2015-12-01

    The maintenance of geochemically reducing conditions is generally optimal for the formation and preservation of reduced metals and mineral phases that can limit contaminant fate and transport. At a riparian aquifer near Rifle, CO, we tracked over six months the biogeochemical response within the aquifer to an annual pulse of dissolved oxygen (DO) that results from snowmelt-driven changes in Colorado River stage. In reduced portions of the aquifer (naturally reduced zones; NRZs) the re-oxidation of abundant iron sulfide minerals was the dominant oxygen-consuming process, and resulted in little DO intrusion into the deeper aquifer. In less reduced areas, DO intruded through the entire vertical profile of the aquifer. Across both regions, these perturbations resulted in changes to the microbial community structure, and aqueous metal pools. Two potentially different mechanisms of uranium mobilization were observed; (1) re-oxidation of reduced U(IV) phases in response to DO intrusion, and (2) mobilization of U(VI) from the vadose zone during water table rise. This high-resolution, long-term monitoring of aquifer biogeochemistry at the Rifle site has revealed dynamic microbial and geochemical responses to predictable, annual hydrologic perturbations, and offers an opportunity to further refine modeling approaches for such regions.

  19. Intermittent flux from a sand filter for household wastewater and integrated solute transfer to the vadose zone.

    PubMed

    Nasri, Behzad; Fouché, Olivier

    2018-02-24

    Depending on the actual number of soil-based on-site wastewater treatment system (OWTS) in an area, on-site sanitation may be a significant source of pollutants and a threat to groundwater. Even in the case of a system functioning correctly, here, a sand filter substituted for the in-situ soil, as the treated effluent may reach to the water table, it is necessary evaluating in situ how much the sand and underneath soil respectively contribute to pollutant removal. On the plot of a household in a small rural community, the functioning of a real scale OWTS was monitored for 1.5 years. This system, composed of a septic tank connected to a 5 × 5 m 2 and 0.7-m thick aerobic sand filter was equipped with soil hydrodynamic probes (water content and matrix potential) during construction. By using the instantaneous profile method of water content, the intermittent infiltrated flux was determined across the sand-pack according to position and time. Treated water infiltrates into underneath soil acting as post-treatment. Quality of interstitial liquid from the sand and the soil was analysed each month on a 12-h pumping sample obtained through porous plates. Results of water fluxes and concentrations provide an estimate of the annual flux to the vadose zone and groundwater of metals, nutrients and some organic micro-pollutants (parabens and triclosan) through the OWTS and subsoil.

  20. Spatio-temporal Root Zone Soil Moisture Estimation for Indo - Gangetic Basin from Satellite Derived (AMSR-2 and SMOS) Surface Soil Moisture

    NASA Astrophysics Data System (ADS)

    Sure, A.; Dikshit, O.

    2017-12-01

    Root zone soil moisture (RZSM) is an important element in hydrology and agriculture. The estimation of RZSM provides insight in selecting the appropriate crops for specific soil conditions (soil type, bulk density, etc.). RZSM governs various vadose zone phenomena and subsequently affects the groundwater processes. With various satellite sensors dedicated to estimating surface soil moisture at different spatial and temporal resolutions, estimation of soil moisture at root zone level for Indo - Gangetic basin which inherits complex heterogeneous environment, is quite challenging. This study aims at estimating RZSM and understand its variation at the level of Indo - Gangetic basin with changing land use/land cover, topography, crop cycles, soil properties, temperature and precipitation patterns using two satellite derived soil moisture datasets operating at distinct frequencies with different principles of acquisition. Two surface soil moisture datasets are derived from AMSR-2 (6.9 GHz - `C' Band) and SMOS (1.4 GHz - `L' band) passive microwave sensors with coarse spatial resolution. The Soil Water Index (SWI), accounting for soil moisture from the surface, is derived by considering a theoretical two-layered water balance model and contributes in ascertaining soil moisture at the vadose zone. This index is evaluated against the widely used modelled soil moisture dataset of GLDAS - NOAH, version 2.1. This research enhances the domain of utilising the modelled soil moisture dataset, wherever the ground dataset is unavailable. The coupling between the surface soil moisture and RZSM is analysed for two years (2015-16), by defining a parameter T, the characteristic time length. The study demonstrates that deriving an optimal value of T for estimating SWI at a certain location is a function of various factors such as land, meteorological, and agricultural characteristics.

  1. Hydrologically-driven crustal stresses and seismicity in the New Madrid Seismic Zone.

    PubMed

    Craig, Timothy J; Chanard, Kristel; Calais, Eric

    2017-12-15

    The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or 'stable' plate interiors, remains a subject of debate. Recent work in plate-boundary regions demonstrates the capacity for long-wavelength changes in continental water storage to produce observable surface deformation, induce crustal stresses and modulate seismicity rates. Here we show that a significant variation in the rate of microearthquakes in the intraplate New Madrid Seismic Zone at annual and multi-annual timescales coincides with hydrological loading in the upper Mississippi embayment. We demonstrate that this loading, which results in geodetically observed surface deformation, induces stresses within the lithosphere that, although of small amplitude, modulate the ongoing seismicity of the New Madrid region. Correspondence between surface deformation, hydrological loading and seismicity rates at both annual and multi-annual timescales indicates that seismicity variations are the direct result of elastic stresses induced by the water load.

  2. Using an Integrated Hydrologic Model to Assess the Ecohydrological Impacts of Change on a Mountain Headwaters Critical Zone

    NASA Astrophysics Data System (ADS)

    Collins, C.; Maxwell, R. M.; Visser, A.

    2016-12-01

    The critical zone is the region of the Earth's crust where hydrogeology, ecology, and climate interact. As many critical zone processes are fundamental, the significance of studying critical zone processes goes beyond understanding the local ecohydrological setting. Therefore studying critical zone governing processes requires an interdisciplinary approach that integrates simulation and observation. In this study, a high-resolution integrated hydrologic model, ParFlow-CLM, was developed for the Providence Creek watershed. Providence Creek is a highly instrumented critical zone observatory (CZO) located in the southern Sierra Nevada Mountains, a region currently experiencing a range of short-term responses (i.e. tree mortality) to a severe four-year drought. Sources of plant water use, pathways and residence times of water through the subsurface are identified using a suite of isotopic signatures and numerical particle tracking. Implications of using a fully coupled integrated hydrologic model accompanied by tracer analysis include better understanding of water partitioning and water storage in the regolith and vegetation water use during drought time conditions. The importance of subsurface storage, plant available water and lateral flow during the 2012-2015 drought to mitigate vegetation stress are addressed and verified against observed tree mortality. The stream flow response to tree mortality in the aftermath of the drought, analogous to the Colorado Mountain Pine Beetle case, provides insight into the potential effects of proposed forest management practices.

  3. Field test and sensitivity analysis of a sensible heat balance method to determine ice contents

    USDA-ARS?s Scientific Manuscript database

    Soil ice content impacts winter vadose zone hydrology. It may be possible to estimate changes in soil ice content with a sensible heat balance (SHB) method, using measurements from heat pulse (HP) sensors. Feasibility of the SHB method is unknown because of difficulties in measuring soil thermal pro...

  4. Socio-hydrological implications of water management in the dry zone of Sri Lanka

    NASA Astrophysics Data System (ADS)

    Upeksha Gamage, Isurun; Arachchige Hemachandra Jayasena, Hetti

    2018-06-01

    Water management plays a vital role in the agricultural economy and living conditions of people in Sri Lanka. Though government and non-government organizations have been readily contributing to water management, it is still inefficient, especially in terms of water allocation, consumption and conservation. To identify factors which could be used to implement integrated water resources management (IWRM), a socio-hydrological study was performed in five areas within the dry zone in Sri Lanka. The study covers a comprehensive analysis of how the household income, demography and education level correlating to water usage, purification and disposal methods. The average household income ranges from LKR 2500 to 15 000 per month. The results show that the average daily usage for drinking, cooking, washing, toiletries and bathing are 3, 5, 10, 7, and 85 L per person, respectively. Majority of the families use dug wells and pipe-borne water as the primary source. Correlation coefficients suggest that higher household income or level of education leads to increased water consumption (R = 0.91, 0.94). There is no linear relationship between the level of education with the good practices of water purification and disposal. Though these results indicate preliminary assessments based on the dry zone practices, efficient water management could be enhanced by strong socio-hydrological implications through educating people on conservation, usage, disposal practices and health concerns.

  5. GEOPHYSICS AND SITE CHARACTERIZATION AT THE HANFORD SITE THE SUCCESSFUL USE OF ELECTRICAL RESISTIVITY TO POSITION BOREHOLES TO DEFINE DEEP VADOSE ZONE CONTAMINATION - 11509

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    GANDER MJ; LEARY KD; LEVITT MT

    2011-01-14

    Historic boreholes confirmed the presence of nitrate and radionuclide contaminants at various intervals throughout a more than 60 m (200 ft) thick vadose zone, and a 2010 electrical resistivity survey mapped the known contamination and indicated areas of similar contaminants, both laterally and at depth; therefore, electrical resistivity mapping can be used to more accurately locate characterization boreholes. At the Hanford Nuclear Reservation in eastern Washington, production of uranium and plutonium resulted in the planned release of large quantities of contaminated wastewater to unlined excavations (cribs). From 1952 until 1960, the 216-U-8 Crib received approximately 379,000,000 L (100,000,000 gal) ofmore » wastewater containing 25,500 kg (56,218 lb) uranium; 1,029,000 kg (1,013 tons) of nitrate; 2.7 Ci of technetium-99; and other fission products including strontium-90 and cesium-137. The 216-U-8 Crib reportedly holds the largest inventory of waste uranium of any crib on the Hanford Site. Electrical resistivity is a geophysical technique capable of identifying contrasting physical properties; specifically, electrically conductive material, relative to resistive native soil, can be mapped in the subsurface. At the 216-U-8 Crib, high nitrate concentrations (from the release of nitric acid [HNO{sub 3}] and associated uranium and other fission products) were detected in 1994 and 2004 boreholes at various depths, such as at the base of the Crib at 9 m (30 ft) below ground surface (bgs) and sporadically to depths in excess of 60 m (200 ft) bgs. These contaminant concentrations were directly correlative with the presence of observed low electrical resistivity responses delineated during the summer 2010 geophysical survey. Based on this correlation and the recently completed mapping of the electrically conductive material, additional boreholes are planned for early 2011 to identify nitrate and radionuclide contamination: (a) throughout the entire vertical length of

  6. Preserving Heterogeneity and Consistency in Hydrological Model Inversions by Adjusting Pedotransfer Functions

    USDA-ARS?s Scientific Manuscript database

    Numerical modeling is the dominant method for quantifying water flow and the transport of dissolved constituents in surface soils as well as the deeper vadose zone. While the fundamental laws that govern the mechanics of the flow processes in terms of Richards' and convection-dispersion equations a...

  7. Hydrology of the unsaturated zone, Yucca Mountain, Nevada

    USGS Publications Warehouse

    Lecain, Gary D.; Stuckless, John S.

    2012-01-01

    The unsaturated zone at Yucca Mountain was investigated as a possible site for the nation's first high-level nuclear waste repository. Scientific investigations included infiltration studies, matrix properties testing, borehole testing and monitoring, underground excavation and testing, and the development of conceptual and numerical models of the hydrologic processes at Yucca Mountain. Infiltration estimates by empirical and geochemical methods range from 0.2 to 1.4 mm/yr and 0.2–6.0 mm/yr, respectively. Infiltration estimates from numerical models range from 4.5 mm/yr to 17.6 mm/yr. Rock matrix properties vary vertically and laterally as the result of depositional processes and subsequent postdepositional alteration. Laboratory tests indicate that the average matrix porosity and hydraulic conductivity values for the main level of the proposed repository (Topopah Spring Tuff middle nonlithophysal zone) are 0.08 and 4.7 × 10−12 m/s, respectively. In situ fracture hydraulic conductivity values are 3–6 orders of magnitude greater. The permeability of fault zones is approximately an order of magnitude greater than that of the surrounding rock unit. Water samples from the fault zones have tritium concentrations that indicate some component of postnuclear testing. Gas and water vapor movement through the unsaturated zone is driven by changes in barometric pressure, temperature-induced density differences, and wind effects. The subsurface pressure response to surface barometric changes is controlled by the distribution and interconnectedness of fractures, the presence of faults and their ability to conduct gas and vapor, and the moisture content and matrix permeability of the rock units. In situ water potential values are generally less than −0.2 MPa (−2 bar), and the water potential gradients in the Topopah Spring Tuff units are very small. Perched-water zones at Yucca Mountain are associated with the basal vitrophyre of the Topopah Spring Tuff or the Calico

  8. Development of a Hydrologic Characterization Technology for Fault Zones Final Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karasaki, Kenzi; Onishi, Celia Tiemi; Doughty, Christine

    2012-03-31

    This is the final report for the five-year program of the NUMO-LBNL collaborative project (hereafter called the Project): Development of Hydrologic Characterization Technology for Fault Zones, under a NUMO-DOE/LBNL collaboration agreement. Detailed results from the past four years of study can be found in the each year’s year-end report (Karasaki et al., 2008, 2009, 2010, and 2011; Kiho et al., 2008, 2009, 2010, and 2011). In this report, we discuss the results of the studies conducted in FY2011. We also give a summary of the overall results and findings, as well as the lessons learned during the course of themore » Project.« less

  9. Linkages among geophysical facies, microbial composition, biogeochemical rates, and seasonal hydrology in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Stegen, J.

    2016-12-01

    The hyporheic zone is a critical ecosystem transition that links terrestrial, aquatic, and subsurface domains. To understand connections among physical, microbial, and biogeochemical components of the hyporheic zone, we obtained freeze cores along the Columbia River in the Hanford 300 Area and performed geologic, molecular, and microbial assays. Mud and sand content were found to be the primary drivers of microbial community attributes (in particular, of nitrite and carbon oxidizers). Microbial community analysis revealed an abundance of nitrifying Archaea (Thaumarchaea) and an absence of nitrifiying Bacteria. Network analysis revealed significant negative correlations between sand content and some statistical modules of microbial taxa, perhaps indicating the importance of pore water residence time on community composition. A similar set of microbial modules was positively correlated with total organic carbon. One such module that also positively correlated with aerobic metabolic rates was dominated by Thaumarchaea and Nitrospira, suggesting that ammonia oxidation was the dominant aerobic process. We also examined temporal changes in hyporheic microbial structure and activity through repeated sampling of attached and pore water microbes across a spatial gradient. We found that microbial communities remained distinct in river, hyporheic, and inland zones across seasonal variation in hydrologic mixing conditions. One reason was temperature-driven increases in microbial species richness in the hyporheic zone. We show that the relative importance of ecological selection and dispersal varied across environments and across geographic zones. Our results also indicated that while selection imposed short-term constraints on microbial community structure, hyporheic sediment communities did not respond to short-term hydrologic variation. Importantly, we demonstrated that the influence of selective pressures varied with phylogenetic affiliation, which may have been responsible

  10. Criteria for selecting fluorescent dye tracers for soil hydrological applications using Uranine as an example

    EPA Science Inventory

    Calibrating and verifying 2-D and 3-D vadose zone flow and transport models requires detailed information on water and solute redistribution. Among the different water flow and mass transfer determination methods, staining tracers have the best spatial resolution allowing visuali...

  11. Developing hydrological model for water quality in Iraq marshes zone using Landsat-TM

    NASA Astrophysics Data System (ADS)

    Marghany, Maged; Hasab, Hashim Ali; Mansor, Shattri; Shariff, Abdul Rashid Bin Mohamed

    2016-06-01

    The Mesopotamia marshlands constitute the largest wetland ecosystem in the Middle East and Western Eurasia. These wetlands are located at the confluence of the Tigris and Euphrates Rivers in southern Iraq. However, there are series reductions in the wetland zones because of neighbor countries, i.e. Turkey, Syria built dams upstream of Tigris and Euphrates Rivers. In addition, the first Gulf war of the 1980s had damaged majority of the marches resources. In fact,the marshes had been reduced in size to less than 7% since 1973 and had deteriorated in water quality parameters. The study integrates Hydrological Model of RMA-2 with Geographic Information System, and remote sensing techniques to map the water quality in the marshlands south of Iraq. This study shows that RMA-2 shows the two dimensional water flow pattern and water quality quantities in the marshlands. It can be said that the integration between Hydrological Model of RMA-2, Geographic Information System, and remote sensing techniques can be used to monitor water quality in the marshlands south of Iraq.

  12. Relating runoff generation mechanisms to concentration-discharge relationships in catchments with well-characterized Critical Zone structures and hydrologic dynamics

    NASA Astrophysics Data System (ADS)

    Hahm, W. J.; Wang, J.; Druhan, J. L.; Rempe, D.; Dietrich, W. E.

    2017-12-01

    Stream solute concentration-discharge (C-Q) relationships integrate catchment-scale hydrologic and geochemical processes, potentially yielding valuable information about runoff generation and weathering mechanisms. However, recent compilations have established that chemostasis—the condition where solute concentrations are invariant across large ranges of runoff—is observed in watersheds of diverse lithology, climate, and topography, suggesting an equifinality of the C-Q relationship independent of hydrologic process. Here we explore C-Q signals in contrasting catchments of the Eel River Critical Zone (CZ) Observatory in the Northern California Coast Ranges, where, unlike most watersheds where chemostasis has been observed, hillslope hydrologic processes are well characterized via years of intensive hydrologic monitoring. Our two catchments in the Franciscan Complex have radically different runoff generation mechanisms arising from differences in CZ structure: at Elder Creek (Coastal Belt), rain passes vertically as unsaturated flow through soil, saprolite, and a thick weathered rock zone before perching as groundwater on fresh bedrock and flowing laterally through fractures to generate streamflow, resulting in nearly chemostatic major cation behavior (power law C-Q slopes (B) ≈ 0 to -0.1). At Dry Creek (Central Belt), the thin (2 to 3 m) hydrologically active CZ completely saturates in most storm events, generating saturation overland flow across the landscape. New data from Dry Creek reveal log-log C-Q relationships for major cations that exhibit negative curvature, indicating a trend towards increasing dilution at higher flow rates and a possible C-Q signature of overland flow. High geomorphic channel drainage density (16.9 km/km2) results in short flow paths and, presumably, short water hillslope residence times at high runoff when overland flow dominates (> 50 mm d-1). Surprisingly, even at these high runoff rates, pure dilution does not occur (high

  13. Clay with Desiccation Cracks is an Advection Dominated Environment

    NASA Astrophysics Data System (ADS)

    Baram, S.; Kurtzman, D.; Sher, Y.; Ronen, Z.; Dahan, O.

    2012-04-01

    Heavy clay sediments are regarded "safe" from the hydrological point of view due to their low hydraulic conductivities. However, the formation of desiccation cracks in dispersive clays may dramatically change their bulk hydraulic properties. The impact of desiccation cracks on water percolation, dissolved salts and contaminants transport and redox related reactions (microbial ammonium oxidation and denitrification) were investigated in 6 -12 m clay layer near a diary farm waste lagoon. The study implemented unique vadose-zone monitoring systems that enable in-situ measurements of the temporal variation of the sediment's water content along with frequent sampling of the sediment's pore water along the entire vadose zone (> 30 m). Results from four years of continuous measurements showed quick rises in sediment water content following rain events and temporal wastewater overflows. The percolation pattern indicated dominance of preferential flow through a desiccation-cracks network crossing the entire clay sediment layer. High water-propagation velocities (0.4 - 23.6 m h-1) were observed, indicating that the desiccation-crack network remains open and serves as a preferential flow pathway year-round, even at high sediment water content (~0.50 m3 m-3). The rapid percolation bypassed the most bio-geo-active parts of the soil, transporting even highly sorptive contaminants (testosterone and estrogen) in to the deep sections of the vadose zone, accelerating the underlying groundwater contamination. The ammonium and nitrate concentrations in the vadose zone and the high number of nitrifying and denitrifying bacteria (~108 gene copies gdry-sediemt-1, each) found in the sediment indicated that the entire vadose zone is aerated even at high water content conditions (~0.55 m3 m-3). The dissolved salts concentration in the pore-water and the δ2H-H2O and δ18O-H2O values of the pore-water substantially increased with depth (becoming less depleted) in the clay sediment

  14. Hydrological and Oceanographic Considerations for Integrated Coastal Zone Management in Southern Belize.

    PubMed

    Heyman; Kjerfve

    1999-09-01

    / The objectives of this study are to: (1) characterize the meteorology and hydrology of the Maya Mountain-Marine Area Transect in southern Belize, (2) employ a simple water balance model to examine the discharge rates of seven watersheds to Port Honduras, (3) test the validity of the hydrological model, (4) explore the implications of potential landscape and hydrological alterations, and (5) examine the value of protected areas. The southern coastal portion of the study area is classified as wet tropical forest and the remainder as moist tropical forest. Rainfall is 3000-4000 mm annually. Resulting annual freshwater discharge directly into Port Honduras is calculated at 2.5 x 10(9) m3, a volume equal to the basin. During the rainy season, June-September, 84% of the annual discharge occurs, which causes the bay to become brackish. Port Honduras serves as an important nursery ground for many species of commercially important fish and shellfish. The removal of forest cover in the uplands, as a result of agriculture, aquaculture, and village development, is likely to significantly accelerate erosion. Increased erosion would reduce soil fertility in the uplands and negatively affect mangrove, seagrass, and coral reef productivity in the receiving coastal embayment. Alternatively, the conservation of an existing protected areas corridor, linking the Maya Mountains to the Caribbean Sea, is likely to enhance regional sustainable economic development. This study aims to support environmental management at the scale of the "ecoscape"-a sensible ecological unit of linked watersheds and coastal and marine environments.KEY WORDS: Ecosystem management; Coastal zone management; Belize; Hydrologyhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n2p229.html

  15. Hydrological and biogeochemical investigation of an agricultural watershed, southeast New Hampshire, USA

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; McDowell, W. H.; Campbell, J. E.; Hristov, A. N.

    2010-12-01

    Developing sustainable agricultural practices and policies requires an understanding of the hydrological and biological processes that control nutrient fluxes and how those processes are manifested in nutrient loading of surface water bodies. Groundwater and surface water from the UNH Organic Research Dairy, located in southeast New Hampshire, flow into the Lamprey River and then into the Great Bay, New Hampshire; both are experiencing increasing nutrient loads. The farm hosts approximately 80 Jersey cows (40 milking) and is located on relatively thin (<10m) glacial deposits that include sandy glacial till moraines, an ice-contact delta, and marine silt and clay overlying fractured calcareous quartzite. Recharge of precipitation is the dominant mode through which nutrients are introduced into the hydrologic system. Intensive meteorological, hydrological, and biogeochemical monitoring of a 35 hectare watershed that includes the main farm operation buildings and several pastures has been underway since June 2009. A three-dimensional transient unsaturated-saturated groundwater flow model was developed using LIDAR topography and detailed field mapping. The transient model was calibrated to observed water level and streamflow observations. Model results suggest that summer recharge rates vary considerably across the site and depth to the water table is the dominant control on the recharge flux. Areas having depth to water of 1-2 m experience the greatest recharge (up to 60% of precipitation). Areas with deeper water tables experience greater evapotranspiration from the vadose zone, and shallower water tables experience greater runoff. Water budget calculations suggest that the hydrologic fluxes occur predominately in the shallow groundwater, wetlands, and small surface streams draining the watershed. High dissolved nitrogen (N) concentrations (up to an average concentration of 35 mg N/L) are observed in groundwater immediately downgradient from the main farm operation

  16. Use of Large-Scale Multi-Configuration EMI Measurements to Characterize Subsurface Structures of the Vadose Zone.

    NASA Astrophysics Data System (ADS)

    Huisman, J. A.; Brogi, C.; Pätzold, S.; Weihermueller, L.; von Hebel, C.; Van Der Kruk, J.; Vereecken, H.

    2017-12-01

    Subsurface structures of the vadose zone can play a key role in crop yield potential, especially during water stress periods. Geophysical techniques like electromagnetic induction EMI can provide information about dominant shallow subsurface features. However, previous studies with EMI have typically not reached beyond the field scale. We used high-resolution large-scale multi-configuration EMI measurements to characterize patterns of soil structural organization (layering and texture) and their impact on crop productivity at the km2 scale. We collected EMI data on an agricultural area of 1 km2 (102 ha) near Selhausen (NRW, Germany). The area consists of 51 agricultural fields cropped in rotation. Therefore, measurements were collected between April and December 2016, preferably within few days after the harvest. EMI data were automatically filtered, temperature corrected, and interpolated onto a common grid of 1 m resolution. Inspecting the ECa maps, we identified three main sub-areas with different subsurface heterogeneity. We also identified small-scale geomorphological structures as well as anthropogenic activities such as soil management and buried drainage networks. To identify areas with similar subsurface structures, we applied image classification techniques. We fused ECa maps obtained with different coil distances in a multiband image and applied supervised and unsupervised classification methodologies. Both showed good results in reconstructing observed patterns in plant productivity and the subsurface structures associated with them. However, the supervised methodology proved more efficient in classifying the whole study area. In a second step, we selected hundred locations within the study area and obtained a soil profile description with type, depth, and thickness of the soil horizons. Using this ground truth data it was possible to assign a typical soil profile to each of the main classes obtained from the classification. The proposed methodology was

  17. High-quality unsaturated zone hydraulic property data for hydrologic applications

    USGS Publications Warehouse

    Perkins, Kimberlie; Nimmo, John R.

    2009-01-01

    In hydrologic studies, especially those using dynamic unsaturated zone moisture modeling, calculations based on property transfer models informed by hydraulic property databases are often used in lieu of measured data from the site of interest. Reliance on database-informed predicted values has become increasingly common with the use of neural networks. High-quality data are needed for databases used in this way and for theoretical and property transfer model development and testing. Hydraulic properties predicted on the basis of existing databases may be adequate in some applications but not others. An obvious problem occurs when the available database has few or no data for samples that are closely related to the medium of interest. The data set presented in this paper includes saturated and unsaturated hydraulic conductivity, water retention, particle-size distributions, and bulk properties. All samples are minimally disturbed, all measurements were performed using the same state of the art techniques and the environments represented are diverse.

  18. Towards operational hydrology for a thorough spatio-temporal exploration of the Critical Zone

    NASA Astrophysics Data System (ADS)

    Chatton, Eliot; Labasque, Thierry; Guillou, Aurélie; Aquilina, Luc; Bour, Olivier; Le Borgne, Tanguy; Longuevergne, Laurent

    2017-04-01

    Over the last century, the Critical Zone faced remarkable climate and land use changes increasing the pressures on the Hydrosphere and giving rise to numerous environmental consequences in terms of water quantity and quality. From now on, the Critical Zone must face the challenge to supply 9 billion people with quality food and safe drinking water in a context of global warming. For the Hydrosphere, this challenge could be addressed with a better understanding of the dynamics and resilience of aquatic environments (rivers, lakes, groundwaters, oceans). In view of the spatial and temporal variety and variability of flow dynamics and biogeochemical reactions occurring in the Hydrosphere a new investigation method is needed. This study approaches the concept of "operational hydrology" aiming to enhance either the spatio-temporal distribution and the quality of environmental data for a thorough exploration of the Hydrosphere. To illustrate our approach, we present natural and anthropogenic dissolved gas data (He, Ne, Ar, Kr, Xe, N2, O2, CO2, CH4, N2O, H2, BTEX, and some VOCs) measured in situ with a CF-MIMS (Chatton et al, 2016) installed in a mobile laboratory arranged in an all-terrain truck (CRITEX-Lab). This ongoing work focuses on groundwater and the field investigation of residence time distributions, recharge processes (origins), water flow paths and mixing, biogeochemical reactivity and contamination (sources). The rationale behind "operational hydrology" could be applied to the field measurement at high-frequency of many other environmental parameters (temperature, cations, anions, isotopes, micro-organisms) not only for the investigation of groundwaters but also rivers, lakes and oceans. Eliot Chatton, Thierry Labasque, Jérôme de La Bernardie, Nicolas Guihéneuf, Olivier Bour and Luc Aquilina; Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of Groundwater Flow; Environmental Science

  19. A metrics for soil hydrological processes and their intrinsic dimensionality in heterogeneous systems

    NASA Astrophysics Data System (ADS)

    Lischeid, G.; Hohenbrink, T.; Schindler, U.

    2012-04-01

    Hydrology is based on the observation that catchments process input signals, e.g., precipitation, in a highly deterministic way. Thus, the Darcy or the Richards equation can be applied to model water fluxes in the saturated or vadose zone, respectively. Soils and aquifers usually exhibit substantial spatial heterogeneities at different scales that can, in principle, be represented by corresponding parameterisations of the models. In practice, however, data are hardly available at the required spatial resolution, and accounting for observed heterogeneities of soil and aquifer structure renders models very time and CPU consuming. We hypothesize that the intrinsic dimensionality of soil hydrological processes, which is induced by spatial heterogeneities, actually is very low and that soil hydrological processes in heterogeneous soils follow approximately the same trajectory. That means, the way how the soil transforms any hydrological input signals is the same for different soil textures and structures. Different soils differ only with respect to the extent of transformation of input signals. In a first step, we analysed the output of a soil hydrological model, based on the Richards equation, for homogeneous soils down to 5 m depth for different soil textures. A matrix of time series of soil matrix potential and soil water content at 10 cm depth intervals was set up. The intrinsic dimensionality of that matrix was assessed using the Correlation Dimension and a non-linear principal component approach. The latter provided a metrics for the extent of transformation ("damping") of the input signal. In a second step, model outputs for heterogeneous soils were analysed. In a last step, the same approaches were applied to 55 time series of observed soil water content from 15 sites and different depths. In all cases, the intrinsic dimensionality in fact was very close to unity, confirming our hypothesis. The metrics provided a very efficient tool to quantify the observed

  20. Transport of Carbon Tetrachloride in a Fractured Vadose Zone due to Atmospheric Pressure Fluctuations, Diffusion, and Vapor Density

    NASA Astrophysics Data System (ADS)

    McCray, J. E.; Downs, W.; Falta, R. W.; Housley, T.

    2005-12-01

    DNAPL sources of carbon tetrachloride (CT) vapors are of interest at the Radioactive Waste Management Complex (RWMC) at the Idaho National Engineering and Environmental Laboratory (INEEL). The site is underlain by thick fractured basalt that includes sedimentary interbeds, each are a few meters thick. Daily atmospheric pressure fluctuations serve as driving forces for CT vapor transport in the subsurface. Other important transport processes for vapor movement include gas-phase diffusion and density-driven transport. The objective of this research is to investigate the influence and relative importance of these processes on gaseous transport of CT. Gas pressure and vapor concentration measurements were conducted at various depths in two wells. A numerical multiphase flow model (TOUGH2), calibrated to field pressure data, is used to conduct sensitivity analyses to elucidate the importance of the different transport mechanisms. Results show that the basalt is highly permeable to vertical air flow. The pressure dampening occurs mainly in the sedimentary interbeds. Model-calibrated permeability values for the interbeds are similar to those obtained in a study by the U.S. Geological Survey for shallow sediments, and an order of magnitude higher than column-scale values obtained by previous studies conducted by INEEL scientists. The transport simulations indicate that considering the effect of barometric pressure changes is critical to simulating transport of pollutants in the vadose zone above the DNAPL source. Predicted concentrations can be orders of magnitude smaller than actual concentrations if the effect is not considered. Below the DNAPL vapor source, accounting for density and diffusion alone would yield acceptable results provided that a 20% error in concentrations are acceptable, and that simulating concentrations trends (and not actual concentrations) is the primary goal.

  1. Understanding the Impacts of Climate Change and Land Use Dynamics Using a Fully Coupled Hydrologic Feedback Model between Surface and Subsurface Systems

    NASA Astrophysics Data System (ADS)

    Park, C.; Lee, J.; Koo, M.

    2011-12-01

    Climate is the most critical driving force of the hydrologic system of the Earth. Since the industrial revolution, the impacts of anthropogenic activities to the Earth environment have been expanded and accelerated. Especially, the global emission of carbon dioxide into the atmosphere is known to have significantly increased temperature and affected the hydrologic system. Many hydrologists have contributed to the studies regarding the climate change on the hydrologic system since the Intergovernmental Panel on Climate Change (IPCC) was created in 1988. Among many components in the hydrologic system groundwater and its response to the climate change and anthropogenic activities are not fully understood due to the complexity of subsurface conditions between the surface and the groundwater table. A new spatio-temporal hydrologic model has been developed to estimate the impacts of climate change and land use dynamics on the groundwater. The model consists of two sub-models: a surface model and a subsurface model. The surface model involves three surface processes: interception, runoff, and evapotranspiration, and the subsurface model does also three subsurface processes: soil moisture balance, recharge, and groundwater flow. The surface model requires various input data including land use, soil types, vegetation types, topographical elevations, and meteorological data. The surface model simulates daily hydrological processes for rainfall interception, surface runoff varied by land use change and crop growth, and evapotranspiration controlled by soil moisture balance. The daily soil moisture balance is a key element to link two sub-models as it calculates infiltration and groundwater recharge by considering a time delay routing through a vadose zone down to the groundwater table. MODFLOW is adopted to simulate groundwater flow and interaction with surface water components as well. The model is technically flexible to add new model or modify existing model as it is

  2. Using Airborne Geophysics to Improve the Management of Produced Water from Coal Bed Natural Gas Extraction in the Powder River Basin

    NASA Astrophysics Data System (ADS)

    Sams, J.; Lipinski, B.; Hammack, R.; Veloski, G.; Ackman, T.; Harbert, B.

    2005-05-01

    The Powder River Basin (PRB) of Wyoming and Montana has seen a boom in drilling for coalbed natural gas (CBNG), the natural gas contained in coal seams. Large quantities of water are coproduced during the extraction process. The water is currently managed by land application (irrigation), returned to shallow groundwater aquifers via infiltration basins, directly discharged to ephemeral or perennial streams, or injected into the deep subsurface via injection wells. At present, there are over 28,000 CBNG wells permitted or drilled in the PRB and it is estimated that another 50,000 to 100,000 new wells will be drilled in the future. Produced water management is a major challenge to the oil and gas industry as well as federal and state regulators. The purpose of this study was to evaluate the use of airborne electromagnetic (AEM) methods for the large-scale mapping of vadose zone properties. The base maps derived from the AEM data show the location of conductive anomalies within the vadose zone. These conductive anomalies have been identified as conditions related to soil properties, geologic features, saturated areas, and seepage zones. In the PRB, the data can be used to identify suitable locations for constructing impoundments in areas that avoid highly conductive soils where infiltrating water may leach salts through the vadose zone and into shallow aquifers. Hydrologic changes within the vadose zone were evaluated by completing an AEM survey in 2003 and 2004 over two coincident spatial areas. The data were analyzed to determine statistical relationships between the data sets, in particular data outliers which may represent areas of significant change between each year. Some outliers plot near areas of CBNG development. Ultimately, it is hoped that the information from these surveys will identify cost effective treatment or disposal options for produced water that address both production and environmental issues.

  3. The Annual Glaciohydrology Cycle in the Ablation Zone of the Greenland Ice Sheet: Part 1. Hydrology Model

    NASA Technical Reports Server (NTRS)

    Colgan, William; Rajaram, Harihar; Anderson, Robert; Steffen. Konrad; Phillips, Thomas; Zwally, H. Jay; Abdalati, Waleed

    2012-01-01

    We apply a novel one-dimensional glacier hydrology model that calculates hydraulic head to the tidewater-terminating Sermeq Avannarleq flowline of the Greenland ice sheet. Within a plausible parameter space, the model achieves a quasi-steady-state annual cycle in which hydraulic head oscillates close to flotation throughout the ablation zone. Flotation is briefly achieved during the summer melt season along a approx.17 km stretch of the approx.50 km of flowline within the ablation zone. Beneath the majority of the flowline, subglacial conduit storage closes (i.e. obtains minimum radius) during the winter and opens (i.e. obtains maximum radius) during the summer. Along certain stretches of the flowline, the model predicts that subglacial conduit storage remains open throughout the year. A calculated mean glacier water residence time of approx.2.2 years implies that significant amounts of water are stored in the glacier throughout the year. We interpret this residence time as being indicative of the timescale over which the glacier hydrologic system is capable of adjusting to external surface meltwater forcings. Based on in situ ice velocity observations, we suggest that the summer speed-up event generally corresponds to conditions of increasing hydraulic head during inefficient subglacial drainage. Conversely, the slowdown during fall generally corresponds to conditions of decreasing hydraulic head during efficient subglacial drainage.

  4. In Situ Bioremediation of Perchlorate in Vadose Zone Source Areas

    DTIC Science & Technology

    2011-01-01

    agricultural bags (e.g., ITRC, 2008; Evans et al., 2008). Phytoremediation has also been tested for soil treatment (ITRC, 2008). However, these...within the saturated zone (through in situ bioremediation or groundwater extraction and ex-situ treatment), phytoremediation , which is unlikely to

  5. Representation of Stormflow and a More Responsive Water Table in a TOPMODEL-Based Hydrology Model

    NASA Technical Reports Server (NTRS)

    Shaman, Jeffrey; Stieglitz, Marc; Engel, Victor; Koster, Randal; Stark, Colin; Houser, Paul R. (Technical Monitor)

    2001-01-01

    This study presents two new modeling strategies. First, a methodology for representing the physical process of stormflow within a TOPMODEL framework is developed. In using this approach, discharge at quickflow time scales is simulated and a fuller depiction of hydrologic activity is brought about. Discharge of water from the vadose zone is permitted in a physically realistic manner without a priori assumption of the level within the soil column at which stormflow saturation can take place. Determination of the stormflow contribution to discharge is made using the equation for groundwater flow. No new parameters are needed. Instead, regions of near saturation that develop during storm events, producing vertical recharge, are allowed to contribute to soil column discharge. These stormflow contributions to river runoff, as for groundwater flow contributions, are a function of catchment topography and local hydraulic conductivity at the depth of these regions of near saturation. The second approach improves groundwater flow response through a reduction of porosity and field capacity with depth in the soil column. Large storm events are better captured and a more dynamic water table develops with application of this modified soil column profile (MSCP). The MSCP predominantly reflects soil depth differences in upland and lowland regions of a watershed. Combined, these two approaches - stormflow and the MSCP - provide a more accurate representation of the time scales at which soil column discharge responds and a more complete depiction of hydrologic activity. Storm events large and small are better simulated, and some of the biases previously evident in TOPMODEL simulations are reduced.

  6. Radionuclide field lysimeter experiment (RadFLEx): geochemical and hydrological data for SRS performance assessments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaplan, D.; Powell, B.; Barber, K.

    The SRNL Radiological Field Lysimeter Experiment (RadFLEx) is a one-of-a-kind test bed facility designed to study radionuclide geochemical processes in the Savannah River Site (SRS) vadose zone at a larger spatial scale (from grams to tens of kilograms of sediment) and temporal scale (from months to decade) than is readily afforded through laboratory studies. RadFLEx is a decade-long project that was initiated on July 5, 2012 and is funded by six different sources. The objective of this status report is as follows: 1) to report findings to date that have an impact on SRS performance assessment (PA) calculations, and 2)more » to provide performance metrics of the RadFLEx program. The PA results are focused on measurements of transport parameters, such as distribution coefficients (Kd values), solubility, and unsaturated flow values. As this is an interim report, additional information from subsequent research may influence our interpretation of current results. Research related to basic understanding of radionuclide geochemistry in these vadose zone soils and other source terms are not described here but are referenced for the interested reader.« less

  7. Laboratory and numerical experiments on water and energy fluxes during freezing and thawing in the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Holländer, Hartmut; Montasir Islam, Md.; Šimunek, Jirka

    2017-04-01

    Frozen soil has a major effect in many hydrologic processes, and its effects are difficult to predict. A prime example is flood forecasting during spring snowmelt within the Canadian Prairies. One key driver for the extent of flooding is the antecedent soil moisture and the possibility for water to infiltrate into frozen soils. Therefore, these situations are crucial for accurate flood prediction during every spring. The main objective of this study was to evaluate the water flow and heat transport within HYDRUS-1D version 4.16 and with Hansson's model, which is a detailed freezing/thawing module (Hansson et al., 2004), to predict the impact of frozen and partly frozen soil on infiltration. We developed a standardized data set of water flow and heat transport into (partial) frozen soil by laboratory experiments using fine sand. Temperature, soil moisture, and percolated water were observed at different freezing conditions as well as at thawing conditions. Significant variation in soil moisture was found between the top and the bottom of the soil column at the starting of the thawing period. However, with increasing temperature, the lower depth of the soil column showed higher moisture as the soil became enriched with moisture due to the release of heat by soil particles during the thawing cycle. We applied vadose zone modeling using the results from the laboratory experiments. The simulated water content by HYDRUS-1D 4.16 showed large errors compared to the observed data showing by negative Nash-Sutcliffe Efficiency. Hansson's model was not able to predict soil water fluxes due to its unstable behavior (Šimunek et al., 2016). The soil temperature profile simulated using HYDRUS-1D 4.16 was not able to predict the release of latent heat during the phase change of water that was visible in Hansson's model. Hansson's model includes the energy gain/loss due to the phase change in the amount of latent energy stored in the modified heat transport equation. However, in

  8. Influence of Hydrological Perturbations and Riverbed Sediment Characteristics on Hyporheic Zone Respiration of CO2 and N2

    NASA Astrophysics Data System (ADS)

    Newcomer, Michelle E.; Hubbard, Susan S.; Fleckenstein, Jan H.; Maier, Ulrich; Schmidt, Christian; Thullner, Martin; Ulrich, Craig; Flipo, Nicolas; Rubin, Yoram

    2018-03-01

    Rivers in climatic zones characterized by dry and wet seasons often experience periodic transitions between losing and gaining conditions across the river-aquifer continuum. Infiltration shifts can stimulate hyporheic microbial biomass growth and cycling of riverine carbon and nitrogen leading to major exports of biogenic CO2 and N2 to rivers. In this study, we develop and test a numerical model that simulates biological-physical feedback in the hyporheic zone. We used the model to explore different initial conditions in terms of dissolved organic carbon availability, sediment characteristics, and stochastic variability in aerobic and anaerobic conditions from water table fluctuations. Our results show that while highly losing rivers have greater hyporheic CO2 and N2 production, gaining rivers allowed the greatest fraction of CO2 and N2 production to return to the river. Hyporheic aerobic respiration and denitrification contributed 0.1-2 g/m2/d of CO2 and 0.01-0.2 g/m2/d of N2; however, the suite of potential microbial behaviors varied greatly among sediment characteristics. We found that losing rivers that consistently lacked an exit pathway can store up to 100% of the entering C/N as subsurface biomass and dissolved gas. Our results demonstrate the importance of subsurface feedbacks whereby microbes and hydrology jointly control fate of C and N and are strongly linked to wet-season control of initial sediment conditions and hydrologic control of seepage direction. These results provide a new understanding of hydrobiological and sediment-based controls on hyporheic zone respiration, including a new explanation for the occurrence of anoxic microzones and large denitrification rates in gravelly riverbeds.

  9. [Spatial and temporal variations of hydrological characteristic on the landscape zone scale in alpine cold region].

    PubMed

    Yang, Yong-Gang; Hu, Jin-Fei; Xiao, Hong-Lang; Zou, Song-Bing; Yin, Zhen-Liang

    2013-10-01

    There are few studies on the hydrological characteristics on the landscape zone scale in alpine cold region at present. This paper aimed to identify the spatial and temporal variations in the origin and composition of the runoff, and to reveal the hydrological characteristics in each zone, based on the isotopic analysis of glacier, snow, frozen soil, groundwater, etc. The results showed that during the wet season, heavy precipitation and high temperature in the Mafengou River basin caused secondary evaporation which led to isotope fractionation effects. Therefore, the isotope values remained high. Temperature effects were significant. During the dry season, the temperature was low. Precipitation was in the solid state during the cold season and the evaporation was weak. Water vapor came from the evaporation of local water bodies. Therefore, less secondary evaporation and water vapor exchange occurred, leading to negative values of delta18O and deltaD. delta18O and deltaD values of precipitation and various water bodies exhibited strong seasonal variations. Precipitation exhibited altitude effects, delta18O = -0. 005 2H - 8. 951, deltaD = -0.018 5H - 34. 873. Other water bodies did not show altitude effects in the wet season and dry season, because the runoff was not only recharged by precipitation, but also influenced by the freezing and thawing process of the glacier, snow and frozen soil. The mutual transformation of precipitation, melt water, surface water and groundwater led to variations in isotopic composition. Therefore, homogenization and evaporation effect are the main control factors of isotope variations.

  10. Hydrologic evaluation methodology for estimating water movement through the unsaturated zone at commercial low-level radioactive waste disposal site

    USGS Publications Warehouse

    Meyer, P.D.; Rockhold, M.L.; Nichols, W.E.; Gee, G.W.

    1996-01-01

    This report identifies key technical issues related to hydrologic assessment of water flow in the unsaturated zone at low-level radioactive waste (LLW) disposal facilities. In addition, a methodology for incorporating these issues in the performance assessment of proposed LLW disposal facilities is identified and evaluated. The issues discussed fall into four areas:Estimating the water balance at a site (i.e., infiltration, runoff, water storage, evapotranspiration, and recharge);Analyzing the hydrologic performance of engineered components of a facility;Evaluating the application of models to the prediction of facility performance; andEstimating the uncertainty in predicted facility performance.An estimate of recharge at a LLW site is important since recharge is a principal factor in controlling the release of contaminants via the groundwater pathway. The most common methods for estimating recharge are discussed in Chapter 2. Many factors affect recharge; the natural recharge at an undisturbed site is not necessarily representative either of the recharge that will occur after the site has been disturbed or of the flow of water into a disposal facility at the site. Factors affecting recharge are discussed in Chapter 2.At many sites engineered components are required for a LLW facility to meet performance requirements. Chapter 3 discusses the use of engineered barriers to control the flow of water in a LLW facility, with a particular emphasis on cover systems. Design options and the potential performance and degradation mechanisms of engineered components are also discussed.Water flow in a LLW disposal facility must be evaluated before construction of the facility. In addition, hydrologic performance must be predicted over a very long time frame. For these reasons, the hydrologic evaluation relies on the use of predictive modeling. In Chapter 4, the evaluation of unsaturated water flow modeling is discussed. A checklist of items is presented to guide the evaluation

  11. Utilizing High-Performance Computing to Investigate Parameter Sensitivity of an Inversion Model for Vadose Zone Flow and Transport

    NASA Astrophysics Data System (ADS)

    Fang, Z.; Ward, A. L.; Fang, Y.; Yabusaki, S.

    2011-12-01

    High-resolution geologic models have proven effective in improving the accuracy of subsurface flow and transport predictions. However, many of the parameters in subsurface flow and transport models cannot be determined directly at the scale of interest and must be estimated through inverse modeling. A major challenge, particularly in vadose zone flow and transport, is the inversion of the highly-nonlinear, high-dimensional problem as current methods are not readily scalable for large-scale, multi-process models. In this paper we describe the implementation of a fully automated approach for addressing complex parameter optimization and sensitivity issues on massively parallel multi- and many-core systems. The approach is based on the integration of PNNL's extreme scale Subsurface Transport Over Multiple Phases (eSTOMP) simulator, which uses the Global Array toolkit, with the Beowulf-Cluster inspired parallel nonlinear parameter estimation software, BeoPEST in the MPI mode. In the eSTOMP/BeoPEST implementation, a pre-processor generates all of the PEST input files based on the eSTOMP input file. Simulation results for comparison with observations are extracted automatically at each time step eliminating the need for post-process data extractions. The inversion framework was tested with three different experimental data sets: one-dimensional water flow at Hanford Grass Site; irrigation and infiltration experiment at the Andelfingen Site; and a three-dimensional injection experiment at Hanford's Sisson and Lu Site. Good agreements are achieved in all three applications between observations and simulations in both parameter estimates and water dynamics reproduction. Results show that eSTOMP/BeoPEST approach is highly scalable and can be run efficiently with hundreds or thousands of processors. BeoPEST is fault tolerant and new nodes can be dynamically added and removed. A major advantage of this approach is the ability to use high-resolution geologic models to preserve

  12. Hydrogeologic characterization of an arid zone Radioactive Waste Management Site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ginanni, J.M.; O`Neill, L.J.; Hammermeister, D.P.

    1994-06-01

    An in-depth subsurface site characterization and monitoring program for the soil water migration pathway has been planned, implemented, and completed to satisfy data requirements for a waiver from groundwater monitoring, for an exemption from liner leachate collections systems, and for different regulatory driven performance assessments. A traditional scientific approach has been taken to focus characterization and monitoring efforts. This involved developing a conceptual model of the hydrogeologic system and defining and testing hypotheses about this model. Specific hypotheses tested included: that the system was hydrologically heterogenous and anisotropic, and that recharge was very low or negligible. Mineralogical, physical, and hydrologicmore » data collected to test hypotheses has shown the hydrologic system to be remarkably homogenous and isotropic rather than heterogenous and anisotropic. Both hydrodynamic and environmental tracer approaches for estimating recharge have led to the conclusion that recharge from the Area 5 RWMS is not occurring in the upper region of the vadose zone, and that recharge at depth is extremely small or negligible. This demonstration of ``no migration of hazardous constituents to the water table satisfies a key requirement for both the groundwater monitoring waiver and the exemption from liner leachate collection systems. Data obtained from testing hypotheses concerning the soil water migration pathway have been used to refine the conceptual model of the hydrogeologic system of the site. These data suggest that the soil gas and atmospheric air pathways may be more important for transporting contaminants to the accessible environment than the soil water pathway. New hypotheses have been developed about these pathways, and characterization and monitoring activities designed to collect data to test these hypotheses.« less

  13. Traditional and innovative methods applied to a crystalline aquifer for characterizing fault zone hydrology at different scales

    NASA Astrophysics Data System (ADS)

    Bour, O.; Ruelleu, S.; Le Borgne, T.; Boudin, F.; Moreau, F.; Durand, S.; Longuevergne, L.

    2011-12-01

    Crystalline rocks aquifers are difficult to characterize since flow is mainly localized in few fractures or faults. In particular, the geometry of the main flow paths and the connections of the aquifer with the sub-surface are often poorly constrained. Here, we present results from different geophysical and hydraulic methods to quantify fault zone hydrology of a crystalline confined aquifer (Ploemeur, French Brittany). This outstandingly productive crystalline rock aquifer is exploited at a rate of about 10 6 m3 per year since 1991. The pumping site is located at the intersection of two main structures: the contact zone between granite roof and overlying micaschists, and a steeply dipping fault striking North 20°, with combined dextral strike-slip and normal components. Core samples and borehole optical imagery reveals that the contact zone at the granite roof consists of alternating deformed granitic sheets and enclaves of micaschists, pegmatite and aplite dykes, as well as quartz veins. Locally, this contact is marked by mylonites and pegmatite-bearing breccias that are often but not systematically associated with major borehole inflows. Other significant inflows are localized within single fractures independently of the lithologies encountered. At the borehole scale the structural and hydraulic properties of the aquifer are thus highly variable. At the site scale - typically a kilometer squared - the water levels are monitored in 22 boreholes, 100 meters deep in average. The connectivity of the main flow paths and the hydraulic properties are relatively well constrained and quantified thanks to cross-borehole flowmeter tests and traditional pumping tests. In complement, long-base tiltmeters monitoring and ground-surface leveling allows to monitor sub-surface deformation. It provides a quantification of the hydro-mechanical properties of the aquifer and better constraints about the geometry of the main fault zone. Surprisingly, the storage coefficient of the

  14. Hydrologic Monitoring in the Deep Subsurface to Support Repository Performance

    NASA Astrophysics Data System (ADS)

    Hubbell, J. M.; Heath, G. L.; Scott, C. L.

    2007-12-01

    The INL has installed and operated several vadose and ground water monitoring systems in arid and humid sites to depths of about 200m. Some of these systems have been in continuous operation for over 12 years. It is important that the systems be physically robust, simple, yet versatile enough that it can operate for extended time periods with little or no maintenance. Monitoring instruments are frequently installed and run to characterize the site, collect data during site operation, and continue to run for long-term stewardship, necessitating sensors that can be maintained or serviced. Sensors are carefully chosen based on the perceived data requirements over the life of the site. An emphasis is given on direct measurements such as tensiometers (portable and advanced), neutron probe, drain gauge, temperature, wells or sampling for fluids and gases. Other complementary data can include using TDR/capacitance, radiation detectors, and larger scale geophysical techniques (3-d resistivity and EM) for volumetric measurements. Commercially available instruments may have to be modified for their use at greater depths, to allow multiple instruments in a single borehole or to perform the intended monitoring function. Access tubes (some open at the bottom) can be placed to allow insertion of multiple sensors (radiation, neutron and portable sensors/samplers), future drilling/sampling and to install new instruments at a later time. The installation techniques and backfill materials must be chosen and the measurement technique tested to ensure representative data collection for the parameters of interest. The data collection system can be linked to climatic data (precipitation, barometric pressure, snow depth, runoff, surface water sources) that may influence the site's subsurface hydrology. The instruments are then connected to a real-time automated data collection system that collect, stores, and provides access to the data. These systems have been developed that allow easy

  15. CO2 leakage monitoring and analysis to understand the variation of CO2 concentration in vadose zone by natural effects

    NASA Astrophysics Data System (ADS)

    Joun, Won-Tak; Ha, Seung-Wook; Kim, Hyun Jung; Ju, YeoJin; Lee, Sung-Sun; Lee, Kang-Kun

    2017-04-01

    Controlled ex-situ experiments and continuous CO2 monitoring in the field are significant implications for detecting and monitoring potential leakage from CO2 sequestration reservoir. However, it is difficult to understand the observed parameters because the natural disturbance will fluctuate the signal of detections in given local system. To identify the original source leaking from sequestration reservoir and to distinguish the camouflaged signal of CO2 concentration, the artificial leakage test was conducted in shallow groundwater environment and long-term monitoring have been performed. The monitoring system included several parameters such as pH, temperature, groundwater level, CO2 gas concentration, wind speed and direction, atmospheric pressure, borehole pressure, and rainfall event etc. Especially in this study, focused on understanding a relationship among the CO2 concentration, wind speed, rainfall and pressure difference. The results represent that changes of CO2 concentration in vadose zone could be influenced by physical parameters and this reason is helpful in identifying the camouflaged signal of CO2 concentrations. The 1-D column laboratory experiment also was conducted to understand the sparking-peak as shown in observed data plot. The results showed a similar peak plot and could consider two assumptions why the sparking-peak was shown. First, the trapped CO2 gas was escaped when the water table was changed. Second, the pressure equivalence between CO2 gas and water was broken when the water table was changed. These field data analysis and laboratory experiment need to advance due to comprehensively quantify local long-term dynamics of the artificial CO2 leaking aquifer. Acknowledgement Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003)

  16. Prospects for hydrologic classification of landscapes and watersheds

    EPA Science Inventory

    The ecological functions of streams and associated riparian zones are strongly influenced by the hydrological attributes of watersheds and landscapes in which they occur. Oregon hydrologic landscape regions (HLRs) have been defined based on four types of GIS data: 1) climate, 2) ...

  17. Sorption and mineralization of S-metolachlor and its ionic metabolites in soils and vadose zone solids: consequences on groundwater quality in an alluvial aquifer (Ain Plain, France).

    PubMed

    Baran, Nicole; Gourcy, Laurence

    2013-11-01

    This study characterizes the transfer of S-metolachlor (SMOC) and its metabolites, metolachlor ethane sulfonic acid (MESA) and metolachlor oxanilic acid (MOXA) to the alluvial aquifer. Sorption and mineralization of SMOC and its two ionic metabolites were characterized for cultivated soils and solids from the vadose (unsaturated) zone in the Ain Plain (France). Under sterile soil conditions, the absence of mineralization confirms the importance of biotic processes in SMOC degradation. There is some adsorption and mineralization of the parent molecule and its metabolites in the unsaturated zone, though less than in soils. For soils, the MESA adsorption constant is statistically higher than that of MOXA and the sorption constants of the two metabolites are significantly lower than that of SMOC. After 246 days, for soils, maximums of 26% of the SMOC, 30% of the MESA and 38% of the MOXA were mineralized. This partly explains the presence of these metabolites in the groundwater at concentrations generally higher than those of the parent molecule for MESA, although there is no statistical difference in the mineralization of the 3 molecules. The laboratory results make it possible to explain the field observations made during 27 months of groundwater quality monitoring (monthly sampling frequency). The evolution of both metabolite concentrations in the groundwater is directly related to recharge dynamics; there is a positive correlation between concentrations and the groundwater level. The observed lag of several months between the signals of the parent molecule and those of the metabolites is probably due to greater sorption of the parent molecule than of its metabolites and/or to degradation kinetics. © 2013.

  18. Hydrologic flow path development varies by aspect during spring snowmelt in complex subalpine terrain

    NASA Astrophysics Data System (ADS)

    Webb, Ryan W.; Fassnacht, Steven R.; Gooseff, Michael N.

    2018-01-01

    In many mountainous regions around the world, snow and soil moisture are key components of the hydrologic cycle. Preferential flow paths of snowmelt water through snow have been known to occur for years with few studies observing the effect on soil moisture. In this study, statistical analysis of the topographical and hydrological controls on the spatiotemporal variability of snow water equivalent (SWE) and soil moisture during snowmelt was undertaken at a subalpine forested setting with north, south, and flat aspects as a seasonally persistent snowpack melts. We investigated if evidence of preferential flow paths in snow can be observed and the effect on soil moisture through measurements of snow water equivalent and near-surface soil moisture, observing how SWE and near-surface soil moisture vary on hillslopes relative to the toes of hillslopes and flat areas. We then compared snowmelt infiltration beyond the near-surface soil between flat and sloping terrain during the entire snowmelt season using soil moisture sensor profiles. This study was conducted during varying snowmelt seasons representing above-normal, relatively normal, and below-normal snow seasons in northern Colorado. Evidence is presented of preferential meltwater flow paths at the snow-soil interface on the north-facing slope causing increases in SWE downslope and less infiltration into the soil at 20 cm depth; less association is observed in the near-surface soil moisture (top 7 cm). We present a conceptualization of the meltwater flow paths that develop based on slope aspect and soil properties. The resulting flow paths are shown to divert at least 4 % of snowmelt laterally, accumulating along the length of the slope, to increase the snow water equivalent by as much as 170 % at the base of a north-facing hillslope. Results from this study show that snow acts as an extension of the vadose zone during spring snowmelt and future hydrologic investigations will benefit from studying the snow and soil

  19. Spatial and temporal variation of denitrification in the riparian zone during the hydrological year

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Musolff, Andreas; Knöller, Kay; Fleckenstein, Jan H.

    2017-04-01

    In the riparian zone, where stream water mixes with groundwater, biogeochemical reactions and solute transformations occur which may enhance the self-cleaning mechanisms of aquatic ecosystems. The water exchange and solute transport through the riparian zone is controlled by hydraulic gradients between stream and groundwater and thus varies seasonally and during stream discharge events. In this study, we focus on transport, mixing and the distribution of nitrate in the riparian zone of a gravelly alluvial aquifer with the aim to quantify its denitrification potential during the hydrological year. For this purpose, 25 groundwater wells were drilled along a 2 km stream section of the Selke river, a third-order stream in Germany. From the stream and the wells, water samples were taken 4-weekly over a period of 2 years. Water samples were analyzed to field parameters, major ions, dissolved organic carbon, and N-O isotopes. Results show a strong influence of the stream on the adjacent groundwater, which varies both in time and space. In general, we can distinguish between two endmembers: a) the stream water with low chloride (<30 mg/L) and nitrate (<10 mg/L) concentrations and b) the groundwater in 100m distance to the stream with high chloride (>70 mg/L) and nitrate (>50 mg/L) concentrations. Based on conservatively transported chloride, the mixing of the endmembers can be determined in the riparian zone. Deviations in nitrate concentrations from this mixing model may indicate nitrate degradation by e.g. denitrification. By combining this chloride-nitrate-ratio method with dissolved oxygen data and the isotopic signature of the nitrate molecule, we are able to determine the timing and the location of high denitrification patterns in the riparian aquifer. Highest variability of denitrification occurs over the year in terms of seasonality (temperature-driven) and is temporally fueled by additional organic carbon supply during discharge events.

  20. Riparian zone hydrology and biogeochemistry as a function of stream evolution stage in glaciated landscapes of the US Northeast

    NASA Astrophysics Data System (ADS)

    Rook, S. P.; Vidon, P.; Walter, M. T.

    2011-12-01

    The management of riparian buffer strips is often regarded as one of the most economical and sustainable methods of managing non-point source pollution and water quality. However, current riparian management often follows a 'one size fits all' design, which fails to recognize the complexity of the many biogeochemical processes that regulate pollutant transformation and retention in these systems. This study addresses two critical gaps in knowledge: (1) How carbon, nitrogen, phosphorous, and iron cycles interact with one another (rather than individually). (2) How stream channel geometry and evolution regulate these nutrient cycles and greenhouse gas (GHG) dynamics in the near stream zone. This project specifically explores the hydrological and biogeochemical functioning of riparian zones across a gradient of stream meander evolution stages, with the primary goal of understanding and predicting potential interactions between nutrient dynamics in these systems. Key research questions include: (1) How does stream meander curvature affect riparian zone hydrology? (2) How does stream meander curvature influence riparian zone biogeochemistry? (3) What relationships exist among N, P, Fe, and GHG dynamics? We instrumented three riparian sites near Ithaca, NY, with a dense network of wells, piezometers, and static chambers. These sites represent three riparian zones along three evolution stages of stream meanders: an inner meander, a straight stream section, and an outer bend of the stream with an oxbow lake formation. In spring through fall 2011, water samples and gas samples were collected at a tri-weekly bases at each of the three sites. Water samples were analyzed for oxidation-reduction potential, dissolved oxygen, temperature, FeII/FeIII, nutrients (NO3-, NH4+, PO43-) and dissolved organic carbon (DOC). GHG fluxes at the soil-atmosphere interface were measured for N2O, CO2, and CH4 gases. We predict that stream curvature will significantly affect groundwater flow

  1. Hydrologic exchanges and baldcypress water use on deltaic hummocks, Louisiana, USA

    USGS Publications Warehouse

    Hsueh, Yu-Hsin; Chambers, Jim L.; Krauss, Ken W.; Allen, Scott T.; Keim, Richard F.

    2016-01-01

    Coastal forested hummocks support clusters of trees in the saltwater–freshwater transition zone. To examine how hummocks support trees in mesohaline sites that are beyond physiological limits of the trees, we used salinity and stable isotopes (2H and 18O) of water as tracers to understand water fluxes in hummocks and uptake by baldcypress (Taxodium distichum (L.) Rich.), which is the most abundant tree species in coastal freshwater forests of the southeastern U.S. Hummocks were always partially submerged and were completely submerged 1 to 8% of the time during the two studied growing seasons, in association with high water in the estuary. Salinity, δ18O, and δ2H varied more in the shallow open water than in groundwater. Surface water and shallow groundwater were similar to throughfall in isotopic composition, which suggested dominance by rainfall. Salinity of groundwater in hummocks increased with depth, was higher than in swales, and fluctuated little over time. Isotopic composition of xylem water in baldcypress was similar to the vadose zone and unlike other measured sources, indicating that trees preferentially use unsaturated hummock tops as refugia from higher salinity and saturated soil in swales and the lower portions of hummocks. Sustained upward gradients of salinity from groundwater to surface water and vadose water, and low variation in groundwater salinity and isotopic composition, suggested long residence time, limited exchange with surface water, and that the shallow subsurface of hummocks is characterized by episodic salinization and slow dilution.

  2. Transuranic Contamination in Sediment and Groundwater at the U.S. DOE Hanford Site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cantrell, Kirk J.

    2009-08-20

    transuranic radionuclides have been co-disposed with acidic liquid waste, transport through the vadose zone for considerable distances has occurred. For example, at the 216-Z-9 Crib, plutonium-239 and americium-241 have moved to depths in excess of 36 m (118 ft) bgs. Acidic conditions increase the solubility of these contaminants and reduce adsorption to mineral surfaces. Subsequent neutralization of the acidity by naturally occurring calcite in the vadose zone (particularly in the Cold Creek unit) appears to have effectively stopped further migration. The vast majority of transuranic contaminants disposed to the vadose zone on the Hanford Site (10,200 Ci [86%] of plutonium-239; 27,900 Ci [97%] of americium-241; and 41.8 Ci [78%] of neptunium-237) were disposed in sites within the PFP Closure Zone. This closure zone is located within the 200 West Area (see Figures 1.1 and 3.1). Other closure zones with notably high quantities of transuranic contaminant disposal include the T Farm Zone with 408 Ci (3.5%) plutonium-239, the PUREX Zone with 330 Ci (2.8%) plutonium-239, 200-W Ponds Zone with 324 Ci (2.8%) plutonium-239, B Farm Zone with 183 Ci (1.6%) plutonium-239, and the REDOX Zone with 164 Ci (1.4%) plutonium 239. Characterization studies for most of the sites reviewed in the document are generally limited. The most prevalent characterization methods used were geophysical logging methods. Characterization of a number of sites included laboratory analysis of borehole sediment samples specifically for radionuclides and other contaminants, and geologic and hydrologic properties. In some instances, more detailed research level studies were conducted. Results of these studies were summarized in the document.« less

  3. Mycorrhizal colonization across hydrologic gradients in restored and reference freshwater wetlands

    USGS Publications Warehouse

    Bauer, C.R.; Kellogg, C.H.; Bridgham, S.D.; Lamberti, G.A.

    2003-01-01

    Arbuscular mycorrhizae, which are plant root-fungal symbioses, are common associates of vascular plants. Such relationships, however, are thought to be rare in wetland plant roots, although several recent studies suggest that arbuscular mycorrhizae may be important in wetland ecosystems. Our objectives were to determine (1) the level of arbuscular mycorrhizal colonization of plant roots in three freshwater marshes and (2) the effect of restoration status, hydrologic zone, and plant species identity on mycorrhizal colonization. We quantified the percentage of plant roots colonized by mycorrhizal fungi in one reference and two restored freshwater marshes in northern Indiana, USA during summer 1999. Roots were collected from soil cores taken around dominant plant species present in each of three hydrologic zones and then stained for microscopic examination of mycorrhizal colonization. Mycorrhizae were present in each wetland, in all hydrologic zones and in all sampled plants, including Carex and Scirpus species previously thought to be non-mycorrhizal. Both restored and reference wetlands had moderate levels of mycorrhizal colonization, but no clear trends in colonization were seen with hydrologic zone, which has been hypothesized to regulate the formation of mycorrhizae in wetlands. Mycorrhizal colonization levels in the roots of individual species ranged from 3 to 90% and were particularly large in members of the Poaceae (grass) family. Our results suggest that arbuscular mycorrhizae may be widely distributed across plant species and hydrologic zones in both restored and reference freshwater marshes. Thus, future research should examine the functional role of mycorrhizal fungi in freshwater wetlands. ?? 2003, The Society of Wetland Scientists.

  4. Evaluation of air sparging and vadose zone aeration for remediation of iron and manganese-impacted groundwater at a closed municipal landfill.

    PubMed

    Pleasant, Saraya; O'Donnell, Amanda; Powell, Jon; Jain, Pradeep; Townsend, Timothy

    2014-07-01

    High concentrations of iron (Fe(II)) and manganese (Mn(II)) reductively dissolved from soil minerals have been detected in groundwater monitoring wells near many municipal solid waste landfills. Air sparging and vadose zone aeration (VZA) were evaluated as remedial approaches at a closed, unlined municipal solid waste landfill in Florida, USA. The goal of aeration was to oxidize Fe and Mn to their respective immobile forms. VZA and shallow air sparging using a partially submerged well screen were employed with limited success (Phase 1); decreases in dissolved iron were observed in three of nine monitoring wells during shallow air sparging and in two of 17 wells at VZA locations. During Phase 2, where deeper air sparging was employed, dissolved iron levels decreased in a significantly greater number of monitoring wells surrounding injection points, however no radial pattern was observed. Additionally, in wells affected positively by air sparging (mean total iron (FeTOT) <4.2mg/L, after commencement of air sparging), rising manganese concentrations were observed, indicating that the redox potential of the groundwater moved from an iron-reducing to a manganese-reducing environment. The mean FeTOT concentration observed in affected monitoring wells throughout the study was 1.40 mg/L compared to a background of 15.38 mg/L, while the mean Mn concentration was 0.60 mg/L compared to a background level of 0.27 mg/L. Reference wells located beyond the influence of air sparging areas showed little variation in FeTOT and Mn, indicating the observed effects were the result of air injection activities at study locations and not a natural phenomenon. Air sparging was found effective in intercepting plumes of dissolved Fe surrounding municipal landfills, but the effect on dissolved Mn was contrary to the desired outcome of decreased Mn groundwater concentrations. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Inverse modeling of hydrologic parameters using surface flux and runoff observations in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Hou, Z.; Huang, M.; Tian, F.; Leung, L. Ruby

    2013-12-01

    This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Both deterministic least-square fitting and stochastic Markov-chain Monte Carlo (MCMC)-Bayesian inversion approaches are evaluated by applying them to CLM4 at selected sites with different climate and soil conditions. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find that using model parameters calibrated by the sampling-based stochastic inversion approaches provides significant improvements in the model simulations compared to using default CLM4 parameter values, and that as more information comes in, the predictive intervals (ranges of posterior distributions) of the calibrated parameters become narrower. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.

  6. Using a spatially-distributed hydrologic biogeochemistry model to study the spatial variation of carbon processes in a Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Shi, Y.; Eissenstat, D. M.; Davis, K. J.; He, Y.

    2016-12-01

    Forest carbon processes are affected by, among other factors, soil moisture, soil temperature, soil nutrients and solar radiation. Most of the current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve the topographically driven hill-slope land surface heterogeneity or the spatial pattern of nutrient availability. A spatially distributed forest ecosystem model, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while soil nitrogen is transported among model grids via subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation information, while BBGC provides Flux-PIHM with leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). Model results suggest that the vegetation and soil carbon distribution is primarily constrained by nitorgen availability (affected by nitorgen transport via topographically driven subsurface flow), and also constrained by solar radiation and root zone soil moisture. The predicted vegetation and soil carbon distribution generally agrees with the macro pattern observed within the watershed. The coupled ecosystem-hydrologic model provides an important tool to study the impact of topography on watershed carbon processes, as well as the impact of climate change on water resources.

  7. Assessing the hydrological response from an ensemble of CMIP5 climate projections in the transition zone of the Atlantic region (Bay of Biscay)

    NASA Astrophysics Data System (ADS)

    Meaurio, Maite; Zabaleta, Ane; Boithias, Laurie; Epelde, Ane Miren; Sauvage, Sabine; Sánchez-Pérez, Jose-Miguel; Srinivasan, Raghavan; Antiguedad, Iñaki

    2017-05-01

    The climate changes projected for the 21st century will have consequences on the hydrological response of catchments. These changes, and their consequences, are most uncertain in the transition zones. The study area, in the Bay of Biscay, is located in the transition zone of the European Atlantic region, where hydrological impact of climate change was scarcely studied. In order to address this scarcity, the hydrological impacts of climate change on river discharge were assessed. To do so, a hydrological modelling was carried out considering 16 climate scenarios that include 5 General Circulation Models (GCM) from the 5th report of the Coupled Model Intercomparison Project (CMIP5), 2 statistical downscaling methods and 2 Representative Concentration Pathways. Projections for future discharge (2011-2100) were divided into three 30-year horizons (2030s, 2060s and 2090s) and a comparison was made between these time horizons and the baseline (1961-2000). The results show that the downscaling method used resulted in a higher source of uncertainty than GCM itself. In addition, the uncertainties inherent to the methods used at all the levels do not affect the results equally along the year. In spite of those uncertainties, general trends for the 2090s predict seasonal discharge decreases by around -17% in autumn, -16% in spring, -11% in winter and -7% in summer. These results are in line with those predicted for the Atlantic region (France and the Iberian Peninsula). Trends for extreme flows were also analysed: the most significant show an increase in the duration (days) of low flows. From an environmental point of view, and considering the need to meet the objectives established by the Water Framework Directive (WFD), this will be a major challenge for the future planning on water management.

  8. Hydrological deformation signals in karst systems: new evidence from the European Alps

    NASA Astrophysics Data System (ADS)

    Serpelloni, E.; Pintori, F.; Gualandi, A.; Scoccimarro, E.; Cavaliere, A.; Anderlini, L.; Belardinelli, M. E.; Todesco, M.

    2017-12-01

    The influence of rainfall on crustal deformation has been described at local scales, using tilt and strain meters, in several tectonic settings. However, the literature on the spatial extent of rainfall-induced deformation is still scarce. We analyzed 10 years of displacement time-series from 150 continuous GPS stations operating across the broad zone of deformation accommodating the N-S Adria-Eurasia convergence and the E-ward escape of the Eastern Alps toward the Pannonian basin. We applied a blind-source-separation algorithm based on a variational Bayesian Independent Component Analysis method to the de-trended time-series, being able to characterize the temporal and spatial features of several deformation signals. The most important ones are a common mode annual signal, with spatially uniform response in the vertical and horizontal components and a time-variable, non-cyclic, signal characterized by a spatially variable response in the horizontal components, with stations moving (up to 8 mm) in the opposite directions, reversing the sense of movement in time. This implies a succession of extensional/compressional strains, with variable amplitudes through time, oriented normal to rock fractures in karst areas. While seasonal displacements in the vertical component (with an average amplitude of 4 mm over the study area) are satisfactorily reproduced by surface hydrological loading, estimated from global assimilation models, the non seasonal signal is associated with groundwater flow in karst systems, and is mainly influencing the horizontal component. The temporal evolution of this deformation signal is correlated with cumulated precipitation values over periods of 200-300 days. This horizontal deformation can be explained by pressure changes associated with variable water levels within vertical fractures in the vadose zones of karst systems, and the water level changes required to open or close these fractures are consistent with the fluctuations of precipitation

  9. Self-potential monitoring of water flux at the HOBE agricultural site, Voulund, Denmark

    NASA Astrophysics Data System (ADS)

    Jougnot, D.; Linde, N.; Looms, M. C.

    2013-12-01

    The self-potential (SP) method is of interest in hydrology and environmental sciences because of its non-invasive nature and its sensitivity to flow and transport processes in the subsurface. The contribution to the SP signal by water flux is referred to as the streaming potential and is due to the presence of an electrical double layer at the mineral-pore water interface. When water flows through the pore, it gives rise to a streaming current and a resulting measurable electrical voltage between non-polarizable electrodes placed at different locations. This electrokinetic behavior is well understood in water saturated porous media, but the best way to model streaming currents under partial saturation is still under discussion. To better understand SP data within the vadose zone, we conducted field-based monitoring of the vertical distribution of the SP signal following different hydrologic events. The investigations were carried out at the Voulund agricultural test site that is part of the Danish hydrological observatory, HOBE, located in the Skjern river catchment (Denmark) in the middle of a cultivated area. It has been instrumented since 2010 to monitor suction, water content and temperature down to a depth of 3 m, together with meteorological variables and repeated geophysical campaigns (cross borehole electrical resistivity tomography and ground penetrating radar). In July 2011, we installed 15 non-polarizable electrodes at 10 depths within the vadose zone (from 0.25 to 3.10 m) and a reference electrode below the water table (7.30 m). More than 2 years of data acquired at a measurement period of 5 minutes are now available with periods indicative of various hydrologic events, such as natural infiltration, water table rises and a high salinity tracer test. We performed wavelet-based signal analysis and investigated the wavelet coherency of the SP data with other measurement variables. The wavelet coherency analysis displays an anti-correlation between SP and

  10. Quantifying the Influence of Near-Surface Water-Energy Budgets on Soil Thermal Properties Using a Network of Coupled Meteorological and Vadose Zone Instrument Arrays in Indiana, USA

    NASA Astrophysics Data System (ADS)

    Naylor, S.; Gustin, A. R.; Ellett, K. M.

    2012-12-01

    Weather stations that collect reliable, sustained meteorological data sets are becoming more widely distributed because of advances in both instrumentation and data server technology. However, sites collecting soil moisture and soil temperature data remain sparse with even fewer locations where complete meteorological data are collected in conjunction with soil data. Thanks to the advent of sensors that collect continuous in-situ thermal properties data for soils, we have gone a step further and incorporated thermal properties measurements as part of hydrologic instrument arrays in central and northern Indiana. The coupled approach provides insights into the variability of soil thermal conductivity and diffusivity attributable to geologic and climatological controls for various hydrogeologic settings. These data are collected to facilitate the optimization of ground-source heat pumps (GSHPs) in the glaciated Midwest by establishing publicly available data that can be used to parameterize system design models. A network of six monitoring sites was developed in Indiana. Sensors that determine thermal conductivity and diffusivity using radial differential temperature measurements around a heating wire were installed at 1.2 meters below ground surface— a typical depth for horizontal GSHP systems. Each site also includes standard meteorological sensors for calculating reference evapotranspiration following the methods by the Food and Agriculture Organization (FAO) of the United Nations. Vadose zone instrumentation includes time domain reflectometry soil-moisture and temperature sensors installed at 0.3-meter depth intervals down to a 1.8-meter depth, in addition to matric potential sensors at 0.15, 0.3, 0.6, and 1.2 meters. Cores collected at 0.3-meter intervals were analyzed in a laboratory for grain size distribution, bulk density, thermal conductivity, and thermal diffusivity. Our work includes developing methods for calibrating thermal properties sensors based on

  11. Evolution of Root Zone Storage after Land Use Change

    NASA Astrophysics Data System (ADS)

    Nijzink, R.; Hutton, C.; Capell, R.; Pechlivanidis, I.; Hrachowitz, M.; Savenije, H.

    2015-12-01

    It has been acknowledged for some time that a coupling exists between vegetation, climate and hydrological processes (e.g. Eagleson, 1982a, Rodriguez-Iturbe,2001 ). Recently, Gao et al.(2014) demonstrated that one of the core parameters of hydrological functioning, the catchment-scale root zone water storage capacity, can be estimated based on climate data alone. It was shown that ecosystems develop root zone storage capacities that allow vegetation to bridge droughts with return periods of about 20 years. As a consequence, assuming that the evaporative demand determines the root zone storage capacity, land use changes, such as deforestation, should have an effect on the development of this capacity . In this study it was tested to which extent deforestation affects root zone storage capacities. To do so, four different hydrological models were calibrated in a moving window approach after deforestation occurred. In this way, model based estimates of the storage capacity in time were obtained. This was compared with short term estimates of root zone storage capacities based on a climate based method similar to Gao et al.(2014). In addition, the equilibrium root zone storage capacity was determined with the total time series of an unaffected control catchment. Preliminary results indicate that models tend to adjust their storage capacity to the values found by the climate based method. This is strong evidence that the root zone storage is determined by the evaporative demand of vegetation. Besides, root zones storage capacities develop towards an equilibrium value where the ecosystem is in balance, further highlighting the evolving, time dynamic character of hydrological systems.

  12. Hydrology controls dissolved organic matter export and composition in an Alpine stream and its hyporheic zone.

    PubMed

    Fasching, Christina; Ulseth, Amber J; Schelker, Jakob; Steniczka, Gertraud; Battin, Tom J

    2016-03-01

    Streams and rivers transport dissolved organic matter (DOM) from the terrestrial environment to downstream ecosystems. In light of climate and global change it is crucial to understand the temporal dynamics of DOM concentration and composition, and its export fluxes from headwaters to larger downstream ecosystems. We monitored DOM concentration and composition based on a diurnal sampling design for 3 years in an Alpine headwater stream. We found hydrologic variability to control DOM composition and the coupling of DOM dynamics in the streamwater and the hyporheic zone. High-flow events increased DOM inputs from terrestrial sources (as indicated by the contributions of humic- and fulvic-like fluorescence), while summer baseflow enhanced the autochthonous imprint of DOM. Diurnal and seasonal patterns of DOM composition were likely induced by biological processes linked to temperature and photosynthetic active radiation (PAR). Floods frequently interrupted diurnal and seasonal patterns of DOM, which led to a decoupling of streamwater and hyporheic water DOM composition and delivery of aromatic and humic-like DOM to the streamwater. Accordingly, DOM export fluxes were largely of terrigenous origin as indicated by optical properties. Our study highlights the relevance of hydrologic and seasonal dynamics for the origin, composition and fluxes of DOM in an Alpine headwater stream.

  13. Biodegradation of organic compounds in vadose zone and aquifer sediments.

    PubMed Central

    Konopka, A; Turco, R

    1991-01-01

    The microbial processes that occur in the subsurface under a typical Midwest agricultural soil were studied. A 26-m bore was installed in November of 1988 at a site of the Purdue University Agronomy Research Center. Aseptic collections of soil materials were made at 17 different depths. Physical analysis indicated that the site contained up to 14 different strata. The site materials were primarily glacial tills with a high carbonate content. The N, P, and organic C contents of sediments tended to decrease with depth. Ambient water content was generally less than the water content, which corresponds to a -0.3-bar equivalent. No pesticides were detected in the samples, and degradation of added 14C-labeled pesticides (atrazine and metolachlor) was not detected in slurry incubations of up to 128 days. The sorption of atrazine and metolachlor was correlated with the clay content of the sediments. Microbial biomass (determined by direct microscopic count, viable count, and phospholipid assay) in the tills was lower than in either the surface materials or the aquifer located at 25 m. The biodegradation of glucose and phenol occurred rapidly and without a lag in samples from the aquifer capillary fringe, saturated zone, and surface soils. In contrast, lag periods and smaller biodegradation rates were found in the till samples. Subsurface sediments are rich in microbial numbers and activity. The most active strata appear to be transmissive layers in the saturated zone. This implies that the availability of water may limit activity in the profile. PMID:1768098

  14. ANNUAL REPORT FOR ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant

    2003-06-15

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zonemore » systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the coprecipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).« less

  15. Temporal Variation and Scaling of Hydrological Variables in a Typical Watershed

    NASA Astrophysics Data System (ADS)

    Yang, C.; Zhang, Y. K.; Liang, X.; Liu, J.

    2016-12-01

    Temporal variations of the main hydrological variables over 16 years were systematically investigated based on the results from an integrated hydrological modeling at the Sagehen Creek Watershed in northern Sierra Nevada. Temporal scaling of these variables and damping effects of the hydrological system as well as its subsystems, i.e., the land surface, unsaturated zone, and saturated zone, were analyzed with spectral analyses. It was found that the hydrological system may act as a cascade of hierarchical fractal filters which sequentially transfer a non-fractal or less correlated fractal hydrological signal to a more correlated fractal signal. Temporal scaling of infiltration (I), actual evapotraspiration (ET), recharge (R), baseflow (BF), streamflow (SF) exist and the temporal autocorrelation of these variables increase as water moves through the system. The degree of the damping effect of the subsystems is different and is strongest in the unsaturated zone compared with that of the land surface and saturated zone. The temporal scaling of the groundwater levels (h) also exists and is strongly affected by the river: the temporal autocorrelation of h near the river is similar to that of the river stage fluctuations and increases away from the river. There is a break in the temporal scaling of h near the river at low frequencies due to the effect of the river. Temporal variations of the soil moisture (θ) is more complicated: the value of the scaling exponent (β) for θ increases with depth as water moves downwards and its high-frequency fluctuations are damped by the unsaturated zone. The temporal fluctuations of precipitation (P) and I are fractional Gauss noise (fGn), those of ET, R, BF, and SF are fractional Brownian motion (fBm), and those of h away from the river are 2nd-order fBm based on the values of β obtained in this study. Keywords: Temporal variations, Scaling, Damping effect, Hydrological system.

  16. Hydrologic testing of tight zones in southeastern New Mexico.

    USGS Publications Warehouse

    Dennehy, K.F.; Davis, P.A.

    1981-01-01

    Increased attention is being directed toward the investigation of tight zones in relation to the storage and disposal of hazardous wastes. Shut-in tests, slug tests, and pressure-slug tests are being used at the proposed Waste Isolation Pilot Plant site, New Mexico, to evaluate the fluid-transmitting properties of several zones above the proposed repository zone. All three testing methods were used in various combinations to obtain values for the hydraulic properties of the test zones. Multiple testing on the same zone produced similar results. -from Authors

  17. Recharge zone of the Edwards aquifer hydrologically associated with Barton springs in the Austin area, Texas

    USGS Publications Warehouse

    Slagle, Diana L.; Ardis, Ann F.; Slade, Raymond M.

    1986-01-01

    The Edwards aquifer extends in a narrow belt from Bell County in the northeast to Kinney County in the southwest (index map) and provides water for at least nine counties in south-central Texas. Hydrologic boundaries divide the Edwards aquifer in the Austin area for which Barton Springs is the major discharge point. This part of the Edwards aquifer provides the municipal, industrial, domestic, and agricultural water supplies for about 30,000 people in the Austin area (southern Travis and northern Hays counties). Discharge from Barton Springs sustains streamflow at the mouth of Barton Creek and flows into Town Lake. Much of the land use within the outcrop area of the Edwards aquifer near Austin is rapidly changing from natural woodland and grassland to commercial and residential developments. Because urban development can result in a substantial degradation of the quality of water that recharges the aquifer, the extent of the recharge zone of the Edwards aquifer was delineated to provide information to the City of Austin for their use in formulating a plan for protecting and managing groundwater quality. The purpose of this report is to define and delineate the areal extent of the recharge zone of the Edwards aquifer in southern Travis and northern Hays Counties. The areal boundary of the recharge zone was determined by: (1) geologic mapping of the aquifer area; (2) interpretation of aerial photographs; (3) field verification of existing geologic maps; and (4) streamflow-loss studies. 

  18. Analysis of one year time-lapse electrical data to unravel hydrological processes acting on a clayey landslide

    NASA Astrophysics Data System (ADS)

    Gance, J.; Sailhac, P.; Malet, J.; Supper, R.; Jochum, B.; Ottowitz, D.; Grandjean, G.

    2013-12-01

    Movements of water in the topsoil (infiltration, run-off and evaporation) influence changes in slope stability which is the main controlling factor of landslide triggering (e.g. van Asch et al., 1999). Among the petrophysical parameters that can provide time-lapse sections of the topsoil, we consider the electrical conductivity for its sensitivity to soil water contents. Based on recent works which showed the possibility of monitoring the hydrological response of a clay-shale slope to a controlled rainfall experiment (Travelletti et al., 2012), we installed a permanent electrical monitoring experiment at the Super-Sauze landslide for long-term monitoring (one year) of natural meteorological events. We used the GEOMON4D resistivimeter, developed by the Austrian Geological Survey (Vienna, Austria) for experiments needing high rate of data acquisition, records of full signal samples for noise detection, remote controlled management and automatic data transfer (Supper et al., 2002, 2003 & 2004). The electrode positions varying with time, we installed two terrestrial optical cameras to characterize the changes in dipole geometry. Several hydrological sensors were installed along the profile to measure soil temperature, water temperature and conductivity, ground water level and soil humidity in the vadose zone. The main challenge is the processing of ca. 4.2 million of electrical resistivity data. In this difficult context, the potential factors influencing electrical resistivity with time without modification of soil saturation are the relative changes in the dipole geometry (linked to the displacement of the electrodes), changes in soil and water temperature, change in material porosity due to compaction/dilatation caused by the landslide movement. Therefore, before any inversion of data, we verify the presence of possible 3D effects, and assess the measurement accuracy and uncertainty. An apparent resistivity variation threshold, from which a modification of the

  19. Studying unsaturated epikarst water storage properties by time lapse surface to depth gravity measurements

    NASA Astrophysics Data System (ADS)

    Deville, S.; Champollion, C.; chery, J.; Doerflinger, E.; Le Moigne, N.; Bayer, R.; Vernant, P.

    2011-12-01

    The assessment of water storage in the unsaturated zone in karstic areas is particularly challenging. Indeed, water flow path and water storage occur in quite heterogeneous ways through small scale porosity, fractures, joints and large voids. Due to this large heterogeneity, it is therefore difficult to estimate the amount of water circulating in the vadose zone by hydrological means. One indirect method consists to measure the gravity variation associated to water storage and withdrawal. Here, we apply a gravimetric method in which the gravity is measured at the surface and at depth on different sites. Then the time variations of the surface to depth (STD) gravity differences are compared for each site. In this study we attempt to evaluate the magnitude of epikarstic water storage variation in various karst settings using a CG5 portable gravimeter. Surface to depth gravity measurements are performed two times a year since 2009 at the surface an inside caves at different depths on three karst aquifers in southern France : 1. A limestone site on the Larzac plateau with a vadose zone thickness of 300m On this site measurements are done on five locations at different depths going from 0 to 50 m; 2. A dolomitic site on the Larzac plateau (Durzon karst aquifer) with a vadose zone thickness of 200m; Measurements are taken at the surface and at 60m depth 3. A limestone site on the Hortus karst aquifer and "Larzac Septentrional karst aquifer") with a vadose zone thickness of only 35m. Measurements are taken at the surface and at 30m depth Therefore, our measurements are used in two ways : First, the STD differences between dry and wet seasons are used to estimate the capacity of differential storage of each aquifer. Surprisingly, the differential storage capacity of all the sites is relatively invariant despite their variable geological of hydrological contexts. Moreover, the STD gravity variations on site 1 show that no water storage variation occurs beneath 10m depth

  20. Monitoring CO2 Intrusion in shallow aquifer using complex electrical methods and a novel CO2 sensitive Lidar-based sensor

    NASA Astrophysics Data System (ADS)

    Leger, E.; Dafflon, B.; Thorpe, M.; Kreitinger, A.; Laura, D.; Haivala, J.; Peterson, J.; Spangler, L.; Hubbard, S. S.

    2016-12-01

    a range of geophysical, remote sensing, hydrological and geochemical measurement approaches can be optimally configured to detect the distribution and explore behavior of possible CO2 leakages in distinct compartments, including groundwater, vadose zone, and atmosphere.

  1. Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

    NASA Astrophysics Data System (ADS)

    Moffett, Kevan B.; Gorelick, Steven M.

    2016-03-01

    Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

  2. Experimental quantification of solute transport through the vadose zone under dynamic boundary conditions with dye tracers and optical methods.

    NASA Astrophysics Data System (ADS)

    Cremer, Clemens; Neuweiler, Insa

    2017-04-01

    transport through the material interface which differs between the stationary (unilateral) and dynamic cases (bilateral). This qualitative observation is confirmed by breakthrough curves for dynamic experiments which generally show the trend of faster initial breakthrough and increased tailing when compared to stationary infiltration results. Literature Cremer, C.J.M., I. Neuweiler, M. Bechtold, J. Vanderborght (2016): Solute Transport in Heterogeneous Soil with Time-Dependent Boundary Conditions, Vadose Zone Journal 15 (6) DOI: 10.2136/vzj2015.11.0144

  3. A simulation model for projecting changes in salinity concentrations and species dominance in the coastal margin habitats of the Everglades

    USGS Publications Warehouse

    Teh, S.Y.; DeAngelis, D.L.; Sternberg, L.D.S.L.; Miralles-Wilhelm, F. R.; Smith, T.J.; Koh, H. L.

    2008-01-01

    Sharp boundaries typically separate the salinity tolerant mangroves from the salinity intolerant hardwood hammock species, which occupy the similar geographical areas of southern Florida. Evidence of strong feedback between tree community-type and the salinity of the unsaturated (vadose) zone of the soil suggests that a severe disturbance that significantly tilts the salinity in the vadose zone might cause a shift from one vegetation type to the other. In this study, a model based upon the feedback dynamics between vegetation and salinity of the vadose zone of the soil was used to take account of storm surge events to investigate the mechanisms that by which this large-scale disturbance could affect the spatial pattern of hardwood hammocks and mangroves. Model simulation results indicated that a heavy storm surge that completely saturated the vadose zone at 30 ppt for 1 day could lead to a regime shift in which there is domination by mangroves of areas previously dominated by hardwood hammocks. Lighter storm surges that saturated the vadose zone at less than 7 ppt did not cause vegetation shifts. Investigations of model sensitivity analysis indicated that the thickness of the vadose zone, coupled with precipitation, influenced the residence time of high salinity in the vadose zone and therefore determined the rate of mangrove domination. The model was developed for a southern Florida coastal ecosystem, but its applicability may be much broader. ?? 2008 Elsevier B.V. All rights reserved.

  4. Soil Moisture: The Hydrologic Interface Between Surface and Ground Waters

    NASA Technical Reports Server (NTRS)

    Engman, Edwin T.

    1997-01-01

    A hypothesis is presented that many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture. The specific hydrologic processes that may be detected include groundwater recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential evapotranspiration (ET), and information about the hydrologic properties of soils. In basin and hillslope hydrology, soil moisture is the interface between surface and ground waters.

  5. Illuminating hydrological processes at the soil-vegetation-atmosphere interface with water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, Matthias; Leistert, Hannes; Gimbel, Katharina; Weiler, Markus

    2016-09-01

    Water stable isotopes (18O and 2H) are widely used as ideal tracers to track water through the soil and to separate evaporation from transpiration. Due to the technical developments in the last two decades, soil water stable isotope data have become easier to collect. Thus, the application of isotope methods in soils is growing rapidly. Studies that make use of soil water stable isotopes often have a multidisciplinary character since an interplay of processes that take place in the vadose zone has to be considered. In this review, we provide an overview of the hydrological processes that alter the soil water stable isotopic composition and present studies utilizing pore water stable isotopes. The processes that are discussed include the water input as precipitation or throughfall, the output as evaporation, transpiration, or recharge, and specific flow and transport processes. Based on the review and supported by additional data and modeling results, we pose a different view on the recently proposed two water world hypothesis. As an alternative to two distinct pools of soil water, where one pool is enriched in heavy isotopes and used by the vegetation and the other pool does not undergo isotopic fractionation and becomes recharge, the water gets successively mixed with newly introduced rainwater during the percolation process. This way, water initially isotopically enriched in the topsoil loses the fractionation signal with increasing infiltration depth, leading to unfractionated isotopic signals in the groundwater.

  6. Inverse Modeling of Hydrologic Parameters Using Surface Flux and Runoff Observations in the Community Land Model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sun, Yu; Hou, Zhangshuan; Huang, Maoyi

    2013-12-10

    This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Two inversion strategies, the deterministic least-square fitting and stochastic Markov-Chain Monte-Carlo (MCMC) - Bayesian inversion approaches, are evaluated by applying them to CLM4 at selected sites. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find thatmore » using model parameters calibrated by the least-square fitting provides little improvements in the model simulations but the sampling-based stochastic inversion approaches are consistent - as more information comes in, the predictive intervals of the calibrated parameters become narrower and the misfits between the calculated and observed responses decrease. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to the different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.« less

  7. Assessing controls on perched saturated zones beneath the Idaho Nuclear Technology and Engineering Center, Idaho

    USGS Publications Warehouse

    Mirus, Benjamin B.; Perkins, Kim S.; Nimmo, John R.

    2011-01-01

    Waste byproducts associated with operations at the Idaho Nuclear Technology and Engineering Center (INTEC) have the potential to contaminate the eastern Snake River Plain (ESRP) aquifer. Recharge to the ESRP aquifer is controlled largely by the alternating stratigraphy of fractured volcanic rocks and sedimentary interbeds within the overlying vadose zone and by the availability of water at the surface. Beneath the INTEC facilities, localized zones of saturation perched on the sedimentary interbeds are of particular concern because they may facilitate accelerated transport of contaminants. The sources and timing of natural and anthropogenic recharge to the perched zones are poorly understood. Simple approaches for quantitative characterization of this complex, variably saturated flow system are needed to assess potential scenarios for contaminant transport under alternative remediation strategies. During 2009-2011, the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, employed data analysis and numerical simulations with a recently developed model of preferential flow to evaluate the sources and quantity of recharge to the perched zones. Piezometer, tensiometer, temperature, precipitation, and stream-discharge data were analyzed, with particular focus on the possibility of contributions to the perched zones from snowmelt and flow in the neighboring Big Lost River (BLR). Analysis of the timing and magnitude of subsurface dynamics indicate that streamflow provides local recharge to the shallow, intermediate, and deep perched saturated zones within 150 m of the BLR; at greater distances from the BLR the influence of streamflow on recharge is unclear. Perched water-level dynamics in most wells analyzed are consistent with findings from previous geochemical analyses, which suggest that a combination of annual snowmelt and anthropogenic sources (for example, leaky pipes and drainage ditches) contribute to recharge of shallow and

  8. Quasi 3D modeling of water flow in vadose zone and groundwater

    USDA-ARS?s Scientific Manuscript database

    The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One habitual simplification is based on the assumption that lateral flow and transport in unsaturated zone are not significant unless the capillary fringe is involved. In ...

  9. Trace Metals in Groundwater and Vadose Zone Calcite: In Situ Containment and Stabilization of Stronthium-90 and Other Divalent Metals and Radionuclides at Arid Western DOE Sites: Final Report for Award Number DE-FG07-02ER63486 to the University of Idaho (RW Smith) Environmental Management Science Program Project Number 87016

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, Robert W.; Fujita, Yoshiko

    2007-11-07

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) energy research and weapons complex. In situ containment and stabilization of these contaminants represents a cost-effective treatment strategy that minimizes workers’ exposure to hazardous substances, does not require removal or transport of contaminants, and generally does not generate a secondary waste stream. We have investigated an in situ bioremediation approach that immobilizes radionuclides or contaminant metals (e.g., strontium-90) by their microbially facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Calcite, a common mineral in many aquifers and vadosemore » zones in the arid west, can incorporate divalent metals such as strontium, cadmium, lead, and cobalt into its crystal structure by the formation of a solid solution. Collaborative research undertaken by the Idaho National Laboratory (INL), University of Idaho, and University of Toronto as part of this Environmental Management Science Program project has focused on in situ microbially-catalyzed urea hydrolysis, which results in an increase in pH, carbonate alkalinity, ammonium, calcite precipitation, and co-precipitation of divalent cations. In calcite-saturated aquifers, microbially facilitated co-precipitation with calcium carbonate represents a potential long-term contaminant sequestration mechanism. Key results of the project include: **Demonstrating the linkage between urea hydrolysis and calcite precipitation in field and laboratory experiments **Observing strontium incorporation into calcite precipitate by urea hydrolyzers with higher distribution coefficient than in abiotic **Developing and applying molecular methods for characterizing microbial urease activity in groundwater including a quantitative PCR method for enumerating ureolytic bacteria **Applying the suite of developed molecular methods to assess the

  10. Uranium plume persistence impacted by hydrologic and geochemical heterogeneity in the groundwater and river water interaction zone of Hanford site

    NASA Astrophysics Data System (ADS)

    Chen, X.; Zachara, J. M.; Vermeul, V. R.; Freshley, M.; Hammond, G. E.

    2015-12-01

    The behavior of a persistent uranium plume in an extended groundwater- river water (GW-SW) interaction zone at the DOE Hanford site is dominantly controlled by river stage fluctuations in the adjacent Columbia River. The plume behavior is further complicated by substantial heterogeneity in physical and geochemical properties of the host aquifer sediments. Multi-scale field and laboratory experiments and reactive transport modeling were integrated to understand the complex plume behavior influenced by highly variable hydrologic and geochemical conditions in time and space. In this presentation we (1) describe multiple data sets from field-scale uranium adsorption and desorption experiments performed at our experimental well-field, (2) develop a reactive transport model that incorporates hydrologic and geochemical heterogeneities characterized from multi-scale and multi-type datasets and a surface complexation reaction network based on laboratory studies, and (3) compare the modeling and observation results to provide insights on how to refine the conceptual model and reduce prediction uncertainties. The experimental results revealed significant spatial variability in uranium adsorption/desorption behavior, while modeling demonstrated that ambient hydrologic and geochemical conditions and heterogeneities in sediment physical and chemical properties both contributed to complex plume behavior and its persistence. Our analysis provides important insights into the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by surface water and groundwater interactions.

  11. Critical Zone structure inferred from multiscale near surface geophysical and hydrological data across hillslopes at the Eel River CZO

    NASA Astrophysics Data System (ADS)

    Lee, S. S.; Rempe, D. M.; Holbrook, W. S.; Schmidt, L.; Hahm, W. J.; Dietrich, W. E.

    2017-12-01

    Except for boreholes and road cut, landslide, and quarry exposures, the subsurface structure of the critical zone (CZ) of weathered bedrock is relatively invisible and unmapped, yet this structure controls the short and long term fluxes of water and solutes. Non-invasive geophysical methods such as seismic refraction are widely applied to image the structure of the CZ at the hillslope scale. However, interpretations of such data are often limited due to heterogeneity and anisotropy contributed from fracturing, moisture content, and mineralogy on the seismic signal. We develop a quantitative framework for using seismic refraction tomography from intersecting geophysical surveys and hydrologic data obtained at the Eel River Critical Zone Observatory (ERCZO) in Northern California to help quantify the nature of subsurface structure across multiple hillslopes of varying topography in the area. To enhance our understanding of modeled velocity gradients and boundaries in relation to lithological properties, we compare refraction tomography results with borehole logs of nuclear magnetic resonance (NMR), gamma and neutron density, standard penetration testing, and observation drilling logs. We also incorporate laboratory scale rock characterization including mineralogical and elemental analyses as well as porosity and density measurements made via pycnometry, helium and mercury porosimetry, and laboratory scale NMR. We evaluate the sensitivity of seismically inferred saprolite-weathered bedrock and weathered-unweathered bedrock boundaries to various velocity and inversion parameters in relation with other macro scale processes such as gravitational and tectonic forces in influencing weathered bedrock velocities. Together, our sensitivity analyses and multi-method data comparison provide insight into the interpretation of seismic refraction tomography for the quantification of CZ structure and hydrologic dynamics.

  12. Comparing Flow Mechanism Hypothesis with Mobility Data of Natural Tracers

    NASA Astrophysics Data System (ADS)

    Sanda, M.; Chárová, Z.; Zumr, D.; Císlerová, M.

    2009-04-01

    Hillslope rainfall-outflow interactions, groundwater fluxes and hydrological balance have been examined in the small mountainous headwater catchment Uhlířská (1.78 km2), Jizera Mountains, Czech Republic. The hillslope soil profile is formed by paleozolic crystalline bedrock overlaid by shallow highly permeable Cambisol, whereas the thick saturated glacial deposits in the valley are overlaid by Histosols. Quick communication of the vadose zone with the granite bedrock via preferential subsurface flowpaths is hypothesized, in agreement with the observation of instant water transformation through the permeable Cambisols, to outflow caused by storms. There is regularly a quick response of high magnitude, although surface runoff occurs very rarely. Standard climatic and hydrological monitoring is supplemented by measurements of the soil moisture, soil pore water suction, hillslope stormflow in the vadose zone and water table fluctuation in the saturated subsurface. Water sampling for analysis of the isotopes 18O and 2H and geochemical tracer silica in the form of SiO2 is performed throughout the catchment. The episode based isotopic data serve for the separation of the particular components of the outflow hydrograph and for the determination of the contribution of event and pre-event water in the hypodermic hillslope outflow and in the catchment outflow as a whole. Variation of silica content in the water cycle components was examined to assess contributions from the soil profile and the aquifer. Significant portion of event catchment runoff was assigned to pre-event water, partly stored in the shallow soil layers on hillslopes and partly in the valley aquifer. Here, a significant mixing (in form of attenuation of the input signal of 18O or 2H measured for precipitation) occurs as proven by sampling and modeling by means of physically based models for vadose and saturated zones. Hydrological balance of the catchment shows only minor discrepancies in averaged value

  13. “Groundwater hydrology” is redundant

    NASA Astrophysics Data System (ADS)

    While in the Netherlands a few months ago, I mentioned “groundwater hydrology” to a very well-educated, very literary, and non-hydrologic old friend. She shuddered and told me in no uncertain words that this was a horrible term, completely redundant like a round circle, or as the linguists call it, a pleonasm. This is, of course, because hydrology already means water science (from the Greek words udor, or hydor for water, and logos for science), so that groundwater hydrology really stands for groundwater water science, and surface water hydrology for surface water science.These are pleonasms of the first kind and insults to any language purist, which all of us should strive to be! So I propose that henceforth groundwater hydrology be called subterranean hydrology. Other possibilities would be subsurface hydrology, but this sounds too shallow, or underground hydrology, which, however, could give the impression of some clandestine activity. Besides, subterranean hydrology would be in keeping with the words for groundwater in Latin-based languages (eau souterrain in French, acqua sotierranea in Italian, and aguas subterraneas in Spanish). Also, subterranean hydrology includes the vadose zone, which, of course, groundwater hydrology as such does not. Surface water hydrology would simply be called surface hydrology, and anything above that atmospheric hydrology.

  14. Self-potential method for characterizing streaming flows in the saturated and vadose zones: state of the art and limitations

    NASA Astrophysics Data System (ADS)

    Sailhac, P.

    2005-12-01

    Self-Potential (SP) method is sensitive not only to the water content, but, above all, to flow velocities within the underground porous medium. So it can be considered as a crucial help in hydrogeophysics. This is underlined by the so-called electrokinetic coupling and has been early used in geophysics (e.g. Bogoslovsky and Ogilvy, 1970) and hydrology (Abaza and Clyde 1969). During the last decade, both experimental and theoretical progresses have moved ahead SP to provide quantitative flow parameters. Now SP time and/or spatial variations can be used to monitor water fluxes during infiltration (e.g. Thony et al. 1997, Doussan et al. 2002, Darnet & Marquis 2004), seepage (Titov et al. 2000), or pumping (e.g. Fagerlund & Heinson 2003, Darnet et al. 2003, Revil et al. 2003). In order that SP is used by a larger community, it would be useful to recall the fundamentals, to review recent interpretation techniques in a simple framework and to precise their limitations. First considering flows in the saturated zone and a pumping experiment, I will show different interpretation techniques that are based upon Green function decompositions (e.g. wavelets, COP tomography of Patella, and iso-α line of Revil et al.). Classical application of theses techniques is underlined by the assumption of a constant electrical conductivity medium that involves uncertainty and bias in quantitative flow parameter estimates. For instance, the diffusive effect of a conductive shallow layer tends to increase the apparent depth of an underground flow source or sink. To correct this problem, one can use Green functions of a tabular medium in the COP tomography. In the complex case of unsaturated zone, the hydraulic and electric conductivities are depending on the water content. We will discuss on different soil models and different experiments that can be used for the monitoring of the infiltration and the characterisation of the soil hydraulic parameters.

  15. Characterization of Vadose Zone Sediment: RCRA Borehole 299-E33-338 Located Near the B-BX-BY Waste Management Area

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lindenmeier, Clark W.; Serne, R. Jeffrey; Bjornstad, Bruce N.

    2003-09-11

    This report summarizes data collected from samples in borehole 299-E33-338 (C3391). Borehole 299-E33-338 was drilled for two purposes. One purpose was for installation of a RCRA ground-water monitoring well and the other was to characterize the in situ soils and background porewater chemistry near WMA B-BX-BY that have been largely uncontaminated by tank farm and crib and trench discharge operations. This borehole was drilled just outside the southeast fence line of the B tank farm. The borehole was drilled between July 23 and August 8, 2001 to a total depth of 80.05 m (275.75 ft) bgs using the cable-tool methodmore » (Horton 2002). The water table was contacted at 77.5 m (254.2 ft) bgs and the top of basalt at 82.6 m (271 ft) bgs. Samples to the top of basalt were collected via a drive barrel/splitspoon, before switching to a hard tool to drill 5 feet into the basalt. Nearly continuous core was obtained down to a depth of ~78.6 m (258 ft) bgs. Two hundred and two 2-ft long by 4-in diameter cores were retrieved, which accounts for ~75% the total length of the borehole. Each 2-ft splitspoon contained two 1-ft lexan-lined core segments. The lithology of this borehole was summarized onto a field geologist's log by a CH2M HILL Hanford Group, Inc. geologist (L. D. Walker); subsequently visual inspection of the cores was performed in the laboratory by K. A. Lindsey (Kennedy/Jenks), K. D. Reynolds (Duratek), and B. N. Bjornstad (Pacific Northwest National Laboratory), who also collected 24 samples for paleomagnetic analysis. Subsamples were taken from all 102 cores for moisture content (Table B.1). In addition, 21 core subsamples were collected from a depth of geological interest for mineralogical and geochemical analysis. Data from these samples allow for comparison of uncontaminated versus contaminated soils to better understand the contributions of tank wastes and other wastewaters on the vadose zone in and around WMA B-BX-BY.« less

  16. Linking major and trace element headwater stream concentrations to DOC release and hydrologic conditions in a bog and peaty riparian zone

    NASA Astrophysics Data System (ADS)

    Broder, Tanja; Biester, Harald

    2017-04-01

    Peatlands and organic-rich riparian zones are known to export large amounts of dissolved organic carbon (DOC) to surface water. In organic-rich, acidic headwater streams main carriers for element export are dissolved organic matter (DOM) and organic-iron complexes. In this environment DOM might also act as major carrier for metals, which otherwise may have a low solubility. This study examines annual and short term event-based variations of major and trace elements in a headwater catchment. Patterns are used to trace hydrological pathways and element sources under different hydrologic preconditions. Furthermore, it elucidates the importance of DOC as carrier of different elements in a bog and a peaty riparian catchment. The study was conducted in a small headwater stream draining an ombrotrophic peatland with an adjacent forested area with peaty riparian soils in the Harz Mountains (Germany). Discharge sampling was conducted weekly at two sites from snowmelt to begin of snowfall and in high resolution during selected discharge events in 2013 and 2014. Element concentrations were measured by means of ICP-MS and ICP-OES. A PCA was performed for each site and for annual and event datasets. Results show that a large number of element concentrations strongly correlate with DOC concentrations at the bog site. Even elements like Ca and Mg, which are known to have a low affinity to DOC. Congruently, the first principal component integrates the DOC pattern (element loadings > 0.8: Ca, Fe, Mg, Mn, Zn, As, Sr, Cd, DOC) and explained about 35 % of total variance and even 50 % during rain events (loadings > 0.8: Al, Ca, Fe, Mg, Mn, Zn, Li, Co, As, Sr, Cd, Pb, DOC). The study cannot verify that all correlating elements bind to DOC. It is likely that also a common mobilization pattern in the upper peat layer by plant decomposition causes the same response to changes in hydrologic pathways. Additionally, a low mineral content and an enrichment of elements like Fe and Mn in the

  17. Susceptibility to enhanced chemical migration from depression-focused preferential flow, High Plains aquifer

    USGS Publications Warehouse

    Gurdak, Jason J.; Walvoord, Michelle Ann; McMahon, Peter B.

    2008-01-01

    Aquifer susceptibility to contamination is controlled in part by the inherent hydrogeologic properties of the vadose zone, which includes preferential-flow pathways. The purpose of this study was to investigate the importance of seasonal ponding near leaky irrigation wells as a mechanism for depression-focused preferential flow and enhanced chemical migration through the vadose zone of the High Plains aquifer. Such a mechanism may help explain the widespread presence of agrichemicals in recently recharged groundwater despite estimates of advective chemical transit times through the vadose zone from diffuse recharge that exceed the historical period of agriculture. Using a combination of field observations, vadose zone flow and transport simulations, and probabilistic neural network modeling, we demonstrated that vadose zone transit times near irrigation wells range from 7 to 50 yr, which are one to two orders of magnitude faster than previous estimates based on diffuse recharge. These findings support the concept of fast and slow transport zones and help to explain the previous discordant findings of long vadose zone transit times and the presence of agrichemicals at the water table. Using predictions of aquifer susceptibility from probabilistic neural network models, we delineated approximately 20% of the areal extent of the aquifer to have conditions that may promote advective chemical transit times to the water table of <50 yr if seasonal ponding and depression-focused flow exist. This aquifer-susceptibility map may help managers prioritize areas for groundwater monitoring or implementation of best management practices.

  18. Using chemical, hydrologic, and age dating analysis to delineate redox processes and flow paths in the riparian zone of a glacial outwash aquifer‐stream system

    USGS Publications Warehouse

    Puckett, Larry J.; Cowdery, Timothy K.; McMahon, Peter B.; Tornes, Lan H.; Stoner, Jeffrey D.

    2002-01-01

    A combination of chemical and dissolved gas analyses, chlorofluorocarbon age dating, and hydrologic measurements were used to determine the degree to which biogeochemical processes in a riparian wetland were responsible for removing NO3−from groundwaters discharging to the Otter Tail River in west central Minnesota. An analysis of river chemistry and flow data revealed that NO3− concentrations in the river increased in the lower half of the 8.3 km study reach as the result of groundwater discharge to the river. Groundwater head measurements along a study transect through the riparian wetland revealed a zone of groundwater discharge extending out under the river. On the basis of combined chemical, dissolved gas, age date, and hydrologic results, it was determined that water chemistry under the riparian wetland was controlled largely by upgradient groundwaters that followed flow paths up to 16 m deep and discharged under the wetland, creating a pattern of progressively older, more chemically reduced, low NO3− water the farther one progressed from the edge of the wetland toward the river. These findings pose challenges for researchers investigating biogeochemical processes in riparian buffer zones because the progressively older groundwaters entered the aquifer in earlier years when less NO3− fertilizer was being used. NO3− concentrations originally present in the groundwater had also decreased in the upgradient aquifer as a result of denitrification and progressively stronger reducing conditions there. The resulting pattern of decreasing NO3− concentrations across the riparian zone may be incorrectly interpreted as evidence of denitrification losses there instead of in the upgradient aquifer. Consequently, it is important to understand the hydrogeologic setting and age structure of the groundwaters being sampled in order to avoid misinterpreting biogeochemical processes in riparian zones.

  19. Effect of water table dynamics on land surface hydrologic memory

    NASA Astrophysics Data System (ADS)

    Lo, Min-Hui; Famiglietti, James S.

    2010-11-01

    The representation of groundwater dynamics in land surface models has received considerable attention in recent years. Most studies have found that soil moisture increases after adding a groundwater component because of the additional supply of water to the root zone. However, the effect of groundwater on land surface hydrologic memory (persistence) has not been explored thoroughly. In this study we investigate the effect of water table dynamics on National Center for Atmospheric Research Community Land Model hydrologic simulations in terms of land surface hydrologic memory. Unlike soil water or evapotranspiration, results show that land surface hydrologic memory does not always increase after adding a groundwater component. In regions where the water table level is intermediate, land surface hydrologic memory can even decrease, which occurs when soil moisture and capillary rise from groundwater are not in phase with each other. Further, we explore the hypothesis that in addition to atmospheric forcing, groundwater variations may also play an important role in affecting land surface hydrologic memory. Analyses show that feedbacks of groundwater on land surface hydrologic memory can be positive, negative, or neutral, depending on water table dynamics. In regions where the water table is shallow, the damping process of soil moisture variations by groundwater is not significant, and soil moisture variations are mostly controlled by random noise from atmospheric forcing. In contrast, in regions where the water table is very deep, capillary fluxes from groundwater are small, having limited potential to affect soil moisture variations. Therefore, a positive feedback of groundwater to land surface hydrologic memory is observed in a transition zone between deep and shallow water tables, where capillary fluxes act as a buffer by reducing high-frequency soil moisture variations resulting in longer land surface hydrologic memory.

  20. The Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFC Focused on Hanford’s 300 Area Uranium Plume Quality Assurance Project Plan

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fix, N. J.

    The purpose of the project is to conduct research at an Integrated Field-Scale Research Challenge Site in the Hanford Site 300 Area, CERCLA OU 300-FF-5 (Figure 1), to investigate multi-scale mass transfer processes associated with a subsurface uranium plume impacting both the vadose zone and groundwater. The project will investigate a series of science questions posed for research related to the effect of spatial heterogeneities, the importance of scale, coupled interactions between biogeochemical, hydrologic, and mass transfer processes, and measurements/approaches needed to characterize a mass-transfer dominated system. The research will be conducted by evaluating three (3) different hypotheses focused onmore » multi-scale mass transfer processes in the vadose zone and groundwater, their influence on field-scale U(VI) biogeochemistry and transport, and their implications to natural systems and remediation. The project also includes goals to 1) provide relevant materials and field experimental opportunities for other ERSD researchers and 2) generate a lasting, accessible, and high-quality field experimental database that can be used by the scientific community for testing and validation of new conceptual and numerical models of subsurface reactive transport.« less

  1. Modeling impact of small Kansas landfills on underlying aquifers

    USGS Publications Warehouse

    Sophocleous, M.; Stadnyk, N.G.; Stotts, M.

    1996-01-01

    Small landfills are exempt from compliance with Resource Conservation and Recovery Act Subtitle D standards for liner and leachate collection. We investigate the ramifications of this exemption under western Kansas semiarid environments and explore the conditions under which naturally occurring geologic settings provide sufficient protection against ground-water contamination. The methodology we employed was to run water budget simulations using the Hydrologic Evaluation of Landfill Performance (HELP) model, and fate and transport simulations using the Multimedia Exposure Assessment Model (MULTIMED) for several western Kansas small landfill scenarios in combination with extensive sensitivity analyses. We demonstrate that requiring landfill cover, leachate collection system (LCS), and compacted soil liner will reduce leachate production by 56%, whereas requiring only a cover without LCS and liner will reduce leachate by half as much. The most vulnerable small landfills are shown to be the ones with no vegetative cover underlain by both a relatively thin vadose zone and aquifer and which overlie an aquifer characterized by cool temperatures and low hydraulic gradients. The aquifer-related physical and chemical parameters proved to be more important than vadose zone and biodegradation parameters in controlling leachate concentrations at the point of compliance. ??ASCE.

  2. Influence of multi-scale hydrologic controls on river network connectivity and riparian function

    EPA Science Inventory

    The ecological functions of rivers and streams and their associated riparian zones are strongly influenced by surface and subsurface hydrologic routing of water within river basins and river networks. Hydrologic attributes of the riparian area for a given stream reach are typica...

  3. Mixing-dependent Reactions in the Hyporheic Zone: Laboratory and Numerical Experiments

    NASA Astrophysics Data System (ADS)

    Santizo, K. Y.; Eastes, L. A.; Hester, E. T.; Widdowson, M.

    2017-12-01

    The hyporheic zone is the surface water-groundwater interface surrounding the river's perimeter. Prior research demonstrates the ability of the hyporheic zone to attenuate pollutants when surface water cycles through reactive sediments (non-mixing-dependent reactions). However, the colocation of both surface and ground water within hyporheic sediments also allows mixing-dependent reactions that require mixing of reactants from these two water sources. Recent modeling studies show these mixing zones can be small under steady state homogeneous conditions, but do not validate those results in the laboratory or explore the range of hydrological characteristics that control the extent of mixing. Our objective was to simulate the mixing zone, quantify its thickness, and probe its hydrological controls using a "mix" of laboratory and numerical experiments. For the lab experiments, a hyporheic zone was simulated in a sand mesocosm, and a mixing-dependent abiotic reaction of sodium sulfite and dissolved oxygen was induced. Oxygen concentration response and oxygen consumption were visualized via planar optodes. Sulfate production by the mixing-dependent reaction was measured by fluid samples and a spectrophometer. Key hydrologic controls varied in the mesocosm included head gradient driving hyporheic exchange and hydraulic conductivity/heterogeneity. Results show a clear mixing area, sulfate production, and oxygen gradient. Mixing zone length (hyporheic flow cell size) and thickness both increase with the driving head gradient. For the numerical experiments, transient surface water boundary conditions were implemented together with heterogeneity of hydraulic conductivity. Results indicate that both fluctuating boundary conditions and heterogeneity increase mixing-dependent reaction. The hyporheic zone is deemed an attenuation hotspot by multiple studies, but here we demonstrate its potential for mixing-dependent reactions and the influence of important hydrological

  4. Characterization of return flow pathways during flood irrigation

    NASA Astrophysics Data System (ADS)

    Claes, N.; Paige, G. B.; Parsekian, A.; Gordon, B. L.; Miller, S. N.

    2015-12-01

    With a decline in water resources available for private consumption and irrigation, the importance of sustainable water management practices is increasing. Local management decisions, based on models may affect the availability of water both locally and downstream, causing a ripple effect. It is therefore important that the models that these local management decisions are based on, accurately quantify local hydrological processes and the timescales at which they happen. We are focusing on return flow from flood irrigation, which can occur via different pathways back to the streams: overland flow, near-surface return flow and return flow via pathways below the vadose zone. The question addressed is how these different pathways each contribute to the total amount of return flow and the dynamics behind them. We used time-lapse ERT measurements in combination with an ensemble of ERT and seismic lines to answer this question via (1) capturing the process of gradual fragmentation of aqueous environments in the vadose zone during drying stages at field scale; (2) characterization of the formation of preferential flow paths from infiltrating wetting fronts during wetting cycles at field scale. The time-lapse ERT provides the possibility to capture the dynamic processes involved during the occurrence of finger flow or macro-pores when an intensive wetting period during flood irrigation occurs. It elucidates the dynamics of retention in the vadose zone during drying and wetting periods at field scale. This method provides thereby a link to upscale from laboratory experiments to field scale and watershed scale for finger flow and preferential flow paths and illustrates the hysteresis behavior at field scale.

  5. Potential for Remotely Sensed Soil Moisture Data in Hydrologic Modeling

    NASA Technical Reports Server (NTRS)

    Engman, Edwin T.

    1997-01-01

    Many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture and portray the spatial heterogeneity of hydrologic processes and properties that one encounters in drainage basins. The hydrologic processes that may be detected include ground water recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential ET, and information about the hydrologic properties of soils and heterogeneity of hydrologic parameters. Microwave remote sensing has the potential to detect these signatures within a basin in the form of volumetric soil moisture measurements in the top few cm. These signatures should provide information on how and where to apply soil physical parameters in distributed and lumped parameter models and how to subdivide drainage basins into hydrologically similar sub-basins.

  6. Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees.

    PubMed

    Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

    2014-05-01

    Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Water shifts due to climatic fluctuations between floodplain storage reservoirsAnthropogenic changes to hydrology directly impact water available to treesEcohydrologic approaches to integration of hydrology afford new possibilities.

  7. Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees

    PubMed Central

    Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

    2014-01-01

    Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Key Points Water shifts due to climatic fluctuations between floodplain storage reservoirs Anthropogenic changes to hydrology directly impact water available to trees Ecohydrologic approaches to integration of hydrology afford new

  8. Predicting changes in hydrologic retention in an evolving semi-arid alluvial stream

    USGS Publications Warehouse

    Harvey, J.W.; Conklin, M.H.; Koelsch, R.S.

    2003-01-01

    Hydrologic retention of solutes in hyporheic zones or other slowly moving waters of natural channels is thought to be a significant control on biogeochemical cycling and ecology of streams. To learn more about factors affecting hydrologic retention, we repeated stream-tracer injections for 5 years in a semi-arid alluvial stream (Pinal Creek, Ariz.) during a period when streamflow was decreasing, channel width increasing, and coverage of aquatic macrophytes expanding. Average stream velocity at Pinal Creek decreased from 0.8 to 0.2 m/s, average stream depth decreased from 0.09 to 0.04 m, and average channel width expanded from 3 to 13 m. Modeling of tracer experiments indicated that the hydrologic retention factor (Rh), a measure of the average time that solute spends in storage per unit length of downstream transport, increased from 0.02 to 8 s/m. At the same time the ratio of cross-sectional area of storage zones to main channel cross-sectional area (As/A) increased from 0.2 to 0.8 m2/m2, and average water residence time in storage zones (ts) increased from 5 to 24 min. Compared with published data from four other streams in the US, Pinal Creek experienced the greatest change in hydrologic retention for a given change in streamflow. The other streams differed from Pinal Creek in that they experienced a change in streamflow between tracer experiments without substantial geomorphic or vegetative adjustments. As a result, a regression of hydrologic retention on streamflow developed for the other streams underpredicted the measured increases in hydrologic retention at Pinal Creek. The increase in hydrologic retention at Pinal Creek was more accurately predicted when measurements of the Darcy-Weisbach friction factor were used (either alone or in addition to streamflow) as a predictor variable. We conclude that relatively simple measurements of channel friction are useful for predicting the response of hydrologic retention in streams to major adjustments in channel

  9. Hydrologic control on redox and nitrogen dynamics in a peatland soil.

    PubMed

    Rubol, Simonetta; Silver, Whendee L; Bellin, Alberto

    2012-08-15

    Soils are a dominant source of nitrous oxide (N(2)O), a potent greenhouse gas. However, the complexity of the drivers of N(2)O production and emissions has hindered our ability to predict the magnitude and spatial dynamics of N(2)O fluxes. Soil moisture can be considered a key driver because it influences oxygen (O(2)) supply, which feeds back on N(2)O sources (nitrification versus denitrification) and sinks (reduction to dinitrogen). Soil water content is directly linked to O(2) and redox potential, which regulate microbial metabolism and chemical transformations in the environment. Despite its importance, only a few laboratory studies have addressed the effects of hydrological transient dynamics on nitrogen (N) cycling in the vadose zone. To further investigate these aspects, we performed a long term experiment in a 1.5 m depth soil column supplemented by chamber experiments. With this experiment, we aimed to investigate how soil moisture dynamics influence redox sensitive N cycling in a peatland soil. As expected, increased soil moisture lowered O(2) concentrations and redox potential in the soil. The decline was more severe for prolonged saturated conditions than for short events and at deep than at the soil surface. Gaseous and dissolved N(2)O, dissolved nitrate (NO(3)(-)) and ammonium (NH(4)(+)) changed considerably along the soil column profile following trends in soil O(2) and redox potential. Hot spots of N(2)O concentrations corresponded to high variability in soil O(2) in the upper and lower parts of the column. Results from chamber experiments confirmed high NO(3)(-) reduction potential in soils, particularly from the bottom of the column. Under our experimental conditions, we identified a close coupling of soil O(2) and N(2)O dynamics, both of which lagged behind soil moisture changes. These results highlight the relationship among soil hydrologic properties, redox potential and N cycling, and suggest that models working at a daily scale need to

  10. Spatial and temporal variability of nitrate and nitrous oxide concentrations in the unsaturated zone at a corn field in the US Midwest

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, G.; Negri, C.

    2011-12-01

    There has been a significant increase in reactive nitrogen in the environment as a result of human activity. Reactive nitrogen of anthropogenic origin now equals that derived from natural terrestrial nitrogen fixation and is expected to exceed it by the end of the decade. Nitrogen is applied to crops as fertilizer and impacts the environment through water quality impairments (mostly as nitrate) and as greenhouse gas emissions (as nitrous oxide). Research on environmental impacts resulting from nitrogen application in the form of fertilizers has focused disproportionately on the degradation of water quality from agricultural non-point sources. The impacts of this degradation are registered both locally, with runoff and percolation of agrochemicals into local surface water and groundwater, and on a larger scale, such as the increase in the anoxic zone in the Gulf of Mexico attributed to nitrate from the Mississippi River. Impacts to the global climate from increased production of nitrous oxide as a result of increased fertilization are equally significant. Nitrous oxide is a greenhouse gas with a warming potential that is approximately 300 times greater than carbon dioxide. Direct emissions of nitrous oxide from the soil have been expressed as 1% of the applied nitrogen. Indirect emissions due to runoff, leaching and volatilization of the nitrogen from the field have been expressed as 0.75% of the applied nitrogen. Many studies have focused on processes governing nitrogen fluxes in the soil, surface water and groundwater systems. However, research on the biogeochemical processes regulating nitrogen fluxes in the unsaturated zone and consequent impacts on nitrate and nitrous oxide concentrations in groundwater are lacking. Our study explores the spatial and temporal variability of nitrate and nitrous oxide concentrations in the vadose zone at a 15 acre corn field in the US Midwest and links it to the concentrations found in the groundwater at the field site. Results

  11. Application of SIR-C SAR to Hydrology

    NASA Technical Reports Server (NTRS)

    Engman, Edwin T.; ONeill, Peggy; Wood, Eric; Pauwels, Valentine; Hsu, Ann; Jackson, Tom; Shi, J. C.; Prietzsch, Corinna

    1996-01-01

    The progress, results and future plans regarding the following objectives are presented: (1) Determine and compare soil moisture patterns within one or more humid watersheds using SAR data, ground-based measurements, and hydrologic modeling; (2) Use radar data to characterize the hydrologic regime within a catchment and to identify the runoff producing characteristics of humid zone watersheds; and (3) Use radar data as the basis for scaling up from small scale, near-point process models to larger scale water balance models necessary to define and quantify the land phase of GCM's (Global Circulation Models).

  12. Vadose zone isobaric well

    DOEpatents

    Hubbell, Joel M.; Sisson, James B.

    2001-01-01

    A deep tensiometer is configured with an outer guide tube having a vented interval along a perforate section at its lower end, which is isolated from atmospheric pressure at or above grade. A transducer having a monitoring port and a reference port is located within a coaxial inner guide tube. The reference port of the transducer is open to the vented interval of the outer guide tube, which has the same gas pressure as in the sediment surrounding the tensiometer. The reference side of the pressure transducer is thus isolated from the effects of atmospheric pressure changes and relative to pressure changes in the material surrounding the tensiometer measurement location and so it is automatically compensated for such pressure changes.

  13. T Tank Farm Interim Surface Barrier Demonstration - Vadose Zone Monitoring FY09 Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Z. F.; Strickland, Christopher E.; Field, Jim G.

    2010-01-01

    DOE’s Office of River Protection constructed a temporary surface barrier over a portion of the T Tank Farm as part of the T Farm Interim Surface Barrier Demonstration Project. As part of the demonstration effort, vadose zone moisture is being monitored to assess the effectiveness of the barrier at reducing soil moisture. A solar-powered system was installed to continuously monitor soil water conditions at four locations (i.e., instrument Nests A, B, C, and D) beneath the barrier and outside the barrier footprint as well as site meteorological conditions. Nest A is placed in the area outside the barrier footprint andmore » serves as a control, providing subsurface conditions outside the influence of the surface barrier. Nest B provides subsurface measurements to assess surface-barrier edge effects. Nests C and D are used to assess changes in soil-moisture conditions beneath the interim surface barrier. Each instrument nest is composed of a capacitance probe (CP) with multiple sensors, multiple heat-dissipation units (HDUs), and a neutron probe (NP) access tube. The monitoring results in FY09 are summarized below. The solar panels functioned normally and could provide sufficient power to the instruments. The CP in Nest C after September 20, 2009, was not functional. The CP sensors in Nest B after July 13 and the 0.9-m CP sensor in Nest D before June 10 gave noisy data. Other CPs were functional normally. All the HDUs were functional normally but some pressure-head values measured by HDUs were greater than the upper measurement-limit. The higher-than-upper-limit values might be due to the very wet soil condition and/or measurement error but do not imply the malfunction of the sensors. Similar to FY07 and FY08, in FY09, the soil under natural conditions (Nest A) was generally recharged during the winter period (October-March) and discharged during the summer period (April-September). Soil water conditions above about 1.5-m to 2-m depth from all three types of

  14. Two decision-support tools for assessing the potential effects of energy development on hydrologic resources as part of the Energy and Environment in the Rocky Mountain Area interactive energy atlas

    USGS Publications Warehouse

    Linard, Joshua I.; Matherne, Anne Marie; Leib, Kenneth J.; Carr, Natasha B.; Diffendorfer, James E.; Hawkins, Sarah J.; Latysh, Natalie; Ignizio, Drew A.; Babel, Nils C.

    2014-01-01

    The U.S. Geological Survey project—Energy and Environment in the Rocky Mountain Area (EERMA)—has developed a set of virtual tools in the form of an online interactive energy atlas for Colorado and New Mexico to facilitate access to geospatial data related to energy resources, energy infrastructure, and natural resources that may be affected by energy development. The interactive energy atlas currently (2014) consists of three components: (1) a series of interactive maps; (2) downloadable geospatial datasets; and (3) decison-support tools, including two maps related to hydrologic resources discussed in this report. The hydrologic-resource maps can be used to examine the potential effects of energy development on hydrologic resources with respect to (1) groundwater vulnerability, by using the depth to water, recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity of the aquifer (DRASTIC) model, and (2) landscape erosion potential, by using the revised universal soil loss equation (RUSLE). The DRASTIC aquifer vulnerability index value for the two-State area ranges from 48 to 199. Higher values, indicating greater relative aquifer vulnerability, are centered in south-central Colorado, areas in southeastern New Mexico, and along riparian corridors in both States—all areas where the water table is relatively close to the land surface and the aquifer is more susceptible to surface influences. As calculated by the RUSLE model, potential mean annual erosion, as soil loss in units of tons per acre per year, ranges from 0 to 12,576 over the two-State area. The RUSLE model calculated low erosion potential over most of Colorado and New Mexico, with predictions of highest erosion potential largely confined to areas of mountains or escarpments. An example is presented of how a fully interactive RUSLE model could be further used as a decision-support tool to evaluate the potential hydrologic effects of energy development on a

  15. Ecohydrological Consequences of Critical Zone Structure in the Franciscan Formation, Northern California Coast Ranges

    NASA Astrophysics Data System (ADS)

    Hahm, W. J.; Dietrich, W. E.; Dawson, T. E.; Lovill, S.; Rempe, D.

    2016-12-01

    Water availability regulates ecosystem function, particularly in seasonally dry climates where lack of moisture in the growing season acts as an ecological bottleneck. Water within hillslopes is extracted by plants during transpiration and also delivered to streams to support baseflow for riparian ecosystems and human use. How water is stored and then released from hillslopes is strongly influenced by the structure of the critical zone (CZ) that emerges from the complex interaction of lithology, climate, and tectonics. Here we show how contrasting CZ development has extreme ecohydrological consequences in the seasonally dry climate of the Northern California Coast Ranges. To explore how the CZ transmits and stores water, we studied hydrologic dynamics at two sites with similar climate across belts of the Franciscan Formation in the Eel River CZO. We monitored plant water use, precipitation inputs and stream runoff, groundwater and vadose zone moisture dynamics and documented near-surface hydraulic conductivity and runoff-generation processes. We investigated CZ structure via boreholes and geophysical methods. We find that CZ thickness determines the extent to which hillslopes `shed' or `store' wet season precipitation, and fundamentally controls the structure of plant communities and summer low-flows. In a climate where winter precipitation regularly exceeds 2000 mm, the thin CZ of the sheared argillite matrix Central belt rapidly fills, resulting in wet-season saturation overland flow that drives flashy winter runoff in channels that then quickly run dry in the early summer. The maximum unsaturated moisture storage of approximately 200 mm is sufficient to host an ecologically diverse yet sparsely forested oak savanna. In contrast, the thick CZ of the interbedded argillite and greywacke Coastal belt stores up to 600 mm of winter precipitation in the unsaturated zone and a seasonal groundwater system within fractured bedrock provides year-round flow to channels

  16. Three Dimensional Modeling of Agricultural Contamination of Groundwater: a Case Study in the Nebraska Management Systems Evaluation Area (MSEA) Site

    NASA Astrophysics Data System (ADS)

    Akbariyeh, S.; Snow, D. D.; Bartelt-Hunt, S.; Li, X.; Li, Y.

    2015-12-01

    Contamination of groundwater from nitrogen fertilizers and pesticides in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater, impacting future uses of this limited resource. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have been validated based on realistic three dimensional soil lithology, hydrological conditions, and historical changes in groundwater quality. In this work, contamination of groundwater in the Nebraska Management Systems Evaluation Area (MSEA) site was simulated based on extensive field data including (1) lithology from 69 wells and 11 test holes; (2) surface soil type, land use, and surface elevations; (3) 5-year groundwater level and flow velocity; (4) daily meteorological monitoring; (5) 5-year seasonal irrigation records; (6) 5-years of spatially intensive contaminant concentration in 40 multilevel monitoring wells; and (7) detailed cultivation records. Using this data, a three-dimensional vadose zone lithological framework was developed using a commercial software tool (RockworksTM). Based on the interpolated lithology, a hydrological model was developed using HYDRUS-3D to simulate water flow and contaminant transport. The model was validated through comparison of simulated atrazine and nitrate concentration with historical data from 40 wells and multilevel samplers. The validated model will be used to predict potential changes in ground water quality due to agricultural contamination under future climate scenarios in the High Plain Aquifer system.

  17. Accommodating permafrost in contaminant transport modeling, a preliminary approach to modify the TREECS modeling tools

    NASA Astrophysics Data System (ADS)

    Ryder, J. L.; Dortch, M. S.; Johnson, B. E.

    2017-12-01

    Efforts are underway to adapt TREECS (Training Range Environmental Evaluation and Characterization System) for use in arctic or subarctic conditions where the extent and duration of snowpack and frozen ground may influence the development and concentration of contaminant plumes. TREECS is a multi-media model designed to aid facility managers in the long term stewardship of Army properties. TREECS includes sub-models for mass loading, soil, vadose zone, aquifer, and stream transport. Potential changes to the sub-models to improve the ability to model contaminant transport in areas with permafrost include accurately representing the dissolution of contaminants over a wider range of temperatures, estimating snow depth and ablation for both the hydrology and thermal conditions, determining ground freeze/thaw state and an average active layer depth, a more precise method to estimate a vertical transport time to a water table, and a soil interflow routine that adapts for permafrost condition. In this presentation we will show three sub-model comparisons 1) the use of the National Weather Service SNOW-17 model and the current TREECS snowmelt routines for input hydrology, 2) a Continuous Frozen Ground Index (CFGI) model and the Geophysical Institute Permafrost Lab model (GIPL 1.0) for determining active layer depth and summer season length, and 3) the use of HYDRUS-1D and the current TREECS vadose zone model for transport to the water table. The performance vs input needs, assumptions, and limitations of each approach, as well as the physical system uncertainties will also be discussed.

  18. Development of Hydrologic Characterization Technology of Fault Zones -- Phase I, 2nd Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Karasaki, Kenzi; Onishi, Tiemi; Black, Bill

    2009-03-31

    This is the year-end report of the 2nd year of the NUMO-LBNL collaborative project: Development of Hydrologic Characterization Technology of Fault Zones under NUMO-DOE/LBNL collaboration agreement, the task description of which can be found in the Appendix 3. Literature survey of published information on the relationship between geologic and hydrologic characteristics of faults was conducted. The survey concluded that it may be possible to classify faults by indicators based on various geometric and geologic attributes that may indirectly relate to the hydrologic property of faults. Analysis of existing information on the Wildcat Fault and its surrounding geology was performed. Themore » Wildcat Fault is thought to be a strike-slip fault with a thrust component that runs along the eastern boundary of the Lawrence Berkeley National Laboratory. It is believed to be part of the Hayward Fault system but is considered inactive. Three trenches were excavated at carefully selected locations mainly based on the information from the past investigative work inside the LBNL property. At least one fault was encountered in all three trenches. Detailed trench mapping was conducted by CRIEPI (Central Research Institute for Electric Power Industries) and LBNL scientists. Some intriguing and puzzling discoveries were made that may contradict with the published work in the past. Predictions are made regarding the hydrologic property of the Wildcat Fault based on the analysis of fault structure. Preliminary conceptual models of the Wildcat Fault were proposed. The Wildcat Fault appears to have multiple splays and some low angled faults may be part of the flower structure. In parallel, surface geophysical investigations were conducted using electrical resistivity survey and seismic reflection profiling along three lines on the north and south of the LBNL site. Because of the steep terrain, it was difficult to find optimum locations for survey lines as it is desirable for them to be

  19. Simulation of Flow and Long-Term Plutonium (Pu) Transport in the Vadose Zone at the Savannah River National Laboratory (SRNL)

    NASA Astrophysics Data System (ADS)

    Demirkanli, I.; Molz, F. J.; Kaplan, D. I.; Fjeld, R. A.; Serkiz, S. M.

    2006-05-01

    An improved understanding of flow and radionuclide transport in vadose zone sediments is fundamental to all types of future planning involving radioactive materials. One way to obtain such understanding is to perform long-term experimental studies of Pu transport in complex natural systems. With this in mind, a series of field experiments were initiated at the SRNL in the early 1980s. Lysimeters containing sources of different Pu oxidation states were placed in the shallow subsurface and left open to the natural environment for 2 to 11 years. At the end of the experiments, Pu activities were measured along vertical cores obtained from the lysimeters. Pu distributions were anomalous in nature, with transport from oxidized Pu sources being less than expected, and a small fraction of Pu from reduced sources moving more. Laboratory studies with lysimeter sediments suggested that surface-mediated, oxidation/reduction (redox) reactions could be responsible for the anomalous behavior, and this hypothesis is tested by performing both steady-state and transient Pu transport simulations that include retardation along with first-order redox reactions on mineral surfaces. Based on the simulations, we conclude that the surface-mediated, redox hypothesis is consistent with the observed downward Pu activity profiles in the experiments, and such profiles are captured well by a steady-state, net downward, flow model. (Discussion is presented as to why a steady model appears to work in a highly transient flow environment.) The redox model explains how Pu(V/VI) sources release activity that moves downward more slowly than expected based on adsorptive retardation alone, and how Pu(III/IV) sources result in a small fraction of activity that moves downward more rapidly than expected. The calibrated parameter values were robust and relatively well-defined throughout all four sets of simulations. Pu(V/VI) (i.e., oxidized Pu)retardation factors were about 15, and reduced Pu

  20. Improvements to measuring water flux in the vadose zone.

    PubMed

    Masarik, Kevin C; Norman, John M; Brye, Kristofor R; Baker, John M

    2004-01-01

    Evaluating the impact of land use practices on ground water quality has been difficult because few techniques are capable of monitoring the quality and quantity of soil water flow below the root zone without disturbing the soil profile and affecting natural flow processes. A recently introduced method, known as equilibrium tension lysimetry, was a major improvement but it was not a true equilibrium since it still required manual intervention to maintain proper lysimeter suction. We addressed this issue by developing an automated equilibrium tension lysimeter (AETL) system that continuously matches lysimeter tension to soil-water matric potential of the surrounding soil. The soil-water matric potential of the bulk soil is measured with a heat-dissipation sensor, and a small DC pump is used to apply suction to a lysimeter. The improved automated approach reported here was tested in the field for a 12-mo period. Powered by a small 12-V rechargeable battery, the AETLs were able to continuously match lysimeter suction to soil-water matric potential for 2-wk periods with minimal human attention, along with the added benefit of collecting continuous soil-water matric potential data. We also demonstrated, in the laboratory, methods for continuous measurement of water depth in the AETL, a capability that quantifies drainage on a 10-min interval, making it a true water-flux meter. Equilibrium tension lysimeters have already been demonstrated to be a reliable method of measuring drainage flux, and the further improvements have created a more effective device for studying water drainage and chemical leaching through the soil matrix.

  1. Effects of hydrology on red mangrove recruits

    USGS Publications Warehouse

    Doyle, Thomas W.

    2003-01-01

    Coastal wetlands along the Gulf of Mexico have been experiencing significant shifts in hydrology and salinity levels over the past century as a result of changes in sea level and freshwater drainage patterns. Local land management in coastal zones has also impacted the hydrologic regimes of salt marshes and mangrove areas. Parks and refuges in south Florida that contain mangrove forests have, in some cases, been ditched or impounded to control mosquito outbreaks and to foster wildlife use. And while mangroves dominate the subtropical coastlines of Florida and thrive in saltwater environments, little is known about how they respond to changes in hydrology under managed or variable tidal conditions. USGS researchers designed a study to evaluate the basic hydrological requirements of mangroves so that their health and survival may be more effectively managed in controlled impoundments and restored wetlands. Mangroves are commonly found in the intertidal zone (between low and high tides) in a rather broad spectrum of hydrologic settings. Because they thrive at the interface of land and sea, mangroves are subject to changes in freshwater flow (flow rate, nutrients, pollutants) and to marine influences (sea-level rise, salinity). Salinity has long been recognized as a controlling factor that determines the health and distribution of mangrove forests. Field and experimental observations indicate that most mangrove species achieve their highest growth potential under brackish conditions (modest salinity) between 10 and 20 parts per thousand (ppt). Yet, if provided with available propagules, successful regeneration, and limited competition from other plants, then mangroves can survive and thrive in freshwater systems as well. Because little is known about the growthand survival patterns of mangrove species relative to changing hydrology, USGS scientists conducted greenhouse and field experiments to determine how flooded or drained patterns of hydrology would influence

  2. What's so critical about the critical zone?: New insights at the boundaries between hydrology, pedology, geomorphology, rocks and life (Invited)

    NASA Astrophysics Data System (ADS)

    Grant, G.

    2013-12-01

    The great promise of critical zone science and observatories (CZOs) emerging over the past decade was that real progress towards understanding the earth's near-surface environment could be made through coordinated studies of processes and interactions that occur within that thin layer between the bottom of the atmosphere and the top of competent bedrock - the critical zone. How well has this promise been realized, and where is the science now headed? Drawing on recent findings from CZOs and elsewhere, I identify a number of exciting and potentially transformative new ideas and threads at the boundaries of hydrology, geomorphology, pedology, and ecology. These include: 1). New understanding of interactions and feedbacks among soil weathering, pathways for water, tree roots, and bedrock fractures. A fundamental insight emerging from critical zone studies is that soils are far more interestingly structured than simple textbook models of homogeneous substrates with exponentially decreasing permeability with depth. Instead, the near-surface is now seen as a complex network of voids, paths, conduits, and storage zones that are both formed and exploited by the movement of water, geochemical reactions, and organisms. This evolving perspective on the critical zone has implications for a wide range of issues, including the residence time and chemistry of water, rates of weathering, slope stability, and long-term soil fertility. 2. Growing appreciation for the role of biology in conditioning and transforming its own physical environment within the critical zone. This includes the role of trees in hydraulically redistributing water, fracturing bedrock, and contributing to long-term soil erosion and landscape evolution through tree fall and throw and vegetation effects on moisture regimes. 3. Similarly, the importance of understanding linkages among soils, water, and vegetation has never been greater as a warming climate dramatically changes the 'rules of the game'. New

  3. Using stable isotopes and major ions to identify hydrological processes and geochemical characteristics in a typical karstic basin, Guizhou, Southwest China.

    PubMed

    Han, Zhiwei; Tang, Changyuan; Wu, Pan; Zhang, Ruixue; Zhang, Chipeng

    2014-01-01

    The investigation of hydrological processes is very important for water resource development in karst basins. In order to understand these processes associated with complex hydrogeochemical evolution, a typical basin was chosen in Houzai, southwest China. The basin was hydrogeologically classified into three zones based on hydrogen and oxygen isotopes as well as the field surveys. Isotopic values were found to be enriched in zone 2 where paddy fields were prevailing with well-developed underground flow systems, and heavier than those in zone 1. Zone 3 was considered as the mixture of zones 1 and 2 with isotopic values falling in the range between the two zones. A conceptual hydrological model was thus proposed to reveal the probable hydrological cycle in the basin. In addition, major processes of long-term chemical weathering in the karstic basin were discussed, and reactions between water and carbonate rocks proved to be the main geochemical processes in karst aquifers.

  4. Tracer transport in soils and shallow groundwater: model abstraction with modern tools

    USDA-ARS?s Scientific Manuscript database

    Vadose zone controls contaminant transport from the surface to groundwater, and modeling transport in vadose zone has become a burgeoning field. Exceedingly complex models of subsurface contaminant transport are often inefficient. Model abstraction is the methodology for reducing the complexity of a...

  5. Preferential flow in the vadose zone and interface dynamics: Impact of microbial exudates

    NASA Astrophysics Data System (ADS)

    Li, Biting; Pales, Ashley R.; Clifford, Heather M.; Kupis, Shyla; Hennessy, Sarah; Liang, Wei-Zhen; Moysey, Stephen; Powell, Brian; Finneran, Kevin T.; Darnault, Christophe J. G.

    2018-03-01

    In the hydrological cycle, the infiltration process is a critical component in the distribution of water into the soil and in the groundwater system. The nonlinear dynamics of the soil infiltration process yield preferential flow which affects the water distribution in soil. Preferential flow is influenced by the interactions between water, soil, plants, and microorganisms. Although the relationship among the plant roots, their rhizodeposits and water transport in soil has been the subject of extensive study, the effect of microbial exudates has been studied in only a few cases. Here the authors investigated the influence of two artificial microbial exudates-catechol and riboflavin-on the infiltration process, particularly unstable fingered flow, one form of preferential flow. Flow experiments investigating the effects of types and concentrations of microbial exudates on unstable fingered flow were conducted in a two-dimensional tank that was filled with ASTM

  6. Baseline Characterization of Forested Headwater Stream Hydrology and Water Chemistry in Southwest Georgia

    Treesearch

    David G. Jones; William B. Summer; Masato Miwa; C. Rhett Jackson

    2004-01-01

    Stream hydrology and water quality in headwater streams are important components of ecosystem health. The Dry Creek Long-Term Watershed Study is designed to evaluate the effects of upland forestry operations and stream management zone (SMZ) thinning on stream hydrology, water quality, benthic macroinvertebrates, and other biologicindicators. The study also tests the...

  7. The Evolution of Root Zone Storage Capacity after Land Use Change

    NASA Astrophysics Data System (ADS)

    Nijzink, Remko C.; Hutton, Christopher; Pechlivanidis, Ilias; Capell, René; Arheimer, Berit; Wagener, Thorsten; Savenije, Hubert H. G.; Hrachowitz, Markus

    2016-04-01

    Root zone storage capacity forms a crucial parameter in ecosystem functioning as it is the key parameter that determines the partitioning between runoff and transpiration. There is increasing evidence from several case studies for specific plants that vegetation adapts to the critical situation of droughts. For example, trees will, on the long term, try to improve their internal hydraulic conductivity after droughts, for example by allocating more biomass for roots. In spite of this understanding, the water storage capacity in the root zone is often treated as constant in hydrological models. In this study, it was hypothesized that root zone storage capacities are altered by deforestation and the regrowth of the ecosystem. Three deforested sub catchments as well as not affected, nearby control catchments of the experimental forests of HJ Andrews and Hubbard Brook were selected for this purpose. Root zone storage capacities were on the one hand estimated by a climate-based approach similar to Gao et al. (2014), making use of simple water balance considerations to determine the evaporative demand of the system. In this way, the maximum deficit between evaporative demand and precipitation allows a robust estimation of the root zone storage capacity. On the other hand, three conceptual hydrological models (FLEX, HYPE, HYMOD) were calibrated in a moving window approach for all catchments. The obtained model parameter values representing the root zone storage capacities of the individual catchments for each moving window period were then compared to the estimates derived from climate data for the same periods. Model- and climate-derived estimates of root zone storage capacities both showed a similar evolution. In the deforested catchments, considerable reductions of the root zone storage capacities, compared to the pre-treatment situation and control catchments, were observed. In addition, the years after forest clearing were characterized by a gradual recovery of the

  8. DEMONSTRATION BULLETIN: IN-SITU VACUUM EXRACTION: TERRA VAC, INC.

    EPA Science Inventory

    This in-situ vacuum extraction technology is a process for the removal and venting of volatile organic compounds (VOCs) from the vadose or unsaturated zone of soils. Often, these compounds can be removed from the vadose zone before they have a chance to contaminate groundwater. ...

  9. Hydrological modelling of the Mara River Basin, Kenya: Application of the Normalised Difference Infrared Index (NDII)

    NASA Astrophysics Data System (ADS)

    Hulsman, Petra; Savenije, Hubert; Bogaard, Thom

    2017-04-01

    In hydrology and water resources management, precipitation and discharge are the main time series for hydrological modelling. However, in African river catchments, the quantity and quality of the available precipitation stations and discharge measurements are unfortunately often inadequate for reliable hydrological modelling. To cope with these uncertainties, this study proposes to calibrate on water levels and to constrain the model using the Normalised Difference Infrared Index (NDII) as a proxy for root zone moisture stress. With the NDII, the leaf water content can be monitored. Previous studies related the NDII to the equivalent water thickness (EWT) of leaves, which is used to determine the vegetation water content (VWC). As the water content in the leaves is related to the water content in the root zone, the NDII can also be used as indicator of the soil moisture content in the root zone. In previous studies it was found that the root zone moisture content is exponentially correlated to the NDII during periods of moisture stress. In this study, the semi-distributed rainfall runoff model FLEX-Topo has been applied to the Mara River Basin. In this model seven sub-basins are distinguished and four hydrological response units with each a unique model structure based on the expected dominant flow processes. To calibrate the model, the water levels have been back-calculated from modelled discharges, using cross-section data and the Strickler formula calibrating parameter 'k•s1/2', and compared to measured water levels. In addition, the correlation between the NDII and root zone moisture content has been analysed for this river basin for each sub-catchment and hydrological response unit. Also, the application of the NDII as model constraint or for calibration has been analysed.

  10. Emergent Archetype Hydrological-Biogeochemical Response Patterns in Heterogeneous Catchments

    NASA Astrophysics Data System (ADS)

    Jawitz, J. W.; Gall, H. E.; Rao, P.

    2013-12-01

    What can spatiotemporally integrated patterns observed in stream hydrologic and biogeochemical signals generated in response to transient hydro-climatic and anthropogenic forcing tell us about the interactions between spatially heterogeneous soil-mediated hydrological and biogeochemical processes? We seek to understand how the spatial structure of solute sources coupled with hydrologic responses affect observed concentration-discharge (C-Q) patterns. These patterns are expressions of the spatiotemporal structure of solute loads exported from managed catchments, and their likely ecological consequences manifested in receiving water bodies (e.g., wetlands, rivers, lakes, and coastal waters). We investigated the following broad questions: (1) How does the correlation between flow-generating areas and biogeochemical source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and biogeochemical responses that lead to the emergence of the observed archetype C-Q patterns? and; (3) What implications do these coupled dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We introduce a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and biogeochemical filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the types and degree of spatial correlation between solute source zones and flow generating zones, and activation of different portions of the catchments during rainfall events. Our overarching hypothesis is that each of the archetype C-Q patterns can be generated by explicitly linking landscape-scale hydrologic responses and spatial distributions of solute source properties within a catchment. The model

  11. Hydrological regions in monsoon Asia

    NASA Astrophysics Data System (ADS)

    Kondoh, Akihiko; Budi Harto, Agung; Eleonora, Runtunuwu; Kojiri, Toshiharu

    2004-11-01

    Monsoon Asia is characterized by its diversity of natural and social environments. These environments range from humid tropics to arid regions and there exist associated various hydrological phenomena. This paper attempts to characterize the hydrological regions of monsoon Asia based on the water budget calculated using grid-based global datasets. A map of hydrological regions is created by ranking the value of water surplus and deficit. A humid zone with large water surplus extending from Southeast Asia to the Japanese archipelago, rapid transition from humid to arid environments in eastern China, and an arid region surrounded by a humid region in continental Southeast Asia are the most remarkable features in monsoon Asia. The map reveals that an essential characteristic of monsoon Asia is the proximity of the arid and humid environments. Many water problems and water management practices in a region can be easily understood by plotting them on a map. The boundaries of several large river basins are superimposed on the map, and examined for the water budget and flow regimes. The results are found to explain the regional characteristics of the seasonal runoff regimes satisfactorily. The importance of using a spatial framework for the comparative hydrological study in Monsoon Asia is highlighted.

  12. Hydrologic refugia, plants, and climate change.

    PubMed

    McLaughlin, Blair C; Ackerly, David D; Klos, P Zion; Natali, Jennifer; Dawson, Todd E; Thompson, Sally E

    2017-08-01

    Climate, physical landscapes, and biota interact to generate heterogeneous hydrologic conditions in space and over time, which are reflected in spatial patterns of species distributions. As these species distributions respond to rapid climate change, microrefugia may support local species persistence in the face of deteriorating climatic suitability. Recent focus on temperature as a determinant of microrefugia insufficiently accounts for the importance of hydrologic processes and changing water availability with changing climate. Where water scarcity is a major limitation now or under future climates, hydrologic microrefugia are likely to prove essential for species persistence, particularly for sessile species and plants. Zones of high relative water availability - mesic microenvironments - are generated by a wide array of hydrologic processes, and may be loosely coupled to climatic processes and therefore buffered from climate change. Here, we review the mechanisms that generate mesic microenvironments and their likely robustness in the face of climate change. We argue that mesic microenvironments will act as species-specific refugia only if the nature and space/time variability in water availability are compatible with the ecological requirements of a target species. We illustrate this argument with case studies drawn from California oak woodland ecosystems. We posit that identification of hydrologic refugia could form a cornerstone of climate-cognizant conservation strategies, but that this would require improved understanding of climate change effects on key hydrologic processes, including frequently cryptic processes such as groundwater flow. © 2017 John Wiley & Sons Ltd.

  13. Carbon Tetrachloride Flow and Transport in the Subsurface of the 216-Z-9 Trench at the Hanford Site

    NASA Astrophysics Data System (ADS)

    Oostrom, M.; Rockhold, M.; Truex, M.; Thorne, P.; Last, G.; Rohay, V.

    2006-12-01

    Three-dimensional modeling was conducted with layered and heterogeneous models to enhance the conceptual model of CT distribution in the vertical and lateral direction beneath the 216-Z-9 trench and to investigate the effects of soil vapor extraction (SVE). This work supports the U.S. Department of Energy's (DOE's) efforts to characterize the nature and distribution of CT in the 200 West Area and subsequently select an appropriate final remedy. Simulations targeted migration of dense, nonaqueous phase liquid (DNAPL) consisting of CT and co-disposed organics in the subsurface beneath the 216-Z-9 trench as a function of the properties and distribution of subsurface sediments and of the properties and disposal history of the waste. Simulations of CT migration were conducted using the Subsurface Transport Over Multiple Phases (STOMP) simulator. Simulation results support a conceptual model for CT distribution where CT in the DNAPL phase is expected to have migrated primarily in a vertical direction below the disposal trench. Presence of small-scale heterogeneities tends to limit the extent of vertical migration of CT DNAPL due to enhanced retention of DNAPL compared to more homogeneous conditions, but migration is still predominantly in the vertical direction. Results also show that the Cold Creek units retain more CT DNAPL within the vadose zone than other hydrologic unit during SVE. A considerable amount of the disposed CT DNAPL may have partitioned to the vapor and subsequently water and sorbed phases. Presence of small-scale heterogeneities tends to increase the amount of volatilization. Any continued migration of CT from the vadose zone to the groundwater is likely through interaction of vapor phase CT with the groundwater and not through continued DNAPL migration. The results indicated that SVE appears to be an effective technology for vadose zone remediation, but additional effort is needed to improve simulation of the SVE process.

  14. Unraveling the Fate and Transport of SrEDTA-2 and Sr+2 in Hanford Sediments

    NASA Astrophysics Data System (ADS)

    Pace, M. N.; Mayes, M. A.; Jardine, P. M.; Mehlhorn, T. L.; Liu, Q. G.; Yin, X. L.

    2004-12-01

    Accelerated migration of strontium-90 has been observed in the vadose zone beneath the Hanford tank farm. The goal of this paper is to provide an improved understanding of the hydrogeochemical processes that contribute to strontium transport in the far-field Hanford vadose zone. Laboratory scale batch, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core were conducted to quantify geochemical and hydrological processes controlling Sr+2 and SrEDTA-2 sorption to Hanford flood deposits. After experimentation, the undisturbed core was disassembled and samples were collected from different bedding units as a function of depth. Sequential extractions were then performed on the samples. It has been suggested that organic chelates such as EDTA may be responsible for the accelerated transport of strontium due to the formation of stable anionic complexes. Duplicate batch and column experiments performed with Sr+2 and SrEDTA-2 suggested that the SrEDTA-2 complex was not stable in the presence of soil and rapid dissociation allowed strontium to be transported as a divalent cation. Batch experiments indicated a decrease in sorption with increasing rock:water ratios, whereas saturated packed column experiments indicated equal retardation in columns of different lengths. This difference between the batch and column experiments is primarily due to the difference between equilibrium conditions where dissolution of cations may compete for sorption sites versus flowing conditions where any dissolved cations are flushed through the system minimizing competition for sorption sites. Unsaturated transport in the undisturbed core resulted in significant Sr+2 retardation despite the presence of physical nonequilibrium. Core disassembly and sequential extractions revealed the mass wetness distribution and reactive mineral phases associated with strontium in the core. Overall, results indicated that strontium will most likely be transported

  15. Technetium, Iodine, and Chromium Adsorption/Desorption Kd Values for Vadose Zone Pore Water, ILAW Glass, and Cast Stone Leachates Contacting an IDF Sand Sequence

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Last, George V.; Snyder, Michelle M.V.; Um, Wooyong

    Performance and risk assessments of immobilized low-activity waste (ILAW) at the Integrated Disposal Facility (IDF) have shown that risks to groundwater are quite sensitive to adsorption-desorption interactions occurring in the near- and far-field environment. These interactions between the underlying sediments and the contaminants present in the leachates that descend from the buried glass, secondary waste grouts, and potentially Cast Stone low-activity waste packages have been represented in these assessments using the contaminant distribution coefficient (Kd) construct. Some contaminants (99Tc, 129I, and Cr) present in significant quantities in these wastes have low Kd values and tend to drive risk to publicmore » health and the environment. Relatively small changes in the Kd value can cause relatively large changes in the retardation factor. Thus, even relatively small uncertainty in the Kd value can result in a relatively large uncertainty in the risk determined through performance assessment modeling. The purpose of this study is to further reduce the uncertainty in Kd values for 99Tc, iodine (iodide and iodate), and Cr (chromate; CrO42-) by conducting systematic adsorption-desorption experiments using actual sand-dominated Hanford formation sediments from beneath the IDF and solutions that closely mimic Hanford vadose zone pore water and leachates from Cast Stone and ILAW glass waste forms. Twenty-four batch and 21 flow-through column experiments were conducted, yielding 261 Kd measurements for these key contaminants, and contributing to our understanding for predicting transport from wastes disposed to the IDF. While the batch Kd methodology is not well-suited for measuring Kd values for non-sorbing species (as noted by the U.S. Environmental Protection Agency), the batch Kd results presented here are not wholly inconsistent with the column Kd results, and could be used for sensitivity purposes. Results from the column experiments are consistent with the

  16. Hydrologic functioning of the deep Critical Zone and contributions to streamflow in a high elevation catchment: testing of multiple conceptual models

    NASA Astrophysics Data System (ADS)

    Dwivedi, R.; Meixner, T.; McIntosh, J. C.; Ferre, T. P. A.; Eastoe, C. J.; Minor, R. L.; Barron-Gafford, G.; Chorover, J.

    2017-12-01

    The composition of natural mountainous waters maintains important control over the water quality available to downstream users. Furthermore, the geochemical constituents of stream water in the mountainous catchments represent the result of the spatial and temporal evolution of critical zone structure and processes. A key problem is that high elevation catchments involve rugged terrain and are subject to extreme climate and landscape gradients; therefore, high density or high spatial resolution hydro-geochemical observations are rare. Despite such difficulties, the Santa Catalina Mountains Critical Zone Observatory (SCM-CZO), Tucson, AZ, generates long-term hydrogeochemical data for understanding not only hydrological processes and their seasonal characters, but also the geochemical impacts of such processes on streamflow chemical composition. Using existing instrumentation and hydrogeochemical observations from the last 9+ years (2009 through 2016 and an initial part of 2017), we employed a multi-tracer approach along with principal component analysis to identify water sources and their seasonal character. We used our results to inform hydrological process understanding (flow paths, residence times, and water sources) for our study site. Our results indicate that soil water is the largest contributor to streamflow, which is ephemeral in nature. Although a 3-dimensional mixing space involving precipitation, soil water, interflow, and deep groundwater end-members could explain most of the streamflow chemistry, geochemical complexity was observed to grow with catchment storage. In terms of processes and their seasonal character, we found soil water and interflow were the primary end-member contributors to streamflow in all seasons. Deep groundwater only contributes to streamflow at high catchment storage conditions, but it provides major ions such as Na, Mg, and Ca that are lacking in other water types. In this way, our results indicate that any future efforts aimed

  17. Solute Transport Dynamics in a Large Hyporheic Corridor System

    NASA Astrophysics Data System (ADS)

    Zachara, J. M.; Chen, X.; Murray, C. J.; Shuai, P.; Rizzo, C.; Song, X.; Dai, H.

    2016-12-01

    A hyporheic corridor is an extended zone of groundwater surface water-interaction that occurs within permeable aquifer sediments in hydrologic continuity with a river. These systems are dynamic and tightly coupled to river stage variations that may occur over variable time scales. Here we describe the behavior of a persistent uranium (U) contaminant plume that exists within the hyporheic corridor of a large, managed river system - the Columbia River. Temporally dense monitoring data were collected for a two year period from wells located within the plume at varying distances up to 400 m from the river shore. Groundwater U originates from desorption of residual U in the lower vadose zone during periods of high river stage and associated elevated water table. U is weakly adsorbed to aquifer sediments because of coarse texture, and along with specific conductance, serves as a tracer of vadose zone source terms, solute transport pathways, and groundwater-surface water mixing. Complex U concentration and specific conductance trends were observed for all wells that varied with distance from the river shoreline and the river hydrograph, although trends for each well were generally repeatable for each year during the monitoring period. Statistical clustering analysis was used to identify four groups of wells that exhibited common trends in dissolved U and specific conductance. A flow and reactive transport code, PFLOTRAN, was implemented within a hydrogeologic model of the groundwater-surface water interaction zone to provide insights on hydrologic processes controlling monitoring trends and cluster behavior. The hydrogeologic model was informed by extensive subsurface characterization, with the spatially variable topography of a basal aquitard being one of several key parameters. Numerical tracer experiments using PFLOTRAN revealed the presence of temporally complex flow trajectories, spatially variable domains of groundwater - river water mixing, and locations of

  18. Paleomagnetism of Basaltic Lava Flows in Coreholes ICPP 213, ICPP-214, ICPP-215, and USGS 128 Near the Vadose Zone Research Park, Idaho Nuclear Technology and Engineering Center, Idaho National Engineering and Environmental Laboratory, Idaho

    USGS Publications Warehouse

    Champion, Duane E.; Herman, Theodore C.

    2003-01-01

    A paleomagnetic study was conducted on basalt from 41 lava flows represented in about 2,300 ft of core from coreholes ICPP-213, ICPP-214, ICPP-215, and USGS 128. These wells are in the area of the Idaho Nuclear Technology and Engineering Center (INTEC) Vadose Zone Research Park within the Idaho National Engineering and Environmental Laboratory (INEEL). Paleomagnetic measurements were made on 508 samples from the four coreholes, which are compared to each other, and to surface outcrop paleomagnetic data. In general, subhorizontal lines of correlation exist between sediment layers and between basalt layers in the area of the new percolation ponds. Some of the basalt flows and flow sequences are strongly correlative at different depth intervals and represent important stratigraphic unifying elements. Some units pinch out, or thicken or thin even over short separation distances of about 1,500 ft. A more distant correlation of more than 1 mile to corehole USGS 128 is possible for several of the basalt flows, but at greater depth. This is probably due to the broad subsidence of the eastern Snake River Plain centered along its topographic axis located to the south of INEEL. This study shows this most clearly in the oldest portions of the cored sections that have differentially subsided the greatest amount.

  19. Balancing practicality and hydrologic realism: a parsimonious approach for simulating rapid groundwater recharge via unsaturated-zone preferential flow

    USGS Publications Warehouse

    Mirus, Benjamin B.; Nimmo, J.R.

    2013-01-01

    The impact of preferential flow on recharge and contaminant transport poses a considerable challenge to water-resources management. Typical hydrologic models require extensive site characterization, but can underestimate fluxes when preferential flow is significant. A recently developed source-responsive model incorporates film-flow theory with conservation of mass to estimate unsaturated-zone preferential fluxes with readily available data. The term source-responsive describes the sensitivity of preferential flow in response to water availability at the source of input. We present the first rigorous tests of a parsimonious formulation for simulating water table fluctuations using two case studies, both in arid regions with thick unsaturated zones of fractured volcanic rock. Diffuse flow theory cannot adequately capture the observed water table responses at both sites; the source-responsive model is a viable alternative. We treat the active area fraction of preferential flow paths as a scaled function of water inputs at the land surface then calibrate the macropore density to fit observed water table rises. Unlike previous applications, we allow the characteristic film-flow velocity to vary, reflecting the lag time between source and deep water table responses. Analysis of model performance and parameter sensitivity for the two case studies underscores the importance of identifying thresholds for initiation of film flow in unsaturated rocks, and suggests that this parsimonious approach is potentially of great practical value.

  20. Origin of increased sulfate in groundwater at the ETF disposal site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thornton, E.C.

    1997-09-01

    Treated effluent being discharged to the vadose zone from the C-018H Effluent Treatment Facility (ETF) at the Hanford Site has infiltrated vertically to the unconfined aquifer, as indicated by increasing tritium activity levels in the groundwater. Well 699-48-77A, in particular, exhibits increased levels of tritium and also sulfate in the groundwater. The origin of increased sulfate levels in the groundwater is attributed to the dissolution of gypsum as the effluent flows through the vadose zone. This is supported by the observation that sulfate was found to be present in soils collected from the vadose zone at an average value ofmore » about 10.6 ppm. The maximum observed sulfate concentration of 190 mg/L from well 699-48-77A was observed on August 6, 1996, and is less than the maximum value of 879 mg/L that potentially could be achieved if water in the vadose zone was to attain saturation with respect to gypsum and calcite. It is suggested that infiltration rates were high enough that the effluent did not completely equilibrate with gypsum in the vadose zone, and thus, sulfate levels remained below gypsum saturation levels. Sulfate levels appear to be dropping, which may be attributed to the completion of the dissolution of the bulk of gypsum present along the vadose zone flow path traversed by the effluent. Geochemical modeling was undertaken to evaluate the influence of effluent chemistry on sulfate concentration levels in the presence of excess calcite and gypsum. In general, the effect is fairly minor for dilute solutions, but becomes more significant for concentrated solutions.« less

  1. The Vapor-phase Multi-stage CMD Test for Characterizing Contaminant Mass Discharge Associated with VOC Sources in the Vadose Zone: Application to Three Sites in Different Lifecycle Stages of SVE Operations

    PubMed Central

    Brusseau, M.L.; Mainhagu, J.; Morrison, C.; Carroll, K.C.

    2015-01-01

    Vapor-phase multi-stage contaminant mass discharge (CMD) tests were conducted at three field sites to measure mass discharge associated with contaminant sources located in the vadose zone. The three sites represent the three primary stages along the soil vapor extraction (SVE) operations lifecycle- pre/initial-SVE, mid-lifecycle, and near-closure. A CMD of 32 g/d was obtained for a site at which soil vapor SVE has been in operation for approximately 6 years, and for which mass removal is currently in the asymptotic stage. The contaminant removal behavior exhibited for the vapor extractions conducted at this site suggests that there is unlikely to be a significant mass of non-vapor-phase contaminant (e.g., DNAPL, sorbed phase) remaining in the advective domains, and that most remaining mass is likely located in poorly accessible domains. Given the conditions for this site, this remaining mass is hypothesized to be associated with the low-permeability (and higher water saturation) region in the vicinity of the saturated zone and capillary fringe. A CMD of 25 g/d was obtained for a site wherein SVE has been in operation for several years but concentrations and mass-removal rates are still relatively high. A CMD of 270 g/d was obtained for a site for which there were no prior SVE operations. The behavior exhibited for the vapor extractions conducted at this site suggest that non-vapor-phase contaminant mass (e.g., DNAPL) may be present in the advective domains. Hence, the asymptotic conditions observed for this site most likely derive from a combination of rate-limited mass transfer from DNAPL (and sorbed) phases present in the advective domain as well as mass residing in lower-permeability (“non-advective”) regions. The CMD values obtained from the tests were used in conjunction with a recently developed vapor-discharge tool to evaluate the impact of the measured CMDs on groundwater quality. PMID:26047819

  2. The vapor-phase multi-stage CMD test for characterizing contaminant mass discharge associated with VOC sources in the vadose zone: Application to three sites in different lifecycle stages of SVE operations.

    PubMed

    Brusseau, M L; Mainhagu, J; Morrison, C; Carroll, K C

    2015-08-01

    Vapor-phase multi-stage contaminant mass discharge (CMD) tests were conducted at three field sites to measure mass discharge associated with contaminant sources located in the vadose zone. The three sites represent the three primary stages of the soil vapor extraction (SVE) operations lifecycle-pre/initial-SVE, mid-lifecycle, and near-closure. A CMD of 32g/d was obtained for a site at which soil vapor SVE has been in operation for approximately 6years, and for which mass removal is currently in the asymptotic stage. The contaminant removal behavior exhibited for the vapor extractions conducted at this site suggests that there is unlikely to be a significant mass of non-vapor-phase contaminant (e.g., DNAPL, sorbed phase) remaining in the advective domains, and that most remaining mass is likely located in poorly accessible domains. Given the conditions for this site, this remaining mass is hypothesized to be associated with the low-permeability (and higher water saturation) region in the vicinity of the saturated zone and capillary fringe. A CMD of 25g/d was obtained for a site wherein SVE has been in operation for several years but concentrations and mass-removal rates are still relatively high. A CMD of 270g/d was obtained for a site for which there were no prior SVE operations. The behavior exhibited for the vapor extractions conducted at this site suggest that non-vapor-phase contaminant mass (e.g., DNAPL) may be present in the advective domains. Hence, the asymptotic conditions observed for this site most likely derive from a combination of rate-limited mass transfer from DNAPL (and sorbed) phases present in the advective domain as well as mass residing in lower-permeability ("non-advective") regions. The CMD values obtained from the tests were used in conjunction with a recently developed vapor-discharge tool to evaluate the impact of the measured CMDs on groundwater quality. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Assessing geotechnical centrifuge modelling in addressing variably saturated flow in soil and fractured rock.

    PubMed

    Jones, Brendon R; Brouwers, Luke B; Van Tonder, Warren D; Dippenaar, Matthys A

    2017-05-01

    The vadose zone typically comprises soil underlain by fractured rock. Often, surface water and groundwater parameters are readily available, but variably saturated flow through soil and rock are oversimplified or estimated as input for hydrological models. In this paper, a series of geotechnical centrifuge experiments are conducted to contribute to the knowledge gaps in: (i) variably saturated flow and dispersion in soil and (ii) variably saturated flow in discrete vertical and horizontal fractures. Findings from the research show that the hydraulic gradient, and not the hydraulic conductivity, is scaled for seepage flow in the geotechnical centrifuge. Furthermore, geotechnical centrifuge modelling has been proven as a viable experimental tool for the modelling of hydrodynamic dispersion as well as the replication of similar flow mechanisms for unsaturated fracture flow, as previously observed in literature. Despite the imminent challenges of modelling variable saturation in the vadose zone, the geotechnical centrifuge offers a powerful experimental tool to physically model and observe variably saturated flow. This can be used to give valuable insight into mechanisms associated with solid-fluid interaction problems under these conditions. Findings from future research can be used to validate current numerical modelling techniques and address the subsequent influence on aquifer recharge and vulnerability, contaminant transport, waste disposal, dam construction, slope stability and seepage into subsurface excavations.

  4. Open source data assimilation framework for hydrological modeling

    NASA Astrophysics Data System (ADS)

    Ridler, Marc; Hummel, Stef; van Velzen, Nils; Katrine Falk, Anne; Madsen, Henrik

    2013-04-01

    processes from a different domain or have different spatial and temporal resolutions. An open source framework that bridges OpenMI and OpenDA is presented. The framework provides a generic and easy means for any OpenMI compliant model to assimilate observation measurements. An example test case will be presented using MikeSHE, and OpenMI compliant fully coupled integrated hydrological model that can accurately simulate the feedback dynamics of overland flow, unsaturated zone and saturated zone.

  5. Pedologic influences on hillslope hydrology: The relationships between soil and hydrologic connectivity in a Californian oak-woodland

    NASA Astrophysics Data System (ADS)

    Alldritt, K.; O'Geen, A.; Dahlgren, R. A.

    2013-12-01

    EMI showed potential in showing the discontinuous distribution of the claypan, a horizon characterized by a large and abrupt increase in clay content and very low permeability. The data obtained from the transect excavation was used to create a two-dimensional hillslope model using HYDRUS-2D. Coupled with the soil moisture and local precipitation data the hillslope hydrology was modeled at individual storm event time scale. The field data showed that the hillslope was very complex and comprised of a discontinuous claypan, undulating bedrock topography and highly variable saprolite. The soil moisture data and modeling efforts showed that the surface horizons, which are highly permeable and contain numerous macropores, are the primary hydrologic flowpaths during storm events. The model showed that the presence of claypan decreased effective soil depth, increased antecedent wetness and created a perched water table. The model also showed that the undulating bedrock acted like a dam along the hillslope. The claypan network and undulating bedrock created isolated zones of wetness that only become connected and flow downhill into the stream when a storm caused the disconnected zones to rise in the highly permeable surface horizons.

  6. Hydrologic and Soil Science in a Mediterranean Critical Zone Observatory: Koiliaris River Basin

    NASA Astrophysics Data System (ADS)

    Nikolaidis, Nikolaos; Stamati, Fotini; Schnoor, Jerald; Moraetis, Daniel; Kotronakis, Manolis

    2010-05-01

    The Koiliaris River watershed is situated 25km east from the city of Chania, Crete, Greece. The total watershed area is 145km2 and the main supply of water originates in the White Mountains. At high elevations (altitude 2014 m), the maximum slope is 43% while at the lower elevations the slope measures 1-2%. Land use includes heterogeneous agricultural areas (25.4%), olive and orange groves (15.6%), and scrub and/or herbaceous vegetation associations (57.6%). The geology of the Basin consists of 23.8% Plattenkalk (dolomites, marbles, limestone and re-crystallized limestone with cherts); 31% of Trypali units (re-crystallized calcaric breccias); 9.4% limestones with marls in Neogene formations; 13% marls in Neogene formations; 12.8% schists, and 10% quaternary alluvial deposits. Intensive hydrologic and geochemical monitoring has been conducted since 2004 while the site has historical data since the ‘60s. In addition, a telemetric high-frequency hydrologic and water quality monitoring station has been deployed to obtain data for the characterization of the hydrologic and biogeochemical processes with varying process response-times. Hydrologic and geochemical modeling confirms the estimation of characteristic times of these processes. The main type of soil degradation in the basin as well as in other arid and semi-arid regions is water erosion, which is due to the clearing of forests and natural vegetation for cropping and livestock grazing. De-vegetation and inappropriate cultivation practices induces soil organic matter (SOM) losses making soils susceptible to erosion and desertification with global consequences for food security, climate change, biodiversity, water quality, and agricultural economy. Cropland plowing breaks-up water stable aggregates making the bio-available pool bio-accessible; which could be microbially attacked and oxidized resulting in SOM decline. Chronosequence data analysis suggested first-order kinetic rate of decline of the bio

  7. FINAL REPORT: Temporal and Spatial Distribution of Soil Moisture in Heterogeneous Vadose Zone with Moisture Barriers as Affected by Atmospheric Boundary Conditions

    DTIC Science & Technology

    2015-12-07

    Wallen, B., K.M. Smits and S.E. Howington. Thermal conductivity of binary sand mixtures evaluated through the full range of saturation. Hydrology Days...and T.H. Illangasekare. 2011. Thermal conductivity of soils as affected by temperature, Proceedings from Hydrology Days. Colorado State University...is mixed with very fine soil). Although it is well known that the apparent thermal conductivity (λ) of partially wet soil is a function of water (θ

  8. Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zachara, John M.; Freshley, Mark D.; Last, George V.

    2012-11-01

    The 300 Area uranium groundwater plume in the 300-FF-5 Operable Unit is residual from past discharge of nuclear fuel fabrication wastes to a number of liquid (and solid) disposal sites. The source zones in the disposal sites were remediated by excavation and backfilled to grade, but sorbed uranium remains in deeper, unexcavated vadose zone sediments. In spite of source term removal, the groundwater plume has shown remarkable persistence, with concentrations exceeding the drinking water standard over an area of approximately 1 km2. The plume resides within a coupled vadose zone, groundwater, river zone system of immense complexity and scale. Interactionsmore » between geologic structure, the hydrologic system driven by the Columbia River, groundwater-river exchange points, and the geochemistry of uranium contribute to persistence of the plume. The U.S. Department of Energy (DOE) recently completed a Remedial Investigation/Feasibility Study (RI/FS) to document characterization of the 300 Area uranium plume and plan for beginning to implement proposed remedial actions. As part of the RI/FS document, a conceptual model was developed that integrates knowledge of the hydrogeologic and geochemical properties of the 300 Area and controlling processes to yield an understanding of how the system behaves and the variables that control it. Recent results from the Hanford Integrated Field Research Challenge site and the Subsurface Biogeochemistry Scientific Focus Area Project funded by the DOE Office of Science were used to update the conceptual model and provide an assessment of key factors controlling plume persistence.« less

  9. Hydrology Domain Cyberinfrastructures: Successes, Challenges, and Opportunities

    NASA Astrophysics Data System (ADS)

    Horsburgh, J. S.

    2015-12-01

    Anticipated changes to climate, human population, land use, and urban form will alter the hydrology and availability of water within the water systems on which the world's population relies. Understanding the effects of these changes will be paramount in sustainably managing water resources, as well as maintaining associated capacity to provide ecosystem services (e.g., regulating flooding, maintaining instream flow during dry periods, cycling nutrients, and maintaining water quality). It will require better information characterizing both natural and human mediated hydrologic systems and enhanced ability to generate, manage, store, analyze, and share growing volumes of observational data. Over the past several years, a number of hydrology domain cyberinfrastructures have emerged or are currently under development that are focused on providing integrated access to and analysis of data for cross-domain synthesis studies. These include the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) Hydrologic Information System (HIS), the Critical Zone Observatory Information System (CZOData), HyroShare, the BiG CZ software system, and others. These systems have focused on sharing, integrating, and analyzing hydrologic observations data. This presentation will describe commonalities and differences in the cyberinfrastructure approaches used by these projects and will highlight successes and lessons learned in addressing the challenges of big and complex data. It will also identify new challenges and opportunities for next generation cyberinfrastructure and a next generation of cyber-savvy scientists and engineers as developers and users.

  10. An update of hydrologic conditions and distribution of selected constituents in water, eastern Snake River Plain aquifer and perched groundwater zones, Idaho National Laboratory, Idaho, emphasis 2012-15

    USGS Publications Warehouse

    Bartholomay, Roy C.; Maimer, Neil V.; Rattray, Gordon W.; Fisher, Jason C.

    2017-04-10

    Since 1952, wastewater discharged to in ltration ponds (also called percolation ponds) and disposal wells at the Idaho National Laboratory (INL) has affected water quality in the eastern Snake River Plain (ESRP) aquifer and perched groundwater zones underlying the INL. The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, maintains groundwater-monitoring networks at the INL to determine hydrologic trends and to delineate the movement of radiochemical and chemical wastes in the aquifer and in perched groundwater zones. This report presents an analysis of water-level and water-quality data collected from the ESRP aquifer, multilevel monitoring system (MLMS) wells in the ESRP aquifer, and perched groundwater wells in the USGS groundwater monitoring networks during 2012-15.

  11. Borehole environmental tracers for evaluating net infiltration and recharge through desert bedrock

    USGS Publications Warehouse

    Heilweil, V.M.; Solomon, D.K.; Gardner, P.M.

    2006-01-01

    Permeable bedrock aquifers in arid regions are being increasingly developed as water supplies, yet little is generally known about recharge processes and spatial and temporal variability. Environmental tracers from boreholes were used in this study to investigate net infiltration and recharge to the fractured Navajo Sandstone aquifer. Vadose zone tracer profiles at the Sand Hollow study site in southwestern Utah look similar to those of desert soils at other sites, indicating the predominance of matrix flow. However, recharge rates are generally higher in the Navajo Sandstone than in unconsolidated soils in similar climates because the sandstone matrix allows water movement but not root penetration. Water enters the vadose zone either as direct infiltration of precipitation through exposed sandstone and sandy soils or as focused infiltration of runoff. Net infiltration and recharge exhibit extreme spatial variability. High-recharge borehole sites generally have large amounts of vadose zone tritium, low chloride concentrations, and small vadose zone oxygen-18 evaporative shifts. Annual net-infiltration and recharge rates at different locations range from about 1 to 60 mm as determined using vadose zone tritium, 0 to 15 mm using vadose zone chloride, and 3 to 60 mm using groundwater chloride. Environmental tracers indicate a cyclical net-infiltration and recharge pattern, with higher rates earlier in the Holocene and lower rates during the late Holocene, and a return to higher rates during recent decades associated with anomalously high precipitation during the latter part of the 20th century. The slightly enriched stable isotopic composition of modern groundwater indicates this recent increase in precipitation may be caused by a stronger summer monsoon or winter southern Pacific El Nin??o storm track. ?? Soil Science Society of America.

  12. Miscellaneous chemical basin expedited site characterization report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Riha, B.D.; Pemberton, B.E.; Rossabi, J.

    1996-12-01

    A total of twenty nine cone penetrometer test (CPT) pushes in three weeks were conducted for vadose zone characterization of the Miscellaneous Chemical Basin (MCB) waste unit at the Savannah River Site. The shallow, unlined basin received liquid chemical wastes over an 18 year period beginning in 1956. This characterization was initiated to determine the vertical and lateral extent of contamination in the vadose zone and to install vadose zone wells for remediation by barometric pumping or active vapor extraction to help prevent further contamination of groundwater. The CPT locations within the waste site were selected based on results frommore » previous shallow soil gas surveys, groundwater contamination data, and the suspected basin center. Geophysical data and soil gas samples were collected at twenty five locations and twenty five vadose zone wells were installed. The wells were screened to target the clay zones and areas of higher soil gas concentrations. The well construction diagrams are provided in Appendix B. Baro-Ball{trademark} valves for enhanced barometric pumping were installed on each well upon completion to immediately begin the remediation treatability study at the site.« less

  13. Modelling of agricultural diffuse pollution and mitigation measures effectiveness in Wallonia (Belgium)

    NASA Astrophysics Data System (ADS)

    Sohier, C.; Deraedt, D.; Degré, A.

    2012-04-01

    Implementation of European directives in the environmental field and, specially, in the water management field, generates a request from policy-makers for news tools able to evaluate impact of management measures aiming at reducing pressures on ecosystems. In Wallonia (Southern Region of Belgium), the Nitrate Directive (EEC/676/91) was transposed into the "Walloon action plan for nitrogen sustainable management in agriculture" (PGDA1) in 2002. In 2007, a second plan was launched to reinforce some topics (PGDA2). Furthermore, the goal of "good quality" of surface waters and groundwater imposed by the Water Framework Directive poses new challenges in water management. In this context, a "soil and vadose" hydrological model is used in order to evaluate diffuse pollutions and efficiency of mitigation measures. This model, called EPICgrid, has been developed at catchment scale with an original modular concept on the basis of the field scale "water-soil-plant" EPIC model (Williams J.R., Jones C.A., Dyke P.T. (1984). A modelling approach to determining the relationship between erosion and soil productivity. Transactions of the ASAE. 27, 129-144). The model estimates, for each HRU identified into a 1km2 grid, water and nutrients flows into the plant-soil-vadose zone system (Sohier C., Degré A., Dautrebande S. (2009). From root zone modelling to regional forecasting of nitrate concentration in recharge flows - The case of the Walloon Region (Belgium). Journal of Hydrology, Volume 369, Issues 3-4, 15 May 2009, Pages 350-359). The model is used to make prospective simulations in order to evaluate the impact of measures currently performed to reduce the effect of diffuse pollution on water surface quality and groundwater quality, at regional scale. Response of the soil-vadose zone to agricultural practices modification is analyzed for the deadlines of the Water Framework Directive: 2015, 2021 and 2027, taking into account two climatic scenarios. Simulations results showed

  14. Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization

    NASA Astrophysics Data System (ADS)

    Abou Najm, M. R.; Atallah, N. M.; Selker, J. S.; Roques, C.; Stewart, R. D.; Rupp, D. E.; Saad, G.; El-Fadel, M.

    2015-12-01

    Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization while still representing the functional hydraulic behavior of real porous media. We present a new method for experimentally estimating the pore structure of porous media using a combination of Newtonian and non-Newtonian fluids. The proposed method transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). This method allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation comparing the functional flow behavior of different soils to their modeled flow with N representative radii revealed the ability of the proposed method to represent the water retention and infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media that the use of different non-Newtonian fluids enables the definition of the radii and corresponding percent contribution to flow of multiple representative pores, thus improving the ability of pore-scale models to mimic the functional behavior of real porous media in terms of flow and porosity. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil

  15. Infiltration and recharge at Sand Hollow, an upland bedrock basin in southwestern Utah: Chapter I in Ground-water recharge in the arid and semiarid southwestern United States (Professional Paper 1703)

    USGS Publications Warehouse

    Heilweil, Victor M.; Solomon, D. Kip; Gardner, Philip M.; Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

    2007-01-01

    Permeable bedrock aquifers in arid regions of the southwestern United States are being used increasingly as a source of water for rapidly growing populations, yet in many areas little is known about recharge processes and amounts available for sustainable development. Environmental tracers were used in this study to investigate infiltration and recharge to the Navajo Sandstone at Sand Hollow in the eastern Mojave Desert of southwestern Utah. Average annual precipitation is about 210 millimeters per year. Tracers included bromide, chloride, deuterium, oxygen-18, and tritium. The basin-wide average recharge rate, based on ground-water chloride mass balance, is about 8 millimeters per year, or 4 percent of precipitation. However, infiltration and recharge are highly variable spatially within Sand Hollow. Recharge primarily occurs both as focused infiltration of runoff from areas of outcropping bedrock and as direct infiltration beneath coarse surficial soils. Locations with higher rates generally have lower vadose-zone and ground-water chloride concentrations, smaller vadose-zone oxygen-18 evaporative shifts, and higher ground-water tritium concentrations. Infiltration rates estimated from vadose-zone tritium concentrations at borehole sites within Sand Hollow range from 1 to more than 57 millimeters per year; rates calculated from average vadose-zone chloride concentrations between land surface and the bottom of the chloride bulge range from 0 to 9 millimeters per year; rates calculated from average vadose-zone chloride concentrations below the chloride bulge range from 0.5 to 15 millimeters per year; and rates calculated from ground-water chloride concentrations range from 3 to 60 millimeters per year. A two-end-member deuterium-mixing model indicates that about 85 percent of ground-water recharge in Sand Hollow occurs in the 50 percent of the basin covered by coarser soils and bedrock. Vadose-zone chloride concentrations at individual boreholes represent as much as

  16. Dynamics of Nutrients Transport in Onsite Wastewater Treatment Systems

    NASA Astrophysics Data System (ADS)

    Toor, G.; De, M.

    2013-05-01

    Domestic wastewater is abundant in nutrients¬ that originate from various activities in the households. In developed countries, wastewater is largely managed by (1) centralized treatment where wastewater from large population is collected, treated, and discharged and (2) onsite treatment where wastewater is collected from an individual house, treated, and dispersed onsite; this system is commonly known as septic system or onsite wastewater treatment system (OWTS) and consist of a septic tank (collects wastewater) and drain-field (disperses wastewater in soil). In areas with porous sandy soils, the transport of nutrients from drain-field to shallow groundwater is accelerated. To overcome this limitation, elevated disposal fields (commonly called mounds) on top of the natural soil are constructed to provide unsaturated conditions for wastewater treatment. Our objective was to study the dynamics of nitrogen (N) and phosphorus (P) transport in the vadose zone and groundwater in traditional and advanced OWTS. Soil water samples were collected from the vadose zone by using suction cup lysimeters and groundwater samples were collected by using piezometers. Collected samples (wastewater, soil-water, groundwater) were analyzed for various water quality parameters. The pH (4.39-4.78) and EC (0.28-0.34 dS/m) of groundwater was much lower than both wastewater and soil-water. In contrast to >50 mg/L of ammonium-N in wastewater, concentrations in all lysimeters (0.02-0.81 mg/L) and piezometers (0.01-0.82 mg/L) were <1 mg/L; suggesting that >99% disappeared (primarily nitrified) in the vadose zone (<1.05-m soil profile depth). In the vadose zone of advanced system, heterotrophic and autrotrophic denitrification reduced nitrate-N concentrations to <0.12 mg/L, compared with >20 mg/L in the vadose zones of traditional systems (drip dispersal and gravel trench). Concentrations of chloride showed a distinct pattern of nitrate-N breakthrough in vadose zone and groundwater; the

  17. Impact of material heterogeneity on solute transport behavior in the unsaturated zone of the Calcaire de Beauce aquifer (France)

    NASA Astrophysics Data System (ADS)

    Viel, Emelie; Coquet, Yves

    2016-04-01

    Since a few decades, the Calcaire de Beauce aquifer is contaminated with nitrate. The nitrate dynamics in the aquifer and in the surface soil are quite well understood, but its transport through the vadose zone remains largely unknown. When models fail to simulate nitrate concentrations in wells, preferential flow or physical non-equilibrium transport in soil and in the vadose zone is usually put forward to explain this failure. To study transport processes in the vadose zone of the Calcaire de Beauce aquifer, undisturbed cores (30 cm length and 20 cm diameter) have been taken below the deepest soil horizon. At the field scale, the vadose zone is composed of powdery limestone spatially very heterogeneous, and including a variable amount of coarse elements. Two columns were selected: column "6" is made of very fine homogeneous limestone whereas column "8" is very heterogeneous with a large proportion of coarse elements. Elution experiments have been performed on both columns. A tracer (Br- or DFBA) in a solution of 5 mM CaCl2 was spread as a pulse on the top of the column with a rainfall simulator. Input flow rate was kept constant for steady state cases, or suddenly closed for flux interruption cases. Outflow was collected as a function of time for tracer concentration measurement. The collected fractions were analyzed by HPLC (High-performance liquid chromatography) with a UV detector. Three types of experiments took place: • For steady state experiments, three rainfall rates, respectively 4, 8, and 16 mm/h, have been used to study the occurrence of immobile water in the columns. The tracer was injected during 120 min followed by CaCl2 tracer-free solution at same flow rate. • For flux-interruption experiments, only the 4 and 8 mm/h rainfall rates were used. The tracer was injected during 120 min, input and output fluxes were then stopped and restarted seven days later with the same flow rate. • For drainage experiments, only the 4 and 8 mm/h rainfall rates

  18. Differential soil respiration responses to changing hydrologic regimes

    Treesearch

    Vincent J. Pacific; Brian L. McGlynn; Diego A. Riveros-Iregui; Howard E. Epstein; Daniel L. Welsch

    2009-01-01

    Soil respiration is tightly coupled to the hydrologic cycle (i.e., snowmelt and precipitation timing and magnitude). We examined riparian and hillslope soil respiration across a wet (2005) and a dry (2006) growing season in a subalpine catchment. When comparing the riparian zones, cumulative CO2 efflux was 33% higher, and peak efflux occurred 17 days earlier during the...

  19. Scaling considerations related to interactions of hydrologic, pedologic and geomorphic processes (Invited)

    NASA Astrophysics Data System (ADS)

    Sidle, R. C.

    2013-12-01

    Hydrologic, pedologic, and geomorphic processes are strongly interrelated and affected by scale. These interactions exert important controls on runoff generation, preferential flow, contaminant transport, surface erosion, and mass wasting. Measurement of hydraulic conductivity (K) and infiltration capacity at small scales generally underestimates these values for application at larger field, hillslope, or catchment scales. Both vertical and slope-parallel saturated flow and related contaminant transport are often influenced by interconnected networks of preferential flow paths, which are not captured in K measurements derived from soil cores. Using such K values in models may underestimate water and contaminant fluxes and runoff peaks. As shown in small-scale runoff plot studies, infiltration rates are typically lower than integrated infiltration across a hillslope or in headwater catchments. The resultant greater infiltration-excess overland flow in small plots compared to larger landscapes is attributed to the lack of preferential flow continuity; plot border effects; greater homogeneity of rainfall inputs, topography and soil physical properties; and magnified effects of hydrophobicity in small plots. At the hillslope scale, isolated areas with high infiltration capacity can greatly reduce surface runoff and surface erosion at the hillslope scale. These hydropedologic and hydrogeomorphic processes are also relevant to both occurrence and timing of landslides. The focus of many landslide studies has typically been either on small-scale vadose zone process and how these affect soil mechanical properties or on larger scale, more descriptive geomorphic studies. One of the issues in translating laboratory-based investigations on geotechnical behavior of soils to field scales where landslides occur is the characterization of large-scale hydrological processes and flow paths that occur in heterogeneous and anisotropic porous media. These processes are not only affected

  20. Hydrology and Hyporheic Nitrogen Biogeochemistry in a Geomorphically Degraded Urban Stream

    EPA Science Inventory

    Few studies have investigated the relationship between hydrology and nitrogen biogeochemistry in hyporheic zones of degraded urban streams despite significant national efforts to restore such streams in attempts to improve the nutrient uptake functions in these ecosystems. We ex...

  1. The Relative Importance of the Vadose Zone in Multimedia Risk Assessment Modeling Applied at a National Scale: An Analysis of Benzene Using 3MRA

    NASA Astrophysics Data System (ADS)

    Babendreier, J. E.

    2002-05-01

    , along with the conceptual layout of an accompanying java-based paralleling software toolset. Preliminary work is also reported for a scenario involving Benzene disposal that describes the relative importance of the vadose zone in driving risk levels for ecological receptors and human health. Incorporating landfills, waste piles, aerated tanks, surface impoundments, and land application units, the site-based data used in the analysis included 201 national facilities representing 419 site-WMU combinations.

  2. U- and Th-Series Transport in a Sandy Aquifer in an Arid Climate

    NASA Astrophysics Data System (ADS)

    Reynolds, B. C.; Wasserburg, G. J.

    2001-12-01

    CTh appears to be controlled by local solubility limits, so that Th is precipitated on surfaces within the aquifer. The activities of Ra isotopes are similar to values from a sandy aquifers from a temperate region (Tricca et al. 2000). Measured 226Ra activities are much less than parent U activities and do not correlate. 228Ra/226Ra activity ratios are between 1.5 and 4, the supply ratio from the host sediments, and are dominated by a source in secular equilibrium. The Ra is dominantly adsorbed onto surfaces in exchange equilibrium with the local groundwater. Activities of 222Rn gas are similar to those found in other localities (50 to 450 dpm/kg). These values require emanation factions of up to 10% if the host rock is the direct source. However, the irreversible precipitation of 230Th and 232Th within the aquifer may provide a source for the 222Rn which does not require special recoil processes specific to Rn. In accordance to the model, we conclude that high CU in the vadose zone can be generated by high recoil and weathering rates in arid regions. The aquifer is distinct from the vadose zone with lower recoil fraction and weathering rates, although the apparent hydrologic disconnect between the two zones remains problematic. We acknowledge the invaluable help from the Navajo Tribal Utility Authority.

  3. Hydrological modelling over different scales on the edge of the permafrost zone: approaching model realism based on experimentalists' knowledge

    NASA Astrophysics Data System (ADS)

    Nesterova, Natalia; Makarieva, Olga; Lebedeva, Lyudmila

    2017-04-01

    Quantitative and qualitative experimentalists' data helps to advance both understanding of the runoff generation and modelling strategies. There is significant lack of such information for the dynamic and vulnerable cold regions. The aim of the study is to make use of historically collected experimental hydrological data for modelling poorly-gauged river basins on larger scales near the southern margin of the permafrost zone in Eastern Siberia. Experimental study site "Mogot" includes the Nelka river (30.8 km2) and its three tributaries with watersheds area from 2 to 5.8 km2. It is located in the upper elevated (500 - 1500 m a.s.l.) part of the Amur River basin. Mean annual temperature and precipitation are -7.5°C and 555 mm respectively. Top of the mountains with weak vegetation has well drained soil that prevents any water accumulation. Larch forest on the northern slopes has thick organic layer. It causes shallow active layer and relatively small subsurface water storage. Soil in the southern slopes has thinner organic layer and thaws up to 1.6 m depth. Flood plains are the wettest landscape with highest water storage capacity. Measured monthly evaporation varies from 9 to 100 mm through the year. Experimental data shows importance of air temperature and precipitation changes with the elevation. Their gradient was taken into account for hydrological simulations. Model parameterization was developed according to available quantitative and qualitative data in the Mogot station. The process-based hydrological Hydrograph model was used in the study. It explicitly describes hydrological processes in different permafrost environments. Flexibility of the Hydrograph model allows take advantage from the experimental data for model set-up. The model uses basic meteorological data as input. The level of model complexity is suitable for a remote, sparsely gauged region such as Southern Siberia as it allows for a priori assessment of the model parameters. Model simulation

  4. Wildfire and aspect effects on hydrologic states after the 2010 Fourmile Canyon Fire

    USGS Publications Warehouse

    Ebel, Brian A.

    2013-01-01

    Wildfire can change how soils take in, store, and release water. This study examined differences in how burned and unburned plots on north versus south-facing slope aspects respond to rainfall. The largest wildfire impacts were litter/duff combustion on burned north-facing slopes versus soil-water retention reduction on burned south-facing slopes.Wildfire is one of the most significant disturbances in mountainous landscapes, affecting water supply and ecologic function and setting the stage for natural hazards such as flash floods. The impacts of wildfire can affect the entire hydrologic cycle. Measurements of soil-water content and matric potential in the near surface (top 30 cm) captured the hydrologic state in both burned and unburned hillslopes during the first spring through fall period (1 June–1 Oct. 2011) after the 2010 Fourmile Canyon Fire near Boulder, CO. This time span included different hydrologic periods characterized by cyclonic frontal storms (low-intensity, long duration), convective storms (high-intensity, short duration), and dry periods. In mountainous environments, aspect can also control hydrologic states, so north- vs. south-facing slopes were compared. Wildfire tended to homogenize soil-water contents across aspects and with depth in the soil, yet it also may have introduced an aspect control on matric potential that was not observed in unburned soils. Post-wildfire changes in hydrologic state were observed in south-facing soils, probably reflecting decreased soil-water retention after wildfire. North-facing soils were impacted the most, in terms of hydrologic state, by the loss of water storage in the combusted litter–duff layer and forest canopy, which had provided a large “hydrologic buffering” capacity when unburned. Unsaturated zone measurements showed increased variability in hydrologic states and more rapid state transitions in wildfire-impacted soils. A simple, qualitative analysis suggested that the range of unsaturated-zone

  5. Evapotranspiration And Geochemical Controls On Groundwater Plumes At Arid Sites: Toward Innovative Alternate End-States For Uranium Processing And Tailings Facilities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Looney, Brian B.; Denham, Miles E.; Eddy-Dilek, Carol A.

    2014-01-08

    Management of legacy tailings/waste and groundwater contamination are ongoing at the former uranium milling site in Tuba City AZ. The tailings have been consolidated and effectively isolated using an engineered cover system. For the existing groundwater plume, a system of recovery wells extracts contaminated groundwater for treatment using an advanced distillation process. The ten years of pump and treat (P&T) operations have had minimal impact on the contaminant plume – primarily due to geochemical and hydrological limits. A flow net analysis demonstrates that groundwater contamination beneath the former processing site flows in the uppermost portion of the aquifer and exitsmore » the groundwater as the plume transits into and beneath a lower terrace in the landscape. The evaluation indicates that contaminated water will not reach Moenkopi Wash, a locally important stream. Instead, shallow groundwater in arid settings such as Tuba City is transferred into the vadose zone and atmosphere via evaporation, transpiration and diffuse seepage. The dissolved constituents are projected to precipitate and accumulate as minerals such as calcite and gypsum in the deep vadose zone (near the capillary fringe), around the roots of phreatophyte plants, and near seeps. The natural hydrologic and geochemical controls common in arid environments such as Tuba City work together to limit the size of the groundwater plume, to naturally attenuate and detoxify groundwater contaminants, and to reduce risks to humans, livestock and the environment. The technical evaluation supports an alternative beneficial reuse (“brownfield”) scenario for Tuba City. This alternative approach would have low risks, similar to the current P&T scenario, but would eliminate the energy and expense associated with the active treatment and convert the former uranium processing site into a resource for future employment of local citizens and ongoing benefit to the Native American Nations.« less

  6. Global root zone storage capacity from satellite-based evaporation data

    NASA Astrophysics Data System (ADS)

    Wang-Erlandsson, Lan; Bastiaanssen, Wim; Gao, Hongkai; Jägermeyr, Jonas; Senay, Gabriel; van Dijk, Albert; Guerschman, Juan; Keys, Patrick; Gordon, Line; Savenije, Hubert

    2016-04-01

    We present an "earth observation-based" method for estimating root zone storage capacity - a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data computed with independent energy balance equations to derive gridded root zone storage capacity at global scale. This approach does not require soil or vegetation information, is model independent, and is in principle scale-independent. In contrast to traditional look-up table approaches, our method captures the variability in root zone storage capacity within land cover type, including in rainforests where direct measurements of root depth otherwise are scarce. Implementing the estimated root zone storage capacity in the global hydrological model STEAM improved evaporation simulation overall, and in particular during the least evaporating months in sub-humid to humid regions with moderate to high seasonality. We find that evergreen forests are able to create a large storage to buffer for extreme droughts (with a return period of up to 60 years), in contrast to short vegetation and crops (which seem to adapt to a drought return period of about 2 years). The presented method to estimate root zone storage capacity eliminates the need for soils and rooting depth information, which could be a game-changer in global land surface modelling.

  7. Global root zone storage capacity from satellite-based evaporation

    NASA Astrophysics Data System (ADS)

    Wang-Erlandsson, Lan; Bastiaanssen, Wim G. M.; Gao, Hongkai; Jägermeyr, Jonas; Senay, Gabriel B.; van Dijk, Albert I. J. M.; Guerschman, Juan P.; Keys, Patrick W.; Gordon, Line J.; Savenije, Hubert H. G.

    2016-04-01

    This study presents an "Earth observation-based" method for estimating root zone storage capacity - a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data computed with independent energy balance equations to derive gridded root zone storage capacity at global scale. This approach does not require soil or vegetation information, is model independent, and is in principle scale independent. In contrast to a traditional look-up table approach, our method captures the variability in root zone storage capacity within land cover types, including in rainforests where direct measurements of root depths otherwise are scarce. Implementing the estimated root zone storage capacity in the global hydrological model STEAM (Simple Terrestrial Evaporation to Atmosphere Model) improved evaporation simulation overall, and in particular during the least evaporating months in sub-humid to humid regions with moderate to high seasonality. Our results suggest that several forest types are able to create a large storage to buffer for severe droughts (with a very long return period), in contrast to, for example, savannahs and woody savannahs (medium length return period), as well as grasslands, shrublands, and croplands (very short return period). The presented method to estimate root zone storage capacity eliminates the need for poor resolution soil and rooting depth data that form a limitation for achieving progress in the global land surface modelling community.

  8. Hydrology team

    NASA Technical Reports Server (NTRS)

    Ragan, R.

    1982-01-01

    General problems faced by hydrologists when using historical records, real time data, statistical analysis, and system simulation in providing quantitative information on the temporal and spatial distribution of water are related to the limitations of these data. Major problem areas requiring multispectral imaging-based research to improve hydrology models involve: evapotranspiration rates and soil moisture dynamics for large areas; the three dimensional characteristics of bodies of water; flooding in wetlands; snow water equivalents; runoff and sediment yield from ungaged watersheds; storm rainfall; fluorescence and polarization of water and its contained substances; discriminating between sediment and chlorophyll in water; role of barrier island dynamics in coastal zone processes; the relationship between remotely measured surface roughness and hydraulic roughness of land surfaces and stream networks; and modeling the runoff process.

  9. Hydrological disposition of flash flood and debris flows events in an Alpine watershed in Austria

    NASA Astrophysics Data System (ADS)

    Prenner, David; Kaitna, Roland; Mostbauer, Karin; Hrachowitz, Markus

    2017-04-01

    Debris flows and flash floods including intensive bedload transport represent severe hazards in the Alpine environment of Austria. For neither of these processes, explicit rainfall thresholds - even for specific regions - are available. This may be due to insufficient data on the temporal and spatial variation of precipitation, but probably also due to variations of the geomorphic and hydrological disposition of a watershed to produce such processes in the course of a rainfall event. In this contribution we investigate the importance of the hydrological system state for triggering debris flows and flash floods in the Ill/Suggadin watershed (500 km2), Austria, by analyzing the effects of dynamics in system state variables such as soil moisture, snow pack, or ground water level. The analysis is based on a semi-distributed conceptual rainfall-runoff model, spatially discretizing the watershed according to the available precipitation observations, elevation, topographic considerations and land cover. Input data are available from six weather stations on a daily basis ranging back to 1947. A Thiessen polygon decomposition results in six individual precipitation zones with a maximum area of about 130 km2. Elevation specific behavior of the quantities temperature and precipitation is covered through an elevation-resolved computation every 200 m. Spatial heterogeneity is considered by distinct hydrological response units for bare rock, forest, grassland, and riparian zone. To reduce numerical smearing on the hydrological results, the Implicit Euler scheme was used to discretize the balance equations. For model calibration we utilized runoff hydrographs, snow cover data as well as prior parameter and process constraints. The obtained hydrological output variables are linked to documented observed flash flood and debris flow events by means of a multivariate logistic regression. We present a summary about the daily hydrological disposition of experiencing a flash flood or

  10. Distributed nitrate transport and reaction routines (NTR) inside the mesoscale Hydrological Model (mHM) framework: Development and Application in the Selke catchment

    NASA Astrophysics Data System (ADS)

    Sinha, Sumit; Rode, Michael; Kumar, Rohini; Yang, Xiaoqiang; Samaniego, Luis; Borchardt, Dietrich

    2016-04-01

    Precise measurements of where, when and how much denitrification occurs on the basis of measurements alone persist to be vexing and intractable research problem at all spatial and temporal scales. As a result, models have become essential and vital tools for furthering our current understanding of the processes that control denitrification on catchment scale. Emplacement of Water Framework Directive (WFD) and continued efforts in improving water treatment facilities has resulted in alleviating the problems associated with point sources of pollution. However, the problem of eutrophication still persists and is primarily associated with the diffused sources of pollution originating from agricultural area. In this study, the nitrate transport and reaction (NTR) routines are developed inside the distributed mesoscale Hydrological Model (mHM www.ufz.de/mhm) which is a fully distributed hydrological model with a novel parameter regionalization scheme (Samaniego et al. 2010; Kumar et al. 2013) and has been applied to whole Europe (Rakovec et al. 2016) and numerous catchments worldwide. The aforementioned NTR model is applied to a mesoscale river basin, Selke (463 km2) located in central Germany. The NTR model takes in account the critical and pertinent processes like transformation in vadose zone, atmospheric deposition, plant uptake, instream denitrification and also simulates the process of manure and fertilizer application. Both streamflow routines and the NTR model are run on daily time steps. The split-sample approach was used for model calibration (1994-1999) and validation (2000-2004). Flow dynamics at three gauging stations located inside this catchment are successfully captured by the model with consistently high Nash-Sutcliffe Efficiency (NSE) of at least 0.8. Regarding nitrate estimates, the NSE values are greater than 0.7 for both validation and calibration periods. Finally, the NTR model is used for identifying the critical source areas (CSAs) that contribute

  11. Hillslope hydrologic connectivity controls riparian groundwater turnover: Implications of catchment structure for riparian buffering and stream water sources

    Treesearch

    Kelsey G. Jencso; Brian L. McGlynn; Michael N. Gooseff; Kenneth E. Bencala; Steven M. Wondzell

    2010-01-01

    Hydrologic connectivity between catchment upland and near stream areas is essential for the transmission of water, solutes, and nutrients to streams. However, our current understanding of the role of riparian zones in mediating landscape hydrologic connectivity and the catchment scale export of water and solutes is limited. We tested the relationship between the...

  12. Characterizing hydrology and the importance of ground-water discharge in natural and constructed wetlands

    USGS Publications Warehouse

    Hunt, Randall J.; Walker, John F.; Krabbenhoft, David P.

    1999-01-01

    Although considered the most important component for the establishment and persistence of wetlands, hydrology has been hard to characterize and linkages between hydrology and other environmental conditions are often poorly understood. In this work, methods for characterizing a wetland’s hydrology from hydrographs were developed, and the importance of ground water to the physical and geochemical conditions in the root zone was investigated. Detailed sampling of nearly continuous hydrographs showed that sites with greater ground-water discharge had higher water tables and more stable hydrographs. Subsampling of the continuous hydrograph failed to characterize the sites correctly, even though the wetland complex is located in a strong regional ground-water-discharge area. By comparing soil-moisture-potential measurements to the water-table hydrograph at one site, we noted that the amount of root-zone saturation was not necessarily driven by the water-table hydrograph but can be a result of other soil parameters (i.e., soil texture and associated capillary fringe). Ground-water discharge was not a significant determinant of maximum or average temperatures in the root zone. High ground-water discharge was associated with earliest date of thaw and shortest period of time that the root zone was frozen, however. Finally, the direction and magnitude of shallow ground-water flow was found to affect the migration and importance of a geochemical species. Areas of higher ground-water discharge had less downward penetration of CO2 generated in the root zone. In contrast, biotically derived CO2 was able to penetrate the deeper ground-water system in areas of ground-water recharge. Although ground-water flows are difficult to characterize, understanding these components is critical to the success of wetland restoration and creation efforts.

  13. Hydrological Process of Martian Surface in Hesperian epoch

    NASA Astrophysics Data System (ADS)

    Yamashiki, Y. A.; Sato, H.; Kuroki, R.; Miyamoto, H.; Hemmi, R.

    2017-12-01

    It is considered that the Mars in Noachian ecoch was much warmer temperature than current condition, with atmosphere and ocean supported by its magnetic actiity. Several valley which seems to be developed by ancient hydrological processes are obsered in Martian surface, is being considered to be built long time before. Some fluvial fun was formed during the following Hesperian epoch, which is considered as much cooler and drier than Noachian epoch. In this study, we applied Hydro-debris 2D model into Martian surface in Hesperian epoch in order to try develping surface vallay formation throughout hydrological processes. Sediment transport and associated small-scale debris-flow occurrence may be the key for valley formation, where might be the micro-habitable zone.

  14. Hanford Site 100-N Area In Situ Bioremediation of UPR-100-N-17, Deep Petroleum Unplanned Release - 13245

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saueressig, Daniel G.

    2013-07-01

    In 1965 and 1966, approximately 303 m{sup 3} of Number 2 diesel fuel leaked from a pipeline used to support reactor operations at the Hanford Site's N Reactor. N Reactor was Hanford's longest operating reactor and served as the world's first dual purpose reactor for military and power production needs. The Interim Action Record of Decision for the 100-N Area identified in situ bioremediation as the preferred alternative to remediate the deep vadose zone contaminated by this release. A pilot project supplied oxygen into the vadose zone to stimulate microbial activity in the soil. The project monitored respiration rates asmore » an indicator of active biodegradation. Based on pilot study results, a full-scale system is being constructed and installed to remediate the vadose zone contamination. (authors)« less

  15. A comparative study of two approaches to analyse groundwater recharge, travel times and nitrate storage distribution at a regional scale

    NASA Astrophysics Data System (ADS)

    Turkeltaub, T.; Ascott, M.; Gooddy, D.; Jia, X.; Shao, M.; Binley, A. M.

    2017-12-01

    Understanding deep percolation, travel time processes and nitrate storage in the unsaturated zone at a regional scale is crucial for sustainable management of many groundwater systems. Recently, global hydrological models have been developed to quantify the water balance at such scales and beyond. However, the coarse spatial resolution of the global hydrological models can be a limiting factor when analysing regional processes. This study compares simulations of water flow and nitrate storage based on regional and global scale approaches. The first approach was applied over the Loess Plateau of China (LPC) to investigate the water fluxes and nitrate storage and travel time to the LPC groundwater system. Using raster maps of climate variables, land use data and soil parameters enabled us to determine fluxes by employing Richards' equation and the advection - dispersion equation. These calculations were conducted for each cell on the raster map in a multiple 1-D column approach. In the second approach, vadose zone travel times and nitrate storage were estimated by coupling groundwater recharge (PCR-GLOBWB) and nitrate leaching (IMAGE) models with estimates of water table depth and unsaturated zone porosity. The simulation results of the two methods indicate similar spatial groundwater recharge, nitrate storage and travel time distribution. Intensive recharge rates are located mainly at the south central and south west parts of the aquifer's outcrops. Particularly low recharge rates were simulated in the top central area of the outcrops. However, there are significant discrepancies between the simulated absolute recharge values, which might be related to the coarse scale that is used in the PCR-GLOBWB model, leading to smoothing of the recharge estimations. Both models indicated large nitrate inventories in the south central and south west parts of the aquifer's outcrops and the shortest travel times in the vadose zone are in the south central and east parts of the

  16. Estimation of Hydraulic Properties Influencing Recharge and Contaminant Transport through Complex Vadose Zones by Analyzing Perched Water Data from the 1994 Large-Scale Infiltration Test at the Idaho National Laboratory

    NASA Astrophysics Data System (ADS)

    Creasey, K. M.; Nimmo, J. R.

    2014-12-01

    Layers of strong geologic contrast within the vadose zone can control recharge and contaminant transport to underlying aquifers. Above the eastern Snake River Plain Aquifer, multiple sedimentary interbeds are interspersed between fractured basalt. These interbeds have a variety of thicknesses and hydraulic properties, and can impede water flow, which allows perched water to collect on the interbeds. The Large-Scale Infiltration Test (LSIT) of 1994 at the Idaho National Laboratory (INL) maintained a circular pond, 200 meters in diameter, at a constant head for 20 days. Monitoring wells were arranged in circles of different radii around and within the pond, and perched water levels on a major sedimentary interbed, 55 meters below ground surface, were measured over time. Data showed that water formed a mound on the interbed before seeping through the interbed. Such behavior is consistent with a hypothesis of rapid flow through the fractured basalt being impeded by the sedimentary interbed. In 2014, the USGS, in cooperation with the U.S. Department of Energy, used a modified version of a Hantush (1967) equation to model the time-dependent perched water table heights from the LSIT as a function of radial distance from the pond center. The modeled volume change between time-steps and the known inflows to the pond were used in a mass balance to estimate the time-varying volume of water seeping through the interbed. This volume of water, the height of perched water, and the interbed thickness were used in Darcy's Law to estimate the effective saturated hydraulic conductivity of the impeding interbed. Results indicate a slightly higher effective conductivity than laboratory measurements of small core samples taken from the interbed, reflecting the presence of fractures or other heterogeneities that facilitate field-scale flow through the interbed. Applied to other locations, this method can improve estimates of recharge and contaminant transport to underlying aquifers.

  17. netherland hydrological modeling instrument

    NASA Astrophysics Data System (ADS)

    Hoogewoud, J. C.; de Lange, W. J.; Veldhuizen, A.; Prinsen, G.

    2012-04-01

    Netherlands Hydrological Modeling Instrument A decision support system for water basin management. J.C. Hoogewoud , W.J. de Lange ,A. Veldhuizen , G. Prinsen , The Netherlands Hydrological modeling Instrument (NHI) is the center point of a framework of models, to coherently model the hydrological system and the multitude of functions it supports. Dutch hydrological institutes Deltares, Alterra, Netherlands Environmental Assessment Agency, RWS Waterdienst, STOWA and Vewin are cooperating in enhancing the NHI for adequate decision support. The instrument is used by three different ministries involved in national water policy matters, for instance the WFD, drought management, manure policy and climate change issues. The basis of the modeling instrument is a state-of-the-art on-line coupling of the groundwater system (MODFLOW), the unsaturated zone (metaSWAP) and the surface water system (MOZART-DM). It brings together hydro(geo)logical processes from the column to the basin scale, ranging from 250x250m plots to the river Rhine and includes salt water flow. The NHI is validated with an eight year run (1998-2006) with dry and wet periods. For this run different parts of the hydrology have been compared with measurements. For instance, water demands in dry periods (e.g. for irrigation), discharges at outlets, groundwater levels and evaporation. A validation alone is not enough to get support from stakeholders. Involvement from stakeholders in the modeling process is needed. There fore to gain sufficient support and trust in the instrument on different (policy) levels a couple of actions have been taken: 1. a transparent evaluation of modeling-results has been set up 2. an extensive program is running to cooperate with regional waterboards and suppliers of drinking water in improving the NHI 3. sharing (hydrological) data via newly setup Modeling Database for local and national models 4. Enhancing the NHI with "local" information. The NHI is and has been used for many

  18. Internal architecture, permeability structure, and hydrologic significance of contrasting fault-zone types

    NASA Astrophysics Data System (ADS)

    Rawling, Geoffrey C.; Goodwin, Laurel B.; Wilson, John L.

    2001-01-01

    The Sand Hill fault is a steeply dipping, large-displacement normal fault that cuts poorly lithified Tertiary sediments of the Albuquerque basin, New Mexico, United States. The fault zone does not contain macroscopic fractures; the basic structural element is the deformation band. The fault core is composed of foliated clay flanked by structurally and lithologically heterogeneous mixed zones, in turn flanked by damage zones. Structures present within these fault-zone architectural elements are different from those in brittle faults formed in lithified sedimentary and crystalline rocks that do contain fractures. These differences are reflected in the permeability structure of the Sand Hill fault. Equivalent permeability calculations indicate that large-displacement faults in poorly lithified sediments have little potential to act as vertical-flow conduits and have a much greater effect on horizontal flow than faults with fractures.

  19. Network analysis applications in hydrology

    NASA Astrophysics Data System (ADS)

    Price, Katie

    2017-04-01

    Applied network theory has seen pronounced expansion in recent years, in fields such as epidemiology, computer science, and sociology. Concurrent development of analytical methods and frameworks has increased possibilities and tools available to researchers seeking to apply network theory to a variety of problems. While water and nutrient fluxes through stream systems clearly demonstrate a directional network structure, the hydrological applications of network theory remain under­explored. This presentation covers a review of network applications in hydrology, followed by an overview of promising network analytical tools that potentially offer new insights into conceptual modeling of hydrologic systems, identifying behavioral transition zones in stream networks and thresholds of dynamical system response. Network applications were tested along an urbanization gradient in Atlanta, Georgia, USA. Peachtree Creek and Proctor Creek. Peachtree Creek contains a nest of five long­term USGS streamflow and water quality gages, allowing network application of long­term flow statistics. The watershed spans a range of suburban and heavily urbanized conditions. Summary flow statistics and water quality metrics were analyzed using a suite of network analysis techniques, to test the conceptual modeling and predictive potential of the methodologies. Storm events and low flow dynamics during Summer 2016 were analyzed using multiple network approaches, with an emphasis on tomogravity methods. Results indicate that network theory approaches offer novel perspectives for understanding long­ term and event­based hydrological data. Key future directions for network applications include 1) optimizing data collection, 2) identifying "hotspots" of contaminant and overland flow influx to stream systems, 3) defining process domains, and 4) analyzing dynamic connectivity of various system components, including groundwater­surface water interactions.

  20. Geothermal evolution of an intruded dike in the rift zone of Kilauea volcano, Hawaii from VLF and self-potential measurements

    NASA Astrophysics Data System (ADS)

    Davis, Paul M.

    2015-09-01

    Self-potential (SP) and VLF measurements were made in 1973, 1975, 1995, 1997 and 2012 across a basaltic dike that intruded into the Koae fault zone of Kilauea volcano, Hawaii in May 1973. The SP anomaly remained strong throughout. In 2012 it was at about 60% of the strength it had in 1973. In contrast, the VLF anomaly, though diminished, was still observable in 1995/1997, but by 2012 it had disappeared. A hydrothermal dike model, with parameters calibrated by modeling the solidification of Kilauea Iki lava lake, is used to calculate temperatures and conductivity variation. Following Jaeger's (1957) method, we find that the time in years for a dike of width W (m) to solidify is 0.0075W2. Thus, a 1 m dike solidifies within the first few days, and after 39 years is only tens of degrees above ambient. Given the orders of magnitude difference between the conductivities of wet and dry basalt, we infer, that after solidification, the VLF anomalies were caused by induction in a localized veil of wet, hot basalt enveloping the dike, that was generated initially by condensation of steam, and subsequently by condensation of evaporated water as temperatures reduced. The conductivity anomaly persisted until the mid-nineties. By 2012, temperatures and condensation were too small for a VLF signal. The persistent SP anomaly is attributed to localized fluid disruption, with evaporation mainly at the water table and in the vadose zone. Streaming potentials are associated with evaporative circulation in the vadose zone. Next to the dike a positive potential is generated by upward flow of moisture-laden air, with a smaller negative potential on its flanks from downward infiltrating rainwater. The analysis indicates that the combination of SP and VLF measurements can characterize the evolving geothermal regime of intrusions above the water table.

  1. An Isotopic view of water and nitrogen transport through the ...

    EPA Pesticide Factsheets

    Groundwater nitrate contamination affects thousands of households in Oregon’s southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 due to nitrate levels in the groundwater exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen inputs to the GWMA comes from agricultural nitrogen use, and thus efforts to reduce N inputs to groundwater are focused upon improving N management. However, the effectiveness of these improvements on groundwater quality is unclear because of the complexity of nutrient transport through the vadose zone and long groundwater residence times. Our objective was to focus on vadose zone transport and understand the dynamics and timing of N and water movement below the rooting zone in relation to N management and water inputs. Stable isotopes are a powerful tool for tracking water movement, and understanding nitrogen transformations within the vadose zone. In partnership with local farmers, and state agencies, we established lysimeters and groundwater wells in multiple agricultural fields in the GWMA, and have monitored nitrate, nitrate isotopes, and water isotopes weekly for multiple years. Our results indicate that vadose zone transport is highly complex, and the residence time of water collected in lysimeters was much longer than expected. While input precipitation water isotopes were highly variab

  2. An Isotopic view of water and nitrogen transport through the ...

    EPA Pesticide Factsheets

    Background/Question/MethodsGroundwater nitrate contamination affects thousands of households in Oregon's southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 due to nitrate levels in the groundwater exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen inputs to the GWMA comes from agricultural nitrogen use, and thus efforts to reduce N inputs to groundwater are focused upon improving N management. However, the effectiveness of these improvements on groundwater quality is unclear because of the complexity of nutrient transport through the vadose zone and long groundwater residence times. Our objective was to focus on vadose zone transport and understand the dynamics and timing of N and water movement below the rooting zone in relation to N management and water inputs. Stable isotopes are a powerful tool for tracking water movement, and understanding nitrogen transformations within the vadose zone. In partnership with local farmers, and state agencies, we established lysimeters and groundwater wells in multiple agricultural fields in the GWMA, and have monitored nitrate, nitrate isotopes, and water isotopes weekly for multiple years Results/ConclusionsOur results indicate that vadose zone transport is highly complex, and the residence time of water collected in lysimeters was much longer than expected. While input precipitatio

  3. Geochemical response to hydrologic change along land-sea interfaces

    NASA Astrophysics Data System (ADS)

    Michael, H. A.; Yu, X.; LeMonte, J. J.; Sparks, D. L.; Kim, K. H.; Heiss, J.; Ullman, W. J.; Guimond, J. A.; Seyfferth, A.

    2016-12-01

    Coastal groundwater-surface water interfaces are hotspots of geochemical activity, where reactants contributed by different sources come in contact. Reactions that occur along these land-sea boundaries have important effects on fluxes and cycling of carbon, nutrients, and contaminants. Hydrologic perturbations can alter interactions by promoting mixing, changing redox state, and altering subsurface residence times during which reactions may occur. We present examples from field and modeling investigations along the Delaware coastline that illustrate the impacts of hydrologic fluctuations on geochemical conditions and fluxes in different coastal environments. Along the highly populated Wilmington coastline, soils are contaminated with heavy metals from legacy industrial practices. We show with continuous redox monitoring and sampling over tidal to seasonal timescales that arsenic is mobilized and immobilized in response to hydrologic change. Along a beach, modeling and long-term monitoring show the influence of tidal to seasonal changes in the mixing zone between discharging fresh groundwater and seawater in the intertidal beach aquifer and associated impacts on biogeochemical reactivity and denitrification. In a saltmarsh, hydrologic changes alter carbon dynamics, with implications for the discharge of dissolved organic carbon to the ocean and export of carbon dioxide and methane to the atmosphere. Understanding the impacts of hydrologic changes on both long and short timescales is essential for improving our ability to predict the global biogeochemical impacts of a changing climate.

  4. Vadose Zone as a Potential Carbon Source: a Look at Seasonal Spikes in Hyporheic Zone pCO2

    NASA Astrophysics Data System (ADS)

    Brandes, J.

    2016-12-01

    Connections between soils, terrestrial streams and the atmosphere are not yet thoroughly understood as contributing factors to the global carbon budget. We collected data from an undisturbed soil column adjacent to a small stream in a forested watershed in the H. J. Andrews Experimental Forest in the Western Cascades of Oregon in the United States. Our data includes: CO2 (ppm); temperature (oC); depth below water table (m); and soil moisture (cm3/cm3) and spans approximately one year. We are analyzing the data using the gradient method and have observed distinct seasonal patterns which may support previous research describing temporal processes. We can expect to see changing soil moisture characteristics which may promote either vertical CO2 diffusion out of the surface or vertical/lateral advection into subsurface flow. We hypothesize that there is flushing of soil CO2 into the hyporheic zone during precipitation events following soil CO2 buildup.

  5. Disturbance Hydrology in the Tropics: The Galápagos Islands as a Case Study

    NASA Astrophysics Data System (ADS)

    Riveros-Iregui, D. A.; Schmitt, S.; Percy, M.; Hu, J.; Singha, K.; Mirus, B. B.

    2015-12-01

    Tropical Latin America has shown the largest acceleration in land use change in recent decades. It is well established that changes in vegetation cover can lead to changes in water demand, evapotranspiration, and eventually soil textural characteristics. Given the projected changes in the intensity and distribution of rainfall in tropical regions in the coming decades, it is critical to characterize how changes in land use change across different climatic zones may fundamentally reshape water availability and storage, soil composition and associated hydraulic properties, and overall watershed hydrologic behavior. This study evaluates the role of anthropogenic disturbance on hydrological processes across different climatic zones in the tropics. We focus specifically on San Cristobal Island, the second most populated island of the iconic Galapagos archipelago, which is currently undergoing severe anthropogenic transformation. The island contains a spectrum of climates, ranging from very humid to arid, and has seen a dramatic increase in tourism and an increase in the permanent population of greater than 1000% in the last 40 years. Over 70% of the landscape of San Cristobal has been altered by land use change and invasive species. Our study identifies the complex interactions among hydrological, geological, economic, and social variables that tropical island systems will face in the years ahead, and the role and effects of a dynamic hydrologic cycle across multiple scales.

  6. Hydrogeology and Hydrologic Landscape Regions of Nevada

    USGS Publications Warehouse

    Maurer, Douglas K.; Lopes, Thomas J.; Medina, Rose L.; Smith, J. LaRue

    2004-01-01

    units consist of: (1) carbonate rocks, Quaternary to Tertiary age; (2) basaltic, (3) rhyolitic, and (4) andesitic volcanic flows; (5) volcanic breccias, tuffs, and volcanic rocks older than Tertiary age; (6) intrusive and metamorphic rocks; (7) consolidated and semi-consolidated tuffaceous rocks and sediments; and (8) clastic rocks consisting of sandstone and siltstone. Unconsolidated sediments are subdivided into four hydrogeologic units on the basis of flow regime, topographic slope, and mapped stream channels. The four units are (1) alluvial slopes, (2) valley floors, (3) fluvial deposits, and (4) playas. Soil permeability was grouped into five descriptive categories ranging from very high to very low, which generally correspond to mapped geomorphic features such as playas and alluvial slopes. In general, soil permeability is low to moderate in northern, northeastern, and eastern Nevada and high to very high in western, southwestern, and southern Nevada. Within a particular basin, soil permeability decreases downslope from the bedrock contact. The type of parent rock, climate, and streamflow velocities are factors that likely cause these spatial patterns. Faults in unconsolidated sediments usually are barriers to ground-water flow. In consolidated rocks, permeability and ground-water flow is reduced in directions normal to the fault zone and increased in directions parallel to the fault zone. With time, mineral precipitation may seal fractures in consolidated rocks, reducing the permeability. However, continued movement along the fault may form new fractures, resulting in a fault alternating from a zone of preferred flow to a flow barrier during geologic time. The effect of faults on ground-water flow at a particular location is difficult to determine without a site- specific investigation. Hydrologic landscape regions were delineated by overlaying a grid of 100-foot (30-meter) cells over the State, estimating the value of five variables for each cell, an

  7. Part 1: Vadose-zone column studies of toluene (enhanced bioremediation) in a shallow unconfined aquifer

    USGS Publications Warehouse

    Tindall, J.A.; Friedel, M.J.; Szmajter, R.J.; Cuffin, S.M.

    2005-01-01

    The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H2O2) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II). For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added. As measured by CO2 respiration, the initial benefits for aerobic organisms from the O2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment. The O2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage

  8. The Critical Zone: A Necessary Framework for Understanding Surface Earth Processes

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.

    2016-12-01

    One definition of the critical zone is: the thin veneer of Earth that extends from the top of the vegetation to the base of weathered bedrock. With this definition we can envision the critical zone as a distinct entity with a well-defined top and a fairly well-defined bottom that is distributed across terrestrial earth landscapes. It is a zone of co-evolving processes and, importantly, much of this zone is well below the soil mantle (and commonly more than 10 times thicker than the soil). Weathering advance into fresh bedrock creates a hydrologically-conductive skin that mediates runoff and solute chemistry, stores water used by vegetation, releases water as baseflow to streams, influences soil production and hillslope evolution, and feeds gasses to the atmosphere. Especially in seasonally dry environments, rock moisture in the critical zone, i.e. moisture that is exchangeable and potentially mobile in the matrix and fractures of the bedrock, can be a significant source of water to plants and is a previously unrecognized large component of the water budget that matters to climate models. First observations on the systematic variation of the critical zone across hillslopes have led to four distinct theories representing four distinct processes for what controls the depth to fresh bedrock (and thus the thickness of this zone across a hillslope). These theories are motivating geophysical surveys, deep drilling, and other actions to parameterize and explore the power of these models. Studies at the NSF-supported Critical Zone Observatories have taught us that the critical zone is an entity and that enduring field studies reveal key processes. A challenge we now face is how to include this emerging understanding of the critical zone into models of reactive transport, hydrologic processes and water supply, critical zone structure, landscape evolution, and climate.

  9. The role of hillslope hydrology in controlling nutrient loss

    Treesearch

    Willem J. van Verseveld; Jeffrey J. McDonnell; Kate Lajtha

    2009-01-01

    Hydrological controls on DOC and N transport at the catchment scale were studied for five storm events from the fall of 2004 through the spring of 2005 in WS10, H,J, Andrews Experimental Forest in the western Cascade Mountains of Oregon, This catchment is devoid of any riparian zone and characterized by hillslopes that issue directly into the stream. This enabled us to...

  10. Characterizing the proposed geologic repository for high-level radioactive waste at Yucca Mountain, Nevada--hydrology and geochemistry

    USGS Publications Warehouse

    Stuckless, John S.; Levich, Robert A.

    2012-01-01

    This hydrology and geochemistry volume is a companion volume to the 2007 Geological Society of America Memoir 199, The Geology and Climatology of Yucca Mountain and Vicinity, Southern Nevada and California, edited by Stuckless and Levich. The work in both volumes was originally reported in the U.S. Department of Energy regulatory document Yucca Mountain Site Description, for the site characterization study of Yucca Mountain, Nevada, as the proposed U.S. geologic repository for high-level radioactive waste. The selection of Yucca Mountain resulted from a nationwide search and numerous committee studies during a period of more than 40 yr. The waste, largely from commercial nuclear power reactors and the government's nuclear weapons programs, is characterized by intense penetrating radiation and high heat production, and, therefore, it must be isolated from the biosphere for tens of thousands of years. The extensive, unique, and often innovative geoscience investigations conducted at Yucca Mountain for more than 20 yr make it one of the most thoroughly studied geologic features on Earth. The results of these investigations contribute extensive knowledge to the hydrologic and geochemical aspects of radioactive waste disposal in the unsaturated zone. The science, analyses, and interpretations are important not only to Yucca Mountain, but also to the assessment of other sites or alternative processes that may be considered for waste disposal in the future. Groundwater conditions, processes, and geochemistry, especially in combination with the heat from radionuclide decay, are integral to the ability of a repository to isolate waste. Hydrology and geochemistry are discussed here in chapters on unsaturated zone hydrology, saturated zone hydrology, paleohydrology, hydrochemistry, radionuclide transport, and thermally driven coupled processes affecting long-term waste isolation. This introductory chapter reviews some of the reasons for choosing to study Yucca Mountain as a

  11. Characterizing the proposed geologic repository for high-level radioactive waste at Yucca Mountain, Nevada: hydrology and geochemistry

    USGS Publications Warehouse

    Stuckless, John S.; Levich, Robert A.

    2012-01-01

    This hydrology and geochemistry volume is a companion volume to the 2007 Geological Society of America Memoir 199, The Geology and Climatology of Yucca Mountain and Vicinity, Southern Nevada and California, edited by Stuckless and Levich. The work in both volumes was originally reported in the U.S. Department of Energy regulatory document Yucca Mountain Site Description, for the site characterization study of Yucca Mountain, Nevada, as the proposed U.S. geologic repository for high-level radioactive waste. The selection of Yucca Mountain resulted from a nationwide search and numerous committee studies during a period of more than 40 yr. The waste, largely from commercial nuclear power reactors and the government's nuclear weapons programs, is characterized by intense penetrating radiation and high heat production, and, therefore, it must be isolated from the biosphere for tens of thousands of years. The extensive, unique, and often innovative geoscience investigations conducted at Yucca Mountain for more than 20 yr make it one of the most thoroughly studied geologic features on Earth. The results of these investigations contribute extensive knowledge to the hydrologic and geochemical aspects of radioactive waste disposal in the unsaturated zone. The science, analyses, and interpretations are important not only to Yucca Mountain, but also to the assessment of other sites or alternative processes that may be considered for waste disposal in the future. Groundwater conditions, processes, and geochemistry, especially in combination with the heat from radionuclide decay, are integral to the ability of a repository to isolate waste. Hydrology and geochemistry are discussed here in chapters on unsaturated zone hydrology, saturated zone hydrology, paleohydrology, hydrochemistry, radionuclide transport, and thermally driven coupled processes affecting long-term waste isolation. This introductory chapter reviews some of the reasons for choosing to study Yucca Mountain as a

  12. Revising Hydrology of a Land Surface Model

    NASA Astrophysics Data System (ADS)

    Le Vine, Nataliya; Butler, Adrian; McIntyre, Neil; Jackson, Christopher

    2015-04-01

    Land Surface Models (LSMs) are key elements in guiding adaptation to the changing water cycle and the starting points to develop a global hyper-resolution model of the terrestrial water, energy and biogeochemical cycles. However, before this potential is realised, there are some fundamental limitations of LSMs related to how meaningfully hydrological fluxes and stores are represented. An important limitation is the simplistic or non-existent representation of the deep subsurface in LSMs; and another is the lack of connection of LSM parameterisations to relevant hydrological information. In this context, the paper uses a case study of the JULES (Joint UK Land Environmental Simulator) LSM applied to the Kennet region in Southern England. The paper explores the assumptions behind JULES hydrology, adapts the model structure and optimises the coupling with the ZOOMQ3D regional groundwater model. The analysis illustrates how three types of information can be used to improve the model's hydrology: a) observations, b) regionalized information, and c) information from an independent physics-based model. It is found that: 1) coupling to the groundwater model allows realistic simulation of streamflows; 2) a simple dynamic lower boundary improves upon JULES' stationary unit gradient condition; 3) a 1D vertical flow in the unsaturated zone is sufficient; however there is benefit in introducing a simple dual soil moisture retention curve; 4) regionalized information can be used to describe soil spatial heterogeneity. It is concluded that relatively simple refinements to the hydrology of JULES and its parameterisation method can provide a substantial step forward in realising its potential as a high-resolution multi-purpose model.

  13. Changes in dissolved organic matter quality in a peatland and forest headwater stream as a function of seasonality and hydrologic conditions

    NASA Astrophysics Data System (ADS)

    Broder, Tanja; Knorr, Klaus-Holger; Biester, Harald

    2017-04-01

    Peatlands and peaty riparian zones are major sources of dissolved organic matter (DOM), but are poorly understood in terms of export dynamics and controls thereof. Thereby quality of DOM affects function and behavior of DOM in aquatic ecosystems, but DOM quality can also help to track DOM sources and their export dynamics under specific hydrologic preconditions. The objective of this study was to elucidate controls on temporal variability in DOM concentration and quality in stream water draining a bog and a forested peaty riparian zone, particularly considering drought and storm flow events. DOM quality was monitored using spectrofluorometric indices for aromaticity (SUVA254), apparent molecular size (SR) and precursor organic material (FI), as well as PARAFAC modeling of excitation emission matrices (EEMs). Indices for DOM quality exhibited major changes due to different hydrologic conditions, but patterns were also dependent on season. Stream water at the forested site with mineral, peaty soils generally exhibited higher variability in DOM concentrations and quality compared to the outflow of an ombrotrophic bog, where DOM was less susceptible to changes in hydrologic conditions. During snowmelt and spring events, near-surface protein-like DOM pools were exported. A microbial DOM fraction originating from groundwater and deep peat layers was increasing during drought, while a strongly microbially altered DOM fraction was also exported by discharge events with dry preconditions at the forested site. This might be due to accelerated microbial activity in the peaty riparian zone of the forested site under these preconditions. Our study demonstrated that DOM export dynamics are not only a passive mixing of different hydrological sources, but monitoring studies have to consider that DOM quality depends on hydrologic preconditions and season. Moreover, the forested peaty riparian zone generated the most variability in headwater DOM quantity and quality, as could be

  14. Hydrological and water quality processes simulation by the integrated MOHID model

    NASA Astrophysics Data System (ADS)

    Epelde, Ane; Antiguedad, Iñaki; Brito, David; Eduardo, Jauch; Neves, Ramiro; Sauvage, Sabine; Sánchez-Pérez, José Miguel

    2016-04-01

    Different modelling approaches have been used in recent decades to study the water quality degradation caused by non-point source pollution. In this study, the MOHID fully distributed and physics-based model has been employed to simulate hydrological processes and nitrogen dynamics in a nitrate vulnerable zone: the Alegria River watershed (Basque Country, Northern Spain). The results of this study indicate that the MOHID code is suitable for hydrological processes simulation at the watershed scale, as the model shows satisfactory performance at simulating the discharge (with NSE: 0.74 and 0.76 during calibration and validation periods, respectively). The agronomical component of the code, allowed the simulation of agricultural practices, which lead to adequate crop yield simulation in the model. Furthermore, the nitrogen exportation also shows satisfactory performance (with NSE: 0.64 and 0.69 during calibration and validation periods, respectively). While the lack of field measurements do not allow to evaluate the nutrient cycling processes in depth, it has been observed that the MOHID model simulates the annual denitrification according to general ranges established for agricultural watersheds (in this study, 9 kg N ha-1 year-1). In addition, the model has simulated coherently the spatial distribution of the denitrification process, which is directly linked to the simulated hydrological conditions. Thus, the model has localized the highest rates nearby the discharge zone of the aquifer and also where the aquifer thickness is low. These results evidence the strength of this model to simulate watershed scale hydrological processes as well as the crop production and the agricultural activity derived water quality degradation (considering both nutrient exportation and nutrient cycling processes).

  15. Factors Effecting the Fate and Transport of CL-20 in the Vadose Zone and Groundwater: Final Report 2002 - 2004 SERDP Project CP-1255

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szecsody, James E.; Riley, Robert G.; Devary, Brooks J.

    2005-06-01

    This SERDP-funded project was initiated to investigate the fate of CL-20 in the subsurface environment, with a focus on identification and quantification of geochemical and microbial reactions of CL-20. CL-20 can be released to the surface and subsurface terrestrial environment by: a) manufacturing processes, b) munition storage, and c) use with low order detonation or unexploded ordnance. The risk of far-field subsurface migration was assessed through labora-tory experiments with a variety of sediments and subsurface materials to quantify processes that control CL-20 sorption-limited migration and degradation. Results of this study show that CL-20 will exhibit differing behavior in the subsurfacemore » terrestrial environment: 1. CL-20 on the sediment surface will photodegrade and interact with plants/animals (described in other SERDP projects CU 1254, 1256). CL-20 will exhibit greater sorption in humid sediments to organic matter. Transport will be solubility limited (i.e., low CL-20 aqueous solubility). 2. CL-20 infiltration into soils (<2 m) from spills will be subject to sorption to soil organic matter (if present), and low to high biodegradation rates (weeks to years) depending on the microbial population (greater in humid environment). 3. CL-20 in the vadose zone (>2 m) will be, in most cases, subject to low sorption and low degradation rates, so would persist in the subsurface environment and be at risk for deep migration. Low water content in arid regions will result in a decrease in both sorption and the degradation rate. Measured degradation rates in unsaturated sediments of years would result in significant subsurface migration distances. 4. CL-20 in groundwater will be subject to some sorption but likely very slow degradation rates. CL-20 sorption will be greater than RDX. Most CL-20 degradation will be abiotic (ferrous iron and other transition metals), because most deep subsurface systems have extremely low natural microbial populations

  16. Hydrologic and geologic characteristics of the Yucca Mountain site relevant to the performance of a potential repository

    USGS Publications Warehouse

    Levich, R.A.; Linden, R.M.; Patterson, R.L.; Stuckless, J.S.

    2000-01-01

    Yucca Mountain, located ~100 mi northwest of Las Vegas, Nevada, has been designated by Congress as a site to be characterized for a potential mined geologic repository for high-level radioactive waste. This field trip will examine the regional geologic and hydrologic setting for Yucca Mountain, as well as specific results of the site characterization program. The first day focuses on the regional setting with emphasis on current and paleo hydrology, which are both of critical concern for predicting future performance of a potential repository. Morning stops will be southern Nevada and afternoon stops will be in Death Valley. The second day will be spent at Yucca Mountain. The field trip will visit the underground testing sites in the "Exploratory Studies Facility" and the "Busted Butte Unsaturated Zone Transport Field Test" plus several surface-based testing sites. Much of the work at the site has concentrated on studies of the unsaturated zone, an element of the hydrologic system that historically has received little attention. Discussions during the second day will compromise selected topics of Yucca Mountain geology, hydrology and geochemistry and will include the probabilistic volcanic hazard analysis and the seismicity and seismic hazard in the Yucca Mountain area. Evening discussions will address modeling of regional groundwater flow, the results of recent hydrologic studies by the Nye County Nuclear Waste Program Office, and the relationship of the geology and hydrology of Yucca Mountain to the performance of a potential repository. Day 3 will examine the geologic framework and hydrology of the Pahute Mesa-Oasis Valley Groundwater Basin and then will continue to Reno via Hawthorne, Nevada and the Walker Lake area.

  17. Futuristic isotope hydrology in the Gulf region

    NASA Astrophysics Data System (ADS)

    Saravana Kumar, U.; Hadi, Khaled

    2018-03-01

    The Gulf region is one of the most water-stressed parts in the world. Water in the region is very scarce, shortage of supply and lacking of renewable water resources, while the demand for water is growing day by day. It is thus essential to implement modern approaches and technologies in addressing water-related issues. In this context, isotope hydrology will provide invaluable aid. Some of the most important areas of futuristic applications of isotope hydrology include evaluation of aquifer recharge, storage and their recovery system, understanding of dynamic changes due to long-term exploitation of the groundwater, development and management of shared groundwater aquifers, fresh groundwater discharge along the Arabian Gulf, identification and quantification of hydrocarbon contamination in groundwater; soil moisture and solute movement in unsaturated zone, paleoclimate reconstruction, etc. Literature survey suggests, in general, not many isotope studies on the above have been reported.

  18. Development of hydrologic landscape regions for classifying hydrologic permanace and hydrological-ecological interactions

    EPA Science Inventory

    In a 2001 paper, Winter proposed the concept of the hydrologic landscape unit as a fundamental unit composed of an upland and lowland separated by a steeper slope. Winter suggested that this concept could be useful for hydrologic research, data analysis, and comparing hydrologic...

  19. Adaptable Web Modules to Stimulate Active Learning in Engineering Hydrology using Data and Model Simulations of Three Regional Hydrologic Systems

    NASA Astrophysics Data System (ADS)

    Habib, E. H.; Tarboton, D. G.; Lall, U.; Bodin, M.; Rahill-Marier, B.; Chimmula, S.; Meselhe, E. A.; Ali, A.; Williams, D.; Ma, Y.

    2013-12-01

    The hydrologic community has long recognized the need for broad reform in hydrologic education. A paradigm shift is critically sought in undergraduate hydrology and water resource education by adopting context-rich, student-centered, and active learning strategies. Hydrologists currently deal with intricate issues rooted in complex natural ecosystems containing a multitude of interconnected processes. Advances in the multi-disciplinary field include observational settings such as Critical Zone and Water, Sustainability and Climate Observatories, Hydrologic Information Systems, instrumentation and modeling methods. These research advances theory and practices call for similar efforts and improvements in hydrologic education. The typical, text-book based approach in hydrologic education has focused on specific applications and/or unit processes associated with the hydrologic cycle with idealizations, rather than the contextual relations in the physical processes and the spatial and temporal dynamics connecting climate and ecosystems. An appreciation of the natural variability of these processes will lead to graduates with the ability to develop independent learning skills and understanding. This appreciation cannot be gained in curricula where field components such as observational and experimental data are deficient. These types of data are also critical when using simulation models to create environments that support this type of learning. Additional sources of observations in conjunction with models and field data are key to students understanding of the challenges associated with using models to represent such complex systems. Recent advances in scientific visualization and web-based technologies provide new opportunities for the development of active learning techniques utilizing ongoing research. The overall goal of the current study is to develop visual, case-based, data and simulation driven learning experiences to instructors and students through a web

  20. The Effect of Riparian Zones in Structuring Small Mammal Communities in the Southern Appalachians

    Treesearch

    Joshua Laerm; Michael A. Menzel; Dorothy J. Wolf; James R. Welch

    1997-01-01

    Riparian zones have been shown to be important in structuring vertebrate communities and in maintaining biodiversity. We examined the role of riparian zones in structuring small mammal communities in a southern Appalachian watershed at Coweeta Hydrological Laboratory, Macon County, North Carolina. We established pitfall and live-trap grids in three replicates each of...

  1. The Impact of Urban Development in the Arid Zone and its Management.

    NASA Astrophysics Data System (ADS)

    Gat, J. R.

    2002-05-01

    From the experience in humid and semi-arid settings, the immediate impact of urbanization on the hydrological system is the interference with the natural direct infiltration pathways, resulting in a decrease of groundwater recharge as well as the possibility of surface flooding. In contrast, in the arid environment the limited rain amounts and number of rain events makes the contribution of rain of marginal importance in the city's water balance. The major impact of urbanization in the arid zone is the continuous excess of discharge of treated or untreated sewage or water spills, originating from the import of water to the city's water supply. Their effect can be advantageous if properly channeled. On the other hand, the polluting potential of these water excesses as well as the possibility of mobilizing stored salinity in the downstream locations is of concern, if the natural drainage network and its remediation capacity becomes overloaded. Further, since the arid zone hydrological cycle depends naturally on a discontinuous and episodal groundwater recharge pattern, the new situation requires the re-assessment of the eco-hydrological patterns in the downstream location.

  2. Deterministic influences exceed dispersal effects on hydrologically-connected microbiomes: Deterministic assembly of hyporheic microbiomes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Graham, Emily B.; Crump, Alex R.; Resch, Charles T.

    2017-03-28

    Subsurface zones of groundwater and surface water mixing (hyporheic zones) are regions of enhanced rates of biogeochemical cycling, yet ecological processes governing hyporheic microbiome composition and function through space and time remain unknown. We sampled attached and planktonic microbiomes in the Columbia River hyporheic zone across seasonal hydrologic change, and employed statistical null models to infer mechanisms generating temporal changes in microbiomes within three hydrologically-connected, physicochemically-distinct geographic zones (inland, nearshore, river). We reveal that microbiomes remain dissimilar through time across all zones and habitat types (attached vs. planktonic) and that deterministic assembly processes regulate microbiome composition in all data subsets.more » The consistent presence of heterotrophic taxa and members of the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum nonetheless suggests common selective pressures for physiologies represented in these groups. Further, co-occurrence networks were used to provide insight into taxa most affected by deterministic assembly processes. We identified network clusters to represent groups of organisms that correlated with seasonal and physicochemical change. Extended network analyses identified keystone taxa within each cluster that we propose are central in microbiome composition and function. Finally, the abundance of one network cluster of nearshore organisms exhibited a seasonal shift from heterotrophic to autotrophic metabolisms and correlated with microbial metabolism, possibly indicating an ecological role for these organisms as foundational species in driving biogeochemical reactions within the hyporheic zone. Taken together, our research demonstrates a predominant role for deterministic assembly across highly-connected environments and provides insight into niche dynamics associated with seasonal changes in hyporheic microbiome composition and metabolism.« less

  3. Bistability of mangrove forests and competition with freshwater plants

    USGS Publications Warehouse

    Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.

    2015-01-01

    Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

  4. Enhanced Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam for Metal, Radionuclide, and NAPL Remediation

    NASA Astrophysics Data System (ADS)

    Zhong, L.; Szecsody, J.; Li, X.; Oostrom, M.; Truex, M.

    2010-12-01

    In many contamination sites, removal of contaminants by any active remediation efforts is not practical due to the high cost and technological limitations. Alternatively, in situ remediation is expected to be the most important remediation strategy. Delivery of reactive amendment to the contamination zone is essential for the reactions between the contaminants and remedial amendments to proceed in situ. It is a challenge to effectively deliver remedial amendment to the subsurface contamination source areas in both aquifer and vadose zone. In aquifer, heterogeneity induces fluid bypassing the low-permeability zones, resulting in certain contaminated areas inaccessible to the remedial amendment delivered by water injection, thus inhibiting the success of remedial operations. In vadose zone in situ remediation, conventional solution injection and infiltration for amendment delivery have difficulties to achieve successful lateral spreading and uniform distribution of the reactive media. These approaches also tend to displace highly mobile metal and radionuclide contaminants such as hexavalent chromium [Cr(VI)] and technetium (Tc-99), causing spreading of contaminations. Shear thinning fluid and aqueous foam can be applied to enhance the amendment delivery and improve in situ subsurface remediation efficiency under aquifer and vadose zone conditions, respectively. Column and 2-D flow cell experiments were conducted to demonstrate the enhanced delivery and improved remediation achieved by the application of shear thinning fluid and foam injection at the laboratory scale. Solutions of biopolymer xanthan gum were used as the shear thinning delivering fluids. Surfactant sodium lauryl ether sulfate (STEOL CS-330) was the foaming agent. The shear thinning fluid delivery (STFD) considerably improved the sweeping efficiency over a heterogeneous system and enhanced the non-aqueous liquid phase (NAPL) removal. The delivery of amendment into low-perm zones (LPZs) by STFD also

  5. Transpiration Driven Hydrologic Transport in vegetated shallow water environments: Implications on Diel and Seasonal Soil Biogeochemical Processes and System Management

    NASA Astrophysics Data System (ADS)

    Bachand, P.; Bachand, S. M.; Fleck, J.; Anderson, F.

    2011-12-01

    Hydrology arguably plays the most important role in biogeochemical cycling of mercury in wetlands and other shallow aquatic systems. CFSTR, PFR and non-ideal reactor models are oftentimes currently used to hydrologically assess these systems and to account for the fate, transport and cycling of constituents of concern (COC) with systems assumed to be non-leaky and with diffusion dominating soil transport. Yet a number of results in the literature imply transpiration drives soil transport: transpiration into the root zone is in the range of 50 - 75% of ET seasonally; gaseous emissions from aquatic systems show a diel pattern that tracks diel ET patterns; in long detention time aquatic systems ET is the largest sink for applied surface waters; and non-reactive tracers when applied to surface waters can find themselves in the root zone and within plants. All these findings strongly suggest transpiration driven infiltration into the root zone, is a significant hydrologic pathway for constituents and is an important transport mechanism. This paper examines the annual water budget for four shallow aquatic land uses in the Yolo Bypass, California: rice, wild rice, fallowed fields and wetlands. Results indicate that differences in hydrology between the fields, particularly the temporal nature of transpiration, play a significant role in mercury transformations and transport. During the irrigation period, fallowed fields discharged 6 cm of surface water (15% applied water), rice fields 31 - 43 cm (27 - 31% applied water), and wild rice fields 16 - 39 cm (15 - 31% applied water). Evapotranspiration rates were in the range of 120 - 130 cm/y for all land uses (i.e. rice, wild rice, fallowed fields and seasonal wetlands) except for the permanent wetland which was about 1/3 higher at about 170 cm/y. During the summer, approximately 50% of the applied surface water was drawn into the root zone to meet transpiration demands. Based upon results from our water budget and utilizing

  6. Luminescent microbanding in speleothems: High-resolution chronology and paleoclimate

    NASA Astrophysics Data System (ADS)

    Shopov, Y. Y.; Ford, D. C.; Schwarcz, H. P.

    1994-05-01

    When illuminated by ultraviolet light, many calcite speleothems (stalagmites, stalactites, flowstones) display luminescence caused by the presence of organic (humic) substances occluded in the calcite. The amplitude of luminescence varies in a banded pattern parallel to growth layering. Through 14C and thermal ionization mass spectrometry uranium-series dating, we show that cyclical oscillations in the luminescence have periodicities ranging from a few days to ≥105 yr. A well-defined annual cycle is present in many vadose-zone speleothems and can be used to define the chronology of short-term events. This cycle is probably a response to hydrological events in the recharge to the cave. Longer term oscillations are inferred to be controlled by climate, through its effect on organic activity in the overlying soil.

  7. Modelling past hydrology of an interfluve area in the Campine region (NE Belgium)

    NASA Astrophysics Data System (ADS)

    Leterme, Bertrand; Beerten, Koen; Gedeon, Matej; Vandersteen, Katrijn

    2015-04-01

    This study aims at hydrological model verification of a small lowland interfluve area (18.6 km²) in NE Belgium, for conditions that are different than today. We compare the current state with five reference periods in the past (AD 1500, 1770, 1854, 1909 and 1961) representing important stages of landscape evolution in the study area. Historical information and proxy data are used to derive conceptual model features and boundary conditions specific to each period: topography, surface water geometry (canal, drains and lakes), land use, soils, vegetation and climate. The influence of landscape evolution on the hydrological cycle is assessed using numerical simulations of a coupled unsaturated zone - groundwater model (HYDRUS-MODFLOW). The induced hydrological changes are assessed in terms of groundwater level, recharge, evapotranspiration, and surface water discharge. HYDRUS-MODFLOW coupling allows including important processes such as the groundwater contribution to evapotranspiration. Major land use change occurred between AD 1854 and 1909, with about 41% of the study area being converted from heath to coniferous forest, together with the development of a drainage network. Results show that this led to a significant decrease of groundwater recharge and lowering of the groundwater table. A limitation of the study lies in the comparison of simulated past hydrology with appropriate palaeo-records. Examples are given as how some indicators (groundwater head, swamp zones) can be used to tend to model validation. Quantifying the relative impact of land use and climate changes requires running sensitivity simulations where the models using alternative land use are run with the climate forcing of other periods. A few examples of such sensitivity runs are presented in order to compare the influence of land use and climate change on the study area hydrology.

  8. Hydrologic enforcement of lidar DEMs

    USGS Publications Warehouse

    Poppenga, Sandra K.; Worstell, Bruce B.; Danielson, Jeffrey J.; Brock, John C.; Evans, Gayla A.; Heidemann, H. Karl

    2014-01-01

    Hydrologic-enforcement (hydro-enforcement) of light detection and ranging (lidar)-derived digital elevation models (DEMs) modifies the elevations of artificial impediments (such as road fills or railroad grades) to simulate how man-made drainage structures such as culverts or bridges allow continuous downslope flow. Lidar-derived DEMs contain an extremely high level of topographic detail; thus, hydro-enforced lidar-derived DEMs are essential to the U.S. Geological Survey (USGS) for complex modeling of riverine flow. The USGS Coastal and Marine Geology Program (CMGP) is integrating hydro-enforced lidar-derived DEMs (land elevation) and lidar-derived bathymetry (water depth) to enhance storm surge modeling in vulnerable coastal zones.

  9. A Unified Multi-scale Model for Cross-Scale Evaluation and Integration of Hydrological and Biogeochemical Processes

    NASA Astrophysics Data System (ADS)

    Liu, C.; Yang, X.; Bailey, V. L.; Bond-Lamberty, B. P.; Hinkle, C.

    2013-12-01

    Mathematical representations of hydrological and biogeochemical processes in soil, plant, aquatic, and atmospheric systems vary with scale. Process-rich models are typically used to describe hydrological and biogeochemical processes at the pore and small scales, while empirical, correlation approaches are often used at the watershed and regional scales. A major challenge for multi-scale modeling is that water flow, biogeochemical processes, and reactive transport are described using different physical laws and/or expressions at the different scales. For example, the flow is governed by the Navier-Stokes equations at the pore-scale in soils, by the Darcy law in soil columns and aquifer, and by the Navier-Stokes equations again in open water bodies (ponds, lake, river) and atmosphere surface layer. This research explores whether the physical laws at the different scales and in different physical domains can be unified to form a unified multi-scale model (UMSM) to systematically investigate the cross-scale, cross-domain behavior of fundamental processes at different scales. This presentation will discuss our research on the concept, mathematical equations, and numerical execution of the UMSM. Three-dimensional, multi-scale hydrological processes at the Disney Wilderness Preservation (DWP) site, Florida will be used as an example for demonstrating the application of the UMSM. In this research, the UMSM was used to simulate hydrological processes in rooting zones at the pore and small scales including water migration in soils under saturated and unsaturated conditions, root-induced hydrological redistribution, and role of rooting zone biogeochemical properties (e.g., root exudates and microbial mucilage) on water storage and wetting/draining. The small scale simulation results were used to estimate effective water retention properties in soil columns that were superimposed on the bulk soil water retention properties at the DWP site. The UMSM parameterized from smaller

  10. A physically-based Distributed Hydrologic Model for Tropical Catchments

    NASA Astrophysics Data System (ADS)

    Abebe, N. A.; Ogden, F. L.

    2010-12-01

    Hydrological models are mathematical formulations intended to represent observed hydrological processes in a watershed. Simulated watersheds in turn vary in their nature based on their geographic location, altitude, climatic variables and geology and soil formation. Due to these variations, available hydrologic models vary in process formulation, spatial and temporal resolution and data demand. Many tropical watersheds are characterized by extensive and persistent biological activity and a large amount of rain. The Agua Salud catchments located within the Panama Canal Watershed, Panama, are such catchments identified by steep rolling topography, deep soils derived from weathered bedrock, and limited exposed bedrock. Tropical soils are highly affected by soil cracks, decayed tree roots and earthworm burrows forming a network of preferential flow paths that drain to a perched water table, which forms at a depth where the vertical hydraulic conductivity is significantly reduced near the bottom of the bioturbation layer. We have developed a physics-based, spatially distributed, multi-layered hydrologic model to simulate the dominant processes in these tropical watersheds. The model incorporates the major flow processes including overland flow, channel flow, matrix and non-Richards film flow infiltration, lateral downslope saturated matrix and non-Darcian pipe flow in the bioturbation layer, and deep saturated groundwater flow. Emphasis is given to the modeling of subsurface unsaturated zone soil moisture dynamics and the saturated preferential lateral flow from the network of macrospores. Preliminary results indicate that the model has the capability to simulate the complex hydrological processes in the catchment and will be a useful tool in the ongoing comprehensive ecohydrological studies in tropical catchments, and help improve our understanding of the hydrological effects of deforestation and aforestation.

  11. The influence of the hydrologic cycle on the extent of sea ice with climatic implications

    NASA Technical Reports Server (NTRS)

    Dean, Ken; Gosink, Joan

    1991-01-01

    The role was analyzed of the hydrologic cycle on the distribution of sea ice, and its influence on forcings and fluxes between the marine environment and the atmosphere. River discharge plays a significant role in degrading the sea ice before any melting occurs elsewhere along the coast. The influence is considered of river discharge on the albedo, thermal balance, and distribution of sea ice. Quantitative atmospheric-hydrologic models are being developed to describe these processes in the coastal zone. Input for the models will come from satellite images, hydrologic data, and field observations. The resulting analysis provides a basis for the study of the significance of the hydrologic cycle throughout the Arctic Basin and its influence on the regional climate as a result of possible climatic scenarios. The area offshore from the Mackenzie River delta was selected as the study area.

  12. Forest hydrology

    Treesearch

    Ge Sun; Devendra Amatya; Steve McNulty

    2016-01-01

    Forest hydrology studies the distribution, storage, movement, and quality of water and the hydrological processes in forest-dominated ecosystems. Forest hydrological science is regarded as the foundation of modern integrated water¬shed management. This chapter provides an overview of the history of forest hydrology and basic principles of this unique branch of...

  13. Towards a simple representation of chalk hydrology in land surface modelling

    NASA Astrophysics Data System (ADS)

    Rahman, Mostaquimur; Rosolem, Rafael

    2017-01-01

    Modelling and monitoring of hydrological processes in the unsaturated zone of chalk, a porous medium with fractures, is important to optimize water resource assessment and management practices in the United Kingdom (UK). However, incorporating the processes governing water movement through a chalk unsaturated zone in a numerical model is complicated mainly due to the fractured nature of chalk that creates high-velocity preferential flow paths in the subsurface. In general, flow through a chalk unsaturated zone is simulated using the dual-porosity concept, which often involves calibration of a relatively large number of model parameters, potentially undermining applications to large regions. In this study, a simplified parameterization, namely the Bulk Conductivity (BC) model, is proposed for simulating hydrology in a chalk unsaturated zone. This new parameterization introduces only two additional parameters (namely the macroporosity factor and the soil wetness threshold parameter for fracture flow activation) and uses the saturated hydraulic conductivity from the chalk matrix. The BC model is implemented in the Joint UK Land Environment Simulator (JULES) and applied to a study area encompassing the Kennet catchment in the southern UK. This parameterization is further calibrated at the point scale using soil moisture profile observations. The performance of the calibrated BC model in JULES is assessed and compared against the performance of both the default JULES parameterization and the uncalibrated version of the BC model implemented in JULES. Finally, the model performance at the catchment scale is evaluated against independent data sets (e.g. runoff and latent heat flux). The results demonstrate that the inclusion of the BC model in JULES improves simulated land surface mass and energy fluxes over the chalk-dominated Kennet catchment. Therefore, the simple approach described in this study may be used to incorporate the flow processes through a chalk unsaturated

  14. Reproducible research in vadose zone sciences

    USDA-ARS?s Scientific Manuscript database

    A significant portion of present-day soil and Earth science research is computational, involving complex data analysis pipelines, advanced mathematical and statistical models, and sophisticated computer codes. Opportunities for scientific progress are greatly diminished if reproducing and building o...

  15. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.

    2012-07-03

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  16. Thixotropic gel for vadose zone remediation

    DOEpatents

    Rhia, Brian D [Augusta, GA

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  17. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  18. Vadose zone flow convergence test suite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Butcher, B. T.

    Performance Assessment (PA) simulations for engineered disposal systems at the Savannah River Site involve highly contrasting materials and moisture conditions at and near saturation. These conditions cause severe convergence difficulties that typically result in unacceptable convergence or long simulation times or excessive analyst effort. Adequate convergence is usually achieved in a trial-anderror manner by applying under-relaxation to the Saturation or Pressure variable, in a series of everdecreasing RELAxation values. SRNL would like a more efficient scheme implemented inside PORFLOW to achieve flow convergence in a more reliable and efficient manner. To this end, a suite of test problems that illustratemore » these convergence problems is provided to facilitate diagnosis and development of an improved convergence strategy. The attached files are being transmitted to you describing the test problem and proposed resolution.« less

  19. Using a spatially-distributed hydrologic biogeochemistry model to study the spatial variation of carbon processes in a Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Shi, Y.; Eissenstat, D. M.; Davis, K. J.; He, Y.

    2015-12-01

    Forest carbon processes are affected by soil moisture, soil temperature and solar radiation. Most of the current biogeochemical models are 1-D and represent one point in space. Therefore they can neither resolve topographically driven hill-slope soil moisture patterns, nor simulate the nonlinear effects of soil moisture on carbon processes. A spatially-distributed biogeochemistry model, Flux-PIHM-BGC, has been developed by coupling the Biome-BGC (BBGC) model with a coupled physically-based land surface hydrologic model, Flux-PIHM. Flux-PIHM incorporates a land-surface scheme (adapted from the Noah land surface model) into the Penn State Integrated Hydrologic Model (PIHM). Because PIHM is capable of simulating lateral water flow and deep groundwater, Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. Flux-PIHM-BGC model was tested at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). The abundant observations at the SSHCZO, including eddy covariance fluxes, soil moisture, groundwater level, sap flux, stream discharge, litterfall, leaf area index, aboveground carbon stock, and soil carbon efflux, provided an ideal test bed for the coupled model. Model results show that when uniform solar radiation is used, vegetation carbon and soil carbon are positively correlated with soil moisture in space, which agrees with the observations within the watershed. When topographically-driven solar radiation is used, however, the wetter valley floor becomes radiation limited, and produces less vegetation and soil carbon than the drier hillslope due to the assumption that canopy height is uniform in the watershed. This contradicts with the observations, and suggests that a tree height model with dynamic allocation model are needed to reproduce the spatial variation of carbon processes within a watershed.

  20. Virtual hydrology observatory: an immersive visualization of hydrology modeling

    NASA Astrophysics Data System (ADS)

    Su, Simon; Cruz-Neira, Carolina; Habib, Emad; Gerndt, Andreas

    2009-02-01

    The Virtual Hydrology Observatory will provide students with the ability to observe the integrated hydrology simulation with an instructional interface by using a desktop based or immersive virtual reality setup. It is the goal of the virtual hydrology observatory application to facilitate the introduction of field experience and observational skills into hydrology courses through innovative virtual techniques that mimic activities during actual field visits. The simulation part of the application is developed from the integrated atmospheric forecast model: Weather Research and Forecasting (WRF), and the hydrology model: Gridded Surface/Subsurface Hydrologic Analysis (GSSHA). Both the output from WRF and GSSHA models are then used to generate the final visualization components of the Virtual Hydrology Observatory. The various visualization data processing techniques provided by VTK are 2D Delaunay triangulation and data optimization. Once all the visualization components are generated, they are integrated into the simulation data using VRFlowVis and VR Juggler software toolkit. VR Juggler is used primarily to provide the Virtual Hydrology Observatory application with fully immersive and real time 3D interaction experience; while VRFlowVis provides the integration framework for the hydrologic simulation data, graphical objects and user interaction. A six-sided CAVETM like system is used to run the Virtual Hydrology Observatory to provide the students with a fully immersive experience.

  1. Effect of Selected Modeling Assumptions on Subsurface Radionuclide Transport Projections for the Potential Environmental Management Disposal Facility at Oak Ridge, Tennessee

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Painter, Scott L.

    2016-06-28

    The Department of Energy’s Office of Environmental Management recently revised a Remedial Investigation/ Feasibility Study (RI/FS) that included an analysis of subsurface radionuclide transport at a potential new Environmental Management Disposal Facility (EMDF) in East Bear Creek Valley near Oak Ridge, Tennessee. The effect of three simplifying assumptions used in the RI/FS analyses are investigated using the same subsurface pathway conceptualization but with more flexible modeling tools. Neglect of vadose zone dispersion was found to be conservative or non-conservative, depending on the retarded travel time and the half-life. For a given equilibrium distribution coefficient, a relatively narrow range of half-lifemore » was identified for which neglect of vadose zone transport is non-conservative and radionuclide discharge into surface water is non-negligible. However, there are two additional conservative simplifications in the reference case that compensate for the non-conservative effect of neglecting vadose zone dispersion: the use of a steady infiltration rate and vadose zone velocity, and the way equilibrium sorption is used to represent transport in the fractured material of the saturated aquifer. With more realistic representations of all three processes, the RI/FS reference case was found to either provide a reasonably good approximation to the peak concentration or was significantly conservative (pessimistic) for all parameter combinations considered.« less

  2. Identifying Hydrologic Processes in Agricultural Watersheds Using Precipitation-Runoff Models

    USGS Publications Warehouse

    Linard, Joshua I.; Wolock, David M.; Webb, Richard M.T.; Wieczorek, Michael

    2009-01-01

    Understanding the fate and transport of agricultural chemicals applied to agricultural fields will assist in designing the most effective strategies to prevent water-quality impairments. At a watershed scale, the processes controlling the fate and transport of agricultural chemicals are generally understood only conceptually. To examine the applicability of conceptual models to the processes actually occurring, two precipitation-runoff models - the Soil and Water Assessment Tool (SWAT) and the Water, Energy, and Biogeochemical Model (WEBMOD) - were applied in different agricultural settings of the contiguous United States. Each model, through different physical processes, simulated the transport of water to a stream from the surface, the unsaturated zone, and the saturated zone. Models were calibrated for watersheds in Maryland, Indiana, and Nebraska. The calibrated sets of input parameters for each model at each watershed are discussed, and the criteria used to validate the models are explained. The SWAT and WEBMOD model results at each watershed conformed to each other and to the processes identified in each watershed's conceptual hydrology. In Maryland the conceptual understanding of the hydrology indicated groundwater flow was the largest annual source of streamflow; the simulation results for the validation period confirm this. The dominant source of water to the Indiana watershed was thought to be tile drains. Although tile drains were not explicitly simulated in the SWAT model, a large component of streamflow was received from lateral flow, which could be attributed to tile drains. Being able to explicitly account for tile drains, WEBMOD indicated water from tile drains constituted most of the annual streamflow in the Indiana watershed. The Nebraska models indicated annual streamflow was composed primarily of perennial groundwater flow and infiltration-excess runoff, which conformed to the conceptual hydrology developed for that watershed. The hydrologic

  3. Using a spatially-distributed hydrologic biogeochemistry model with a nitrogen transport module to study the spatial variation of carbon processes in a Critical Zone Observatory

    DOE PAGES

    Shi, Yuning; Eissenstat, David M.; He, Yuting; ...

    2018-05-12

    Terrestrial carbon processes are affected by soil moisture, soil temperature, nitrogen availability and solar radiation, among other factors. Most of the current ecosystem biogeochemistry models represent one point in space, and have limited characterization of hydrologic processes. Therefore these models can neither resolve the topographically driven spatial variability of water, energy, and nutrient, nor their effects on carbon processes. A spatially-distributed land surface hydrologic biogeochemistry model, Flux-PIHM-BGC, is developed by coupling the Biome-BGC model with a physically-based land surface hydrologic model, Flux-PIHM. In the coupled system, each Flux-PIHM model grid couples a 1-D Biome-BGC model. In addition, a topographic solarmore » radiation module and an advection-driven nitrogen transport module are added to represent the impact of topography on nutrient transport and solar energy distribution. Because Flux-PIHM is able to simulate lateral groundwater flow and represent the land surface heterogeneities caused by topography, Flux-PIHM-BGC is capable of simulating the complex interaction among water, energy, nutrient, and carbon in time and space. The Flux-PIHM-BGC model is tested at the Susquehanna/Shale Hills Critical Zone Observatory. Model results show that distributions of carbon and nitrogen stocks and fluxes are strongly affected by topography and landscape position, and tree growth is nitrogen limited. The predicted aboveground and soil carbon distributions generally agree with the macro patterns observed. Although the model underestimates the spatial variation, the predicted watershed average values are close to the observations. Lastly, the coupled Flux-PIHM-BGC model provides an important tool to study spatial variations in terrestrial carbon and nitrogen processes and their interactions with environmental factors, and to predict the spatial structure of the responses of ecosystems to climate change.« less

  4. Hydrologic Drivers of Soil Organic Carbon Erosion and Burial: Insights from a Spatially-explicit Model of a Degraded Landscape at the Calhoun Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Dialynas, Y. G.; Bras, R. L.; Richter, D. D., Jr.

    2017-12-01

    Soil erosion and burial of organic material may constitute a substantial sink of atmospheric CO2. Attempts to quantify impacts of soil erosion on the soil-atmosphere C exchange are limited by difficulties in accounting for the fate of eroded soil organic carbon (SOC), a key factor in estimating of the net effect of erosion on the C cycle. Processes that transport SOC are still inadequately represented in terrestrial carbon (C) cycle models. This study investigates hydrologic controls on SOC redistribution across the landscape focusing on dynamic feedbacks between watershed hydrology, soil erosional processes, and SOC burial. We use tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially-explicit model of SOC dynamics coupled with a physically-based hydro-geomorphic model. tRIBS-ECO systematically accounts for the fate of eroded SOC across the watershed: Rainsplash erosion and sheet erosion redistribute SOC from upland sites to depositional environments, altering depth-dependent soil biogeochemical properties in diverse soil profiles. Eroded organic material is transferred with sediment and can be partially oxidized upon transport, or preserved from decomposition by burial. The model was applied in the Calhoun Critical Zone Observatory (CZO), a site that is recovering from some of the most serious agricultural erosion in North America. Soil biogeochemical characteristics at multiple soil horizons were used to initialize the model and test performance. Remotely sensed soil moisture data (NASA SMAP) were used for model calibration. Results show significant rates of hydrologically-induced burial of SOC at the Calhoun CZO. We find that organic material at upland eroding soil profiles is largely mobilized by rainsplash erosion. Sheet erosion mainly drives C transport in lower elevation clayey soils. While SOC erosion and deposition rates declined with recent reforestation at the study site, the

  5. Using a spatially-distributed hydrologic biogeochemistry model with a nitrogen transport module to study the spatial variation of carbon processes in a Critical Zone Observatory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shi, Yuning; Eissenstat, David M.; He, Yuting

    Terrestrial carbon processes are affected by soil moisture, soil temperature, nitrogen availability and solar radiation, among other factors. Most of the current ecosystem biogeochemistry models represent one point in space, and have limited characterization of hydrologic processes. Therefore these models can neither resolve the topographically driven spatial variability of water, energy, and nutrient, nor their effects on carbon processes. A spatially-distributed land surface hydrologic biogeochemistry model, Flux-PIHM-BGC, is developed by coupling the Biome-BGC model with a physically-based land surface hydrologic model, Flux-PIHM. In the coupled system, each Flux-PIHM model grid couples a 1-D Biome-BGC model. In addition, a topographic solarmore » radiation module and an advection-driven nitrogen transport module are added to represent the impact of topography on nutrient transport and solar energy distribution. Because Flux-PIHM is able to simulate lateral groundwater flow and represent the land surface heterogeneities caused by topography, Flux-PIHM-BGC is capable of simulating the complex interaction among water, energy, nutrient, and carbon in time and space. The Flux-PIHM-BGC model is tested at the Susquehanna/Shale Hills Critical Zone Observatory. Model results show that distributions of carbon and nitrogen stocks and fluxes are strongly affected by topography and landscape position, and tree growth is nitrogen limited. The predicted aboveground and soil carbon distributions generally agree with the macro patterns observed. Although the model underestimates the spatial variation, the predicted watershed average values are close to the observations. Lastly, the coupled Flux-PIHM-BGC model provides an important tool to study spatial variations in terrestrial carbon and nitrogen processes and their interactions with environmental factors, and to predict the spatial structure of the responses of ecosystems to climate change.« less

  6. Fusion of Tomography Tests for DNAPL Source Zone Characterization: Technology Development and Validation

    DTIC Science & Technology

    2011-07-01

    alternative to the REV and fracture network concepts, pp. 533-561, Rock Mechanics : Proceedings of the 28th U.S. Symposium, Tucson, Arizona, edited by I.W...spatially integrated measure of residual DNAPL volume in the flow without causing disturbances to the source zone domain [ Jin et al., 1995; Nelson and...step. 6 Hydrological inversion has been a major focus of groundwater hydrology during the last three decades [see Yeh, 1986; Sun , 1994 and

  7. Modeling Water Flux at the Base of the Rooting Zone for Soils with Varying Glacial Parent Materials

    NASA Astrophysics Data System (ADS)

    Naylor, S.; Ellett, K. M.; Ficklin, D. L.; Olyphant, G. A.

    2013-12-01

    Soils of varying glacial parent materials in the Great Lakes Region (USA) are characterized by thin unsaturated zones and widespread use of agricultural pesticides and nutrients that affect shallow groundwater. To better our understanding of the fate and transport of contaminants, improved models of water fluxes through the vadose zones of various hydrogeologic settings are warranted. Furthermore, calibrated unsaturated zone models can be coupled with watershed models, providing a means for predicting the impact of varying climate scenarios on agriculture in the region. To address these issues, a network of monitoring sites was developed in Indiana that provides continuous measurements of precipitation, potential evapotranspiration (PET), soil volumetric water content (VWC), and soil matric potential to parameterize and calibrate models. Flux at the base of the root zone is simulated using two models of varying complexity: 1) the HYDRUS model, which numerically solves the Richards equation, and 2) the soil-water-balance (SWB) model, which assumes vertical flow under a unit gradient with infiltration and evapotranspiration treated as separate, sequential processes. Soil hydraulic parameters are determined based on laboratory data, a pedo-transfer function (ROSETTA), field measurements (Guelph permeameter), and parameter optimization. Groundwater elevation data are available at three of six sites to establish the base of the unsaturated zone model domain. Initial modeling focused on the groundwater recharge season (Nov-Feb) when PET is limited and much of the annual vertical flux occurs. HYDRUS results indicate that base of root zone fluxes at a site underlain by glacial ice-contact parent materials are 48% of recharge season precipitation (VWC RMSE=8.2%), while SWB results indicate that fluxes are 43% (VWC RMSE=3.7%). Due in part to variations in surface boundary conditions, more variable fluxes were obtained for a site underlain by alluvium with the SWB model (68

  8. The constructed catchment Chicken Creek as Critical Zone Observatory under transition

    NASA Astrophysics Data System (ADS)

    Gerwin, Werner; Schaaf, Wolfgang; Elmer, Michael; Hinz, Christoph

    2014-05-01

    The constructed catchment Chicken Creek was established in 2005 as an experimental landscape laboratory for ecosystem research. The 6 ha area with clearly defined horizontal as well as vertical boundary conditions was left for an unrestricted primary succession. All Critical Zone elements are represented at this site, which allows the study of most processes occurring at the interface of bio-, pedo-, geo- and hydrosphere. It provides outstanding opportunities for investigating interactions and feedbacks between different evolving compartments during ecosystem development. The catchment is extensively instrumented since 2005 in order to detect transition stages of the ecosystem. Data recorded with a high spatial and temporal resolution include hydrological, geomorphological, pedological, limnological as well as biological parameters. In contrast to other Critical Zone Observatories, this site offers the unique situation of an early stage ecosystem with highly dynamic system properties. The first years of development were characterized by a fast formation of geomorphological structures due to massive erosion processes at the initially non-vegetated surface. Hydrological processes led to the establishment of a local groundwater body within 5 years. In the following years the influence of biological structures like vegetation patterns gained an increasing importance. Feedbacks between developing vegetation and e.g. hydrological features became more and more dominant. As a result, different phases of ecosystem development could be distinguished until now. This observatory offers manifold possibilities to identify and disentangle complex interactions between Critical Zone processes in situ under natural conditions. The originally low complexity of the system is growing with time facilitating the identification of influences of newly developing structures on system functions. Thus, it is possible to study effects of small-scale processes on the whole system at the

  9. Hydrology

    NASA Astrophysics Data System (ADS)

    Brutsaert, Wilfried

    2005-08-01

    Water in its different forms has always been a source of wonder, curiosity and practical concern for humans everywhere. Hydrology - An Introduction presents a coherent introduction to the fundamental principles of hydrology, based on the course that Wilfried Brutsaert has taught at Cornell University for the last thirty years. Hydrologic phenomena are dealt with at spatial and temporal scales at which they occur in nature. The physics and mathematics necessary to describe these phenomena are introduced and developed, and readers will require a working knowledge of calculus and basic fluid mechanics. The book will be invaluable as a textbook for entry-level courses in hydrology directed at advanced seniors and graduate students in physical science and engineering. In addition, the book will be more broadly of interest to professional scientists and engineers in hydrology, environmental science, meteorology, agronomy, geology, climatology, oceanology, glaciology and other earth sciences. Emphasis on fundamentals Clarification of the underlying physical processes Applications of fluid mechanics in the natural environment

  10. Integrated Site Investigation Methods and Modeling: Recent Developments at the BHRS (Invited)

    NASA Astrophysics Data System (ADS)

    Barrash, W.; Bradford, J. H.; Cardiff, M. A.; Dafflon, B.; Johnson, B. A.; Malama, B.; Thoma, M. J.

    2010-12-01

    The Boise Hydrogeophysical Research Site (BHRS) is a field-scale test facility in an unconfined aquifer with the goals of: developing cost-effective, non-invasive methods for quantitative characterization of heterogeneous aquifers using hydrologic and geophysical techniques; understanding fundamental relations and processes at multiple scales; and testing theories and models for groundwater flow and solute transport. The design of the BHRS supports a wide range of single-well, cross-hole, multiwell and multilevel hydrologic, geophysical, and combined hydrogeophysical experiments. New installations support direct and geophysical monitoring of hydrologic fluxes and states from the aquifer through the vadose zone to the atmosphere, including ET and river boundary behavior. Efforts to date have largely focused on establishing the 1D, 2D, and 3D distributions of geologic, hydrologic, and geophysical parameters which can then be used as the basis for testing methods to integrate direct and indirect data and invert for “known” parameter distributions, material boundaries, and tracer test or other system state behavior. Aquifer structure at the BHRS is hierarchical and includes layers and lenses that are recognized with geologic, hydrologic, radar, electrical, and seismic methods. Recent advances extend findings and method developments, but also highlight the need to examine assumptions and understand secular influences when designing and modeling field tests. Examples of advances and caveats include: New high-resolution 1D K profiles obtained from multi-level slug tests (inversion improves with priors for aquifer K, wellbore skin, and local presence of roots) show variable correlation with porosity and bring into question a Kozeny-Carman-type relation for much of the system. Modeling of 2D conservative tracer transport through a synthetic BHRS-like heterogeneous system shows the importance of including porosity heterogeneity (rather than assuming constant porosity for

  11. Knowledge discovery from high-frequency stream nitrate concentrations: hydrology and biology contributions.

    PubMed

    Aubert, Alice H; Thrun, Michael C; Breuer, Lutz; Ultsch, Alfred

    2016-08-30

    High-frequency, in-situ monitoring provides large environmental datasets. These datasets will likely bring new insights in landscape functioning and process scale understanding. However, tailoring data analysis methods is necessary. Here, we detach our analysis from the usual temporal analysis performed in hydrology to determine if it is possible to infer general rules regarding hydrochemistry from available large datasets. We combined a 2-year in-stream nitrate concentration time series (time resolution of 15 min) with concurrent hydrological, meteorological and soil moisture data. We removed the low-frequency variations through low-pass filtering, which suppressed seasonality. We then analyzed the high-frequency variability component using Pareto Density Estimation, which to our knowledge has not been applied to hydrology. The resulting distribution of nitrate concentrations revealed three normally distributed modes: low, medium and high. Studying the environmental conditions for each mode revealed the main control of nitrate concentration: the saturation state of the riparian zone. We found low nitrate concentrations under conditions of hydrological connectivity and dominant denitrifying biological processes, and we found high nitrate concentrations under hydrological recession conditions and dominant nitrifying biological processes. These results generalize our understanding of hydro-biogeochemical nitrate flux controls and bring useful information to the development of nitrogen process-based models at the landscape scale.

  12. Environmental factors controlling transient and seasonal changes of trace gases within shallow vadose zone

    NASA Astrophysics Data System (ADS)

    Pla, Concepcion; Galiana-Merino, Juan Jose; Cuezva, Soledad; Fernandez-Cortes, Angel; Garcia-Anton, Elena; Cuevas, Jaime; Cañaveras, Juan Carlos; Sanchez-Moral, Sergio; Benavente, David

    2014-05-01

    Shallow vadose environments below soil, mainly caves, show significant seasonal and even daily variations in gas composition of ground air, which involves the exchange of large amounts of gases, e.g. greenhouse gases (GHGs) as CO2 or CH4, with the lower troposphere. To understand better the role of caves as a sink or depot of GHGs, geochemical tracing of air (atmosphere, soil and ground air) was performed at Rull cave (southeast Spain) by monitoring CH4, CO2 and the stable carbon isotopic delta13C[CO2] using cavity ring-down spectroscopy (CRDS). A comprehensive microclimatic monitoring of exterior and cave atmosphere was simultaneously conducted to GHGs-tracking, including factors as temperature, barometric pressure, relative humidity and concentration of CO2 and 222Rn. The analysis of the measured data allows understanding outgassing and isolation processes taking place in the karst cavity. Annual patterns of gases behaviour can be distinguished, depending on the prevailing relationship between outer atmosphere, indoor atmosphere and soil system. Cave air temperature fluctuates around 15.7 ºC and relative humidity remains higher than 96% the whole annual cycle. The mean concentration of 222Rn is 1584 Bq m-3 while CO2 remains 1921 ppm. When external temperature is higher of indoor temperature (April-October), the highest levels of both trace gases are reached, while levels drop to its lowest values in the coldest months. Preliminary results obtained show an annual variation in concentration of CO2 inside the cave between 3300 ppm and 900 ppm, whereas corresponding isotopic signal delta13CO2 varies between -24‰ and -21‰. The results have been studied by Keeling model that approximates the isotopic signal of the source contribution in a resulting air mix. The values registered inside the cave were represented joined to results for exterior air (average values round 410 ppm of CO2 and -9 ‰ for delta13C). Value obtained is -27‰ pointing to a high influence of

  13. Moisture Monitoring at Area G, Technical Area 54, Los Alamos National Laboratory, 2016 Status Report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Levitt, Daniel Glenn; Birdsell, Kay Hanson; Jennings, Terry L.

    Hydrological characterization and moisture monitoring activities provide data required for evaluating the transport of subsurface contaminants in the unsaturated and saturated zones beneath Area G, and for the Area G Performance Assessment and Composite Analysis. These activities have been ongoing at Area G, Technical Area 54 of the Los Alamos National Laboratory since waste disposal operations began in 1957. This report summarizes the hydrological characterization and moisture monitoring activities conducted at Area G. It includes moisture monitoring data collected from 1986 through 2016 from numerous boreholes and access tubes with neutron moisture meters, as well as data collected by automatedmore » dataloggers for water content measurement sensors installed in a waste disposal pit cover, and buried beneath the floor of a waste disposal pit. This report is an update of a nearly identical report by Levitt et al., (2015) that summarized data collected through early 2015; this report includes additional moisture monitoring data collected at Pit 31 and the Pit 38 extension through December, 2016. It also includes information from the Jennings and French (2009) moisture monitoring report and includes all data from Jennings and French (2009) and the Draft 2010 Addendum moisture monitoring report (Jennings and French, 2010). For the 2015 version of this report, all neutron logging data, including neutron probe calibrations, were investigated for quality and pedigree. Some data were recalculated using more defensible calibration data. Therefore, some water content profiles are different from those in the Jennings and French (2009) report. All of that information is repeated in this report for completeness. Monitoring and characterization data generally indicate that some areas of the Area G vadose zone are consistent with undisturbed conditions, with water contents of less than five percent by volume in the top two layers of the Bandelier tuff at Area G. These data

  14. Linking channel hydrology with riparian wetland accretion in tidal rivers

    USGS Publications Warehouse

    Ensign, Scott H.; Noe, Gregory B.; Hupp, Cliff R.

    2014-01-01

    The hydrologic processes by which tide affects river channel and riparian morphology within the tidal freshwater zone are poorly understood, yet are fundamental to predicting the fate of coastal rivers and wetlands as sea level rises. We investigated patterns of sediment accretion in riparian wetlands along the non-tidal through oligohaline portion of two coastal plain rivers in Maryland, U.S.A., and how flow velocity, water level, and suspended sediment concentration (SSC) in the channel may have contributed to those patterns. Sediment accretion was measured over a one year period using artificial marker horizons, channel hydrology was measured over a one month period using acoustic Doppler current profilers, and SSC was predicted from acoustic backscatter. Riparian sediment accretion was lowest at the non-tidal sites (mean and standard deviation = 8 ± 8 mm yr-1), highest at the upstream tidal freshwater forested wetlands (TFFW) (33 ± 28 mm yr-1), low at the midstream TFFW (12 ± 9 mm yr-1), and high at the oligohaline (fresh-to-brackish) marshes (19 ± 8 mm yr-1). Channel maximum flood and ebb velocity was 2-fold faster at the oligohaline than tidal freshwater zone on both tidal rivers, corresponding with the differences in in-channel SSC: the oligohaline zone's SSC was more than double the tidal freshwater zone's, and was greater than historical SSC at the non-tidal gages. The tidal wave characteristics differed between rivers, leading to significantly greater in-channel SSC during floodplain inundation in the weakly convergent than the strongly convergent tidal river. Overall sediment accretion was higher in the embayed river likely due to a single storm discharge and associated sedimentation.

  15. Assessing Hydrologic Impacts of Land Configuration Changes Using an Integrated Hydrologic Model at the Rocky Flats Environmental Technology Site, Colorado

    NASA Astrophysics Data System (ADS)

    Prucha, R. H.; Dayton, C. S.; Hawley, C. M.

    2002-12-01

    The Rocky Flats Environmental Technology Site (RFETS) in Golden, Colorado, a former Department of Energy nuclear weapons manufacturing facility, is currently undergoing closure. The natural semi-arid interaction between surface and subsurface flow at RFETS is complex and complicated by the industrial modifications to the flow system. Using a substantial site data set, a distributed parameter, fully-integrated hydrologic model was developed to assess the hydrologic impact of different hypothetical site closure configurations on the current flow system and to better understand the integrated hydrologic behavior of the system. An integrated model with this level of detail has not been previously developed in a semi-arid area, and a unique, but comprehensive, approach was required to calibrate and validate the model. Several hypothetical scenarios were developed to simulate hydrologic effects of modifying different aspects of the site. For example, some of the simulated modifications included regrading the current land surface, changing the existing surface channel network, removing subsurface trenches and gravity drain flow systems, installing a slurry wall and geotechnical cover, changing the current vegetative cover, and converting existing buildings and pavement to permeable soil areas. The integrated flow model was developed using a rigorous physically-based code so that realistic design parameters can simulate these changes. This code also permitted evaluation of changes to complex integrated hydrologic system responses that included channelized and overland flow, pond levels, unsaturated zone storage, groundwater heads and flow directions, and integrated water balances for key areas. Results generally show that channel flow offsite decreases substantially for different scenarios, while groundwater heads generally increase within the reconfigured industrial area most of which is then discharged as evapotranspiration. These changes have significant implications to

  16. Carbon dioxide, ground air and carbon cycling in Gibraltar karst

    NASA Astrophysics Data System (ADS)

    Mattey, D. P.; Atkinson, T. C.; Barker, J. A.; Fisher, R.; Latin, J.-P.; Durrell, R.; Ainsworth, M.

    2016-07-01

    We put forward a general conceptual model of CO2 behaviour in the vadose zone of karst aquifers, based on physical principles of air flow through porous media and caves, combined with a geochemical interpretation of cave monitoring data. This 'Gibraltar model' links fluxes of water, air and carbon through the soil with the porosity of the vadose zone, the circulation of ground air and the ventilation of caves. Gibraltar hosts many natural caves whose locations span the full length and vertical range of the Rock. We report results of an 8-year monitoring study of carbon in soil organic matter and bedrock carbonate, dissolved inorganic carbon in vadose waters, and gaseous CO2 in soil, cave and ground air. Results show that the regime of cave air CO2 results from the interaction of cave ventilation with a reservoir of CO2-enriched ground air held within the smaller voids of the bedrock. The pCO2 of ground air, and of vadose waters that have been in close contact with it, are determined by multiple factors that include recharge patterns, vegetation productivity and root respiration, and conversion of organic matter to CO2 within the soil, the epikarst and the whole vadose zone. Mathematical modelling and field observations show that ground air is subject to a density-driven circulation that reverses seasonally, as the difference between surface and underground temperatures reverses in sign. The Gibraltar model suggests that cave air pCO2 is not directly related to CO2 generated in the soil or the epikarstic zone, as is often assumed. Ground air CO2 formed by the decay of organic matter (OM) washed down into the deeper unsaturated zone is an important additional source of pCO2. In Gibraltar the addition of OM-derived CO2 is the dominant control on the pCO2 of ground air and the Ca-hardness of waters within the deep vadose zone. The seasonal regime of CO2 in cave air depends on the position of a cave in relation to the density-driven ground air circulation pattern which

  17. What is the philosophy of modelling soil moisture movement?

    NASA Astrophysics Data System (ADS)

    Chen, J.; Wu, Y.

    2009-12-01

    In laboratory, the soil moisture movement in the different soil textures has been analysed. From field investigation, at a spot, the soil moisture movement in the root zone, vadose zone and shallow aquifer has been explored. In addition, on ground slopes, the interflow in the near surface soil layers has been studied. Along the regions near river reaches, the expansion and shrink of the saturated area due to rainfall occurrences have been observed. From those previous explorations regarding soil moisture movement, numerical models to represent this hydrologic process have been developed. However, generally, due to high heterogeneity and stratification of soil in a basin, modelling soil moisture movement is rather challenging. Normally, some empirical equations or artificial manipulation are employed to adjust the soil moisture movement in various numerical models. In this study, we inspect the soil moisture movement equations used in a watershed model, SWAT (Soil and Water Assessment Tool) (Neitsch et al., 2005), to examine the limitations of our knowledge in such a hydrologic process. Then, we adopt the features of a topographic-information based on a hydrologic model, TOPMODEL (Beven and Kirkby, 1979), to enhance the representation of soil moisture movement in SWAT. Basically, the results of the study reveal, to some extent, the philosophy of modelling soil moisture movement in numerical models, which will be presented in the conference. Beven, K.J. and Kirkby, M.J., 1979. A physically based variable contributing area model of basin hydrology. Hydrol. Science Bulletin, 24: 43-69. Neitsch, S.L., Arnold, J.G., Kiniry, J.R., Williams, J.R. and King, K.W., 2005. Soil and Water Assessment Tool Theoretical Documentation, Grassland, soil and research service, Temple, TX.

  18. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zachara, John M.; Chen, Xingyuan; Murray, Chris

    In this study, a well-field within a uranium (U) plume in the groundwater-surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (U aq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time seriesmore » trends for U aq and SpC were complex and displayed large temporal and well-to-well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot-spots in U aq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized U aq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While U aq time-series concentration trends varied significantly from year-to-year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.« less

  19. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone

    DOE PAGES

    Zachara, John M.; Chen, Xingyuan; Murray, Chris; ...

    2016-03-04

    In this study, a well-field within a uranium (U) plume in the groundwater-surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (U aq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time seriesmore » trends for U aq and SpC were complex and displayed large temporal and well-to-well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot-spots in U aq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized U aq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While U aq time-series concentration trends varied significantly from year-to-year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.« less

  20. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone: U TRANSPORT IN A GROUNDWATER-SURFACE WATER TRANSITION ZONE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zachara, John M.; Chen, Xingyuan; Murray, Chris

    A tightly spaced well-field within a groundwater uranium (U) plume in the groundwater-surface water transition zone was monitored for a three year period for groundwater elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from mountain snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time series trendsmore » for Uaq and SpC were complex and displayed large temporal well-to well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common temporal behaviors resulting from the intrusion dynamics of river water and the location of source terms. Concentration hot spots were observed in groundwater that varied in location with increasing water table elevation. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized U was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While uranium time-series concentration trends varied significantly from year to year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of the river water intrusion event.« less

  1. Hydrology and Geostatistics of a Vermont, USA Kettlehole Peatland

    NASA Astrophysics Data System (ADS)

    Mouser, Paula J.; Hession, W. Cully; Rizzo, Donna M.; Gotelli, Nicholas J.

    2005-01-01

    The ability to predict the response of peatland ecosystems to hydrologic changes is imperative for successful conservation and remediation efforts. We studied a 1.25-ha Vermont kettlehole bog for one year (September 2001-October 2002) to identify hydrologic controls, temporal and spatial variability in flow regimes, and to link hydrologic processes to density of the carnivorous plant ( Sarracenia purpurea), an ombrotrophic bog specialist. Using a spatial array of nested piezometers, we measured surface and subsurface flow in shallow peat and surrounding mineral soil. Our unique sampling array was based on a repeated measures factorial design with: (1) incremental distances from a central kettlehole pond; (2) equal distances between piezometers; and (3) at three depths from the peat surface. Local flow patterns in the peat were controlled by snowpack storage during winter and spring months and by evapotranspiration and pond water elevation during summer and fall months. Hydraulic head values showed a local reversal within the peat during spring months which was reflected in higher chemical constituent concentrations in these wells. On a regional scale, higher permeable soils diverted groundwater beneath the peatland to a nearby wetland complex. Horizontal water gradient magnitudes were larger in zones where the peatland was perched above regional groundwater and smaller in zones where a hydraulic connection existed between the peatland and the regional groundwater. The density of pitcher plants ( S. purpurea) is strongly correlated to the distance from a central pond, [Fe 3+], [Na +], [Cl -], and [SO42-]. The pH, conductivity, and [Ca 2+] had significant effects of depth and time with horizontal distance correlations between 20 and 26 m. The pH samples had temporal correlations between 27 and 79 days. The link between pitcher plants and ion chemistry; significant effects of peatland chemistry on distance, depth, and time; and spatial and temporal correlations are

  2. Concentration-Discharge Relations in the Critical Zone: Implications for Resolving Critical Zone Structure, Function, and Evolution

    NASA Astrophysics Data System (ADS)

    Chorover, Jon; Derry, Louis A.; McDowell, William H.

    2017-11-01

    Critical zone science seeks to develop mechanistic theories that describe critical zone structure, function, and long-term evolution. One postulate is that hydrogeochemical controls on critical zone evolution can be inferred from solute discharges measured down-gradient of reactive flow paths. These flow paths have variable lengths, interfacial compositions, and residence times, and their mixing is reflected in concentration-discharge (C-Q) relations. Motivation for this special section originates from a U.S. Critical Zone Observatories workshop that was held at the University of New Hampshire, 20-22 July 2015. The workshop focused on resolving mechanistic CZ controls over surface water chemical dynamics across the full range of lithogenic (e.g., nonhydrolyzing and hydrolyzing cations and oxyanions) and bioactive solutes (e.g., organic and inorganic forms of C, N, P, and S), including dissolved and colloidal species that may cooccur for a given element. Papers submitted to this special section on "concentration-discharge relations in the critical zone" include those from authors who attended the workshop, as well as others who responded to the open solicitation. Submissions were invited that utilized information pertaining to internal, integrated catchment function (relations between hydrology, biogeochemistry, and landscape structure) to help illuminate controls on observed C-Q relations.

  3. Long term (2006-2016) seasonal and inter-annual variability of soil electrical resistivity in a Laotian catchment of the OZCAR network. Impact of land use change, soil type and rainfall

    NASA Astrophysics Data System (ADS)

    Robain, Henri; Ribolzi, Olivier; De Rouw, Anneke; Silvera, Norbert; Souniaphong, Phabvilay; Soulileuth, Bousamai; Latchasak, Keooudone; Sengtaheuanghoung, Oloth; Valentin, Christian; Gaillardet, Jerome

    2017-04-01

    The MSEC(1) observatory of the critical zone in south-east Asia, which is part of the OZCAR(2) Network, has been monitored since 1999 (Laos, Thailand, Vietnam) to study the long term impact of land use changes in tropical mountainous regions, in terms of soil properties (porosity, depth, SOC, nutrients…), biodiversity (weeds, soil macro fauna), plant roots (architecture, functions,…), and transfers within the critical zone at various temporal and space scales: partition between infiltration and runoff, water quality (physical, chemical and bacteriological) and erosion processes (splash, inter-rill and rill, tillage, mass-movement). In the Houay Pano catchment located in Northern Laos, a long-term monitoring system was implemented in 2006 combining Electrical Resistivity Tomography (ERT), with soil and hydrological equipments to better analyse the interactions between bank and hillslopes groundwater, and streamwater, in a context of steep slopes (>50%) and rapid land use change (conversion of annual crops to teak plantation). This continuous ERT monitoring has been carried out along a representative 100 m long transect in the middle of the 65 ha catchment perpendicular to the stream. The data were collected every week during rainy season and every second week during dry season. It has been associated with hydrological monitoring (piezometers, limnimeters, gauging weirs). Such high resolution geophysical monitoring data set (approx. 900 apparent resistivity measurements for each acquisition) provides an invaluable non-invasive proxy of soil water content variations in the different layers of the vadose zone. It demonstrates: i) the influence of plant cover on water infiltration; ii) the pathways for vertical and horizontal water fluxes within the soil cover; iii) the control of soil organisation along the hillslope over the hydrological behaviour of the unsaturated part of the critical zone. (1) «Multi-Scale Environmental Changes» : http://msec.obs-mip.fr/ (2

  4. Deterministic influences exceed dispersal effects on hydrologically-connected microbiomes.

    PubMed

    Graham, Emily B; Crump, Alex R; Resch, Charles T; Fansler, Sarah; Arntzen, Evan; Kennedy, David W; Fredrickson, Jim K; Stegen, James C

    2017-04-01

    Subsurface groundwater-surface water mixing zones (hyporheic zones) have enhanced biogeochemical activity, but assembly processes governing subsurface microbiomes remain a critical uncertainty in understanding hyporheic biogeochemistry. To address this obstacle, we investigated (a) biogeographical patterns in attached and waterborne microbiomes across three hydrologically-connected, physicochemically-distinct zones (inland hyporheic, nearshore hyporheic and river); (b) assembly processes that generated these patterns; (c) groups of organisms that corresponded to deterministic changes in the environment; and (d) correlations between these groups and hyporheic metabolism. All microbiomes remained dissimilar through time, but consistent presence of similar taxa suggested dispersal and/or common selective pressures among zones. Further, we demonstrated a pronounced impact of deterministic assembly in all microbiomes as well as seasonal shifts from heterotrophic to autotrophic microorganisms associated with increases in groundwater discharge. The abundance of one statistical cluster of organisms increased with active biomass and respiration, revealing organisms that may strongly influence hyporheic biogeochemistry. Based on our results, we propose a conceptualization of hyporheic zone metabolism in which increased organic carbon concentrations during surface water intrusion support heterotrophy, which succumbs to autotrophy under groundwater discharge. These results provide new opportunities to enhance microbially-explicit ecosystem models describing hyporheic zone biogeochemistry and its influence over riverine ecosystem function. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Ecological impacts of winter water level drawdowns on lake littoral zones: A review

    USGS Publications Warehouse

    Roy, Allison

    2017-01-01

    Freshwater littoral zones harbor diverse ecological communities and serve numerous ecosystem functions that are controlled, in part, by natural water level fluctuations. However, human alteration of lake hydrologic regimes beyond natural fluctuations threaten littoral zone ecological integrity. One type of hydrologic alteration in lakes is winter water level drawdowns, which are frequently employed for hydropower, flood control, and macrophyte control, among other purposes. Here, we synthesize the abiotic and biotic responses to annual and novel winter water level drawdowns in littoral zones of lakes and reservoirs. The dewatering, freezing, and increased erosion of exposed lakebeds drive changes in the littoral zone. Shoreline-specific physicochemical conditions such as littoral slope and shoreline exposure further induce modifications. Loss of fine sediment decreases nutrient availability over time, but desiccation may promote a temporary nutrient pulse upon re-inundation. Annual winter drawdowns can decrease taxonomic richness of macrophytes and benthic invertebrates and shift assemblage composition to favor taxa with r-selected life history strategies and with functional traits resistant to direct and indirect drawdown effects. Fish assemblages, though less directly affected by winter drawdowns (except where there is critically low dissolved oxygen), experience negative effects via indirect pathways like decreased food resources and spawning habitat. We identify eight general research gaps to guide future research that could improve our understanding about the complex effects of winter drawdowns on littoral zone ecology.

  6. Inflatable straddle packers and associated equipment for hydraulic fracturing and hydrologic testing

    USGS Publications Warehouse

    Shuter, Eugene; Pemberton, Robert R.

    1978-01-01

    Independent aquifer testing is the only way to fully understand the hydrology encountered in boreholes intersecting multiple aquifers. The most feasible method to accomplish the testing of multiple aquifer wells is through the use inflatable packers. The straddle packers and associated equipment herein described arE valuable tools for making isolated aquifer tests as well as conducting hydraulic fracturing experiments. The system, due to design, permits multiple tests in a bore-hole without the necessity of tripping in and out of the hole to redress the packers prior to testing each zone. Electronic pressure transducers, the output of which was fed into strip-chart recorders, were used to monitor the zone being tested, as well as to monitor the zones above and below the packers. This was necessary to ensure that no leaking had occurred around the packers, causing hydraulic continuity between the isolated zones.

  7. Two dimensional hydrological simulation in elastic swelling/shrinking peat soils

    NASA Astrophysics Data System (ADS)

    Camporese, M.; Ferraris, S.; Paniconi, C.; Putti, M.; Salandin, P.; Teatini, P.

    2005-12-01

    Peatlands respond to natural hydrologic cycles of precipitation and evapotranspiration with reversible deformations due to variations of water content in both the unsaturated and saturated zone. This phenomenon results in short-term vertical displacements of the soil surface that superimpose to the irreversible long-term subsidence naturally occurring in drained cropped peatlands because of bio-oxidation of the organic matter. The yearly sinking rates due to the irreversible process are usually comparable with the short-term deformation (swelling/shrinkage) and the latter must be evaluated to achieve a thorough understanding of the whole phenomenon. A mathematical model describing swelling/shrinkage dynamics in peat soils under unsaturated conditions has been derived from simple physical considerations, and validated by comparison with laboratory shrinkage data. The two-parameter model relates together the void and moisture ratios of the soil. This approach is implemented in a subsurface flow model describing variably saturated porous media flow (Richards' equation), by means of an appropriate modification of the general storage term. The contribution of the saturated zone to total deformation is considered by using information from the elastic storage coefficient. Simulations have been carried out for a drained cropped peatland south of the Venice Lagoon (Italy), for which a large data set of hydrological and deformation measurements has been collected since the end of 2001. The considered domain is representative of a field section bounded by ditches, subject to rainfall and evapotranspiration. The comparison between simulated and measured quantities demonstrates the capability of the model to accurately reproduce both the hydrological and deformation dynamics of peat, with values of the relevant parameters that are in good agreement with the literature.

  8. Measuring and modeling of a three-dimensional tracer transport in a planted soil column

    NASA Astrophysics Data System (ADS)

    Schroeder, N.; Javaux, M.; Haber-Pohlmeier, S.; Pohlmeier, A. J.; Huber, K.; Vereecken, H.; Vanderborght, J.

    2013-12-01

    Predicting Root Water Uptake, Vadose Zone Journal, 7(3), 1079-1079. [2] Schröder, N., M. Javaux, J. Vanderborght, B. Steffen, and H. Vereecken (2012), Effect of Root Water and Solute Uptake on Apparent Soil Dispersivity: A Simulation Study, Vadose Zone Journal, 11(3). [3 ]Haber-Pohlmeier, S., Bechtold, M., Stapf, S., and Pohlmeier, A. (2010). Water Flow Monitored by Tracer Transport in Natural Porous Media Using Magnetic Resonance Imaging. Vadose Zone Journal (9),835-845. [4] Stingaciu, L. R., Schulz, H., Pohlmeier, A., Behnke, S., Zilken, H., Vereecken, H., and Javaux, M. (2013). In Situ Root System Architecture Extraction from Magnetic Resonance Imaging for Application to Water Uptake Modeling. Vadose Zone Journal.

  9. Oregon Hydrologic Landscapes: An Approach for Broadscale Hydrologic Classification

    EPA Science Inventory

    Gaged streams represent only a small percentage of watershed hydrologic conditions throughout the Unites States and globe, but there is a growing need for hydrologic classification systems that can serve as the foundation for broad-scale assessments of the hydrologic functions of...

  10. Fault zone hydrogeologic properties and processes revealed by borehole temperature monitoring

    NASA Astrophysics Data System (ADS)

    Fulton, P. M.; Brodsky, E. E.

    2015-12-01

    High-resolution borehole temperature monitoring can provide valuable insight into the hydrogeologic structure of fault zones and transient processes that affect fault zone stability. Here we report on results from a subseafloor temperature observatory within the Japan Trench plate boundary fault. In our efforts to interpret this unusual dataset, we have developed several new methods for probing hydrogeologic properties and processes. We illustrate how spatial variations in the thermal recovery of the borehole after drilling and other spectral characteristics provide a measure of the subsurface permeability architecture. More permeable zones allow for greater infiltration of cool drilling fluids, are more greatly thermally disturbed, and take longer to recover. The results from the JFAST (Japan Trench Fast Drilling Project) observatory are consistent with geophysical logs, core data, and other hydrologic observations and suggest a permeable damage zone consisting of steeply dipping faults and fractures overlays a low-permeability clay-rich plate boundary fault. Using high-resolution time series data, we have also developed methods to map out when and where fluid advection occurs in the subsurface over time. In the JFAST data, these techniques reveal dozens of transient earthquake-driven fluid pulses that are spatially correlated and consistently located around inferred permeable areas of the fault damage zone. These observations are suspected to reflect transient fluid flow driven by pore pressure changes in response to dynamic and/or static stresses associated with nearby earthquakes. This newly recognized hydrologic phenomenon has implications for understanding subduction zone heat and chemical transport as well as the redistribution of pore fluid pressure which influences fault stability and can trigger other earthquakes.

  11. Water chemistry at Snowshoe Mountain, Colorado: mixed processes in a common bedrock

    USGS Publications Warehouse

    Hoch, A.R.; Reddy, M.M.

    2001-01-01

    At Snowshoe Mountain the primary bedrock is quite homogeneous, but weathering processes vary as waters moves through the soils, vadose zone and phreatic zone of the subsurface. In the thin soil, physical degradation of tuff facilitates preferential dissolution of potassium ion from glass within the rock matrix, while other silicate minerals remain unaltered. In the vadose zone, in the upper few meters of fractured bedrock, dilute water infiltrates during spring snowmelt and summer storms, leading to preferential dissolution of augite exposed on fracture surfaces. Deeper yet, in the phreatic zone of the fractured bedrock, Pleistocene calcite fracture fillings dissolve, and dioctahedral and trioctahedral clays form as penetrative weathering alters feldspar and pyroxene. Alkalinity is generated and silica concentrations are buffered by mineral alteration reactions.

  12. Implications of groundwater hydrology to buffer design in the southeastern U.S.

    Treesearch

    Ge Sun; James M. Vose; Devendra M. Amatya; Carl Trettin; Steven G. McNulty

    2008-01-01

    The objective of this study was to examine the hydrologic processes of shallow groundwater to better define and design forest riparian management zones in headwater streams of two contrasting terrains in the southeastern U.S. We employed two long-term experimental watersheds, WS80 (206 ha) and WS77 (151 ha) at the Santee Experimental Forests in South Carolina, and WS2...

  13. Delineating riparian zones for entire river networks using geomorphological criteria

    NASA Astrophysics Data System (ADS)

    Fernández, D.; Barquín, J.; Álvarez-Cabria, M.; Peñas, F. J.

    2012-03-01

    Riparian zone delineation is a central issue for riparian and river ecosystem management, however, criteria used to delineate them are still under debate. The area inundated by a 50-yr flood has been indicated as an optimal hydrological descriptor for riparian areas. This detailed hydrological information is, however, not usually available for entire river corridors, and is only available for populated areas at risk of flooding. One of the requirements for catchment planning is to establish the most appropriate location of zones to conserve or restore riparian buffer strips for whole river networks. This issue could be solved by using geomorphological criteria extracted from Digital Elevation Models. In this work we have explored the adjustment of surfaces developed under two different geomorphological criteria with respect to the flooded area covered by the 50-yr flood, in an attempt to rapidly delineate hydrologically-meaningful riparian zones for entire river networks. The first geomorphological criterion is based on the surface that intersects valley walls at a given number of bankfull depths above the channel (BFDAC), while the second is based on the surface defined by a~threshold value indicating the relative cost of moving from the stream up to the valley, accounting for slope and elevation change (path distance). As the relationship between local geomorphology and 50-yr flood has been suggested to be river-type dependant, we have performed our analyses distinguishing between three river types corresponding with three valley morphologies: open, shallow vee and deep vee valleys (in increasing degree of valley constrainment). Adjustment between the surfaces derived from geomorphological and hydrological criteria has been evaluated using two different methods: one based on exceeding areas (minimum exceeding score) and the other on the similarity among total area values. Both methods have pointed out the same surfaces when looking for those that best match with

  14. Hydrology

    ERIC Educational Resources Information Center

    Sharp, John M., Jr.

    1978-01-01

    The past year saw a re-emphasis on the practical aspects of hydrology due to regional drought patterns, urban flooding, and agricultural and energy demands on water resources. Highlights of hydrologic symposia, publications, and events are included. (MA)

  15. Hydrologic conditions controlling runoff generation immediately after wildfire

    USGS Publications Warehouse

    Ebel, Brian A.; Moody, John A.; Martin, Deborah A.

    2012-01-01

    We investigated the control of postwildfire runoff by physical and hydraulic properties of soil, hydrologic states, and an ash layer immediately following wildfire. The field site is within the area burned by the 2010 Fourmile Canyon Fire in Colorado, USA. Physical and hydraulic property characterization included ash thickness, particle size distribution, hydraulic conductivity, and soil water retention curves. Soil water content and matric potential were measured indirectly at several depths below the soil surface to document hydrologic states underneath the ash layer in the unsaturated zone, whereas precipitation and surface runoff were measured directly. Measurements of soil water content showed that almost no water infiltrated below the ash layer into the near-surface soil in the burned site at the storm time scale (i.e., minutes to hours). Runoff generation processes were controlled by and highly sensitive to ash thickness and ash hydraulic properties. The ash layer stored from 97% to 99% of rainfall, which was critical for reducing runoff amounts. The hydrologic response to two rain storms with different rainfall amounts, rainfall intensity, and durations, only ten days apart, indicated that runoff generation was predominantly by the saturation-excess mechanism perched at the ash-soil interface during the first storm and predominantly by the infiltration-excess mechanism at the ash surface during the second storm. Contributing area was not static for the two storms and was 4% (saturation excess) to 68% (infiltration excess) of the catchment area. Our results showed the importance of including hydrologic conditions and hydraulic properties of the ash layer in postwildfire runoff generation models.

  16. Compound-specific isotope analysis (CSIA) for assessing pesticide dynamics in soil and vadose zone

    NASA Astrophysics Data System (ADS)

    Torrentó, Clara; Bakkour, Rani; Melsbach, Aileen; Ponsin, Violaine; Lihl, Christina; Prasuhn, Volker; Hofstetter, Thomas B.; Elsner, Martin; Hunkeler, Daniel

    2017-04-01

    A lysimeter facility was used to study long-term pesticide fate and transport through two different soils. The present investigation focuses on some commonly and worldwide used herbicides for weed control on corn (atrazine, acetochlor and metolachlor) and sugar beet (chloridazon), together with their main degradation products. Since some degradation products are found more frequently and at higher concentrations that their parent compounds, there is growing environmental concern. The fate of these metabolites is, however, not well-understood. Twelve weighing lysimeters filled with two typical arable soils in Switzerland (a well-drained sandy loam cambisol developed from a stony alluvium-"gravel soil"- and a poorly-drained loam cambisol developed from moraine deposits -"moraine soil"-) were cropped with corn in the first and third seasons, and sugar beet in the second one. Three types of experiments were performed: (1) herbicides application at the surface simulating the common application scenario, (2) herbicides injection at a depth of 40 cm for simulating high preferential transport through the topsoil and assessing the dynamics below the root zone, and (3) metabolites (2,6-dichlorobenzamide, desphenylchloridazon and desethylatrazine) application at the surface to simulate rapid generation of transformation products from the parent compounds. Leachate was collected and the concentration of the applied substances and main degradation products was determined. Since assessing transport and fate of micropollutants in the environment is extremely difficult because transformation processes are slow and may not become evident from analysis of concentrations, multi-element (C, N, Cl) compound-specific isotope analysis (CSIA) is also being used. With both surface application and depth injection, compound breakthrough by preferential as well as matrix flow was observed. A few days after their application, significant infiltration of the herbicides took place by

  17. Nitrous oxide production and consumption by denitrification in a grassland: Effects of grazing and hydrology.

    PubMed

    Hu, Jing; Inglett, Kanika S; Clark, Mark W; Inglett, Patrick W; Ramesh Reddy, K

    2015-11-01

    Denitrification is generally recognized as a major mechanism contributing to nitrous oxide (N2O) production, and is the only known biological process for N2O consumption. Understanding factors controlling N2O production and consumption during denitrification will provide insights into N2O emission variability, and potentially predict capacity of soils to serve as sinks or sources of N2O. This study investigated the effects of hydrology and grazing on N2O production and consumption in a grassland based agricultural watershed. A batch incubation study was conducted on soils (0-10 cm) collected along a hydrological gradient representing isolated wetland (Center), transient zone (Edge) and pasture upland (Upland), from both grazed and ungrazed areas. Production and consumption potentials of N2O were quantified on soils under four treatments, including (i) ambient condition, and amended with (ii) NO3(-), (iii) glucose-C, and (iv) NO3(-) +glucose-C. The impacts of grazing on N2O production and consumption were not observed. Soils in hydrologically distinct zones responded differently to N2O production and consumption. Under ambient conditions, both production and consumption rates of Edge soils were higher than those observed for Center and Upland soils. Results of amended incubations suggested NO3(-) was a key factor limiting N2O production and consumption rates in all hydrological zones. Over 5-d incubation with NO3(-) amendment, cumulative production and consumption of N2O for Center soils were 1.6 and 3.3 times higher than Edge soils, and 3.6 and 7.6 times higher than Upland soils, respectively. However, cumulative N2O net production for Edge soils was the highest, with 2 to 3 times higher than Upland and Center soils. Our results suggest that the transient areas between wetland and upland are likely to be "hot spots" of N2O emissions in this ecosystem. Wetlands within agricultural landscapes can potentially function to reduce both NO3(-) leaching and N2O emissions

  18. Understanding the hydrologic and geochemical control of regolith formation on shale in a hilly landscape

    NASA Astrophysics Data System (ADS)

    Xiao, D.; Brantley, S.; Li, L.

    2017-12-01

    Chemical weathering transforms rock to soil and determine soil texture, bedrock depth, and soil hydrological properties. At the Shale Hills watershed in central Pennsylvania, field evidence indicated that the regolith depth, hydrologic processes, and chemical depletion are different at the two aspects. Current regolith formation models considering reactive transport processes have a limitation in coupling complex and evolving hydrodynamic conditions. We hypothesize that deeper regolith forms when more water flushes dissolved mass out of the system. The hypothesis is tested by developing a two-dimensional regolith formation model at the hillslope scale using measured mineral composition and hydrologic properties at Shale Hills using CrunchFlow. A 2-D hillslope domain was setup to simulate hydrogeochemical processes at north and south aspects and to understand the evolution of hydrodynamics, rock properties, and extent of chemical reactions. The bedrock has the primary minerals of quartz, illite, chlorite, calcite, and pyrite; goethite and kaolinite precipitated as secondary minerals. The permeability, mass transfer, and groundwater table depth were constrained by field measurement. We implemented different recharge rates on north and south aspects based on the annually averaged fluxes from a current reanalysis using a hydrologic model. The simulation started from a homogeneous bedrock composition at 10,000 years ago. After 10,000 years' weathering, the south facing aspect with small recharge rate has a shallower soil and regolith. The simulation output indicates the formation of a shallow and a deep groundwater, based on the formation of lateral flow that connects to the stream. One is at the interface between high permeability soil zone and low permeability regolith zone, forming a relatively high-velocity perched groundwater layer. The remnant water infiltrates into the deeper low permeability zone and forms the regional groundwater layer. Because of high

  19. Hydrological Flowpaths and Their Controls at LBA Biogeochemistry Study Sites - Communalities, Contrasts and Representativeness

    NASA Astrophysics Data System (ADS)

    Elsenbeer, H.; Johnson, M.; Neill, C.

    2006-12-01

    Several LBA projects have focused on nutrient fluxes within and nutrient export from forested terra firme headwater catchments. Their physiographic settings encompass the most common soil types of Amazonia, i.e., Oxisols and Ultisols, and share the topography typical of recently dissected landscapes. We will explore to which degree pedological and geomorphological similarities among sites in Amazonas, Mato Grosso and Rondonia extend to near-surface hydrological behavior. We will then interpret differences in nutrient dynamics in terms of contrasting hydrological flowpaths and soil chemistry. Special attention will be given to the usefulness, or lack thereof, of soil taxonomic information as a predictor of near-surface hydrological and hydrochemical behavior in Amazonia, and to the role of riparian zones in masking terra firme processes. Against this background, we will evaluate the representativeness of these LBA sites in the Amazonian context.

  20. Soil Systems for Upscaling Saturated Hydraulic Conductivity (Ksat) for Hydrological Modeling in the Critical Zone

    USDA-ARS?s Scientific Manuscript database

    Successful hydrological model predictions depend on appropriate framing of scale and the spatial-temporal accuracy of input parameters describing soil hydraulic properties. Saturated soil hydraulic conductivity (Ksat) is one of the most important properties influencing water movement through soil un...