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Sample records for hyporheic zone affect

  1. Modeling hyporheic zone processes

    USGS Publications Warehouse

    Runkel, Robert L.; McKnight, Diane M.; Rajaram, Harihar

    2003-01-01

    Stream biogeochemistry is influenced by the physical and chemical processes that occur in the surrounding watershed. These processes include the mass loading of solutes from terrestrial and atmospheric sources, the physical transport of solutes within the watershed, and the transformation of solutes due to biogeochemical reactions. Research over the last two decades has identified the hyporheic zone as an important part of the stream system in which these processes occur. The hyporheic zone may be loosely defined as the porous areas of the stream bed and stream bank in which stream water mixes with shallow groundwater. Exchange of water and solutes between the stream proper and the hyporheic zone has many biogeochemical implications, due to differences in the chemical composition of surface and groundwater. For example, surface waters are typically oxidized environments with relatively high dissolved oxygen concentrations. In contrast, reducing conditions are often present in groundwater systems leading to low dissolved oxygen concentrations. Further, microbial oxidation of organic materials in groundwater leads to supersaturated concentrations of dissolved carbon dioxide relative to the atmosphere. Differences in surface and groundwater pH and temperature are also common. The hyporheic zone is therefore a mixing zone in which there are gradients in the concentrations of dissolved gasses, the concentrations of oxidized and reduced species, pH, and temperature. These gradients lead to biogeochemical reactions that ultimately affect stream water quality. Due to the complexity of these natural systems, modeling techniques are frequently employed to quantify process dynamics.

  2. The role of the hyporheic zone across stream networks

    Treesearch

    Steven M. Wondzell

    2011-01-01

    Many hyporheic papers state that the hyporheic zone is a critical component of stream ecosystems, and many of these papers focus on the biogeochemical effects of the hyporheic zone on stream solute loads. However, efforts to show such relationships have proven elusive, prompting several questions: Are the effects of the hyporheic zone on stream ecosystems so highly...

  3. Temporal Hyporheic Zone Response to Water Table Fluctuations.

    PubMed

    Malzone, Jonathan M; Anseeuw, Sierra K; Lowry, Christopher S; Allen-King, Richelle

    2016-03-01

    Expansion and contraction of the hyporheic zone due to temporal hydrologic changes between stream and riparian aquifer influence the biogeochemical cycling capacity of streams. Theoretical studies have quantified the control of groundwater discharge on the depth of the hyporheic zone; however, observations of temporal groundwater controls are limited. In this study, we develop the concept of groundwater-dominated differential hyporheic zone expansion to explain the temporal control of groundwater discharge on the hyporheic zone in a third-order stream reach flowing through glacially derived terrain typical of the Great Lakes region. We define groundwater-dominated differential expansion of the hyporheic zone as: differing rates and magnitudes of hyporheic zone expansion in response to seasonal vs. storm-related water table fluctuation. Specific conductance and vertical hydraulic gradient measurements were used to map changes in the hyporheic zone during seasonal water table decline and storm events. Planar and riffle beds were monitored in order to distinguish the cause of increasing hyporheic zone depth. Planar bed seasonal expansion of the hyporheic zone was of a greater magnitude and longer in duration (weeks to months) than storm event expansion (hours to days). In contrast, the hyporheic zone beneath the riffle bed exhibited minimal expansion in response to seasonal groundwater decline compared to storm related expansion. Results indicated that fluctuation in the riparian water table controlled seasonal expansion of the hyporheic zone along the planar bed. This groundwater induced hyporheic zone expansion could increase the potential for biogeochemical cycling and natural attenuation.

  4. Determining long time-scale hyporheic zone flow paths in Antarctic streams

    USGS Publications Warehouse

    Gooseff, M.N.; McKnight, Diane M.; Runkel, R.L.; Vaughn, B.H.

    2003-01-01

    hyporheic zones, in which slower biogeochemical reaction rates may affect stream-water chemistry at longer time-scales. Copyright ?? 2003 John Wiley & Sons, Ltd.

  5. Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance

    USGS Publications Warehouse

    Harvey, J.W.; Fuller, C.C.

    1998-01-01

    We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheicflow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/??(s), of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/??(h) = 2.6 hours), and in laboratory batch experiments using streambed sediment (1/?? = 2.7 hours). The modeled depths of subsurface storage zones (d(s) = 4-17 cm) and modeled residence times of water in storage zones (t(s) = 3-12 min) were both consistent with direct measurements in hyporheic flow paths (d(h) = 0-15 cm, and t(h) = 1-25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (f(s) = 8.9%, and f(h) = 9.3%). Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The

  6. Influence of the Hyporheic Zone on Supersaturated Gas Exposure to Incubating Chum Salmon

    SciTech Connect

    Arntzen, Evan V.; Geist, David R.; Murray, Katherine J.; Vavrinec, John; Dawley, Earl M.; Schwartz, Dennis E.

    2009-12-01

    Supersaturated total dissolved gas (TDG) is elevated seasonally in the lower Columbia River, with surface water concentrations approaching 120% saturation of TDG. Chum salmon (Oncorhynchus keta) embryos incubating in nearby spawning areas could be affected if depth-compensated TDG concentrations within the hyporheic zone exceed 103% TDG. The objective of this study was to determine if TDG of the hyporheic zone in two chum salmon spawning areas -- one in a side channel near Ives Island, Washington, and another on the mainstem Columbia River near Multnomah Falls, Oregon -- was affected by the elevated TDG of the surface water. Depth-compensated hyporheic TDG did not exceed 103% at the Multnomah Falls site. However, in the Ives Island area, chum salmon redds were exposed to TDG greater than 103% for more than 600 hours. In response to river depth fluctuations, TDG varied significantly in the Ives Island area, suggesting increased interaction between the hyporheic zone and surface water at that site. We conclude from this study that the interaction between surface water and the hyporheic zone affects the concentration of TDG within the hyporheic zone directly via physical mixing as well as indirectly by altering water chemistry and thus dissolved gas solubility. These interactions are important considerations when estimating TDG exposure within egg pocket environments, facilitating improved exposure estimates, and enabling managers to optimize recovery strategies.

  7. Pyrosequencing Reveal the Genetic Diversity of Bacteria, Archaea, and Fungi in Hyporheic Zones

    NASA Astrophysics Data System (ADS)

    Kim, Heejung; Kaown, Dugin; Lee, Kang-Kun

    2017-04-01

    Hyporheic zones are hot spot to numerically vast and phyrogenitically diverse bacterial, archaea and fungi communities between surface water and groundwater. However, the prokaryotes and eukaryotes in the zones were rarely investigated in detail. To date, little is known about hydroecology of hyporheic zones. Here, we report on use of pyrosequencing technique to eluciate the bacterial, archaeal and fungal community profiles associated with the groundwater and stream water interactions in hyporheic zones. Analyses of the zones microbial communities have revealed that the novel genera and species were associated with hydrogical uniqueness of hyporheic zones. The absent and presence microbial communities in the areas were significantly affected by groundwater and stream water exchange patterns. Our data sugguest that the bacterial, achaeal and fungal communities distribute and gathered within the mixing patterns of hyporheic zones, and that relative scarcity of these microbials in the zones is due to lack of appropiate substrates. Key words: Hyporehic exchange patterns, Pyrosequncing analysis, Bacterial community profiles, Archaeal community profiles, Fungal community profiles.

  8. Coupling of Flow and Biogeochemical Processes Controlling the Environmental Conditions in the Hyporheic Zone: Implications for the Streambed Habitat

    NASA Astrophysics Data System (ADS)

    Andersen, M. S.; Eberhard, S. M.; Rutlidge, H.; Rau, G. C.; Auhl, A.

    2016-12-01

    The hyporheic zone of streams not only connects groundwater and surface water, but is essential for nutrient and carbon cycling and provides crucial habitat for organisms (termed hyporheos). Here we demonstrate how flow (groundwater discharge and hyporheic exchange) and biogeochemical processes interact to form environmental conditions and habitat for hyporheos. This provides the understanding to assess how hyporheic conditions may be altered by changing flow paths caused by flow perturbations such as groundwater pumping. The studied reaches in the Maules Creek Catchment in New South Wales, Australia, comprise intermittent losing, perennial gaining and perennial losing sections, and are therefore well-suited to study how different flow paths affect water quality. Surface water, hyporheic zone pore water (at depths between 0.4 and 0.8 m), and groundwater from monitoring bores, was sampled and analysed for water quality and hyporheos. For each hyporheic site the hydraulic potential for upwelling or down-welling was measured by the vertical hydraulic head difference. Upwelling regional groundwater was generally oxic with detectable nitrate and low DOC (dissolved organic carbon). On the other hand, hyporheic water in down-welling zones became anoxic at shallow depths (< 1 m), with dissolved reduced species such as Fe2+, Mn2+ and NH4+ and no O2, forming a steep vertical redox gradient from the streambed into the sediment. Upwelling hyporheic water (originating from the stream) was found to have a similar hydrochemical signature. These zones did not support habitat for hyporheic invertebrates because metazoan organisms cannot permanently inhabit anoxic environments. No invertebrates were found for Fe2+ concentrations above 2 mg/L. The hyporheos in these zones appeared to be dominated by anaerobic microbes including Fe-reducing bacteria. Our results show that flow conditions affect water quality, which in turn regulates the habitat of hyporheic invertebrates as they will

  9. BEST Engineered Hyporheic Zones: Enhanced Hyporheic Exchange and Resazurin and Nitrate Cycling in Constructed Stream Experiments

    NASA Astrophysics Data System (ADS)

    Herzog, S.; McCray, J. E.; Higgins, C. P.

    2016-12-01

    The hyporheic zone is a hotspot for biogeochemical processing that can attenuate a variety of nonpoint source contaminants in streamwater. However, hyporheic zones in urban and agricultural streams are often degraded and poorly connected with surface water. To increase hyporheic exchange and improve water quality, we introduced engineered streambeds as a stormwater and restoration best management practice. Modifications to streambed hydraulic conductivity and reactivity are termed Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low-permeability sediments to drive efficient hyporheic exchange, and reactive geomedia to increase reaction rates within the hyporheic zone. This research utilized two artificial stream flumes at the Colorado School of Mines in Golden, CO. Each lined stream flume was 15m long, 0.3m wide, had 0.3m sediment depth, and was continuously dosed with recycled water at 0.25 L/s. One flume served as an all-sand control condition, the other featured BEST modules at 1m spacing with a mixture of 70/30 sand/woodchips (v/v). NaCl breakthrough curves were monitored and analyzed using STAMMT-L, a mobile-immobile exchange model, which showed greater hyporheic exchange and residence times in the BEST stream relative to the control. This result is even more apparent when the calibrated models are used to simulate longer stream reaches. Water quality samples at the reach scale also revealed greater attenuation of nitrate and transformation of the indicator compound resazurin into resorufin. Together these compounds demonstrate that BEST can attenuate contaminants that degrade under anaerobic and aerobic conditions, respectively. These experimental results were also compared to previous numerical simulations to evaluate model accuracy, and show reasonable agreement. Altogether, these results show that BEST may be an effective novel best management practice for improving streamwater quality in urban and

  10. Flow regulation effects on the hydrogeochemistry of the hyporheic zone in boreal rivers.

    PubMed

    Siergieiev, D; Widerlund, A; Ingri, J; Lundberg, A; Öhlander, B

    2014-11-15

    River-aquifer interfaces are essential for ecosystem functioning in terms of nutrient exchange and biological habitat, but are greatly threatened world-wide. This study examined geochemical aspects of river-aquifer interaction in one regulated and one unregulated boreal river in Northern Sweden to determine whether the geochemical functioning of the hyporheic zone is affected by hydrological alterations, e.g. regulated river discharge and river-aquifer connectivity. In the unregulated Kalix River, the hyporheic pore water was well-oxygenated with orthogonal fluxes (≈0.6-0.7 m d(-1)) and acted as a sink for Fe, Mn, Al, NH4, and Ca, with fractional losses of 95%, 92%, 45%, 31%, and 15%, respectively. A corresponding elevation in the concentrations of these elements in the hyporheic sediment was observed, with higher saturation indices of Fe-, Mn-, and Al-bearing secondary minerals in hyporheic waters. In the regulated Lule River, hydraulic connectivity at the river-aquifer interface was altered by the presence of a clogging layer (0.04 m d(-1)). In addition, the river discharge oscillated daily, severely reducing exchange flows across the riverbed (<0.01 m d(-1)). As a result, the hyporheic pore water was suboxic, with elevated concentrations of filtered Fe and Mn (fractional increases of ≈3700% and ≈2500%, respectively) and other solutes (NH4, Si, S, Ca). A conceptual model revealed functional differences between geochemical features of the hyporheic zone of regulated and unregulated rivers. Overall, the results showed that hyporheic processes are altered along regulated rivers, with resulting impacts on the geochemistry of riverine, riparian and related marine ecosystems. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Arsenic mobilization in the hyporheic zone of a contaminated stream

    NASA Astrophysics Data System (ADS)

    Nagorski, Sonia A.; Moore, Johnnie N.

    1999-11-01

    Arsenic behavior was examined in a contaminated stream by sampling the dissolved (<0.45 μm) arsenic and metals in surface water, shallow hyporheic zone water, and adjacent ground water. Surface water was oxic and slightly basic, and ground water was anoxic and acidic. Hyporheic zone water had pH values of 6-7, dissolved oxygen concentrations mostly between 0 and 3 mg L-1, and mean concentrations of most metals inbetween surface and ground water sample concentrations. However, arsenic and iron were enriched in the hyporheic zone. Most of the hyporheic zone dissolved arsenic was in the form of As(III), which is considered to be more toxic to some organisms than As(V). In the oxic surface water, 20% of the total dissolved As was found to occur in its reduced form. We hypothesize that upon burial and reduction of Fe-oxyhydroxides in the streambed, sediment-bound arsenic is transferred into the dissolved phase as As(III), and it is subsequently released into the surface water, where it does not immediately reoxidize. A continual flux of reduced As to the surface water maintains As(III) concentrations above that expected in oxygenated surface waters.

  12. Temporal Dynamics of Dissolved Oxygen Concentrations in the Hyporheic Zone.

    NASA Astrophysics Data System (ADS)

    Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

    2016-12-01

    Dissolved oxygen (DO) concentration profiles and DO consumption rates are primary indicators of the redox state of porewaters in the hyporheic zone (HZ). Previous studies (mostly numeric) of reactive solute transport, in the HZ, are steady state and give a fixed, in time, view of the biogeochemical activity and redox state of the HZ. Through the use of a novel, multichannel fiber optic DO measurement system and a robotic surface probe system in a large flume experiment, we have been able to track DO concentration, in the HZ, over time and at high spatial and temporal resolutions never achieved before. Our research shows that in carbon-limited systems (i.e., ones in which organic carbon replenishment is largely episodic), DO concentration profiles and consumption rates will vary as a function of time. As the most readily available organic carbon is consumed, (first near the bed surface/water interface) respiration rates, in that area, will drop and DO will be transported deeper into the HZ. Over time, and lacking either an external source of bioavailable carbon or an alternate electron donor substrate, microbial metabolic activity will slow substantially and the majority of the HZ will be rendered oxic. Hyporheic fluxes affect the time scale of biological reactions resulting in faster growth of the aerobic zone in high-flux systems. While this temporal variability can result in a multitude of DO consumption curves (DO vs. residence time), the careful application of dimensional analysis can collapse the consumption curves to a single characteristic curve that accounts for a wide range of morphology and reactivity.

  13. Exchange pattern in the hyporheic zone of boreal rivers

    NASA Astrophysics Data System (ADS)

    Babak Mojarrad, Brian; Wörman, Anders; Riml, Joakim; Laudon, Hjalmar

    2017-04-01

    Rivers and groundwater are two essential components of hydrological systems which due to their contrasting hydrochemical characteristics plays significantly different roles in transporting water and solutes across the landscape. The interaction between these two components takes place in the hyporheic zone, where the stream water and groundwater mix in permeable sediments below the stream channel. This interaction is driven by processes that occur on different temporal and spatial scales reflecting a spectrum of landscape morphologies ranging from small stream features to large geological structures. The water movement within the catchment is governed by morphology due to its control on the groundwater head. Small scale and large scale topographies cause dynamic and static head variation, respectively. Dynamic head is controlled by the flow velocity whereas static head is regulated by variation in the water surface elevation. Thus, hyporheic exchange models that include both small and large scale topographies provide improved understanding of hyporheic exchange properties. Using COMSOL Multiphysics, the discharge patterns for both local hyporheic and regional catchment-scale groundwater flow were derived for the Krycklan Catchment (Sweden) with respect to the interacting circulation from a wide range of spatial scales in the watershed including those of the stream-bed. The general methodology was to divide the topography into three successive spatial scales: first the whole catchment was modeled in order to obtain the large-scale groundwater flow field. Secondly, the groundwater flow from the whole catchment was used as the boundary condition for a 1×1 km2 subdomain of the catchment. Finally, a 5×5 m2 region was used to represent the flow along the stream and its adjacent hyporheic zone. Due to lack of observation of the small scale topography of the stream bed a spectral approach was used to re-scale the topography from the 100×100 m2 scale to the 5×5 m2 scale

  14. MTBE, TBA, and TAME attenuation in diverse hyporheic zones

    USGS Publications Warehouse

    Landmeyer, J.E.; Bradley, P.M.; Trego, D.A.; Hale, K.G.; Haas, J.E.

    2010-01-01

    Groundwater contamination by fuel-related compounds such as the fuel oxygenates methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and tert-amyl methyl ether (TAME) presents a significant issue to managers and consumers of groundwater and surface water that receives groundwater discharge. Four sites were investigated on Long Island, New York, characterized by groundwater contaminated with gasoline and fuel oxygenates that ultimately discharge to fresh, brackish, or saline surface water. For each site, contaminated groundwater discharge zones were delineated using pore water geochemistry data from 15 feet (4.5 m) beneath the bottom of the surface water body in the hyporheic zone and seepage-meter tests were conducted to measure discharge rates. These data when combined indicate that MTBE, TBA, and TAME concentrations in groundwater discharge in a 5-foot (1.5-m) thick section of the hyporheic zone were attenuated between 34% and 95%, in contrast to immeasurable attenuation in the shallow aquifer during contaminant transport between 0.1 and 1.5 miles (0.1 to 2.4 km). The attenuation observed in the hyporheic zone occurred primarily by physical processes such as mixing of groundwater and surface water. Biodegradation also occurred as confirmed in laboratory microcosms by the mineralization of U- 14C-MTBE and U- 14C-TBA to 14CO2 and the novel biodegradation of U- 14C-TAME to 14CO2 under oxic and anoxic conditions. The implication of fuel oxygenate attenuation observed in diverse hyporheic zones suggests an assessment of the hyporheic zone attenuation potential (HZAP) merits inclusion as part of site assessment strategies associated with monitored or engineered attenuation. ?? 2009 National Ground Water Association.

  15. Physicochemical characteristics of the hyporheic zone affect redd site selection of chum salmon and fall chinook salmon in the Columbia River

    SciTech Connect

    Geist, David R. ); Hanrahan, Timothy P. ); Arntzen, Evan V. ); McMichael, Geoffrey A. ); Murray, Christopher J. ); Chien, Yi-Ju )

    2002-11-01

    Chum salmon Oncorhynchus keta and fall chinook salmon O. tshawytscha spawned at different locations in the vicinity of Ives Island, Washington, a side channel to the Columbia River downstream of Bonneville Dam. We hypothesized that measurements of water depth, substrate size, and water velocity alone would not explain the separation in spawning areas and began a 2-year investigation of physicochemical characteristics of the hyporheic zone. We found that chum salmon spawned in upwelling water that was significantly warmer than the surrounding river water. In contrast, fall chinook salmon constructed redds at downwelling sites where there was no difference in temperature between the river and its bed. Understanding the specific features that are important for chum salmon and fall chinook salmon redd site selection at Ives Island will be useful to resource managers attempting to maximize available spawning habitat for these species within the constraints imposed by other water resource needs.

  16. Single discharge events increase reactive efficiency of the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Fleckenstein, Jan H.

    2017-01-01

    In this study, we investigate the impact of single stream discharge events on water exchange, solute transport, and reactions in the hyporheic zone below a natural in-stream gravel bar. We set up a reactive transport groundwater model with streamflow scenarios that vary by event duration and peak discharge. A steady ambient groundwater flow field is assumed that results in losing, neutral, or gaining stream conditions depending on the stream stage. Across the streambed dissolved oxygen, organic carbon, and nitrate are transported into the subsurface. Additional nitrate is received from upwelling groundwater. Aerobic respiration and denitrification are simulated for scenarios with different stream solute concentrations. Results show that hyporheic exchange flux, solute transport, and consumption increase during events. However, their intensities depend highly on the interplay between event characteristics and ambient groundwater conditions. During events where reversals in the hydraulic gradient occur stream water and solutes infiltrate deeper into the aquifer where they have more time to react. For those events, the reactive efficiency of the hyporheic zone (solute consumption as fraction of influx) for aerobic respiration and denitrification is up to 2.7 and 10 times higher compared to base flow conditions. The fraction of stream nitrate load consumed in the hyporheic zone increases with stream discharge (up to 150 mg/m2/h), but remains below the value under base flow conditions for weak events. Events also increase denitrification of groundwater borne nitrate, but groundwater nitrate flux to the stream decreases by up to 33% due to temporary gradient reversals.

  17. Relating hydraulic conductivity and hyporheic zone biogeochemical processing to conserve and restore river ecosystem services.

    PubMed

    Mendoza-Lera, Clara; Datry, Thibault

    2017-02-01

    River management practices commonly attempt to improve habitat and ecological functioning (e.g. biogeochemical processing or retention of pollutants) by restoring hydrological exchange with the hyporheic zone (i.e. hyporheic flow) in an effort to increase mass transfer of solutes (nutrients, carbon and electron acceptors such as oxygen or nitrate). However, even when hyporheic flow is increased, often no significant changes in biogeochemical processing are detected. Some of these apparent paradox result from the simplistic assumption that there is a direct relationship between hyporheic flow and biogeochemical processing. We propose an alternative conceptual model that hyporheic flow is non-linearly related with biogeochemical processing. Based on the different solute mass transfer and area available for colonization among hydraulic conductivities, we hypothesize that biogeochemical processing in the hyporheic zone follows a Gaussian function depending on hyporheic hydraulic conductivity. After presenting the conceptual model and its domain of application, we discuss the potential implications, notably for river restoration and further hyporheic research.

  18. Quantifying Hydro-biogeochemical Model Sensitivity in Assessment of Climate Change Effect on Hyporheic Zone Processes

    NASA Astrophysics Data System (ADS)

    Song, X.; Chen, X.; Dai, H.; Hammond, G. E.; Song, H. S.; Stegen, J.

    2016-12-01

    The hyporheic zone is an active region for biogeochemical processes such as carbon and nitrogen cycling, where the groundwater and surface water mix and interact with each other with distinct biogeochemical and thermal properties. The biogeochemical dynamics within the hyporheic zone are driven by both river water and groundwater hydraulic dynamics, which are directly affected by climate change scenarios. Besides that, the hydraulic and thermal properties of local sediments and microbial and chemical processes also play important roles in biogeochemical dynamics. Thus for a comprehensive understanding of the biogeochemical processes in the hyporheic zone, a coupled thermo-hydro-biogeochemical model is needed. As multiple uncertainty sources are involved in the integrated model, it is important to identify its key modules/parameters through sensitivity analysis. In this study, we develop a 2D cross-section model in the hyporheic zone at the DOE Hanford site adjacent to Columbia River and use this model to quantify module and parametric sensitivity on assessment of climate change. To achieve this purpose, We 1) develop a facies-based groundwater flow and heat transfer model that incorporates facies geometry and heterogeneity characterized from a field data set, 2) derive multiple reaction networks/pathways from batch experiments with in-situ samples and integrate temperate dependent reactive transport modules to the flow model, 3) assign multiple climate change scenarios to the coupled model by analyzing historical river stage data, 4) apply a variance-based global sensitivity analysis to quantify scenario/module/parameter uncertainty in hierarchy level. The objectives of the research include: 1) identifing the key control factors of the coupled thermo-hydro-biogeochemical model in the assessment of climate change, and 2) quantify the carbon consumption in different climate change scenarios in the hyporheic zone.

  19. Bacterial community dynamics in the hyporheic zone of an intermittent stream

    PubMed Central

    Febria, Catherine M; Beddoes, Paul; Fulthorpe, Roberta R; Williams, D Dudley

    2012-01-01

    The dynamics of in situ bacterial communities in the hyporheic zone of an intermittent stream were described in high spatiotemporal detail. We assessed community dynamics in stream sediments and interstitial pore water over a two-year period using terminal-restriction fragment length polymorphism. Here, we show that sediments remained saturated despite months of drought and limited hydrologic connectivity. The intermittency of stream surface water affected interstitial pore water communities more than hyporheic sediment communities. Seasonal changes in bacterial community composition was significantly associated with water intermittency, phosphate concentrations, temperature, nitrate and dissolved organic carbon (DOC) concentrations. During periods of low- to no-surface water, communities changed from being rich in operational taxonomic units (OTUs) in isolated surface pools, to a few OTUs overall, including an overall decline in both common and rare taxa. Individual OTUs were compared between porewater and sediments. A total of 19% of identified OTUs existed in both porewater and sediment samples, suggesting that bacteria use hyporheic sediments as a type of refuge from dessication, transported through hydrologically connected pore spaces. Stream intermittency impacted bacterial diversity on rapid timescales (that is, within days), below-ground and in the hyporheic zone. Owing to the coupling of intermittent streams to the surrounding watershed, we stress the importance of understanding connectivity at the pore scale, consequences for below-ground and above-ground biodiversity and nutrient processing, and across both short- and long-time periods (that is, days to months to years). PMID:22158391

  20. Dicamptodon tenebrosus larvae within hyporheic zones of intermittent streams in California

    Treesearch

    David Feral; Michael A. Camann; Hartwell H. Welsh Jr.

    2005-01-01

    Lotic ecosystems are increasingly viewed as having three interactive spatial compartments, i.e., channel sediments, the hyporheic zone, and flood plains or riparian areas (Cummins et al. 1983; Ward 1989). The hyporheic zone is the sub-benthic habitat of interstitial spaces between substrate particles in the stream bed, and is the transition zone between surface flow...

  1. Hyporheic zone denitrification: controls on effective reaction depth and contribution to whole-stream mass balance

    USGS Publications Warehouse

    Harvey, Judson W.; Böhlke, John Karl; Voytek, Mary A.; Scott, Durelle; Tobias, Craig R.

    2013-01-01

    Stream denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field. To demonstrate at a field site, we injected 15NO3−, Br (conservative tracer), and SF6 (gas exchange tracer) and compared measured whole-stream denitrification with in situ hyporheic denitrification in shallow and deeper flow paths of contrasting geomorphic units. Hyporheic denitrification accounted for between 1 and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (greater substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance (nirS), and measures of granular surface area and presence of anoxic microzones. The dimensionless product of the reaction rate constant and hyporheic residence time, λhzτhz define a Damköhler number, Daden-hz that was optimal in the subset of hyporheic flow paths where Daden-hz ≈ 1. Optimal conditions exclude inefficient deep pathways transport where substrates are used up and also exclude inefficient shallow pathways that require repeated hyporheic entries and exits to complete the reaction. The whole-stream reaction significance, Rs (dimensionless), was quantified by multiplying Daden-hz by the proportion of stream discharge passing through the hyporheic zone. Together these two dimensionless metrics, one flow-path scale and the other reach-scale, quantify the whole-stream significance of hyporheic denitrification. One consequence is that the effective zone of significant denitrification often differs from the full depth of the hyporheic zone, which is one reason why whole-stream denitrification rates have not previously been explained based on total hyporheic-zone metrics such as hyporheic-zone size or residence time.

  2. Controls on mixing-dependent denitrification in hyporheic zones induced by riverbed dunes: A steady state modeling study

    NASA Astrophysics Data System (ADS)

    Hester, Erich T.; Young, Katie I.; Widdowson, Mark A.

    2014-11-01

    The hyporheic zone is known to attenuate contaminants originating from surface water, yet the ability of the hyporheic zone to attenuate contaminants in upwelling groundwater plumes as they exit to surface water is less understood. We used MODFLOW and SEAM3D to simulate hyporheic flow cells induced by riverbed dunes and upwelling groundwater together with mixing-dependent denitrification of an upwelling nitrate (NO3-) plume. Our base case modeled labile dissolved organic carbon (DOC) and dissolved oxygen (DO) advecting from surface water, and DO and NO3- advecting from groundwater, typical of certain agricultural areas. We conducted sensitivity analyses that showed mixing-dependent denitrification in the hyporheic zone increased with increasing hydraulic conductivity (K), decreasing lower boundary flux, and increasing DOC in surface water or NO3- in groundwater. Surface water DOC, groundwater NO3-, and K were the most sensitive parameters affecting mixing-dependent denitrification. Nonmixing-dependent denitrification also occurred when there was surface water NO3-, and its magnitude was often greater than mixing-dependent denitrification. Nevertheless, mixing-dependent reactions provide functions that nonmixing-dependent reactions cannot, with potential for hyporheic zones to attenuate upwelling NO3- plumes, depending on geomorphic, hydraulic, and biogeochemical conditions. Stream and river restoration efforts may be able to increase mixing-dependent reactions by promoting natural processes that promote bedform creation and augment labile carbon sources.

  3. Flow characteristics control turnover of polar trace organic compounds in the hyporheic zone of an urban lowland river

    NASA Astrophysics Data System (ADS)

    Schaper, Jonas L.; Seher, Wiebke; Jaeger, Anna; Galloway, Jason; Nuetzmann, Gunnar; Putschew, Anke; Lewandowski, Joerg

    2017-04-01

    Hyporheic zones are hypothesized to be important sinks for polar trace organic compounds (TrOCs) in lotic systems, mitigating potential adverse effects of TrOCs on ecosystem functioning and drinking water production. Predicting the fate of TrOCs in the hyporheic zone, however, is difficult as the attenuation rate itself as well as the biogeochemical factors and hydrological conditions controlling attenuation rates are unknown. We used time series of temperature depth profiles as well as heat pulse sensing with a 1D advection dispersion transport model to calculate first order attenuation rates of several TrOCs from equilibrium depth profiles in an urban lowland river in Berlin, Germany. Ring enclosures were used to prohibit horizontal flow and to create distinct biogeochemical conditions within the hyporheic zone. Flow characteristics as well as biogeochemical conditions showed pronounced differences between depth profiles inside and outside of enclosures. TrOCs attenuation rates varied considerably among compounds reflecting their general susceptibility to biodegradation and sorption. While for some compounds such as benzotriazole and sulfamethoxazole redox conditions had an influence on attenuation rates, the fate of other compounds was not affected by biogeochemical parameters. Under loosing conditions, hyporheic zones of urban lowland rivers can thus be regarded as sinks for TrOCs. Their effectiveness is dependent on both, hyporheic exchange characteristics as well as biogeochemical parameters.

  4. Hyporheic Zone Management: Nitrate Removal from Treated Wastewater Effluent using an Engineered Hyporheic Zone as a Bioreactor

    NASA Astrophysics Data System (ADS)

    Esteban, M.; Herzog, S.; Jones, Z.; Sharp, J.

    2014-12-01

    The hyporheic zone (HZ) is a natural bioreactor within streambed sediments. The dynamic interface of streamwater and groundwater creates a diverse microbial community that has potential to provide substantial contaminant removal. However, insufficient water exchange between the stream and the HZ is often a limiting factor for improved streamwater quality. Modular subsurface hydraulic conductivity (K) modifications with the addition of organic carbon substrates have been proposed as a means to increase hyporheic exchange and enhance natural water treatment via denitrification. Subsurface K modification flow paths are well understood from previous computer modeling and tracer testing studies, but treatment capabilities have yet to be tested in physical systems. This research applied chemical and molecular biological techniques to investigate nitrate removal and microbial community structure in a bench-scale stream simulation with subsurface K and carbon modifications. The system received treated wastewater effluent containing soluble nitrogen primarily in the form of nitrate at concentrations fluctuating from 4-7mg/L. To gain insight into denitrification potential and relative microbial activity along hyporheic flow paths, profiles of nitrate fate, total bacterial presence and the density of the denitrification genes (nirS and nirK) were quantified spatially. Nitrate tests showed a decrease from ~7mg/L in the influent to less than 1mg/L along hyporheic flowpaths. This was accompanied by an increase in 16S rRNA copies (representative of total bacterial biomass) from approximately 200000 gene copies in the influent zone to 630000 gene copies in the effluent zone. Also, the bacterial communities had a greater presence in the upper 6cm of the sediment layer with nirS amplifying 4-5 cycles earlier than nirK in the PCR analysis. The nirS gene concentration was nearly an order of magnitude greater in the effluent zone than the carbon modified zone, suggesting that leached

  5. Mercury and methylmercury dynamics in the hyporheic zone of an Oregon stream

    USGS Publications Warehouse

    Hinkle, Stephen R.; Bencala, Kenneth E.; Wentz, Dennis A.; Krabbenhoft, David P.

    2014-01-01

    The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r2=0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems.

  6. No evidence of aquatic priming effects in hyporheic zone microcosms

    NASA Astrophysics Data System (ADS)

    Bengtsson, Mia M.; Wagner, Karoline; Burns, Nancy R.; Herberg, Erik R.; Wanek, Wolfgang; Kaplan, Louis A.; Battin, Tom J.

    2014-06-01

    The priming effect refers to quantitative changes in microbial decomposition of recalcitrant organic matter upon addition of labile organic matter and is a phenomenon that mainly has been reported and debated in soil science. Recently, priming effects have been indicated in aquatic ecosystems and have received attention due to the potential significance for ecosystem carbon budgets. Headwater stream biofilms, which are important degraders of both allochthonous, presumably recalcitrant, organic matter and labile autochthonous organic matter, may be sites where priming effects are important in aquatic environments. We have experimentally tested for priming effects in stream biofilms within microcosms mimicking the stream hyporheic zone. A 13C labeled model allochthonous carbon source was used in combination with different carbon sources simulating autochthonous inputs. We did not detect changes in respiration, removal or incorporation of allochthonous organic matter in response to autochthonous treatments, thus not supporting the occurrence of priming effects under the experimental conditions. This study is the first to address priming effects in the hyporheic zone, and one of very few studies quantitatively assessing aquatic priming effects. The results contrast with existing studies, which highlights the need for quantitative approaches to determine the importance of priming effects in aquatic environments.

  7. No evidence of aquatic priming effects in hyporheic zone microcosms.

    PubMed

    Bengtsson, Mia M; Wagner, Karoline; Burns, Nancy R; Herberg, Erik R; Wanek, Wolfgang; Kaplan, Louis A; Battin, Tom J

    2014-06-05

    The priming effect refers to quantitative changes in microbial decomposition of recalcitrant organic matter upon addition of labile organic matter and is a phenomenon that mainly has been reported and debated in soil science. Recently, priming effects have been indicated in aquatic ecosystems and have received attention due to the potential significance for ecosystem carbon budgets. Headwater stream biofilms, which are important degraders of both allochthonous, presumably recalcitrant, organic matter and labile autochthonous organic matter, may be sites where priming effects are important in aquatic environments. We have experimentally tested for priming effects in stream biofilms within microcosms mimicking the stream hyporheic zone. A (13)C labeled model allochthonous carbon source was used in combination with different carbon sources simulating autochthonous inputs. We did not detect changes in respiration, removal or incorporation of allochthonous organic matter in response to autochthonous treatments, thus not supporting the occurrence of priming effects under the experimental conditions. This study is the first to address priming effects in the hyporheic zone, and one of very few studies quantitatively assessing aquatic priming effects. The results contrast with existing studies, which highlights the need for quantitative approaches to determine the importance of priming effects in aquatic environments.

  8. No evidence of aquatic priming effects in hyporheic zone microcosms

    PubMed Central

    Bengtsson, Mia M.; Wagner, Karoline; Burns, Nancy R.; Herberg, Erik R.; Wanek, Wolfgang; Kaplan, Louis A.; Battin, Tom J.

    2014-01-01

    The priming effect refers to quantitative changes in microbial decomposition of recalcitrant organic matter upon addition of labile organic matter and is a phenomenon that mainly has been reported and debated in soil science. Recently, priming effects have been indicated in aquatic ecosystems and have received attention due to the potential significance for ecosystem carbon budgets. Headwater stream biofilms, which are important degraders of both allochthonous, presumably recalcitrant, organic matter and labile autochthonous organic matter, may be sites where priming effects are important in aquatic environments. We have experimentally tested for priming effects in stream biofilms within microcosms mimicking the stream hyporheic zone. A 13C labeled model allochthonous carbon source was used in combination with different carbon sources simulating autochthonous inputs. We did not detect changes in respiration, removal or incorporation of allochthonous organic matter in response to autochthonous treatments, thus not supporting the occurrence of priming effects under the experimental conditions. This study is the first to address priming effects in the hyporheic zone, and one of very few studies quantitatively assessing aquatic priming effects. The results contrast with existing studies, which highlights the need for quantitative approaches to determine the importance of priming effects in aquatic environments. PMID:24898319

  9. Modeling surface and ground water mixing in the hyporheic zone using MODFLOW and MT3D

    NASA Astrophysics Data System (ADS)

    Lautz, Laura K.; Siegel, Donald I.

    2006-11-01

    We used a three-dimensional MODFLOW model, paired with MT3D, to simulate hyporheic zones around debris dams and meanders along a semi-arid stream. MT3D simulates both advective transport and sink/source mixing of solutes, in contrast to particle tracking (e.g. MODPATH), which only considers advection. We delineated the hydrochemically active hyporheic zone based on a new definition, specifically as near-stream subsurface zones receiving a minimum of 10% surface water within a 10-day travel time. Modeling results indicate that movement of surface water into the hyporheic zone is predominantly an advective process. We show that debris dams are a key driver of surface water into the subsurface along the experimental reach, causing the largest flux rates of water across the streambed and creating hyporheic zones with up to twice the cross-sectional area of other hyporheic zones. Hyporheic exchange was also found in highly sinuous segments of the experimental reach, but flux rates are lower and the cross-sectional areas of these zones are generally smaller. Our modeling approach simulated surface and ground water mixing in the hyporheic zone, and thus provides numerical approximations that are more comparable to field-based observations of surface-groundwater exchange than standard particle-tracking simulations.

  10. Seasonal variation of water quality in a lateral hyporheic zone with response to dam operations

    NASA Astrophysics Data System (ADS)

    Chen, X.; Chen, L.; Zhao, J.

    2015-12-01

    Aquatic environment of lateral hyporheic zone in a regulated river were investigated seasonally under fluctuated water levels induced by dam operations. Groundwater levels variations in preassembled wells and changes in electronic conductivity (EC), dissolved oxygen (DO) concentration, water temperature and pH in the hyporheic zone were examined as environmental performance indicators for the water quality. Groundwater tables in wells were highly related to the river water levels that showed a hysteresis pattern, and the lag time is associated with the distances from wells to the river bank. The distribution of DO and EC were strongly related to the water temperature, indicating that the cold water released from up-reservoir could determine the biochemistry process in the hyporheic zone. Results also showed that the hyporheic water was weakly alkaline in the study area but had a more or less uniform spatial distribution. Dam release-storage cycles were the dominant factor in changing lateral hyporheic flow and water quality.

  11. How does subsurface characterization affect simulations of hyporheic exchange?

    PubMed

    Ward, Adam S; Gooseff, Michael N; Singha, Kamini

    2013-01-01

    We investigated the role of increasingly well-constrained geologic structures in the subsurface (i.e., subsurface architecture) in predicting streambed flux and hyporheic residence time distribution (RTD) for a headwater stream. Five subsurface realizations with increasingly resolved lithological boundaries were simulated in which model geometries were based on increasing information about flow and transport using soil and geologic maps, surface observations, probing to depth to refusal, seismic refraction, electrical resistivity (ER) imaging of subsurface architecture, and time-lapse ER imaging during a solute tracer study. Particle tracking was used to generate RTDs for each model run. We demonstrate how improved characterization of complex lithological boundaries and calibration of porosity and hydraulic conductivity affect model prediction of hyporheic flow and transport. Models using hydraulic conductivity calibrated using transient ER data yield estimates of streambed flux that are three orders of magnitude larger than uncalibrated models using estimated values for hydraulic conductivity based on values published for nearby hillslopes (10(-4) vs. 10(-7) m(2)/s, respectively). Median residence times for uncalibrated and calibrated models are 10(3) and 10(0) h, respectively. Increasingly well-resolved subsurface architectures yield wider hyporheic RTDs, indicative of more complex hyporheic flowpath networks and potentially important to biogeochemical cycling. The use of ER imaging to monitor solute tracers informs subsurface structure not apparent from other techniques, and helps to define transport properties of the subsurface (i.e., hydraulic conductivity). Results of this study demonstrate the value of geophysical measurements to more realistically simulate flow and transport along hyporheic flowpaths.

  12. 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.

  13. Effect of Rapidly Changing River Stage on Uranium Flux through the Hyporheic Zone

    SciTech Connect

    Fritz, Brad G.; Arntzen, Evan V.

    2007-11-01

    At the Hanford Site, the flux of uranium contaminated groundwater into the Columbia River varies according to the dynamic changes in hydraulic gradient caused by fluctuating river stage. The river stage changes in response to operations of dams on the Columbia River. Piezometers were installed in the hyporheic zone to facilitate long term, high frequency measurement of water and uranium fluxes into the Columbia River in response to fluctuating river stage. In addition, measurement of the water level in the near shore unconfined aquifer enhanced the understanding of the relationship between fluctuating river stage and uranium flux. The changing river stage caused head fluctuations in the unconfined aquifer, and resulted in fluctuating hydraulic gradient in the hyporheic zone. Further, influx of river water into the unconfined aquifer caused reduced uranium concentration in near shore groundwater as a result of dilution. Calculated water flux through the hyporheic zone ranged between 0.3 and -0.5 L/min/m2. The flux of uranium through the hyporheic zone exceeded 30 ug/min/m2 during some time periods, but was generally on the order of 3 to 5 ug/min/m2 over the course of this study. It was also found that at this location, the top 20 cm of the hyporheic zone constituted the most restrictive portion of the aquifer, and controlled the flux of water through the hyporheic zone.

  14. Cooling Along Hyporheic Pathlines in a Large River Riparian Zone

    EPA Science Inventory

    Floodplains can contribute to hyporheic cooling and moderation of temperature for rivers, but extent and magnitude are dependent on ground water hydrology. Here we illustrate the controls and dynamics of hyporheic cooling in the ground water of a large river floodplain with field...

  15. Cooling Along Hyporheic Pathlines in a Large River Riparian Zone

    EPA Science Inventory

    Floodplains can contribute to hyporheic cooling and moderation of temperature for rivers, but extent and magnitude are dependent on ground water hydrology. Here we illustrate the controls and dynamics of hyporheic cooling in the ground water of a large river floodplain with field...

  16. Focused groundwater controlled feedbacks into the hyporheic zone during baseflow recession.

    PubMed

    Malzone, Jonathan M; Lowry, Christopher S

    2015-01-01

    Groundwater surface water interaction in the hyporheic zone remains an important challenge for water resources management and ecosystem restoration. In heterogeneous stratified glacial sediments, reach-scale environments contain an uneven distribution of focused groundwater flow occurring simultaneously with diffusely discharging groundwater. This results in a variation of stream-aquifer interactions, where focused flow systems are able to temporally dominate exchange processes. The research presented here investigates the direct and indirect influences focused groundwater discharge exerts on the hyporheic zone during baseflow recession. Field results demonstrate that as diffuse sources of groundwater deplete during baseflow recession, focused groundwater discharge remains constant. During baseflow recession the hyporheic zone is unable to expand, while the high nitrate concentration from focused discharge changes the chemistry of the stream. The final result is a higher concentration of nitrate in the hyporheic zone as this altered surface water infiltrates into the subsurface. This indirect coupling of focused groundwater discharge and the hyporheic zone is unaccounted for in hyporheic studies at this time. Results indicate important implications for the potential reduction of agricultural degradation of water quality.

  17. Hyporheic zone influences on concentration-discharge relationships in a headwater sandstone stream

    NASA Astrophysics Data System (ADS)

    Hoagland, Beth; Russo, Tess A.; Gu, Xin; Hill, Lillian; Kaye, Jason; Forsythe, Brandon; Brantley, Susan L.

    2017-06-01

    Complex subsurface flow dynamics impact the storage, routing, and transport of water and solutes to streams in headwater catchments. Many of these hydrogeologic processes are indirectly reflected in observations of stream chemistry responses to rain events, also known as concentration-discharge (CQ) relations. Identifying the relative importance of subsurface flows to stream CQ relationships is often challenging in headwater environments due to spatial and temporal variability. Therefore, this study combines a diverse set of methods, including tracer injection tests, cation exchange experiments, geochemical analyses, and numerical modeling, to map groundwater-surface water interactions along a first-order, sandstone stream (Garner Run) in the Appalachian Mountains of central Pennsylvania. The primary flow paths to the stream include preferential flow through the unsaturated zone ("interflow"), flow discharging from a spring, and groundwater discharge. Garner Run stream inherits geochemical signatures from geochemical reactions occurring along each of these flow paths. In addition to end-member mixing effects on CQ, we find that the exchange of solutes, nutrients, and water between the hyporheic zone and the main stream channel is a relevant control on the chemistry of Garner Run. CQ relationships for Garner Run were compared to prior results from a nearby headwater catchment overlying shale bedrock (Shale Hills). At the sandstone site, solutes associated with organo-mineral associations in the hyporheic zone influence CQ, while CQ trends in the shale catchment are affected by preferential flow through hillslope swales. The difference in CQ trends document how the lithology and catchment hydrology control CQ relationships.

  18. Comparing the Biogeochemical Potential of Hyporheic Zones Driven by Different River Morphologies

    NASA Astrophysics Data System (ADS)

    Gomez, J. D.; Harvey, J. W.

    2013-12-01

    Channel morphology controls the hydrodynamics of hyporheic exchange and its residence times. As a result, it also constrains the hyporheic zone's biogeochemical processes that transform carbon, nutrients, metals, and contaminants and the hyporheic zone's net effect at the local, reach and watershed scales. Previous studies of different morphologies (e.g., meanders, bars, and smaller bedforms such as dunes) have mainly focused on the amount of exchange or, if biogeochemistry was involved, have been specific to a particular morphology. In this work, we present a quantitative intercomparison of the amount of exchange, residence time distributions (RTDs), and biogeochemical potential for four channel morphologies: ripples, dunes, bars, and meander bends. To this end, simple two-dimensional conceptualizations and semi-analytical solutions for the hyporheic zone's flow and transport are used. In general, all morphologies are characterized by heavy-tail RTDs, implying long-term memory to solute inputs. We hypothesize that even though meander bends induce larger hyporheic exchange per unit length of channel and longer residence times, substrate limitations result in less biogeochemical processing when compared with the cumulative effect of multiple bedforms. The models presented are a function of geometric and physical properties easily measured or constrained with field or remote sensing data. The simplicity of this approach allows for practical calculations of the hyporheic zone's exchange and biogeochemical potential over a broad range of scenarios and morphologies, making it a useful tool for experimental design, sampling, and watershed scale assessment.

  19. One-dimensional flow model of the river-hyporheic zone system

    NASA Astrophysics Data System (ADS)

    Pokrajac, D.

    2016-12-01

    The hyporheic zone is a shallow layer beneath natural streams that is characterized by intense exchange of water, nutrients, pollutants and thermal energy. Understanding these exchange processes is crucial for successful modelling of the river hydrodynamics and morphodynamics at various scales from the river corridor up to the river network scale (Cardenas, 2015). Existing simulation models of hyporheic exchange processes are either idealized models of the tracer movement through the river-hyporheic zone system (e.g. TSM, Bencala and Walters, 1983) or detailed models of turbulent flow in a stream, coupled with a conventional 2D Darcian groundwater model (e.g. Cardenas and Wilson, 2007). This paper presents an alternative approach which involves a simple 1-D simulation model of the hyporheic zone system based on the classical SWE equations coupled with the newly developed porous media analogue. This allows incorporating the effects of flow unsteadiness and non-Darcian parameterization od the drag term in the hyporheic zone model. The conceptual model of the stream-hyporheic zone system consists of a 1D model of the open channel flow in the river, coupled with a 1D model of the flow in the hyporheic zone via volume flux due to the difference in the water level in the river and the hyporheic zone. The interaction with the underlying groundwater aquifer is neglected, but coupling the present model with any conventional groundwater model is straightforward. The paper presents the derivation of the 1D flow equations for flow in the hyporheic zone, the details of the numerical scheme used for solving them and the model validation by comparison with published experimental data. References Bencala, K. E., and R. A. Walters (1983) "Simulation of solute transport in a mountain pool-and-riffle stream- a transient storage model", Water Resources Reseach 19(3): 718-724. Cardenas, M. B. (2015) "Hyporheic zone hydrologic science: A historical account of its emergence and a

  20. Reshaping of the hyporheic zone beneath river restoration structures: Flume and hydrodynamic experiments

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Endreny, Theodore A.

    2013-08-01

    In-channel stream restoration structures readjust surface water hydraulics, streambed pressure, and subsurface hyporheic exchange characteristics. In this study, we conducted flume experiments (pool-riffle amplitude of 0.03 m and wavelengths of 0.5 m) and computational fluid dynamic (CFD) simulations to quantify how restoration structures impacted hyporheic penetration depth, Dp, and hyporheic vertical discharge rate, Qv. Restoration structures were channel-spanning vanes with subsurface footers placed in the gravel bed at each riffle. Hyporheic vertical discharge rate was estimated by analyzing solute concentration decay data, and maximum hyporheic penetration depth was measured as the interface between hyporheic water and groundwater using dye tracing experiments. The CFD was verified with literature-based flume hydraulic data and with Dp and Qz observations, and the CFD was then used to document how Dp and Qz varied with flume discharge, Q, ranging from 1 to 15 L/s (3E + 03 < Re < 5E + 04). Flume experiments and CFD simulations showed that restoration structures increased Qz and decreased Dp, creating a shallower but higher flux hyporheic zone. Qz had a positive linear relationship with Q, while Dp initially grew as Q increased, but then shrunk when a hydraulic jump with low streambed pressured formed downstream of the structure. The restoration structures created counter-acting forces of increased downwelling head due to backwater effects, and increased upwelling due to low streambed pressure and standing waves downstream of the structure.

  1. Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.

    PubMed

    Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

    2015-02-01

    The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC

  2. 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

  3. Freeze core sampling to validate time-lapse resistivity monitoring of the hyporheic zone.

    PubMed

    Toran, Laura; Hughes, Brian; Nyquist, Jonathan; Ryan, Robert

    2013-01-01

    A freeze core sampler was used to characterize hyporheic zone storage during a stream tracer test. The pore water from the frozen core showed tracer lingered in the hyporheic zone after the tracer had returned to background concentration in collocated well samples. These results confirmed evidence of lingering subsurface tracer seen in time-lapse electrical resistivity tomographs. The pore water exhibited brine exclusion (ion concentrations in ice lower than source water) in a sediment matrix, despite the fast freezing time. Although freeze core sampling provided qualitative evidence of lingering tracer, it proved difficult to quantify tracer concentration because the amount of brine exclusion during freezing could not be accurately determined. Nonetheless, the additional evidence for lingering tracer supports using time-lapse resistivity to detect regions of low fluid mobility within the hyporheic zone that can act as chemically reactive zones of importance in stream health.

  4. The transport of manufactured nanoparticles in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Hitchman, A.; Sambrook Smith, G.; Sterling, M.; Blois, G.; Best, J.; Hardy, R. J.; Lead, J.

    2010-12-01

    the bed corresponded with known flow patterns within the hyporheic zone.

  5. Carbon dynamics in the hyporheic zone of a headwater mountain stream in the Cascade Mountains, Oregon

    NASA Astrophysics Data System (ADS)

    Corson-Rikert, Hayley A.; Wondzell, Steven M.; Haggerty, Roy; Santelmann, Mary V.

    2016-10-01

    We investigated carbon dynamics in the hyporheic zone of a steep, forested, headwater catchment western Oregon, USA. Water samples were collected monthly from the stream and a well network during base flow periods. We examined the potential for mixing of different source waters to explain concentrations of DOC and DIC. We did not find convincing evidence that either inputs of deep groundwater or lateral inputs of shallow soil water influenced carbon dynamics. Rather, carbon dynamics appeared to be controlled by local processes in the hyporheic zone and overlying riparian soils. DOC concentrations were low in stream water (0.04-0.09 mM), and decreased with nominal travel time through the hyporheic zone (0.02-0.04 mM lost over 100 h). Conversely, stream water DIC concentrations were much greater than DOC (0.35-0.7 mM) and increased with nominal travel time through the hyporheic zone (0.2-0.4 mM gained over 100 h). DOC in stream water could only account for 10% of the observed increase in DIC. In situ metabolic processing of buried particulate organic matter as well as advection of CO2 from the vadose zone likely accounted for the remaining 90% of the increase in DIC. Overall, the hyporheic zone was a source of DIC to the stream. We suggest that, in mountain stream networks, hyporheic exchange facilitates the transformation of particulate organic carbon buried in floodplains and transports the DIC that is produced back to the stream where it can be evaded to the atmosphere.

  6. Comparison of tracer methods to quantify hydrodynamic exchange within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Engelhardt, I.; Piepenbrink, M.; Trauth, N.; Stadler, S.; Kludt, C.; Schulz, M.; Schüth, C.; Ternes, T. A.

    2011-03-01

    SummaryHydrodynamic exchange between surface-water and groundwater was studied at a river located within the Rhine Valley in Germany. Piezometric pressure heads and environmental tracers such as temperature, stable isotopes, chloride, X-ray contrast media, and artificial sweetener were investigated within the hyporheic zone and river water plume. Vertical profiles of environmental tracers were collected using multi-level wells within the neutral up-gradient zone, beneath the river bed, and within the horizontal proximal and distal down-gradient zone. Infiltration velocities were calculated from pressure heads, temperature fluctuations and gradients. The amount of river water within groundwater was estimated from vertical profiles of chloride, stable isotopes, and persistent pharmaceuticals. Profiles of stable isotopes and chloride reveal the existence of down-welling within the shallow hyporheic zone that is generated by river bed irregularities. Due to down-welling an above-average migration of river water into the hyporheic zone establishes even under upward hydraulic pressure gradients. The investigated environmental tracers could not distinctively display short-time-infiltration velocities representative for flood waves, while average infiltration velocities calculated over several months are uniform displayed. Based on vertical temperature profiles the down-gradient migration of the river water plume could be observed even after long periods of effluent conditions and over a distance of 200 m from the river bank. X-ray contrast media and artificial sweeteners were observed in high concentrations within the proximal zone, but were not detected at a distance of 200 m from the river bank. Using temperature as environmental tracer within the hyporheic zone may result in overestimating the migration of pollutants within the river water plume as the process of natural attenuation will be neglected. Furthermore, temperature was not able to display the effect of down

  7. Thermal dynamic in hyporheic zone response to river temperatures formed by reservoir operations in Xinanjiang River, China

    NASA Astrophysics Data System (ADS)

    Chen, X.; Zhao, J.; Chen, L.; Tao, X.; Zhao, Z.

    2012-12-01

    Understanding heat fluxes through hyporheic zones (HZ) becomes increasingly important as anthropogenic influences and changing climate alter river thermal regimes. The HZ directly interacts with river thermal regimes by storing and releasing heat over a range of timescales. Alteration of HZ can lead to shifts in aquatic species composition and changes in biogeochemical processes. In this study we examine a reach of the Xinanjiang, China downstream of the Xinanjiang Dam. The Xinanjiang Dam introduces a low temperature water (LTW) region to the downstream of a length of 23 km and an area of 9.9 km2, which greatly changes the downstream thermal regime. However, how and to what extent the LTW in stream affect the HZ temperature distribution and, ulteriorly, the full range of the river ecosystem are still not completely understood. We quantify hyporheic exchange and heat transport induced by LTW by field experiments and numerical simulations for coupled groundwater flow and heat transport. Both surface and subsurface water temperature are measured in a study region for model validation. The hydraulic head and water temperature along the water-aquifer interface are considered as the input boundaries for groundwater models. The upwelling water with short streamline paths shows the same temperature pattern as surface water but the temperature of water that comes out from the deep subsurface zones rises much higher and shows a relatively lower variation. However, with the continuing exchange of surface LTW and groundwater, the low temperature spreads over the entire domain. Detailed field characterization and groundwater modeling indicate residence times of hyporheic flux can vary from hours to months. A significant implication is that the LTW released from upstream reservoir contributes to the downstream temperature field and potential degradation of habitats in hyporheic zones.

  8. Tracking tracer breakthrough in the hyporheic zone using time‐lapse DC resistivity, Crabby Creek, Pennsylvania

    USGS Publications Warehouse

    Nyquist, Jonathan E.; Toran, Laura; Fang, Allison C.; Ryan, Robert J.; Rosenberry, Donald O.

    2010-01-01

    Characterization of the hyporheic zone is of critical importance for understanding stream ecology, contaminant transport, and groundwater‐surface water interaction. A salt water tracer test was used to probe the hyporheic zone of a recently re‐engineered portion of Crabby Creek, a stream located near Philadelphia, PA. The tracer solution was tracked through a 13.5 meter segment of the stream using both a network of 25 wells sampled every 5–15 minutes and time‐lapse electrical resistivity tomographs collected every 11 minutes for six hours, with additional tomographs collected every 100 minutes for an additional 16 hours. The comparison of tracer monitoring methods is of keen interest because tracer tests are one of the few techniques available for characterizing this dynamic zone, and logistically it is far easier to collect resistivity tomographs than to install and monitor a dense network of wells. Our results show that resistivity monitoring captured the essential shape of the breakthrough curve and may indicate portions of the stream where the tracer lingered in the hyporheic zone. Time‐lapse resistivity measurements, however, represent time averages over the period required to collect a tomographic data set, and spatial averages over a volume larger than captured by a well sample. Smoothing by the resistivity data inversion algorithm further blurs the resulting tomograph; consequently resistivity monitoring underestimates the degree of fine‐scale heterogeneity in the hyporheic zone.

  9. Hyporheic zone as a bioreactor: sediment heterogeneity influencing biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Perujo, Nuria; Romani, Anna M.; Sanchez-Vila, Xavier

    2017-04-01

    Mediterranean fluvial systems are characterized by frequent periods of low flow or even drought. During low flow periods, water from wastewater treatment plants (WWTPs) is proportionally large in fluvial systems. River water might be vertically transported through the hyporheic zone, and then porous medium acts as a complementary treatment system since, as water infiltrates, a suite of biogeochemical processes occurs. Subsurface sediment heterogeneity plays an important role since it influences the interstitial fluxes of the medium and drives biomass growing, determining biogeochemical reactions. In this study, WWTP water was continuously infiltrated for 3 months through two porous medium tanks: one consisting of 40 cm of fine sediment (homogeneous); and another comprised of two layers of different grain size sediments (heterogeneous), 20 cm of coarse sediment in the upper part and 20 cm of fine one in the bottom. Several hydrological, physicochemical and biological parameters were measured periodically (weekly at the start of the experiment and biweekly at the end). Analysed parameters include dissolved nitrogen, phosphorus, organic carbon, and oxygen all measured at the surface, and at 5, 20 and 40 cm depth. Variations in hydraulic conductivity with time were evaluated. Sediment samples were also analysed at three depths (surface, 20 and 40 cm) to determine bacterial density, chlorophyll content, extracellular polymeric substances, and biofilm function (extracellular enzyme activities and carbon substrate utilization profiles). Preliminary results suggest hydraulic conductivity to be the main driver of the differences in the biogeochemical processes occurring in the subsurface. At the heterogeneous tank, a low nutrient reduction throughout the whole medium is measured. In this medium, high hydraulic conductivity allows for a large amount of infiltrating water, but with a small residence time. Since some biological processes are largely time-dependent, small water

  10. The dynamic response of hyporheic zone redox zonation after surface flow perturbation

    NASA Astrophysics Data System (ADS)

    Kaufman, M.; Zheng, L.; Cardenas, M. B.

    2015-12-01

    As water in a stream or river flows over ripples and other bedforms, differential surface pressures create bedform-induced hyporheic exchange. The oxygen, carbon, and nutrients carried into the bed by the surface water as well as those already existing in the bed material form the basis for microbial communities in the sediment.The resulting dissolved oxygen conditions are a critical control on the ecological function of the hyporheic zone (HZ), from both micro- and macro-biological habitat perspectives. Because hyporheic exchange rates are controlled by surface flow velocity, variations in surface flow have significant impact on the subsurface oxygen conditions. Most rivers are subject to flow velocity variations due to natural forcing including precipitation and variations in evapotranspiration as well as anthropogenic forces like dam releases. We use a large (10m x 0.7m x 0.3m) programmable flume instrumented with a bedform-scale high-resolution planar optode dissolved oxygen imaging system to observe the distribution of oxygenated sediment within the HZ over time. Using this system we characterize the rate at which hyporheic oxygen conditions reconfigure in response to changes in the surface flow velocity, particularly the time it takes for conditions to recover after a pulse of increased flow velocity. In addition, we make use of numerical models to further identify critical response time drivers. With these tools, we develop equations to describe the post-disturbance recovery time as a function of relative pulse magnitude and duration. Using these equations we can predict the time scale over which the hyporheic zone will recover following both natural and anthropogenic flow regime disturbances. Being able to predict the magnitude and duration of dissolved oxygen changes in the wake of flow perturbing events allows us to better understand the impact these disturbances have on the ecology of the hyporheic zone.

  11. Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream

    NASA Astrophysics Data System (ADS)

    Roley, Sarah S.; Tank, Jennifer L.; Williams, Maureen A.

    2012-09-01

    Stream ecotones, specifically the lateral floodplain and subsurface hyporheic zone, can be important sites for nitrogen (N) removal via denitrification, but their role in streams with constructed floodplains has not been examined. We studied denitrification in the hyporheic zone and floodplains of an agriculturally influenced headwater stream in Indiana, USA, that had floodplains added as part of a "two-stage ditch" restoration project. To examine the potential for N removal in the hyporheic zone, we seasonally measured denitrification rates and nitrate concentrations by depth into the stream sediments. We found that nitrate concentration and denitrification rates declined with depth into the hyporheic zone, but denitrification was still measureable to a depth of at least 20 cm. We also measured denitrification rates on the restored floodplains over the course of a flood (pre, during, and post-inundation), and also compared denitrification rates between vegetated and non-vegetated areas of the floodplain. We found that floodplain denitrification rates increased over the course of a floodplain inundation event, and that the presence of surface water increased denitrification rates when vegetation was present. Stream ecotones in midwestern, agriculturally influenced streams have substantial potential for N removal via denitrification, particularly when they are hydrologically connected with high-nitrate surface water.

  12. Dynamics of nitrate production and removal as a function of residence time in the hyporheic zone

    Treesearch

    Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

    2011-01-01

    Biogeochemical reactions associated with stream nitrogen cycling, such as nitrification and denitrification, can be strongly controlled by water and solute residence times in the hyporheic zone (HZ). We used a whole-stream steady state 15N-Iabeled nitrate and conservative tracer addition to investigate the spatial and temporal physiochemical...

  13. The stream subsurface: nitrogen cycling and the cleansing function of hyporheic zones

    Treesearch

    Rhonda Mazza; Steve Wondzell; Jay Zarnetske

    2014-01-01

    Nitrogen is an element essential to plant growth and ecosystem productivity. Excess nitrogen, however, is a common water pollutant. It can lead to algal blooms that deplete the water's dissolved oxygen, creating "dead zones" devoid of fish and aquatic insects.Previous research showed that the subsurface area of a stream, known as the hyporheic...

  14. Optimizing Locations of Stream Restoration Structures to Maximize Hyporheic Zone Path Lengths in a Pool and Riffle Sequence

    NASA Astrophysics Data System (ADS)

    Beck, M.; Lowry, C.

    2016-12-01

    The exchange of surface water and groundwater in the hyporheic zone encourages biogeochemical reactions that naturally attenuate nutrients in streams. Stream restoration efforts often include instream, dam-like structures that increase hyporheic exchange, with the goal of enhancing natural attenuation. The effectiveness of these structures on improving stream quality has been widely researched, however the ideal installation location for these structures along a stream reach to achieve maximum hyporheic exchange must be optimized based on physical and temporal changes in bed forms and hydrologic drivers. Through the use of the finite difference model MODFLOW and particle tracking code MODPATH, the optimal location for emplacement of these stream barriers to maximize the spatial extent of the hyporheic zone was explored. In addition, impacts of seasonal changes in stream stage were also evaluated based on hyporheic zone path lengths. A total of sixteen realizations were created to vary the location of the stream barrier relative to a pool and riffle sequence. Once the ideal location of the barrier was determined, a region of variable groundwater discharge was prescribed to determine the effect of focused discharge. Using MODPATH, imaginary particles identify areas of maximized hyporheic exchange. The results show that the optimal location of the stream restoration structure changes based on stream stage and groundwater discharge zones. The spatial location of the instream barrier relative to zones of concentrated groundwater discharge as well as the location along a pool and riffle sequence has a significant effect on the extent of the hyporheic zone.

  15. The hyporheic zone and its functions: revision and research status in Neotropical regions.

    PubMed

    Mugnai, R; Messana, G; Di Lorenzo, T

    2015-08-01

    The hyporheic zone (HZ), as the connecting ecotone between surface- and groundwater, is functionally part of both fluvial and groundwater ecosystems. Its hydrological, chemical, biological and metabolic features are specific of this zone, not belonging truly neither to surface- nor to groundwater. Exchanges of water, nutrients, and organic matter occur in response to variations in discharge and bed topography and porosity. Dynamic gradients exist at all scales and vary temporally. Across all scales, the functional significance of the HZ relates to its activity and connection with the surface stream. The HZ is a relatively rich environment and almost all invertebrate groups have colonized this habitat. This fauna, so-called hyporheos, is composed of species typical from interstitial environment, and also of benthic epigean and phreatic species. The hyporheic microbiocenose consists in bacteria, archaea, protozoa and fungi. The HZ provides several ecosystem services, playing a pivotal role in mediating exchange processes, including both matter and energy, between surface and subterranean ecosystems, functioning as regulator of water flow, benthic invertebrates refuge and place of storage, source and transformation of organic matter. The hyporheic zone is one of the most threatened aquatic environments, being strongly influenced by human activities, and the least protected by legislation worldwide. Its maintenance and conservation is compelling in order to preserve the ecological interconnectivity among the three spatial dimensions of the aquatic environment. Although several researchers addressed the importance of the hyporheic zone early, and most contemporary stream ecosystem models explicitly include it, very little is known about the HZ of Neotropical regions. From a biological standpoint, hyporheos fauna in Neotropical regions are still largely underestimated. This review focuses on a brief presentation of the hyporheic zone and its functions and significance as

  16. Morphology control on hyporheic zone hydrodynamics: implication on redox and thermal regimes (Invited)

    NASA Astrophysics Data System (ADS)

    Marzadri, A.; Tonina, D.; Bellin, A.

    2013-12-01

    Stream ecotones, specifically riparian and hyporheic zones, received a great deal of attention for their key role in nitrogen removal and in important ecological functions such as habitat and food web maintenance. An important characteristic of these zones is the continuous and dynamic exchange of water and mass with the stream. The interaction between stream flow and stream bed morphology generates spatial and temporal variations of the near-bed energy heads (pumping processes) which originates exchange fluxes between the stream and the underlying hyporheic zone. The ecological status of these zones depends on temporal and spatial patterns of such fluxes. In the present work we discuss the capabilities of a Lagrangian approach to investigate the transport of a passive quantity (temperature) and the transformation of nitrogen within the hyporheic zone of gravel-bed rivers. In particular, the flow field within the hyporheic zone of a gravel-bed river is first obtained analytically with suitable boundary conditions mimicking the pumping effect originating from the interaction between the stream and the bed-forms. Successively transport is modelled with a semi-analytical Lagrangian approach founded on the travel time concept. The hyporheic residence time distribution provides a simple kinematic explanation of the emergence of tailing in the Breakthrough Curves (BTC) observed in field experiments. According to our model, the first three normalized central moments of the residence time distribution can be written as function of the alternate bar dimensionless depth, Y*BM, which is given by the ratio between the mean flow depth and the equilibrium amplitude of the alternate bar. Both are measurable quantities. Another important statistical moment derived from the residence time distribution is the median residence time (τ50): 50% of the downwelled particles of a nonreactive tracer are still within the hyporheic zone after this time has passed since the injection

  17. Diurnal temperature effect on nitrate removal and production efficiency in bedform-induced hyporheic zones

    NASA Astrophysics Data System (ADS)

    Zheng, L.; Cardenas, M. B.

    2014-12-01

    Rivers and aquifers are connected through the hyporheic zone (HZ). Pore water in the subsurface sediments is continuously exchanged with the overlying surface water. The exchange of water, mass and energy occurring along the surface-subsurface interface or within the HZ exerts a strong influence on the quality of both surface and subsurface waters, and fluvial ecology. Moreover, the HZ is rich in biologically active sediment, creating a favorable condition for microbially-facilitated reactions to occur, including organic carbon oxidation (aerobic respiration), nitrification, and denitrification. Inorganic N, especially NO3-, is of concern as a drinking water pollutant and as a cause for eutrophication that threatens ecosystems. The biogeochemical reactions in the HZ could produce or consume NO3- and thus the HZ could serve a nitrate source or sink role in the fluvial system. In addition, hyporheic exchange across the sediment-water interface (SWI) leads to penetration of diel temperature cycles from the river, leading to dynamic HZ temperature pattern. This in turn affects biogeochemical reactions in the HZ. The main objective of this study is to integrate all the processes that occur along the SWI to understand how diurnal temperature variations affect the biogeochemical function of the HZ. We conducted numerical simulations of coupled turbulent open-channel fluid flow, porous fluid flow, porous heat transport and reactive solute transport to study feedbacks and coupling between these processes. We assumed sinusoidally varying diurnal temperature variations. We studied the effects of different mean temperatures and different amplitudes of the diurnal temperature variations on nitrate removal or production efficiency in the HZ. The simulation results show that the average temperature effect on the HZ nitrate source-sink functionality and its associated efficiency has strong dependence on the [NO3-]/[NH4+ ] ratio in the river. However, the effects of the

  18. Stream water bypass through a meander neck, laterally extending the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Peterson, Eric W.; Sickbert, Timothy B.

    2006-12-01

    A meander lobe neck diverts stream water into a hyporheic flow path adjacent to a low gradient stream, Little Kickapoo Creek, Illinois, USA. Hyporheic processes have been well-documented in surface water-groundwater mixing zones underlying and directly adjacent to streams. Alluvial aquifers underlying meander necks provide a further extension of the hyporheic zone. Hydraulic head and temperature data, collected from a set of wells across a meander neck, show stream water moves through the meander neck. The hydraulic gradient across the meander neck (0.006) is greater than the stream gradient (0.003) between the same points, driving the bypass. Rapid subsurface response to elevated stream stage shows a hydraulic connection between the stream and the alluvial aquifer. Temperature data and a Peclet number (Pe) of 43.1 indicate that thermal transport is dominated by advection from the upstream side to the downstream side of the meander neck. The temperature observed within the alluvial aquifer correlates with seasonal temperature variation. Together, the pressure and temperature data indicate that water moves across the meander neck. The inflow of stream water through the meander neck suggests that the meander system may host biogeochemical hyporheic zone processes.

  19. Hyporheic Zone Study at Susquehanna/Shale Hills Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Yu, X.; Duffy, C.; Bhatt, G.; Kumar, M.

    2011-12-01

    Hyporheic Zone (HZ) has been investigated by a wide range of researchers in hydrology, biogeochemistry and ecology to examine the complex ecohydrologic and biogeochemical processes near groundwater and surface water interface. A recent European Geosciences Union (EGU) session explored a definition of the HZ as: the saturated transition zone between surface water and groundwater bodies that derives its specific physical (e.g. water temperature) and biogeochemical (e.g. steep chemical gradients) characteristics from active mixing of surface and groundwater to provide a habitat and refugia for obligate and facultative species. According to the definition, understanding the hydrologic processes in HZ are usually the primary targets for HZ studies. Therefore, an increasing number of publications have reported about modeling strategies of hyporheic exchange flow (HEF). Hydrological studies at hyporheic zone have suggested that conditions and processes controlling HEF vary at different spatial scales from reach-scale to watershed-scale. Also, HEF is highly dynamic at temporal scale. One of the most conspicuous direct impacts is the sub daily fluctuation in groundwater table and stream discharge. Therefore, investigation of the HZ and HEF need abundant high-resolution hydrological data. Another important topic about HZ is temperature. Stream temperature directly influences the metabolic rates, biochemical processes and ecologic behaviors. Accurate and versatile water temperature simulation is necessary for comprehensive environmental assessment of HZ ecosystem. The study focuses on a small experimental watershed, Susquehanna-Shale Hills Critical Zone Observatory (SSHO), which provides a platform for multi-disciplinary research. The multi-scale responses of HEF and stream temperature are simulated in a physics based, fully-coupled watershed modeling strategy facilitated by Penn State Integrated Hydrologic Modeling System (PIHM) which has the potential of simulating the

  20. Factors Controlling Dissolved Oxygen Concentration in the Hyporheic Zone Induced by Fish Egg Nests

    NASA Astrophysics Data System (ADS)

    Ford, A.; Cardenas, M. B.; Kaufman, M.; Zheng, L.; Kessler, A. J.

    2014-12-01

    There is currently limited research on the effects of bed depressions, such as those associated with fish nests, on hyporheic flow and biogeochemistry. A series of flume experiments are in progress, with the aim of understanding the effects of bed depressions on the hyporheic flow of oxygenated water. This study focuses on fish nests, also called redds, which represent a typical depression or scour feature. Previous research has shown that redd topography induces hyporheic circulation, but experiments regarding the oxygen concentration in and around the redds have not been conducted. We are determining the ways in which redds affect dissolved oxygen distribution and how this is controlled by hyporheic flow. The oxygen concentration across the cross-sectional plane of a fish nest is measured using a planar optode and microsensors. Hydraulic measurements include pressure measurements along the sediment-water interface and dye visualization. The redd design is based on a salmonid redd, which consists of a scour feature and a tailspin. The salmonid eggs are found in the tailspin. We hypothesize that the oxygen concentration will be greatest in close proximity to the gravel base of the redd and concentration will decrease with increasing depth and distance from the redd. Higher oxygen concentrations in the tailspin supports the placement of fish eggs within that area as opposed to a less oxygenated area of the streambed. Thus, fish nests are likely bio-engineered to optimize hyporheic flow and biogeochemistry to improve egg viability.

  1. Organic Processing In The Hyporheic Zone And The Effect Of Water Balance Changes

    NASA Astrophysics Data System (ADS)

    Rutlidge, H.; Auhl, A.; Andersen, M. S.; Eberhard, S. M.; Baker, A.

    2016-12-01

    Organic matter processing is a key aspect of aquatic-terrestrial systems and understanding how these processes will be impacted by processes disturbing the water balance such as groundwater drawdown, is important. Utilising the extensive bore network at Maules Creek, Australia, a transect of groundwater, hyporheic, and surface water samples were collected. Samples were analysed for dissolved organic matter (DOM), OM fluorescence by spectroscopy, as well as a range of hydrochemical parameters. PARAFAC was applied to the fluorescence landscapes and a three component model was fitted with the following: (i) protein-like, (ii) unprocessed soil-derived humic/fulvic-like material and (iii) biogeochemically processed humic/fulvic-like material. Regional groundwater could be identified based on low total DOM and an increase in the relative proportion of the protein-like DOM. The presence of regional groundwater was confirmed using the known chemical signature of the regional groundwater. The hyporheic samples showed that as water flowed along hyporheic flow paths, there was an increase in total dissolved organic matter (DOM) along with an increase in the processed humic component relative to the unprocessed component. These findings suggest that the hyporheic zone is an area of biogeochemical processing of organic matter and that this organic matter is mobilised as water flows through these zones. Groundwater drawdown would potentially lead to a decrease in this organic matter processing.

  2. Multi-offset GPR methods for hyporheic zone investigations

    USGS Publications Warehouse

    Brosten, T.R.; Bradford, J.H.; McNamara, J.P.; Gooseff, M.N.; Zarnetske, J.P.; Bowden, W.B.; Johnston, M.E.

    2009-01-01

    Porosity of stream sediments has a direct effect on hyporheic exchange patterns and rates. Improved estimates of porosity heterogeneity will yield enhanced simulation of hyporheic exchange processes. Ground-penetrating radar (GPR) velocity measurements are strongly controlled by water content thus accurate measures of GPR velocity in saturated sediments provides estimates of porosity beneath stream channels using petrophysical relationships. Imaging the substream system using surface based reflection measurements is particularly challenging due to large velocity gradients that occur at the transition from open water to saturated sediments. The continuous multi-offset method improves the quality of subsurface images through stacking and provides measurements of vertical and lateral velocity distributions. We applied the continuous multi-offset method to stream sites on the North Slope, Alaska and the Sawtooth Mountains near Boise, Idaho, USA. From the continuous multi-offset data, we measure velocity using reflection tomography then estimate water content and porosity using the Topp equation. These values provide detailed measurements for improved stream channel hydraulic and thermal modelling. ?? 2009 European Association of Geoscientists & Engineers.

  3. The Role of Hyporheic Zones in Cycling of Carbon and Nitrogen

    NASA Astrophysics Data System (ADS)

    Dwivedi, D.; Steefel, C. I.; Arora, B.; Bisht, G.; Williams, K. H.

    2015-12-01

    Hyporheic zones impact the biogeochemical cycling of carbon and nitrogen, both organic and inorganic. To investigate and develop a predictive understanding of the coupled carbon and nitrogen cycling in the subsurface, we integrated a genome inspired complex reaction network with a high-resolution, three-dimensional, reactive flow and transport code - PFLOTRAN. Three-dimensional reactive flow and transport simulations were performed, making use of the high performance computing platform provided by PFLOTRAN, to describe the biogeochemical zonation developed because of the organic carbon rich sediments and a gradient of dissolved oxygen and pH within the hyporheic zone. We conducted this study in the lower East River, a high elevation catchment in southwestern Colorado. The lower East River site displays a rolling-to-mountainous topography with multiple river meanders that extend over a distance of 11 km. We carried out simulations within two stream meanders to examine (1) the impact of hyporheic exchanges on the biogeochemical zonation of variables and (2) how carbon and nitrogen fluxes at the meander scale influence coupled carbon and nitrogen cycling at the river scale. Three-dimensional model domain - 330 m (X) by 400 m (Y) by 48 m (Z) - was uniformly discretized with 10 m horizontal (X and Y) and 0.25 m vertical (Z) resolutions using structured grids in PFLOTRAN. Simulation results show that the intra-meander hyporheic flow paths and biogeochemical reactions result in the lateral redox zonation, which considerably impact the carbon and nitrogen fluxes into the stream system. The meander-driven hyporheic flow paths enhance the denitrification because of relatively longer residence times in the organic carbon-rich sediments.

  4. Characterizing biogeochemical processes in the hyporheic zone using flume experiments and reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Quick, A. M.; Reeder, W. J.; Farrell, T. B.; Feris, K. P.; Tonina, D.; Benner, S. G.

    2015-12-01

    The hyporheic zones of streams are hotspots of biogeochemical cycling, where reactants from surface water and groundwater are continually brought into contact with microbial populations on the surfaces of stream sediments and reaction products are removed by hyporheic flow and degassing. Using large flume experiments we have documented the complex redox dynamics associated with dune-scale hyporheic flow. Observations, coupled with reactive transport modeling, provide insight into how flow dictates spatio-temporal distribution of redox reactions and the associated consumption and production of reactants and products. Dune hyporheic flow was experimentally produced by maintaining control over flow rates, slopes, sediment grain size, bedform geomorphology, and organic carbon content. An extensive in-situ monitoring array combined with sampling events over time elucidated redox-sensitive processes including constraints on the spatial distribution and magnitude of aerobic respiration, organic carbon consumption, sulfide deposition, and denitrification. Reactive transport modeling reveals further insight into the influence of system geometry and reaction rate. As an example application of the model, the relationship between residence times and reaction rates may be used to generate Damköhler numbers that are related to biogeochemical processes, such as the potential of streambed morphology and nitrate loading to influence production of the greenhouse gas nitrous oxide via incomplete denitrification.

  5. Hydrogeomorphology of the hyporheic zone: stream solute and fine particle interactions with a dynamic streambed

    USGS Publications Warehouse

    Harvey, J.W.; Drummond, J.D.; Martin, R.L.; McPhillips, L.E.; Packman, A.I.; Jerolmack, D.J.; Stonedahl, S.H.; Aubeneau, A.F.; Sawyer, A.H.; Larsen, L.G.; Tobias, C.R.

    2012-01-01

    Hyporheic flow in streams has typically been studied separately from geomorphic processes. We investigated interactions between bed mobility and dynamic hyporheic storage of solutes and fine particles in a sand-bed stream before, during, and after a flood. A conservatively transported solute tracer (bromide) and a fine particles tracer (5 μm latex particles), a surrogate for fine particulate organic matter, were co-injected during base flow. The tracers were differentially stored, with fine particles penetrating more shallowly in hyporheic flow and retained more efficiently due to the high rate of particle filtration in bed sediment compared to solute. Tracer injections lasted 3.5 h after which we released a small flood from an upstream dam one hour later. Due to shallower storage in the bed, fine particles were rapidly entrained during the rising limb of the flood hydrograph. Rather than being flushed by the flood, we observed that solutes were stored longer due to expansion of hyporheic flow paths beneath the temporarily enlarged bedforms. Three important timescales determined the fate of solutes and fine particles: (1) flood duration, (2) relaxation time of flood-enlarged bedforms back to base flow dimensions, and (3) resulting adjustments and lag times of hyporheic flow. Recurrent transitions between these timescales explain why we observed a peak accumulation of natural particulate organic matter between 2 and 4 cm deep in the bed, i.e., below the scour layer of mobile bedforms but above the maximum depth of particle filtration in hyporheic flow paths. Thus, physical interactions between bed mobility and hyporheic transport influence how organic matter is stored in the bed and how long it is retained, which affects decomposition rate and metabolism of this southeastern Coastal Plain stream. In summary we found that dynamic interactions between hyporheic flow, bed mobility, and flow variation had strong but differential influences on base flow retention and

  6. Hydrogeomorphology of the hyporheic zone: Stream solute and fine particle interactions with a dynamic streambed

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Drummond, J. D.; Martin, R. L.; McPhillips, L. E.; Packman, A. I.; Jerolmack, D. J.; Stonedahl, S. H.; Aubeneau, A. F.; Sawyer, A. H.; Larsen, L. G.; Tobias, C. R.

    2012-12-01

    Hyporheic flow in streams has typically been studied separately from geomorphic processes. We investigated interactions between bed mobility and dynamic hyporheic storage of solutes and fine particles in a sand-bed stream before, during, and after a flood. A conservatively transported solute tracer (bromide) and a fine particles tracer (5 μm latex particles), a surrogate for fine particulate organic matter, were co-injected during base flow. The tracers were differentially stored, with fine particles penetrating more shallowly in hyporheic flow and retained more efficiently due to the high rate of particle filtration in bed sediment compared to solute. Tracer injections lasted 3.5 h after which we released a small flood from an upstream dam one hour later. Due to shallower storage in the bed, fine particles were rapidly entrained during the rising limb of the flood hydrograph. Rather than being flushed by the flood, we observed that solutes were stored longer due to expansion of hyporheic flow paths beneath the temporarily enlarged bedforms. Three important timescales determined the fate of solutes and fine particles: (1) flood duration, (2) relaxation time of flood-enlarged bedforms back to base flow dimensions, and (3) resulting adjustments and lag times of hyporheic flow. Recurrent transitions between these timescales explain why we observed a peak accumulation of natural particulate organic matter between 2 and 4 cm deep in the bed, i.e., below the scour layer of mobile bedforms but above the maximum depth of particle filtration in hyporheic flow paths. Thus, physical interactions between bed mobility and hyporheic transport influence how organic matter is stored in the bed and how long it is retained, which affects decomposition rate and metabolism of this southeastern Coastal Plain stream. In summary we found that dynamic interactions between hyporheic flow, bed mobility, and flow variation had strong but differential influences on base flow retention and

  7. Geoelectrical Response of a Hyporheic Zone within a Fractured Sedimentary Bedrock Riverbed

    NASA Astrophysics Data System (ADS)

    Steelman, C. M.; Kennedy, C. S.; Capes, D. C.; Parker, B. L.

    2015-12-01

    Fractured sedimentary bedrock aquifers represent an important source of water for many communities around the world. Although the effective porosities of these aquifers are extremely low relative to their unconsolidated counterparts, the existence of dense networks of interconnected fractures, dissolution-enhanced conduits or karst features can result in productive, yet heterogeneous and anisotropic, flow systems. Fluid-filled fractures remain connected to the porous matrix through advective-diffusive processes. This dual porosity concept is routinely applied to groundwater resource and contaminant transport studies; however, they have only recently been examined in shallow hyporheic environments, where groundwater and surface water influence one another through water and solute exchange across a streambed. Needless to say, there remains a gap in our conceptual understanding of hyporheic zones along rivers where water flowing through high-permeability fracture networks variably interacts with porewater residing in the low-permeability matrix. It is hypothesized that bedrock rivers will possess some measure of a hyporheic zone, albeit one that is governed by a vertical/horizontal fracture network but remains connected to the porous matrix. Hydrogeophysical methods provide a non-invasive means of assessing the scale and variability of critical zone dynamics. Here, we focus on the capacity of surface electrical resistivity for the detection and monitoring of a seasonally variable hyporheic zone at a field station located along the Eramosa River near Guelph, Ontario, Canada. Unlike conventional hydrogeological methods which potentially bias conduction in the fractures, surface resistivity is sensitive to the bulk electrical conductivity of the formation, making it more suited for detection of matrix conditions. Electrical resistivity data was collected along two 50 m profiles along a pool-riffle sequence on a daily to weekly interval from July 2014 to July 2015 and

  8. Response of invertebrates from the hyporheic zone of chalk rivers to eutrophication and land use.

    PubMed

    Pacioglu, Octavian; Moldovan, Oana Teodora

    2016-03-01

    Whereas the response of lotic benthic macroinvertebrates to different environmental stressors is a widespread practice nowadays in assessing the water and habitat quality, the use of hyporheic zone invertebrates is still in its infancy. In this study, classification and regression trees analysis were employed in order to assess the ecological requirements and the potential as bioindicators for the hyporheic zone invertebrates inhabiting four lowland chalk rivers (south England) with contrasting eutrophication levels (based on surface nitrate concentrations) and magnitude of land use (based on percentage of fine sediments load and median interstitial space). Samples of fauna, water and sediment were sampled twice, during low (summer) and high (winter) groundwater level, at depths of 20 and 35 cm. Certain groups of invertebrates (Glossosomatidae and Psychomyiidae caddisflies, and riffle beetles) proved to be good indicators of rural catchments, moderately eutrophic and with high fine sediment load. A diverse community dominated by microcrustaceans (copepods and ostracods) were found as good indicators of highly eutrophic urban streams, with moderate-high fine sediment load. However, the use of other taxonomic groups (e.g. chironomids, oligochaetes, nematodes, water mites and the amphipod Gammarus pulex), very widespread in the hyporheic zone of all sampled rivers, is of limited use because of their high tolerance to the analysed stressors. We recommend the use of certain taxonomic groups (comprising both meiofauna and macroinvertebrates) dwelling in the chalk hyporheic zone as indicators of eutrophication and colmation and, along with routine benthic sampling protocols, for a more comprehensive water and habitat quality assessment of chalk rivers.

  9. Hydrologic dynamics and geochemical responses within a floodplain aquifer and hyporheic zone during Hurricane Sandy

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Kaplan, L. A.; Lazareva, O.; Michael, H. A.

    2014-06-01

    Storms dominate solute export budgets from catchments and drive hydrogeochemical changes in the near-stream environment. We captured near-stream hydrogeochemical dynamics during an intense storm (Hurricane Sandy, October 2012), by instrumenting a riparian-hyporheic zone transect of White Clay Creek in the Christina River Basin Critical Zone Observatory with pressure transducers, redox probes, and pore water samplers. In the floodplain aquifer, preferential vertical flow paths such as macropores facilitated rapid infiltration early in the storm. Water table rose quickly and promoted continuous groundwater discharge to the stream. Floodplain-hillslope topography controlled poststorm aquifer drainage rates, as the broad, western floodplain aquifer drained more slowly than the narrow, eastern floodplain aquifer adjacent to a steep hillslope. These changes in groundwater flow drove heterogeneous geochemical responses in the floodplain aquifer and hyporheic zone. Vertical infiltration in the floodplain and hyporheic exchange in the streambed increased DOC and oxygen delivery to microbially active sediments, which may have enhanced respiration. Resulting geochemical perturbations persisted from days to weeks after the storm. Our observations suggest that groundwater-borne solute delivery to streams during storms depends on unique interactions of vertical infiltration along preferential pathways, perturbations to groundwater geochemistry, and topographically controlled drainage rates.

  10. Investigation of the Hyporheic Zone at the 300 Area,Hanford Site

    SciTech Connect

    Fritz, Brad G.; Kohn, Nancy P.; Gilmore, Tyler J.; McFarland, Doug; Arntzen, Evan V.; Mackley, Rob D.; Patton, Gregory W.; Mendoza, Donaldo P.; Bunn, Amoret L.

    2007-10-01

    The Remediation Task of the Science and Technology (S&T) Project is intended to provide research to meet several objectives concerning the discharge of groundwater contamination into the river at the 300 Area of the Hanford Site. This report serves to meet the research objectives by developing baseline data for future evaluation of remedial technologies, evaluating the effects changing river stage on near-shore groundwater chemistry, improving estimates of contaminant flux to the river, providing estimates on the extent of contaminant discharge areas along the shoreline, and providing data to support computer models used to evaluate remedial alternatives. This report summarizes the activities conducted to date and provides an overview of data collected through July 2006. Recent geologic investigations (funded through other U. S. Department of Energy (DOE) programs) have provided a more complete geologic interpretation of the 300 Area and a characterization of the vertical extent of uranium contamination. Extrapolation of this geologic interpretation into the hyporheic zone is possible, but there is little data to provide corroboration. Penetration testing was conducted along the shoreline to develop evidence to support the extrapolation of the mapping of the geologic facies. In general, this penetration testing provided evidence supporting the extrapolation of the most recent geologic interpretation, but it also provided some higher resolution detail on the shape of the layer than constrains contaminant movement. Information on this confining layer will provide a more detailed estimate of the area of river bed that has the potential to be impacted by uranium discharge to the river from groundwater transport. Water sampling in the hyporheic zone has provided results that illustrate the degree of mixing that occurs in the hyporheic zone. Uranium concentrations measured at individual sampling locations can vary by several orders of magnitude depending on the river and

  11. Groundwater-surface water interactions in the hyporheic zone under climate change scenarios.

    PubMed

    Zhou, Shangbo; Yuan, Xingzhong; Peng, Shuchan; Yue, Junsheng; Wang, Xiaofeng; Liu, Hong; Williams, D Dudley

    2014-12-01

    Slight changes in climate, such as the rise of temperature or alterations of precipitation and evaporation, will dramatically influence nearly all freshwater and climate-related hydrological behavior on a global scale. The hyporheic zone (HZ), where groundwater (GW) and surface waters (SW) interact, is characterized by permeable sediments, low flow velocities, and gradients of physical, chemical, and biological characteristics along the exchange flows. Hyporheic metabolism, that is biogeochemical reactions within the HZ as well as various processes that exchange substances and energy with adjoining systems, is correlated with hyporheic organisms, habitats, and the organic matter (OM) supplied from GW and SW, which will inevitably be influenced by climate-related variations. The characteristics of the HZ in acting as a transition zone and in filtering and purifying exchanged water will be lost, resulting in a weakening of the self-purification capacity of natural water bodies. Thus, as human disturbances intensify in the future, GW and SW pollution will become a greater challenge for mankind than ever before. Biogeochemical processes in the HZ may favor the release of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) under climate change scenarios. Future water resource management should consider the integrity of aquatic systems as a whole, including the HZ, rather than independently focusing on SW and GW.

  12. Denitrification in sediments from the hyporheic zone adjacent to a small forested stream

    USGS Publications Warehouse

    Duff, J.H.; Triska, F.J.

    1990-01-01

    Denitrifying potentials increased with increasing distance from the stream channel. Dissolved oxygen was 100% of the concentration expected in equilibrium with the atmosphere in water obtained from monitoring wells immediately adjacent to the stream but was as low as 7% of the expected value in water 11.4 m inland. Both nitrate and dissolved organic carbon decreased over summer in wells at the base of the alder-forested slope. A 48-h injection of nitrate-amended stream water into hyporheic water 8.4 m inland stimulated nitrous oxide production in the presence of acetylene. Nitrous oxide was generated as nitrate and acetylene were co-transported to a well 13 m down-gradient. Acetylene-block experiments coupled with the chemistry data suggest that denitrification can modify the chemistry of water during passage through the hyporheic zone. -from Authors

  13. Predicting mean residence time and exchange velocity in the hyporheic zone of restored streams

    NASA Astrophysics Data System (ADS)

    Morén, Ida; Wörman, Anders; Riml, Joakim

    2016-04-01

    The hyporheic zones of streams and rivers have been identified as hotspots for biogeochemical reactions in the aquatic environment, making the retention time and exchange velocity of the hyporheic zone essential parameters in the modelling of these processes. However, exact site-specific values of those parameters are often missing in stream restoration projects because there are no well-defined scaling relationships linking them to measurable reach characteristics. In this study we derive semi-analytical solutions for the retention time and exchange velocity in the hyporheic zone. In particular the effect on hyporheic exchange is expressed by the use of physically based models and by superimposing different geomorphologic features of different scales. It is suggested that all exchange phenomena can be modelled as head anomalies expressed with a harmonic distribution along the stream with specific wavelength and head amplitude. The maximum head of an exchange phenomena is either dominated by hydrodynamic or hydrostatic water pressure, depending on the size of the feature causing the exchange. The theory leads to constitutive relationships for exchange velocity and residence time expressed as functions of the distribution of wavelengths, distribution of head amplitude and hydraulic conductivity. In order to validate and evaluate certain empirical coefficients, a number of Rhodamine WT tracer tests were performed in a partly restored agricultural stream in the south of Sweden called the Tullstorps brook. To evaluate the tracer test in sections where remediation actions have been undertaken we used the method of temporal moments. In conjunction with the tracer tests a characterisation of the stream was carried out where hydraulic conductivity of the streambed and stream morphology was measured. The study verifies that the residence time in the hyporheic zone decreases with the maximum hydraulic head of the largest (dominating) geomorphic feature of the reach, and

  14. Time-Scales of Storm Flow Response in the Stream and Hyporheic Zone of a Small, Steep Forested Catchment - Contrasting the Potential Contributions from the Hillslope, Riparian-Hyporheic Zones, and the Stream Channel

    NASA Astrophysics Data System (ADS)

    Wondzell, S. M.; Corson-rikert, H.; Haggerty, R.

    2016-12-01

    Storm-flow responses of small catchments are widely studied to identify water sources and mechanisms routing water through catchments. These studies typically observe rapid responses to rainfall with peak concentrations of many chemical constituents occurring on rising leg of the hydrograph. To explain this, some conceptual models suggest that stream water early in storm periods is dominated by riparian water sources with hillslope water sources dominating later in the storm. We examined changes in both stream and hyporheic water chemistry during a small, autumn storm in a forested mountain catchment to test this conceptual model. Our study site was located in WS01 at the H.J. Andrews Experimental Forest, in Oregon, USA. The watershed has a narrow valley floor, always less than 15 m wide and occasionally interrupted by narrow, constrained bedrock sections. The valley floor has a longitudinal gradient of approximately 14%. Hyporheic water tends to flow parallel the valley axis and flow paths change little with changes in stream discharge, even during storm events. A well network is located in a 30-m reach near the bottom of the watershed. We sampled the stream, 9 hyporheic wells, and a hillslope well for DOC, DIC, Cl-, and NO3- during the storm. As expected, concentrations of DOC and NO3- increased rapidly on the rising leg of the hydrograph in both the stream and the hyporheic wells. However, the stream always had higher concentrations of DOC, and lower concentrations of NO3-, than did either the hillslope well or the hyporheic wells. These data suggest that the riparian/hyporheic zone is not a likely source of water influencing stream water chemistry on the rising leg of the hydrograph. These data agree with median travel time estimates of water flowing along hyporheic flow paths - it takes many 10s of hours for water to move from the riparian/hyporheic zone to the stream - a time scale that is far too slow to explain the rapid changes observed on the rising leg

  15. Stream discharge events increase the reaction efficiency of the hyporheic zone of an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

    Fleckenstein, J. H.; Trauth, N.; Schmidt, C.

    2015-12-01

    Streambed structures such as dunes, pool-riffles or bars enhance the exchange of stream water and solutes with the subsurface, the hyporheic zone. Prior studies have evaluated the factors which control hyporheic exchange and biogeochemical processes for steady state hydrological conditions using numerical models. However, the impact of natural discharge variability on water and solute exchange, creating hydraulically specific conditions for the reactions in the shallow streambed, has not been studied so far. In our study, we set up a transient flow and reactive transport model to elucidate the impact of single stream discharge events on water exchange, solute transport and reactions within the hyporheic zone of an in-stream gravel bar. The discharge events were varied by their duration and the maximum stream discharge. Temporally variable hydraulic heads were assigned as hydraulic head boundary conditions at the top of the reactive groundwater model MIN3P. A steady ambient groundwater flow field was introduced by lateral upstream and downstream hydraulic head boundaries, generating in combination with the stream water level, losing, neutral, or gaining stream conditions. Stream water borne dissolved oxygen, dissolved organic carbon and nitrate can infiltrate into the modelling domain across the top boundary and can react with each other by aerobic respiration and denitrification. Our results show that water and solute exchange through the hyporheic zone (only stream water that infiltrates into the subsurface and exfiltrates back to the stream) is highly dependent on the interplay between event characteristics and the ambient groundwater level. In scenarios where the stream discharge shifts the hydraulic system to strong and long-lasting losing conditions, hyporheic flow paths are longer and the extent of the hyporheic zone are deeper than under base flow conditions and small events where gaining conditions prevail. Consequently, stream discharge events may

  16. Stream discharge events increase the reactive efficiency of the hyporheic zone of an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Fleckenstein, Jan H.

    2016-04-01

    Streambed structures such as dunes, pool-riffles or bars enhance the exchange of stream water and solutes with the subsurface, the hyporheic zone. Prior studies have evaluated the factors which control hyporheic exchange and biogeochemical processes for steady state hydrological conditions using numerical models. However, the impact of natural discharge variability on water and solute exchange, creating hydraulically specific conditions for the reactions in the shallow streambed, has received less attention to date. In our study, we set up a transient flow and reactive transport model to elucidate the impact of single stream discharge events on water exchange, solute transport and reactions within the hyporheic zone of an in-stream gravel bar. The discharge events were varied by their duration and the maximum stream discharge. Temporally varying hydraulic heads were assigned as hydraulic head boundary conditions at the top of the reactive groundwater model MIN3P. A steady ambient groundwater flow field was introduced by lateral upstream and downstream hydraulic head boundaries, resulting in losing, neutral, or gaining conditions in the stream with respect to exchange with groundwater. Stream water borne dissolved oxygen, dissolved organic carbon and nitrate can infiltrate across the top of the modelling domain, where aerobic respiration and denitrification are simulated. Our results show that water and solute exchange through the hyporheic zone (only stream water that infiltrates into the subsurface and exfiltrates back to the stream) is highly dependent on the interplay between event characteristics and the ambient groundwater level. In scenarios where the stream discharge shifts the hydraulic system to strong and long-lasting losing conditions, hyporheic flow paths are longer and the extent of the hyporheic zone deeper than under base flow conditions and small hydrologic events where gaining conditions prevail. Consequently, stream discharge events may

  17. Aquatic hyphomycete species are screened by the hyporheic zone of woodland streams.

    PubMed

    Cornut, Julien; Chauvet, Eric; Mermillod-Blondin, Florian; Assemat, Fiona; Elger, Arnaud

    2014-03-01

    Aquatic hyphomycetes strongly contribute to organic matter dynamics in streams, but their abilities to colonize leaf litter buried in streambed sediments remain unexplored. Here, we conducted field and laboratory experiments (slow-filtration columns and stream-simulating microcosms) to test the following hypotheses: (i) that the hyporheic habitat acting as a physical sieve for spores filters out unsuccessful strategists from a potential species pool, (ii) that decreased pore size in sediments reduces species dispersal efficiency in the interstitial water, and (iii) that the physicochemical conditions prevailing in the hyporheic habitat will influence fungal community structure. Our field study showed that spore abundance and species diversity were consistently reduced in the interstitial water compared with surface water within three differing streams. Significant differences occurred among aquatic hyphomycetes, with dispersal efficiency of filiform-spore species being much higher than those with compact or branched/tetraradiate spores. This pattern was remarkably consistent with those found in laboratory experiments that tested the influence of sediment pore size on spore dispersal in microcosms. Furthermore, leaves inoculated in a stream and incubated in slow-filtration columns exhibited a fungal assemblage dominated by only two species, while five species were codominant on leaves from the stream-simulating microcosms. Results of this study highlight that the hyporheic zone exerts two types of selection pressure on the aquatic hyphomycete community, a physiological stress and a physical screening of the benthic spore pool, both leading to drastic changes in the structure of fungal community.

  18. Aquatic Hyphomycete Species Are Screened by the Hyporheic Zone of Woodland Streams

    PubMed Central

    Chauvet, Eric; Mermillod-Blondin, Florian; Assemat, Fiona; Elger, Arnaud

    2014-01-01

    Aquatic hyphomycetes strongly contribute to organic matter dynamics in streams, but their abilities to colonize leaf litter buried in streambed sediments remain unexplored. Here, we conducted field and laboratory experiments (slow-filtration columns and stream-simulating microcosms) to test the following hypotheses: (i) that the hyporheic habitat acting as a physical sieve for spores filters out unsuccessful strategists from a potential species pool, (ii) that decreased pore size in sediments reduces species dispersal efficiency in the interstitial water, and (iii) that the physicochemical conditions prevailing in the hyporheic habitat will influence fungal community structure. Our field study showed that spore abundance and species diversity were consistently reduced in the interstitial water compared with surface water within three differing streams. Significant differences occurred among aquatic hyphomycetes, with dispersal efficiency of filiform-spore species being much higher than those with compact or branched/tetraradiate spores. This pattern was remarkably consistent with those found in laboratory experiments that tested the influence of sediment pore size on spore dispersal in microcosms. Furthermore, leaves inoculated in a stream and incubated in slow-filtration columns exhibited a fungal assemblage dominated by only two species, while five species were codominant on leaves from the stream-simulating microcosms. Results of this study highlight that the hyporheic zone exerts two types of selection pressure on the aquatic hyphomycete community, a physiological stress and a physical screening of the benthic spore pool, both leading to drastic changes in the structure of fungal community. PMID:24441154

  19. Ecohydrological Impacts of Groundwater Drawdown : Effects on Microbial Activity in the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Auhl, A.; Rutlidge, H.; Andersen, M. S.; Eberhard, S. M.; Baker, A.; Holley, C.

    2016-12-01

    Our current understanding of ecohydrological processes in the ecotone between surface water and groundwater - the hyporheic zone - is limited. Groundwater drawdown is a key stressor for many groundwater dependent ecosystems, as groundwater levels are declining globally. It is caused by different perturbations, including agriculture, mine dewatering and climate change. Therefore, there is a pressing need to examine how different ecohydrological systems work under different types of stress. This research aims to investigate the impacts of groundwater drawdown on hyporheic zone microbial activity. For two six week sampling campaigns (winter and summer) at Maules Creek, Namoi, New South Wales, Australia, microbial activity was measured using the cotton strip degradation method. Unprimed cotton canvas was affixed to rulers which were then placed for six weeks in different habitats (dry bar, hyporheic zone and surface waters) at three different water regimes found at different sections of the creek (perennial, ephemeral, and losing). The microbial activity was related to the loss of cotton strip tensile strength. The water regimes were used as proxies for different stages of groundwater drawdown. Key physico-chemical variables were also measured. The preliminary results show that there is a positive correlation between moisture status (i.e. the degree of habitat saturation over six weeks) and microbial activity.This suggests that groundwater drawdown and desaturation of streambed sediments may lead to a decrease in microbial activity and therefore, the recycling of organic carbon and nutrients. This research has local implications for environmental impact assessments and global implications for the assessment and management of ecological impacts of declining shallow groundwater levels.

  20. Engineered Hyporheic Zones as Novel Water Quality Best Management Practice: Flow and Contaminant Attenuation in Constructed Stream Experiments

    NASA Astrophysics Data System (ADS)

    Herzog, S.; McCray, J. E.; Higgins, C. P.

    2015-12-01

    The hyporheic zone is a hotspot for biogeochemical processing that can attenuate a variety of nonpoint source contaminants in streamwater. However, hyporheic zones in urban and agricultural streams are often degraded and poorly connected with surface water. In order to increase hyporheic exchange and improve water quality, we introduced engineered streambeds as a stormwater and restoration best management practice. Modifications to streambed hydraulic conductivity and reactivity are termed Biohydrochemical Enhancement structures for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low- and high-permeability sediments to drive efficient hyporheic exchange, and reactive geomedia to increase reaction rates within the hyporheic zone. This work presents the first physical performance data of BEST modules at the pilot scale. BEST modules were installed in a constructed stream facility at the Colorado School of Mines in Golden, CO. This facility features two 15m artificial streams, which included an all sand control condition alongside the BEST test condition. Streams were continuously operated at a discharge of 1 L/s using recycled water. Time-lapse electrical resistivity surveys demonstrated that BEST modules provided substantially greater hyporheic exchange than the control condition. Water quality samples at the hyporheic and reach scales also revealed greater attenuation of nitrogen, coliforms, and select metals and trace organics by BEST modules relative to the control condition. These experimental results were also compared to previous numerical model simulations to evaluate model accuracy. Together, these results show that BEST may be an effective best management practice for improving streamwater quality in urban and agricultural settings.

  1. From temperature and hydraulic gradients measurements to spatial-temporal energy balance within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Flipo, N.; Berrhouma, A.; Rivière, A.; Goblet, P.

    2016-12-01

    The hyporheic zone plays a significant role for the biogeochemical cycles. The biogeochemical reactions and the ecosystem depend on water temperature. The spatio-temporal energy balance dynamics at the stream-aquifer interface are complex and mainly depend on porous media properties, hydrogeological (direction, magnitude and variability of water exchanges) and temporal variation of river and aquifer temperatures. This study aims to determine the part of the convective and the diffusive fluxes in the energy balance along a hydraulic corridor. A 2D finite element coupled thermo-hydrogeological model (METIS) is used to determine the hydrogeological and thermal parameters of the hyporheic zone and of the underlying aquifers by inversion at five LOcal MOnitoring Stations (LOMOS) and to quantify water and heat exchanges at the local scale. LOMOS are composed of one or two shallow piezometers to monitor the temperature and the hydraulic head variations in the aquifers, two hyporheic zone (HZ) temperature profiles and one water level and temperature monitoring system in the river. This study is applied to the Avenelles basin (46 km²), located 70km east from Paris (France). The basin is composed of a multi-layer aquifer system which consists of two limestone aquifers: the Brie aquifer (Oligocene) and the Champigny aquifer (Eocene) separated by a clayey aquitard. An Optimization script (screening of parameters'space) is developed to determine the optimal parameters combination using the temperature time series measured in different depths in the hyporheic zone. The parameters ranges prescribed in the inversion are defined using both literature values and slug test measurements. The models are calibrated during a high flow period and validated during low flow periods. Eventually the energy balance is calculated as well as stream-aquifer water exchanges for each LOMOS from October 2012 to December 2015. We demonstrate the importance of the knowledge of the structure and

  2. Residence time distributions in sinuosity-driven hyporheic zones and their biogeochemical effects

    NASA Astrophysics Data System (ADS)

    Gomez, Jesus D.; Wilson, John L.; Cardenas, M. Bayani

    2012-09-01

    Hyporheic exchange plays a key role in the biogeochemical evolution of water and in ecosystem functioning at the local, reach, and watershed scales. Residence time is a fundamental metric to describe the possible transformation taking place in this exchange zone. With this in mind, we use a simple conceptual model to explore the residence time distributions (RTDs) of sinuosity-driven hyporheic zones (HZs) and to discriminate the individual effect of sinuosity (σ), valley slope (Jx), hydraulic conductivity (K), aquifer dispersivity (αL), and the biogeochemical timescales (BTSs) that characterize the degradation of dissolved organic carbon in these hydrologic systems. We find that RTDs are characterized by one early mode and a late time power law behavior. For a given aquifer dispersivity, the shape of these distributions is stretched or compressed by changes in Jx, K, and σ, having a strong influence on the net biogeochemical transformations within the HZ. Using BTSs proposed in previous studies and sensitivity analyses, we show the potential of σ, Jx, and K to classify meander HZs as net sinks of nitrates or only modulators of the residence times in the subsurface where nitrate reduction is negligible. These findings can be used as predictive tools to quantify the potential of meanders as biogeochemical reactors at the watershed scale with the aid of remote sensing data and GIS processing techniques. These tools can guide experimental design, suggesting important locations to visit, sample, and/or instrument. Also, hyporheic restoration projects can use them for initial site selection and design of channel modifications.

  3. Rn as a geochemical tool for estimating residence times in the hyporheic zone and its application to biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Gilfedder, Benjamin; Dörner, Sebastian; Ebertshäuser, Marlene Esther; Glaser, Barbara; Klug, Maria; Pittroff, Marco; Pieruschka, Ines; Waldemer, Carolin

    2014-05-01

    The hyporheic zone is at the interface between groundwater and surface water systems. It is also often a geochemical and redox boundary between typically reduced groundwater and oxic surface water. It experiences dynamic physical and chemical conditions as both groundwater fluxes and surface water levels vary in time and space. This can be particularly important for processes such as biogeochemical processing of nutrients and carbon. There has recently been an increasing focus on coupling residence times of surface water in the hyporheic zone with biogeochemical reactions. While geochemical profiles can be readily measured using established geochemical sampling techniques (e.g. peepers), quantifying surface water residence times and flow paths within the hyporheic zone is more elusive. The nobel gas radon offers a method for quantification of surface water residence times in the hyporheic zone. Radon activities are typically low in surface waters due to degassing to the atmosphere and decay. However once the surface water flows into the hyporheic zone radon accumulates along the flow path due to emanation from the sediments. Using simple analytical equations the water residence time can be calculated based on the difference between measured 222Rn activities and 222Rn activities at secular equilibrium, with a maximum limit of about 20 days (depending on measurement precision). Rn is particularly suited to residence time measurements in the hyporheic zone since it does not require addition of tracers to the stream nor does it require complex simulations and assumptions (such as 1D vertical flow) as for temperature measurements. As part of the biogeochemistry course at the University of Bayreuth, we have investigated the coupling of redox processes and water residence times in the hyporheic zone using 222Rn as a tracer for residence time. Of particular interest were nitrate and sulfate reduction and methane and CO2 production. Measurements were made in a sandy section

  4. Comparison of environmental tracer to characterize wastewater mass fluxes into the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Engelhardt, Irina; Barth, Johannes A. C.; Prommer, Henning; Schulz, Manoj; Ternes, Thomas A.; Schüth, Christoph; van Geldern, Robert

    2014-05-01

    Groundwater and surface water are in many cases closely linked components of the water cycle with respect to both quantity and quality. Bank filtrates may eventually be impacted by the infiltration of wastewater-derived pollutants from surface waters. To study the fate of wastewater-derived substances (e.g. X-ray contrast media) in groundwater, different environmental tracers (temperature, stable isotopes, and the artificial sweetener acesulfame) were evaluated in a model-based analysis of a field experiment within the hyporheic and riparian zone of a highly polluted stream in Germany [1,2]. The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zone was compared with the transport of water stable isotopes (δ18O and δ2H), temperature, and hydraulic heads via analytical and numerical approaches. A calibrated conservative transport model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using additional data sets of acesulfame and water stable isotopes collected over 5 months in a stream and groundwater. Surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water-groundwater interactions properly. Acesulfame completely missed to indicate wastewater-related surface water volumes that remain in the hyporheic zone even under stream-gaining conditions. In contrast, under stream-losing conditions, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone [2]. A model sensitivity analysis revealed temperature as the best indicator in terms of mass flux prediction beneath the stream bed

  5. Mixing interfaces, fluxes, residence times and redox conditions of the hyporheic zones induced by dune-like bedforms and ambient groundwater flow

    NASA Astrophysics Data System (ADS)

    Marzadri, Alessandra; Tonina, Daniele; Bellin, Alberto; Valli, Alberto

    2016-02-01

    Recent studies highlighted the importance of the interface between streams and their surrounding sediment, known as the hyporheic zone, where stream waters flow through the alluvium. These pore water fluxes stem from the interaction among streambed morphology, stream hydraulics and surrounding groundwater flow. We analytically model the hyporheic hydraulics induced by a spatially uniform ambient groundwater flow made of a horizontal, underflow, and a vertical, basal, component, which mimics gaining and losing stream conditions. The proposed analytical solution allows to investigate the control of simple hydromorphological quantities on the extent, residence time and redox conditions of the hyporheic zone, and the thickness of the mixing interface between hyporheic and groundwater cells. Our analysis shows that the location of the mixing zone shallows or deepens in the sediment as a function of bedform geometry, surface hydraulic and groundwater flow. The point of stagnation, where hyporheic flow velocities vanish and where the separation surface passes through, is shallower than or coincides with the deepest point of the hyporheic zone only due to underflow. An increase of the ambient flow causes a reduction of the hyporheic zone volume similarly in both losing and gaining conditions. The hyporheic residence time is lognormally distributed under neutral, losing and gaining conditions, with the residence time moments depending on the same set of parameters describing dune morphology and stream flow.

  6. Argon concentration time-series as a tool to study gas dynamics in the hyporheic zone.

    PubMed

    Mächler, Lars; Brennwald, Matthias S; Kipfer, Rolf

    2013-07-02

    The oxygen dynamics in the hyporheic zone of a peri-alpine river (Thur, Switzerland), were studied through recording and analyzing the concentration time-series of dissolved argon, oxygen, carbon dioxide, and temperature during low flow conditions, for a period of one week. The argon concentration time-series was used to investigate the physical gas dynamics in the hyporheic zone. Differences in the transport behavior of heat and gas were determined by comparing the diel temperature evolution of groundwater to the measured concentration of dissolved argon. These differences were most likely caused by vertical heat transport which influenced the local groundwater temperature. The argon concentration time-series were also used to estimate travel times by cross correlating argon concentrations in the groundwater with argon concentrations in the river. The information gained from quantifying the physical gas transport was used to estimate the oxygen turnover in groundwater after water recharge. The resulting oxygen turnover showed strong diel variations, which correlated with the water temperature during groundwater recharge. Hence, the variation in the consumption rate was most likely caused by the temperature dependence of microbial activity.

  7. Oxygen Carbon Dynamics within the Hyporheic Zone of a Headwater Stream

    NASA Astrophysics Data System (ADS)

    Pennington, R.; Haggerty, R.; Wondzell, S. M.; Serchan, S. P.; Reeder, W. J.; Tonina, D.

    2016-12-01

    Streams and rivers influence global carbon fluxes; on an aerial basis, they have disproportionately high export rates compared to land. Various mechanisms exist for the movement of terrestrially derived carbon to the stream network including transport of organic and inorganic carbon with groundwater and hillslope runoff. A secondary process that has received little attention is carbon dynamics of hyporheic flow along flow paths that pass beneath the vegetated riparian zone. Through use of high frequency monitoring of dissolved inorganic carbon and dissolved oxygen we find that the riparian zone is a net source of carbon throughout the year. Increases in DIC relative stream water are generally more than double decreases in O2 on a molar basis. Metabolic quotients of C to O2 are close to 1.0, therefore respiration of dissolved or particulate organic carbon along flow paths would result in an equal magnitude increase in inorganic carbon to decrease in O2. Diffusion from the high CO2 soil atmosphere into hyporheic water has been considered, however 2-D reactive transport modeling using PFLOTRAN indicates that soil diffusion processes are unlikely to produce observed increases in carbon and that alternative transport mechanisms including root respiration or diel water level fluctuations are necessary for mass balance. Results of the analysis will feed into a comprehensive distributed model of the system that explores carbon dynamics at the reach scale.

  8. Influence of streambed hydraulic conductivity on solute exchange with the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Ryan, Robert J.; Boufadel, Michel C.

    2006-11-01

    A conservative solute tracer experiment was conducted in Indian Creek, a small urban stream in Philadelphia, Pennsylvania to investigate the role of subsurface properties on the exchange between streamwater and the hyporheic zone (subsurface surrounding the stream). Sodium Bromide (NaBr) was used as a conservative tracer, and it was monitored in the surface water at two stations and in the upper bed sediments (shallow hyporheic zone extending from 7.5 to 10 cm below the streambed). The hydraulic conductivity ( K) of the upper bed sediments and the lower bed sediments (10 12.5 cm below the streambed) was measured in situ. High tracer concentrations were observed in the upper layer at locations where the hydraulic conductivity of the upper layer was larger than that of the lower layer. Low concentrations in the upper layer were observed in the converse case. A statistically significant relationship between the mass retained in the upper layer and the difference of K values between layers was observed.

  9. Association of Arsenic and Phosphorus with Iron Nanoparticles in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    O'Carroll, Denis; Hartland, Adam; Larsen, Joshua; Andersen, Martin

    2016-04-01

    The role of colloids and nanoparticles in hyporheic zone reactive transport is currently poorly understood, and may play an important role in contaminant mobility. The microbial oxidation of organic matter coupled to reductive iron oxide dissolution is widely recognized as the dominant mechanism driving elevated arsenic (As) concentrations in aquifers. This paper considers the potential of nanoparticles to increase the mobility of As in aquifers, thereby accounting for discrepancies between predicted and observed As transport reported elsewhere. Arsenic, phosphorus, and iron size distributions and natural organic matter association were examined along a flow path from surface water via the hyporheic zone to shallow groundwater. Our analysis demonstrates that the colloidal Fe concentration (>1 kDa) correlates with both colloidal P and colloidal As concentrations. Importantly, increases in the concentration of colloidal P (>1 kDa) were positively correlated with increases in the concentration of nominally dissolved As (<1 kDa), but no correlation was observed between colloidal As and nominally dissolved P. This suggests that P actively competes for adsorption sites on Fe nanoparticles, displacing adsorbed As, thus mirroring their interaction with Fe oxides in the aquifer matrix. Dynamic redox fronts at the interface between streams and aquifers may therefore provide globally widespread conditions for the generation of Fe nanoparticles, a mobile phase for As adsorption currently not a part of reactive transport models.

  10. Biogeochemical cycling at the aquatic-terrestrial interface is linked to parafluvial hyporheic zone inundation history

    NASA Astrophysics Data System (ADS)

    Goldman, Amy E.; Graham, Emily B.; Crump, Alex R.; Kennedy, David W.; Romero, Elvira B.; Anderson, Carolyn G.; Dana, Karl L.; Resch, Charles T.; Fredrickson, Jim K.; Stegen, James C.

    2017-09-01

    The parafluvial hyporheic zone combines the heightened biogeochemical and microbial interactions indicative of a hyporheic region with direct atmospheric/terrestrial inputs and the effects of wet-dry cycles. Therefore, understanding biogeochemical cycling and microbial interactions in this ecotone is fundamental to understanding biogeochemical cycling at the aquatic-terrestrial interface and to creating robust hydrobiogeochemical models of dynamic river corridors. We aimed to (i) characterize biogeochemical and microbial differences in the parafluvial hyporheic zone across a small spatial domain (6 lateral meters) that spans a breadth of inundation histories and (ii) examine how parafluvial hyporheic sediments respond to laboratory-simulated re-inundation. Surface sediment was collected at four elevations along transects perpendicular to flow of the Columbia River, eastern WA, USA. The sediments were inundated by the river 0, 13, 127, and 398 days prior to sampling. Spatial variation in environmental variables (organic matter, moisture, nitrate, glucose, % C, % N) and microbial communities (16S and internal transcribed spacer (ITS) rRNA gene sequencing, qPCR) were driven by differences in inundation history. Microbial respiration did not differ significantly across inundation histories prior to forced inundation in laboratory incubations. Forced inundation suppressed microbial respiration across all histories, but the degree of suppression was dramatically different between the sediments saturated and unsaturated at the time of sample collection, indicating a binary threshold response to re-inundation. We present a conceptual model in which irregular hydrologic fluctuations facilitate microbial communities adapted to local conditions and a relatively high flux of CO2. Upon rewetting, microbial communities are initially suppressed metabolically, which results in lower CO2 flux rates primarily due to suppression of fungal respiration. Following prolonged inundation

  11. Capturing Hot Moments of Carbon Cycling in the Hyporheic Zone of an Intermittent Stream

    NASA Astrophysics Data System (ADS)

    Brandt, T.; Harjung, A.; Vieweg, M.; Butturini, A.; Schmidt, C.; Fleckenstein, J. H.; Sabater, F.

    2016-12-01

    Intermittent streams are increasingly recognized as a factor for underestimating potential CO2 emissions of aquatic ecosystems, because they are neglected during their dry phase. This can be partly attributed to poor understanding of dissolved organic matter (DOM) processing at highly reactive interfaces such as the hyporheic zone (HZ). Here, hydrological transitions drive rapid changes in the spatiotemporal distribution of dissolved oxygen (DO), thus creating hot moments of increased biogeochemical cycling. However, capturing these process-dynamics requires a continuous monitoring of hyporheic pore water at a sufficient temporal and spatial resolution. In order to investigate the transitions between the wet and dry phase, we used a combination of automated pore water sampling and in situ measurements. By combining conventional pumping approaches with recently developed technology we achieved a high resolution multi-scale, quasi continuous monitoring of relevant parameters of the carbon cycle. Our novel approach coupled continuous fluorescence DOM and infrared CO2 sensor measurements with spatially continuous vertical oxygen profiling in situ. A proof-of-concept application was established in a semi-pristine Mediterranean stream during the drying period in summer 2015. Previous sampling campaigns already identified the water level as a driver of DOM composition in the HZ. Once the surface flow switches to subsurface flow, the HZ becomes a sink for aromatic, high molecular weight compounds, while protein-like, autochthonous DOM gets released. Generally, we observed exponential increases in hyporheic CO2 from this point on, co-occurring with a sharp vertical DO gradient as a function of changing hydrological conditions.

  12. 3D Electrical resistivity tomography monitoring of an artificial tracer injected within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Houzé, Clémence; Pessel, Marc; Durand, Veronique

    2016-04-01

    Due to the high complexity level of hyporheic flow paths, hydrological and biogeochemical processes which occur in this mixing place are not fully understood yet. Some previous studies made in flumes show that hyporheic flow is strongly connected to the streambed morphology and sediment heterogeneity . There is still a lack of practical field experiment considering a natural environment and representation of natural streambed heterogeneities will be always limited in laboratories. The purpose of this project is to propose an innovative method using 3D Electrical Resistivity Tomography (ERT) monitoring of an artificial tracer injection directly within the streambed sediments in order to visualize the water pathways within the hyporheic zone. Field experiment on a small stream was conducted using a plastic tube as an injection piezometer and home-made electrodes strips arranged in a rectangular form made of 180 electrodes (15 strips of 12 electrodes each). The injection of tracer (NaCl) lasted approximatively 90 minutes, and 24h monitoring with increasing step times was performed. The physical properties of the water are controlled by CTD probes installed upstream and downstream within the river. Inverse time-lapse tomographs show development and persistence of a conductive water plume around the injection point. Due to the low hydraulic conductivity of streambed sediments (clay and overlying loess), the tracer movement is barely visible, as it dilutes gradually in the pore water. Impact of boundary conditions on inversion results can lead to significant differences on images, especially in the shallow part of the profiles. Preferential paths of transport are not highlighted here, but this experiment allows to follow spatially and temporarily the evolution of the tracer in a complex natural environment .

  13. Structure and seasonal dynamics of hyporheic zone microbial communities in free-stone rivers of the western United States.

    PubMed

    Feris, K P; Ramsey, P W; Frazar, C; Rillig, M C; Gannon, J E; Holben, W E

    2003-08-01

    The hyporheic zone of a river is characterized by being nonphotic, exhibiting chemical/redox gradients, and having a heterotrophic food web based on the consumption of organic carbon entrained from surface waters. Hyporheic microbial communities constitute the base of food webs in these environments and are important for maintaining a functioning lotic ecosystem. While microbial communities of rivers dominated by fine-grained sediments are relatively well studied, little is known about the structure and seasonal dynamics of microbial communities inhabiting the predominantly gravel and cobble hyporheic zones of rivers of the western United States. Here, we present the first molecular analysis of hyporheic microbial communities of three different stream types (based on mean base discharge, substratum type, and drainage area), in Montana. Utilizing 16S rDNA phylogeny, DGGE pattern analysis, and qPCR, we have analyzed the prokaryotic communities living on the 1.7 to 2.36 mm grain-size fraction of hyporheic sediments from three separate riffles in each stream. DGGE analysis showed clear seasonal community patterns, indicated similar community composition between different riffles within a stream (95.6-96.6% similarity), and allowed differentiation between communities in different streams. Each river supported a unique complement of species; however, several phylogenetic groups were conserved between all three streams including Pseudomonads and members of the genera Aquabacterium, Rhodoferax, Hyphomicrobium, and Pirellula. Each group showed pronounced seasonal trends in abundance, with peaks during the Fall. The Hyphomicrobium group was numerically dominant throughout the year in all three streams. This work provides a framework for investigating the effects of various environmental factors and anthropogenic effects on microbial communities inhabiting the hyporheic zone.

  14. The hyporheic zone as a source of dissolved organic carbon and carbon gases to a temperate forested stream

    USGS Publications Warehouse

    Schindler, J.E.; Krabbenhoft, D.P.

    1998-01-01

    The objective of this study was to examine chemical changes in porewaters that occur over small scales (cm) as groundwater flows through the hyporheic zone and discharges to a stream in a temperate forest of northern Wisconsin. Hyporheic-zone porewaters were sampled at discrete depths of 2, 10, 15, 61, and 183 cm at three study sites in the study basin. Chemical profiles of dissolved organic carbon (DOC), CO2, CH4, and pH show dramatic changes between 61 cm sediment depth and the water-sediment interface. Unless discrete samples at small depth intervals are taken, these chemical profiles are not accounted for. Similar trends were observed at the three study locations, despite each site having very different hydraulic-flow regimes. Increases in DOC concentration by an order of magnitude from 61 to 15 cm depth with a corresponding decrease in pH and rapid decreases in the molecular weight of the DOC suggest that aliphatic compounds (likely organic acids) are being generated in the hyporheic zone. Estimated efflux rates of DOC, CO2, and CH4 to the stream are 6.2, 0.79, 0.13 moles m2 d-1, respectively, with the vast majority of these materials produced in the hyporheic zone. Very little of these materials are accounted for by sampling stream water, suggesting rapid uptake and/or volatilization.

  15. Anthropogenic triggers on the hyporheic zone: quantifying groundwater-surface water interaction and the impact on water quality

    NASA Astrophysics Data System (ADS)

    Siirila-Woodburn, E. R.; Steefel, C. I.; Moulton, J. D.; Dwivedi, D.

    2016-12-01

    The hyporheic zone along and below river corridors plays an important role in controlling stream temperature, supplying nutrients to microorganisms, and stimulating biogeochemical reactions. These complex hydrologic and biogeochemical feedbacks naturally regulate water quality, but may be susceptible to the impacts of anthropogenic factors occurring at the regional and watershed scales. For example, the onset of earlier annual snow melt and higher intensity storms due to climate change will likely affect the spatial and temporal distribution of water within a given basin, and with unknown consequences on the interaction and exchange of ground and surface waters along major rivers. To quantify these impacts, a meandering reach of the East River near Crested Butte, Colorado is used in a series of physically based numerical experiments. Ultra-high resolution data from LIDAR and bathymetry sampling campaigns allow for spatial resolution below a half meter to accurately capture the integrated hydrologic dynamics in the floodplain and along hyporheic zones of the river reach. The impact of so-called "hot-spots" and "hot-moments" are explored via benchmarking between numerical codes with both uniform refinement over the domain and adaptive refinement near the meanders. The degree to which fully coupled models are needed (those explicitly accounting for the interaction of groundwater, surface water, and atmospheric exchange) is also quantified by comparing numerical codes with and without this dynamic coupling and with and without simulations including a land surface model. Results demonstrate the potential for up-scaled impacts on significant water resources such as the Colorado River.

  16. Geochemical and Microbial Community Attributes in Relation to Hyporheic Zone Geological Facies.

    PubMed

    Hou, Z; Nelson, W C; Stegen, J C; Murray, C J; Arntzen, E; Crump, A R; Kennedy, D W; Perkins, M C; Scheibe, T D; Fredrickson, J K; Zachara, J M

    2017-09-20

    The hyporheic zone (HZ) is the active ecotone between the surface stream and groundwater, where exchanges of nutrients and organic carbon have been shown to stimulate microbial activity and transformations of carbon and nitrogen. To examine the relationship between sediment texture, biogeochemistry, and biological activity in the Columbia River HZ, the grain size distributions for sediment samples were characterized to define geological facies, and the relationships among physical properties of the facies, physicochemical attributes of the local environment, and the structure and activity of associated microbial communities were examined. Mud and sand content and the presence of microbial heterotrophic and nitrifying communities partially explained the variability in many biogeochemical attributes such as C:N ratio and %TOC. Microbial community analysis revealed a high relative abundance of putative ammonia-oxidizing Thaumarchaeota and nitrite-oxidizing Nitrospirae. Network analysis showed negative relationships between sets of co-varying organisms and sand and mud contents, and positive relationships with total organic carbon. Our results indicate grain size distribution is a good predictor of biogeochemical properties, and that subsets of the overall microbial community respond to different sediment texture. Relationships between facies and hydrobiogeochemical properties enable facies-based conditional simulation/mapping of these properties to inform multiscale modeling of hyporheic exchange and biogeochemical processes.

  17. 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.

  18. Transport of Solutes in Hyporheic Zones with Temperature-Dependent Reversible Sorption

    NASA Astrophysics Data System (ADS)

    Kaufman, M.; Cardenas, M. B.; Zheng, L.

    2014-12-01

    One of the most important processes impacting the mobility of heavy metals in rivers and their hyporheic zones is reversible sorption to sediment. Reversible sorption has been shown to be a temperature dependent process, however the impact of this variability on heavy metal fate and transport, as well as environmental metal concentrations, has not received much attention. In this study we used zinc as an example heavy metal. Previous studies of the impact of temperature on the sorption of zinc on a goethite substrate show a change in partitioning coefficient and thus retardation factor of 10 to over 60 percent with a temperature change from 10 to 25*C, depending on concentration of dissolved zinc in the water. This relationship was extrapolated to estimate the change in reversible sorption of zinc on silicate sand. This change was then utilized within a finite-element model coupling hyporheic fluid flow in porous media with heat transfer and solute transport with reversible sorption to explore the ways in which variations in surface water temperature over varying timescales can drive changes in both zinc sorption and dissolved zinc fluxes at the bedform scale. These linked processes are of fundamental importance when considering the number of different ways in which surface water temperatures can be varied through both human and non-human activities.

  19. Hydrology controls dissolved organic matter export and composition in an Alpine stream and its hyporheic zone

    PubMed Central

    Fasching, Christina; Ulseth, Amber J.; Schelker, Jakob; Steniczka, Gertraud

    2015-01-01

    Abstract 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. PMID:27478248

  20. Storage and Transformation of Artificial and Natural Salmon-Derived Nutrients in the Hyporheic Zone of a Southeast Alaska Stream

    NASA Astrophysics Data System (ADS)

    Marshall, M. C.; Edwards, R. T.; Hall, R. O.; Norberg, E. C.

    2005-05-01

    Adding nutrients in organic pellets (analogs) or salmon carcasses (SDN) is one strategy resource managers use to enhance productivity in streams where natural salmon nutrient subsidies have been reduced. We compared hyporheic storage and transformation of nutrients from carcasses to those from analogs added to surface water of two tributaries of a salmon stream in Southeast Alaska. Hyporheic sediments responded differently to the two sources with some responses detectable the following summer. Average hyporheic and phreatic SRP concentrations in the analog treatment were 2.5 and 3.5 times greater, respectively, than controls one month after the August additions. Subsurface SRP was again higher the following spring and summer in the analog treatment. Surface water SRP was higher in the analog treatment in late summer a year after the addition. Respiration in phreatic zones in analog and control reaches remained under 1.1 mg DO L sediment-1 h-1. However, respiration rates were elevated in phreatic zones in the carcass treatment reach (3.0 mg DO L sediment-1 h-1) the summer after the addition, suggesting delayed use of stored carcass carbon. These results support the hypothesis that hyporheic zones provide long-term storage and remobilization of SDN thereby enhancing stream productivity in subsequent years.

  1. Modeling the influence of varying hydraulic conditions on aerobic respiration and denitrification in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Trauth, N.; Schmidt, C.; Fleckenstein, J. H.

    2013-12-01

    Exchange of water and solutes across the stream-sediment interface is an important control for biogeochemical transformations in the hyporheic zone (HZ) with measurable impacts on nutrient cycling and solute attenuation in fluvial systems. Here we investigate the interplay between turbulent stream flow and HZ flow under various hydraulic conditions applied to two cases: a) three-dimensional generic pool-riffle sequences with different morphological properties, and b) a real mid-stream gravel-bar. Stream flow is simulated by the open source computational fluid dynamics (CFD) software OpenFOAM which provides the hydraulic head distribution at the streambed. It is sequentially coupled to the top of the groundwater model code MIN3P, simulating flow, solute transport, aerobic respiration (AR) and denitrification (DN) in the HZ. Flow in the HZ is directly influenced by the hydraulic head distribution at the streambed surface and the ambient groundwater flow. Three reactive transport scenarios are considered: 1) stream water as the primary source of dissolved oxygen (DO), nitrate (NO3) and dissolved organic carbon (DOC), 2) upwelling groundwater as an additionally source of NO3, and 3) upwelling groundwater as an additional source of DO in various concentrations. Results show an increase in hyporheic exchange flow for increasing stream discharge with a concurrent decrease in residence time. The fraction of circulating stream water through the HZ is in the range of 1x10-5 to 1x10-6 per unit stream length, decreasing with increasing discharge. Ambient groundwater flow in both the up- and downwelling direction diminishes significantly the hyporheic exchange flow and extent. Biogeochemical processes in the HZ are strongly controlled by ambient groundwater flow, even more so than by changes in stream discharge. AR and DN efficiencies of the HZ are significantly reduced by up- and downwelling groundwater and are positively correlated with median residence times. AR occurs in

  2. Effects of augmentation of coarse particulate organic matter on metabolism and nutrient retention in hyporheic sediments

    Treesearch

    C.L. Crenshaw; H.M. Valett; J.R. Webster

    2002-01-01

    1. Metabolic and biogeochemical processes in hyporheic zones may depend on inputs of coarse particulate organic matter. Our research focused on how differing quantity and quality of organic matter affects metabolism and nutrient retention in the hyporheic zone of a first-order Appalachian stream. 2. Sixteen plots were established on a tributary of Hugh White Creek, NC...

  3. Residence time control on hot moments of net nitrate production and uptake in the hyporheic zone

    USGS Publications Warehouse

    Briggs, Martin A.; Lautz, Laura K.; Hare, Danielle K.

    2014-01-01

    moments of net production and uptake, enhancing NO3- production as residence times approach the anaerobic threshold, and changing zones of net NO3- production to uptake as residence times increase past the net sink threshold. The anaerobic and net sink thresholds for beaver-influenced streambed morphology occur at much shorter residence times (1.3 h and 2.3 h, respectively) compared to other documented hyporheic systems, and the net sink threshold compares favorably to the lower boundary of the anaerobic threshold determined for this system with the new oxygen Damkohler number. The consistency of the residence time threshold values of NO3- cycling in this study, despite environmental variability and disparate morphology, indicates that NO3- hot moment dynamics are primarily driven by changes in physical hydrology and associated residence times.

  4. Stoichiometry of Carbon, Nitrogen, and Phosphorus Regeneration Interactions in the Hyporheic Zones of Arctic Streams Draining Areas of Continuous Permafrost

    NASA Astrophysics Data System (ADS)

    Bowden, W. B.; Greenwald, M. J.; Gooseff, M. N.; McNamara, J. P.; Bradford, J.; Zarnetske, J. P.; Brosten, T.

    2007-12-01

    We used conservative tracer (Rhodamine WT) additions to examine flow paths in two arctic tundra streams with contrasting physical characteristics (high and low gradient, cobble and peat substrate). We installed mini- piezometers in the same streams to examine nutrient patterns longitudinally and with depth. The combination of the flow and nutrient data allowed us to estimate nutrient regeneration rates. In a separate study, we used whole- stream metabolism methods to estimate whole-system photosynthesis and respiration. Comparison to chamber-based metabolism methods showed that most of the whole-system respiration could be attributed to heterotrophic activity in the hyporheic zone. We found that regeneration of C in the hyporheic zone (respiration) was in reasonable stoichiometric agreement with the regeneration of N and P. Increasing temperature and discharge had relatively modest impacts on ecosystem respiration and photosynthesis. We concluded that a substantial portion of the N and P required to support ecosystem photosynthesis in these permafrost-dominated streams can be obtained from hyporheic regeneration. Second, a substantial portion of the excess C (supersaturated CO2) in these streams may be due to hyporheic respiration rather than terrestrial runoff of CO2-laden groundwater. Third, the expected changes in future climate in the arctic foothills may have only a limited effect on the instantaneous rates of C, N, and P processing. The larger effect is likely to be on annual processing rates, due to the longer flowing water season.

  5. Power-law residence time distribution in the hyporheic zone of a 2nd-order mountain stream

    NASA Astrophysics Data System (ADS)

    Haggerty, Roy; Wondzell, Steven M.; Johnson, Matthew A.

    2002-07-01

    We measured the hyporheic residence time distribution in a 2nd-order mountain stream at the H. J. Andrews Experimental Forest, Oregon, and found it to be a power-law over at least 1.5 orders of magnitude in time (1.5 hr to 3.5 d). The residence time distribution has a very long tail which scales as t-1.28, and is poorly characterized by an exponential model. Because of the small power-law exponent, efforts to characterize the mean hyporheic residence time (ts) in this system result in estimates that are scale invariant, increasing with the characteristic advection time within the stream channel (tad). The distribution implies the hyporheic zone has a very large range of exchange timescales, with significant quantities of water and solutes stored over time-scales very much longer than tad. The hyporheic zone in such streams may contribute to short-time fractal scaling in time series of solute concentrations observed in small-watershed studies.

  6. Temperature effect on tert-butyl alcohol (TBA) biodegradation kinetics in hyporheic zone soils

    PubMed Central

    Greenwood, Mark H; Sims, Ronald C; McLean, Joan E; Doucette, William J

    2007-01-01

    Background Remediation of tert-butyl alcohol (TBA) in subsurface waters should be taken into consideration at reformulated gasoline contaminated sites since it is a biodegradation intermediate of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-butyl formate (TBF). The effect of temperature on TBA biodegradation has not been not been published in the literature. Methods Biodegradation of [U 14C] TBA was determined using hyporheic zone soil microcosms. Results First order mineralization rate constants of TBA at 5°C, 15°C and 25°C were 7.84 ± 0.14 × 10-3, 9.07 ± 0.09 × 10-3, and 15.3 ± 0.3 × 10-3 days-1, respectively (or 2.86 ± 0.05, 3.31 ± 0.03, 5.60 ± 0.14 years-1, respectively). Temperature had a statistically significant effect on the mineralization rates and was modelled using the Arrhenius equation with frequency factor (A) and activation energy (Ea) of 154 day-1 and 23,006 mol/J, respectively. Conclusion Results of this study are the first to determine mineralization rates of TBA for different temperatures. The kinetic rates determined in this study can be used in groundwater fate and transport modelling of TBA at the Ronan, MT site and provide an estimate for TBA removal at other similar shallow aquifer sites and hyporheic zones as a function of seasonal change in temperature. PMID:17877835

  7. Groundwater and solute transport modeling at Hyporheic zone of upper part Citarum River

    NASA Astrophysics Data System (ADS)

    Iskandar, Irwan; Farazi, Hendy; Fadhilah, Rahmat; Purnandi, Cipto; Notosiswoyo, Sudarto

    2017-06-01

    Groundwater and surface water interaction is an interesting topic to be studied related to the water resources and environmental studies. The study of interaction between groundwater and river water at the Upper Part Citarum River aims to know the contribution of groundwater to the river or reversely and also solute transport of dissolved ions between them. Analysis of drill logs, vertical electrical sounding at the selected sections, measurement of dissolved ions, and groundwater modeling were applied to determine the flow and solute transport phenomena at the hyporheic zone. It showed the hyporheic zone dominated by silt and clay with hydraulic conductivity range from 10-4∼10-8 m/s. The groundwater flowing into the river with very low gradient and it shows that the Citarum River is a gaining stream. The groundwater modeling shows direct seepage of groundwater into the Citarum River is only 186 l/s, very small compared to the total discharge of the river. Total dissolved ions of the groundwater ranged from 200 to 480 ppm while the river water range from 200 to 2,000 ppm. Based on solute transport modeling it indicates dissolved ions dispersion of the Citarum River into groundwater may occur in some areas such as Bojongsoang-Dayeuh Kolot and Nanjung. This situation would increase the dissolved ions in groundwater in the region due to the contribution of the Citarum River. The results of the research can be a reference for further studies related to the mechanism of transport of the pollutants in the groundwater around the Citarum River.

  8. Modelling of transient river - aquifer exchange using pressure head and heat measurements: the hyporheic zone's dimension

    NASA Astrophysics Data System (ADS)

    Nuetzmann, Gunnar; Christian, Levers; Jörg, Lewandowski

    2010-05-01

    Water exchange processes in the floodplain of a lowland groundwater-surface water system are studied on the basis of a study site near Freienbrink, NE Germany. The surface water boundaries of this site are formed by an oxbow and the current bed of the river Spree, section Müggelspree. Surface and ground water levels and water temperatures were collected in 12 piezometers and 2 recording stage gauges of a 300 m long transect throughout a one-year-period. Due to water level fluctuations alternation of infiltration and exfiltration occurred. However, most of the time groundwater flux is directed into the river Spree and, river water infiltration events into the aquifer are usually short and of minor importance. Due to clogging of the oxbow bed with a mud layer of different thickness the hydraulic contact between the oxbow and the adjacent aquifer is heterogeneously distributed and partially marginal. These features are modelled quantitatively using SUTRA in order to simulate coupled ground water flow and heat transport. A two-dimensional vertical modelling approach along the piezometer transect is developed to study exchange processes close to the surface water bodies more in detail in order to quantify the hyporheic fluxes of both river sections and to identify the directions and quantities of mass and heat fluxes. With the results the following questions will be answered: (1) It is possible to identify and to quantify the hydraulic processes (in- and exfiltration) between both river sections and the aquifer? (2) How fast does the exchange between the surface water and the aquifer occur? (3) Is there a hyporheic zone between the river sections and the aquifer, where groundwater and surface water are mixed, and how much water and heat will be transferred through this zones?

  9. Trace Element Mobility in Water and Sediments in a Hyporheic Zone Adjacent to an Abandoned Uranium Mine

    NASA Astrophysics Data System (ADS)

    Roldan, C.; Blake, J.; Cerrato, J.; Ali, A.; Cabaniss, S.

    2015-12-01

    The legacy of abandoned uranium mines lead to community concerns about environmental and health effects. This study focuses on a cross section of the Rio Paguate, adjacent to the Jackpile Mine on the Laguna Reservation, west-central New Mexico. Often, the geochemical interactions that occur in the hyporheic zone adjacent to these abandoned mines play an important role in trace element mobility. In order to understand the mobility of uranium (U), arsenic (As), and vanadium (V) in the Rio Paguate; surface water, hyporheic zone water, and core sediment samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). All water samples were filtered through 0.45μm and 0.22μm filters and analyzed. The results show that there is no major difference in concentrations of U (378-496μg/L), As (0.872-6.78μg/L), and V (2.94-5.01μg/L) between the filter sizes or with depth (8cm and 15cm) in the hyporheic zone. The unfiltered hyporheic zone water samples were analyzed after acid digestion to assess the particulate fraction. These results show a decrease in U concentration (153-202μg/L) and an increase in As (33.2-219μg/L) and V (169-1130μg/L) concentrations compared to the filtered waters. Surface water concentrations of U(171-184μg/L) are lower than the filtered hyporheic zone waters while As(1.32-8.68μg/L) and V(1.75-2.38μg/L) are significantly lower than the hyporheic zone waters and particulates combined. Concentrations of As in the sediment core samples are higher in the first 15cm below the water-sediment interface (14.3-3.82μg/L) and decrease (0.382μg/L) with depth. Uranium concentrations are consistent (0.047-0.050μg/L) at all depths. The over all data suggest that U is mobile in the dissolved phase and both As and V are mobile in the particular phase as they travel through the system.

  10. The Effects of Dissolved Organic Carbon Quantity and Quality on Hyporheic Zone Microbial Respiration

    NASA Astrophysics Data System (ADS)

    Sanfilippo, A. R.; Feris, K. P.; Wondzell, S. M.; Serchan, S. P.; Tonina, D.; Haggerty, R.; Reeder, W. J.; Pennington, R.; Dunn, G.; Bring-Horvath, E.

    2016-12-01

    Global carbon respiration totals approximately 100 Pg per year, of which approximately 1% is contributed by streams. The majority of that contribution occurs in the hyporheic zone (HZ) of the stream. Heterotrophic HZ microbial communities contribute 40-90% of total stream respiration via metabolism of dissolved organic carbon compounds (DOC). However, the processes controlling HZ metabolism are poorly constrained and effects of the type (labile vs recalcitrant) and quantity of DOC on microbial respiration have not been extensively studied. Our study site, Watershed 1, a 2nd order headwater stream in the HJ Andrews Experimental Forest, provides historic stream data detailing seasonal variability in DOC concentrations. We are performing two experiments to assess effects of DOC on HZ respiration. An on-going observational experiment utilizing a network of 41 hyporheic wells measures seasonal variations in in vitro rates of HZ respiration and DOC via short term incubations of sediment and pore water. Pore water is analyzed for in situ DOC factors, temperature, and pH, and sediments are analyzed for microbial abundance via real-time PCR (qPCR). These in situ data are correlated to the in vitro consumption of oxygen over time and show a marked increase in respiration in response to a seasonal influx of DOC. Separately, an on-going manipulative experiment consisting of six replicate 2 meter hyporheic mesocosms is being utilized to measure in situ rates of HZ microbial respiration via the rate of consumption of dissolved oxygen. We are utilizing these mesocosms to examine the effects of labile (acetate) and recalcitrant (fulvic acid and similar) DOC amendments on microbial respiration. Initial observations suggest a connection between higher rates of microbial respiration, larger quantities of DOC, and more labile types of DOC, with average DO consumption rates experiencing a nearly nine-fold increase during periods of high DOC (0.18 - 1.44 µg O2 g sediment-1 hour-1). On

  11. Change in hyporheic zone residence time under different surface flow states

    NASA Astrophysics Data System (ADS)

    Liu, Suning; Chui, Ting Fong May

    2017-04-01

    Hyporheic zone (HZ), which is the ecotone immediately below or adjacent to a stream, plays an important role in a stream ecological system. One of the most common metrics in evaluating the functioning of an HZ is residence time (RT) which is the duration a water molecule or a solute remains within the HZ. Many factors, such as meandering of a stream, heterogeneity of streambed, can influence the RT of an HZ. Stream discharge is another governing but less discussed factor. Different discharge values produce different flow states (i.e.., subcritical, critical and supercritical) and alluvial stream bed forms. This study examined the changes of RT in discharges of different states and their corresponding induced bed forms. It employed a toolbox developed by Stonedahl et al. (2015) within Netlogo to simulate the RT of an HZ, considering three discharge values in each of the supercritical, critical and subcritical states. It approximated the bed forms as sinusoidal waves with amplitudes and periods selected for each flow state. The simulated results suggest that the RT is minimum when the flow is critical, and it is longer for both subcritical and supercritical flows. For subcritical flow, the RT, as well as the fraction remained within the streambed during particle tracing, increases with the increase in discharge value. However, there is no such variation among the different discharge values of supercritical flow. Therefore, for supercritical flow, one combination of discharge value and bed form might be sufficient and representative. However, for subcritical flow, the variations of discharge values and their induced bed forms should be considered. Reference: Stonedahl, S.H., Roche, K.R., Stonedahl, F., & Packman, A.I. (2015). Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation. J. Vis. Exp. (105), e53285. doi: 10.3791/53285

  12. 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.

  13. Time-lapse ERT and DTS for seasonal and short-term monitoring of an alpine river hyporheic zone

    NASA Astrophysics Data System (ADS)

    Boaga, Jacopo; Laura, Busato; Mariateresa, Perri; Giorgio, Cassiani

    2016-04-01

    The hyporheic zone (HZ) is the area located beneath and adjacent to rivers and streams, where the interactions between surface water and groundwater take place. This complex physical domain allows the transport of several substances from a stream to the unconfined aquifer below, and vice versa, thus playing a fundamental role in the river ecosystem. The importance of the hyporheic zone makes its characterization a goal shared by several disciplines, which range from applied geophysics to biogeochemistry, from hydraulics to ecology. The frontier field of HZ characterization stays in applied non-invasive methodologies as Electrical Resistivity Tomography - ERT - and Distributed Temperature Sensing - DTS. ERT is commonly applied in cross-well configuration or with a superficial electrodes deployment while DTS is used in hydro-geophysics in the last decade, revealing a wide applicability to the typical issues of this field of study. DTS for hydro-geophysics studies is based on Raman scattering and employs heat as tracer and uses a fiber-optic cable to acquire temperature values. We applied both techniques for an alpine river case studies located in Val di Sole, TN, Italy. The collected measurements allow high-resolution characterization of the hyporheic zone, overcoming the critical problem of invasive measurements under riverbeds. In this work, we present the preliminary results regarding the characterization of the hyporheic zone of the alpine river obtained combining ERT and DTS time-lapse measurements. The data collection benefits from an innovative instrumentation deployment, which consists of both an ERT multicore cable and a DTS fiber-optic located in two separated boreholes drilled 5m under the watercourse and perpendicular to it. In particular we present the first year monitoring results and a short time-lapse monitoring experiment conducted during summer 2015. The site and the results here described are part of the EU FP7 CLIMB (Climate Induced Changes on the

  14. A tale of two interfaces: Dynamic nitrate removal in the hyporheic zone of a tidal fresh river

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Knights, D. H.; Barnes, R. T.; Wallace, C.; Bray, S. N.; Musial, C.

    2015-12-01

    At the interface of rivers and oceans, tidal freshwater zones (TFZs) stretch for tens to hundreds of kilometers but are rarely monitored for nitrogen export due to their complex hydrodynamics. Field observations from the TFZ of White Clay Creek (Delaware, USA) show that river discharge and nitrate export rates decrease during rising tide, while hyporheic storage increases. During falling tide, river discharge and nitrate export rates increase, while stored hyporheic water is released to the river. We estimate that 11% of river water exchanges through the hyporheic zone of this TFZ due to tidal pumping alone. We developed a one-dimensional, coupled fluid flow and solute transport model to quantify the influence of tidal pumping on nitrate removal in the riverbed. Tidal pumping promotes a deep, oscillating zone of aerobic respiration that limits denitrification near the sediment-water interface. As tide rises, groundwater residence times in shallow riverbed sediments increase, which causes a doubling of denitrification rates relative to falling tide. Given a uniform substrate along TFZs, removal rates of groundwater-borne nitrate should decrease as tidal amplitude increases downstream. Denitrification hot spots should occur in less permeable, organic-rich sediment under low tidal ranges. Because TFZs connect lowland nitrogen sources to the ocean, it is imperative that we expand monitoring efforts and elucidate their role in nitrogen export to the coast.

  15. Experimental analysis and modelling of the oxygen balance in the hyporheic zone of the Kharaa River (Mongolia)

    NASA Astrophysics Data System (ADS)

    Hartwig, M.; Borchardt, D.

    2012-04-01

    The hyporheic zone has important functions for the aquatic ecosystem like beeing a habitat for a variety of organisms and a reactor for a multitude of transformation processes. But these functions are dependent on the availability of oxygen. Under oxygen depletion for example, the habitat for macroinvertebrates and fish gets lost, and denitrification or the dissolution of phosphorous occurs. Then again, the input, retention time and depletion of oxygen is for most of the part dependent on the morphology and the sediment properties. Therefor, the aim of the study is the process analysis of the oxygen balance within the compartments surface water column and hyporheic zone along a river gradient and under consideration of sediment input. The study area of the Kharaa River (Mongolia) is suitable for that reason as it is close to natural conditions and an identifiable point source of suspended sediment enables a causal analysis of the clogging problem. For the numerical analysis a two-compartment model on the riffle scale was conceptualized. According to that an intensive monitoring program was conducted in spring and late summer of 2010 and 2011 including methods for the characterization of the hydraulics, the exchange as well as biogeochemical properties. The model concept was implemented in AQUASIM and calibrated with the data. The data show a decreased interaction of surface and interstitial water along the river gradient, in particular the diversity of oxygenation and therefor potential transformation processes within the hyporheic zone decreased. And the functional loss for habitat and production could be proved to be impaired by suspended or infiltrated sediments. The results of the numerical analysis demonstrates, at which state the clogging process can become critical for the hyporheic functioning. This study provides important information in order to identify critical conditions for the aquatic ecology as well as for the self regulation of the river under

  16. Mixing effects on nitrogen and oxygen concentrations and the relationship to mean residence time in a hyporheic zone of a riffle-pool sequence

    USGS Publications Warehouse

    Naranjo, Ramon C.; Niswonger, Richard G.; Clinton Davis,

    2015-01-01

    Flow paths and residence times in the hyporheic zone are known to influence biogeochemical processes such as nitrification and denitrification. The exchange across the sediment-water interface may involve mixing of surface water and groundwater through complex hyporheic flow paths that contribute to highly variable biogeochemically active zones. Despite the recognition of these patterns in the literature, conceptualization and analysis of flow paths and nitrogen transformations beneath riffle-pool sequences often neglect to consider bed form driven exchange along the entire reach. In this study, the spatial and temporal distribution of dissolved oxygen (DO), nitrate (NO3-) and ammonium (NH4+) were monitored in the hyporheic zone beneath a riffle-pool sequence on a losing section of the Truckee River, NV. Spatially-varying hyporheic exchange and the occurrence of multi-scale hyporheic mixing cells are shown to influence concentrations of DO and NO3- and the mean residence time (MRT) of riffle and pool areas. Distinct patterns observed in piezometers are shown to be influenced by the first large flow event following a steady 8 month period of low flow conditions. Increases in surface water discharge resulted in reversed hydraulic gradients and production of nitrate through nitrification at small vertical spatial scales (0.10 to 0.25 m) beneath the sediment-water interface. In areas with high downward flow rates and low MRT, denitrification may be limited. The use of a longitudinal two-dimensional flow model helped identify important mechanisms such as multi-scale hyporheic mixing cells and spatially varying MRT, an important driver for nitrogen transformation in the riverbed. Our observations of DO and NO3- concentrations and model simulations highlight the role of multi-scale hyporheic mixing cells on MRT and nitrogen transformations in the hyporheic zone of riffle-pool sequences. This article is protected by copyright. All rights reserved.

  17. A Bayesian inversion of hydrological and thermal parameters in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Cucchi, K.; Flipo, N.; Rivière, A.; Rubin, Y.

    2015-12-01

    Reliable estimates of hydrological properties at the stream-aquifer interface are necessary for quantifying surface-subsurface exchanges but are challenging to get due to spatial variability and field data scarcity. Our study introduces a novel approach for inferring uncertainty-quantified hydrological and thermal parameters from a combination of pressure and temperature measurements in the hyporheic zone (HZ). We use a stochastic approach to infer thermal and hydrological parameters in a HZ vertical profile. The column is forced by pressure and temperature time series at the boundaries and conditioned on temperature at multiple depths. The inversion process is based on a Bayesian algorithm called Method of Anchored Distribution (MAD) and on the associated open-source program MAD++, with extensions in the post-processing toolbox. This approach has several benefits. First, the hierarchical framework built-in in MAD allows the specification of a non-parametric and assumption-free likelihood function. Moreover, the Bayesian approach yields data-driven and naturally uncertainty-quantified parameter estimates. We present two outcomes of the inversion approach. (1) Repeating the analysis at multiple locations yields spatially-distributed snapshots of uncertainty-quantified HZ parameters. (2) The unconditional posterior distribution of hydrological parameters is integrated in a Monte-Carlo error estimation framework to provide statistical distributions of surface-subsurface exchanges time series. We present the methodology and demonstrate its application using field measurements from the Avenelles basin, France.

  18. Freeze shoe sampler for the collection of hyporheic zone sediments and porewater.

    PubMed

    Bianchin, M; Smith, L; Beckie, R

    2015-01-01

    The Starr and Ingleton (1992) drive point piston sampler (DPPS) design was modified by fitting it with a Murphy and Herkelrath (1996) type sample-freezing drive shoe (SFDS), which uses liquid carbon dioxide as a cryogen. Liquid carbon dioxide was used to freeze sediments in the lower 0.1 m of the core and the drive-point piston sealed the core at the top preserving the reductive-oxidation (redox) sensitive sediments from the atmosphere and maintaining natural stratigraphy. The use of nitrogen gas to provide positive pressure on the gas system blocked the ingress of water which froze on contact with the cryogen thus blocking the gas lines with ice. With this adaptation to the gas system cores could be collected at greater depths beneath the static water level. This tool was used to collect intact saturated sediment cores from the hyporheic zone of the tidally influenced Fraser River in Vancouver, British Columbia, Canada where steep geochemical and microbial gradients develop within the interface between discharging anaerobic groundwater and recharging aerobic river water. In total, 25 cores driven through a 1.5 m sampling interval were collected from the river bed with a mean core recovery of 75%. The ability to deploy this method from a fishing vessel makes the tool more cost effective than traditional marine-based drilling operations which often use barges, tug boats, and drilling rigs.

  19. Chemoautotrophic production and respiration in the hyporheic zone of a sonoran desert stream

    SciTech Connect

    Jones, J.B. Jr.; Holmes, R.M.; Fisher, S.G.; Grimm, N.B.

    1994-12-31

    Chemoautotrophic production and respiration (aerobic and anaerobic) were examined along flowpaths in three subsystems in Sycamore Creek, Arizona. Chemoautotrophic production was highest where surface waters enter parafluvial sediments (64 to 76 mgC{center_dot}m{sup {minus}2}{center_dot}d{sup {minus}1}) and lowest in anoxic bank sediments (14 to 16 mgC{center_dot}m{sup {minus}2}{center_dot}d{sup {minus}1}). Aerobic respiration was considerable greater than chemoautotrophy in oxygenated hyporheic and parafluvial zones (2,400 to 4,900 mgC{center_dot}m{sup {minus}2}{center_dot}d{sup {minus}1}). In anoxic bank sediments, respiration was also much greater than chemoautotrophy, but was entirely anaerobic (i.e., methane production; 3,500 mgC{center_dot}m{sup {minus}2}{center_dot}d{sup {minus}1}). Weighting subsystems by areal extent, the largest proportion of aerobic respiration and chemoautotrophic production occurred in parafluvial sediments (64 to 76%), whereas anoxic bank sediments were most important for anaerobic respiration (94% of total anaerobic respiration). Overall, chemoautotrophic production was only 1.0 to 1.3% of respiration and methane production was only 5% of total sediment respiration.

  20. Unraveling the Drivers of Spatial and Temporal Variability in Biogeochemical Cycling at Aquifer-River Interfaces - The LEVERHULME Hyporheic Zone Research Network

    NASA Astrophysics Data System (ADS)

    Krause, S.; Ward, A. S.; Zarnetske, J. P.; Martí Roca, E.; Larned, S.; Milner, A.; Datry, T.; Fleckenstein, J. H.; Schmidt, C.; Blaen, P.; Kurz, M. J.; Klaar, M. J.; Drummond, J. D.; Knapp, J.; Folegot, S.; Hannah, D. M.; Romeijn, P.; Blume, T.; Lewandowski, J.; Maruedo, A.; Ledger, M.; Lee-Cullin, J. A.; O'Callaghan, M.; Keller, T.; Vieweg, M.

    2014-12-01

    While there has been substantial improvement of understanding hyporheic exchange flow and residence time controls on biogeochemical turnover rates, there is little knowledge of the actual drivers of the spatial and temporal variability of interlinked biogeochemical cycles. Previous research has mainly focused on bedform controlled hyporheic exchange and the transformation of surface solutes along a hyporheic flow path but failed to explain observations of spatially and temporally variable nutrient turnover in streambeds with higher structural heterogeneity and autochthonous carbon and nitrogen sources. The "Leverhulme Hyporheic Zone Research Network" has developed an interdisciplinary strategy for investigating the physical controls on hyporheic exchange fluxes and residence time distributions, heat and reactive solute transport along biogeographical and catchment gradients. This strategy combines smart tracer applications with distributed sensor networks in multi-scale nested monitoring schemes and numerical model studies to investigate the interactions between physico-chemical process dynamics and hyporheic microbial, invertebrate and macrophyte ecology. Investigations integrating the process knowledge from mesocosms to artificial channels and stream reaches highlight the impact of small-scale streambed structure on spatial patterns of hyporheic exchange flow, residence time distribution and the development of biogeochemical hotspots. Manipulation studies inhibiting flow through dominant hyporheic exchange flow paths allowed to quantify the functional significance, sensitivity and resilience of biogeochemical, microbial and ecological functioning of identified hyporheic hotspots to environmental change. Further discharge and stage manipulations proved to not only control in-channel macrophyte growth but also temperature patterns and residence time distributions as well as microbial metabolic activity and biogeochemical processing rates, highlighting the potential

  1. Unraveling the Drivers of Spatial and Temporal Variability in Biogeochemical Cycling at Aquifer-River Interfaces - The LEVERHULME Hyporheic Zone Research Network

    NASA Astrophysics Data System (ADS)

    Krause, Stefan

    2015-04-01

    While there has been substantial improvement of understanding hyporheic exchange flow and residence time controls on biogeochemical turnover rates, there is little knowledge of the actual drivers of the spatial and temporal variability of interlinked biogeochemical cycles. Previous research has mainly focused on bedform controlled hyporheic exchange and the transformation of surface solutes along a hyporheic flow path but failed to explain observations of spatially and temporally variable nutrient turnover in streambeds with higher structural heterogeneity and autochthonous carbon and nitrogen sources. The "Leverhulme Hyporheic Zone Research Network" has developed an interdisciplinary strategy for investigating the physical controls on hyporheic exchange fluxes and residence time distributions, heat and reactive solute transport along biogeographical and catchment gradients. This strategy combines smart tracer applications with distributed sensor networks in multi-scale nested monitoring schemes and numerical model studies to investigate the interactions between physico-chemical process dynamics and hyporheic microbial, invertebrate and macrophyte ecology. Investigations integrating the process knowledge from mesocosms to artificial channels and stream reaches highlight the impact of small-scale streambed structure on spatial patterns of hyporheic exchange flow, residence time distribution and the development of biogeochemical hotspots. Manipulation studies inhibiting flow through dominant hyporheic exchange flow paths allowed to quantify the functional significance, sensitivity and resilience of biogeochemical, microbial and ecological functioning of identified hyporheic hotspots to environmental change. Further discharge and stage manipulations proved to not only control in-channel macrophyte growth but also temperature patterns and residence time distributions as well as microbial metabolic activity and biogeochemical processing rates, highlighting the potential

  2. Measuring vertical oxygen profiles in the hyporheic zone using planar optodes

    NASA Astrophysics Data System (ADS)

    Vieweg, M.; Fleckenstein, J. H.; Schmidt, C.

    2012-04-01

    On of the key parameters, controlling biogeochemical reactions in the hyporheic zone (HZ) is the distribution of oxygen. A reliable measurement of the vertical oxygen distribution is an important tool to understand the dynamic fluctuations of the aerobic zone within the HZ. With repeated measurements of continuous profiles, mixing of surface water and groundwater as well as the consumption of oxygen can be evaluated. We present a novel approach for the in situ measurements of vertical oxygen distribution in the riverbed using a planar optode. The luminescence based optode measurement enables a non invasive measurement without consumption of oxygen, no creation of preferential flow paths and only minimal disturbance of the flow field. Possible atmospheric contamination by pumping pore water into a vessel can be avoided and the readings are independent of flow velocity. A self manufactured planar optode is wrapped around an acrylic tube and installed in the riverbed. The measurement is performed by vertically moving a profiler-piston inside the acrylic tube. The piston holds a robust polymer optical fibre which emits a modulated light signal through the acrylic glass to the optode-foil and transmits the induced luminescence signal back to a commercially available trace oxygen meter. Temperature compensation is accomplished using a depth-oriented temperature probe nearby and processing the raw data within a Matlab script. Robust and unbiased oxygen profiles are obtained by averaging multiple consecutive measurements. To ensure a constant velocity of the profiler for replicating the exact measuring depths, an electric motor device is used. First results at our test site show a variable oxygen profile down to 40 cm depth which is strongly influenced by stream level and upwelling groundwater conditions. The measured oxygen profiles will serve as input parameter for a 3D solute transport and chemical reaction subsurface model of the HZ.

  3. Changes in distribution of fine sediments in the hyporheic zone during high flow events

    NASA Astrophysics Data System (ADS)

    Kasahara, T.; Yasuda, Y.; Otsuki, K.

    2013-12-01

    Streambed sediments are dynamic, influencing stream-groundwater exchange. Reduction of the exchange flow due to streambed clogging by fine sediments has been reported in impacted agricultural and urban streams. In natural streams, intrusion of fine sediments and subsequent clogging may occur, but its effects are expected to be temporary due to the periodical washout of fine sediments. Understanding the dynamics of fine sediments in shallow streambed in natural streams is important in studying stream-groundwater exchange and in designing of management practices of impacted streams. In this study, we focused on shallow streambed, less than 25cm depth, where hyporheic exchange occurs. The concentrations of fine sediments in interstitial water were measured, using PVC pipes, to study the change in fine sediments distribution in the streambed during high flow events. We also measured the sediment accumulation on the streambed, using mesh, to study the linkage between the locations of surface accumulation and fine sediment intrusion. The study site was located in a 3rd order stream with gravel-cobble bed and base flow of about 80 L/s in northern Kyushu Island of Japan. The concentration of fine sediments in the interstitial water varied considerably among sampling locations, ranging from 38mg/L to over 200mg/L with an average of 120mg/L. The concentrations increased after high flow event, with an average of 3g/L in some event, and they were higher in the locations with negative vertical head gradient, indicating that the downwelling flow carrying fine sediments into the interstitial zone. Streambed sediment accumulation showed relation with fine sediment concentration, and also with water depth and velocity, suggesting that the surface channel condition may indicate the locations of fine sediments intrusion in the interstitial zone. The results of this study showed that fine sediment distribution in the shallow streambed changes considerably during high flow events, and

  4. The importance and challenge of hyporheic mixing

    NASA Astrophysics Data System (ADS)

    Hester, Erich T.; Cardenas, M. Bayani; Haggerty, Roy; Apte, Sourabh V.

    2017-05-01

    The hyporheic zone is the interface beneath and adjacent to streams and rivers where surface water and groundwater interact. The hyporheic zone presents unique conditions for reaction of solutes from both surface water and groundwater, including reactions which depend upon mixing of source waters. Some models assume that hyporheic zones are well-mixed and conceptualize the hyporheic zone as a surface water-groundwater mixing zone. But what are the controls on and effects of hyporheic mixing? What specific mechanisms cause the relatively large (>˜1 m) mixing zones suggested by subsurface solute measurements? In this commentary, we explore the various processes that might enhance mixing in the hyporheic zone relative to deeper groundwater, and pose the question whether the substantial mixing suggested by field studies may be due to the combination of fluctuating boundary conditions and multiscale physical and chemical spatial heterogeneity. We encourage investigation of hyporheic mixing using numerical modeling and laboratory experiments to ultimately inform field investigations.

  5. Geomorphic controls on hyporheic exchange flow in mountain streams.

    Treesearch

    T. Kasahara; S.M. Wondzell

    2003-01-01

    Hyporheic exchange flows were simulated using MODFLOW and MODPATH to estimate relative effects of channel morphologic features on the extent of the hyporheic zone, on hyporheic exchange flow, and on the residence time of stream water in the hyporheic zone. Four stream reaches were compared in order to examine the influence of stream size and channel constraint. Within...

  6. Seasonal variation of water level, water and soil temperature, chemistry, and stable isotopes in hyporheic zone of Korea

    NASA Astrophysics Data System (ADS)

    Jeon, W. H.; Lee, J. Y.

    2015-12-01

    The purpose of study was to evaluate interaction between groundwater and stream water in hyporheic zone using water level, water temperature, soil temperature, chemistry, and stable isotopes. We installed seven piezometers (IYHW1 to 7) in the streambed that across stream in every 10 m and in depth of 0.85 to 1.54 m, a device that measure stage level nearby IYHW1, and devices that measure soil temperature in every 10 cm down to 50 cm nearby each piezometer was installed. We monitored water level and water temperature every hour from automatic transducers at the piezometers and the stage level, and soil temperatures were monitored every two hours. We took samples from the hyporheic water, stream water, and nearby groundwater to analysis chemical and isotopic compositions. The water level difference between stream water and hyporheic waters indicated that groundwater was downwelling in wet season and upwelling in dry season. The groundwater temperature remained steady in different seasons, but the stream water represented a frequent fluctuation with large amplitude. The hyporheic waters and soil temperature represented intermediate variation characteristics. The chemical compositions were not able to indicate in interaction of groundwater and stream water because no distinctive difference in seasonal variation in waters. The quantity of isotopic compositions of oxygen and hydrogen determined from using mixing ratio indicated that downwelling in wet season and upwelling in dry season. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2011-0007232).

  7. Experimental and modelling approaches for characterizing stream water-groundwater mixing and dynamic in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Houzé, Clémence; Durand, Véronique; Pessel, Marc; Mugler, Claude; Mouche, Emmanuel; Varnède, Lucie

    2017-04-01

    The hyporheic zone, which is a near-channel zone of surface water-groundwater mixing, has a major importance in the functioning of ecosystems and reflects the whole ecological state of a river. As a consequence, a good understanding of the processes involved in the hyporheic zone is essential for river restoration. In the present work, we used both experimental and modelling approaches for characterizing stream water - groundwater mixing and dynamic in the Essonne River (France). The experimental approach was based on geophysical and geochemical tools that give complementary results; water analyses are punctual whereas geophysical surveys give a continuous 2D model of the distribution of some parameters in the subsurface. The river was instrumented with several electrodes lines for electrical resistivity tomography (ERT), and multi-sampling systems to collect pore water from several depths within the streambed sediments. Precise topography of every electrode, piezometer and sampling system was done in order to understand the possible effect of streambed topography on observed measurements. An artificial flood was reproduced during a dam controlled experiment. The dam level downstream the studied area was lowered and raised in order to simulate a flood without any additional contribution from runoff. Another experiment was performed to follow the river water into the streambed sediments. Salt was added into the stream and followed with a high resolution monitoring. Results from the different experiments showed that is it possible to follow the hyporheic zone dynamic thanks to different varieties of tools. The geophysical surveys indicate a clear change in resistivity of the streambed sediments when the water chemistry of the stream changes, along with the dam experiment. The end of the monitoring highlights a quite rapid return to the stable state despite some hysteresis observed in electric measurements. In the modelling approach, we used a 3D distributed model

  8. Dynamic Change of Water Quality in Hyporheic Zone at Water Curtain Cultivation Area, Cheongju, Korea

    NASA Astrophysics Data System (ADS)

    Moon, S. H.; Kim, Y.

    2015-12-01

    There has been recently growing numbers of facilities for water curtain cultivation of strawberry and lettuce in Korea. These areas are nearly all located in the fluvial deposits near streams which can replenish water resources into exhausted groundwater aquifers during peak season. The purpose of this study is on groundwater chemistry and the change in physical and chemical properties due to stream-groundwater exchange or mixing in the representative agricultural area among the Jurassic granitic terrain of Korea. In the study area, groundwater level continuously decreased from November through March due to intensive use of groundwater, which forced stream water into aquifer. After March, groundwater level was gradually recovered to the original state. To evaluate the extent and its variations of stream water mixing into aquifer, field parameters including T, pH, EC and DO values, concentrations of major ions and oxygen and hydrogen stable isotopic ratios were used. Field measurements and water sample collections were performed several times from 2012 to 2015 mainly during peak time of groundwater use. To compare the temporal variations and areal differences, 21 wells from four cross sections perpendicular to stream line were used. While water temperature, EC values and concentrations of Ca, Mg, Si, HCO3 showed roughly gradual increase from stream line to 150 m distance, pH and DO values showed reverse phenomenon. This can be used to evaluate the extent and limit of stream water introduction into aquifer. However, individual wells showed yearly variations in those parameters and this dynamic and unstable feature indicates that mixing intensity of stream water over groundwater in this hyporheic zone varied year by year according to amounts of groundwater use and decrease of groundwater level.

  9. Combining direct residence time measurements and biogeochemistry to calculate in-situ reaction rates in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Pittroff, Marco; Gilfedder, Benjamin

    2015-04-01

    The hyporheic zone is an active interface between groundwater, riparian and surface water systems. Exchange and reaction of water, nutrients, and organic matter occur due to variations in surface and groundwater flow regimes, bed topography and active biogeochemistry fuelled by bioavailable carbon. There has been an increasing focus on coupling the residence time of surface water in the hyporheic zone with biogeochemical reactions. However, there are very few tracers that can be used to measure residence times in-situ, especially in complex groundwater-surface water settings. In this work we have used the natural radioisotope Radon (222Rn) as an in-situ tracer for river water residence time in a riffle-pool sequence (Rote Main River), and combined this information with biogeochemical parameters (DOC and C quality, O3, NO3, CO2). We can clearly observe a dependence of reaction progress on the water residence times, with oxygen and nitrate reduction following inverse logarithmic trends as a function of time. By comparing with initial concentrations (the river end member) with riverbed levels we have estimated first-order in-situ reduction rates for nitrate and oxygen. Nitrate reduction rates are at the higher end of published values, which is likely due to the continual supply of bioavailable carbon from the river system. This work helps to better understand the function and efficiency of the hyporheic zone as a natural filter for redox sensitive species such as nitrate at the groundwater - steam interface. It also provides a useful method for estimating residence times in complex, higher order river systems.

  10. Hyporheic Zones in Coastal Streams: Filters for Removal of Agricultural Nitrate

    NASA Astrophysics Data System (ADS)

    Mills, A. L.; Hornberger, G. M.; Herman, J. S.; Chauhan, M. J.; Galavotti, H. S.

    2002-12-01

    The Eastern Shore of Virginia comprises about 35-40% active cropland which receives extensive nitrogen fertilization to support corn, wheat, soybeans, tomatoes and cotton. The unconfined Columbia aquifer contains NO3- at concentrations of 8 to 25 mg N L-1. The low relief streams that drain the peninsula into the seaside lagoons, and are fed from groundwater under both base flow and flood conditions, contain a wide range of NO3- concentrations, 0.5 to 10 mg N L-1, but all of the streams have a much lower NO3- concentration than the aquifers charging them. In Cobb Mill Creek, the change in NO3- concentration is from 10-12 mg L-1 in the groundwater to 1-2 mg L-1 in the stream under base flow conditions. Piezometers inserted into this stream indicate the NO3- is removed from the water within a zone of 1 m below the stream sediment surface. Removal of these amounts of NO3- from the water over such a short distance suggests the mechanism for removal is bacterial denitrification. The overall impact of the removal was determined by modeling the NO3- loading into the seaside lagoons under base flow conditions from all the streams draining into the lagoons. Discharge and NO3- measurements were made for a number of seaside streams. A watershed area - stream discharge relationship was established with those data that allowed estimation of the discharge from the remaining streams. NO3- concentrations in the remaining streams was estimated by the relationship between the % cropland in the watershed and the NO3- concentration in the stream. Annual NO3- loading into the seaside lagoons under base flow conditions is estimated to be about 2 x 105 kg NO3-- N per year. Estimated loading in the absence of agriculture (assuming all cropland was still unfertilized forest) was about 1 x 103 kg NO3-- N per year. Nevertheless, denitrification in the hyporheic zone apparently accounts for removal of about 8 x 105 kg NO3-- N per year, drastically reducing the enrichment of the lagoons by

  11. Development of a Passive Sensor for Measuring Water and Solute Mass Flux in the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Annable, Michael D.; Layton, Leif; Hatfield, Kirk; Newman, Mark C.; Cho, Jaehyun; Klammler, Harald

    2014-05-01

    Measuring water, pollutant and nutrient exchange at the groundwater-surface water interface is challenging due to the dynamic nature of the hyporheic zone. Quantifying the exchange is critical to understanding mass balance across this interface. Technologies currently exist to identify groundwater discharge zones and infer estimates of contaminant mass flux based on total contaminant concentration in bulk sediment, though it is generally accepted that freely dissolved concentration in pore water is a better measure of potential exposure. Laboratory and preliminary field testing has been completed to demonstrate a new tool with potential to provide more accurate characterization of water, pollutant and nutrient flux at the groundwater-surface water interface through direct in-situ measurement. The sediment bed passive flux meter (SBPFM) was designed for passively and directly providing in-situ measurements of volumetric water flux and solute mass flux vertically through the upper surface sediment layer and into the overlying water column. The SBPFM consists of an internal permeable sorbent which is impregnated with one or more water soluble tracers (typically alcohols) and is contained in a dedicated drive-point with upper and lower screened openings for fluid intake and exhaust. This configuration generates water flow through the device proportional to the vertical gradient between the sediment bed and the water column. Once the SBPFM has been deployed, the tracers are displaced from the sorbent at rates proportional to the average vertical specific discharge. The mass loss of tracers during deployment can be used to calculate the cumulative water flux. Similarly, the cumulative mass of sorbed pollutants or nutrients provide a direct measurement of the vertical mass flux during deployment. The SBPFM prototype has been tested in controlled laboratory sediment interface models. The results show good agreement between the SBPFM calculated and the applied water and

  12. Application of in-situ passive samplers for the investigation of the impacts of vegetated river beds on mineral N concentration gradients in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Ullah, S.; Zhang, H.; Heathwaite, L.; Lansdown, K.; Heppell, K.; Binley, A.; Trimmer, M.; Keenan, P.

    2010-12-01

    Conventional pore water sampling techniques have only a limitated capability to provide fine scale (cm or mm) depth resolution of chemical species associated with a ‘hotspot’ or a ‘hot event' in riverine hyporheic zones. To overcome this limitation, in-situ passive samplers (diffusive equilibrium in thin films-DET) were deployed in hyporheic sediments (0-30 cm depth) both under vegetated beds (dominated by Phragmites, spp.) and non-vegetated beds of a groundwater-fed river in Cumbria, UK. The riverbed environment consisted of coarse gravels and sandstone, requiring development of a new methodology for inserting the DET probes. The objectives were two-fold; 1) to explore the feasibility of DET deployment in hyporheic sediments dominated by gravels, and 2) to assess the impacts of vegetated beds on mineral N concentration gradients (cm scale resolution) to those under non-vegetated beds of the riverbed. The challenge of deploying DET in gravel bed sediments was met. Resulting information on fine scale gradients of mineral N and other redox sensitive species can improve our understanding of the dynamics of hyporheic mineral N species. According to the results, hyporheic sediments under vegetation exhibited significantly lower nitrate concentration gradients compared to non-vegetated hyporheic sediments. A dense piezometer network installed at the site showed that both locations possessed an upwelling potential at the time of DET deployment, and the amount of dissolved organic C was high in the hyporheic under reeds relative to the non-vegetated zones. These preliminary results suggest that vegetated beds in rivers could be effective in removing NO3 through denitrification and plant uptake besides rendering other ecosystem services such as habitat provision.

  13. Ambient groundwater flow diminishes nitrate processing in the hyporheic zone of streams

    NASA Astrophysics Data System (ADS)

    Azizian, Morvarid; Boano, Fulvio; Cook, Perran L. M.; Detwiler, Russell L.; Rippy, Megan A.; Grant, Stanley B.

    2017-05-01

    Modeling and experimental studies demonstrate that ambient groundwater reduces hyporheic exchange, but the implications of this observation for stream N-cycling is not yet clear. Here we utilize a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N-cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the United States). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but overpredicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3-11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damköhler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.

  14. Biofilm-induced bioclogging produces sharp interfaces in hyporheic flow, redox conditions, and microbial community structure

    NASA Astrophysics Data System (ADS)

    Caruso, Alice; Boano, Fulvio; Ridolfi, Luca; Chopp, David L.; Packman, Aaron

    2017-05-01

    Riverbed sediments host important biogeochemical processes that play a key role in nutrient dynamics. Sedimentary nutrient transformations are mediated by bacteria in the form of attached biofilms. The influence of microbial metabolic activity on the hydrochemical conditions within the hyporheic zone is poorly understood. We present a hydrobiogeochemical model to assess how the growth of heterotrophic and autotrophic biomass affects the transport and transformation of dissolved nitrogen compounds in bed form-induced hyporheic zones. Coupling between hyporheic exchange, nitrogen metabolism, and biomass growth leads to an equilibrium between permeability reduction and microbial metabolism that yields shallow hyporheic flows in a region with low permeability and high rates of microbial metabolism near the stream-sediment interface. The results show that the bioclogging caused by microbial growth can constrain rates and patterns of hyporheic fluxes and microbial transformation rate in many streams.

  15. The bacterivory of interstitial ciliates in association with bacterial biomass and production in the hyporheic zone of a lowland stream.

    PubMed

    Königs, Sascha; Cleven, Ernst-Josef

    2007-07-01

    Rates of bacteria ingestion by interstitial ciliates were estimated and compared to bacterial biomass and production. Investigation was carried out in the hyporheic zone of a lowland stream. FISH was applied to quantitatively determine bacteria within the ciliate's food vacuoles. To estimate bacteria ingestion rates using FISH, we had to strike a new path. When numbers of bacteria in the food vacuoles remains constant with time (bacterial digestion and ingestion are at equilibrium), ingestion rate can be estimated based on the digestion time and the average number of bacteria per cell. Ciliate community was predominantly composed of bacterivorous ciliates. FISH-signals deriving from ingested bacteria were detected in Cinetochilum margaritaceum, 'other small scuticociliates', Pleuronema spp., and Vorticella spp. Ingestion rates for these taxa were 78, 150, 86, and 38 bacteria ind(-1) h(-1), respectively. The grazing impacts on bacterial biomass and carbon production were calculated based on these ingestion rates. Ciliate grazing caused a decrease in bacterial biomass of 0.024% day(-1) and in bacterial carbon production of 1.60%. These findings suggest that interstitial ciliate grazing impact on bacteria biomass and production was too low to represent an important link in the carbon flow of the hyporheic zone under study.

  16. Functional and Structural Responses of Hyporheic Biofilms to Varying Sources of Dissolved Organic Matter

    PubMed Central

    Wagner, Karoline; Bengtsson, Mia M.; Besemer, Katharina; Sieczko, Anna; Burns, Nancy R.; Herberg, Erik R.

    2014-01-01

    Headwater streams are tightly connected with the terrestrial milieu from which they receive deliveries of organic matter, often through the hyporheic zone, the transition between groundwater and streamwater. Dissolved organic matter (DOM) from terrestrial sources (that is, allochthonous) enters the hyporheic zone, where it may mix with DOM from in situ production (that is, autochthonous) and where most of the microbial activity takes place. Allochthonous DOM is typically considered resistant to microbial metabolism compared to autochthonous DOM. The composition and functioning of microbial biofilm communities in the hyporheic zone may therefore be controlled by the relative availability of allochthonous and autochthonous DOM, which can have implications for organic matter processing in stream ecosystems. Experimenting with hyporheic biofilms exposed to model allochthonous and autochthonous DOM and using 454 pyrosequencing of the 16S rRNA (targeting the “active” community composition) and of the 16S rRNA gene (targeting the “bulk” community composition), we found that allochthonous DOM may drive shifts in community composition whereas autochthonous DOM seems to affect community composition only transiently. Our results suggest that priority effects based on resource-driven stochasticity shape the community composition in the hyporheic zone. Furthermore, measurements of extracellular enzymatic activities suggest that the additions of allochthonous and autochthonous DOM had no clear effect on the function of the hyporheic biofilms, indicative of functional redundancy. Our findings unravel possible microbial mechanisms that underlie the buffering capacity of the hyporheic zone and that may confer stability to stream ecosystems. PMID:25063654

  17. Effects of Fluctuating River flow on Groundwater/Surface Water Mixing in the Hyporheic Zone of a Regulated, Large Cobble Bed River

    SciTech Connect

    Arntzen, Evan V.; Geist, David R.; Dresel, P. Evan

    2006-10-31

    Physicochemical relationships in the boundary zone between groundwater and surface water (i.e., the hyporheic zone) are controlled by surface water hydrology and the hydrogeologic properties of the riverbed. We studied how sediment permeability and river discharge altered the vertical hydraulic gradient (VHG) and water quality of the hyporheic zone within the Hanford Reach of the Columbia River. The Columbia River at Hanford is a large, cobble-bed river where water level fluctuates up to 2 m daily because of hydropower generation. Concomitant with recording river stage, continuous readings were made of water temperature, specific conductance, dissolved oxygen, and water level of the hyporheic zone. The water level data were used to calculate VHG between the river and hyporheic zone. Sediment permeability was estimated using slug tests conducted in piezometers installed into the river bed. The response of water quality measurements and VHG to surface water fluctuations varied widely among study sites, ranging from no apparent response to co-variance with river discharge. At some sites, a hysteretic relationship between river discharge and VHG was indicated by a time lag in the response of VHG to changes in river stage. The magnitude, rate of change, and hysteresis of the VHG response varied the most at the least permeable location (hydraulic conductivity (K) = 2.9 x 10-4 cms-1), and the least at the most permeable location (K=8.0 x 10-3 cms-1). Our study provides empirical evidence that sediment properties and river discharge both control the water quality of the hyporheic zone. Regulated rivers, like the Columbia River at Hanford, that undergo large, frequent discharge fluctuations represent an ideal environment to study hydrogeologic processes over relatively short time scales (i.e., days to weeks) that would require much longer periods of time to evaluate (i.e., months to years) in un-regulated systems.

  18. Linking hyporheic flow and nitrogen cycling near the Willamette River - A large river in Oregon, USA

    USGS Publications Warehouse

    Hinkle, S.R.; Duff, J.H.; Triska, F.J.; Laenen, A.; Gates, E.B.; Bencala, K.E.; Wentz, D.A.; Silva, S.R.

    2001-01-01

    strong vertical redox gradient was observed, with nitrate-limited denitrification potential in deeper sediment and both nitrification and denitrification potential in shallower sediment. Since nitrogen cycling is strongly affected by redox conditions, nitrogen cycling in the hyporheic zone of this large-river system likely is affected by dynamics of ground water/surface water interactions that control fluxes of nitrogen and other redox species to hyporheic zone sediment.

  19. Temperature effects on nitrogen cycling and nitrate removal-production efficiency in bed form-induced hyporheic zones

    NASA Astrophysics Data System (ADS)

    Zheng, Lizhi; Cardenas, M. Bayani; Wang, Lichun

    2016-04-01

    Hyporheic flow in aquatic sediment controls solute and heat transport thereby mediating the fate of nutrients and contaminants, dissolved oxygen, and temperature in the hyporheic zone (HZ). We conducted a series of numerical simulations of hyporheic processes within a dune with different uniform temperatures, coupling turbulent open channel fluid flow, porous fluid flow, and reactive solute transport to study the temperature dependence of nitrogen source/sink functionality and its efficiency. Two cases were considered: a polluted stream and a pristine stream. Sensitivity analysis was performed to investigate the influence of stream water [NO3-]/[NH4+]. The simulations showed that in both cases warmer temperatures resulted in shallower denitrification zones and oxic-anoxic zone boundaries, but the trend of net denitrification rate and nitrate removal or production efficiency of the HZ for these two cases differed. For both cases, at high [NO3-]/[NH4+], the HZ functioned as a NO3- sink with the nitrate removal efficiency increasing with temperature. But at low [NO3-]/[NH4+] for the polluted stream, the HZ is a NO3- sink at low temperature but then switches to a NO3- source at warmer temperatures. For the pristine stream case, the HZ was always a NO3- source, with the NO3- production efficiency increasing monotonically with temperature. In addition, although the interfacial fluid flux expectedly increased with increasing temperature due to decreasing fluid viscosity, the total nitrate flux into the HZ did not follow this trend. This is because when HZ nitrification is high, uniformly elevated [NO3-] lowers dispersive fluxes into the HZ. We found that there are numerous confounding and interacting factors that combined to lead to the final temperature dependence of N transformation reaction rates. Although the temperature effect on the rate constant can be considered as the dominant factor, simply using the Arrhenius equation to predict the reaction rate would lead to

  20. Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona

    USGS Publications Warehouse

    Fuller, Christopher C.; Bargar, John R.

    2014-01-01

    The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (μSXRF) mapping, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.

  1. Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona.

    PubMed

    Fuller, Christopher C; Bargar, John R

    2014-02-18

    The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (μSXRF) mapping, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.

  2. Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona

    PubMed Central

    Fuller, Christopher C.; Bargar, John R.

    2014-01-01

    The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using micro-focused Extended X-ray Absorption Fine Structure (EXAFS) and X-ray fluorescence (μSXRF) mapping , bulk EXAFS, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and micro-focused EXAFS spectra of Zn in the biogenic Mn oxides coating are indicative of Zn forming triple corner sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to decreasing in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in solid to solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating desorption is not controlled by dissolution of secondary Zn phases. In sum, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process in Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present. PMID:24460038

  3. Use of an Instrumented Mini-Well Matrix to Document Hydraulic and Transport Fluctuations in the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Hinlein, E. S.; Ostendorf, D. W.

    2010-12-01

    A matrix of mini-wells was installed and instrumented to monitor the hyporheic zone linking a river and its floodplain deposit in Eastern Massachusetts. The Neponset River is of small to moderate size with seasonal approximate depths ranging from 1-3 m, widths of 5-15 m, and flows varying from 0.3-28 m3/s in the study area adjacent to a major interstate highway. Transport in the hyporheic zone is governed by the floodplain deposit and the river which combine to induce diurnal timescale dispersive mixing. A low steady groundwater gradient drives transport toward the river at a rate of approximately 10 meters per year. The floodplain deposit is made up of silty sand to a depth of 21 m underlain by 9 m of low permeability medium silt. The mini-well installation is in the medium silt river bank. Because of the presence of conductive ions in the floodplain deposit, it is possible to use the mini-well matrix to document a front where groundwater and river water meet both through changes in hydraulic head and groundwater conductivity. Specific conductivity values are in the range of 500 uS/cm in the river and 1500 uS/cm in the adjacent 4.5 m deep well 15 m away. Four clusters of existing monitoring wells currently measure head and conductivity outside the hyporheic zone in 4.5 m deep wells along a line from 15-300 m away from the river. A monitoring station at the river measures river level and conductivity. The mini-well matrix captures the final 15 m between the last well cluster and the river. Data from the existing well cluster adjacent to the hyporheic zone shows response to high river levels on the order of 12-24 hrs, with a predicted excursion amplitude of 1 m in response to a hydrograph amplitude of 2 m from a storm of Feb, 2010. The mini-well matrix will measure the horizontal excursions as well as vertical gradients of head and conductivity. Due to complications associated with river bank topography and the sensitivity of the area, the mini-wells were installed

  4. Water-sediment exchanges control microbial processes associated with leaf litter degradation in the hyporheic zone: a microcosm study.

    PubMed

    Navel, Simon; Mermillod-Blondin, Florian; Montuelle, Bernard; Chauvet, Eric; Simon, Laurent; Marmonier, Pierre

    2011-05-01

    The present study aimed to experimentally quantify the influence of a reduction of surface sediment permeability on microbial characteristics and ecological processes (respiration and leaf litter decomposition) occurring in the hyporheic zone (i.e. the sedimentary interface between surface water and groundwater). The physical structure of the water-sediment interface was manipulated by adding a 2-cm layer of coarse sand (unclogged systems) or fine sand (clogged systems) at the sediment surface of slow filtration columns filled with a heterogeneous gravel/sand sedimentary matrix. The influence of clogging was quantified through measurements of hydraulic conductivity, water chemistry, microbial abundances and activities and associated processes (decomposition of alder leaf litter inserted at a depth of 9 cm in sediments, oxygen and nitrate consumption by microorganisms). Fine sand deposits drastically reduced hydraulic conductivity (by around 8-fold in comparison with unclogged systems topped by coarse sand) and associated water flow, leading to a sharp decrease in oxygen (reaching less than 1 mg L(-1) at 3 cm depth) and nitrate concentrations with depth in sediments. The shift from aerobic to anaerobic conditions in clogged systems favoured the establishment of denitrifying bacteria living on sediments. Analyses performed on buried leaf litter showed a reduction by 30% of organic matter decomposition in clogged systems in comparison with unclogged systems. This reduction was linked to a negative influence of clogging on the activities and abundances of leaf-associated microorganisms. Finally, our study clearly demonstrated that microbial processes involved in organic matter decomposition were dependent on hydraulic conductivity and oxygen availability in the hyporheic zone.

  5. The dark side of the hyporheic zone: Depth profiles of nitrogen and its processing in stream sediments

    USGS Publications Warehouse

    Stelzer, R.S.; Bartsch, L.A.; Richardson, W.B.; Strauss, E.A.

    2011-01-01

    1.Although it is well known that sediments can be hot spots for nitrogen transformation in streams, many previous studies have confined measurements of denitrification and nitrate retention to shallow sediments (<5cm deep). We determined the extent of nitrate processing in deeper sediments of a sand plains stream (Emmons Creek) by measuring denitrification in core sections to a depth of 25cm and by assessing vertical nitrate profiles, with peepers and piezometers, to a depth of 70cm. 2.Denitrification rates of sediment slurries based on acetylene block were higher in shallower core sections. However, core sections deeper than 5cm accounted for 68% of the mean depth-integrated denitrification rate. 3.Vertical hydraulic gradient and vertical profiles of pore water chloride concentration suggested that deep ground water upwelled through shallow sediments before discharging to the stream channel. The results of a two-source mixing model based on chloride concentrations suggested that the hyporheic zone was very shallow (<5cm) in Emmons Creek. 4.Vertical profiles showed that nitrate concentration in shallow ground water was about 10-60% of the nitrate concentration of deep ground water. The mean nitrate concentrations of deep and shallow ground water were 2.17 and 0.73mgNO3-NL-1, respectively. 5.Deep ground water tended to be oxic (6.9mgO2L-1) but approached anoxia (0.8mgO2L-1) after passing through shallow, organic carbon-rich sediments, which suggests that the decline in the nitrate concentrations of upwelling ground water was because of denitrification. 6.Collectively, our results suggest that there is substantial nitrate removal occurring in deep sediments, below the hyporheic zone, in Emmons Creek. Our findings suggest that not accounting for nitrate removal in deep sediments could lead to underestimates of nitrogen processing in streams and catchments. ?? 2011 Blackwell Publishing Ltd.

  6. The Physical, Geochemical and Microbial Conditions and Processes in the Hyporheic Zone of a Large Tidally Influenced River: The Fraser River, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Bianchin, M.; Roschinski, T.; Ross, K.; Leslie, S.; William, M.; Beckie, R.

    2006-12-01

    The objective of this research is to investigate the physical, chemical and biological conditions and processes that occur in the hyporheic zone of the lower Fraser River, British Columbia. The large flows of between 2000 and 10000 cubic meters per second, the 10 15 m deep, 250 m wide channel, the 1 m tidal fluctuations, the localized scour and redeposition of sediments during freshet and the strong geochemical contrast between groundwater and surface water distinguish this investigation from studies on smaller channels and streams and required the development of novel characterization tools and strategies. The geochemistry of water samples collected with a push-in profiler, bulk electrical conductivity (EC) measurements collected with a push-in tool and hydraulic head measurements indicate that groundwater principally discharges into the river approximately 100 m offshore in a 10 m wide band. River water and groundwater mix to a maximum depth of between 0.75 and 1.5 m. While hydraulic heads show strong tidal reversals, bulk EC profiles show only moderate changes during the tidal cycle. It was hypothesized that high iron (10's mg/L of Fe(II)) in reduced groundwater would precipitate from solution as secondary iron-oxide phases in the zone where groundwater mixes with aerobic river water. Sediments were collected with a freeze-shoe corer and depth profiles through the hyporheic zone and into the underlying aquifer were analyzed by selective extractions. The 15-30 mg/g of total extractable iron in both the aquifer and hyporheic zone is relatively high. The lack of noticeable iron accumulation in the hyporheic zone may indicate that iron precipitates on shallow sediments that are subsequently scoured from the river bed during freshet. Microbial DNA from sediments was analyzed using denaturing gradient gel electrophoresis and showed a relatively diverse community structure but an overall low biomass.

  7. Groundwater flow, nutrient, and stable isotope dynamics in the parafluvial-hyporheic zone of the regulated Lower Colorado River (Texas, USA) over the course of a small flood

    NASA Astrophysics Data System (ADS)

    Briody, Alyse C.; Cardenas, M. Bayani; Shuai, Pin; Knappett, Peter S. K.; Bennett, Philip C.

    2016-06-01

    Periodic releases from an upstream dam cause rapid stage fluctuations in the Lower Colorado River near Austin, Texas, USA. These daily pulses modulate fluid exchange and residence times in the hyporheic zone where biogeochemical reactions are typically pronounced. The effects of a small flood pulse under low-flow conditions on surface-water/groundwater exchange and biogeochemical processes were studied by monitoring and sampling from two dense transects of wells perpendicular to the river. The first transect recorded water levels and the second transect was used for water sample collection at three depths. Samples were collected from 12 wells every 2 h over a 24-h period which had a 16-cm flood pulse. Analyses included nutrients, carbon, major ions, and stable isotopes of water. The relatively small flood pulse did not cause significant mixing in the parafluvial zone. Under these conditions, the river and groundwater were decoupled, showed potentially minimal mixing at the interface, and did not exhibit any discernible denitrification of river-borne nitrate. The chemical patterns observed in the parafluvial zone can be explained by evaporation of groundwater with little mixing with river water. Thus, large pulses may be necessary in order for substantial hyporheic mixing and exchange to occur. The large regulated river under a low-flow and small flood pulse regime functioned mainly as a gaining river with little hydrologic connectivity beyond a narrow hyporheic zone.

  8. Dissolved oxygen concentration profiles in the hyporheic zone through the use of a high density fiber optic measurement network

    NASA Astrophysics Data System (ADS)

    Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

    2013-12-01

    The hyporheic zone (HZ) is a potentially important source of the potent greenhouse gas, nitrous oxide (N2O); stream processes may account for up to 10% of global anthropogenic N2O emissions. However, mechanistic understanding and predictive quantification of this gas flux is hampered by complex temporally and spatially variable interactions between flow dynamics and biogeochemical processes. Reactive inorganic nitrogen (Nr) is typically present at low concentrations in natural stream waters, but many rural and urban streams suffer from an excess of Nr, typically in the form of ammonium (NH4+) and nitrate (NO3-). These reactive species are either assimilated by living biomass or transformed by microbial processes. The two primary microbial transformations of Nr are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2). Denitrification, which occurs almost exclusively in the anoxic zone of the HZ, permanently removes between 30-70% of all Nr entering streams, other mechanisms may retain nitrogen. The mass transport of reactive species (i.e. O2, NO3- and N2O) by hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O flux. By extension, stream flow and channel morphology presumably control, and may be effective predictors of, N2O generation rates. By recreating the stream processes in the University of Idaho flume, we are able to control the bed morphology, fluxes and residence times through the HZ and concentrations of Nr from exogenous (stream water) and endogenous (organic material in the streambed) sources. For the present experiment, the flume was divided into three streams, each with different morphologies (3, 6 and 9cm dunes) and all using the same source water. Stream water for this first experimental phase had no significant loading of Nr. As such, all reaction products were the result of endogenous sources of Nr. To measure dissolved oxygen (DO) concentrations we deployed 120 channels of a novel, fiber-optic optode

  9. Modeling Hyporheic Flux Along a Second-Order Semi-arid Stream: Red Canyon Creek, Wyoming

    NASA Astrophysics Data System (ADS)

    Lautz, L. K.; Siegel, D. I.

    2004-12-01

    Models of near-stream hyporheic exchange flows are difficult to prepare because geomorphic stream features and adjacent subsurface characteristics both affect groundwater-surface water interaction. Inverse models of the results of in-stream tracer tests characterize net short time-scale hyporheic exchange along reaches, but not the actual physical processes driving the exchange. In contrast, numerical groundwater flow models simulate near-stream and hyporheic flow driven by hydraulic gradients from a physical process perspective. In this paper, we present a three-dimensional MODFLOW model of hyporheic exchange along a lower riparian reach of Red Canyon Creek, Wyoming. We calibrated the model results to hydraulic head measurements from > 30 monitoring wells, piezometers, in-stream mini-piezometers, and to changes in stream discharge measured by in-stream tracer tests. We also simulated hyporheic flow paths with MODPATH (a particle-tracking package), from which we obtained residence times of water parcels in the hyporheic zone. Hydraulic gradients around in-stream flow obstructions, such as beaver dams, and through meander bends, cause most near-stream hyporheic exchange (residence time <30 days). Hyporheic residence times <10 days occur only along flow paths around beaver dams. We also simulated stream solutes moving into the subsurface with MT3D, a solute transport package, and operationally defined the hyporheic zone as places where solute concentrations were equal to or greater than 10% of the stream water concentration after a 10-day model simulation. The results of this modeling agreed with MODPATH; solutes move both horizontally and vertically from streams into the subsurface behind debris dams, which create hydraulic steps in the subsurface and surface flow systems.

  10. Suitability of temperature, hydraulic heads, and acesulfame to quantify wastewater-related fluxes in the hyporheic and riparian zone

    NASA Astrophysics Data System (ADS)

    Engelhardt, Irina; Prommer, Henning; Moore, Catherine; Schulz, Manoj; Schüth, Christoph; Ternes, Thomas A.

    2013-01-01

    Groundwater and surface water are in many cases closely linked components of the water cycle with respect to both quantity and quality. Bank filtrates may eventually be impacted by the infiltration of wastewater-derived micropollutants from surface waters. Artificial sweeteners such as acesulfame have recently been reported as a novel class of potentially valuable tracers to study the fate of wastewater-derived substances in groundwater and, in particular, to determine the (bio)degradability of micropollutants. In this paper, a model-based analysis of a field experiment within the hyporheic and riparian zone of a highly polluted German stream was performed to assess the physical and chemical behavior of the artificial sweetener acesulfame. In the first part of this study, a reliable flow and transport model was established by jointly using hydraulic heads, temperatures, and acesulfame concentrations as inverse model calibration constraints. The analysis confirmed the conservative behavior of acesulfame and, therefore, its usability as an indicator of sewage flux provenance. However, a comparison of the appropriateness of hydraulic head, temperature, and acesulfame concentrations revealed that the characterization of the surface water-groundwater flux data indicated diurnal temperature fluctuations are the best indicator in terms of characterizing the flow and transport behavior in the groundwater system.

  11. Interactions Between Diffuse Groundwater Recharge and Hyporheic Zone Chemistry in Spring-Fed River: Implications for Metal, Nutrient & Carbonate Cycling

    NASA Astrophysics Data System (ADS)

    Kurz, M. J.; Martin, J. B.; Cohen, M.

    2012-12-01

    Diffuse groundwater flow through stream-bed sediments can represent water with a chemically distinct composition, influencing elemental cycling and ecosystem dynamics. Diffuse flow may be particularly important in systems where hyporheic exchange is small. The entirely spring-sourced Ichetucknee River (north-central Florida) is a model system for distinguishing the processes controlling solute sources and cycling due to its stable discharge (6-9 m3/s), constant but distinct spring chemistry through time, and minimal hyporheic exchange. Most stream solute concentrations exhibit large diel cycles, but these changes do not explain all observed longitudinal changes in river chemistry. Ca, Fe, and PO4 concentrations are all elevated in river water over the flow-weighted average of the source springs (Ca = 1.37 vs 1.31 mM; Fe = 8 vs. 0.4 μg/L; PO4 = 54 vs. 49 μg/L) despite evidence of in-stream removal of these solutes by biotic and abiotic processes. Cl concentrations are also elevated in the river over the spring sources and previous calculations estimated an additional 0.75 m3/s of water was needed to close the Cl budget of the river. Diffuse groundwater flow could be the source of these additional solutes and flow. To estimate the impact of diffuse flow interacting with hyporheic zone chemistry on the metal, nutrient, and carbonate chemistry of the Ichetucknee River we compared the chemistry of the springs and river with measurements of pore-water chemistry and hydraulic gradients within the unconsolidated channel sediments. A cross-river transect of four pore-water chemical profiles indicate that pore-water chemistry is dominated by the mineralization of organic carbon, resulting in pore-waters undersaturated with respect to calcite and elevated in Ca, Fe, and PO4 concentrations (ca. 1.44 mM, 2000 μg/L, and 150-300 μg/L, respectively) relative to the river. A diffuse flow rate through the river sediments of 0.2-0.7 m3/s, would account for the addition of both PO

  12. Hydraulic controls of in-stream gravel bar hyporheic exchange and reactions

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Vieweg, Michael; Oswald, Sascha E.; Fleckenstein, Jan H.

    2015-04-01

    Hyporheic exchange transports solutes into the subsurface where they can undergo biogeochemical transformations, affecting fluvial water quality and ecology. A three-dimensional numerical model of a natural in-stream gravel bar (20 m × 6 m) is presented. Multiple steady state streamflow is simulated with a computational fluid dynamics code that is sequentially coupled to a reactive transport groundwater model via the hydraulic head distribution at the streambed. Ambient groundwater flow is considered by scenarios of neutral, gaining, and losing conditions. The transformation of oxygen, nitrate, and dissolved organic carbon by aerobic respiration and denitrification in the hyporheic zone are modeled, as is the denitrification of groundwater-borne nitrate when mixed with stream-sourced carbon. In contrast to fully submerged structures, hyporheic exchange flux decreases with increasing stream discharge, due to decreasing hydraulic head gradients across the partially submerged structure. Hyporheic residence time distributions are skewed in the log-space with medians of up to 8 h and shift to symmetric distributions with increasing level of submergence. Solute turnover is mainly controlled by residence times and the extent of the hyporheic exchange flow, which defines the potential reaction area. Although streamflow is the primary driver of hyporheic exchange, its impact on hyporheic exchange flux, residence times, and solute turnover is small, as these quantities exponentially decrease under losing and gaining conditions. Hence, highest reaction potential exists under neutral conditions, when the capacity for denitrification in the partially submerged structure can be orders of magnitude higher than in fully submerged structures.

  13. Hyporheic exchange along a river below a dam

    Treesearch

    Alessandra Marzadri; Daniele Tonina; James A. McKean; Matt Tiedemann

    2012-01-01

    Hyporheic exchange is an important mechanism for solute mixing between river waters and shallow groundwater in streambed sediment. The hyporheic zone also provides an important ecotone for benthic species, including macro-invertebrates, microorganisms, and parts of some fish life stages. Most hyporheic analyses are limited in scope and performed at the reach scale....

  14. Comparison of Whole-stream and Hyporheic-zone Estimates of Denitrification Determined Simultaneously During an Isotope Tracer Injection in a Nitrate-Rich Stream

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Bohlke, J. K.; Voytek, M. A.

    2005-05-01

    15N labeled nitrate is increasingly being used as a reactive tracer in stream tracer tests to estimate whole-stream denitrification averaged at a spatial scale large enough to allow comparisons across disparate stream ecosystems. No matter how valuable, these whole-stream estimates are not very informative about controlling processes and will have limited transfer value unless processes controlling denitrification are investigated simultaneously at finer scales. Insights about the processes that influence the whole-stream rates could be especially informative if simultaneous rate measurements are made representing variable hydrologic and biogeochemical conditions near reactive surfaces in the stream and in the streambed. Our approach was to investigate factors that control denitrification by simultaneously measuring denitrification in-situ in a variety of streambed environments by sampling evolution of the (15NO3-) tracer during transport through shallow hyporheic flow paths. Here we report results from two tracer studies conducted in Sugar Creek, western Indiana, in a basin dominated by corn and soybean agriculture. The two tracer experiments were conducted in September 2001 and September 2003, when streamflows (40 and 20 L s-1) and stream NO3- concentrations (70 and 175 μmoles L-1) in the two reaches were near their annual minimum values. The experiments involved co-injection of conservative (Br), reactive (15NO3-), and dissolved gas (SF6) tracers into streamflow allowing quantification of advection, dispersion, gas evasion, hydrologic retention in "storage" zones, and also allowing in-situ estimation of denitrification within selected hyporheic flow paths. The experiments resulted in estimates of both whole-stream and hyporheic-zone rates of denitrification and related nitrogen reactions. The streambed of Sugar Creek is covered in most areas with a relatively thin layer (ranging from <1 to 3 cm) of fine granular and organic sediment and periphyton, overlying a

  15. Characterization of Macroinvertebrate Communities in the Hyporheic Zone of River Ecosystems Reflects the Pump-Sampling Technique Used

    PubMed Central

    Dole-Olivier, Marie-José; Galassi, Diana M. P.; Hogan, John-Paul; Wood, Paul J.

    2016-01-01

    The hyporheic zone of river ecosystems provides a habitat for a diverse macroinvertebrate community that makes a vital contribution to ecosystem functioning and biodiversity. However, effective methods for sampling this community have proved difficult to establish, due to the inaccessibility of subsurface sediments. The aim of this study was to compare the two most common semi-quantitative macroinvertebrate pump-sampling techniques: Bou-Rouch and vacuum-pump sampling. We used both techniques to collect replicate samples in three contrasting temperate-zone streams, in each of two biogeographical regions (Atlantic region, central England, UK; Continental region, southeast France). Results were typically consistent across streams in both regions: Bou-Rouch samples provided significantly higher estimates of taxa richness, macroinvertebrate abundance, and the abundance of all UK and eight of 10 French common taxa. Seven and nine taxa which were rare in Bou-Rouch samples were absent from vacuum-pump samples in the UK and France, respectively; no taxon was repeatedly sampled exclusively by the vacuum pump. Rarefaction curves (rescaled to the number of incidences) and non-parametric richness estimators indicated no significant difference in richness between techniques, highlighting the capture of more individuals as crucial to Bou-Rouch sampling performance. Compared to assemblages in replicate vacuum-pump samples, multivariate analyses indicated greater distinction among Bou-Rouch assemblages from different streams, as well as significantly greater consistency in assemblage composition among replicate Bou-Rouch samples collected in one stream. We recommend Bou-Rouch sampling for most study types, including rapid biomonitoring surveys and studies requiring acquisition of comprehensive taxon lists that include rare taxa. Despite collecting fewer macroinvertebrates, vacuum-pump sampling remains an important option for inexpensive and rapid sample collection. PMID:27723819

  16. Characterization of Macroinvertebrate Communities in the Hyporheic Zone of River Ecosystems Reflects the Pump-Sampling Technique Used.

    PubMed

    Stubbington, Rachel; Dole-Olivier, Marie-José; Galassi, Diana M P; Hogan, John-Paul; Wood, Paul J

    2016-01-01

    The hyporheic zone of river ecosystems provides a habitat for a diverse macroinvertebrate community that makes a vital contribution to ecosystem functioning and biodiversity. However, effective methods for sampling this community have proved difficult to establish, due to the inaccessibility of subsurface sediments. The aim of this study was to compare the two most common semi-quantitative macroinvertebrate pump-sampling techniques: Bou-Rouch and vacuum-pump sampling. We used both techniques to collect replicate samples in three contrasting temperate-zone streams, in each of two biogeographical regions (Atlantic region, central England, UK; Continental region, southeast France). Results were typically consistent across streams in both regions: Bou-Rouch samples provided significantly higher estimates of taxa richness, macroinvertebrate abundance, and the abundance of all UK and eight of 10 French common taxa. Seven and nine taxa which were rare in Bou-Rouch samples were absent from vacuum-pump samples in the UK and France, respectively; no taxon was repeatedly sampled exclusively by the vacuum pump. Rarefaction curves (rescaled to the number of incidences) and non-parametric richness estimators indicated no significant difference in richness between techniques, highlighting the capture of more individuals as crucial to Bou-Rouch sampling performance. Compared to assemblages in replicate vacuum-pump samples, multivariate analyses indicated greater distinction among Bou-Rouch assemblages from different streams, as well as significantly greater consistency in assemblage composition among replicate Bou-Rouch samples collected in one stream. We recommend Bou-Rouch sampling for most study types, including rapid biomonitoring surveys and studies requiring acquisition of comprehensive taxon lists that include rare taxa. Despite collecting fewer macroinvertebrates, vacuum-pump sampling remains an important option for inexpensive and rapid sample collection.

  17. The role of water exchange between a stream channel and its hyporheic zone in nitrogen cycling at the terrestrial-aquatic interface

    USGS Publications Warehouse

    Triska, F.J.; Duff, J.H.; Avanzino, R.J.

    1993-01-01

    The subsurface riparian zone was examined as an ecotone with two interfaces. Inland is a terrestrial boundary, where transport of water and dissolved solutes is toward the channel and controlled by watershed hydrology. Streamside is an aquatic boundary, where exchange of surface water and dissolved solutes is bi-directional and flux is strongly influenced by channel hydraulics. Streamside, bi-directional exchange of water was qualitatively defined using biologically conservative tracers in a third order stream. In several experiments, penetration of surface water extended 18 m inland. Travel time of water from the channel to bankside sediments was highly variable. Subsurface chemical gradients were indirectly related to the travel time. Sites with long travel times tended to be low in nitrate and DO (dissolved oxygen) but high in ammonium and DOC (dissolved organic carbon). Sites with short travel times tended to be high in nitrate and DO but low in ammonium and DOC. Ammonium concentration of interstitial water also was influenced by sorption-desorption processes that involved clay minerals in hyporheic sediments. Denitrification potential in subsurface sediments increased with distance from the channel, and was limited by nitrate at inland sites and by DO in the channel sediments. Conversely, nitrification potential decreased with distance from the channel, and was limited by DO at inland sites and by ammonium at channel locations. Advection of water and dissolved oxygen away from the channel resulted in an oxidized subsurface habitat equivalent to that previously defined as the hyporheic zone. The hyporheic zone is viewed as stream habitat because of its high proportion of surface water and the occurrence of channel organisms. Beyond the channel's hydrologic exchange zone, interstitial water is often chemically reduced. Interstitial water that has not previously entered the channel, groundwater, is viewed as a terrestrial component of the riparian ecotone. Thus

  18. Floodplain Hyporheic Response under Dam Release Hydrographs

    NASA Astrophysics Data System (ADS)

    Zhou, T.; Ward, A. S.; O'Connor, B. L.; Endreny, T. A.

    2012-12-01

    Hydropower operations cause altered hydrograph patterns downstream of dams, which regulates the direction and magnitude of floodplain and riverbed hyporheic flux. Periodic adjustments in river stage changes temporal and spatial patterns in hydraulic pressure, initiates propagation of lateral and vertical hyporheic flux, and affects the riparian ecological system by changing the hyporheic penetration distance, hyporheic flux rate, and thermal conditions in river banks. While this issue has been largely neglected by watershed scientists and managers, there is the potential to use hyporheic metrics in setting dam release rules and restoring downstream river reaches. In order to evaluate the hyporheic feedbacks of various dam release patterns, this study applied a computational fluid dynamics (CFD) model to simulate the interaction of open water hydrographs on porous media lateral hyporheic exchange for the Green River, Utah, downstream of Flaming Gorge Dam. The CFD initially represented the river as a straight channel with a thick porous media extending from the channel banks and bottom. The dam release hydrographs changed the patterns of hyporheic flux at the river banks, the penetration distance of the hyporheic flux, the subsurface thermal patterns, and the residence time of water in the subsurface. The results suggest the undulating river stage downstream of dam releases can initiate patterns of hyporheic exchange similar to those induced by restoration of river bed morphology.

  19. A mini drivepoint sampler for measuring pore water solute concentrations in the hyporheic zone of sand-bottom streams

    USGS Publications Warehouse

    Duff, J.H.; Murphy, F.; Fuller, C.C.; Triska, F.J.

    1998-01-01

    A new method for collecting pore-water samples in sand and gravel streambeds is presented. We developed a mini drivepoint solution sampling (MINIPOINT) technique to collect pore-water samples at 2.5-cm vertical resolution. The sampler consisted of six small-diameter stainless steel drivepoints arranged in a 10-cm-diameter circular array. In a simple procedure, the sampler was installed in the streambed to preset drivepoint depths of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 cm. Sampler performance was evaluated in the Shingobee River, Minnesota, and Pinal Creek, Arizona, by measuring the vertical gradient of chloride concentration in pore water beneath the streambed that was established by the uninterrupted injection to the stream for 3 d. Pore-water samples were withdrawn from all drivepoints simultaneously. In the first evaluation, the vertical chloride gradient was unchanged at withdrawal rates between 0.3 and 4.0 ml min-1 but was disturbed at higher rates. In the second evaluation, up to 70 ml of pore water was withdrawn from each drivepoint at a withdrawal rate of 2.5 ml min-1 without disturbing the vertical chloride gradient. Background concentrations of other solutes were also determined with MINIPOINT sampling. Steep vertical gradients were present for biologically reactive solutes such as DO, NH4/+, NO3/-, and dissolved organic C in the top 20 cm of the streambed. These detailed solute profiles in the hyporheic zone could not have been determined without a method for close interval vertical sampling that does not disturb natural hydrologic mixing between stream water and groundwater.

  20. Estimation of hydrological and thermal parameters in the hyporheic zone using a novel Bayesian inverse modeling approach

    NASA Astrophysics Data System (ADS)

    Cucchi, Karina; Flipo, Nicolas; Rivière, Agnès; Rubin, Yoram

    2016-04-01

    Hydrothermal properties of the stream-aquifer interface are key information for modeling water and heat transfers in hydrological basins. Our study introduces an algorithm to estimate hydrological and thermal parameters of the hyporheic zone (HZ), as well as their associated uncertainties. Properties of the HZ are inferred from a combination of head differential time series and vertically-distributed temperature time series measured continually in a HZ vertical profile. Head differential and two temperature time series are used as boundary conditions for the vertical profile; the other temperature time series are used as conditioning measurements. Following the Bayesian framework, model parameters are treated as random variables and we seek to characterize their probability density function (PDF) conditional on the temperature time series. Our algorithm follows the Method of Anchored Distributions (MAD) implemented in the MAD# software. In order to cut down the number of simulations needed, we develop a hybrid discrete-continuous inversion approach. We first identify the most sensitive parameters in a sensitivity analysis, these parameters are characterized with continuous PDFs. Less sensitive parameters are represented with a discrete PDFs using a finite number of discrete outcomes. We use a non-parametric likelihood function and time series dimension reduction techniques in order to calculate posterior PDFs of HZ parameters. We demonstrate the approach on a synthetic study using an analytical solution and then apply it to field measurements gathered in the Avenelles basin, France. We present one application of this approach, the uncertainty-quantified time series of localized stream-aquifer exchanges.

  1. New microbes as causative agents of Ibuprofen degradation capabilities in the hyporheic zone of a lowland stream

    NASA Astrophysics Data System (ADS)

    Njeru, Cyrus; Posselt, Malte; Horn, Marcus A.

    2017-04-01

    Ibuprofen is a non-steroidal anti-inflammatory pain reliever and among pharmaceutical residues detected in aquatic environments. Widespread use of the drug and incomplete removal during waste water treatment results in its persistence in effluents and receiving waters. Potential total removal by microbial activity in the hyporheic zone (HZ) of rivers downstream of wastewater treatment plant discharge sites has been hypothesized. Ibuprofen degradation associated microbial communities in are essentially unknown. To address this hypothesis, two sets of oxic HZ sediment microcosms spiked with ibuprofen only (5, 40, 200 and 400 µM), or ibuprofen and 1 mM acetate were set up under laboratory conditions. Ibuprofen degradation in non-sterile relative to autoclaved sediments indicated removal by microbial degradation. Ibuprofen was completely consumed in the absence and presence of supplemental acetate after approximately 11 and 16 days, respectively. Refeeding of ibuprofen and acetate after the first depletion resulted in complete degradation within 24 hours in all treatments. Metabolites of ibuprofen included 1-, 2-, 3-hydroxy- and carboxyibuprofen. Quantitative real-time PCR revealed no pronounced differences in copy numbers of 16S rRNA gene or transcripts between non-spiked controls and treatments. Time resolved triplicate amplicon Illumina MiSeq sequencing targeting the 16S rRNA genes and transcripts revealed increased relative abundances of Proteobacteria, Acidobacteria, Actinobacteria and Firmicutes in treatments with compared to those without ibuprofen. Alpha-, Beta- and Deltaproteobacteria were most active as indicated by RNA based analyses. Enrichment and isolation yielded new Alphaproteobacteria utilizing ibuprofen as sole carbon and energy source. The collective results indicated that (i) HZ sediments sustain efficient biotic (micro-)pollutant removal and (ii) are a reservoir of hitherto unknown microbial diversity associated with such ecosystem services

  2. The role of the benthic-hyporheic zone in controlling nitrous oxide emissions along two stream networks draining watersheds with contrasting land use

    NASA Astrophysics Data System (ADS)

    Marzadri, Alessandra; Dee, Martha M.; Tonina, Daniele; Tank, Jennifer L.; Bellin, Alberto

    2016-04-01

    Nitrous oxide (N2O) is a potent greenhouse gas responsible of stratospheric ozone destruction. Denitrification in stream ecosystems occurs within the benthic layer at the sediment-water interface and within subsurface environments such as the hyporheic zone and results in N2O production that could be eventually emitted to the atmosphere. Here, we quantify the role of benthic and hyporheic zones as sources of N2O gas and explore the dependence of emissions from stream morphology, flow hydraulics, land use and climate using a recently-developed fully analytical framework. Variations in N2O emissions within and among catchments of contrasting land use can be explained with a new denitrification Damköhler number (DaD) that accounts for denitrification processes within both benthic and hyporheic zones. For initial model development, we found a strong relationship between DaD and stream N2O emissions using field data collected from multiple headwater streams (i.e., LINXII project) from different biomes draining contrasting land use. We then tested its generality by comparing N2O emissions predicted with DaD to those measured using a synoptic sampling campaign in two stream networks draining contrasting land use: Manistee R (Michigan, USA) and Tippecanoe R (Indiana, USA). Our dimensionless analysis shows that the effect of land use disappears after making the emissions dimensionless with respect to the nitrogen load. Reliable predictions of N2O emissions at the stream network scale can be obtained from a limited amount of information, consisting in relatively easy to obtain biogeochemical and hydromorphological quantities.

  3. Functional and structural responses of hyporheic biofilms to varying sources of dissolved organic matter.

    PubMed

    Wagner, Karoline; Bengtsson, Mia M; Besemer, Katharina; Sieczko, Anna; Burns, Nancy R; Herberg, Erik R; Battin, Tom J

    2014-10-01

    Headwater streams are tightly connected with the terrestrial milieu from which they receive deliveries of organic matter, often through the hyporheic zone, the transition between groundwater and streamwater. Dissolved organic matter (DOM) from terrestrial sources (that is, allochthonous) enters the hyporheic zone, where it may mix with DOM from in situ production (that is, autochthonous) and where most of the microbial activity takes place. Allochthonous DOM is typically considered resistant to microbial metabolism compared to autochthonous DOM. The composition and functioning of microbial biofilm communities in the hyporheic zone may therefore be controlled by the relative availability of allochthonous and autochthonous DOM, which can have implications for organic matter processing in stream ecosystems. Experimenting with hyporheic biofilms exposed to model allochthonous and autochthonous DOM and using 454 pyrosequencing of the 16S rRNA (targeting the "active" community composition) and of the 16S rRNA gene (targeting the "bulk" community composition), we found that allochthonous DOM may drive shifts in community composition whereas autochthonous DOM seems to affect community composition only transiently. Our results suggest that priority effects based on resource-driven stochasticity shape the community composition in the hyporheic zone. Furthermore, measurements of extracellular enzymatic activities suggest that the additions of allochthonous and autochthonous DOM had no clear effect on the function of the hyporheic biofilms, indicative of functional redundancy. Our findings unravel possible microbial mechanisms that underlie the buffering capacity of the hyporheic zone and that may confer stability to stream ecosystems. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  4. Effect of Streambed Roughness and Topography on the Solute Transport and Hyporheic Exchanges: Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Chen, Xiaobing; Zhao, Jian; Chen, Li

    2013-04-01

    Hyporheic zones are critical for maintaining river ecosystem as they provide hyporheic and riparian organisms critical solutes, including nutrients and dissolved gases from bedforms to watershed scales. Among the hyporheic driving factors, the streambed topogaraphy is considered as a significant driving factor for hydraulic process in hyporheic zone that has been well documented in the past few decades. Previous research has implied that the rough streambed impact the flow resistance and continuously affect the hydraulic gradient between the river and the streambed. Recent research works focused more on the realistic pressure distribution along the bedform interface (eg. triangular-shaped sand dunes) on a macro level scale, while only few works related to the hyporheic exchanges induced by pore size scaled topography. How and to what extent that pore size scaled bedform would contribute to the total hyporheic discharge is still unclear. Indeed, the mesoscopic uneven topography can disturb the flow regime that near the water-sand interface, for example, it brings turbulent eddies and fluctuating pressure distribution along a rough gravel bed. In our study, a set of flume experiments were setup to examine the pore size roughness impacts on the solute transport and hyporheic exchanges in surface-subsurface system. Six kinds of riverbed sediments with median diameter range from 1.1 mm to 50.2 mm were chosen for comparative analyses. Also, three kinds of triangular shaped bedforms represented by the ratio α (=δ/?, δ is the amplitude and ? is the wavelength) with value of 0.125, 0.17 and 0.25 were considered as the macro-topography driver variation in our experiments. Our tests revealed that under a flat riverbed condition, the vertical diffusion is the main factor for the solute transport in hyporheic zone, however, the hyporheic exchange rate (represented by the decrease rate in concentration of surface water) is significantly enhanced as the growth of gravel grain

  5. Carbon availability and the distribution of denitrifying organisms influence N2O production in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Farrell, T. B.; Quick, A. M.; Reeder, W. J.; Tonina, D.; Benner, S. G.; Feris, K. P.

    2013-12-01

    It has been estimated that 10% of greenhouse gas N2O emissions take place within river networks, with the majority of these processes occurring in the hyporheic zone (HZ). These emissions are the result of microbially-mediated nitrogen transformations (i.e. nitrification and denitrification) and yet the role of microbial distribution and function in this complex system is not well understood. We hypothesized that the concentration and availability of organic carbon influences the production of redox gradients, DIN (via mineralization, nitrification, and loss of DIN via denitrification), and ultimately N2O production in the HZ by controlling the distribution and activity of denitrifying microbial communities. Further, we hypothesized that by linking the distribution of denitrifying microbial communities and their associated functional genes (i.e. the relative abundance of N2O vs. N2 producing genetic elements) to flow dynamics and biogeochemical processes, we can begin to better understand what controls N2O production in hyporheic networks. To address these hypotheses we performed a series of column experiments designed to determine the influence of carbon concentration on redox gradient development and N2O flux along a one-dimensional flow path. Intact sediment cores were amended with 0.01%, 0.05%, 0.15%, and 0.5% dry mass riparian vegetation (>90% Populus sp.) to serve as an endogenous particulate organic matter (POM) source. During quasi-steady state conditions dissolved oxygen (DO), NH4+, NO3-, and N2O levels were measured. As predicted, a positive relationship between the level of POM amendment and development of a gradient of oxic and anoxic conditions was observed. There was negligible N2O production within columns inoculated with 0.01% and 0.05% DOC likely because these POC treatments were too low to create anoxic conditions necessary to stimulate denitrification. Maximum N2O flux was observed with the 0.15% POC treatment. Both oxic and anoxic conditions

  6. Exoenzyme activities as indicators of dissolved organic matter composition in the hyporheic zone of a floodplain river

    Treesearch

    Sandra M. Clinton; Rick T. Edwards; Stuart E.G. Findlay

    2010-01-01

    We measured the hyporheic microbial exoenzyme activities in a floodplain river to determine whether dissolved organic matter (DOM) bioavailability varied with overlying riparian vegetation patch structure or position along flowpaths. Particulate organic matter (POM), dissolved organic carbon (DOC), dissolved oxygen (DO), electrical conductivity and temperature were...

  7. Storm-associated hydrodynamics drive transient solute and redox chemistry within the floodplain aquifer and hyporheic zone of a piedmont stream

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Kaplan, L. A.; Lazareva, O.; Michael, H. A.

    2013-12-01

    Riparian and hyporheic zones are dynamic settings where fluctuations in pore water flow influence redox-sensitive biogeochemical processes and solute transport. We instrumented a riparian-hyporheic zone transect with pressure transducers, redox probes, and pore water samplers to measure hydrology, redox potential, and water chemistry before, during and after Hurricane Sandy in October 2012. The transect spanned opposing, topographically distinct floodplains, consisting of a broad, flat western side and narrow, steep eastern side. The water table on both sides of the stream rose rapidly with rising stage and promoted continuous groundwater discharge to the stream throughout the storm hydrograph. Soil moisture and oxygen isotope data suggest that preferential recharge through macropores drove the rapid water table response. Macropore flow was also implicated in the delivery of oxygenated, carbon-rich water from the land surface into the floodplain aquifer, driving a shift in redox conditions at depth. Groundwater chemistry changed dramatically: DOC concentrations increased while nitrate and metal concentrations decreased. Greater shifts in groundwater chemistry occurred on the steep eastern side and required more time to reestablish after the storm. The eastern floodplain aquifer also drained more rapidly. Topographic variations across the floodplain transect influenced fluid flow paths and residence times that ultimately controlled the spatial and temporal dynamics of groundwater biogeochemistry. Use of paired sensors such as redox and pressure sensors can improve our understanding of hydrobiogeochemical dynamics during storms.

  8. Patterns of hydrological exchange and nutrient transformation in the hyporheic zone of a gravel-bottom stream: examining terrestrial- aquatic linkages

    USGS Publications Warehouse

    Triska, F.J.; Duff, J.H.; Avanzino, R.J.

    1993-01-01

    The terrestrial-aquatic interface beneath a riparian corridor was investigated as a region of hydrological and biological control of nutrient flux. Dissolved oxygen (DO) concentration in the hyporheic zone ranged from <1.0 to 9.5 mg l-1 due to permeability variations in bankside sediments. DO concentration was related to the proportion of stream water in the lateral hyporheic zone, indicating that the channel water was the DO source. The magnitude and timing of lateral water exchange was linked to previously published studies of nitrification and denitrification. Both nitrification potential and channel exchange decreased with distance from the channel and were absent at sites lacking effective exchange, due to low DO. Field amendment of ammonium to an aerobic flow path indicated nitrification potential under natural hydrological conditions. Denitrification potential was inversely related to channel exchange and was insignificant in channel sediments. Field amendment of acetylene plus nitrate to a flow path with low DO and minimal channel exchange indicated denitrification of amended nitrate. -from Authors

  9. Investigating the role of the hyporheic zone in the transformation and fate of nitrogen within an agriculturally impacted catchment

    NASA Astrophysics Data System (ADS)

    Garrard, Nicholas; Hiscock, Kevin; Marca, Alina; Jickells, Tim

    2017-04-01

    The role of the hyporheic zone (HZ) in the attenuation of nitrogen in a catchment impacted by intensive arable agriculture is investigated after mass balance calculations showed a 31% discrepancy between input of nitrogen through fertiliser applications and the flux of nitrate in stream water downstream at the catchment outlet (Wexler, 2012). Measurement of the dual stable isotopes of nitrate together with major ion analysis has been carried out on field drain, stream water and nested in-stream piezometers (at depths of 0.5, 1.0 and 1.5 m below the stream bed). Sampling occurred at five sites along a 1.6 km reach in the Wensum Demonstration Test Catchment (DTC) in eastern England between October 2014 and March 2017. While Wexler (2012) highlighted the potential importance of the HZ in nitrate removal, stable isotope and nitrate concentration data in the present study reveal strong evidence for microbially-mediated denitrification in the soil profile as demonstrated in the field drain samples, while piezometer samples do not follow this same trend. Sampling of end-members (groundwater and stream water samples) reveals enriched δ18ONO3 values in the piezometer samples (+2 to +35‰) relative to groundwater boreholes (+19.65‰ at 15.5 m depth and +18.53‰ at 12 m) and the stream water (+2.0 to +8.5‰), with similar δ15NNO3 values across all sampling locations (+3 to +20‰). A slightly narrower range in δ15NNO3 values is observed in the piezometer samples (+5 to +15‰). The large variability in piezometer samples suggests a sporadic input of high δ18ONO3 material to the HZ, with δ18ONO3 falling in the range of wet and dry deposition of atmospheric nitrate and nitrogen fertiliser. This input could potentially be masking any denitrification signal in the piezometer samples, given the very low concentrations of nitrate ( 0.1 - 5 mg NO3- L) present.

  10. Hydrological Mechanism for Arsenic Deposits in Meghna River Hyporheic Zone Sediments

    NASA Astrophysics Data System (ADS)

    Knappett, Peter; Datta, Saugata; Dimova, Natasha; Myers, Kimberly; Hossain, Abrar; Berube, Michelle; Shuai, Pin; Rhodes, Kimberly; Jewell, Katrina; Lipsi, Mehtaz; Hossain, Saddam; Hosain, Alamgir; Peterson, Jacqeline; Ahmed, Kazi

    2016-04-01

    develop within one season. A 3-D numerical groundwater flow model indicates that river water preferentially moves into the seepage face under the influence of tidal fluctuations. This process, coupled with gaining conditions may be responsible for the formation of the high As zone. Sea level rise and increased groundwater pumping will convert many rivers throughout the world into losing rivers altering this process whereby heavy metals are deposited in river sediments along seepage faces. This may remove an important heavy metal sink and shut off the discharge of other important elements to the oceans.

  11. Hyporheic microbes: the unseen players in stream biogeochemistry

    NASA Astrophysics Data System (ADS)

    Battin, Tom J.; Bengtsson, Mia; Burns, Nancy; Besemer, Katharina; Hall, Ed; Rosentreter, Judith; Wagner, Karoline

    2013-04-01

    The hyporheic zone is the interface between the catchment and its stream. Here streamwater and groundwater interact along numerous flow paths, also conveying solutes and particles. Innumerable microorganisms colonize the large surface offered by the hyporheic sediments and potentially interact with the solute and particle fluxes. Despite our general appreciation of the hyporheic zone for biogeochemical processes in streams and even in rivers, the contributions of its microorganisms to biogeochemistry remain elusive. In this talk, I will present recent research aimed at unravelling the structure and function of hyporheic microorganisms and their involvement in carbon cycling. We experimented with bioreactors simulating the hyporheic zone in headwater streams, and using sequencing and proteomics, we unveiled the massive biodiversity of these microbial communities. Furthermore, using stable isotopes, we explored the contribution of microorganisms to the hyporheic carbon carbon cycle.

  12. USE OF ELECTRICAL RESISTIVITY PROBE WITH MODFLOW FOR SCREENING LEVEL DETERMINATION OF PARAFLUVIAL HYPORHEIC FLOW

    EPA Science Inventory

    The hyporheic zone can provide significant nutrient attenuation in watersheds. Conceptual models describe the behavior of nutrients and biota for the hyporheic ecotone, but site characterization is needed to quantify these effects at the restoration reach scale (hundreds of meter...

  13. USE OF ELECTRICAL RESISTIVITY PROBE WITH MODFLOW FOR SCREENING LEVEL DETERMINATION OF PARAFLUVIAL HYPORHEIC FLOW

    EPA Science Inventory

    The hyporheic zone can provide significant nutrient attenuation in watersheds. Conceptual models describe the behavior of nutrients and biota for the hyporheic ecotone, but site characterization is needed to quantify these effects at the restoration reach scale (hundreds of meter...

  14. Using heat as a tracer to estimate spatially distributed mean residence times in the hyporheic zone of a riffle-pool sequence

    USGS Publications Warehouse

    Naranjo, Ramon C.

    2013-01-01

    Biochemical reactions that occur in the hyporheic zone are highly dependent on the time solutes that are in contact with sediments of the riverbed. In this investigation, we developed a 2-D longitudinal flow and solute-transport model to estimate the spatial distribution of mean residence time in the hyporheic zone. The flow model was calibrated using observations of temperature and pressure, and the mean residence times were simulated using the age-mass approach for steady-state flow conditions. The approach used in this investigation includes the mixing of different ages and flow paths of water through advection and dispersion. Uncertainty of flow and transport parameters was evaluated using standard Monte Carlo and the generalized likelihood uncertainty estimation method. Results of parameter estimation support the presence of a low-permeable zone in the riffle area that induced horizontal flow at a shallow depth within the riffle area. This establishes shallow and localized flow paths and limits deep vertical exchange. For the optimal model, mean residence times were found to be relatively long (9–40.0 days). The uncertainty of hydraulic conductivity resulted in a mean interquartile range (IQR) of 13 days across all piezometers and was reduced by 24% with the inclusion of temperature and pressure observations. To a lesser extent, uncertainty in streambed porosity and dispersivity resulted in a mean IQR of 2.2 and 4.7 days, respectively. Alternative conceptual models demonstrate the importance of accounting for the spatial distribution of hydraulic conductivity in simulating mean residence times in a riffle-pool sequence.

  15. Analysing hyporheic exchange processes during unsteady flow in a small gravel bed river

    NASA Astrophysics Data System (ADS)

    Kurtenbach, Andreas; Schuetz, Tobias; Krein, Andreas; Bierl, Reinhard

    2017-04-01

    Quantifying hyporheic exchange in gravel dominated rivers still remains a challenging task in stream ecology and hydrology, in particular during unsteady flow. We adopted three strategies to decipher exchange processes with the hyporheic zone during unsteady boundary conditions. First, artificial floods were generated in the mid-mountain gravel bed river system of the Olewiger Bach, Germany (24 km2). The advantage of the artificial flood approach lies in the selective control of governing processes by experimental design. Consequently, hydraulic boundary conditions such as maximum discharge, runoff volume and flood duration are steerable during the field experiments and the composition of the discharged water (e.g. low conductivity values) is known. Second, hyporheic exchange was analysed via heat dynamics using air, water and sediment pore water temperatures. Temperature dynamics in the hyporheic zone were monitored at the head, mid and tail of a riffle using specific lances (length: 67 cm, Ø: 3cm) containing temperature sensors in depths of 2, 5, 10, 15, 25, 45 and 65 cm. Short-term temperature variability during the unsteady artificial flood waves were analysed in high resolution of 10-30 seconds. In order to capture long-term seasonal fluctuations and dynamics during natural floods temperature was continuously measured at 5-min resolution. However, heat transfer in the hyporheic zone is affected by both advective and conductive transport. In a third strategy we therefore measure electrical conductivity and selected solutes in pore water during three artificial floods in 2015. Pore water was sampled from different sediment depths (5, 15, 25 and 45 cm) via stainless steel multilevel probes (length: 58 cm, Ø: 4cm). The investigation of temperature and pore water dynamics reveals that precedent hydrological conditions and ground-water levels are significant determinants for hyporheic exchange during unsteady flow. Stable groundwater stratification in spring for

  16. A Survey of Escherichia coli and Salmonella in the Hyporheic Zone of a Subtropical Stream: Their Bacteriological, Physicochemical and Environmental Relationships

    PubMed Central

    Mugnai, Riccardo; Sattamini, Ana; Albuquerque dos Santos, José Augusto; Regua-Mangia, Adriana Hamond

    2015-01-01

    The Hyporheic Zone is among the most important interstitial freshwater habitats, but the relationship between biotic and abiotic factors in this zone remains under-explored. Enterobacteria were expected to be present, but no specific studies had ever confirmed this prediction. The aim of this study was, therefore, to evaluate the total coliforms, Escherichia coli and Salmonella spp. in hyporheic water and to determine the relationship of the physical, chemical and environmental factors at different depths in a rainforest stream. To this end, thirty-six water samples were collected at three depths in sites located in the first, second and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmonella sp. were evaluated in terms of their CFU/ml. In the interstitial samples, coliforms were detected in 100% of the samples. The total coliform counts had higher values at intermediate depths, while E. coli and Salmonella spp. instead had higher values at intermediate and large depths, often reaching or exceeding the values of the surface samples. Our results revealed that Salmonella spp. and the coliforms have different microhabitat preferences. Salmonella spp. and coliform species prefer deposition areas, such as lateral sides of pools, curves and bars, but they have a tendency to distribute into different depths, likely due to temperature differences. Salmonella spp. prefer compact substrata, with fewer fluids passing through and with upwelling areas with lower oxygen inflow. The coliform species showed the opposite preference. Our results suggest that bacterial variation is related to environmental factors and physical-chemical parameters within the HZ and may play a key role in the microbial diversity and distribution in these ecosystems. PMID:26067288

  17. Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

    USGS Publications Warehouse

    Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

    2013-01-01

    ¨hler number seemed to overestimate the actual transition as indicated by multiple secondary electron acceptors, illustrating the gradient nature of anaerobic transition. Temporal flux variability in low-flux morphologies generated a much greater range in hyporheic redox conditions compared to high-flux zones, and chemical responses to changing flux rates were consistent with those predicted from the empirical relationship between redox condition and residence time. The Raz tracer revealed that hyporheic flow paths have strong net aerobic respiration, particularly at higher residence time, but this reactive exchange did not affect the net stream signal at the reach scale.

  18. Multi-scale streambed topographic and discharge effects on hyporheic at the stream network scale in confined streams

    Treesearch

    Alessandra Marzadri; Daniele Tonina; James A. McKean; Matthew G. Tiedemann; Rohan M. Benjankar

    2014-01-01

    The hyporheic zone is the volume of the streambed sediment mostly saturated with stream water. It is the transitional zone between stream and shallow-ground waters and an important ecotone for benthic species, including macro-invertebrates, microorganisms, and some fish species that dwell in the hyporheic zone for parts of their lives. Most hyporheic analyses are...

  19. Impact of a wastewater treatment plant on microbial community composition and function in a hyporheic zone of a eutrophic river

    PubMed Central

    Atashgahi, Siavash; Aydin, Rozelin; Dimitrov, Mauricio R.; Sipkema, Detmer; Hamonts, Kelly; Lahti, Leo; Maphosa, Farai; Kruse, Thomas; Saccenti, Edoardo; Springael, Dirk; Dejonghe, Winnie; Smidt, Hauke

    2015-01-01

    The impact of the installation of a technologically advanced wastewater treatment plant (WWTP) on the benthic microbial community of a vinyl chloride (VC) impacted eutrophic river was examined two years before, and three and four years after installation of the WWTP. Reduced dissolved organic carbon and increased dissolved oxygen concentrations in surface water and reduced total organic carbon and total nitrogen content in the sediment were recorded in the post-WWTP samples. Pyrosequencing of bacterial 16S rRNA gene fragments in sediment cores showed reduced relative abundance of heterotrophs and fermenters such as Chloroflexi and Firmicutes in more oxic and nutrient poor post-WWTP sediments. Similarly, quantitative PCR analysis showed 1–3 orders of magnitude reduction in phylogenetic and functional genes of sulphate reducers, denitrifiers, ammonium oxidizers, methanogens and VC-respiring Dehalococcoides mccartyi. In contrast, members of Proteobacteria adapted to nutrient-poor conditions were enriched in post-WWTP samples. This transition in the trophic state of the hyporheic sediments reduced but did not abolish the VC respiration potential in the post-WWTP sediments as an important hyporheic sediment function. Our results highlight effective nutrient load reduction and parallel microbial ecological state restoration of a human-stressed urban river as a result of installation of a WWTP. PMID:26607034

  20. Impact of a wastewater treatment plant on microbial community composition and function in a hyporheic zone of a eutrophic river

    NASA Astrophysics Data System (ADS)

    Atashgahi, Siavash; Aydin, Rozelin; Dimitrov, Mauricio R.; Sipkema, Detmer; Hamonts, Kelly; Lahti, Leo; Maphosa, Farai; Kruse, Thomas; Saccenti, Edoardo; Springael, Dirk; Dejonghe, Winnie; Smidt, Hauke

    2015-11-01

    The impact of the installation of a technologically advanced wastewater treatment plant (WWTP) on the benthic microbial community of a vinyl chloride (VC) impacted eutrophic river was examined two years before, and three and four years after installation of the WWTP. Reduced dissolved organic carbon and increased dissolved oxygen concentrations in surface water and reduced total organic carbon and total nitrogen content in the sediment were recorded in the post-WWTP samples. Pyrosequencing of bacterial 16S rRNA gene fragments in sediment cores showed reduced relative abundance of heterotrophs and fermenters such as Chloroflexi and Firmicutes in more oxic and nutrient poor post-WWTP sediments. Similarly, quantitative PCR analysis showed 1-3 orders of magnitude reduction in phylogenetic and functional genes of sulphate reducers, denitrifiers, ammonium oxidizers, methanogens and VC-respiring Dehalococcoides mccartyi. In contrast, members of Proteobacteria adapted to nutrient-poor conditions were enriched in post-WWTP samples. This transition in the trophic state of the hyporheic sediments reduced but did not abolish the VC respiration potential in the post-WWTP sediments as an important hyporheic sediment function. Our results highlight effective nutrient load reduction and parallel microbial ecological state restoration of a human-stressed urban river as a result of installation of a WWTP.

  1. Impact of a wastewater treatment plant on microbial community composition and function in a hyporheic zone of a eutrophic river.

    PubMed

    Atashgahi, Siavash; Aydin, Rozelin; Dimitrov, Mauricio R; Sipkema, Detmer; Hamonts, Kelly; Lahti, Leo; Maphosa, Farai; Kruse, Thomas; Saccenti, Edoardo; Springael, Dirk; Dejonghe, Winnie; Smidt, Hauke

    2015-11-26

    The impact of the installation of a technologically advanced wastewater treatment plant (WWTP) on the benthic microbial community of a vinyl chloride (VC) impacted eutrophic river was examined two years before, and three and four years after installation of the WWTP. Reduced dissolved organic carbon and increased dissolved oxygen concentrations in surface water and reduced total organic carbon and total nitrogen content in the sediment were recorded in the post-WWTP samples. Pyrosequencing of bacterial 16S rRNA gene fragments in sediment cores showed reduced relative abundance of heterotrophs and fermenters such as Chloroflexi and Firmicutes in more oxic and nutrient poor post-WWTP sediments. Similarly, quantitative PCR analysis showed 1-3 orders of magnitude reduction in phylogenetic and functional genes of sulphate reducers, denitrifiers, ammonium oxidizers, methanogens and VC-respiring Dehalococcoides mccartyi. In contrast, members of Proteobacteria adapted to nutrient-poor conditions were enriched in post-WWTP samples. This transition in the trophic state of the hyporheic sediments reduced but did not abolish the VC respiration potential in the post-WWTP sediments as an important hyporheic sediment function. Our results highlight effective nutrient load reduction and parallel microbial ecological state restoration of a human-stressed urban river as a result of installation of a WWTP.

  2. Impact of watershed topography on hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Caruso, Alice; Ridolfi, Luca; Boano, Fulvio

    2016-08-01

    Among the interactions between surface water bodies and aquifers, hyporheic exchange has been recognized as a key process for nutrient cycling and contaminant transport. Even though hyporheic exchange is strongly controlled by groundwater discharge, our understanding of the impact of the regional groundwater flow on hyporheic fluxes is still limited because of the complexity arising from the multi-scale nature of these interactions. In this work, we investigate the role of watershed topography on river-aquifer interactions by way of a semi-analytical model, in which the landscape topography is used to approximate the groundwater head distribution. The analysis of a case study shows how the complex topographic structure is the direct cause of a substantial spatial variability of the aquifer-river exchange. Groundwater upwelling along the river corridor is estimated and its influence on the hyporheic zone is discussed. In particular, the fragmentation of the hyporeic corridor induced by groundwater discharge at the basin scale is highlighted.

  3. Identification and Large-Scale Mapping of Riverbed Facies along the Hanford Reach of the Columbia River for Hyporheic Zone Studies

    NASA Astrophysics Data System (ADS)

    Scheibe, T. D.; Hou, Z.; Murray, C. J.; Perkins, W. A.; Arntzen, E.; Richmond, M. C.; Mackley, R.; Johnson, T. C.

    2016-12-01

    The hyporheic zone (HZ) is the sediment layer underlying a river channel within which river water and groundwater may interact, and plays a significant role in controlling energy and nutrient fluxes and biogeochemical reactions in hydrologic systems. The area of this study is the HZ along the Hanford Reach of the Columbia River in southeastern Washington State, where daily and seasonal river stage changes, hydromorphology, and heterogeneous sediment texture drive groundwater-river water exchange and associated biogeochemical processes. The recent alluvial sediments immediately underlying the river are geologically distinct from the surrounding aquifer sediments, and serve as the primary locale of mixing and reaction. In order to effectively characterize the HZ, a novel approach was used to define and map recent alluvial (riverine) facies using river bathymetric attributes (e.g., slope, aspect, and local variability) and simulated hydrodynamic attributes (e.g., shear stress, flow velocity, river depth). The riverine facies were compared with riverbed substrate texture data for confirmation and quantification of textural relationships. Multiple flow regimes representing current (managed) and historical (unmanaged) flow hydrographs were considered to evaluate hydrodynamic controls on the current riverbed grain size distributions. Hydraulic properties were then mapped at reach and local scales by linking textural information to hydraulic property measurements from piezometers. The spatial distribution and thickness of riverine facies is being further constrained by integrating 3D time-lapse electrical resistivity tomography. The mapped distributions of riverine facies and the corresponding flow, transport and biogeochemical properties are supporting the parameterization of multiscale models of hyporheic exchange between groundwater and river water and associated biogeochemical transformations.

  4. Studies on the impacts of hydropeaking on hyporheic invertebrates of an Alpine stream

    NASA Astrophysics Data System (ADS)

    Bruno, Maria Cristina; Silveri, Luana; Maiolini, Bruno

    2010-05-01

    Changes in flow regime associated with sharp discharge fluctuations when water is released from the hydropower plants into the streams (hydropeaking) have cascading effects on the ecological integrity of riverine ecosystems. Hydropeaking modifies the specific composition and longitudinal zonation of invertebrate populations downstream of the power plants through direct impacts on the benthic fauna due to scouring, which removes the animals through drift (i.e. the downstream transport of aquatic organisms under the effect of current velocity) and indirect impacts on the hyporheic zone, i.e. clogging of the interstitial spaces. Clogging occurs due to the reduction of flow and extreme flood events and by deposition of the fine material transported by the release of hypolimnetic water. Clogging reduces the throughflow and the concomitant delivery of resources, as well as the usable pore space for interstitial fauna, impacting the colonization dynamics of interstitial animals. While the impacts of hydropeaking on benthic organisms have been widely investigated so far those on hyporheic fauna have seldom been studied. In a previous research conducted in the same stations discussed here, we investigated the effects of one single hydropeaking event on benthic and hyporheic invertebrates, and assessed that the hyporheic habitat was used as a refuge to avoid drift by part of the benthic organisms, and that hydropeaking reduced hyporheic diversity and abundance in impacted sites, especially affecting the stygobites (specialised subterranean forms, obligatory hypogean), which were significantly more abundant at the non-impacted site. We continued the investigations by studying the spatial (downstream from the disturbance) and temporal effects of repeated hydropeaking events on hyporheic communities. We focussed on the specialization level of the organisms to life in the groundwater, based on the assumption that a reduction of the available habitat for stygobite taxa due to

  5. USE OF ELECTRICAL RESISTIVITY PROBE FOR DETERMINATION OF HYPORHEIC FLOW

    EPA Science Inventory

    The hyporheic zone can play a significant role in nutrient behavior in watersheds. Conceptual models describe the behavior of nutrients and biota for the hyporheic ecotone, but site characterization is needed to quantiiy effects at the restoration reach scale (hundreds of meters)...

  6. USE OF ELECTRICAL RESISTIVITY PROBE FOR DETERMINATION OF HYPORHEIC FLOW

    EPA Science Inventory

    The hyporheic zone can play a significant role in nutrient behavior in watersheds. Conceptual models describe the behavior of nutrients and biota for the hyporheic ecotone, but site characterization is needed to quantiiy effects at the restoration reach scale (hundreds of meters)...

  7. Fe(II)- and Sulfide-Facilitated Reduction of 99Tc(VII)O4- in Microbially Reduced Hyporheic Zone Sediments

    SciTech Connect

    Lee, Ji-Hoon; Zachara, John M.; Fredrickson, Jim K.; Heald, Steve M.; McKinley, James P.; Plymale, Andrew E.; Resch, Charles T.; Moore, Dean A.

    2014-07-01

    Redox-reactive, biogeochemical phases generated by reductive microbial activity in hyporheic zone sediments from a dynamic groundwater-river interaction zone were evaluated for their ability to reduce soluble pertechnetate [99Tc(VII)O4-] to less soluble Tc(IV). The sediments were bioreduced by indigenous microorganisms that were stimulated by organic substrate addition in synthetic groundwater with or without sulfate. In most treatments, 20 µmol L-1 initial aqueous Tc(VII) was reduced to near or below detection (3.82×10-9 mol L-1) over periods of days to months in suspensions of variable solids concentrations. Native sediments containing significant lithogenic Fe(II) in various phases were, in contrast, unreactive with Tc(VII). The reduction rates in the bioreduced sediments increased with increases in sediment mass, in proportion to weak acid-extractable Fe(II) and sediment-associated sulfide (AVS). The rate of Tc(VII) reduction was first order with respect to both aqueous Tc(VII) concentration and sediment mass, but correlations between specific reductant concentrations and reaction rate were not found. X-ray microprobe measurements revealed a strong correlation between Tc hot spots and Fe-containing mineral particles in the sediment. However, only a portion of Fe-containing particles were Tc-hosts. The Tc-hot spots displayed a chemical signature (by EDXRF) similar to pyroxene. The application of autoradiography and electron microprobe allowed further isolation of Tc-containing particles that were invariably found to be ca 100 µm aggregates of primary mineral material embedded within a fine-grained phyllosilicate matrix. EXAFS spectroscopy revealed that the Tc(IV) within these were a combination of a Tc(IV)O2-like phase and Tc(IV)-Fe surface clusters, with a significant fraction of a TcSx-like phase in sediments incubated with SO42-. AVS was implicated as a more selective reductant at low solids concentration even though its concentration was below that

  8. Assessment of hyporheic zone, flood-plain, soil-gas, soil, and surface-water contamination at the Old Incinerator Area, Fort Gordon, Georgia, 2009-2010

    USGS Publications Warehouse

    Guimaraes, Wladmir B.; Falls, W. Fred; Caldwell, Andral W.; Ratliff, W. Hagan; Wellborn, John B.; Landmeyer, James E.

    2011-01-01

    The U.S. Geological Survey, in cooperation with the U.S. Department of the Army Environmental and Natural Resources Management Office of the U.S. Army Signal Center and Fort Gordon, Georgia, assessed the hyporheic zone, flood plain, soil gas, soil, and surface-water for contaminants at the Old Incinerator Area at Fort Gordon, from October 2009 to September 2010. The assessment included the detection of organic contaminants in the hyporheic zone, flood plain, soil gas, and surface water. In addition, the organic contaminant assessment included the analysis of explosives and chemical agents in selected areas. Inorganic contaminants were assessed in soil and surface-water samples. The assessment was conducted to provide environmental contamination data to the U.S. Army at Fort Gordon pursuant to requirements of the Resource Conservation and Recovery Act Part B Hazardous Waste Permit process. Total petroleum hydrocarbons were detected above the method detection level in all 13 samplers deployed in the hyporheic zone and flood plain of an unnamed tributary to Spirit Creek. The combined concentrations of benzene, toluene, ethylbenzene, and total xylene were detected at 3 of the 13 samplers. Other organic compounds detected in one sampler included octane and trichloroethylene. In the passive soil-gas survey, 28 of the 60 samplers detected total petroleum hydrocarbons above the method detection level. Additionally, 11 of the 60 samplers detected the combined masses of benzene, toluene, ethylbenzene, and total xylene above the method detection level. Other compounds detected above the method detection level in the passive soil-gas survey included octane, trimethylbenzene, perchlorethylene, and chloroform. Subsequent to the passive soil-gas survey, six areas determined to have relatively high contaminant mass were selected, and soil-gas samplers were deployed, collected, and analyzed for explosives and chemical agents. No explosives or chemical agents were detected above

  9. Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications

    USGS Publications Warehouse

    Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

    2014-01-01

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed."

  10. Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A.

    2014-12-01

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

  11. Quantifying Hyporheic Exchanges in a Large Scale River Reach Using Coupled 3-D Surface and Subsurface Computational Fluid Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Bao, J.; Zhou, T.; Huang, M.; Hou, Z.; Perkins, W. A.; Harding, S.; Hammond, G. E.; Ren, H.; Thorne, P. D.; Suffield, S. R.; Zachara, J. M.

    2016-12-01

    Hyporheic exchange between river water and groundwater is an important mechanism for biogeochemical processes, such as carbon and nitrogen cycling, and biodegradation of organic contaminants, in the subsurface interaction zone. The relationship between river flow conditions and hyporheic exchanges therefore is of great interests to hydrologists, biogeochemists, and ecologists. However, quantifying relative influences of hydrostatic and hydrodynamic drivers on hyporheic exchanges is very challenging in large rivers due to accessibility and spatial coverage of measurements, and computational tools available for numerical experiments. In this study, we aim to demonstrate that a high resolution computational fluid dynamics (CFD) model that couples surface and subsurface flow and transport can be used to simulate hyporheic exchanges and the residence time of river water in the hypothetic zone. Base on the assumption that the hyporheic exchange does not affect the surface water flow condition due to its small magnitude compared to the velocity of river water, we developed a one way coupled surface and subsurface water flow model in a commercial CFD software STAR-CCM+, that connects the Reynolds-averaged Navier-Stokes (RANS) equation solver with a realizable two-layer turbulence model, a two-layer all y+ wall treatment, and the volume of fluid (VOF) method for tracking the free water-air interface as well as porous media flow in the subsurface domain. The model is applied to a 7-km long section of the Columbia River and validated against measurements from the acoustic Doppler current profiler (ADCP) in the surface water and hyporheic fluxes derived from a set of temperature profilers installed across the riverbed. The validated model is then employed to systematically investigate how hyporheic exchanges influenced by 1) riverbed properties such as the permeability and thickness of the alluvial layer; 2) surface water hydrodynamics due to channel geomorphological settings

  12. Hyporheic flow patterns in relation to large river floodplain attributes

    NASA Astrophysics Data System (ADS)

    Faulkner, Barton R.; Renée Brooks, J.; Forshay, Kenneth J.; Cline, Steven P.

    2012-07-01

    behaviors: lognormal decay with shorter distributions of residence times, and heavy tailing, following power-law behavior. Interestingly, we found the heavy tailing behavior more during the wet season when mean residence times were short. This result implies that even though some rates of hyporheic flow were relatively fast, there were also zones of relatively stagnant water causing this large variation in residence time. Observed slopes for log-log plots of the histograms fell in the range of 2.3-5.6. This behavior appeared to be restricted to regions affected by natural river meandering, where avulsions create isolated islands. In some areas, land managers may consider revetment removal as a means to convert channelized systems to more natural systems with shallower depths in the main channel, meander scrolls, and alcoves that can enhance hyporheic flow. The results of this study provide information on how such decisions may affect the extent of hyporheic flow that may occur as a large river returns to its natural geomorphological dynamics.

  13. Hyporheic Flow and Heat Transport Within a Bed-to-Bank Transect of a Large Regulated River: Colorado River, Austin, TX

    NASA Astrophysics Data System (ADS)

    Gerecht, K.; Cardenas, B.; Guswa, A. J.; Sawyer, A. H.; Swanson, T.; Nowinski, J. D.

    2010-12-01

    The stage and discharge of the Lower Colorado River (LCR) near Austin, Texas is regulated by a series of dams for hydropower generation, flood management, water supply, and recreation. Daily releases from a dam, 23 km upstream of the study site, cause the stage at the site to fluctuate by more than 1.5 m with a mean depth of 1.3 m. These fluctuations cause the LCR at the study site to transition from a regionally gaining river to a river that both gains and loses over each daily cycle. To assess the effects of the flow management on river-groundwater exchange, we collected temperature and head measurements across a hyporheic-to-riparian transect that were highly resolved in both space and time over two campaigns of three days each. These observations show that river-groundwater exchange flux is consistently larger close to the bank and decreases with distance from the bank. Correspondingly, both the depth of the hyporheic zone and the exchange time are greatest near the bank. Adjacent to the bank streambed head response is hysteretic, with hysteresis dissipating with increased distance from the bank, indicating that transient bank storage affects the direction and magnitude of vertical exchange close to the bank. Hyporheic zone temperature is perturbed up to one meter below the bed. When the river stage is high, which coincides with when the river is coldest, downward advection of heat from a previous cycles’ warm-water pulse warms the hyporheic zone. When the river is at its lowest stage but warmest temperature, upwelling groundwater cools the hyporheic zone. These hydraulic and thermal alterations may change the biogeochemical and ecologic dynamics of the river and its hyporheic and riparian zones, including the hyporheic zone’s capacity to act as a biological filter and habitat.

  14. Hydroecological Connections: Hyporheic Zone Weathering of Silicate Minerals Controls Diatom Biodiversity in Microbial Mats in Glacial Meltwater Streams of the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    McKnight, D. M.; Dyson, I.; Esposito, R. M.; Gooseff, M. N.; Lyons, W. B.; Welch, K. A.

    2015-12-01

    The McMurdo Dry Valleys of Antarctica is comprised of alpine and terminal glaciers, large expanses of patterned ground, and ice-covered lakes in the valley floors, which are linked by glacial meltwater streams that flow during the austral summer. As part of the McMurdo Dry Valleys Long-Term Ecological research project, we have observed stream ecosystem response to a sustained 18 year cool period with low flows, which has been recently interrupted by three "flood events" during sunny, warm summers. Many of these streams contain thriving microbial mats comprised of cyanobacteria and endemic diatoms, the most diverse group of eukaryotic organisms in the valleys. Of the 45 diatom taxa, some common taxa are heavily silicified, Hantzschia amphioxys f. muelleri, while others are only lightly silicified. By comparing diatom communities in streams which flow every summer with those in streams that only flow during flood events, we found that hydrologic flow regime acts as a strong environmental filter on diatom community composition. Following the first flood event in 2001/02, mat biomass was two-fold lower due to scouring and recovered over several years, with lesser declines following the subsequent floods. In the longer streams, the diatom community composition remained stable through the flood events, whereas in two of the shorter streams, Green and Bowles Creeks, the diatom community shifted after the first flood event to a greater abundance of lightly silicified taxa. Water quality monitoring and reactive transport modeling have shown that rapid weathering of silicate minerals in the hyporheic zone accounts for the downstream increases in Si concentration which are observed in the longer streams. One mechanism driving this greater abundance of lightly silicified diatoms in shorter streams could be the greater dilution of the Si supply from hyporheic weathering in shorter streams under high flows. Given that the stream diatom community is well preserved in the 40

  15. High Variance within Salmonid Spawning Gravels at Restoration Sites Creates More Suitable Habitat within the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Janes, M. K.; Heffernan, J. E.; Rosenberry, J. W.; Horner, T.

    2012-12-01

    The Lower American River has historically provided natural spawning habitat for approximately one third of Northern California's salmon population. However, since the construction of Folsom and Nimbus Dams, downstream reaches have become sediment starved and periodic high outflow from the dam has caused channel armoring and incision, thereby degrading the natural spawning habitat. Restoration work on spawning sites in the Lower American River has consisted primarily of importing gravel to create riffles during periods of moderate flow. This is an effort to mitigate armoring of the riverbed and to rehabilitate salmonid spawning habitat by providing suitable grain size for all stages of spawning (redd construction, incubation, and emergence). Since restoration activities began, all rehabilitated sites have not been equally used for spawning. This study attempts to examine and compare the physical properties of each site in order to ascertain which characteristics create more suitable rehabilitated habitat. To do this, we compared restored areas to pre-restoration conditions through the assessment of three main aspects of the restored spawning habitat; grain size and its natural mobility, water flow in the surface and subsurface, and intragravel water quality. We found that some augmentation sites are more heterogeneous than others, and this correlates with higher spawning use. Most spawning was at fin height, and salmonids tend to use sites with higher depth variance (surface features) and higher variance in flow directions and velocities. With time, salmonids alter the spawning sites, creating small ridges and valleys perpendicular to flow. This creates more variable subsurface flow and generates hyporheic flow through the new gravel. This may have an effect on spawning as the more seasoned additions have a higher frequency of spawning than the newer augmentations. In order to efficiently rehabilitate a site and expedite the "seasoning process", creating variance

  16. A Hyporheic Mesocosm Experiment: Influence of Quantity and Quality of stream-source DOC on Rates of Hyporheic Metabolism

    NASA Astrophysics Data System (ADS)

    Serchan, S. P.; Wondzell, S. M.; Haggerty, R.; Pennington, R.; Feris, K. P.; Sanfilippo, A. R.; Reeder, W. J.; Tonina, D.

    2016-12-01

    Hyporheic zone biogeochemical processes can influence stream water chemistry. Some estimates show that 50-90% stream water CO2 is produced in the hyporheic zone through heterotrophic metabolism of organic matter, usually supplied from the stream as dissolved organic carbon (DOC). Preliminary results from our well network at the HJ Andrews WS1, indicate that dissolved inorganic carbon (DIC) is 1.5-2 times higher in the hyporheic zone than in stream water. Conversely, DOC (mg/L) is 1.5 times higher in stream water than in the hyporheic zone throughout the year. Overall, the hyporheic zone appears to be a net source of DIC. However, the increase in DIC along hyporheic flow paths is approximately 10-times greater than the loss of DOC, suggesting that metabolism of buried particulate organic carbon (POC) is a major source of organic carbon for microbial metabolism. However, we cannot completely rule out alternative sources of DIC, especially those originating in the overlying riparian soil, because hyporheic processes are difficult to isolate in well networks. To study hyporheic zone biogeochemical processes, particularly the transformation of organic carbon to inorganic carbon species, we designed and built six replicate 2-m long hyporheic mesocosms in which we are conducting DOC amendment experiments. We examine the role of DOC quality and quantity on hyporheic respiration by injecting labile (acetate) and refractory (fulvic acid) organic carbon and comparing rates of O2 consumption, DOC loss, and DIC gains against a control. We expect that stream source DOC is limiting in this small headwater stream, forcing hyporheic metabolism to rely on buried POC. However, the long burial time of POC suggests it is likely of low quality so that supplying labile DOC in stream water should shift hyporheic metabolism away from POC rather than increase the overall rate of metabolism. Future experiments will examine natural sources of DOC (stream periphyton, leaf, and soil humic

  17. Effect of morphology and discharge on hyporheic exchange flows in two small streams in the Cascade Mountains of Oregon, USA.

    Treesearch

    Steven M. Wondzell

    2006-01-01

    Stream-tracer injections were used to examine the effect of channel morphology and changing stream discharge on hyporheic exchange flows. Direct observations were made from well networks to follow tracer movement through the hyporheic zone. The reach-integrated influence of hyporheic exchange was evaluated using the transient storage model (TSM) OTIS-P. Transient...

  18. Functional enzyme-based modeling approach for dynamic simulation of denitrification process in hyporheic zone sediments: Genetically structured microbial community model

    NASA Astrophysics Data System (ADS)

    Song, H. S.; Li, M.; Qian, W.; Song, X.; Chen, X.; Scheibe, T. D.; Fredrickson, J.; Zachara, J. M.; Liu, C.

    2016-12-01

    Modeling environmental microbial communities at individual organism level is currently intractable due to overwhelming structural complexity. Functional guild-based approaches alleviate this problem by lumping microorganisms into fewer groups based on their functional similarities. This reduction may become ineffective, however, when individual species perform multiple functions as environmental conditions vary. In contrast, the functional enzyme-based modeling approach we present here describes microbial community dynamics based on identified functional enzymes (rather than individual species or their groups). Previous studies in the literature along this line used biomass or functional genes as surrogate measures of enzymes due to the lack of analytical methods for quantifying enzymes in environmental samples. Leveraging our recent development of a signature peptide-based technique enabling sensitive quantification of functional enzymes in environmental samples, we developed a genetically structured microbial community model (GSMCM) to incorporate enzyme concentrations and various other omics measurements (if available) as key modeling input. We formulated the GSMCM based on the cybernetic metabolic modeling framework to rationally account for cellular regulation without relying on empirical inhibition kinetics. In the case study of modeling denitrification process in Columbia River hyporheic zone sediments collected from the Hanford Reach, our GSMCM provided a quantitative fit to complex experimental data in denitrification, including the delayed response of enzyme activation to the change in substrate concentration. Our future goal is to extend the modeling scope to the prediction of carbon and nitrogen cycles and contaminant fate. Integration of a simpler version of the GSMCM with PFLOTRAN for multi-scale field simulations is in progress.

  19. Effects of Discharge on Hyporheic Flow in a Pool-Riffle Channel: Implications for Aquatic Habitat

    NASA Astrophysics Data System (ADS)

    Tonina, D.; Buffington, J. M.

    2003-12-01

    The hyporheic zone is a band of saturated sediments that includes the riverbed, banks and the riparian zone. It is a rich habitat for benthic species and fish. The extraordinary variability of flora and fauna that utilize the hyporheic zone make it a crucial component of river ecosystems. We examine how changes in discharge affect downwelling and upwelling of river water through the sediments that comprise the hyporheic zone. These fluxes have multiple effects, bringing high concentrations of dissolved oxygen and other nutrients into the sediments, and at the same time, the sediments and the benthic species living in the streambed filter the water, reducing the biological and chemical loads (BOD, COD, P, C, NOx, etc.). The extent of this active zone is a function of the local topography and consequent spatial variation in the near-bed pressure distribution that drives subsurface flow. Analytical solutions for the piezometric head distribution, H, over two-dimensional dunes are known and can be expressed as a sinusoidal function, H=hm sin(2 π / λ x), where the amplitude, hm, is expressed by hm=0.28 U2 /(2g)(Δ /(0.34d))a . H depends on mean flow velocity, U, water depth, d, and dune wavelength, λ , and amplitude Δ . However, this sinusoidal distribution does not hold for pool-riffle morphologies because flow depths are typically shallow relative to bed form size. To explore this issue we coupled a computational fluid dynamics model (FLUENT) with a simple Darcy subsurface flow model to predict pressure distributions and hyporheic flow for two-dimensional pool-riffle morphologies. Results demonstrate that the intensity, shape, and extent of hyporheic flow paths strongly depend on discharge and its influence on the near-bed pressure distribution. We find that the position of the most intense downwelling moves from the top of the riffle at low discharge to the tail of the pool at high discharge. Our results suggest that aquatic habitat created by topographically

  20. From the Local to the Reach Scale - Quantifying Water Fluxes Across the Hyporheic Zone Using Heat as a Tracer, Hydraulic Conductivity Measurements and Modeling Techniques

    NASA Astrophysics Data System (ADS)

    Schneidewind, U.; Anibas, C.; Ghysels, G.; Huysmans, M.; Azzam, R.

    2016-12-01

    Aquifer-river interactions and their spatio-temporal distribution are important aspects in the study of river systems. Many studies have focused on the hyporheic zone (HZ) with its unique physical and biochemical characteristics. A major factor describing the hydrological connection between aquifers and rivers is the water flux q across the HZ, which depends on transient parameters such as riverbed morphology, sediment and channel characteristics, climate and in-stream plant growth. To quantify q entering or leaving a river at different scales, a variety of methods and models are now available. Here we show results from field campaigns in Belgium (rivers Aa and Slootbeek) conducted to determine q at the local scale with simple methods and to use this information to extrapolate q at the reach scale. Riverbed temperatures were mapped at the Aa river for more than a year using a mobile temperature lance. Temperature profiles from different measurement times where combined to determine q for different time steps using the 1D numerical model STRIVE. Resulting fluxes were interpolated and mapped at the riverbed top and show heterogeneity in space and time. Fluxes are generally higher at the banks of the river than at the center of the respective river cross-sections. To investigate this exchange pattern in detail, for a 20 m-long stretch of the Aa, riverbed hydraulic conductivity K was measured on a fine grid using pneumatic slug and standpipe tests. K-values varied over more than two orders of magnitude and variogram analysis indicated a clear spatial variability. A longitudinal high-K zone was identified where K-values follow a normal distribution while the lower K-values in the rest of the area are log-normal. Spatially distributed K-values were then used with measurements of vertical hydraulic gradients to determine the spatial distribution of q. At a section of the Slootbeek, riverbed temperatures were collected as time-series to study temporal aquifer

  1. Resolving hyporheic and groundwater components of streambed water flux

    USGS Publications Warehouse

    Bhaskar, Aditi S.; Harvey, Judson W.; Henry, Eric J.

    2012-01-01

    Hyporheic and groundwater fluxes typically occur together in permeable sediments beneath flowing stream water. However, streambed water fluxes quantified using the thermal method are usually interpreted as representing either groundwater or hyporheic fluxes. Our purpose was to improve understanding of co-occurring groundwater and hyporheic fluxes using streambed temperature measurements and analysis of one-dimensional heat transport in shallow streambeds. First, we examined how changes in hyporheic and groundwater fluxes affect their relative magnitudes by reevaluating previously published simulations. These indicated that flux magnitudes are largely independent until a threshold is crossed, past which hyporheic fluxes are diminished by much larger (1000-fold) groundwater fluxes. We tested accurate quantification of co-occurring fluxes using one-dimensional approaches that are appropriate for analyzing streambed temperature data collected at field sites. The thermal analytical method, which uses an analytical solution to the one-dimensional heat transport equation, was used to analyze results from a numerical heat transport model, in which hyporheic flow was represented as increased thermal dispersion at shallow depths. We found that co-occurring groundwater and hyporheic fluxes can be quantified in streambeds, although not always accurately. For example, using a temperature time series collected in a sandy streambed, we found that hyporheic and groundwater flow could both be detected when thermal dispersion due to hyporheic flow was significant compared to thermal conduction. We provide guidance for when thermal data can be used to quantify both hyporheic and groundwater fluxes, and we show that neglecting thermal dispersion may affect accuracy and interpretation of estimated streambed water fluxes.

  2. Changes in Hydraulic Gradient, Hyporheic Exchange, and Patterns of Nutrient Concentration between Dry and Wet Season Flows for a Tropical Mountain Stream

    NASA Astrophysics Data System (ADS)

    Fabian, M.; Endreny, T.; Lautz, L.; Siegel, D.

    2009-05-01

    Mountain streams are a common source in Central America for community water supplies (CWS). These streams become dewatered by the CWS during dry season low flows, with potential impacts on hydraulic gradients, hyporheic exchange flow, terrestrial-aquatic linkages, and nutrient dynamics, which may ultimately affect aquatic and riparian micro-ecosystems. We are presenting preliminary results of a study conducted in Buena Vista, a village in Yoro, Honduras where the mountain stream was instrumented and manipulated to measure impacts of a CWS. Piezometric head and stream water levels were taken at 7 cross-sections along 30 m of step-pool stream, and water quality samples were retrieved from 48 pairs of riparian and stream piezometers and monitoring wells. We computed vertical hydraulic gradients, zones of hyporheic upwelling and downwelling, and nutrient patterns, and their change with streamflow. Streamflow ranged from 30 L/s in the wet-season high flow to about 2 L/s in the dry-season low flow, and were dewatered to about 1 L/s. A HEC- RAS water-surface profile model was calibrated to observed stages to establish gradients along the entire reach, and river head was then input as a boundary condition into a MODFLOW groundwater model to examine patterns of hyporheic exchange. Changes in hydraulic gradients and fluxes are compared with baseline conditions during the dry season low flow without dewatering. Noticeable changes in hydraulic gradient occurred between high and low flows, but changes in low flow to dewatered flow were negligible. Lengths and location of hyporheic upwelling and downwelling zones shifted slightly with changes in flow, but again the dewatering had a minor impact. Concentrations of nitrate, sulfate, chloride, fluoride and dissolved oxygen were detected in the hyporheic zone, the stream water, and adjacent ground water. We are exploring mixing models to assess the extent to which hyporheic exchange migrated to and from the creek to adjacent

  3. Hyporheic flow pattern based on the coupling of regional and stream scales: Case of Krycklan Catchment area

    NASA Astrophysics Data System (ADS)

    Mojarrad, Morteza; Wörman, Anders; Riml, Joakim

    2016-04-01

    Water resources intense development within the past century has had an enormous impact on hydrological systems especially on rivers and groundwater resources. A river basin is a flow system involving the interaction between surface water and groundwater. This interaction occurs in terrestrial and coastal zone and even in arid and semi-arid areas, where surface water overlie on a permeable sediment. A key zone for the interaction between surface water and groundwater is the hyporheic zone, which forms by stream water that in- and exfiltrating in the permeable sediments surrounding the river corridor. Groundwater and hyporheic flows arise due to different range of topographical scales and their relative importance is investigated in this study. Krycklan is a well-monitored research catchment in which the data collection for more than 90 years has comprised hydrology, biochemistry, and aquatic ecology. The catchment is located in a boreal area of northern Sweden. The head-water streams begin in mountainous area and fall to the Baltic Sea near the city of Umea. In this paper, COMSOL Multi-physics simulation software has been used to model the subsurface flow of the whole Krycklan catchment in order to reach a comprehensive understanding of large-scale groundwater circulation and its impact of the stream hyporheic flows. The model statement is based on the 3D Laplace equation, which has been applied independently on two ranges of topographical scales to obtain a superimposed solution. Steady state simulation has been done based on the simplified assumption of constant boundary conditions of the groundwater surface and otherwise non-flow boundaries. The hydraulic head of the groundwater surface was taken as the topography, which apply as an approximation in wet climate with shallow soil layers. The results demonstrated how the ratio of the topographical amplitudes on different scales affect the size (depth) and fragmentation of the hyporheic zone. "Fragmentation" was

  4. Impacts of Freshets on Hyporheic Exchange Flow under Gaining and Losing Conditions

    NASA Astrophysics Data System (ADS)

    Wu, L.; Singh, T.; Lewandowski, J.; Nuetzmann, G.; Worman, A. L. E.; Hannah, D. M.; Krause, S.; Gomez-Velez, J. D.

    2016-12-01

    Previous research has identified streambed morphology, sediment properties, channel discharge and groundwater flux as key factors controlling flow and transport characteristics within hyporheic zones (HZs). While the potential dampening of hyporheic exchange flow (HEF) by groundwater up-welling (or down-welling) has been investigated, particularly for ripple bedforms, the impact of time-varying discharge, causing non-stationarity in advective pumping induced HEF, for different types of streambed morphologies remained largely unclear. In this study, we explore the complex interplay among transient driving forces (freshets) and both streambed morphology and groundwater up-welling/down-welling conditions. We simulate HEF driven by a wide range of freshet scenarios in riffle-pool, dune and ripple bedforms under different magnitudes of gaining and losing conditions. To evaluate the effect of the dynamic forcing while modulated by groundwater fluxes, we chose the following metrics: HEF, HZ extent, and the spatial patterns of residence time (RTD) and oxic/anoxic zones. Our study revealed that HZ emerged, vanished, expanded and contracted during freshet events as a function of freshet duration and symmetry, geomorphology and groundwater up-welling/down-welling conditions. Furthermore, zones of substantially increased residence times or even stagnant water were found to vertically move up and down with the expansions and contractions of HZ, bearing potential impacts for biogeochemical transformations. In addition to substantially affecting HZ size, shape and quantity of HEF, the investigated transient freshet scenarios proved to cause significant changes in hyporheic RTD of relevance for further research into biogeochemical cycling within hyporheic zones and stream-aquifer management at larger scales.

  5. Nested patterns in hyporheic meta-communities: the role of body morphology and penetrability of sediment.

    PubMed

    Omesová, Marie; Horsák, Michal; Helesic, Jan

    2008-10-01

    Nestedness has been regarded as a common pattern of species distribution especially in terrestrial systems and vertebrate faunas. However, a significantly lower degree of nestedness has been reported for aquatic invertebrates. We analyzed the vertical distribution patterns of taxa in the upper 70 cm of the hyporheic zone. This biotope is abundantly inhabited by epigean fauna, which is morphologically pre-adapted to life within the limited space of sediment interstices. We tested the hypotheses that in the vertical profile of the hyporheic zone sediment acts as a physical barrier (filter), allowing only the morphologically pre-adapted and adapted (i.e., smaller, narrower, more flexible) taxa to penetrate to deeper layers. We demonstrated that this mechanism can promote a strongly nested and colonization-driven pattern at higher taxa levels. The sediment filter (1) constricted the body width: 0.50 mm appeared to be the upper limit for successful sediment colonization at the study site, and (2) favored elongated taxa against small sized taxa. We tested also the assumption that distribution of fine sediment affects the accessibility of hyporheic zone for fauna ("filter density") and thereby influences nestedness. However, we found that nestedness could be sufficiently explained by the depth itself. Our study offers a possible explanation of depth patterns in hyporeic meta-communities as a result of morphological characteristics promoting nestedness at higher taxa level.

  6. Statistical Modeling to Predict N2O Production Within the Hyporheic Zone by Coupling Denitrifying Microbial Community Abundance to Geochemical and Hydrological Parameters

    NASA Astrophysics Data System (ADS)

    Farrell, T. B.; Quick, A. M.; Reeder, W. J.; Benner, S. G.; Tonina, D.; Feris, K. P.

    2015-12-01

    The hyporheic zone (HZ) of streams may be a significant source of nitrous oxide (N2O). However, the biogeochemical processes controlling N2O emissions remain poorly constrained due to difficulties in obtaining high-resolution chemical, physical, and biological data from streams. Our research elucidates specific controls on N2O production within the HZ by coupling the distribution of denitrifying microbial communities to flow dynamics (i.e. hydraulics and streambed morphology) and biogeochemical processes. We conducted a large-scale flume experiment that allowed us to constrain streambed morphology, flow rate, organic carbon loading, grain size distribution, and exogenous nitrate loading while enabling regular monitoring of dissolved oxygen, pH, alkalinity, nitrogen species, and elemental concentrations in the HZ. We also employed real-time PCR (qPCR) to quantify the distribution of denitrifying functional genes (nirS and nosZ, nitrite reductase and nitrous oxide reductase genes, respectively) in HZ sediment cores as a measure of denitrifying microorganism abundance. A steady increase in N2O was observed after 8 hours of residence time with a peak in concentration (9.5 μg-N/L) recorded at hour 18. Abundance of nosZ increased an order of magnitude between hours 8 and 18 (2.6x106 to 2.1x107 gene copy #/g dry sediment). nirS abundance remained within the same order of magnitude between hours 8 and 18 (1.7x107 to 3.8x107). Linear and nonlinear mixed-effects models were used to investigate N2O production in the HZ as a function of total nitrogen, nirS, nosZ, residence time, and dissolved oxygen. N2O production was localized at redox-controlled hotspots within the subsurface and concentrations were strongly correlated with the availability of nitrogen when an interaction with nosZ abundance was considered. On-going analysis will provide predictions of N2O production and support for conditions under which the HZ could be a significant contributor of N2O emissions. These

  7. Discussion of "Evaluating vertical velocities between the stream and the hyporheic zone from temperature data" by Seydell, I., Wawra, B.E., and Zanke, U.C.E. [Chapter 5].

    Treesearch

    John M. Buffington; Daniele Tonina

    2008-01-01

    Hyporheic exchange is principally driven by spatial variations of near-bed pressure, which can be sensitive to seasonal changes in discharge, flow depth, and watersurface profile (Tonina and Buffington, 2003, 2007). Simulations of hyporheic exchange across two-dimensional pool-riffle topography show that the strength and spatial extent of the hyporheic exchange vary...

  8. Response of crayfish to hyporheic water availability and excess sedimentation

    USGS Publications Warehouse

    Dyer, Joseph J.; Worthington, Thomas A.; Brewer, Shannon K.

    2015-01-01

    Crayfish in many headwater streams regularly cope with seasonal drought. However, it is unclear how landscape changes affect the long-term persistence of crayfish populations. We designed two laboratory experiments to investigate the acute effects of common landscape stressors on crayfish: water withdrawal and sedimentation. The first experiment tested the interaction among water withdrawals (four 24-h water reductions of 0, 15, 30, or 45 cm) and two substrate treatments (pebble and cobble) on the burrowing depth of crayfish. The second experiment evaluated the effects of excess fine sediment (three treatments of 0, 45, and 90% sediment) and substrate type (cobble and pebble) on crayfish burrowing depth. Crayfish were able to burrow deeper into the simulated hyporheic zone in cobble substrate when compared to pebble. Crayfish subjected to greater water withdrawals in the pebble treatment were not able to reach the simulated hyporheic zone. Excess fine sediment reduced the depth that crayfish burrowed, regardless of substrate type. Results from this study suggest excess fine sediment may reduce crayfish persistence, particularly when seeking refuge during prolonged dry conditions.

  9. Seasonal hyporheic dynamics control coupled microbiology and geochemistry in Colorado River sediments

    NASA Astrophysics Data System (ADS)

    Danczak, Robert E.; Sawyer, Audrey H.; Williams, Kenneth H.; Stegen, James C.; Hobson, Chad; Wilkins, Michael J.

    2016-12-01

    Riverbed microbial communities play an oversized role in many watershed ecosystem functions, including the processing of organic carbon, cycling of nitrogen, and alterations to metal mobility. The structure and activity of microbial assemblages depend in part on geochemical conditions set by river-groundwater exchange or hyporheic exchange. To assess how seasonal changes in river-groundwater mixing affect these populations in a snowmelt-dominated fluvial system, vertical sediment and pore water profiles were sampled at three time points at one location in the hyporheic zone of the Colorado River and analyzed by using geochemical measurements, 16S rRNA gene sequencing, and ecological modeling. Oxic river water penetrated deepest into the subsurface during peak river discharge, while under base flow conditions, anoxic groundwater dominated shallower depths. Over a 70 cm thick interval, riverbed sediments were therefore exposed to seasonally fluctuating redox conditions and hosted microbial populations statistically different from those at both shallower and deeper locations. Additionally, microbial populations within this zone were shown to be the most dynamic across sampling time points, underlining the critical role that hyporheic mixing plays in constraining microbial abundances. Given such mixing effects, we anticipate that future changes in river discharge in mountainous, semiarid western U.S. watersheds may affect microbial community structure and function in riverbed environments, with potential implications for biogeochemical processes in riparian regions.

  10. Deriving variable travel times and aerobic respiration in the hyporheic zone using electrical conductivity as natural tracer

    NASA Astrophysics Data System (ADS)

    Vieweg, Michael; Fleckenstein, Jan H.; Schmidt, Christian

    2014-05-01

    level is affecting the travel-time, albeit these effects differ depending on the morphology and strength of the streamflow events. The derived travel times allowed for estimating a transient respiration rate between 3 and 12 mg/l/day. Temperature was found to control over 70% of the variation of the respiration rate. The oxygen concentration in the streambed is more influenced by the variability of the respiration rate than of the travel time.

  11. TRANSIENT STORAGE AND HYPORHEIC FLOW ALONG THE UPPER WILLAMETTE RIVER, OREGON: FIELD MEASUREMENTS AND MODEL ESTIMATES

    EPA Science Inventory

    Transient storage measures the exchange of main channel flow with subsurface hyporheic flow and surface water dead zones. Hyporheic flow, in which river water enters the channel bed and banks to emerge downstream, promotes biochemical processes that are iimportant for water qual...

  12. TRANSIENT STORAGE AND HYPORHEIC FLOW ALONG THE UPPER WILLAMETTE RIVER, OREGON: FIELD MEASUREMENTS AND MODEL ESTIMATES

    EPA Science Inventory

    Transient storage measures the exchange of main channel flow with subsurface hyporheic flow and surface water dead zones. Hyporheic flow, in which river water enters the channel bed and banks to emerge downstream, promotes biochemical processes that are iimportant for water qual...

  13. Characterizing multiple timescales of stream and storage zone interaction that affect solute fate and transport in streams

    USGS Publications Warehouse

    Choi, J.; Harvey, J.W.; Conklin, M.H.

    2000-01-01

    The fate of contaminants in streams and rivers is affected by exchange and biogeochemical transformation in slowly moving or stagnant flow zones that interact with rapid flow in the main channel. In a typical stream, there are multiple types of slowly moving flow zones in which exchange and transformation occur, such as stagnant or recirculating surface water as well as subsurface hyporheic zones. However, most investigators use transport models with just a single storage zone in their modeling studies, which assumes that the effects of multiple storage zones can be lumped together. Our study addressed the following question: Can a single-storage zone model reliably characterize the effects of physical retention and biogeochemical reactions in multiple storage zones? We extended an existing stream transport model with a single storage zone to include a second storage zone. With the extended model we generated 500 data sets representing transport of nonreactive and reactive solutes in stream systems that have two different types of storage zones with variable hydrologic conditions. The one storage zone model was tested by optimizing the lumped storage parameters to achieve a best fit for each of the generated data sets. Multiple storage processes were categorized as possessing I, additive; II, competitive; or III, dominant storage zone characteristics. The classification was based on the goodness of fit of generated data sets, the degree of similarity in mean retention time of the two storage zones, and the relative distributions of exchange flux and storage capacity between the two storage zones. For most cases (> 90%) the one storage zone model described either the effect of the sum of multiple storage processes (category I) or the dominant storage process (category III). Failure of the one storage zone model occurred mainly for category II, that is, when one of the storage zones had a much longer mean retention time (t(s) ratio > 5.0) and when the dominance of

  14. Cumulative Significance of Hyporheic Exchange and Biogeochemical Processing in River Networks

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Gomez-Velez, J. D.

    2014-12-01

    Biogeochemical reactions in rivers that decrease excessive loads of nutrients, metals, organic compounds, etc. are enhanced by hydrologic interactions with microbially and geochemically active sediments of the hyporheic zone. The significance of reactions in individual hyporheic flow paths has been shown to be controlled by the contact time between river water and sediment and the intrinsic reaction rate in the sediment. However, little is known about how the cumulative effects of hyporheic processing in large river basins. We used the river network model NEXSS (Gomez-Velez and Harvey, submitted) to simulate hyporheic exchange through synthetic river networks based on the best available models of network topology, hydraulic geometry and scaling of geomorphic features, grain size, hydraulic conductivity, and intrinsic reaction rates of nutrients and metals in river sediment. The dimensionless reaction significance factor, RSF (Harvey et al., 2013) was used to quantify the cumulative removal fraction of a reactive solute by hyporheic processing. SF scales reaction progress in a single pass through the hyporheic zone with the proportion of stream discharge passing through the hyporheic zone for a specified distance. Reaction progress is optimal where the intrinsic reaction timescale in sediment matches the residence time of hyporheic flow and is less efficient in longer residence time hyporheic flow as a result of the decreasing proportion of river flow that is processed by longer residence time hyporheic flow paths. In contrast, higher fluxes through short residence time hyporheic flow paths may be inefficient because of the repeated surface-subsurface exchanges required to complete the reaction. Using NEXSS we found that reaction efficiency may be high in both small streams and large rivers, although for different reasons. In small streams reaction progress generally is dominated by faster pathways of vertical exchange beneath submerged bedforms. Slower exchange

  15. Hyporheic interactions under a hydropeaking scenario: a multi-scale approach

    NASA Astrophysics Data System (ADS)

    Casas-Mulet, R.; Alfredsen, K.

    2012-04-01

    Sudden flow changes caused by hydropeaking are likely to become more frequent with increasing demand for renewable energy. These sudden fluctuations affect both the surface and subsurface flow regime and change the hydrological interaction patterns occurring in the hyporheic zone. The hyporheos plays an important role in freshwater ecology, especially for early stages of salmon embryo development. Hydrological hyporheic interactions and associated larger scale hydrological processes have hardly been investigated in a hydropeaking scenario. The works presented aim (i) to investigate detailed hydrological processes occurring in the hyporheic zone at the micro-scale during hydropeaking; (ii) to upscale the findings at the meso-scale by repeating the same detailed experiments in differentiated morphologies; and (iii) to use the outputs for establishing more environmentally sound hydropower operations at the catchment scale. An experimental set-up was started in December 2011 in the river Lundesokna (central Norway). A total of 14 pipes were buried at several depths (from 20 to 70 cm) across and along a 5 x 20 m side bar subject to regular drying out and dewatering due to hydropeaking operations. Water pressure sensors were placed in the pipes to monitor the hyporheic water level and flow with 1-2 minutes time resolution. In addition, temperature, conductivity and dissolved oxygen are collected at the same site for an expected period of 3 months, coinciding with early stages of salmonid egg development in this catchment. Results to date show sudden and high groundwater dominated inflow as a consequence of the quick surface water drop during dewatering episodes. But slow reaction spots where surface water remains for longer periods in form of water pockets has been observed. Such processes have the potential to influence the survival of salmon eggs at both smaller and larger scales.

  16. Breakthrough curve moments scaling in hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Bellin, A.; Tonina, D.; Marzadri, A.

    2015-02-01

    The interaction between stream flow and bed forms creates an uneven distribution of near-bed energy heads, which is the driving force of hyporheic exchange. Owing to the large disparity of advection characteristic times in the stream and within the hyporheic zone, solute mass exchange is often modeled by considering the latter as an immobile region. In a recent contribution Gónzalez-Pinzón et al. (2013) showed that existing models employing this hypothesis are structurally inconsistent with the scaling revealed by the analysis of 384 breakthrough curves collected in 44 streams across five continents. Motivated by this result, we analyze the scaling characteristics of a model that we recently developed by combining the analytical solution of the advective flow within the hyporheic zone with a Lagrangian solute transport model. Results show that similarly to the experimental data our model predicts breakthrough curves with a constant skewness, irrespective of the stream size, and that the scaling of the first three moments observed by Gónzalez-Pinzón et al. (2013) is also respected. Moreover, we propose regression curves that relate the first three moments of the residence time distribution with the alternate bar dimensionless depth (YBM*), a quantity that is easily measurable in the field. The connection between BTC moments and YBM* opens new possibilities for modeling transport processes at the catchment scale.

  17. Geoelectrical imaging of hyporheic exchange and mixing of river water and groundwater in a large regulated river.

    PubMed

    Cardenas, M Bayani; Markowski, Michael S

    2011-02-15

    Hyporheic mixing and surface water-groundwater interactions are critical processes in aquatic environments. Yet, there is a lack of methods for assessing the spatial extent and distribution of these mixing zones. This study applied time-lapse electrical resistivity (ER) imaging in a 60-m wide and 0.7-m deep alluvial river whose stage periodically varied by 0.7 m due to dam operations to assess dynamic hyporheic mixing and surface water-groundwater interactions. Sixteen channel-spanning repeat ER tomograms (2D sections) over one flood cycle captured the dynamic ER distribution. We mapped a laterally discontinuous hyporheic zone, which had mainly river water circulating through it, several meters into the bed. Underneath the hyporheic zone was a transitional mixing zone intermittently flushed by mixing river water and deep groundwater. Minimally mixed groundwater dominated the deepest areas. ER imaging allows for unraveling hyporheic and deep mixing zone dynamics in large regulated rivers.

  18. Apples and Oranges of Hyporheic Transport: How Benthic Biolayers are Distinguished by In-Stream and Subsurface Tracer Observations.

    NASA Astrophysics Data System (ADS)

    Knapp, J. L.; Gonzalez-Pinzon, R.; Drummond, J. D.; Larsen, L.; Cirpka, O. A.; Harvey, J. W.

    2016-12-01

    Reactive tracer tests with the compound resazurin are often conducted in streams to determine hyporheic exchange parameters and investigate stream metabolism. Metabolic reactivity is closely linked to the hyporheic zone, and it was the aim of this study to assess the contributions of benthic biolayers, layers of increased reactivity at the top of it, to stream reactivity. We performed a reactive tracer test and simultaneously recorded in-stream tracer breakthrough curves and vertical tracer profiles in the hyporheic zone to quantify the importance of the hyporheic zone and measure gradients of reactivity within it. Afterwards, we fitted advection-dispersion-reaction type models to the obtained in-stream and subsurface data to determine parameters of hyporheic exchange and reactivity. We were able to identify the depth of the benthic biolayer from the decreasing concentrations of the reactive tracer in the vertical subsurface profiles. Its extent varied between the different sampling locations, but comprised approximately the upper third of the hyporheic zone. Regarding hyporheic residence times and reactivity, in-stream and subsurface observations and model outcomes differed in their predictions. In-stream data generally revealed lower hyporheic residence times and lower overall reactivity than the subsurface data, because the different observation approaches see different parts of hyporheic water. The analysis of the in-stream data identifies the part of the hyporheic exchange processes with relevance for whole-stream chemistry because it only sees the hyporheic water returning to the stream. The subsurface data, on the other hand, resolves the vertical gradient of reactivity, thereby identifying the depth and extent of the benthic biolayer, but provide no information on hyporheic water returning to the stream during the tracer test. The two pieces of information provided by in-stream and subsurface data are therefore complementary and cannot be interchanged.

  19. Effects of resource chemistry on the composition and function of stream hyporheic biofilms.

    USGS Publications Warehouse

    Hall, E.K.; Besemer, K.; Kohl, L.; Preiler, C.; Reidel, K.; Schneider, T.; Wanek, W.; Battin, T.J.

    2012-01-01

    Fluvial ecosystems process large quantities of dissolved organic matter as it moves from the headwater streams to the sea. In particular, hyporheic sediments are centers of high biogeochemical reactivity due to their elevated residence time and high microbial biomass and activity. However, the interaction between organic matter and microbial dynamics in the hyporheic zone remains poorly understood. We evaluated how variance in resource chemistry affected the microbial community and its associated activity in experimentally grown hyporheic biofilms. To do this we fed beech leaf leachates that differed in chemical composition to a series of bioreactors filled with sediment from a sub-alpine stream. Differences in resource chemistry resulted in differences in diversity and phylogenetic origin of microbial proteins, enzyme activity, and microbial biomass stoichiometry. Specifically, increased lignin, phenolics, and manganese in a single leachate resulted in increased phenoloxidase and peroxidase activity, elevated microbial biomass carbon:nitrogen ratio, and a greater proportion of proteins of Betaproteobacteria origin. We used this model system to attempt to link microbial form (community composition and metaproteome) with function (enzyme activity) in order to better understand the mechanisms that link resource heterogeneity to ecosystem function in stream ecosystems.

  20. Effects of Resource Chemistry on the Composition and Function of Stream Hyporheic Biofilms

    PubMed Central

    Hall, E. K.; Besemer, K.; Kohl, L.; Preiler, C.; Riedel, K.; Schneider, T.; Wanek, W.; Battin, T. J.

    2012-01-01

    Fluvial ecosystems process large quantities of dissolved organic matter as it moves from the headwater streams to the sea. In particular, hyporheic sediments are centers of high biogeochemical reactivity due to their elevated residence time and high microbial biomass and activity. However, the interaction between organic matter and microbial dynamics in the hyporheic zone remains poorly understood. We evaluated how variance in resource chemistry affected the microbial community and its associated activity in experimentally grown hyporheic biofilms. To do this we fed beech leaf leachates that differed in chemical composition to a series of bioreactors filled with sediment from a sub-alpine stream. Differences in resource chemistry resulted in differences in diversity and phylogenetic origin of microbial proteins, enzyme activity, and microbial biomass stoichiometry. Specifically, increased lignin, phenolics, and manganese in a single leachate resulted in increased phenoloxidase and peroxidase activity, elevated microbial biomass carbon:nitrogen ratio, and a greater proportion of proteins of Betaproteobacteria origin. We used this model system to attempt to link microbial form (community composition and metaproteome) with function (enzyme activity) in order to better understand the mechanisms that link resource heterogeneity to ecosystem function in stream ecosystems. PMID:22347877

  1. Hyporheic invertebrate assemblages at reach scale in a Neotropical stream in Brazil.

    PubMed

    Mugnai, R; Messana, G; Di Lorenzo, T

    2015-11-01

    In the Neotropical Region, information concerning hyporheic communities is virtually non-existent. We carried out a sampling survey in the hyporheic zone of the Tijuca River, in the Tijuca National Park, located in the urban area of the city of Rio de Janeiro. Biological samples from the hyporheic zone were collected in three different stream reaches, in June 2012. The main objectives were: 1) to describe the structure of invertebrate assemblages in the hyporheic zone of a neotropical stream; 2) to apply a reach-scale approach in order to investigate spatial patterns of the hyporheic assemblages in relation to hydrology, depth and microhabitat typology. A total of 1460 individuals were collected and identified in 31 taxa belonging to Nematoda, Annelida, Crustacea, Hydrachnidia and Insecta. The class Insecta dominated the upper layer of the hyporheic zone. Copepods were the most abundant taxon among crustaceans and occurred mostly in the upwelling areas of the reaches. The results of this study represent one of the few contributions so far about hyporheic invertebrate assemblages of the Neotropical Region.

  2. Hyporheic invertebrate assemblages at reach scale in a Neotropical stream in Brazil.

    PubMed

    Mugnai, R; Messana, G; Di Lorenzo, T

    2015-11-10

    AbstractIn the Neotropical Region, information concerning hyporheic communities is virtually non-existent. We carried out a sampling survey in the hyporheic zone of the Tijuca River, in the Tijuca National Park, located in the urban area of the city of Rio de Janeiro. Biological samples from the hyporheic zone were collected in three different stream reaches, in June 2012. The main objectives were: 1) to describe the structure of invertebrate assemblages in the hyporheic zone of a neotropical stream; 2) to apply a reach-scale approach in order to investigate spatial patterns of the hyporheic assemblages in relation to hydrology, depth and microhabitat typology. A total of 1460 individuals were collected and identified in 31 taxa belonging to Nematoda, Annelida, Crustacea, Hydrachnidia and Insecta. The class Insecta dominated the upper layer of the hyporheic zone. Copepods were the most abundant taxon among crustaceans and occurred mostly in the upwelling areas of the reaches. The results of this study represent one of the few contributions so far about hyporheic invertebrate assemblages of the Neotropical Region.

  3. 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...

  4. 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...

  5. Does streambed heterogeneity matter for hyporheic residence time distribution in sand-bedded streams?

    NASA Astrophysics Data System (ADS)

    Tonina, Daniele; de Barros, Felipe P. J.; Marzadri, Alessandra; Bellin, Alberto

    2016-10-01

    Stream water residence times within streambed sediments are key values to quantify hyporheic processes including sediment thermal regime, solute transient storage, dilution rates and biogeochemical transformations, such as those controlling degassing nitrous oxide. Heterogeneity of the streambed sediment hydraulic properties has been shown to be potentially an important factor to characterize hyporheic processes. Here, we quantify the importance of streambed heterogeneity on residence times of dune-like bedform induced hyporheic fluxes at the bedform and reach scales. We show that heterogeneity has a net effect of compression of the hyporheic zone (HZ) toward the streambed, changing HZ volume from the homogenous case and thus inducing remarkable differences in the flow field with respect to the homogeneous case. We unravel the physical conditions for which the commonly used homogenous field assumption is applicable for quantifying hyporheic processes thus explaining why predictive measures based on a characteristic residence time, like the Damköhler number, are robust in heterogeneous sand bedded streams.

  6. The dominant mechanisms of hyporheic exchange

    NASA Astrophysics Data System (ADS)

    McCluskey, Alexander H.; Stewardson, Michael J.; Grant, Stanley B.

    2013-04-01

    The mechanisms driving hyporheic exchange are of significant interest facilitating transfer of nutrients, oxygen and energy essential for benthic ecology. The hyporheic zone is the region directly beneath the sediment-water interface (SWI) marking the transition from stream to porous flow. Hyporheic exchange is controlled by a range of variables of the stream, streambed and the geometry of the SWI. The boundary layer of a stream is characterized by a slip velocity across the SWI, facilitating transition from free fluid to Darcian flow. Mass and momentum transfer across the SWI are driven by either (1) advective pumping from variation in dynamic head at the SWI causing potential flow into and out of the streambed, or; (2) turbulent structures in the boundary layer which penetrate into the streambed. Unlike the advective pumping, turbulent structures penetrate well beyond the characteristic mixing length scale and lead to permanent displacement of fluid. The advective pumping model assumes a potential field directly beneath the SWI, despite the slip layer propagating into the bed. Furthermore, turbulent exchange can lead to a permanent displacement of fluid, while advective pumping is multidirectional and periodic. Models derived from flume experiments have been based on one of these mechanisms and have been presented as two alternative approaches for modelling hyporheic exchange. However, the incongruence of these mechanisms leads us to investigate and model each individually. Our investigation treats coherent turbulent penetration and advective pumping as unique mechanisms which both contribute to rates of hyporheic exchange. Using bedforms as a proxy for advective pumping allowed us to gain insight into the dynamics of exchange mechanisms. Analysis of 93 past flume experiments has shown that bedforms alter the dependence of hyporheic exchange on these exchange mechanisms. Power models developed through a multilinear regression analysis showed that exchange in

  7. Coupled long term simulation of reach scale water and heat fluxes across the river groundwater interface and hyporheic temperature dynamics

    NASA Astrophysics Data System (ADS)

    Munz, Matthias; Oswald, Sascha E.; Schmidt, Christian

    2017-04-01

    Flow pattern and seasonal as well as diurnal temperature variations control ecological and biogeochemical conditions in hyporheic sediments. In particular, hyporheic temperatures have a great impact on many microbial processes. In this study we used 3-D coupled water flow and heat transport simulations applying the HydroGeoSphere code in combination with high frequent observations of hydraulic heads and temperatures for quantifying reach scale water and heat flux across the river groundwater interface and hyporheic temperature dynamics of a lowland gravel-bed river. The magnitude and dynamics of simulated temperatures matched the observed with an average mean absolute error of 0.7 °C and an average Nash Sutcliffe Efficiency of 0.87. Our results highlight that the average temperature in the hyporheic zone follows the temperature in the river which is characterized by distinct seasonal and daily temperature cycles. Individual hyporheic flow path temperature substantially varies around the average hyporheic temperature. Hyporheic flow path temperature was found to strongly depend on the flow path residence time and the temperature gradient between river and groundwater; that is, in winter the average flow path temperature of long flow paths is potentially higher compared to short flow paths. Based on the simulation results we derived a general empirical relationship, estimating the influence of hyporheic flow path residence time on hyporheic flow path temperature. Furthermore we used an empirical temperature relationship between effective temperature and respiration rate to estimate the influence of hyporheic flow path residence time and temperature on hyporheic oxygen consumption. This study highlights the relation between complex hyporheic temperature patterns, hyporheic residence times and their implications on temperature sensitive biogeochemical processes.

  8. Labile dissolved organic carbon supply limits hyporheic denitrification

    Treesearch

    Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

    2012-01-01

    We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

  9. Hyporheic Exchange in Gravel-Bed Rivers with Pool-Riffle Morphology: A 3D Model

    NASA Astrophysics Data System (ADS)

    Tonina, D.; Buffington, J. M.

    2004-12-01

    The hyporheic zone is a saturated band of sediment that surrounds river flow and forms a linkage between the river and the aquifer. It is a rich ecotone where benthic, hyporheic, and groundwater species temporarily or permanently reside. Head gradients along the streambed draw river water into the hyporheic zone and expel pore water into the stream. This process, known as hyporheic exchange, is important for delivering nutrients, oxygen and other solutes to the sediment, and for washing away waste products to support this ecotone. It is an essential component of the carbon and nitrogen cycles, and it controls in-stream contaminant transport. Although hyporheic exchange has been studied in sand-bed rivers with two-dimensional dune morphology, few studies have been conducted for gravel-bed rivers with three-dimensional pool-riffle geometry. The hyporheic zone of gravel-bed rivers is particularly important for salmonids, many of which are currently at risk world wide. Salmon and trout lay their eggs within the hyporheic zone for incubation. After hatching, the alevins live in the gravel before emerging into the stream. The upwelling and downwelling hyporheic fluxes are intense in these streams due to the highly permeable sediment and strong head variations forced by shallow flow over high-amplitude bed forms. Moreover, gravel-bed rivers show a wide range of flow regimes that change seasonally and have strong effects on hyporheic exchange. To study this exchange, we used four sets of pool-riffle geometries in twelve recirculating flume experiments. We kept a constant bed-form wavelength, but changed the bed-form amplitude and imposed three discharges, covering a wide range of hydraulic and geometric characteristics. Hyporheic exchange was predicted from a three-dimensional model based on bedform-induced pumping transport, where the boundary head profile is the pressure head distribution at the sediment interface, measured with an array of mini-piezometers buried within

  10. Investigation of Hyporheic Nitrate Retention Using 15NO3- Additions: Preliminary Results from Mack Creek, Oregon

    NASA Astrophysics Data System (ADS)

    Haggerty, R.; Lanier, J.; Crenshaw, C. L.; Wondzell, S. M.; Baker, M. A.; Gooseff, M. N.

    2005-05-01

    We have initiated an investigation to understand the factors controlling nitrate (NO3-) retention and denitrification in hyporheic zones of small streams and to quantify the fraction of nitrate retention in these streams due to hyporheic exchange. We are testing three hypotheses: (1) hyporheic denitrification in headwater, forested streams will be low because of substrate and rate limitations, yet biotic assimilation will be high, relative to agricultural and urban streams, because of inorganic N-limitation; (2) hyporheic denitrification will be greatest in mid-network locations where surrounding land use is predominantly agricultural, however, total loss of NO3- will be transport-limited and biotic assimilation will be reduced because nitrogen is less limiting; and (3) potential rate of denitrification in the hyporheic zone will be high in the urban stream reaches, but total nitrate retention in the hyporheic zone will be low because both denitrification and biotic assimilation will be severely transport-limited. We will present preliminary data from the LINX II 15NO3- injection in an old-growth reach of 3rd-order Mack Creek, Oregon, where we installed a network of 17 hyporheic wells. Prior to and following the LINX II injection of 15NO3-, the wells were sampled for 14N- and 15N-species including 15N2 and 15N2O. Additionally, in-well salt tracer tests were conducted, and a preliminary groundwater flow model of the site has been developed.

  11. Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

    USGS Publications Warehouse

    Knapp, Julia L.A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

    2017-01-01

    Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

  12. Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

    NASA Astrophysics Data System (ADS)

    Knapp, Julia L. A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

    2017-02-01

    Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

  13. Influence of hyporheic flow and geomorphology on temperature of a large, gravel-bed river, Clackamas River, Oregon, USA

    Treesearch

    Vol. 22 Hydrological Processes

    2008-01-01

    The hyporheic zone influences the thermal regime of rivers, buffering temperature by storing and releasing heat over a range of timesscales. We examined the relationship between hyporheic exchange and temperature along a 24-km reach of the lower Clackamas River, a large gravel-bed river in northwestern Oregon (median discharge = 75·7 m3/s;...

  14. Habitat heterogeneity and associated microbial community structure in a small-scale floodplain hyporheic flow path.

    PubMed

    Lowell, Jennifer L; Gordon, Nathan; Engstrom, Dale; Stanford, Jack A; Holben, William E; Gannon, James E

    2009-10-01

    The Nyack floodplain is located on the Middle Fork of the Flathead River, an unregulated, pristine, fifth-order stream in Montana, USA, bordering Glacier National Park. The hyporheic zone is a nutritionally heterogeneous floodplain component harboring a diverse array of microbial assemblages essential in fluvial biogeochemical cycling, riverine ecosystem productivity, and trophic interactions. Despite these functions, microbial community structure in pristine hyporheic systems is not well characterized. The current study was designed to assess whether physical habitat heterogeneity within the hyporheic zone of the Nyack floodplain was sufficient to drive bacterial beta diversity between three different hyporheic flow path locations. Habitat heterogeneity was assessed by measuring soluble reactive phosphorous, nitrate, dissolved organic carbon, dissolved oxygen, and soluble total nitrogen levels seasonally at surface water infiltration, advection, and exfiltration zones. Significant spatial differences were detected in dissolved oxygen and nitrate levels, and seasonal differences were detected in dissolved oxygen, nitrate, and dissolved organic carbon levels. Denaturing gradient gel electrophoresis (DGGE) and cell counts indicated that bacterial diversity increased with abundance, and DGGE fingerprints covaried with nitrate levels where water infiltrated the hyporheic zone. The ribosomal gene phylogeny revealed that hyporheic habitat heterogeneity was sufficient to drive beta diversity between bacterial assemblages. Phylogenetic (P) tests detected sequence disparity between the flow path locations. Small distinct lineages of Firmicutes, Actinomycetes, Planctomycetes, and Acidobacteria defined the infiltration zone and alpha- and beta-proteobacterial lineages delineated the exfiltration and advection zone communities. These data suggest that spatial habitat heterogeneity drives hyporheic microbial community development and that attempts to understand functional

  15. Effect of experimental wood addition on hyporheic exchange and thermal dynamics in a losing meadow stream

    NASA Astrophysics Data System (ADS)

    Sawyer, Audrey H.; Cardenas, M. Bayani

    2012-10-01

    Stream restoration structures such as large wood can enhance shallow river-groundwater exchange, or hyporheic exchange, and alter temperature dynamics in restored reaches. We added and then removed channel-spanning logs in a second-order mountain meadow stream to test short-term impacts on hyporheic exchange, streambed temperatures, and surface water temperatures. Based on vertical seepage measurements and numerical simulations of hyporheic fluid and heat flow, large wood addition increased hyporheic exchange and altered streambed temperatures. In this losing stream, meter-scale hyporheic exchange cells formed beneath large wood. Upwelling pore water downstream of logs stabilized diel temperature cycles across <8% of the streambed, creating localized but potentially valuable thermal refuge. Exchange rates were <0.1% of channel discharge—too small to impact the range of diel temperature signals in surface water. However, the lag between downstream and upstream diel temperature signals was slightly greater with large wood, which may indicate that surface storage zones rather than hyporheic storage zones increased thermal retardation. Losing conditions limited the spatial extent and rates of hyporheic exchange near large wood. Impacts of large wood reintroduction on hyporheic exchange depend on ambient groundwater discharge or recharge, streambed permeability, channel Froude number, large wood blockage ratio, and large wood spacing. In many streams, large wood reintroduction may increase hyporheic habitat volume and complexity but may not increase exchange rates enough to alter surface water temperature or chemistry. Surface storage zones such as eddies and pools can still influence heat and solute retention in the channel.

  16. Modeling dune-induced hyporheic exchange and nutrient reactions in stream sediments

    NASA Astrophysics Data System (ADS)

    Bardini, L.; Boano, F.; Cardenas, M. B.; Revelli, R.; Ridolfi, L.

    2012-04-01

    The exchange of water across the streambed plays an important role in the ecology of fluvial environments, since it assures the connections of surface and subsurface waters, which have very different peculiarities. Water-borne chemicals are also involved in the process: they enter the sediments with the water and they are transformed into oxidized or reduced substances by biogeochemical reactions, mediated by the hyporheic microbiota. In particular, organic substances can be used as electron donors in a series of redox reactions, with different electron acceptors, e.g., oxygen and nitrate. Nitrification and other secondary reactions also occur as soon as water enters the streambed. These pore-scale transformations concur to affect subsurface solute concentrations and, consequently, the chemistry of upwelling water and the quality of the stream environment. The exchange with the hyporheic zone occurs in response to variations in bed topography, with a very wide range of spatial and temporal scales. For instance, small-scale exchanges are mainly induced by river bed forms, like ripples and dunes, while large-scale exchanges depend on larger geomorphological features. In this work we focus on small-scale exchange induced by the presence of dunes on the streambed, investigating the interplay of hydrological and biogeochemical processes and their effects on solute spatial distribution in the sediments. We numerically simulate the turbulent water flow and the pressure distribution on the streambed and then we evaluate the coupled flow field and biogeochemical reactions in the hyporheic zone in steady-state conditions. Four representative reactive compounds are taken into account: dissolved organic carbon (DOC), oxygen (O2), nitrate (NO3-) and ammonium (NH4+). Sensitivity analyses are also performed to analyze the influence of hydrological and chemical properties of the system on solute reaction rates. The results demonstrate that the stream water quality can strongly

  17. Monitoring of lateral hyporheic exchange fluxes and hyporheic travel times at the newly established Steinlach Test Site, Germany

    NASA Astrophysics Data System (ADS)

    Osenbrück, K.; Lemke, D.; Schwientek, M.; Callisto Alvarez, M. C.; Wöhling, Th.; Cirpka, O. A.

    2012-04-01

    Hyporheic exchange is believed to significantly contribute to the retention and degradation of pollutants during downstream transport in surface waters. A better understanding of the relevant hydraulic drivers of stream water infiltration into the hyporheic zone in conjunction with the associated biogeochemical processes is needed in order to quantify the self-cleaning potential of rivers and to predict water quality changes. Key parameters include the spatial and temporal variation of stream water infiltration (i.e. hyporheic exchange) and the distribution of hyporheic travel times. In this study we present the setup, performance and first results of a multi-disciplinary hyporheic monitoring program at the newly established Steinlach Test Site (STS) near Tübingen in Southern Germany. The STS covers an area of about 0.6 ha and consists of a river loop located within a sub-catchment of the Neckar river. The main objective is the quantification and interrelation of hyporheic processes including hyporheic exchange, travel-time distributions, microbial community dynamics and biochemical pollutant turnover at the groundwater-surface water interface. Here we will focus on the extent and time scale of hyporheic exchange fluxes at the STS derived from time series of temperature (T), specific electrical conductivity (EC), and δ18O of water. The STS is equipped with more than 30 piezometers, most of them containing automatic water level, T and EC probes. Additional water samples for major ions, stable isotopes and other water quality parameters were taken in the course of flood events in summer 2011. The sand and gravel aquifer in the subsurface of the STS is characterised by a complex geometry with heterogeneous hydraulic conductivity. Low residence times in the southern part are confirmed by a small to negligible response in EC and T at the respective piezometers compared to the large variation of EC in the stream water. Using deconvolution techniques, a mean travel time

  18. Hydrological and Climate Controls on Hyporheic Contributions to River Net Ecosystem Productivity

    NASA Astrophysics Data System (ADS)

    Newcomer, M. E.; Hubbard, S. S.; Fleckenstein, J. H.; Maier, U.; Schmidt, C.; Laube, G.; Chen, N.; Ulrich, C.; Dwivedi, D.; Steefel, C. I.; Rubin, Y.

    2016-12-01

    Hyporheic zone contributions to river net ecosystem productivity (NEP) can represent a substantial source or sink for organic and inorganic carbon (C). Hyporheic zone processes are estimated to vary with network location as a function of river-aquifer interactions as well as with climatic factors supporting riverbed gross primary productivity (GPP) and ecosystem respiration. Even though hyporheic zone NEP is hypothesized to be a significant budgetary component to river-aquifer biogeochemical cycling, models of river NEP often parameterize hyporheic zone contributions as a space-time constant input of CO2 to rivers, leading to overestimation of hyporheic zone NEP and underestimation of C storage. This assumption is problematic during the summer growing season, when GPP is largest and C is stored in surface and subsurface biomass. We investigated the dynamic role of hyporheic zone NEP using the MIN3P flow and reactive transport model with surface water GPP and ecosystem respiration simulated as a function of light, depth, temperature, pH, and atmospheric CO2. We simulated hyporheic zone NEP for low-order and high-order streams, which collectively represent a range of characteristic flow paths and subsurface residence times. Downscaled climate predictions of temperature and atmospheric CO2 representing carbon emission futures were used to force the models and to compare future and current hyporheic zone NEP. Our results show that river-aquifer flow conditions determine the relative role of the river as either a store or sink of C through direct contributions of O2 and dissolved organic content from river GPP. Modeled results show that high discharge, high order rivers are net stores of CO2 from the atmosphere; however this is dependent on perturbation events that allow stored C from summer GPP to be released (i.e. rising water tables during winter storms). Lacking a perturbation event, C remains in pore-water storage as dissolved CO2 and biomass. Conversely, low

  19. Assessment of Hyporheic Zone, Flood-Plain, Soil-Gas, Soil, and Surface-Water Contamination at the McCoys Creek Chemical Training Area, Fort Gordon, Georgia, 2009-2010

    USGS Publications Warehouse

    Guimaraes, Wladmir B.; Falls, W. Fred; Caldwell, Andral W.; Ratliff, W. Hagan; Wellborn, John B.; Landmeyer, James E.

    2011-01-01

    The U.S. Geological Survey, in cooperation with the U.S. Department of the Army Environmental and Natural Resources Management Office of the U.S. Army Signal Center and Fort Gordon, Georgia, assessed the hyporheic zone, flood plain, soil gas, soil, and surface water for contaminants at the McCoys Creek Chemical Training Area (MCTA) at Fort Gordon, from October 2009 to September 2010. The assessment included the detection of organic contaminants in the hyporheic zone, flood plain, soil gas, and surface water. In addition, the organic contaminant assessment included the analysis of organic compounds classified as explosives and chemical agents in selected areas. Inorganic contaminants were assessed in soil and surface-water samples. The assessment was conducted to provide environmental contamination data to the U.S. Army at Fort Gordon pursuant to requirements of the Resource Conservation and Recovery Act Part B Hazardous Waste Permit process. Ten passive samplers were deployed in the hyporheic zone and flood plain, and total petroleum hydrocarbons (TPH) and octane were detected above the method detection level in every sampler. Other organic compounds detected above the method detection level in the hyporheic zone and flood-plain samplers were trichloroethylene, and cis- and trans- 1, 2-dichloroethylene. One trip blank detected TPH below the method detection level but above the nondetection level. The concentrations of TPH in the samplers were many times greater than the concentrations detected in the blank; therefore, all other TPH concentrations detected are considered to represent environmental conditions. Seventy-one soil-gas samplers were deployed in a grid pattern across the MCTA. Three trip blanks and three method blanks were used and not deployed, and TPH was detected above the method detection level in two trip blanks and one method blank. Detection of TPH was observed at all 71 samplers, but because TPH was detected in the trip and method blanks, TPH was

  20. Flipping the thin film model: Mass transfer by hyporheic exchange in gaining and losing streams

    NASA Astrophysics Data System (ADS)

    McCluskey, Alexander H.; Grant, Stanley B.; Stewardson, Michael J.

    2016-10-01

    The exchange of mass between a stream and its hyporheic zone, or "hyporheic exchange," is central to many important ecosystem services. In this paper we show that mass transfer across the streambed by linear mechanisms of hyporheic exchange in a gaining or losing stream can be represented by a thin film model in which (a) the mass transfer coefficient is replaced with the average Darcy flux of water downwelling into the sediment and (b) the driving force for mass transfer is "flipped" from normal to the surface (concentration difference across a boundary layer) to parallel to the surface (concentration difference across downwelling and upwelling zones). Our analysis is consistent with previously published analytical, computational, and experimental studies of hyporheic exchange in the presence of stream-groundwater interactions, and links stream network, advection-dispersion, and stochastic descriptions of solute fate and transport in rivers.

  1. Temperature and organic matter controls on hyporheic greenhouse gas production

    NASA Astrophysics Data System (ADS)

    Comer-Warner, S.; Romeijn, P.; Krause, S.; Hannah, D. M.; Gooddy, D.

    2016-12-01

    The region of groundwater and surface water mixing, known as the hyporheic zone, has recently attracted interest as an area of greenhouse gas (GHG) production. Although high concentrations of GHG have been found in these environments, the drivers of hyporheic GHG production remain poorly understood. Here we present the results of a microcosm incubation experiment, designed to determine the effect of multiple environmental parameters on GHG production. Three sediment types, representing a gradient of organic matter contents, from two contrasting UK lowland rivers (sandstone and chalk), were incubated for 29 hours. Experiments were performed at five temperature treatments between 5 and 25°C, and the microbial metabolism of each microcosm was determined using the smart tracer Resazurin. Headspace concentrations of carbon dioxide, methane and nitrous oxide were measured to determine the effect of these environmental parameters on GHG production, and establish their roles as drivers of GHG production in the hyporheic zone. Our results indicate strong temperature controls of GHG production, overlapping with the observed impacts of varying organic matter content of different sediments. Experimental findings indicate that increased hyporheic temperatures during increasing baseflow and drought conditions may significantly enhance sediment respiration, and thus, GHG emissions from the streambed interface. This research advances understanding of drivers of whole stream carbon and nitrogen budgets, as well as the role of groundwater-surface water interfaces in GHG emissions, and allows the interaction of these controls to be assessed.

  2. Monitoring hyporheic exchanges during a dam controlled experiment

    NASA Astrophysics Data System (ADS)

    Houzé, Clémence; Varnède, Lucie; Durand, Véronique; Pessel, Marc

    2016-04-01

    Precise understanding of the hyporheic exchanges response to stream flow fluctuations remains a great challenge for many environmental and hydrological problems. Multiplication of natural stream restoration programs and anthropic structures removal highlight that a better understanding of the hydrodynamic and ecological functioning of hyporheic exchanges is critical . The objective of this field experiment was to monitor the dynamic exchanges within the hyporheic zone due to an artificial stream head variation. Various types of measurements were performed, using natural tracers and electrical resistivity tomography (ERT). The dam downstream the studied river reach was successively lowered during two days, and raised during three days, implying river heads variations of about 15cm. The studied area was equipped with CTD probes (measuring the head and the conductivity) within the river, 2 multi-depths water sampling tubes inserted up to one meter depth within the riverbed deposits and 3 ERT profiles with various electrode spacing (20 cm, 25 cm, 50 cm). During the 5 days experiment, water sampling and ERT profiles were done regularly. Estimations of the sediments hydraulic conductivity were obtained by several slug tests in plastic tubes at different depths within the streambed. First results showed that stream fluctuation leads to a rapid hyporheic response according to chloride variations between stream and riverbed sediments. Similar results between geochemical and geophysical tools were found. A decrease in stream head leads to reduce the depth of the mixing zone, as the river gaining conditions intensify. On the contrary, we observed that an increased river head tends to deepen the hyporheic exchange zone.

  3. The influence of stream thermal regimes and preferential flow paths on hyporheic exchange in a glacial meltwater stream

    USGS Publications Warehouse

    Cozzetto, Karen D.; Bencala, Kenneth E.; Gooseff, Michael N.; McKnight, Diane M.

    2013-01-01

    Given projected increases in stream temperatures attributable to global change, improved understanding of relationships between stream temperatures and hyporheic exchange would be useful. We conducted two conservative tracer injection experiments in a glacial meltwater stream, to evaluate the effects of hyporheic thermal gradients on exchange processes, including preferential flow paths (PFPs). The experiments were conducted on the same day, the first (a stream injection) during a cool, morning period and the second (dual stream and hyporheic injections) during a warm, afternoon period. In the morning, the hyporheic zone was thermally uniform at 4°C, whereas by the afternoon the upper 10 cm had warmed to 6–12°C and exhibited greater temperature heterogeneity. Solute transport modeling showed that hyporheic cross-sectional areas (As) at two downstream sites were two and seven times lower during the warm experiment. Exchange metrics indicated that the hyporheic zone had less influence on downstream solute transport during the warm, afternoon experiment. Calculated hyporheic depths were less than 5 cm, contrasting with tracer detection at 10 and 25 cm depths. The hyporheic tracer arrival at one downstream site was rapid, comparable to the in-stream tracer arrival, providing evidence for PFPs. We thus propose a conceptual view of the hyporheic zone in this reach as being dominated by discrete PFPs weaving through hydraulically isolated areas. One explanation for the simultaneous increase in temperature heterogeneity and As decrease in a warmer hyporheic zone may be a flow path preferentiality feedback mechanism resulting from a combination of temperature-related viscosity decreases and streambed heterogeneity.

  4. Physicochemical Characteristics of the Hyporheic Zone Affect Redd Site Selection of Chum and Fall Chinook Salmon, Columbia River.

    SciTech Connect

    Geist, David R.

    2001-10-01

    Chum salmon (Oncorhynchus keta) may historically have been the most abundant species of Columbia River salmon, contributing as much as 50% of the total biomass of all salmon in the Pacific Ocean prior to the 1940's (Neave 1961). By the 1950's, however, run sizes to the Columbia River dropped dramatically and in 1999 the National Marine Fisheries Service (NMFS) listed Columbia River chum salmon as threatened under the Endangered Species Act (ESA; NMFS 1999). Habitat degradation, water diversions, harvest, and artificial propagation are the major human-induced factors that have contributed to the species decline (NMFS 1998). Columbia River chum salmon spawn exclusively in the lower river below Bonneville Dam, including an area near Ives Island. The Ives Island chum salmon are part of the Columbia River evolutionary significant unit (ESU) for this species, and are included in the ESA listing. In addition to chum salmon, fall chinook salmon (O. tshawytscha) also spawn at Ives Island. Spawning surveys conducted at Ives Island over the last several years show that chum and fall chinook salmon spawned in clusters in different locations (US Fish and Wildlife Service and Washington Department of Fish and Wildlife, unpublished data). The presence of redd clusters suggested that fish were selecting specific habitat features within the study area (Geist and Dauble 1998). Understanding the specific features of these spawning areas is needed to quantify the amount of habitat available to each species so that minimum flows can be set to protect fish and maintain high quality habitat.

  5. Relating stationary and non-stationary hyporheic travel times with hyporheic chemistry at the Steinlach Test Site, Germany

    NASA Astrophysics Data System (ADS)

    Osenbrück, Karsten; Rohrbach, Nina; Lemke, Dennis; Liao, Zijie; Cirpka, Olaf A.

    2013-04-01

    Stream-groundwater interaction is believed to significantly contribute to the retention and degradation of pollutants by means of associated biogeochemical processes in the hyporheic zone. The distribution and temporal variability of travel times of water within the hyporheic zone and their relation to hyporheic reactivity are amongst the key parameters for assessing the self-cleaning potential of rivers and hence water quality changes at catchment scale. In this study we used time series of specific electrical conductivity (EC) of water to delineate the flow paths and travel times of water undergoing exchange between a stream and the adjacent riparian aquifer. The main objective was to interrelate hyporheic travel times with transformations of oxygen and nitrate monitored within the hyporheic zone. The study is part of a multi-disciplinary monitoring program at the Steinlach Test Site near Tübingen in Southern Germany. The test site covers an area of about 0.6 ha and consists of a river bend underlain by a sandy gravel aquifer. The site is equipped with more than 30 piezometers, most of them containing automatic water level, temperature, and EC probes and in some cases also oxygen probes. Additional field measurements of dissolved oxygen and pH as well as water samples for the analysis of major ions and DOC were taken from March to December 2012. Travel time distributions and mean travel times were derived using parametric as well as non-parametric (shape-free) deconvolution approaches. In addition to these stationary approaches, we also applied a windowed cross-correlation approach to assess short-term changes in travel time governed by variations in stream discharge. Mean travel times of 0.5 to 8 days were estimated from EC and δ18O data using a dispersion model for groundwater taken from selected piezometers and at the outlet spring. Application of the non-stationary modelling approach revealed a doubling of travel times between high and low flow conditions

  6. Quantifying hyporheic exchange dynamics in a highly regulated large river reach

    NASA Astrophysics Data System (ADS)

    Zhou, T.; Bao, J.; Huang, M.; Hou, Z.; Arntzen, E.; Mackley, R.; Harding, S.; Crump, A.; Xu, Y.; Song, X.; Chen, X.; Stegen, J.; Hammond, G. E.; Thorne, P. D.; Zachara, J. M.

    2016-12-01

    Hyporheic exchange is an important mechanism taking place in riverbanks and riverbed sediments, where the river water and shallow groundwater mix and interact with each other. The direction and magnitude of hyporheic flux that penetrates the river bed and residence time of river water in the hyporheic zone are critical for biogeochemical processes such as carbon and nitrogen cycling, and biodegradation of organic contaminants. Hyporheic flux can be quantified using many direct and indirect measurements as well as analytical and numerical modeling tools. However, in a relatively large river, these methods can be limited by the accessibility, spatial constraints, complexity of geomorphologic features and subsurface properties, and computational power. In rivers regulated by hydroelectric dams, quantifying hyporheic fluxes becomes more challenging due to frequent hydropeaking events created by dam operations. In this study, we developed and validated methods that combined field measurements and numerical modeling for estimating hyporheic fluxes across the river bed in a 7-km long reach of the highly regulated Columbia River. The reach has a minimum width of about 800 meters and variations in river stage within a day could be up to two meters due to the upstream dam operations. In shallow water along the shoreline, vertical thermal profiles measured by self-recording thermistors were combined with time series of hydraulic gradient derived from river stage and water level at in-land wells to estimate the hyporheic flux rate. For the deep section, a high resolution computational fluid dynamics (CFD) modeling framework was developed to characterize the spatial distribution of flux rates at the river bed and the residence time of hyporheic flow at different river flow conditions. Our modeling results show that the rates of hyporheic exchange and residence time are controlled by (1) hydrostatic pressure induced by river stage fluctuations, and (2) hydrodynamic drivers

  7. Redox Zonation and Oscillation in the Hyporheic Zone of the Ganges-Brahmaputra-Meghna Delta: Implications for the Fate of Groundwater Arsenic during Discharge

    PubMed Central

    Jung, Hun Bok; Zheng, Yan; Rahman, Mohammad W.; Rahman, Mohammad M.; Ahmed, Kazi M.

    2015-01-01

    Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.-Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0-2 m depth) to reducing (2-5 m depth) then suboxic conditions (5-7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n=7) and sediment (n=11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ~700 mg kg−1) is associated with the suboxic zones mostly between 0-2 m depth and less frequently between 5-7 m depth. The As enriched zones consist of several 5 to 10 cm-thick dispersed layers and span a length of ~5-15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6±11.7 mg L−1) and As (118±91 μg L−1, mostly as arsenite) between 2-5 m depth, but lower concentrations between 0-2 m depth (0.13±0.19 mg L−1 Fe, 1±1 μg L−1 As) and between 5-6 m depth (1.14±0.45 mg L−1 Fe, 28±17 μg L−1 As). Because it would take more than a few hundred years of steady groundwater discharge (~10 m yr−1) to accumulate hundreds of mg kg−1 of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer. PMID:26855475

  8. Redox Zonation and Oscillation in the Hyporheic Zone of the Ganges-Brahmaputra-Meghna Delta: Implications for the Fate of Groundwater Arsenic during Discharge.

    PubMed

    Jung, Hun Bok; Zheng, Yan; Rahman, Mohammad W; Rahman, Mohammad M; Ahmed, Kazi M

    2015-12-01

    Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.-Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0-2 m depth) to reducing (2-5 m depth) then suboxic conditions (5-7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n=7) and sediment (n=11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ~700 mg kg(-1)) is associated with the suboxic zones mostly between 0-2 m depth and less frequently between 5-7 m depth. The As enriched zones consist of several 5 to 10 cm-thick dispersed layers and span a length of ~5-15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6±11.7 mg L(-1)) and As (118±91 μg L(-1), mostly as arsenite) between 2-5 m depth, but lower concentrations between 0-2 m depth (0.13±0.19 mg L(-1) Fe, 1±1 μg L(-1) As) and between 5-6 m depth (1.14±0.45 mg L(-1) Fe, 28±17 μg L(-1) As). Because it would take more than a few hundred years of steady groundwater discharge (~10 m yr(-1)) to accumulate hundreds of mg kg(-1) of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer.

  9. A Comparison of Hyporheic Transport at a Cross-Vane Structure and Natural Riffle.

    PubMed

    Smidt, Samuel J; Cullin, Joseph A; Ward, Adam S; Robinson, Jesse; Zimmer, Margaret A; Lautz, Laura K; Endreny, Theodore A

    2015-01-01

    While restoring hyporheic flowpaths has been cited as a benefit to stream restoration structures, little documentation exists confirming that constructed restoration structures induce comparable hyporheic exchange to natural stream features. This study compares a stream restoration structure (cross-vane) to a natural feature (riffle) concurrently in the same stream reach using time-lapsed electrical resistivity (ER) tomography. Using this hydrogeophysical approach, we were able to quantify hyporheic extent and transport beneath the cross-vane structure and the riffle. We interpret from the geophysical data that the cross-vane and the natural riffle induced spatially and temporally unique hyporheic extent and transport, and the cross-vane created both spatially larger and temporally longer hyporheic flowpaths than the natural riffle. Tracer from the 4.67-h injection was detected along flowpaths for 4.6 h at the cross-vane and 4.2 h at the riffle. The spatial extent of the hyporheic zone at the cross-vane was 12% larger than that at the riffle. We compare ER results of this study to vertical fluxes calculated from temperature profiles and conclude significant differences in the interpretation of hyporheic transport from these different field techniques. Results of this study demonstrate a high degree of heterogeneity in transport metrics at both the cross-vane and the riffle and differences between the hyporheic flowpath networks at the two different features. Our results suggest that restoration structures may be capable of creating sufficient exchange flux and timescales of transport to achieve the same ecological functions as natural features, but engineering of the physical and biogeochemical environment may be necessary to realize these benefits.

  10. Hyporheic nutrient transformation - A panacea for river restoration that solves the "Nitrate Time Bomb" ?

    NASA Astrophysics Data System (ADS)

    Krause, S.; Heathwaite, L.; Binley, A.; Kaeser, D.

    2009-04-01

    The river - aquifer interface, also called the ‘hyporheic zone' or ‘interstitial' characterises the area of intensive mixing between groundwater and surface water within the streambed of a river. Its physical conditions, as hydraulic conductivity and residence time, control fluxes and exchange rates between groundwater and surface water. Because of its often steep and dynamic redox gradients, the hyporheic zone can represent an area of high chemical activity. Previous studies described how the transport and redox processes in the hyporheic zone can cause effective nutrient attenuation, e.g. by denitrification. Hence, river regulators and river basin management plans hope for the hyporheic zone to delimit the negative impact, polluted groundwater has for the stream ecological health. The desperation behind such expectations becomes apparent in light of increasing nitrate concentrations in many groundwater aquifers and their long residence times - the so-called "Nitrate Time Bomb". In this study we investigate spatial and temporal patterns of physical streambed characteristics and redox chemical conditions and its controls on nitrogen transport and transformation in the streambed of several English rivers. For the streambed sediments of a 50 - 250 m stream reaches, pore water nitrate and ammonia concentrations were monitored together with common anions, redox conditions, dissolved oxygen levels and rates of groundwater up-welling and surface water mixing in a dense system of nested piezometer for a two year period. The results of this study indicate that hyporheic nutrient transformation can well exceed the usually assumed streambed depths of a few cm and may occur in depths of up to 1 m. Our investigations furthermore detected, that within the research area the hyporheic passage has a spatially very variable impact on the exchange fluxes and nitrogen concentrations and transformation rates in the streambed. Nitrate attenuation due to denitrification was found in

  11. How important is the consideration of hyporheic nutrient attenuation for integrated water resource management?

    NASA Astrophysics Data System (ADS)

    Krause, Stefan; Naden, Emma; Tecklenburg, Christina; Munz, Mathias; Kaeser, Daniel; Binley, Andrew; Heathwaite, Louise

    2010-05-01

    The ‘hyporheic zone' or ‘interstitial' characterises an area of intensive groundwater and surface water mixing within streambed sediments. Its physical conditions, as for instance the hydraulic conductivity and residence time, control fluxes and exchange rates between groundwater and surface water. Because of its often steep and dynamic redox gradients, the hyporheic zone can represent an area of high chemical activity. Previous studies described how the transport and redox processes in the hyporheic zone can cause effective nutrient attenuation, e.g. by denitrification. Hence, regulatory bodies and catchment management plans hope for the hyporheic zone to delimit the negative impact, polluted groundwater can have for the stream ecological health. In this study we investigate spatial and temporal patterns of physical streambed characteristics and redox chemical conditions and its controls on the reactive transport and transformation of nitrogen in the streambeds of two UK upland and lowland rivers. For the streambed sediments of several stream reaches, pore water nitrate/nitrite and ammonia concentrations were monitored together with common anions, redox conditions, dissolved oxygen and organic carbon and rates of groundwater up-welling and surface water mixing in a dense system of nested piezometer over several baseflow periods. Spatial patterns of aquifer - river exchange were furthermore investigated by active and passive heat tracer experiments using fibre optic distributed temperature sensor networks at reach and heat pulse injection experiments at local scales. The results of this study indicate that hyporheic nutrient transformation can well exceed the usually assumed streambed depths of a few cm and may occur in depths of > 1m. Our investigations furthermore detected, that within the research area the hyporheic passage has a spatially very variable impact on the exchange fluxes and nitrogen concentrations and transformation rates in the streambed

  12. Drivers and Spatio-Temporal Extent of Hyporheic Patch Variation: Implications for Sampling

    PubMed Central

    Braun, Alexander; Auerswald, Karl; Geist, Juergen

    2012-01-01

    The hyporheic zone in stream ecosystems is a heterogeneous key habitat for species across many taxa. Consequently, it attracts high attention among freshwater scientists, but generally applicable guidelines on sampling strategies are lacking. Thus, the objective of this study was to develop and validate such sampling guidelines. Applying geostatistical analysis, we quantified the spatio-temporal variability of parameters, which characterize the physico-chemical substratum conditions in the hyporheic zone. We investigated eight stream reaches in six small streams that are typical for the majority of temperate areas. Data was collected on two occasions in six stream reaches (development data), and once in two additional reaches, after one year (validation data). In this study, the term spatial variability refers to patch contrast (patch to patch variance) and patch size (spatial extent of a patch). Patch contrast of hyporheic parameters (specific conductance, pH and dissolved oxygen) increased with macrophyte cover (r2 = 0.95, p<0.001), while patch size of hyporheic parameters decreased from 6 to 2 m with increasing sinuosity of the stream course (r2 = 0.91, p<0.001), irrespective of the time of year. Since the spatial variability of hyporheic parameters varied between stream reaches, our results suggest that sampling design should be adapted to suit specific stream reaches. The distance between sampling sites should be inversely related to the sinuosity, while the number of samples should be related to macrophyte cover. PMID:22860053

  13. a Process Based Model to Predict Hyporheic Flow Induced by Alternate Bars

    NASA Astrophysics Data System (ADS)

    Marzadri, A.; Tonina, D.; Bellin, A.; Vignoli, G.; Tubino, M.

    2010-12-01

    The hydrological connection between stream and hyporheic zone, which is the saturated volume of sediment surrounding a stream, may influence the self-purification processes of river ecosystems. This is because stream and pore waters continually exchange in the hyporheic zone due to several mechanisms, which depend on the variations of near-bed pressure, sediment hydraulic conductivity, alluvium volume, and turbulence. We investigate the effects of alternate-bar morphology on the hyporheic exchange in gravel bed rivers by identifying the relations between the hyporheic residence time moments (mean and variance) and the parameters controlling the bed form morphology (width to depth ratio, bottom shear stress and relative submergence). We assume constant stream discharge in equilibrium with the bed forms, which are considered fixed because their formation time scale is much longer than that of the subsurface flow. We solve the three-dimensional flow equation analytically in a domain, whose dimensions are the channel width, bed form wavelength and alluvium depth. The velocity field is obtained via the Darcy’s law, once the head distribution is known within the hyporheic zone. Finally, solute transport is modeled numerically by the particle tracking technique. Model results show that the mean value and variance of the hyporheic residence time normalized by suitable timescales depend only on the amplitude of the alternate-bar morphology at equilibrium. This result is found to be applicable also to discharges that are lower (70% in our simulations) than the equilibrium and that submerge the bed forms entirely. Moreover, our analysis shows that 95% of the hyporheic flow is confined in a near-bed layer, whose depth is about the width of the channel and shallows from low to steep gradient streams. As a result the hyporheic mean residence time reaches an asymptotic value if the alluvial depth is deeper than the channel width. Our results also show that as the stream slope

  14. Leaf litter recycling in benthic and hyporheic layers in agricultural streams with different types of land use.

    PubMed

    Piscart, Christophe; Navel, Simon; Maazouzi, Chafik; Montuelle, Bernard; Cornut, Julien; Mermillod-Blondin, Florian; des Chatelliers, Michel Creuze; Simon, Laurent; Marmonier, Pierre

    2011-09-15

    Changes in land use and intensification of agricultural pressure have greatly accelerated the alteration of the landscape in most developed countries. These changes may greatly disturb the adjacent ecosystems, particularly streams, where the effects of pollution are amplified. In this study, we used the leaf litter breakdown rate to assess the functional integrity of stream ecosystems and river sediments along a gradient of either traditional extensive farming or a gradient of vineyard area. In the benthic layer, the total litter breakdown process integrates the temporal variability of the anthropogenic disturbances and is strongly influenced by land use changes in the catchment even though a low concentration of toxics was measured during the study period. This study also confirmed the essential role played by amphipods in the litter breakdown process. In contrast, microbial processes may have integrated the variations in available nutrients and dissolved oxygen concentrations, but failed to respond to the disturbances induced by vineyard production (the increase in pesticides and metal concentrations) during the study period. The response of microbes may not be sensitive enough for assessing the global effect of seasonal agricultural practices. Finally, the leaf litter breakdown measured in the hyporheic zone seemed mainly driven by microbial activities and was hence more affected by vertical exchanges with surface water than by land use practices. However, the breakdown rate of leaf litter in the hyporheic zone may constitute a relevant way to evaluate the impact on river functioning of any human activities that induce massive soil erosion and sediment clogging.

  15. One-dimensional advection diffusion modeling of upwelled hyporheic stream temperature along Deer Creek, Vina, California

    NASA Astrophysics Data System (ADS)

    Butler, N. L.; Hunt, J. R.; Tompkins, M. R.

    2011-12-01

    flow and hyporheic exchange together. Temperature data from only the hyporheic downwelling and upwelling locations along with the model developed successfully provides a new method to estimate the subsurface water velocity and hydrodynamic dispersivity to evaluate the spatial and temporal variability in the hyporheic zone and its interaction with surface water flow.

  16. 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

  17. Hydrologic and Biogeochemical Controls on Hyporheic N2O Emissions

    NASA Astrophysics Data System (ADS)

    Quick, A. M.; Reeder, W. J.; Farrell, T. B.; Tonina, D.; Feris, K. P.; Benner, S. G.

    2016-12-01

    The hyporheic zones (HZ) of streams and rivers may be a significant source of nitrous oxide (N2O) emissions, but the hydrological and biogeochemical controls on if and how much N2O is released from the HZ are not well constrained. We employed a multidisciplinary approach to examine HZ N2O emissions that included a column experiment and two large-scale flume experiments in which we controlled initial particulate organic matter, exogenous nitrate loading, flow rates, and streambed geomorphology at the scales of a natural stream. In both 1D (column) and 2D (flume) experiments, hyporheic flow paths and residence times were modeled and measured with tracers. We measured in-situ pore water concentrations of dissolved oxygen and inorganic nitrogen species, including dissolved N2O. We observed both N2O production and consumption along HZ flow paths. Our results indicate that N2O generation and consumption are dictated by hyporheic residence times and biological nitrogen reduction rates. For N2O to be released from the HZ, residence times must be sufficiently long (or reaction rates must be sufficiently fast) to promote reduction of nitrate to N2O. However, if residence times are too long (or reaction rates are too fast) N2O will be converted to N2. As a result, only a small fraction of HZ flow paths will produce N2O at a given time. For example, although we observed concentrations up to 122 μg L-1 N-N2O in the HZ, most of this N2O was reduced to N2 before leaving the HZ and entering the surface stream water. We also observed that higher N2O concentrations in the HZ correspond to high surface water nitrate and low carbon reactivity in the sediments. The conceptual model supported by these flume and column experiments suggests that both reduction of nitrate loading and increased hyporheic residence times may moderate the potential for N2O emissions from stream hyporheic zones.

  18. Modeling hyporheic exchange and in-stream transport with time-varying transit time distributions

    NASA Astrophysics Data System (ADS)

    Ball, A.; Harman, C. J.; Ward, A. S.

    2014-12-01

    Transit time distributions (TTD) are used to understand in-stream transport and exchange with the hyporheic zone by quantifying the probability of water (and of dissolved material) taking time T to traverse the stream reach control volume. However, many studies using this method assume a TTD that is time-invariant, despite the time-variability of the streamflow. Others assume that storage is 'randomly sampled' or 'well-mixed' with a fixed volume or fixed exchange rate. Here we present a formulation for a time-variable TTD that relaxes both the time-invariant and 'randomly sampled' assumptions and only requires a few parameters. The framework is applied to transient storage, representing some combination of in-stream and hyporheic storage, along a stream reach. This approach does not assume that hyporheic and dead-zone storage is fixed or temporally-invariant, and allows for these stores to be sampled in more physically representative ways determined by the system itself. Instead of using probability distributions of age, probability distributions of storage (ranked by age) called Ω functions are used to describe how the off-stream storage is sampled in the outflow. Here the Ω function approach is used to describe hyporheic exchange during diurnal fluctuations in streamflow in a gaining reach of the H.J. Andrews Experimental Forest. The breakthrough curves of salt slugs injected four hours apart over a 28-hour period show a systematic variation in transit time distribution. This new approach allows us to relate these salt slug TTDs to a corresponding time-variation in the Ω function, which can then be related to changes in in-stream storage and hyporheic zone mobilization under varying flow conditions. Thus, we can gain insights into how channel storage and hyporheic exchange are changing through time without having to specify difficult to measure or unmeasurable quantities of our system, such as total storage.

  19. Root-Zone Glyphosate Exposure Adversely Affects Two Ditch Species

    PubMed Central

    Saunders, Lyndsay E.; Koontz, Melissa B.; Pezeshki, Reza

    2013-01-01

    Glyphosate, one of the most applied herbicides globally, has been extensively studied for its effects on non-target organisms. In the field, following precipitation, glyphosate runs off into agricultural ditches where it infiltrates into the soil and thus may encounter the roots of vegetation. These edge-of-field ditches share many characteristics with wetlands, including the ability to reduce loads of anthropogenic chemicals through uptake, transformation, and retention. Different species within the ditches may have a differential sensitivity to exposure of the root zone to glyphosate, contributing to patterns of abundance of ruderal species. The present laboratory experiment investigated whether two species commonly found in agricultural ditches in southcentral United States were affected by root zone glyphosate in a dose-dependent manner, with the objective of identifying a sublethal concentration threshold. The root zone of individuals of Polygonum hydropiperoides and Panicum hemitomon were exposed to four concentrations of glyphosate. Leaf chlorophyll content was measured, and the ratio of aboveground biomass to belowground biomass and survival were quantified. The findings from this study showed that root zone glyphosate exposure negatively affected both species including dose-dependent reductions in chlorophyll content. P. hydropiperdoides showed the greatest negative response, with decreased belowground biomass allocation and total mortality at the highest concentrations tested. PMID:24833234

  20. The role of the hyporheic flow on sediment transport processes : an experimental approach using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Rousseau, Gauthier; Sklivaniti, Angeliki; Vito Papa, Daniel; Ancey, Christophe

    2017-04-01

    The study of river dynamics usually considers a turbulent stream on an impervious bed. However, it is known that part of the total discharge takes place through the erodible bed, especially for mountain rivers. This hyporheic flow (or subsurface flow) is likely to play an active role in the stability of the erodible bed. The question then arises: How does the hyporheic flow affect bed stability and thereby bed load transport? Monitoring hyporheic flow under natural conditions remains a key challenge. Laboratory experiments and new measurement techniques shed new light on this problem. Using PIV-LIF method (Particle Image Velocimetry - Laser Induced Fluorescence) we investigate hyporheic flows through erodible beds. The experiment is conducted in a 2-m-long and 6-cm-width flume with 2-mm-diameter glass beads and 4-mm-diameter natural pebbles under turbulent stream conditions. In parallel, we develop a simple analytical model that accounts for the interaction between the surface and subsurface flows at the bed interface. As the Reynolds number of the hyporheic flow is fairly high (10 to 100), inertia cannot be neglected. This leads us to use the Darcy-Forchheimer law instead of Darcy's law to model hyporheic flows. We show that this model is consistent with the PIV-LIF experimental results. Moreover, the PIV-LIF data show that hyporheic flows modify the velocity profile and turbulence. Our measurements and empirical model emphasize the exchange processes in coarse-grained river for incipient sediment motion.

  1. 49 CFR 222.42 - How does this rule affect Intermediate Quiet Zones and Intermediate Partial Quiet Zones?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... and Intermediate Partial Quiet Zones? 222.42 Section 222.42 Transportation Other Regulations Relating... Horns at Groups of Crossings-Quiet Zones § 222.42 How does this rule affect Intermediate Quiet Zones and..., if the public authority provides Notice of Quiet Zone Continuation, in accordance with § 222.43...

  2. A hydrogeomorphic river network model predicts where and why hyporheic exchange is important in large basins

    USGS Publications Warehouse

    Gomez-Velez, Jesus D.; Harvey, Judson

    2014-01-01

    Hyporheic exchange has been hypothesized to have basin-scale consequences; however, predictions throughout river networks are limited by available geomorphic and hydrogeologic data and by models that can analyze and aggregate hyporheic exchange flows across large spatial scales. We developed a parsimonious but physically based model of hyporheic flow for application in large river basins: Networks with EXchange and Subsurface Storage (NEXSS). We applied NEXSS across a broad range of geomorphic diversity in river reaches and synthetic river networks. NEXSS demonstrates that vertical exchange beneath submerged bed forms rather than lateral exchange through meanders dominates hyporheic fluxes and turnover rates along river corridors. Per kilometer, low-order streams have a biogeochemical potential at least 2 orders of magnitude larger than higher-order streams. However, when biogeochemical potential is examined per average length of each stream order, low- and high-order streams were often found to be comparable. As a result, the hyporheic zone's intrinsic potential for biogeochemical transformations is comparable across different stream orders, but the greater river miles and larger total streambed area of lower order streams result in the highest cumulative impact from low-order streams. Lateral exchange through meander banks may be important in some cases but generally only in large rivers.

  3. Mechanical Properties of Heat Affected Zone of High Strength Steels

    NASA Astrophysics Data System (ADS)

    Sefcikova, K.; Brtnik, T.; Dolejs, J.; Keltamaki, K.; Topilla, R.

    2015-11-01

    High Strength Steels became more popular as a construction material during last decade because of their increased availability and affordability. On the other hand, even though general use of Advanced High Strength Steels (AHSS) is expanding, the wide utilization is limited because of insufficient information about their behaviour in structures. The most widely used technique for joining steels is fusion welding. The welding process has an influence not only on the welded connection but on the area near this connection, the so-called heat affected zone, as well. For that reason it is very important to be able to determine the properties in the heat affected zone (HAZ). This area of investigation is being continuously developed in dependence on significant progress in material production, especially regarding new types of steels available. There are currently several types of AHSS on the world market. Two most widely used processes for AHSS production are Thermo-Mechanically Controlled Processing (TMCP) and Quenching in connection with Tempering. In the presented study, TMCP and QC steels grade S960 were investigated. The study is focused on the changes of strength, ductility, hardness and impact strength in heat affected zone based on the used amount of heat input.

  4. Modeling hyporheic flow paths to quantify nitrous oxide production in stream sediments

    NASA Astrophysics Data System (ADS)

    Quick, A. M.; Farrell, T. B.; Reeder, W. J.; Feris, K. P.; Tonina, D.; Benner, S. G.

    2013-12-01

    Nitrous oxide, a powerful greenhouse gas, is potentially produced in large volumes in the hyporheic zone during both the nitrification and denitrification phases of the nitrogen cycle. The conditions leading to N2O generation are poorly constrained due to difficulty in quantifying dissolved gases (O2, N2O) and chemical species (NH3 and NO3-) along flow paths in the hyporheic zone. We modeled N2O generation in the hyporheic zone using large (1 m length x 10 cm diameter) sediment columns, repeatedly measuring gas and chemical species before, during, and after steady state conditions. Column experiments were conducted with soil carbon percentages ranging from 0.01-0.5% (by dry mass). A linear relationship was observed between soil carbon percentages and oxygen consumption rates. With carbon percentages greater than 0.15%, dissolved oxygen concentrations were depleted to below 1 ppm in 2-4 hours travel time. The drop in dissolved oxygen below 1 ppm corresponded to a marked increase in N2O production within the sediments. The highest and most prolonged N2O production rates were observed in the column with intermediate (0.15%) carbon. After reaching their peak (up to 11 ppb N2O/hour for 0.15% carbon), N2O production rates declined, presumably due to conversion to N2 gas along the denitrification pathway. The amount of N2O generated in our 1D flow paths is directly proportional to the amount of carbon in the sediments and travel time along the flow path in the hyporheic zone (a function of flow rate and hydraulic properties of the sediments). Continuing studies examine the role of microbial populations and increased nitrate inputs on the production rates of N2O from the hyporheic zones of streams.

  5. Potential for 3-D hyporheic exchange flow along a succession of pool-riffle sequences

    NASA Astrophysics Data System (ADS)

    Käser, Daniel; Binley, Andrew; Krause, Stefan; Heathwaite, Louise

    2010-05-01

    Pool-riffle sequences are key geomorphological features that can influence the ecology of streams by inducing a flow exchange between surface water and groundwater - a process called hyporheic exchange flow (HEF). The objective of this research was to test the suitability of a simple 3-D groundwater model for characterizing HEF induced by pool-riffle sequences that had been the focus of experimental study. Three reaches of 20 m were modelled separately. While the bed topography was surveyed and represented at a high resolution, the permeability distribution referred to a simple conceptual model consisting of two superposed layers. One hypothesis was that, despite its simplicity, the calibrated model would produce an acceptable fit between observed and simulated heads because its permeability structure resembled the natural system. The potential complexity of hyporheic flow patterns is well-known, yet this study highlights the usefulness of a simple conceptual model coupled to mechanistic flow equations for describing HEF in 3-D. The error structure of the calibrated model provides insight into various site-specific features. The root mean square error between computed and observed hydraulic heads (relative to the head drop over the structure) is comparable to other studies with more elaborate permeability structures. After calibration, a sensitivity analysis was conducted in order to determine the influence of permeability contrast between the layers, depth of the permeability interface, and basal flux on three HEF characteristics: residence time, lateral and vertical extent, and total flux. Results indicate that permeability characteristics can affect HEF in different ways. For example, the vertical extent is deepest in homogeneous conditions, whereas the lateral extent is not significantly affected by permeability contrast, or by the depth of the interface between the two layers. Thus bank piezometers may be insufficient to calibrate groundwater models of HEF

  6. Impact of Spatial Permeability Distribution Characteristics on Hyporheic Flow Using a Physical System and Simulations

    NASA Astrophysics Data System (ADS)

    Stonedahl, S. H.; Gibson, C.; Reiter, C.; Stonedahl, F.; Sawyer, A. H.

    2015-12-01

    Permeability heterogeneity has been found to significantly affect the volume and speed with which water flows through the hyporheic zone. In this study we investigated how characteristics of spatial permeability distributions within a simple Tóthian system affected hyporheic flow both in physical and simulated domains. Our setup consisted of a 13x7x1 grid of two sediments with a divide bisecting the surface water and top middle cell creating two regions of constant head, which induced flow through the grid. Cells were filled with sand and sandy-gravel in a 2:1 ratio and positioned according to TProGS outputs. We ran a blue dye and salt solution through the system, recorded dye location using time-lapse photography, and measured the electrolytic conductivity as the water exited the system. We also calculated a grid of head values using MODFLOW and simulated flow through the system, yielding simulated dye-fronts, residence times, and exiting salt concentrations for the modeled system. We found strong agreement between the simulation and experimental procedure. We generated an additional 100 grids with the 2:1 sediment ratio for each of the transition probabilities 0.25, 0.50, and 1.0. We simulated these with 1, 2, and 3 order of magnitude differences in permeability values and used moving averages with varying window sizes to investigate the effect of the abruptness of transitions between sediment types. For these cases we compared cumulative residence time distributions, volumetric flux, and deviation from the normalized velocity field for homogenous sediment. We found that smoothing the transition between grid cells increased the volumetric flux, decreased the median residence times, and increased the deviation from a normalized homogenous velocity field. These effects were generally greater on grids created with larger transition probabilities and greater differences in K values.

  7. Where and why hyporheic exchange is important: Inferences from a parsimonious, physically-based river network model

    NASA Astrophysics Data System (ADS)

    Gomez-Velez, J. D.; Harvey, J. W.

    2014-12-01

    Hyporheic exchange has been hypothesized to have basin-scale consequences; however, predictions throughout river networks are limited by available geomorphic and hydrogeologic data as well as models that can analyze and aggregate hyporheic exchange flows across large spatial scales. We developed a parsimonious but physically-based model of hyporheic flow for application in large river basins: Networks with EXchange and Subsurface Storage (NEXSS). At the core of NEXSS is a characterization of the channel geometry, geomorphic features, and related hydraulic drivers based on scaling equations from the literature and readily accessible information such as river discharge, bankfull width, median grain size, sinuosity, channel slope, and regional groundwater gradients. Multi-scale hyporheic flow is computed based on combining simple but powerful analytical and numerical expressions that have been previously published. We applied NEXSS across a broad range of geomorphic diversity in river reaches and synthetic river networks. NEXSS demonstrates that vertical exchange beneath submerged bedforms dominates hyporheic fluxes and turnover rates along the river corridor. Moreover, the hyporheic zone's potential for biogeochemical transformations is comparable across stream orders, but the abundance of lower-order channels results in a considerably higher cumulative effect for low-order streams. Thus, vertical exchange beneath submerged bedforms has more potential for biogeochemical transformations than lateral exchange beneath banks, although lateral exchange through meanders may be important in large rivers. These results have implications for predicting outcomes of river and basin management practices.

  8. Hyporheic flow and dissolved oxygen distribution in fish nests: The effects of open channel velocity, permeability patterns, and groundwater upwelling

    NASA Astrophysics Data System (ADS)

    Cardenas, M. Bayani; Ford, Aimee E.; Kaufman, Matthew H.; Kessler, Adam J.; Cook, Perran L. M.

    2016-12-01

    Many fish lay their eggs in nests, or redds, which they construct in sediment. The viability of eggs depends on many factors, particularly their oxygenation. Because dissolved oxygen is typically saturated within the stream channel, the dissolved oxygen distribution within the redd depends on whether or not hyporheic flow and transport occur within the sediment. We conducted a series of flume and numerical flow and age transport modeling experiments with the aim of understanding the effects of salmonid redds on the hyporheic transport of young oxygenated water. Hyporheic flow was visualized directly through dye injections. Dissolved oxygen throughout the fish nest was measured using a planar optode. Experiments were conducted at various open channel flow velocities in order to understand their effect on dissolved oxygen, and computational simulations considered various sediment textures and ambient groundwater upwelling rates to add process-level insight. We found that, as also shown by previous studies, the redd topography induces multiscale hyporheic flow that effectively flushes the egg pocket location with younger presumably oxygenated water; older water upwells and forms anoxic zones. This pattern persists even at the lowest channel flow rates and at small upwelling velocities of older ambient groundwater which splits the multiscale hyporheic flow cells into isolated pockets. Large groundwater upwelling rates can shut down all the hyporheic flushing. The relatively coarse texture of the redd further promotes hyporheic flushing of the redd sediment with oxygenated water. Thus, redd morphology and sediment texture optimally combine to induce hyporheic exchange flow that delivers young oxygenated water to the egg pocket.

  9. Quantifying nutrient fluxes with a new hyporheic passive flux meter (HPFM)

    NASA Astrophysics Data System (ADS)

    Kunz, Julia Vanessa; Annable, Michael D.; Cho, Jaehyun; von Tümpling, Wolf; Hatfield, Kirk; Rao, Suresh; Borchardt, Dietrich; Rode, Michael

    2017-02-01

    The hyporheic zone is a hotspot of biogeochemical turnover and nutrient removal in running waters. However, nutrient fluxes through the hyporheic zone are highly variable in time and locally heterogeneous. Resulting from the lack of adequate methodologies to obtain representative long-term measurements, our quantitative knowledge on transport and turnover in this important transition zone is still limited.In groundwater systems passive flux meters, devices which simultaneously detect horizontal water and solute flow through a screen well in the subsurface, are valuable tools for measuring fluxes of target solutes and water through those ecosystems. Their functioning is based on accumulation of target substances on a sorbent and concurrent displacement of a resident tracer which is previously loaded on the sorbent.Here we evaluate the applicability of this methodology for investigating water and nutrient fluxes in hyporheic zones. Based on laboratory experiments we developed hyporheic passive flux meters (HPFMs) with a length of 50 cm which were separated in 5-7 segments allowing for vertical resolution of horizontal nutrient and water transport. The HPFMs were tested in a 7 day field campaign including simultaneous measurements of oxygen and temperature profiles and manual sampling of pore water. The results highlighted the advantages of the novel method: with HPFMs, cumulative values for the average N and P flux during the complete deployment time could be captured. Thereby the two major deficits of existing methods are overcome: first, flux rates are measured within one device instead of being calculated from separate measurements of water flow and pore-water concentrations; second, time-integrated measurements are insensitive to short-term fluctuations and therefore deliver more representable values for overall hyporheic nutrient fluxes at the sampling site than snapshots from grab sampling. A remaining limitation to the HPFM is the potential susceptibility to

  10. Dynamic hyporheic exchange at intermediate timescales: testing the relative importance of evapotranspiration and flood pulses

    USGS Publications Warehouse

    Larsen, Laurel G.; Harvey, Judson W.; Maglio, Morgan M.

    2014-01-01

    Hyporheic fluxes influence ecological processes across a continuum of timescales. However, few studies have been able to characterize hyporheic fluxes and residence time distributions (RTDs) over timescales of days to years, during which evapotranspiration (ET) and seasonal flood pulses create unsteady forcing. Here we present a data-driven, particle-tracking piston model that characterizes hyporheic fluxes and RTDs based on measured vertical head differences. We used the model to test the relative influence of ET and seasonal flood pulses in the Everglades (FL, USA), in a manner applicable to other low-energy floodplains or broad, shallow streams. We found that over the multiyear timescale, flood pulses that drive relatively deep (∼1 m) flow paths had the dominant influence on hyporheic fluxes and residence times but that ET effects were discernible at shorter timescales (weeks to months) as a break in RTDs. Cumulative RTDs on either side of the break were generally well represented by lognormal functions, except for when ET was strong and none of the standard distributions applied to the shorter timescale. At the monthly timescale, ET increased hyporheic fluxes by 1–2 orders of magnitude; it also decreased 6 year mean residence times by 53–87%. Long, slow flow paths driven by flood pulses increased 6 year hyporheic fluxes by another 1–2 orders of magnitude, to a level comparable to that induced over the short term by shear flow in streams. Results suggest that models of intermediate-timescale processes should include at least two-storage zones with different RTDs, and that supporting field data collection occur over 3–4 years.

  11. Hyporheic Flow and Residence Times in Heterogeneous Cross-Bedded Sediment

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Cardenas, M. B.

    2008-12-01

    The permeability (k) structure of stream sediment influences hyporheic zone depth, flux, and residence time distribution (RTD). We numerically simulate bedform-induced hyporheic exchange using turbulent open channel flow simulations coupled to groundwater flow models that consider high-resolution k fields. The k fields are from the cross-bedded Massillon Sandstone and modern climbing ripple deposits of the Brazos River (Texas). In both cases, k heterogeneity leads to nested scales of hyporheic exchange and increases the depth of exchange relative to equivalent homogeneous sediment. Solute flux and RTDs differ markedly for the Massillon and Brazos cases, although both exhibit power-law RTDs. In the Massillon case, heterogeneity extends the tail of the RTD, relative to equivalent homogeneous sediment. In the Brazos case, heterogeneity leads to earlier breakthrough of solutes and shorter solute residence times along shallow exchange paths, relative to equivalent homogeneous sediment. These complex transport dynamics would presumably influence the fate of biogeochemical constituents and the thermal regime of sediment. Our case studies suggest, however, that the impact of k heterogeneity on hyporheic zone hydrodynamics is small compared with bed topography and channel hydraulics.

  12. Role of a Streambed's Benthic Biolayer in Enhancing Chemical Reactions in Hyporheic Flow

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.

    2016-12-01

    Chemical processing of metals, nutrients, and organic compounds occurs throughout natural waters, however the rate of reactions often is greater at the streambed interface compared with surface water or deeper groundwater. Hydrologic exchange across the sediment interface brings reactive solutes and fine particulate organic matter from surface waters into contact with the streambed biolayer, a zone with algae and other living microflora and fauna, microbial communities, and reactive geochemical coatings on granular sediments. Compared with surface water or deeper hyporheic sediments, the intrinsic rate of reactions may be stimulated in biolayers because of higher rates of metabolic processing and associated redox reactions. Also, hydrologic transport may enhance reaction rates by relieving potential transport limitations through the re-supply of reactive substrates from surface water. As a result the chemical processing that occurs in the biolayer may far exceed processing that occurs in deeper hyporheic flow. Here I highlight new understanding of enhancement of reaction rates and their hydrologic and biogeochemical controls in streambed biolayers compared with hyporheic flow as a whole. The approach distinguishes and quantifies reaction limitation and transport limitation both at the centimeter-scale within the hyporheic zone and at the river network scale where the effect of streambed reactions accumulates and influences downstream water quality.

  13. The hyporheitron - a tool for measuring hyporheic processes along a discrete flow path in gravel bed streams

    NASA Astrophysics Data System (ADS)

    Beamer, J. P.; Wondzell, S. M.; Haggerty, R.

    2012-12-01

    Respiration in streams and rivers occurs primarily in streambed sediment due to the presence of microbial colonies growing as biofilms on sediment surfaces. Hyporheic exchange through this sediment is thus critical to stream ecosystem processes. However, attempts to study the respiration and other biogeochemical processes in the hyporheic zone continues to prove challenging. We developed a hyporheic mesocosm - or hyporheitron - allowing us to sample pore water along a defined hyporheic flowpath. The hyporheitron consists of a 15.24 cm (6 in) I. D. PVC pipe with a total length of 5.5 m packed with hyporheic sediment. Along the length of the pipe, set 1 m apart, are 5 fully penetrating vertical sampling pipes made from 3.81 cm (1.5 in) I. D. PVC slotted well screen which allow for instruments to be used to measure various hydrologic parameters in the streamtube. The hyporheitron was installed in a large gravel bar spanning a pool-riffle-pool sequence in Lookout Creek, at the H. J. Andrews Experimental Forest, Oregon, USA. The hyporheitron was naturally irrigated, provided a controlled environment for transport studies in the hyporheic zone, and could be altered to allow experiments at different residence times and pore water velocities. Performance of the hyporheitron was evaluated using a conservative tracer (NaCl) injection by measuring the electrical conductivity (EC) breakthrough curves at the sampling locations (1, 2, 3, and 4 m down gradient from injection site) allowing calculation of residence time and pore water velocity in the streamtube. We then examined the effects of stream temperature and residence time on metabolism. By changing the outflow rate of the hyporheitron, the pore water residence time and water temperature signal also changes. Hyporheic water with fast flow rates and short residence times can carry the diurnal fluctuations of the stream water temperature, while water with slow flow rates and longer residence times may have less fluctuation

  14. Hyporheic Temperature Dynamics: Predicting Hyporheic Temperatures Based on Travel Time Assuming Instantaneous Water-Sediment Conduction

    NASA Astrophysics Data System (ADS)

    Kraseski, K. A.

    2015-12-01

    Recently developed conceptual frameworks and new observations have improved our understanding of hyporheic temperature dynamics and their effects on channel temperatures. However, hyporheic temperature models that are both simple and useful remain elusive. As water moves through hyporheic pathways, it exchanges heat with hyporheic sediment through conduction, and this process dampens the diurnal temperature wave of the water entering from the channel. This study examined the mechanisms underlying this behavior, and utilized those findings to create two simple models that predict temperatures of water reentering the channel after traveling through hyporheic pathways for different lengths of time. First, we developed a laboratory experiment to represent this process and determine conduction rates for various sediment size classes (sand, fine gravel, coarse gravel, and a proportional mix of the three) by observing the time series of temperature changes between sediment and water of different initial temperatures. Results indicated that conductions rates were near-instantaneous, with heat transfer being completed on the scale of seconds to a few minutes of the initial interaction. Heat conduction rates between the sediment and water were therefore much faster than hyporheic flux rates, rendering reasonable an assumption of instantaneous conduction. Then, we developed two simple models to predict time series of hyporheic water based on the initial diurnal temperature wave and hyporheic travel distance. The first model estimates a damping coefficient based on the total water-sediment heat exchange through each diurnal cycle. The second model solves the heat transfer equation assuming instantaneous conduction using a simple finite difference algorithm. Both models demonstrated nearly complete damping of the sine wave over the distance traveled in four days. If hyporheic exchange is substantial and travel times are long, then hyporheic damping may have large effects on

  15. Identification of Methanogenic archaea in the Hyporheic Sediment of Sitka Stream

    PubMed Central

    Buriánková, Iva; Brablcová, Lenka; Mach, Václav; Dvořák, Petr; Chaudhary, Prem Prashant; Rulík, Martin

    2013-01-01

    Methanogenic archaea produce methane as a metabolic product under anoxic conditions and they play a crucial role in the global methane cycle. In this study molecular diversity of methanogenic archaea in the hyporheic sediment of the lowland stream Sitka (Olomouc, Czech Republic) was analyzed by PCR amplification, cloning and sequencing analysis of the methyl coenzyme M reductase alpha subunit (mcrA) gene. Sequencing analysis of 60 clones revealed 24 different mcrA phylotypes from hyporheic sedimentary layers to a depth of 50 cm. Phylotypes were affiliated with Methanomicrobiales, Methanosarcinales and Methanobacteriales orders. Only one phylotype remains unclassified. The majority of the phylotypes showed higher affiliation with uncultured methanogens than with known methanogenic species. The presence of relatively rich assemblage of methanogenic archaea confirmed that methanogens may be an important component of hyporheic microbial communities and may affect CH4 cycling in rivers. PMID:24278322

  16. Spatial patterns of hyporheic exchange and biogeochemical cycling around cross-vane restoration structures: Implications for stream restoration design

    NASA Astrophysics Data System (ADS)

    Gordon, Ryan P.; Lautz, Laura K.; Daniluk, Timothy L.

    2013-04-01

    Natural channel design restoration projects in streams often include the construction of cross-vanes, which are stone, dam-like structures that span the active channel. Vertical hyporheic exchange flux (HEF) and redox-sensitive solutes were measured in the streambed around four cross-vanes with different morphologies. Observed patterns of HEF and redox conditions are not dominated by a single, downstream-directed hyporheic flow cell beneath cross-vanes. Instead, spatial patterns of moderate (<0.4 m d-1) upwelling and downwelling are distributed in smaller cells around pool and riffle bed forms upstream and downstream of structures. Patterns of biogeochemical cycling are controlled by dissolved oxygen concentrations and resulting redox conditions, and are also oriented around secondary bed forms. Strong downwelling into the hyporheic zone (0.5-3.5 m d-1) was observed immediately upstream of structures, but was limited to an area 1-2 m from the cross-vane; these hyporheic flow paths likely rejoin the stream at the base of cross-vanes after residence times too short to alter nitrate concentrations or accumulate reaction products. Total hyporheic exchange volumes are ˜0.4% of stream discharge in restored reaches of 45-55 m. Results show that shallow hyporheic flow and associated biogeochemical cycling near cross-vanes is primarily controlled by secondary bed forms created or augmented by the cross-vane, rather than by the cross-vane itself. This study suggests that cross-vane restoration structures benefit the stream ecosystem by creating heterogeneous patches of varying HEF and redox conditions in the hyporheic zone, rather than by processing large amounts of nutrients to alter in-stream water chemistry.

  17. Characteristics of GTA fusion zones and heat affected zones in superalloy 713C

    NASA Astrophysics Data System (ADS)

    Lachowicz, M. B.; Dudziński, W.

    2012-09-01

    In this paper, metallographic examinations, characterising microstructural changes in the 713C superalloy subjected to remelting by GTA method, are presented. In the fusion zone, precipitation of M23C6 or M6C carbides based on chromium and molybdenum was observed. Eutectic mixtures of ( γ- gg')-M x C y type with highly developed morphology were also perceived. It was found that, in the matrix areas with non-homogeneous chemical composition, the eutectic reaction γ-γ' can occur at the temperature close to that of the precipitation of the M x C y carbides. The presence of silicon in the carbide phases can be conducive to lowering their solidification point by creating low-melting compound NbSi. Both in the fusion zone (FZ) and in the heat-affected zone (HAZ), the secondary precipitates of the Ni3(AlTi)- γ' phase, varying in size from 50 to 100 nm, were found. The lattice mismatch factor of the γ and γ' particles was +0.48 % to +0.71 %, which is characteristic of the coherent precipitates of the Ni3Al phase enriched with titanium. No dislocations or stacking faults were observed in the microstructure of the FZ. In the HAZ, some primary undissolved γ' precipitates, with a part of aluminium probably replaced with niobium were observed, which raised their melting point.

  18. Using Measurements of Heat and Pressure to Characterize Hyporheic Exchange through a Riffle-Pool Sequence in the Truckee River, NV

    NASA Astrophysics Data System (ADS)

    Naranjo, R. C.; Niswonger, R. G.; Stone, M.; Davis, C.; McKay, W. A.

    2010-12-01

    Flow in and out of the hyporheic zone is largely influenced by streambed topography, hydraulic conductivity, and stream discharge. The timing and magnitude of stream discharge, and the character and distribution of streambed material can significantly affect the chemical, physical, and biological gradients within the hyporheic zone, and ultimately, the structure and function of aquatic ecosystems. In this study, the spatial and temporal distribution of nutrients was observed along a riffle-pool sequence on the Truckee River, NV. The study area was selected due to the presence of significant algal blooms, which are attributed to increased nutrient loading to the stream in this area. Piezometers were installed into the streambed and the surrounding riparian floodplain to monitor nitrate and dissolved oxygen concentrations, temperature, and pressure at multiple depths beneath the streambed. Measurements of temperature and pressure were used to calibrate a 2-dimensional water- and heat-flow model. The model domain consists of a longitudinal profile that traverses a riffle-pool sequence. The purpose of the model was to determine the relationship between vertical and horizontal seepage velocity, and the nitrate and dissolved oxygen concentrations in the stream sediments. The flow model was calibrated using a uniform random sampling approach to explore the feasible parameter space and to estimate the uncertainty in the velocity estimates. A uniform distribution was selected from ranges in hydraulic and thermal parameters reported in the literature based on sediment texture. Using this approach, streambed heterogeneity, parameter identifiability and parameter sensitivity were determined. Results indicate a trade off exists between matching observed temperatures and observed pressures beneath the streambed. However, the estimated parameters were more unique when both temperature and pressure were used as observations, relative to using solely temperature or pressure

  19. The influence of streambed heterogeneity on hyporheic flow in gravelly rivers.

    PubMed

    Zhou, YaoQuan; Ritzi, Robert W; Soltanian, Mohamad Reza; Dominic, David F

    2014-01-01

    Deposits of open-framework gravel occurring in gravelly streambeds can exert a significant influence on hyporheic flow. The influence was quantified using a numerical model of the hyporheic zone. The model included open-framework gravel stratasets represented with commonly observed characteristics including a volume fraction of about one-third of the streambed sediment, a hydraulic conductivity two orders of magnitude greater than other strata present, and a spatial connectivity forming preferential-flow pathways. The influence of open-framework gravel stratasets on hyporheic flow was much greater than the influence of the channel morphology including meanders, point bars, dunes, and ripples. Seventy percent of the total hyporheic exchange occurred across 30% of the channel boundary at locations of open-framework gravel stratasets. The maximum local interfacial flux rates occurred at these locations, and were orders of magnitude greater than those at other locations. The local flux rates varied by six orders of magnitude over the channel boundary. The composite flow rate through the model with open-framework gravel stratsets was an order of magnitude greater than that through an equivalent but homogeneous model. © 2013, National Ground Water Association.

  20. Hyporheic microbial community development is a sensitive indicator of metal contamination.

    PubMed

    Feris, Kevin P; Ramsey, Philip W; Gibbons, Sean M; Frazar, Chris; Rillig, Matthias C; Moore, Johnnie N; Gannon, James E; Holben, William E

    2009-08-15

    Accurate natural resource damage assessment necessitates monitoring organisms or communities that respond most sensitively to contaminants. Observational studies have demonstrated a correlation between fluvial heavy metal deposition and hyporheic microbial community structure. To establish a causal relationship between sediment metal content and the structure of colonizing bacterial communities, we performed a controlled field experiment River sediments of 1.75-2.36 mm in diameter with five different contaminant concentrations were collected from an environmental metal contamination gradient. Sediments were sterilized and then recolonized by incubation in the hyporheic zone of an uncontaminated river (i.e., a common garden experiment was performed). A significant correlation between hyporheic microbial community structure and heavy metal contamination (R2 = 0.81) was observed. The abundance of two phylogenetic groups was highly correlated with the level of heavy metal contamination (Group I, R2 = 0.96; Group III, R2 = 0.96, most closely affiliated with the alpha- and gamma-proteobacteria, respectively). Microbial community structural responses were detected at metal concentrations an order of magnitude lower than those previously reported to impact benthic macroinvertebrate communities. We conclude that hyporheic microbial communities could offer the most sensitive method for assessing natural resource damage in lotic ecosystems in response to fluvial heavy metal deposition.

  1. Scaling Hyporheic Flow and Biogeochemical Reactions across a Wide Range of Flow and Sediment Conditions in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; O'Connor, B. L.

    2008-12-01

    Aquatic ecosystems are strongly influenced by advective transport from surface water into shallow sediments of the hyporheic zone. The delivery of energy and nutrient-rich materials to microbially and geochemically reactive sediment stimulates high rates of biogeochemical reactions that influence the overall metabolism of the ecosystem as well as influencing the chemistry of downstream receiving waters. Predicting hyporheic flow is difficult because of the potential involvement of many physical processes, including diffusion, shear, bedform-scale advective pumping, bed mobility and bioturbation, turbulence penetration, and head potential- driven groundwater exchange. We used published data from carefully controlled laboratory flume experiments to develop a scaling relationship that predicts hyporheic exchange based on physical descriptors (e.g. shear stress velocity, roughness height, and sediment permeability) that summarize fluid- flow and sediment characteristics. We tested the scaling relationship's predictions by comparing them with more time and labor intensive measurements of solute and reactive tracer transport made in situ in hyporheic zones. In situ measurements were acquired using the USGS MINIPOINT sampler, which allows detailed subsurface measurements without significant disturbance of sediment or the ambient surface or subsurface water fluxes. Fieldwork was undertaken in several streams that varied widely in surface water flow velocities, grain type, median grain size, sediment porosity, sediment organic content, sediment hydraulic conductivity, and groundwater specific discharge. The comparison generally supported the predictive capability of the scaling relationship in complex field settings. The value of the scaling relationship is also indicated for improving rate measurements of biogeochemical reactions in hyporheic zones (e.g. oxygen uptake, denitrification, and manganese oxidation), as well as for estimating the cumulative influence of

  2. Effects of Hyporheic Exchange Flows on Egg Pocket Water Temperature in Snake River Fall Chinook Salmon Spawning Areas

    SciTech Connect

    Hanrahan, Timothy P.; Geist, David R.; Arntzen, Evan V.; Abernethy, Cary S.

    2004-09-24

    The development of the Snake River hydroelectric system has affected fall chinook salmon smolts by shifting their migration timing to a period when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations to improve water temperature and flow conditions during the juvenile chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated. This report describes research conducted by PNNL that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall chinook salmon spawning areas. The potential for improved survival would be gained by increasing the rate at which early life history events proceed (i.e., incubation and emergence), thereby allowing smolts to migrate through downstream reservoirs during early- to mid-summer when river conditions are more favorable for survival. PNNL implemented this research project throughout 160 km of the Hells Canyon Reach (HCR) of the Snake River. The hydrologic regime during the 2002?2003 sampling period exhibited one of the lowest, most stable daily discharge patterns of any of the previous 12 water years. The vertical hydraulic gradients (VHG) between the river and the riverbed suggested the potential for predominantly small magnitude vertical exchange. The VHG also showed little relationship to changes in river discharge at most sites. Despite the relatively small vertical hydraulic gradients at most sites, the results from the numerical modeling of riverbed pore water velocity and hyporheic zone temperatures

  3. Characterisation of transient storage biogeochemistry through groundwater models: the importance of considering microform hyporheic exchange in models at coarser scales

    NASA Astrophysics Data System (ADS)

    Käser, D.; Binley, A.; Heathwaite, L.

    2010-12-01

    Transient storage of stream water in the sediment, or hyporheic exchange flow (HEF), is a primary control on the ecological structure and functions of the hyporheic zone. Increasingly, river rehabilitation programmes require quantitative methods for evaluating its influence on the lotic system, particularly on its pollutant attenuation capacity. Previous studies have already shown the potential of groundwater numerical models to characterize HEF at the channel-unit or the reach scale, for example to compare different rehabilitation scenarios. Modellers and end-users, however, must consider these results with care. The predominant underlying concept implies that HEF is driven by geomorphological features such as pool-riffle or pool-step sequences, and meanders. Yet any degree of streambed roughness is also likely to induced small scale HEF through current-obstacle interaction. Both scales of exchange potentially play a crucial role in terms of biogeochemical transformations. Simulated conceptualisations show that ignoring current-obstacle interactions in groundwater models can lead to strong underestimations of short residence time flow paths or to a misrepresentation of biogeochemical 'hotspots'. For example, ‘Head to tail’ flow paths through riffles are sometimes thought to explain variations in stream water chemistry; however, because riffles are shallow zones of high stream water velocity, they have a potential for pumping exchange that would typically be characterized by a small depth, short residence times, and large fluxes. Little is known on the relative efficiency of these two scales of HEF systems. A sensitivity analysis shows how the interaction of pumping exchange and HEF caused by channel-unit structures may create various small-scale and complex patterns of downwelling and upwelling areas that may control in return the biogeochemical patchiness in the shallow subsurface. There is still much to learn about the interaction of HEF systems of different

  4. Bead temperature effects on FCAW heat-affected zone hardness

    SciTech Connect

    Kiefer, J.H.

    1995-11-01

    Hardness limits for welding procedure qualification are often imposed to lessen the chances of delayed hydrogen cracking during production fabrication. Temper bead techniques have been used by fabricators during these qualifications to improve their chances of success. This practice involves using the heat of additional weld beads to soften the heat-affected zone (HAZ) hardness in the base metal next to the weld where the hardness is the greatest. The technique works under controlled conditions, but the consistency for field use was questionable. This report describes an investigate of the effect of welding parameters, base metal chemical composition, and weld bead placement on HAZ softening. An empirical formula developed from base plate chemical composition, weld cooling time, and temper bead placement can be used to estimate the amount of HAZ tempering. Combined with an appropriate hardness prediction formula, it can help find the welding procedure needed to achieve a desired maximum HAZ hardness, or predict the HAZ hardness of existing welds. Based on the results of the study, bead temperature is not recommended for HAZ hardness control on large scale fabrications.

  5. Nitrate removal rates change over time during tracer tests: towards zone specific reaction rates and watershed budgets.

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Ghassani, A. F.; Avilar, C.; Xiong, X.; Wang, S.

    2016-12-01

    Fertilizer pollution leading to downstream eutrofication and hypoxia is a grand challenge affecting aquatic ecosystems and human activities. Here, we present numerical and experimental results showing that simple tracer tests can provide sufficient data to disentangle the contribution of the water column, the benthic zone and the hyporheic zone to total nitrate uptake at the reach scale. The processes that drive nitrate removal are very different in these three distinct environments and their relative contribution change along the river continuum. The dark, often hypoxic hyporheic zone is where denitrification takes place, while autotrophs temporarily store nitrogen in their biomass in the benthos or the water column. The contribution of pelagic uptake increases downstream as rivers are deeper and slower. Together, these findings can be gathered to empirically inform watershed models and arrive at better nutrient budgets and water quality predictions.

  6. Lateral and longitudinal variation of hyporheic exchange in a piedmont stream pool.

    PubMed

    Ryan, Robert J; Boufadel, Michel C

    2007-06-15

    A conservative solute tracer experiment was conducted in Indian Creek, a small urban stream in Philadelphia, PA, to investigate the role of subsurface properties on the exchange between streamwater and the hyporheic zone (subsurface surrounding the stream). Sodium bromide (NaBr) was used as a conservative tracer, and it was monitored in the surface water and in the bed sediments of a 15 m long pool. Subsurface sampling occurred at 12 locations in the upper layer sediments (extending from 7.5 to 10 cm below the streambed) and 13 locations in the lower layer sediments (extending from 10 to 12.5 cm below the streambed). The hydraulic conductivity (K) of the upper bed sediments and the lower bed sediments was measured in situ. Several locations within the streambed exhibited an increase in tracer concentration with depth, suggesting the presence of horizontal flow paths within this small pool. Over the entire pool, the influence of K heterogeneity on hyporheic exchange was masked by the groundwater head gradient and the morphology of the stream. Together, the groundwater head gradient and stream morphology induced a generally high tracer concentration and fast hyporheic exchange on the left side and center of the channel and low concentrations and slower exchange on the right side. Although the reach-scale effects on the surface water concentration were small, groundwater greatly influenced the local-scale hyporheic exchange in the pool. Understanding how physical stream characteristics control the location and extent of hyporheic exchange pathways will lead to a better understanding of biogeochemical cycling of nutrients and contaminants.

  7. Changes in hyporheic exchange flow following experimental wood removal in a small, low-gradient stream

    NASA Astrophysics Data System (ADS)

    Wondzell, Steven M.; Lanier, Justin; Haggerty, Roy; Woodsmith, Richard D.; Edwards, Richard T.

    2009-05-01

    We investigated the response of hyporheic exchange flow (HEF) to wood removal in a small, low-gradient, gravel bed stream in southeast Alaska using a series of groundwater models built to simulate HEF for the initial conditions immediately after wood removal and 1 month, 2 years, 4 years, and 16 years following wood removal. The models were based on topographic surveys of the stream channel and surrounding floodplain, and surveyed water surface elevations (WSEs) were used to assign stream boundary conditions. Using the groundwater flow model, MODFLOW, and the particle tracking model, MODPATH, we calculated hyporheic exchange fluxes, their residence time distributions, and both longitudinal and plan view spatial patterns of downwelling and upwelling zones. In the first few years, streambed scour and sediment deposition smoothed the streambed and WSE profile, reducing HEF. Also, large contiguous patches of downwelling or upwelling were fragmented, nearly doubling the total number of patches present on the streambed. As the stream continued to adjust to the loss of wood, those trends began to reverse. Accretion of sediment onto alternating bars resulted in better developed pool-riffle morphology, enhanced HEF, and increased residence times and also resulted in downwelling and upwelling zones coalescing into elongated patches along bar margins. This study showed that the hyporheic zone is sensitive to changes in wood loading and that initial changes in HEF resulting from the direct effects of wood removal were contrary to longer-term channel adjustments to changes in wood loading.

  8. Comparison of effects of inset floodplains and hyporheic exchange induced by in-stream structures on solute retention

    NASA Astrophysics Data System (ADS)

    Azinheira, David L.; Scott, Durelle T.; Hession, W.; Hester, Erich T.

    2014-07-01

    The pollution of streams and rivers is a growing concern, and environmental guidance increasingly suggests stream restoration to improve water quality. Solute retention in off-channel storage zones, such as hyporheic zones and floodplains, is typically necessary for significant reaction to occur. Yet, the effects of two common restoration techniques, in-stream structures and inset floodplains, on solute retention have not been rigorously compared. We used MIKE SHE to model hydraulics and solute transport in the channel, on inset floodplains, and in structure-induced hyporheic zones of a third-order stream. We varied hydraulic conditions (winter base flow, summer base flow, and stormflow), geology (hydraulic conductivity), and stream restoration design parameters (inset floodplain length and presence of in-stream structures). The in-stream structures induced hyporheic exchange for approximately 20% of the year (during summer base flow) while inset floodplains were active for approximately 1% of the year (during stormflow). Flow onto inset floodplains and residence times in both the channel and on the floodplains increased nonlinearly with the fraction of bank with floodplains installed. The fraction of streamflow that flowed onto the inset floodplains was 1-3 orders of magnitude higher than that which flowed through the structure-induced hyporheic zone. Yet, residence times and mass storage in the hyporheic zone were 1-5 orders of magnitude larger than that on individual inset floodplains. In our modeling, neither in-stream structures nor inset floodplains had sufficient percent flow and residence times simultaneously to have a substantial impact on dissolved contaminants flowing downstream.

  9. Hyporheic Exchange in a Stream Dammed by Beaver: A 1D Simulation with Spatial Energy Head Gradients and Heterogeneous Hydraulic Conductivity as Drivers

    NASA Astrophysics Data System (ADS)

    Fairfax, E. J.; Small, E. E.

    2016-12-01

    , highly heterogeneous zones of hyporheic exchange when compared to both undammed streams and streams with smaller scale flow obstructions or homogeneous hydraulic conductivities. This result is consistent with previous field and laboratory studies in the literature.

  10. Characterising the Hyporheic Environment and Inferring Groundwater-Surface Water Interactions with Continuous Monitoring of Dissolved Oxygen Using Optical Sensors

    NASA Astrophysics Data System (ADS)

    Soulsby, C.; Malcolm, I. A.; Youngson, A. F.; Tetzlaff, D.

    2007-12-01

    The recent development of optical sensors that facilitate continuous, accurate in situ measurement of dissolved oxygen (DO) levels have revolutionised our ability to monitor the hydrochemistry of the hyporheic zone; an important ecological and biogeochemical hot spot in streams. In addition, this has also provided invaluable insight into the nature of local groundwater - surface water exchange in stream-aquifer systems. This contribution will report the use of optode technology over a 2 year period in a gravel-bed stream draining a 30km2 montane watershed in the Scottish Highlands. Laboratory calibration of the optodes before and after installation confirmed excellent reliability and data quality. Two contrasting sites were monitored where previous work had suggested the hyporheic zone was respectively characterised by upwelling groundwater and downwelling surface water. At each site, replicated logging optodes recorded DO levels in the stream and in hyporheic water at depths of 15cm and 30cm in the stream bed. At the upwelling site, DO levels in the stream were close to 100% throughout the 2 years; levels in the hyporheic zone were highly dynamic and could range between 0 and 100% saturation in a matter of hours. Associated piezometry indicated that such changes were strongly influenced by high water table levels in hillslope groundwater, which resulted in positive pressures allowing the discharge of groundwater through the hyporheic zone. As such, hyporheic DO levels exhibited marked seasonal and inter- annual variability with values close to 100% saturation for prolonged periods during summer and other times when rainfall was low and there was poor connectivity between groundwater and the stream. In contrast, winter and wetter times, when hillslope groundwater-hyporheic connectivity was good, resulted in prolonged periods - up to several months - when hyporheic DO levels were at or close to zero. In addition, short transient spells of low DO followed some small

  11. Product-to-parent reversion processes: Stream-hyporheic spiraling increases ecosystem exposure and environmental persistence

    NASA Astrophysics Data System (ADS)

    Ward, A. S.; Cwiertny, D. M.; Kolodziej, E. P.

    2014-12-01

    The product-to-parent reversion of metabolites of trenbolone acetate (TBA), a steroidal growth promoter used widely in beef cattle production, was recently observed to occur in environmental waters. The rapid forward reaction is by direct photolysis (i.e., photohydration), with the much slower reversion reaction occurring via dehydration in the dark. The objective of this study is to quantify the potential effect of this newly discovered reversible process on TBA metabolite concentrations and total bioactivity exposure in fluvial systems. Here, we demonstrate increased persistence of TBA metabolites in the stream and hyporheic zone due to the reversion process, increasing chronic and acute exposure to these endocrine-active compounds along a stream. The perpetually dark hyporheic zone is a key location for reversion in the system, ultimately providing a source of the parent compound to the stream and increasing mean in-stream concentration of 17α-trenbolone (17α-TBOH) by 40% of the input concentration under representative fluvial conditions. As such, regulatory frameworks for compounds undergoing product-to-parent reversion will require new approaches for assessing total exposure to bioactive compounds. Further, we demonstrate generalized cases for prediction of exposure for species with product-to-parent reversion in stream-hyporheic systems.

  12. The significance of droughts for hyporheic dwellers: evidence from freshwater crayfish

    PubMed Central

    Kouba, Antonín; Tíkal, Jan; Císař, Petr; Veselý, Lukáš; Fořt, Martin; Příborský, Josef; Patoka, Jiří; Buřič, Miloš

    2016-01-01

    Freshwater biodiversity is globally threatened by various factors while severe weather events like long-term droughts may be substantially devastating. In order to remain in contact with the water or stay in a sufficiently humid environment at drying localities, the ability to withstand desiccation by dwelling in the hyporheic zone, particularly through vertical burrowing is crucial. We assessed the ability of three European native and five non-native crayfish as models to survive and construct vertical burrows in a humid sandy-clayey substrate under a simulated one-week drought. Three native species (Astacus astacus, A. leptodactylus, and Austropotamobius torrentium) suffered extensive mortalities. Survival of non-native species was substantially higher while all specimens of Cherax destructor and Procambarus clarkii survived. The native species and Pacifastacus leniusculus exhibited no ability to construct vertical burrows. Procambarus fallax f. virginalis and P. clarkii constructed bigger and deeper burrows than C. destructor and Orconectes limosus. In the context of predicted weather fluctuations, the ability to withstand desiccation through constructing vertical burrows into the hyporheic zone under drought conditions might play a significant role in the success of particular crayfish species, as well as a wide range of further hyporheic-dwelling aquatic organisms in general. PMID:27225308

  13. The significance of droughts for hyporheic dwellers: evidence from freshwater crayfish

    NASA Astrophysics Data System (ADS)

    Kouba, Antonín; Tíkal, Jan; Císař, Petr; Veselý, Lukáš; Fořt, Martin; Příborský, Josef; Patoka, Jiří; Buřič, Miloš

    2016-05-01

    Freshwater biodiversity is globally threatened by various factors while severe weather events like long-term droughts may be substantially devastating. In order to remain in contact with the water or stay in a sufficiently humid environment at drying localities, the ability to withstand desiccation by dwelling in the hyporheic zone, particularly through vertical burrowing is crucial. We assessed the ability of three European native and five non-native crayfish as models to survive and construct vertical burrows in a humid sandy-clayey substrate under a simulated one-week drought. Three native species (Astacus astacus, A. leptodactylus, and Austropotamobius torrentium) suffered extensive mortalities. Survival of non-native species was substantially higher while all specimens of Cherax destructor and Procambarus clarkii survived. The native species and Pacifastacus leniusculus exhibited no ability to construct vertical burrows. Procambarus fallax f. virginalis and P. clarkii constructed bigger and deeper burrows than C. destructor and Orconectes limosus. In the context of predicted weather fluctuations, the ability to withstand desiccation through constructing vertical burrows into the hyporheic zone under drought conditions might play a significant role in the success of particular crayfish species, as well as a wide range of further hyporheic-dwelling aquatic organisms in general.

  14. Streambed sediment controls on hyporheic greenhouse gas production - a microcosm experiment

    NASA Astrophysics Data System (ADS)

    Romejn, Paul; Comer, Sophie; Gooddy, Daren; Ullah, Sami; Hannah, David; Krause, Stefan

    2016-04-01

    Hyporheic zones, as the interfaces between groundwater and surface water, can contribute significantly to whole stream carbon respiration. The drivers and controls of rates and magnitude of hyporheic greenhouse gas (GHG) production remain poorly understood. Recent research has hypothesised that nitrous oxide emissions resulting from incomplete denitrification in nutrient rich agricultural streams may contribute substantially to GHG emissions. This paper reports on a controlled microcosm incubation experiment that has been set up to quantify the sensitivity of hyporheic zone GHG production to temperature and nutrient concentrations. Experiments were conducted with sediment from two contrasting UK lowland rivers (sandstone and chalk). Adopting a gradient approach, sediments with different organic matter and carbon content were analysed from both rivers. Our analytical approach integrated several novel methods, such as push-pull application of the Resazurin/Resorufin smart tracer system for estimation of sediment microbial metabolic activity, high-resolution gas sampling and analysis of methane, carbon dioxide and nitrous oxide by gas chromatography with mass spectrometry, coupled with and high precision in-situ dissolved oxygen measurements. Our results indicate strong temperature controls of GHG production rates, overlapping with the observed impacts of different sediment types. Experimental findings indicate that increased hyporheic temperatures during increasing baseflow and drought conditions may enhance substantially sediment respiration and thus, GHG emissions from the streambed interface. The presented results integrated with field experiments of respiration and GHG emission rates under different treatments. This research advances understanding of scale dependent drivers and controls of whole stream carbon and nitrogen budgets and the role of streambed interfaces in GHG emissions.

  15. Outsized impacts of hyporheic exchange on coupled carbon and nitrogen cycling in river systems

    NASA Astrophysics Data System (ADS)

    Dwivedi, D.; Steefel, C. I.; Arora, B.; Newcomer, M. E.; Hammond, G. E.; Moulton, J. D.; Bhattacharyya, A.; Fox, P. M.; Yuan, X.; Nico, P. S.; Williams, K. H.

    2016-12-01

    Biogeochemical gradients that exist within the hyporheic zone can have an outsized impact on coupled carbon and nitrogen cycling because of groundwater-surface water (GW-SW) interactions occurring across various spatial and temporal scales. Distinct redox processes in the hyporheic zone - specifically resulting from upwelling of nutrient rich groundwater and downwelling of stream water with a higher pH and dissolved oxygen concentrations - lead to the formation of hot spots and hot moments of biogeochemical activity within the river system. To examine the effect of these biogeochemical gradients and redox processes on coupled carbon and nitrogen cycles in the subsurface, we have developed a biotic and abiotic reaction network and integrated it into the reactive transport simulator PFLOTRAN. Reactive flow and transport simulations incorporating two stream meanders of the lower East River watershed in Colorado were used to quantify (1) the effect of hyporheic flow on biogeochemical zonation and (2) the impacts of meander-driven flow paths on coupled carbon and nitrogen cycling within the river system. The three-dimensional flow and reactive transport modeling was able to capture the hydrological and biogeochemical response of the system. In particular, the intra-meander regions showed that dissolved organic carbon, nitrate, and dissolved oxygen values decreased, while iron (Fe (II)) concentrations increased along the meander transect with distance from the stream. Simulation results further demonstrated that hyporheic flow paths within intra-meander regions significantly impacted carbon and nitrogen export into the stream system. An important conclusion from this study is that reactive transport modeling allows the effects of spatial and temporal heterogeneities to be integrated into system behavior, thereby identifying important factors that contribute to the redox gradients at riverine scales.

  16. Streambed sediment controls on hyporheic greenhouse gas production - a microcosm experiment

    NASA Astrophysics Data System (ADS)

    Romeijn, P.; Comer, S.; Krause, S.; Hannah, D. M.; Gooddy, D.

    2015-12-01

    Hyporheic zones, as the interfaces between groundwater and surface water, can contribute significantly to whole stream carbon respiration. The drivers and controls of rates and magnitude of hyporheic greenhouse gas (GHG) production remain poorly understood. Recent research has hypothesised that nitrous oxide emissions resulting from incomplete denitrification in nutrient rich agricultural streams may contribute substantially to GHG emissions. This paper reports on a controlled microcosm incubation experiment that has been set up to quantify the sensitivity of hyporheic zone GHG production to temperature and nutrient concentrations. Experiments were conducted with sediment from two contrasting UK lowland rivers (sandstone and chalk). Adopting a gradient approach, sediments with different organic matter and carbon content were analysed from both rivers. Our analytical approach integrated several novel methods, such as push-pull application of the Resazurin/Resorufin smart tracer system for estimation of sediment microbial metabolic activity, high-resolution gas sampling and analysis of methane, carbon dioxide and nitrous oxide by gas chromatography with mass spectrometry, coupled with and high precision in-situ dissolved oxygen measurements. Our results indicate strong temperature controls of GHG production rates, overlapping with the observed impacts of different sediment types. Experimental findings indicate that increased hyporheic temperatures during increasing baseflow and drought conditions may enhance substantially sediment respiration and thus, GHG emissions from the streambed interface. The presented results integrated with field experiments of respiration and GHG emission rates under different treatments. This research advances understanding of scale dependent drivers and controls of whole stream carbon and nitrogen budgets and the role of streambed interfaces in GHG emissions.

  17. Characterizing hyporheic exchange processes using high-frequency electrical conductivity-discharge relationships on subhourly to interannual timescales

    NASA Astrophysics Data System (ADS)

    Singley, Joel G.; Wlostowski, Adam N.; Bergstrom, Anna J.; Sokol, Eric R.; Torrens, Christa L.; Jaros, Chris; Wilson, Colleen E.; Hendrickson, Patrick J.; Gooseff, Michael N.

    2017-05-01

    Concentration-discharge (C-Q) relationships are often used to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by complexity of the critical zone, such as numerous source waters and hydrochemical nonstationarity. Consequently, researchers must often ignore important runoff pathways and geochemical sources/sinks, especially the hyporheic zone because it lacks a distinct hydrochemical signature. Such simplifications limit efforts to identify processes responsible for the transience of C-Q hysteresis over time. To address these limitations, we leverage the hydrologic simplicity and long-term, high-frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone. We utilize a novel approach to decompose loops into subhysteretic EC-Q dynamics to identify individual mechanisms governing hysteresis across a wide range of timescales. We find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability and that the effects of hyporheic mixing processes on C-Q transience differ in short and long streams. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily to interannual timescales. Last, subhysteretic analysis reveals a period of interannual freshening of glacial meltwater streams related to the effects of unsteady flow on hyporheic exchange. The subhysteretic analysis framework we introduce may be applied more broadly to constrain the processes controlling C-Q transience and advance understanding of catchment evolution.

  18. Modeling hyporheic exchange with unsteady stream discharge and bedform dynamics

    NASA Astrophysics Data System (ADS)

    Boano, Fulvio; Revelli, Roberto; Ridolfi, Luca

    2013-07-01

    Water exchange between streams and hyporheic zones is highly dynamic, and its temporal variation is related to the hydrologic fluctuations of stream discharge and groundwater levels. Unfortunately, predictions of temporal patterns of exchange are difficult due to the many hydrodynamic and morphodynamic processes that are involved and also to their complex nonlinear interactions. Examples of these processes include the evolution of streambed morphology in response to changing streamflow as well as the feedback on surface flow induced by drag resistance due to evolving bed forms. In this work, we have employed a stochastic method to analyze the temporal dynamics of bed form-driven hyporheic exchange in a stream characterized by subcritical flow and daily discharge variations. The method is an extension of previous studies that includes current-induced alterations of bedform size and celerity and their effect on water exchange. The modeling results show that during high flows, stream water penetrates deeper and for longer times in the sediments. At the same time, the predicted rate of water exchange per unit streambed area decreases because the streambed area occupied by each bed form increases faster than the volumetric rate of stream water exchange induced by the same bed form. This reduction can be compensated by the increase in wetted area with discharge, which may provide additional streambed area for water exchange. One the main finding of the study is that the time-averaged values of exchange flux and depths are quite similar to those modeled for a steady mean discharge, while residence times are somewhat lower. Predicted temporal variations of exchange depths and times around their time-averaged values are moderate compared to steady state values.

  19. Impacts of Freshets on Hyporheic Exchange Flow under Neutral Conditions

    NASA Astrophysics Data System (ADS)

    Singh, T.; Wu, L.; Worman, A. L. E.; Hannah, D. M.; Krause, S.; Gomez-Velez, J. D.

    2016-12-01

    Hyporheic zones (HZs) are characterized by the exchange of water, solutes, momentum and energy between streams and aquifers. Hyporheic exchange flow (HEF) is driven by pressure gradients along the sediment-water interface, which in turn are caused by interactions between channel flow and bed topography. With this in mind, changes in channel flow can have significant effects in the hydrodynamic and transport characteristics of HZs. While previous research has improved our understanding of the drivers and controls of HEF, little attention has been paid to the potential impacts of transient dynamic hydrologic forcing, such as freshets. In this study, we use a two-dimensional, homogeneous flow and transport model with a time-varying pressure distribution at the sediment-water interface to explore the dynamic development of HZ characteristics in response to discharge fluctuations (i.e., freshets). With this model, we explore a wide range of plausible scenarios for discharge and bed geometry. Our modelling results show that a single freshet alters the spatial extent and penetration of the HZ, though quantitatively different, when investigated using hydrological (streamlines/flow field) and geochemical (>90% of surface water in streambed) approaches of HZ. We summarize the results of a detailed sensitivity analysis where the effects of hydraulic geometry (slope, amplitude of the streambed), flood characteristics (duration, skewness and magnitude of the flood wave) and biogeochemical timescales (time-scale for oxygen consumption) on the HZ's extent, mean age, and oxic/anoxic zonation are explored. Taking into consideration these multiple morphological characteristics along with variable hydrological controls has clear potential to facilitate process understanding and upscaling.

  20. Variability and comparison of hyporheic water temperatures and seepage fluxes in a small Atlantic salmon stream.

    PubMed

    Alexander, Matthew D; Caissie, Daniel

    2003-01-01

    Ground water discharge is often a significant factor in the quality of fish spawning and rearing habitat and for highly biologically productive streams. In the present study, water temperatures (stream and hyporheic) and seepage fluxes were used to characterize shallow ground water discharge and recharge within thestreambed of Catamaran Brook, a small Atlantic salmon (Salmo salar) stream in central New Brunswick, Canada. Three study sites were instrumented using a total of 10 temperature sensors and 18 seepage meters. Highly variable mean seepage fluxes, ranging from 1.7 x 10(-4) to 2.5 cm3 m(-2) sec(-1), and mean hyporheic water temperatures, ranging from 10.5 degrees to 18.0 degrees C, at depths of 20 to 30 cm in the streambed were dependent on streambed location (left versus right stream bank and site location) and time during the summer sampling season. Temperature data were usefulfor determining if an area of the streambed was under discharge (positive flux), recharge (negative flux), or parallel flow (no flux) conditions and seepage meters were used to directly measure the quantity of water flux. Hyporheic water temperature measurements and specific conductance measurements of the seepage meter sample water, mean values ranging from 68.8 to 157.9 microS/cm, provided additional data for determining flux sources. Three stream banks were consistently under discharge conditions, while the other three stream banks showed reversal from discharge to recharge conditions over the sampling season. Results indicate that the majority of the water collected in the seepage meters was composed of surface water. The data obtained suggests that even though a positive seepage flux is often interpreted as ground water discharge, this discharging water may be of stream water origin that has recently entered the hyporheic zone.The measurement of seepage flux in conjunction with hyporheic water temperature or other indicators of water origin should be considered when attempting to

  1. Hyporheic flow patterns in relation to large river floodplain attributes

    EPA Science Inventory

    Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

  2. Hyporheic exchange in mountain rivers I: Mechanics and environmental effects

    Treesearch

    Daniele Tonina; John M. Buffington

    2009-01-01

    Hyporheic exchange is the mixing of surface and shallow subsurface water through porous sediment surrounding a river and is driven by spatial and temporal variations in channel characteristics (streambed pressure, bed mobility, alluvial volume and hydraulic conductivity). The significance of hyporheic exchange in linking fluvial geomorphology, groundwater, and riverine...

  3. WATER QUALITY EFFECTS OF HYPORHEIC PROCESSING IN A LARGE RIVER

    EPA Science Inventory

    Water quality changes along hyporheic flow paths may have
    important effects on river water quality and aquatic habitat. Previous
    studies on the Willamette River, Oregon, showed that river water follows
    hyporheic flow paths through highly porous deposits created by river...

  4. WATER QUALITY EFFECTS OF HYPORHEIC PROCESSING IN A LARGE RIVER

    EPA Science Inventory

    Water quality changes along hyporheic flow paths may have
    important effects on river water quality and aquatic habitat. Previous
    studies on the Willamette River, Oregon, showed that river water follows
    hyporheic flow paths through highly porous deposits created by river...

  5. Hyporheic flow patterns in relation to large river floodplain attributes

    EPA Science Inventory

    Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

  6. 49 CFR 222.41 - How does this rule affect Pre-Rule Quiet Zones and Pre-Rule Partial Quiet Zones?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Pre-Rule Partial Quiet Zones? 222.41 Section 222.41 Transportation Other Regulations Relating to... Groups of Crossings-Quiet Zones § 222.41 How does this rule affect Pre-Rule Quiet Zones and Pre-Rule...-Rule Quiet Zone may be established by automatic approval and remain in effect, subject to § 222.51,...

  7. Streambed Hydraulic Conductivity Structures: Enhanced Hyporheic Exchange and Contaminant Removal in Model and Constructed Stream

    NASA Astrophysics Data System (ADS)

    Herzog, S.; Higgins, C. P.; McCray, J. E.

    2014-12-01

    Urban- and agriculturally-impacted streams face widespread water quality challenges from excess nutrients, metals, and pathogens from nonpoint sources, which the hyporheic zone (HZ) can capture and treat. However, flow through the HZ is typically small relative to stream flow and thus water quality contributions from the HZ are practically insignificant. Hyporheic exchange is a prominent topic in stream biogeochemistry, but growing understanding of HZ processes has not been translated into practical applications. In particular, existing HZ restoration structures (i.e. cross-vanes) do not exchange water efficiently nor control the residence time (RT) of downwelling streamwater. Here we present subsurface modifications to streambed hydraulic conductivity (K) to drive efficient hyporheic exchange and control RT, thereby enhancing the effectiveness of the HZ. Coordinated high K (i.e. gravel) and low K (i.e. concrete, clay) modifications are termed Biohydrochemical Enhancement structures for Streamwater Treatment (BEST). BEST can simply use native sediments or may also incorporate reactive geomedia to enhance reactions. The contaminant mitigation potentials of BEST were estimated based on hyporheic flow and RT outputs from MODFLOW and MODPATH models and reported nutrient, metal, and pathogen removal rate constants from literature for specific porous media. Reactions of interest include denitrification and removal of phosphate, metals, and E. coli. Simulations showed that BEST structures in series can substantially improve water quality in small streams along reaches of tens of meters. The model results are compared to observed data in tank and constructed stream experiments. Preliminary results with BEST incorporating woodchip geomedia demonstrate rapid denitrification exceeding model predictions. These experiments should establish BEST as a novel stream restoration structure or Best Management Practice (BMP) option to help practitioners achieve stormwater compliance.

  8. Metabolic and structural response of hyporheic microbial communities to variations in supply of dissolved organic matter

    USGS Publications Warehouse

    Findlay, S.E.G.; Sinsabaugh, R. L.; Sobczak, W.V.; Hoostal, M.

    2003-01-01

    Hyporheic sediment bacterial communities were exposed to dissolved organic matter (DOM) from a variety of sources to assess the interdependence of bacterial metabolism and community composition. Experiments ranged from small-scale core perfusions with defined compounds (glucose, bovine serum albumin) to mesocosms receiving natural leaf leachate or water from different streams. Response variables included bacterial production, oxygen consumption, extracellular enzyme activity, and community similarity as manifest by changes in banding patterns of randomly amplified polymorphic DNA (RAPD). All DOM manipulations generated responses in at least one metabolic variable. Additions of both labile and recalcitrant materials increased either oxygen consumption, production, or both depending on background DOM. Enzyme activities were affected by both types of carbon addition with largest effects from the labile mixture. Cluster analysis of RAPD data showed strong divergence of communities exposed to labile versus recalcitrant DOM. Additions of leaf leachate to mesocosms representing hyporheic flow-paths caused increases in oxygen consumption and some enzyme activities with weaker effects on production. Community structure yeas strongly affected; samples from the leachate-amended mesocosms clustered separately from the control samples. In mesocosms receiving water from streams ranging in DOC (0.5-4.5 mg L-1), there were significant differences in bacterial growth, oxygen consumption, and enzyme activities. RAPD analysis showed strongest clustering of samples by stream type with more subtle effects of position along the flowpaths. Responses in community metabolism were always accompanied by shifts in community composition, suggesting carbon supply affects both functional and structural attributes of hyporheic bacterial communities.

  9. Hyporheic Exchange: Analysis of Aquifer Heterogeneity, Channel Morphology and Bedforms- 2D and 3D Simulations Using MODFLOW and MODPATH

    NASA Astrophysics Data System (ADS)

    Matos, J. R.; Welty, C.; Packman, A.

    2005-12-01

    The main purpose of the simulations in this research is the analysis of three-dimensional surface-groundwater interchange in heterogeneous systems. The effects of channel pattern, bed forms and aquifer heterogeneity on flow interactions between stream and groundwater systems are examined in order to contribute for a better understanding of the hyporheic process. A two-dimensional approach was also adopted to allow comparisons with the three-dimensional results. The grid was designed using the correlation scales of the heterogeneous fields and the scale of the stream meanders. MODFLOW and MODPATH were used to evaluate magnitude, direction and spatial distribution of the exchange flow. PMWIN and PMPATH were used as pre and post-processors during the construction of the models and analysis of results. Gaining and losing streams as well as parallel flow and flow across streams were simulated as idealized cases intended to describe how properties of the streambed and aquifer in low-gradient lowland streams contribute to hyporheic exchange. At first a straight river was analyzed then meandering streams were created with a sine curve and variations on wavelength and amplitude. Bed forms were simulated assuming a sinusoidal distribution of pressure head in the bed surface. Aspects of the influence of bedforms on mechanisms such as "pumping" and "turnover" are expected to be addressed with simulations. Flow velocities between 20 and 40 cm/s in the channel were tested with the objective of showing the influence of river morphology and natural bed forms on the flow exchange in the hyporheic zone. Several meander cycles and four levels of hydraulic conductivity variance were analyzed. Results of flow variances along the cross-sections and wetted perimeter show the increasing on hyporheic exchange as the degree of heterogeneity increases. Particle tracking was performed to define hyporheic residence time distributions. When comparing the homogeneous fields with all degrees of

  10. Fracture Behavior of Ultra-Low-Carbon Steel Plate and Heat-Affected-Zone.

    DTIC Science & Technology

    1990-12-01

    ganese-molybdenum steel caused an increase in the DBTT . However. it cannot be assumed that the presence of these TiN cubes always causes detrimental...Department Research & Development Report 0 N Fracture Behavior of Ultra-Low-Carbon Steel Plate and Heat-Affected-Zone by M. G. Vassilaros CO a- Co -e DTIC...Materials Engineering Department Research & Development Report Fracture Behavior of Ultra-Low-Carbon Steel Plate and Heat-Affected-Zone by M. G

  11. Development and application of a heat pulse sensor for in-situ measurement of hyporheic flow

    NASA Astrophysics Data System (ADS)

    Angermann, L.; Lewandowski, J.; Fleckenstein, J. H.; Krause, S.; Nuetzmann, G.

    2011-12-01

    The riverine system represents a continuum of surface water (SW), shallow groundwater (GW) and the interconnecting hyporheic zone (HZ). Within this conceptual model, the HZ fulfills important ecological and biogeochemical functions caused by the high specific surface of sediment, the abundance of organic matter and steep and dynamic gradients in temperature, redox potential and oxygen content. These milieu conditions are controlled by the type and intensity of GW-SW interaction like GW-discharge, SW infiltration, alternating up- and downwelling or dominantly horizontal flow. Depending on flow regimes, the HZ either acts as mixing layer or transit zone with the respective end-member mixing ratios and residence times. Hyporheic exchange fluxes (HEF) at different scales potentially interact, superimpose and prevail each other. It is therefore crucial to understand the complex interactions of SW-GW exchange fluxes from patterns at stream reach scale down to shallow HEF in the top 20cm streambed. Field measurements of GW-SW exchange are technically challenging, especially at the decimeter scale and below. This study presents a novel heat pulse sensor (HPS) which was developed for measuring shallow HEF. The method is based on a short heat pulse which is emitted into the sediment in the depth of 5 to 10cm. Breakthrough curves of the heat propagating through the sediment are recorded by a 3D sensor array around the heat source and analyzed with an analytical solution of the advective-conductive heat transport equation in a cylindrical coordinate system. Theoretical breakthrough curves are calculated for every sensor and flow velocity and the position of the longitudinal axis, which is defined parallel to flow, are fitted. After validation in controlled lab environment, the method was applied in the streambed of 3 subsections of a 250m stream reach with heterogeneous patterns of mainly sandy sediments, representing characteristic streambed conditions of a meandering lowland

  12. Turbulent Hyporheic Exchange in Permeable Sediments

    NASA Astrophysics Data System (ADS)

    Roche, K. R.; Aubeneau, A. F.; Li, A.; Packman, A. I.

    2015-12-01

    Solute delivery from the water column into a streambed strongly influences metabolism in rivers. Current hydrological models simplify surface-subsurface (hyporheic) exchange by treating each domain separately, constraining turbulent flows to the water column. Studies have shown, however, that turbulence penetrates into permeable sediments. Evidence is lacking for how this highly coupled flow regime influences hyporheic exchange. We characterized the dynamics of turbulent exchange between surface and porewaters in a 2.5 m recirculating flume. The channel was packed with 3.8 cm PVC spheres to form a coarse gravel bed, with a total depth of 21 cm. We implanted microsensors onto an array of spheres to measure in situsalt concentrations within the streambed. Water was recirculated in the channel, and concentrated salt solution was continuously injected upstream of the sensor array. We observed solute exchange increased with free-stream Reynolds number and decreased with depth in the sediment bed. Mass of injected solute remaining in the bed decreased rapidly in all cases, with only 10-30% of mass recovered 50 cm downstream of the injection point at Re = 25,000. We observed high-frequency (1-10 Hz) concentration fluctuations at bed depths of at least 4.75 cm, and sporadic low-frequency fluctuations at depths of 12.5 cm. Spectral analysis revealed increased filtering of high frequencies with depth. We used particle-tracking simulations to fit depth-dependent turbulent diffusion profiles to experimental results. These results demonstrate that free-stream turbulence impacts hyporheic mixing deep into permeable streambeds, and mixing is strongly influenced by the coupled surface-subsurface flow field.

  13. Schisandrin A and B affect subventricular zone neurogenesis in mouse.

    PubMed

    Sun, Yi-Xue; Cong, Yan-Long; Liu, Yang; Jin, Bo; Si, Lu; Wang, Ai-Bing; Cai, Huan; Che, Guan-Yu; Tang, Bo; Wang, Chun-Feng; Li, Zi-Yi; Zhang, Xue-Ming

    2014-10-05

    Schisandrin A and B (Sch A and B) are the main effective components extracted from the oriental medicine Schisandra chinensis which is traditionally used to enhance mental and intellectual function. Although their neuroprotective effects have been demonstrated, their influences on neurogenesis are still unknown. In the brain, new neural cells born in the subventricular zone (SVZ) next to the lateral ventricles migrate along the rostral migratory stream (RMS) to the olfactory bulb (OB). To investigate the effects of Sch A and B on neurogenesis in the SVZ-RMS-OB system, Sch A and B were intragastrically administrated at dosages of 1, 10 and 20 mg/kg d respectively. The dose of 10 mg/kg d was selected for further analysis based on the preliminary analysis. In the SVZ, significant increases of phosphohistone H3 positive proliferating cells and the intensity of glial fibrillary acidic protein (GFAP+) cells were noticed in Sch B group. In the RMS, Sch A treatment augmented the intensity of doublecortin positive neuroblasts. In the OB, Sch A decreased tyrosine hydroxylase cells and Calbindin (CalB+) cells, while Sch B increased CalB+ cells and Calretinin (CalR+) cells. These results suggest that Sch B stimulates SVZ proliferation by enhancing GFAP+ cells and improves the survival of OB interneurons, while Sch A promotes neuroblast formation in the RMS but impairs the survival of OB interneurons. The present study provides the first evidence that Sch B exerts neuroprotective functions by enhancing neurogenesis, but Sch A mainly negatively regulates neurogenesis, in the adult SVZ-RMS-OB system.

  14. Retention and transport of nutrients in a third-order stream in northwestern California; hyporheic processes

    USGS Publications Warehouse

    Triska, F.J.; Kennedy, V.C.; Avanzino, R.J.; Zellweger, G.W.; Bencala, K.E.

    1989-01-01

    Chloride and nitrate were coinjected into the surface waters of a third-order stream for 20 d to exmaine solute retention, and the fate of nitrate during subsurface transport. A series of wells (shallow pits) 0.5-10 m from the adjacent channel were sampled to estimate the lateral interflow of water. Two subsurface return flows beneath the wetted channel were also examined. Results indicated that the capacity of the hyporheic zone for transient solute storage and as potential biological habitat varies with channel morphology, bed roughness, and permeability. A conceptual model that considers the groundwater-stream water interface as the fluvial boundary is proposed. -from Authors

  15. The response of streambed nitrogen cycling to spatial and temporal hyporheic vertical flux patterns and associated residence times

    NASA Astrophysics Data System (ADS)

    Briggs, M. A.; Lautz, L. K.; Hare, D. K.

    2011-12-01

    Small beaver dams enhance the development of patchy micro-environments along the stream corridor by trapping sediment and creating complex streambed morphologies. This generates intricate hyporheic flux patterns that govern the exchange of oxygen and redox sensitive solutes between the water column and the streambed, and exert control on the biogeochemical cycling of nitrogen. Specifically, flowpaths from the stream into the subsurface with low residence times create oxic conditions that favor nitrification, while flowpaths with longer residence times become anoxic and favor denitrification. To investigate these processes we collected vertical profiles of pore water upstream of two beaver dams in Wyoming, USA at nine locations with varied morphology. We sampled pore water to the 0.55 m depth every week for five weeks as stream discharge dropped by 45% and subsequently measured concentrations of dissolved oxygen and several redox sensitive solutes, including nitrate. Additionally, estimates of hyporheic flux along these nine vertical profiles through time were made using high-resolution heat data combined with 1-D heat transport modeling. The data show that areas of rapid, deep hyporheic flux at the glides immediately upstream of the dams were oxygen rich, and were generally sites of moderate net nitrification to at least the 0.35 m depth. These conditions were relatively steady over the study period. Hyporheic zones at sediment bars closest to the dams were hotspots of nitrate production to a depth of 0.35 m, with nitrate concentrations increasing by as much as 400% as vertical flux fell sharply and residence times increased over the study period. In contrast, shallow bars farther upstream from the dams showed increasing fluxes and decreased residence times, which caused a shift from net denitrification to net nitrification over the period at shallow depths. These results support previous work indicating threshold behavior of nitrogen cycling in response to

  16. Modelling hyporheic processes for regulated rivers under transient hydrological and hydrogeological conditions

    NASA Astrophysics Data System (ADS)

    Siergieiev, D.; Ehlert, L.; Reimann, T.; Lundberg, A.; Liedl, R.

    2015-01-01

    Understanding the effects of major hydrogeological controls on hyporheic exchange and bank storage is essential for river water management, groundwater abstraction, restoration and ecosystem sustainability. Analytical models cannot adequately represent complex settings with, for example, transient boundary conditions, varying geometry of surface water-groundwater interface, unsaturated and overland flow, etc. To understand the influence of parameters such as (1) sloping river banks, (2) varying hydraulic conductivity of the riverbed and (3) different river discharge wave scenarios on hyporheic exchange characteristics such as (a) bank storage, (b) return flows and (c) residence time, a 2-D hydrogeological conceptual model and, subsequently, an adequate numerical model were developed. The numerical model was calibrated against observations in the aquifer adjacent to the hydropower-regulated Lule River, northern Sweden, which has predominantly diurnal discharge fluctuations during summer and long-lasting discharge peaks during autumn and winter. Modelling results revealed that bank storage increased with river wave amplitude, wave duration and smaller slope of the river bank, while maximum exchange flux decreased with wave duration. When a homogeneous clogging layer covered the entire river-aquifer interface, hydraulic conductivity positively affected bank storage. The presence of a clogging layer with hydraulic conductivity < 0.001 m d-1 significantly reduced the exchange flows and virtually eliminated bank storage. The bank storage return/fill time ratio was positively related to wave amplitude and the hydraulic conductivity of the interface and negatively to wave duration and bank slope. Discharge oscillations with short duration and small amplitude decreased bank storage and, therefore, the hyporheic exchange, which has implications for solute fluxes, redox conditions and the potential of riverbeds as fish-spawning locations. Based on these results, river

  17. A multiscale model for integrating hyporheic exchange from ripples to meanders

    NASA Astrophysics Data System (ADS)

    Stonedahl, Susa H.; Harvey, Judson W.; WöRman, Anders; Salehin, Mashfiqus; Packman, Aaron I.

    2010-12-01

    It is necessary to improve our understanding of the exchange of dissolved constituents between surface and subsurface waters in river systems in order to better evaluate the fate of water-borne contaminants and nutrients and their effects on water quality and aquatic ecosystems. Here we present a model that can predict hyporheic exchange at the bed-form-to-reach scale using readily measurable system characteristics. The objective of this effort was to compare subsurface flow induced at scales ranging from very small scale bed forms up to much larger planform geomorphic features such as meanders. In order to compare exchange consistently over this range of scales, we employed a spectral scaling approach as the basis for a generalized analysis of topography-induced stream-subsurface exchange. The spectral model involves a first-order approximation for local flow-boundary interactions but is fully three-dimensional and includes the lateral hyporheic zone in addition to the flow directly beneath the streambed. The primary model input parameters are stream velocity and slope, sediment permeability and porosity, and detailed measurements of the stream channel topography. The primary outputs are the distribution of water flux across the stream channel boundary, the resulting pore water flow paths, and the subsurface residence time distribution. We tested the bed-form-exchange component of the model using a highly detailed two-dimensional data set for exchange with ripples and dunes and then applied the model to a three-dimensional meandering stream in a laboratory flume. Having spatially explicit information allowed us to evaluate the contributions of both gravitational and current-driven hyporheic flow through various classes of stream channel features including ripples, dunes, bars, and meanders. The model simulations indicate that all scales of topography between ripples and meanders have a significant effect on pore water flow fields and residence time distributions

  18. Effects of hyporheic exchange flows on egg pocket water temperature in Snake River fall Chinook salmon spawning areas

    SciTech Connect

    Hanrahan, T. P.; Geist, D. R.; Arntzen, E. V.; Abernethy, C. S.

    2004-09-01

    The development of the Snake River hydroelectric system has affected fall Chinook salmon smolts by shifting their migration timing to a period (mid- to late-summer) when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River Chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations (e.g., summer flow augmentation) to improve water temperature and flow conditions during the juvenile Chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall Chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated. This report describes research conducted by the Pacific Northwest National Laboratory (PNNL) that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall Chinook salmon spawning areas. This was a pilot-scale study to evaluate these relationships under existing operations of Hells Canyon Dam (i.e., without any prescribed manipulations of river discharge) during the 2002–2003 water year.

  19. Hyporheic Exchange Flows and Biogeochemical Patterns near a Meandering Stream: East Fork of the Jemez River, Valles Caldera National Preserve, New Mexico

    NASA Astrophysics Data System (ADS)

    Christensen, H.; Wooten, J. P.; Swanson, E.; Senison, J. J.; Myers, K. D.; Befus, K. M.; Warden, J.; Zamora, P. B.; Gomez, J. D.; Wilson, J. L.; Groffman, A.; Rearick, M. S.; Cardenas, M. B.

    2012-12-01

    A study by the 2012 Hydrogeology Field Methods class of the University of Texas at Austin implemented multiple approaches to evaluate and characterize local hyporheic zone flow and biogeochemical trends in a highly meandering reach of the of the East Fork of the Jemez River, a fourth order stream in northwestern New Mexico. This section of the Jemez River is strongly meandering and exhibits distinct riffle-pool morphology. The high stream sinuosity creates inter-meander hyporheic flow that is also largely influenced by local groundwater gradients. In this study, dozens of piezometers were used to map the water table and flow vectors were then calculated. Surface water and ground water samples were collected and preserved for later geochemical analysis by ICPMS and HPLC, and unstable parameters and alkalinity were measured on-site. Additionally, information was collected from thermal monitoring of the streambed, stream gauging, and from a series of electrical resistivity surveys forming a network across the site. Hyporheic flow paths are suggested by alternating gaining and losing sections of the stream as determined by stream gauging at multiple locations along the reach. Water table maps and calculated fluxes across the sediment-water interface also indicate hyporheic flow paths. We find variability in the distribution of biogeochemical constituents (oxidation-reduction potential, nitrate, ammonium, and phosphate) along interpreted flow paths which is partly consistent with hyporheic exchange. The variability and heterogeneity of reducing and oxidizing conditions is interpreted to be a result of groundwater-surface water interaction. Two-dimensional mapping of biogeochemical parameters show redox transitions along interpreted flow paths. Further analysis of various measured unstable chemical parameters results in observable trends strongly delineated along these preferential flow paths that are consistent with the direction of groundwater flow and the assumed

  20. The dominating impact of small-scale streambed structural heterogeneity on hyporheic exchange and biogeochemical hotspots in lowland rivers

    NASA Astrophysics Data System (ADS)

    Krause, S.; Gomez, J. D.; Blume, T.; Weatherill, J.; Angermann, L.; Munz, M.; Tecklenburg, C.; Cassidy, N. J.; Wilson, J. L.

    2013-12-01

    Exchange fluxes and residence times of groundwater and surface water at aquifer-river interfaces are driven by hydrodynamic and hydrostatic forcing. While previous research, with a predominantly surface water perspective, has mainly focussed on the impact of bedform controlled advective pumping on hyporheic zone extent and residence times, little attention has been paid to the impact of streambed structural controls on groundwater up-welling patterns and its implications for hyporheic exchange. Following a combined experimental and model-based approach, this paper highlights the impact of small-scale streambed structural variability on spatial patterns of hyporheic exchange flow, residence time distribution and the development of hotspots of biogeochemical cycling in the hyporheic zone of a lowland river. Combining Fibre-optic DTS and active Heat Pulse Sensing, this study identified distinct low conductivities peat and clay structures in the streambed to determine patterns, quantity and temporal dynamics of groundwater up-welling. Model simulations confirmed that streambed structure controlled patterns of groundwater up-welling exceeded the impact of bedform driven fluxes on aquifer-river exchange flow patterns. In addition, enhanced residence times of up-welling groundwater in and around these organic rich structures lead to an increase in dissolved oxygen consumption and the development of anaerobic denitrification hotspots. The resulting increases in streambed nitrate attenuation as well as enhanced production of CO2, CH4 and N2O as respiration end products highlight the importance of biogeochemical hotspots at aquifer-river interfaces under the dominant impact of streambed structural heterogeneity. Conceptual model of streambed hydrofacies controlling groundwater up-welling in a typical lowland river including their effect on heat transport at the aquifer-river interface (the star indicates the temperature of the surface water). B: core logs of exemplary

  1. Sedimentary roles on hyporheic exchange in karst conduits at low Reynolds numbers by laboratory experiments

    NASA Astrophysics Data System (ADS)

    Wu, Yuexia; Hunkeler, Daniel

    2017-04-01

    The relative roles of the sediment grain size/permeability, conduit flow rate and conduit geometry/angle on the hyporheic exchange between a karst conduit and its underlying sediments under low Reynolds numbers (Re) were investigated by means of laboratory experiments and numerical simulations. Two laboratory analogues consisting of siphon structured glass tubes (with bend angles of 15° and 45°) were used for the experimental studies. Tracer experiments were performed in each analogue with sediments of variable grain size (0.45 mm, 0.4-0.7 mm, 1 mm) to characterize the transport properties of contaminants originating from the sediments. Numerical simulations were used to probe the exchange flow patterns and exchange flux magnitudes between the conduit and sediment. Tracer experiments demonstrated a zone of forward flow and a zone of reverse flow in the sediments that were independent of grain size, which were reproduced well by numerical simulations. The exchange flux ranged from 0.02 % for fine grains to 2 % for coarse grains under the experimental flow conditions. A linear relationship between the exchange flux and the conduit Re value, which was independent of the conduit geometry and sediment grain size, was established with numerical simulations. This study demonstrated that sediment grain size/permeability has no influence on the exchange flow patterns. However, relative to the conduit flow rate and conduit geometry/angle, sediment permeability has a much stronger influence on the exchange rate of hyporheic flow.

  2. Sedimentary roles on hyporheic exchange in karst conduits at low Reynolds numbers by laboratory experiments

    NASA Astrophysics Data System (ADS)

    Wu, Yuexia; Hunkeler, Daniel

    2017-05-01

    The relative roles of the sediment grain size/permeability, conduit flow rate and conduit geometry/angle on the hyporheic exchange between a karst conduit and its underlying sediments under low Reynolds numbers (Re) were investigated by means of laboratory experiments and numerical simulations. Two laboratory analogues consisting of siphon structured glass tubes (with bend angles of 15 and 45°) were used for the experimental studies. Tracer experiments were performed in each analogue with sediments of variable grain size (0.45 mm, 0.4-0.7 mm, 1 mm) to characterize the transport properties of contaminants originating from the sediments. Numerical simulations were used to probe the exchange flow patterns and exchange flux magnitudes between the conduit and sediment. Tracer experiments demonstrated a zone of forward flow and a zone of reverse flow in the sediments that were independent of grain size, which were reproduced well by numerical simulations. The exchange flux ranged from 0.02% for fine grains to 2% for coarse grains under the experimental flow conditions. A linear relationship between the exchange flux and the conduit Re value, which was independent of the conduit geometry and sediment grain size, was established with numerical simulations. This study demonstrated that sediment grain size/permeability has no influence on the exchange flow patterns; however, relative to the conduit flow rate and conduit geometry/angle, sediment permeability has a much stronger influence on the exchange rate of hyporheic flow.

  3. Sedimentary roles on hyporheic exchange in karst conduits at low Reynolds numbers by laboratory experiments

    NASA Astrophysics Data System (ADS)

    Wu, Yuexia; Hunkeler, Daniel

    2017-01-01

    The relative roles of the sediment grain size/permeability, conduit flow rate and conduit geometry/angle on the hyporheic exchange between a karst conduit and its underlying sediments under low Reynolds numbers (Re) were investigated by means of laboratory experiments and numerical simulations. Two laboratory analogues consisting of siphon structured glass tubes (with bend angles of 15 and 45°) were used for the experimental studies. Tracer experiments were performed in each analogue with sediments of variable grain size (0.45 mm, 0.4-0.7 mm, 1 mm) to characterize the transport properties of contaminants originating from the sediments. Numerical simulations were used to probe the exchange flow patterns and exchange flux magnitudes between the conduit and sediment. Tracer experiments demonstrated a zone of forward flow and a zone of reverse flow in the sediments that were independent of grain size, which were reproduced well by numerical simulations. The exchange flux ranged from 0.02% for fine grains to 2% for coarse grains under the experimental flow conditions. A linear relationship between the exchange flux and the conduit Re value, which was independent of the conduit geometry and sediment grain size, was established with numerical simulations. This study demonstrated that sediment grain size/permeability has no influence on the exchange flow patterns; however, relative to the conduit flow rate and conduit geometry/angle, sediment permeability has a much stronger influence on the exchange rate of hyporheic flow.

  4. Mechanical Properties and Microstructural Evolution of Simulated Heat-Affected Zones in Wrought Eglin Steel

    NASA Astrophysics Data System (ADS)

    Leister, Brett M.; DuPont, John N.; Watanabe, Masashi; Abrahams, Rachel A.

    2015-12-01

    A comprehensive study was performed to correlate the mechanical properties and microstructural evolution in the heat-affected zone of Eglin steel. A Gleeble 3500 thermo-mechanical simulator was used to simulate weld thermal cycles with different peak temperatures at a heat input of 1500 J/mm. These samples underwent mechanical testing to determine strength and toughness in the as-welded and post-weld heat-treated conditions. The inter-critical heat-affected zone (HAZ) had the lowest strength following thermal simulation, while the fine-grain and coarse-grain heat-affected zone exhibited increased strength when compared to the inter-critical HAZ. The toughness of the heat-affected zone in the as-simulated condition is lower than that of the base metal in all regions of the HAZ. Post-weld heat treatments (PWHTs) increased the toughness of the HAZ, but at the expense of strength. In addition, certain combinations of PWHTs within specific HAZ regions exhibited low toughness caused by tempered martensite embrittlement or intergranular failure. Synchrotron X-ray diffraction data have shown that Eglin steel has retained austenite in the fine-grain HAZ in the as-simulated condition. In addition, alloy carbides (M23C6, M2C, M7C3) have been observed in the diffraction spectra for the fine-grain and coarse-grain HAZ following a PWHT of 973 K (700 °C)/4 hours.

  5. Variation of Hyporheic Exchange Metrics along an Urbanization Gradient

    NASA Astrophysics Data System (ADS)

    Hester, E. T.; Cranmer, E. N.

    2010-12-01

    Hyporheic exchange is well established as being important for stream ecosystems and water quality. Urbanization is known to greatly alter hydrologic and geomorphic conditions as well as water quality in streams, leading to extirpation of aquatic organisms and degradation of ecosystem function. Yet the impact of urbanization on hyporheic exchange and function is poorly understood. We utilized metrics that quantify the potential for hyporheic exchange to characterize ten 1st - 3rd order streams that span an urbanization gradient near Washington, DC. Sites were also chosen to minimize variation in other relevant dimensions like parent geology, degree of agriculture, channel slope, and stream order. Metrics of hyporheic potential included horizontal and vertical hydraulic conductivity of sediments (measured via falling head tests), vertical channel thalweg complexity (measured via topographic surveys), and channel planform sinuosity (measured via aerial orthophotos). Degree of urbanization was characterized via both local conditions (e.g., riparian buffer width) and contributing watershed conditions (e.g., percent impervious). Resulting data were first analyzed narratively, by noting the impact of local urbanization stresses (e.g., individual stormwater outfalls) on metrics of hyporheic potential at an individual site level. Data were subsequently analyzed more globally, by regressing metrics of hyporheic potential against various metrics of urbanization within the contributing watershed. Preliminary results reveal a complex picture, where urbanization exerts broad control on hyporheic exchange potential, but individual site circumstances exhibit considerable ability to locally modify such larger landscape trends. For example, channel sinuosity generally decreases with increasing urbanization, reflecting increased constraints on channel meandering, but local riparian corridor widths can vary tremendously, imparting considerable scatter to the relationship. We present

  6. Distributed Temperature Sensing of hyporheic flux patterns in varied space and time around beaver dams

    NASA Astrophysics Data System (ADS)

    Briggs, M.; Lautz, L. K.; McKenzie, J. M.

    2010-12-01

    Small dams enhance hyporheic interaction by creating punctuated head differentials along streams, thereby affecting redox conditions and nutrient cycling in the streambed. As beaver populations return, they create dams that alter hyporheic flowpaths locally, an effect which may integrate at the reach scale to produce a net hydrological and ecological functional change. Streambed heterogeneity around beaver dams combines with varied morphology, head differentials and stream velocities to create patterns of hyporheic seepage flux that vary in both space and time. Heat has been used as a groundwater tracer for many years, but it’s dependence on spatially disperse point measurements has only recently been resolved by the development of Distributed Temperature Sensing (DTS) fiber-optic technology. Modified applications of DTS include wrapping the fiber around a mandrel to increase spatial resolution dramatically. Wrapped configurations can be installed vertically in the streambed to provide data for heat transport modeling of vertical hyporheic flux. The vertically continuous dataset generated with DTS may be more informative regarding subsurface heterogeneity than more commonly used spatially discrete thermocouples. We installed a total of nine wrapped DTS rods with 1.4 cm vertical spatial resolution above two beaver dams in Cherry Creek, a tributary of the Little Popo Agie River in Lander, Wyoming, USA. Data was collected over 20 min periods in dual-ended mode continuously for one month (10-Jul to 10-Aug 2010) during baseflow recession, as discharge dropped from 384 Ls-1 to 211 Ls-1. The temperature rods were installed to at least 0.75 m depth within bed sediments at varied distances upstream of the dams in diverse stream morphological units, which ranged from gravel bars to clay lined pools. Diurnal fluctuations in stream temperature were generally between 4.5 and 5.5 oC in amplitude, imparting a strong potential signal for propagation into the bed due to advective

  7. Influence of varying hydraulic conditions on hyporheic exchange and reactions in an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Maier, Uli; Fleckenstein, Jan H.

    2014-05-01

    In the hyporheic zone (HZ) important biogeochemical transformations occur with crucial impact on nutrient cycling in fluvial systems. Here we investigate the interplay between stream flow and HZ exchange of a natural in-stream gravel bar (ISGB), by using three-dimensional steady state simulations of a coupled surface and subsurface numerical model. Stream flow is simulated by the open source computational fluid dynamics (CFD) software OpenFOAM. It is sequentially coupled by the hydraulic head distribution to the top boundary of the groundwater model code MIN3P, simulating flow, solute transport, aerobic respiration (AR) and denitrification (DN) in the HZ. The modelling approach is validated to the stream rating curve and the subsurface travel times in the ISGB based on field measurements. Hydraulic conditions are varied by stream discharge, ranging from low discharge, sufficient to allow stream water flow through both stream channels surrounding the ISGB (0.1 m³/s), to conditions where the ISGB is completely submerged (5.0 m³/s). Ambient groundwater flow is assigned by constant head boundaries upstream and downstream of the ISGB. By varying stream discharge or ambient groundwater heads the general flow field of the ISGB can be adjusted from losing via neutral to gaining conditions. Reactive transport scenarios consider stream water as the primary source of dissolved oxygen and dissolved organic carbon. Furthermore, two nitrate sources originated from the stream water and ambient groundwater are included in the model. Results show that highest hyporheic exchange and longest residence times occur under neutral conditions, where the extent of the hyporheic flow cell is at a maximum. Hence, the stronger the system is gaining and losing, the smaller is the hyporheic exchange flux and the shorter are the residence times in the HZ of the ISGB. AR and DN efficiencies of the ISGB are lowest under gaining conditions because infiltrating solutes are restriced to the

  8. Tubulin cytoskeleton in elongation zone of Arabidopsis root is affected by clinorotation

    NASA Astrophysics Data System (ADS)

    Shevchenko, G.; Kalinina, Ya.; Kordyum, E.

    Our aim is to find out how clinorotation influences root growth For this purpose we followed the dynamics of tubulin cytoskeleton cortical and endoplasmic microtubules in cells from elongation zone of Arabidopsis roots transfected with GFP-MAP4 3 day old seedlings In distal part of elongation zone in epidermal cells mainly distinct endoplasmic microtubules were observed Prominent cortical microtubules start to be evident in cells in central elongation zone Under clinorotation clusters formed by MAP4 appear in all parts of elongation zone evidencing that microtubule arrangement is somehow distorted there Application of cytochalasin D which disrupts proper functioning of actin cytoskeleton in controls affected mainly the endoplasmic microtubules in cells with isotropic growth where MAP4 was clustered Under clinorotation disruption of actin cytoskeleton by cytochalasin D caused appearance of MAP4 clusters in cells growing anisotropically In those cells cortical microtubules are affected as well as endoplasmic Due to the fact that cortical microtubules are responsible for ordered growth of plant cell and are arranged into a robust structure change of their organization under clinorotation could impact cell growth This proves that cells in elongation zone switching their growth mode from isotropic to anisotropic are rather sensitive to altered gravity The fact that more severe distortion of cortical microtubules was noted in cells with damaged actin microfilaments proves mutually related functioning of actin and tubulin cytoskeletons under clinorotation

  9. Green Island and the Hyporheic Zone: Why Restoration matters

    EPA Science Inventory

    Large river floodplains present diverse benefits to communities, yet management strategies often fail to consider the broad suite of ecosystem services provided by these systems. The U.S. Environmental Protection Agency (EPA) is evaluating the benefits associated with restoring l...

  10. Aquifers and hyporheic zones: Towards an ecological understanding of groundwater

    NASA Astrophysics Data System (ADS)

    Hancock, Peter J.; Boulton, Andrew J.; Humphreys, William F.

    2005-03-01

    Ecological constraints in subsurface environments relate directly to groundwater flow, hydraulic conductivity, interstitial biogeochemistry, pore size, and hydrological linkages to adjacent aquifers and surface ecosystems. Groundwater ecology has evolved from a science describing the unique subterranean biota to its current form emphasising multidisciplinary studies that integrate hydrogeology and ecology. This multidisciplinary approach seeks to elucidate the function of groundwater ecosystems and their roles in maintaining subterranean and surface water quality. In aquifer-surface water ecotones, geochemical gradients and microbial biofilms mediate transformations of water chemistry. Subsurface fauna (stygofauna) graze biofilms, alter interstitial pore size through their movement, and physically transport material through the groundwater environment. Further, changes in their populations provide signals of declining water quality. Better integrating groundwater ecology, biogeochemistry, and hydrogeology will significantly advance our understanding of subterranean ecosystems, especially in terms of bioremediation of contaminated groundwaters, maintenance or improvement of surface water quality in groundwater-dependent ecosystems, and improved protection of groundwater habitats during the extraction of natural resources. Overall, this will lead to a better understanding of the implications of groundwater hydrology and aquifer geology to distributions of subsurface fauna and microbiota, ecological processes such as carbon cycling, and sustainable groundwater management. Les contraintes écologiques dans les environnements de subsurface sont en relation directe avec les écoulements des eaux souterraines, la conductivité hydraulique, la biogéochimie des milieux interstitiels, la taille des pores, et les liens hydrologiques avec les aquifères et les écosystèmes adjacents. L'écologie des eaux souterraines a évolué d'une science décrivant uniquement les biotopes souterrains à des études multidisciplinaires qui intègrent l'écologie et l'hydrogéologie. L'approche multidisciplinaire cherche à élucider le fonctionnement des écosystèmes souterrains et leur rôle consistant à maintenir la qualité des eaux souterraines et de surface. Dans les écotones des eaux de la surfaces des aquifères, les gradients géochimiques et les biofilms microbiologiques contrôlent les transformations de la qualité de l'eau. La faune de subsurface (stygofauna) construisent les biofilms, altèrent la taille des pores interstitiels à travers leur mouvement, et transportent physiquement des matériaux à travers l'environnement des eaux souterraines. Par ailleurs, les changements de leur population signalent un déclin de la qualité de l'eau. Une meilleure intégration de l'écologie des eaux souterraines, de la biogeochimie, et de l'hydrogéologie pourra faire avancer de manière efficace de notre compréhension des écosystèmes souterrains, et spécialement en terme de bioremédiation des eaux souterraines contaminées, de maintenance et d'amélioration de la qualité des eaux de surface dépendant des écosystèmes souterrains, et l'amélioration de la protection des habitats des eaux souterraines durant l'extraction des ressources naturelles. En général, cela conduira à une meilleure compréhension de l'implication de l'hydrogéologie et de la géologie des aquifères à la distribution de la faune de subsurface et aux microbiota, aux processus écologiques tels que les cycles du carbone, et la gestion durable des eaux souterraines. Los entornos ecológicos en ambientes subsuperficiales están relacionados directamente con el flujo de agua subterránea, la conductividad hidráulica, biogeoquímica intersticial, tamaño de los poros, y vínculos hidrológicos con acuíferos adyacentes y ecosistemas superficiales. La ecología del agua subterránea ha evolucionado a partir de una ciencia que describe la biota subterránea única hasta alcanzar la forma actual que enfatiza estudios multidisciplinarios que integran hidrogeología y ecología. Este enfoque multidisciplinario busca clarificar la función de los ecosistemas de agua subterránea y sus roles en el mantenimiento de la calidad de agua superficialy subterránea. En ecotonos de agua superficial y de acuíferos, los gradientes geoquímicos y biopelículas microbiales median trans formaciones de calidad de agua. La fauna subsuperficial (estigofauna) se alimenta de biopeliculas, altera el tamaño de los poros intersticiales mediante su movimiento, y transporta físicamente material a través del ambiente de aguas subterráneas. Además, los cambios en sus poblaciones aportan señales de decadencia de calidad de agua. La mejor integración de ecología de aguas subterráneas, biogeoquímica, e hidrogeología incrementará significativamente nuestro entendimiento de ecosistemas subterráneos, especialmente en términos de bioremediación de aguas subterráneas contaminadas, mantenimiento o mejoramiento de calidad de agua superficial en ecosistemas dependientes de agua subterránea, y protección mejorada de habitats de agua subterránea durante la extracción de recursos naturales. Sobretodo, esto conducirá a un mejor entendimiento de las implicaciones de la hidrología de aguas subterráneas y geología del acuífero, de las distribuciones de fauna subsuperficial y microbiota, procesos ecológicos tal como ciclado de carbono, y gestión sostenible de aguas subterráneas.

  11. Green Island and the Hyporheic Zone: Why Restoration matters

    EPA Science Inventory

    Large river floodplains present diverse benefits to communities, yet management strategies often fail to consider the broad suite of ecosystem services provided by these systems. The U.S. Environmental Protection Agency (EPA) is evaluating the benefits associated with restoring l...

  12. Is hyporheic flow an indicator for salmonid spawning site selection?

    NASA Astrophysics Data System (ADS)

    Benjankar, R. M.; Tonina, D.; Marzadri, A.; McKean, J. A.; Isaak, D.

    2015-12-01

    Several studies have investigated the role of hydraulic variables in the selection of spawning sites by salmonids. Some recent studies suggest that the intensity of the ambient hyporheic flow, that present without a salmon egg pocket, is a cue for spawning site selection, but others have argued against it. We tested this hypothesis by using a unique dataset of field surveyed spawning site locations and an unprecedented meter-scale resolution bathymetry of a 13.5 km long reach of Bear Valley Creek (Idaho, USA), an important Chinook salmon spawning stream. We used a two-dimensional surface water model to quantify stream hydraulics and a three-dimensional hyporheic model to quantify the hyporheic flows. Our results show that the intensity of ambient hyporheic flows is not a statistically significant variable for spawning site selection. Conversely, the intensity of the water surface curvature and the habitat quality, quantified as a function of stream hydraulics and morphology, are the most important variables for salmonid spawning site selection. KEY WORDS: Salmonid spawning habitat, pool-riffle system, habitat quality, surface water curvature, hyporheic flow

  13. In-stream geomorphic structures as drivers of hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Hester, Erich T.; Doyle, Martin W.

    2008-03-01

    Common in-stream geomorphic structures such as debris dams and steps can drive hyporheic exchange in streams. Exchange is important for ecological stream function, and restoring function is a goal of many stream restoration projects, yet the connection between in-stream geomorphic form, hydrogeologic setting, and hyporheic exchange remains inadequately characterized. We used the models HEC-RAS, MODFLOW, and MODPATH to simulate coupled surface and subsurface hydraulics in a gaining stream containing a single in-stream geomorphic structure and to systematically evaluate the impact of fundamental characteristics of the structure and its hydrogeologic setting on induced exchange. We also conducted a field study to support model results. Model results indicated that structure size, background groundwater discharge rate, and sediment hydraulic conductivity are the most important factors determining the magnitude of induced hyporheic exchange, followed by geomorphic structure type, depth to bedrock, and channel slope. Model results indicated channel-spanning structures were more effective at driving hyporheic flow than were partially spanning structures, and weirs were more effective than were steps. Across most structure types, downwelling flux rate increased linearly with structure size, yet hyporheic residence time exhibited nonlinear behavior, increasing quickly with size at low structure sizes and declining thereafter. Important trends in model results were observed at the field site and also interpreted using simple hydraulic theory, thereby supporting the modeling approach and clarifying underlying processes.

  14. Systematic Analysis of the Effect of Small Scale Permeability Heterogeneity on Hyporheic Exchange Flux and Residence Times

    NASA Astrophysics Data System (ADS)

    Laube, G.; Schmidt, C.; Fleckenstein, J. H.

    2014-12-01

    The hyporheic zone (HZ) contributes significantly to whole stream biogeochemical cycling. Biogeochemical reactions within the HZ are often transport limited, thus, understanding these reactions requires knowledge about the magnitude of hyporheic fluxes (HF) and the residence time (RT) of these fluxes within the HZ. While the hydraulics of HF are relatively well understood, studies addressing the influence of permeability heterogeneity lack systematic analysis and have even produced contradictory results (e.g. [1] vs. [2]). In order to close this gap, this study uses a statistical numerical approach to elucidate the influence of permeability heterogeneity on HF and RT. We simulated and evaluated 3750 2D-scenarios of sediment heterogeneity by means of Gaussian random fields with focus on total HF and RT distribution. The scenarios were based on ten realizations of each of all possible combinations of 15 different correlation lengths, 5 dipping angles and 5 permeability variances. Roughly 500 hyporheic stream traces were analyzed per simulation, for a total of almost two million stream traces analyzed for correlations between permeability heterogeneity, HF, and RT. Total HF and the RT variance positively correlated with permeability variance while the mean RT negatively correlated with permeability variance. In contrast, changes in correlation lengths and dipping angles had little effect on the examined properties RT and HF. These results provide a possible explanation of the seemingly contradictory conclusions of recent studies, given that the permeability variances in these studies differ by several orders of magnitude. [1] Bardini, L., Boano, F., Cardenas, M.B, Sawyer, A.H, Revelli, R. and Ridolfi, L. "Small-Scale Permeability Heterogeneity Has Negligible Effects on Nutrient Cycling in Streambeds." Geophysical Research Letters, 2013. doi:10.1002/grl.50224. [2] Zhou, Y., Ritzi, R. W., Soltanian, M. R. and Dominic, D. F. "The Influence of Streambed Heterogeneity on

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    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.

  17. A physical explanation for the development of redox microzones in hyporheic flow

    NASA Astrophysics Data System (ADS)

    Briggs, Martin A.; Day-Lewis, Frederick D.; Zarnetske, Jay P.; Harvey, Judson W.

    2015-06-01

    Recent observations reveal a paradox of anaerobic respiration occurring in seemingly oxic-saturated sediments. Here we demonstrate a residence time-based explanation for this paradox. Specifically, we show how microzones favorable to anaerobic respiration processes (e.g., denitrification, metal reduction, and methanogenesis) can develop in the embedded less mobile porosity of bulk-oxic hyporheic zones. Anoxic microzones develop when transport time from the streambed to the pore center exceeds a characteristic uptake time of oxygen. A two-dimensional pore-network model was used to quantify how anoxic microzones develop across a range of hyporheic flow and oxygen uptake conditions. Two types of microzones develop: flow invariant and flow dependent. The former is stable across variable hydrologic conditions, whereas the formation and extent of the latter are sensitive to flow rate and orientation. Therefore, pore-scale residence time heterogeneity, which can now be evaluated in situ, offers a simple explanation for anaerobic signals occurring in oxic pore waters.

  18. A Field Study of How Hydraulic Conductivity Heterogeneity Influences Hyporheic Exchange

    NASA Astrophysics Data System (ADS)

    Ryan, R. J.; Boufadel, M. C.

    2006-05-01

    A conservative solute tracer experiment was conducted in Indian Creek, a small urban stream located in Philadelphia, Pennsylvania to investigate the role of bed sediment hydraulic conductivity on hyporheic (surface- subsurface) exchange. Sodium Bromide (NaBr) was used as a conservative tracer, and it was monitored in the surface water at two stations and in the upper bed sediments (shallow hyporheic zone extending from 7.5 cm to 10 cm below the streambed). The hydraulic conductivity (K) of the upper bed sediments and the lower bed sediments (10 cm to 12.5 cm below the streambed) was measured in situ. High tracer concentrations were observed in the upper layer at locations where the hydraulic conductivity of the upper layer was larger than that of the lower layer. Low concentrations in the upper layer were observed in the converse case. A statistically significant relationship between the mass retained in the upper layer and the difference of K values between layers was observed.

  19. Temporal Signatures of Hyporheic Exchange and Stream Metabolism in Glacial Meltwater Streams, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Torrens, C.

    2016-12-01

    Streams in the McMurdo Dry Valleys [MDV], Antarctica are an important link in biogeochemical cycling between the source glaciers, terminal lakes, and soils. They are also hotspots of metabolic activity in this polar desert system. MDV streams flow 4-12 weeks per year, and are fed only by glacial melt. Most streams remain first-order from glacier origin to terminus in lakes on the valley floor. There are no vascular plants and no higher animals in this landscape, and algal mats provide most of the primary production. When streams are flowing in the austral summer, there is continuous daylight and potentially continuous photosynthesis as well as respiration. Temperature, streamflow, specific electrical conductance (EC) and instream dissolved oxygen (DO) - observed near the termini of the streams - all vary on diel timescales. Streamflow depends on the intensity and aspect of solar irradiance for meltwater generation, and stream length for travel time. Stream temperature is impacted by stream length and insolation. Specific conductance is commonly used as a proxy for interactions of dilute meltwater with the hyporheic zone, where substrate weathers rapidly. Dissolved oxygen is a proxy for instream metabolic processes, also following diel irradiation patterns. Diel patterns in EC and DO tend to be opposite, with DO peaking when EC is low. Differences in the timing and relationship of these cycles can reveal the controls of heterotrophic hyporheic exchange and autotrophic (dominated) primary production on stream metabolism in these streams, providing new information about ecosystem function in this extreme environment.

  20. Analysis of laser ablation dynamics of CFRP in order to reduce heat affected zone

    NASA Astrophysics Data System (ADS)

    Sato, Yuji; Tsukamoto, Masahiro; Nariyama, Tatsuya; Nakai, Kazuki; Matsuoka, Fumihiro; Takahashi, Kenjiro; Masuno, Shinichiro; Ohkubo, Tomomasa; Nakano, Hitoshi

    2014-03-01

    A carbon fiber reinforced plastic [CFRP], which has high strength, light weight and weather resistance, is attractive material applied for automobile, aircraft and so on. The laser processing of CFRP is one of suitable way to machining tool. However, thermal affected zone was formed at the exposure part, since the heat conduction property of the matrix is different from that of carbon fiber. In this paper, we demonstrated that the CFRP plates were cut with UV nanosecond laser to reduce the heat affected zone. The ablation plume and ablation mass were investigated by laser microscope and ultra-high speed camera. Furthermore, the ablation model was constructed by energy balance, and it was confirmed that the ablation rate was 0.028 μg/ pulse in good agreement with the calculation value of 0.03 μg/ pulse.

  1. Inorganic N and P dynamics of Antarctic glacial meltwater streams as controlled by hyporheic exchange and benthic autotrophic communities

    USGS Publications Warehouse

    McKnight, Diane M.; Runkel, R.L.; Tate, C.M.; Duff, J.H.; Moorhead, D.L.

    2004-01-01

    The McMurdo Dry Valleys of South Victoria Land, Antarctica, contain numerous glacial meltwater streams that drain into lakes on the valley floors. Many of the streams have abundant perennial mats of filamentous cyanobacteria. The algal mats grow during streamflow in the austral summer and are in a dormant freeze-dried state during the rest of the year. NO3 and soluble reactive P (SRP) concentrations were lower in streams with abundant algal mats than in streams with sparse algal mats. NO3 and SRP concentrations were higher in the hyporheic zone of a stream with abundant algal mats than in the stream itself. An experimental injection of LiCl, NaNO3, and K3PO4 was conducted in Green Creek, which has abundant algal mats. Substantial hyporheic exchange occurred. The NO3 and PO4 concentrations at 50 m below the injection were 55 ??M and 18 ??M, respectively, during the experiment. NO3 and PO4 concentrations were below the detection limit of 1 to 2 ??M at a site 497 m below the injection during the Cl tracer arrival, indicating a high capacity for nutrient uptake by algal communities. NO2 and NH4 were present at sites 226 and 327 m below the injection, indicating that, in addition to denitrification and algal uptake, dissimilatory NO3 reduction to NO2 and NH4 may be a NO3 sink during transport. Transport modelling with nutrient uptake represented as a 1st-order process yielded reach-scale parameters of 4.3 ?? 10-5 to 3.9 ?? 10-4/s and 1.4 ?? 10-4 to 3.8 ?? 10 -4/s for uptake of NO3 and PO4, respectively. The best match with the observed data was a model in which PO4 uptake occurred only in the main channel and NO3 uptake occurred in the main channel and in the hyporheic zone. Hyporheic NO3 uptake was 7 to 16% of the total uptake for the different stream reaches. These results demonstrate that nutrient flux to the lakes is controlled by hyporheic exchange and nutrient uptake by algal mats in dry valley streams. Streams without algal mats contribute more nutrients to the

  2. Identification and Characterization of Intercritical Heat-Affected Zone in As-Welded Grade 91 Weldment

    NASA Astrophysics Data System (ADS)

    Wang, Yiyu; Kannan, Rangasayee; Li, Leijun

    2016-12-01

    A metallurgical method is proposed for locating the intercritical heat-affected zone in the as-welded Grade 91 steel. New austenitic grains, preferentially formed along the original prior austenite grain boundaries, are characterized to contain finer M23C6 carbides and higher strain levels than the original prior austenite grains. Kurdjumov-Sachs Group 1 variant pairs, with a low misorientation of 7 deg within a martensitic block, are identified as the dominant variants in the new PAGs.

  3. Validation of Temperature Histories for Structural Steel Welds Using Estimated Heat-Affected-Zone Edges

    DTIC Science & Technology

    2016-10-12

    Estimated Heat-Affected-Zone Edges October 12, 2016 Approved for public release; distribution is unlimited. S.G. LambrakoS Center for Computational Materials ...Science Materials Science and Technology Division i REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 3. DATES COVERED (From - To) Standard... material properties. This would entail adjustment of model parameters to achieve agreement between predicted and measured temperature histories at

  4. SCC Initiation in Alloy 600 Heat Affected Zones Exposed to High Temperature Water

    SciTech Connect

    E Richey; DS Morton; RA Etien; GA Young; RB Bucinell

    2006-11-03

    Studies have shown that grain boundary chromium carbides improve the stress corrosion cracking (SCC) resistance of nickel based alloys exposed to high temperature, high purity water. However, thermal cycles from welding can significantly alter the microstructure of the base material near the fusion line. In particular, the heat of welding can solutionize grain boundary carbides and produce locally high residual stresses and strains, reducing the SCC resistance of the Alloy 600 type material in the heat affected zone (HAZ). Testing has shown that the SCC growth rate in Alloy 600 heat affected zone samples can be {approx}30x faster than observed in the Alloy 600 base material under identical testing conditions due to fewer intergranular chromium rich carbides and increased plastic strain in the HAZ [1, 2]. Stress corrosion crack initiation tests were conducted on Alloy 600 HAZ samples at 360 C in hydrogenated, deaerated water to determine if these microstructural differences significantly affect the SCC initiation resistance of Alloy 600 heat affected zones compared to the Alloy 600 base material. Alloy 600 to EN82H to Alloy 600 heat-affected-zone (HAZ) specimens where fabricated from an Alloy 600 to Alloy 600 narrow groove weld with EN82H filler metal. The approximate middle third of the specimen gauge region was EN82H such that each specimen had two HAZ regions. Tests were conducted with in-situ monitored smooth tensile specimens under a constant load, and a direct current electric potential drop was used for in-situ detection of SCC. Test results suggest that the SCC initiation resistance of Alloy 600 and its weld metal follows the following order: EN82H > Alloy 600 HAZ > Alloy 600. The high SCC initiation resistance observed to date in Alloy 600 heat affected zones compared to wrought Alloy 600 is unexpected based on the microstructure of HAZ versus wrought material and based on prior SCC growth rate studies. The observed behavior for the HAZ specimens is likely

  5. Modeling the Ferrite-Austenite Transformation in the Heat-Affected Zone of Stainless Steel Welds

    SciTech Connect

    Vitek, J.M.; David, S.A.

    1997-12-01

    The diffusion-controlled ferrite-austenite transformation in stainless steel welds was modeled. An implicit finite-difference analysis that considers multi-component diffusion was used. The model was applied to the Fe-Cr-Ni system to investigate the ferrite- austenite transformation in the heat-affected zone of stainless steel weld metal. The transformation was followed as a function of time as the heat-affected zone was subjected to thermal cycles comparable to those experienced during gas-tungsten arc welding. The results showed that the transformation behavior and the final microstructural state are very sensitive to the maximum temperature that is experienced by the heat-affected zone. For high maximum exposure temperatures ({approximately} 1300{degree} C), the ferrite formation that occurs at the highest temperatures is not completely offset by the reverse ferrite dissolution at lower temperatures. As a result, for high temperature exposures there is a net increase in the amount of ferrite in the microstructure. It was also found that if compositional gradients are present in the initial ferrite and austenite phases, the extent of the transformation is impacted.

  6. Does human pressure affect the community structure of surf zone fish in sandy beaches?

    NASA Astrophysics Data System (ADS)

    Costa, Leonardo Lopes; Landmann, Júlia G.; Gaelzer, Luiz R.; Zalmon, Ilana R.

    2017-01-01

    Intense tourism and human activities have resulted in habitat destruction in sandy beach ecosystems with negative impacts on the associated communities. To investigate whether urbanized beaches affect surf zone fish communities, fish and their benthic macrofaunal prey were collected during periods of low and high human pressure at two beaches on the Southeastern Brazilian coast. A BACI experimental design (Before-After-Control-Impact) was adapted for comparisons of tourism impact on fish community composition and structure in urbanized, intermediate and non-urbanized sectors of each beach. At the end of the summer season, we observed a significant reduction in fish richness, abundance, and diversity in the high tourist pressure areas. The negative association between visitors' abundance and the macrofaunal density suggests that urbanized beaches are avoided by surf zone fish due to higher human pressure and the reduction of food availability. Our results indicate that surf zone fish should be included in environmental impact studies in sandy beaches, including commercial species, e.g., the bluefish Pomatomus saltatrix. The comparative results from the less urbanized areas suggest that environmental zoning and visitation limits should be used as effective management and preservation strategies on beaches with high conservation potential.

  7. Performance processes within affect-related performance zones: a multi-modal investigation of golf performance.

    PubMed

    van der Lei, Harry; Tenenbaum, Gershon

    2012-12-01

    Individual affect-related performance zones (IAPZs) method utilizing Kamata et al. (J Sport Exerc Psychol 24:189-208, 2002) probabilistic model of determining the individual zone of optimal functioning was utilized as idiosyncratic affective patterns during golf performance. To do so, three male golfers of a varsity golf team were observed during three rounds of golf competition. The investigation implemented a multi-modal assessment approach in which the probabilistic relationship between affective states and both, performance process and performance outcome, measures were determined. More specifically, introspective (i.e., verbal reports) and objective (heart rate and respiration rate) measures of arousal were incorporated to examine the relationships between arousal states and both, process components (i.e., routine consistency, timing), and outcome scores related to golf performance. Results revealed distinguishable and idiosyncratic IAPZs associated with physiological and introspective measures for each golfer. The associations between the IAPZs and decision-making or swing/stroke execution were strong and unique for each golfer. Results are elaborated using cognitive and affect-related concepts, and applications for practitioners are provided.

  8. Heat-affected zone liquation crack on resistance spot welded TWIP steels

    SciTech Connect

    Saha, Dulal Chandra; Chang, InSung; Park, Yeong-Do

    2014-07-01

    In this study, the heat affected zone (HAZ) liquation crack and segregation behavior of the resistance spot welded twinning induced plasticity (TWIP) steel have been reported. Cracks appeared in the post-welded joints that originated at the partially melted zone (PMZ) and propagated from the PMZ through the heat affected zone (HAZ) to the base metal (BM). The crack length and crack opening widths were observed increasing with heat input; and the welding current was identified to be the most influencing parameter for crack formation. Cracks appeared at the PMZ when nugget diameter reached at 4.50 mm or above; and the liquation cracks were found to occur along two sides of the notch tip in the sheet direction rather than in the electrode direction. Cracks were backfilled with the liquid films which has lamellar structure and supposed to be the eutectic constituent. Co-segregation of alloy elements such as, C and Mn were detected on the liquid films by electron-probe microanalysis (EPMA) line scanning and element map which suggests that the liquid film was enrich of Mn and C. The eutectic constituent was identified by analyzing the calculated phase diagram along with thermal temperature history of finite element simulation. Preliminary experimental results showed that cracks have less/no significant effect on the static cross-tensile strength (CTS) and the tensile-shear strength (TSS). In addition, possible ways to avoid cracking were discussed. - Highlights: • The HAZ liquation crack during resistance spot welding of TWIP steel was examined. • Cracks were completely backfilled and healed with divorced eutectic secondary phase. • Co-segregation of C and Mn was detected in the cracked zone. • Heat input was the most influencing factor to initiate liquation crack. • Cracks have less/no significant effect on static tensile properties.

  9. Profiling Hyporheic Microbial Community Nitrogen Cycle and Carbohydrate Active Enzyme Gene Abundances across Seasons

    NASA Astrophysics Data System (ADS)

    Nelson, W. C.; Graham, E.; Stegen, J.

    2016-12-01

    The hyporheic zone (HZ) is the permanently inundated sediment layer between a surface channel and adjacent groundwater-saturated sediments. It has been hypothesized to play a major role in macronutrient (C, N, P) cycling in rivers. The correlation between community taxonomic composition dynamics and functional gene representation is poorly understood for hyporheic communities. To explore how microbial communities respond to temporal changes in environmental conditions, metagenomes were derived from communities captured in sterile sandpacks deployed within the HZ of the Columbia River. HMM databases were used to enumerate protein families present. Functional classification of reads allowed a general assessment of community function over time, while targeted assembly of specific genes enabled investigation of the diversity of organisms encoding these functions. Preliminary analysis of nitrogen cycle pathways shows most gene families examined to have quite steady representation across seasons, with most observed changes being less than an order of magnitude. Analysis of ammonia oxidation genes showed bacterial ammonia oxidizers (AOB) to be stably present across the year, while the archaeal amoA gene increased in late summer, peaking sharply in November, mirroring results from 16S rRNA amplicon analysis which showed an increase in Thaumarcheal OTUs during that same period. Most glycosyl hydrolase GH families had low representation. Highly abundant classes of GH included the GH94 (beta-glucosidase), GH95 (1-2-alpha-L-fucosidase) and GH103 (lytic transglycosylase) families, suggesting activity on plant, fungus and insect polysaccharides and peptidoglycans. Further work is investigating the taxonomy of the sequences identified, to determine how changes in the community composition contribute to the stable gene family profiles observed. These results are intended to work towards a greater understanding of the role of species diversity and functional redundancy in the

  10. Microstructure characterization of heat affected zone after welding in Mod.9Cr–1Mo steel

    SciTech Connect

    Sawada, K.; Hara, T.; Tabuchi, M.; Kimura, K.; Kubushiro, K.

    2015-03-15

    The microstructure of the heat affected zone after welding was investigated in Mod.9Cr–1Mo steel, using TEM and STEM-EDX. The microstructure of thin foil was observed at the fusion line, and at the positions of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm to the base metal side of the fusion line. Martensite structure with very fine lath and high dislocation density was confirmed at all positions. Twins with a twin plane of (112) were locally observed at all positions. Elemental mapping was obtained for all positions by means of STEM-EDX. Inclusions of mainly Si were formed at the fusion line but not at the other positions. No precipitates could be detected at the fusion line or at the position of 0.5 mm. On the other hand, MX particles were observed at the positions of 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm even after welding. M{sub 23}C{sub 6} particles were also confirmed at the positions of 2.0 mm, 2.5 mm, 3.0 mm and 3.5 mm. Very fine equiaxed grains were locally observed at the positions of 2.0 mm and 2.5 mm. The Cr content of the equiaxed grains was about 12 mass%, although the martensite area included about 8 mass% Cr. - Graphical abstract: Display Omitted - Highlights: • Nonequilibrium microstructure of heat affected zone was observed after welding in Mod.9Cr–1Mo steel. • Inclusions containing Si were detected at the fusion line. • Undissolved M{sub 23}C{sub 6} and MX particles were confirmed in heat affected zone. • Twins with a twin plane of (112) were locally observed at all positions. • Very fine ferrite grains with high Cr content were observed in fine grained heat affected zone.

  11. Femtosecond laser heat affected zones profiled in Co/Si multilayer thin films

    SciTech Connect

    Picard, Yoosuf N.; Yalisove, Steven M.

    2008-01-07

    In this letter, we describe an approach for assessing collateral thermal damage resulting from high intensity, femtosecond laser irradiation. Polycrystalline Co thin films deposited on Si (100) substrates and buried under an amorphous Si film were prepared for plan-view transmission electron microscopy (TEM) prior to laser irradiation by femtosecond laser pulses. A heat affected zone (HAZ) resulting from single pulse irradiation at a fluence of 0.9 J/cm{sup 2} was determined by TEM imaging and point-wise selected area diffraction. The spatially Gaussian laser pulse generated a HAZ extending up to 3 {mu}m radially from the femtosecond laser irradiated region.

  12. The effect of welding line heat-affected-zone on the formability of tube hydroforming process

    NASA Astrophysics Data System (ADS)

    ChiuHuang, Cheng-Kai; Hsu, Cheng-En; Lee, Ping-Kun

    2016-08-01

    Tube hydroforming has been used as a lightweight design approach to reduce CO2 emission for the automotive industry. For the high strength steel tube, the strength and quality of the welding line is very important for a successful tube hydroforming process. This paper aims to investigate the effect of the welding line's strength and the width of the heat-affected zone on the tube thinning during the hydroforming process. The simulation results show that both factors play an important role on the thickness distribution during the tube expansion.

  13. Use of slow filtration columns to assess oxygen respiration, consumption of dissolved organic carbon, nitrogen transformations, and microbial parameters in hyporheic sediments.

    PubMed

    Mermillod-Blondin, F; Mauclaire, L; Montuelle, B

    2005-05-01

    Biogeochemical processes mediated by microorganisms in river sediments (hyporheic sediments) play a key role in river metabolism. Because biogeochemical reactions in the hyporheic zone are often limited to the top few decimetres of sediments below the water-sediment interface, slow filtration columns were used in the present study to quantify biogeochemical processes (uptakes of O2, DOC, and nitrate) and the associated microbial compartment (biomass, respiratory activity, and hydrolytic activity) at a centimetre scale in heterogeneous (gravel and sand) sediments. The results indicated that slow filtration columns recreated properly the aerobic-anaerobic gradient classically observed in the hyporheic zone. O2 and NO3- consumptions (256 +/- 13 microg of O2 per hour and 14.6 +/- 6.1 microg of N-NO3- per hour) measured in columns were in the range of values measured in different river sediments. Slow filtration columns also reproduced the high heterogeneity of the hyporheic zone with the presence of anaerobic pockets in sediments where denitrification and fermentation processes occurred. The respiratory and hydrolytic activities of bacteria were strongly linked with the O2 consumption in the experimental system, highlighting the dominance of aerobic processes in our river sediments. In comparison with these activities, the bacterial biomass (protein content) integrated both aerobic and anaerobic processes and could be used as a global microbial indicator in our system. Finally, slow filtration columns are an appropriate tool to quantify in situ rates of biogeochemical processes and to determine the relationship between the microbial compartment and the physico-chemical environment in coarse river sediments.

  14. TEM observation of the heat-affected zone in electron beam welded superalloy Inconel 713C

    SciTech Connect

    Lachowicz, Maciej Dudzinski, Wlodzimierz; Podrez-Radziszewska, Marzena

    2008-05-15

    The paper presents results of microstructural observations and phase analysis of electron-beam-welded fusion zones in superalloy Inconel 713C using transmission electron microscopy. In the fusion zone, a 90% fraction of fine-grained {gamma}' precipitates was found, with sizes up to 30 nm. No dislocations were observed in the precipitates or at the {gamma}-{gamma}' interface. Primary, undissolved inclusions of {gamma}' were found in the heat-affected zone (HAZ). In the HAZ, a very high concentration of dislocations was found at the {gamma}-{gamma}' boundaries, as well as inside the {gamma}' particles and in the {gamma} solid solution. The increased dislocation density indicates loss of coherence of that phase and the creation of a semi-coherent boundary, and is related to dissolution of the particles and intensified diffusion through the interphase {gamma}-{gamma}' boundary. The lattice misfit coefficient {delta}a/a between the {gamma}' particles and {gamma} solution in the HAZ indicates negative values from - 0.20% to - 0.06%. The presence of semi-coherent boundaries and the negative lattice misfit coefficient leads to dislocation locking and can result in cracking in the HAZ.

  15. Effect of Heat-Affected Zone on Spot Weldability in Automotive Ultra High Strength Steel Sheet

    NASA Astrophysics Data System (ADS)

    Nagasaka, Akihiko; Naito, Junya; Chinzei, Shota; Hojo, Tomohiko; Horiguchi, Katsumi; Shimizu, Yuki; Furusawa, Takuro; Kitahara, Yu

    Effect of heat-affected zone (HAZ) on spot weldability in automotive hot stamping (HS) steel sheet was investigated for automotive applications. Tensile test was performed on a tensile testing machine at a crosshead speed of 3 mm/min, using spot welded test specimen (Parallel length: 60 mm, Width: 20 mm, Thickness: 1.4 mm, Tab: 20×20 mm). The spot welding test was carried out using spot welded test specimen with welding current (I) of 6.3 kA to 9.5 kA. Hardness was measured with the dynamic ultra micro Vickers hardness tester. In HS steel, has very high strength of 1 500 MPa, tensile strength (TS) and total elongation (TEl) of the spot welded test specimen of HS steel were lower than those of base metal test specimen. The spot welded test specimen broke in the weld. The Vickers hardnesses (HVs) of base metal and fusion zone of hot stamping steel were around HV500. In addition, the hardness of HAZ was under HV300. The difference of hardness between fusion zone and HAZ was around HV200. The hardness distribution acted as a notch. On the other hand, in dual phase (DP) steel, has low strength of 590 MPa, the TS of spot welded test specimen of DP steel was the same as the base metal test specimen because of the breaking of base metal. The TEl of the spot welded test specimen of DP steel was smaller than that of base metal test specimen. In the spot welded test specimen of DP steel, the hardness of base metal was around HV200 and the fusion zone was around HV500. The hardness distribution did not act as a notch. The difference in hardness between base metal and HAZ acted on a crack initiation at HAZ softening.

  16. In-situ Phase transformation study in fine grained heat affected zone of Grade 91 steels

    SciTech Connect

    Babu, Sudarsanam Suresh; Yamamoto, Yukinori; Santella, Michael L; Yu, Xinghua; Komizo, Prof. Y; Terasaki, Prof. H

    2014-01-01

    Creep strength-enhanced ferritic (CSEF) steels such as the 9 Cr steel [ASTM A387 Grade 91] are widely used as tubing and piping in the new generation of fossil fired power plants. Microstructures in the fine-grained heat affected zone (FGHAZ) may significantly reduce creep strength leading Type IV failures. Current research suggest that reducing pre-weld tempering temperature from 760 C (HTT) to 650 C (LTT) has the potential to double the creep life of these welds. To understand this improvement, time-resolved X-ray diffraction (TRXRD) measurement with synchrotron radiation was used to characterize the microstructure evolution during fine grained heat-affected zone (HAZ) thermal cycling of grade 91 steel. The measurements showed both M23C6 (M=Fe, Cr) and MX (M=Nb, V; X=C,N) are present in the sample after the HTT condition. Near equilibrium fraction of M23C6 was measured in high temperature tempering condition (HTT, 760 C). However, the amount of M23C6 in LTT condition was very low since the diffraction peaks are close to the background. During simulated FGHAZ thermal cycling, the M23C6 partially dissolved in HTT sample. Interestingly, MX did not dissolve in both LTT and HTT samples. Hypothesis for correlation of M23C6 carbide distribution and pre-mature creep failure in FGHAZ will be made.

  17. Visualization of Microstructural Factor Resisting the Cleavage-Crack Propagation in the Simulated Heat-Affected Zone of Bainitic Steel

    NASA Astrophysics Data System (ADS)

    Terasaki, Hidenori; Miyahara, Yu; Ohata, Mitsuru; Moriguchi, Koji; Tomio, Yusaku; Hayashi, Kotaro

    2015-12-01

    Cleavage-crack propagation behavior was investigated in the simulated coarse-grained heat-affected zone (CGHAZ) of bainitic steel using electron backscattering diffraction (EBSD) pattern analysis when a low heat input welding was simulated. From viewpoint of crystallographic analysis, it was the condition in which the Bain zone was smaller than the close-packed plane (CP) group. It was clarified that the Bain zone and CP group boundaries provided crack-propagation resistance. The results revealed that when the Bain zone was smaller than the CP group, crack length was about one quarter the size of that measured when the CP group was smaller than the Bain zone because of the increasing Bain-zone boundaries. Furthermore, it was clarified that the plastic work associated with crack opening and resistance at the Bain and CP boundaries could be visualized by the kernel average misorientation maps.

  18. Hyporheic exchange and fulvic acid redox reactions in an Alpine stream/wetland ecosystem, Colorado Front Range.

    PubMed

    Miller, Matthew P; McKnight, Diane M; Cory, Rose M; Williams, Mark W; Runkel, Robert L

    2006-10-01

    The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (alpha approximately 10(-3) s(-1)). Parallel factor analysis of fluorescence spectra was used to quantifythe redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (lambda = 6.5 x 10(-3) s(-1)) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (lambda = 1.2 x 10(-3) s(-1)) and production of nitrate (lambda = -1.0 x 10(-3) s(-1)) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale.

  19. Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range

    USGS Publications Warehouse

    Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.

    2006-01-01

    The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.

  20. Low temperature sensitization of type 304 stainless steel pipe weld heat affected zone

    NASA Astrophysics Data System (ADS)

    Schmidt, Charles G.; Caligiuri, Robert D.; Eiselstein, Lawrence E.; Wing, Sharon S.; Cubicciotti, Daniel

    1987-08-01

    Large-diameter Type 304 stainless steel pipe weld heat-affected zone (HAZ) was investigated to determine the rate at which low temperature sensitization (LTS) can occur in weld HAZ at nuclear reactor operating temperatures and to determine the effects of LTS on the initiation and propagation of intergranular stress corrosion cracks (IGSCC). The level of sensitization was determined with the electrochemical potentiokinetic reactivation (EPR) test, and IGSCC susceptibility was determined with constant extension rate tests (CERT) and actively loaded compact tension (CT) tests. Substructural changes and carbide compositions were analyzed by electron microscopy. Weld HAZ was found to be susceptible to IGSCC in the as-welded condition for tests conducted in 8-ppm-oxygen, high-purity water at 288 °C. For low oxygen environments ( i.e., 288 °C/0.2 ppm O2 or 180 °C/1.0 ppm O2), IGSCC susceptibility was detected only in weld HAZ that had been sensitized at temperatures from 385 °C to 500 °C. Lower temperature heat treatments did not produce IGSCC. The microscopy studies indicate that the lack of IGSCC susceptibility from LTS heat treatments below 385 °C is a result of the low chromium-to-iron ratio in the carbide particles formed at grain boundaries. Without chromium enrichment of carbides, no chromium depleted zone is produced to enhance IGSCC susceptibility.

  1. Magnetic Barkhausen noise for reliable detection of the heat affected zone in welded ship steel plate

    NASA Astrophysics Data System (ADS)

    Blaow, Mohamed M.; Shaw, Brian A.

    2014-02-01

    The applicability of the Barkhausen noise technique to non-destructively determine the heat affected zone (HAZ) in welded steel plates was investigated. Magnetic Barkhausen noise measurements were conducted on welded hot-rolled low carbon ship steel plates to determine the MBN behaviour following the exposure to elevated heat in a localized region by welding. The exciting field was applied parallel to the weld bead. The results showed a variation in MBN level along a line that crosses the weld bead. The MBN intensity was higher in the near weld material compared with a lower intensity when the measurement setup was moved away from the weld bead in both sides of the weld. The increased MBN level was attributed to the induced residual tensile stresses as a result of the shrinkage of the hot zone. The variation of MBN along the measurement line was eliminated after the welded plate was shot peened. The decrease in MBN intensity after shot peening was attributed to the induced compressive stresses. The results were explained in terms of different mechanisms of interaction of domain walls with residual tensile and compressive stresses.

  2. Zones of impact around icebreakers affecting beluga whales in the Beaufort Sea.

    PubMed

    Erbe, C; Farmer, D M

    2000-09-01

    A software model estimating zones of impact on marine mammals around man-made noise [C. Erbe and D. M. Farmer, J. Acoust. Soc. Am. 108, 1327-1331 (2000)] is applied to the case of icebreakers affecting beluga whales in the Beaufort Sea. Two types of noise emitted by the Canadian Coast Guard icebreaker Henry Larsen are analyzed: bubbler system noise and propeller cavitation noise. Effects on beluga whales are modeled both in a deep-water environment and a near-shore environment. The model estimates that the Henry Larsen is audible to beluga whales over ranges of 35-78 km, depending on location. The zone of behavioral disturbance is only slightly smaller. Masking of beluga communication signals is predicted within 14-71-km range. Temporary hearing damage can occur if a beluga stays within 1-4 km of the Henry Larsen for at least 20 min. Bubbler noise impacts over the short ranges quoted; propeller cavitation noise accounts for all the long-range effects. Serious problems can arise in heavily industrialized areas where animals are exposed to ongoing noise and where anthropogenic noise from a variety of sources adds up.

  3. Stressed Heat Affected Zone Simulations of AerMet 100 Alloy

    SciTech Connect

    Puskar, Joseph D.; Smith, Mark F.

    1999-08-03

    AerMet 100 is a high strength, high fracture toughness alloy designed for use in aerospace applications. In previous work the welding behavior of this alloy has been evaluated, and it has been shown that a softened region in the heat-affected zone (HAZ) is a principal feature of the weld zone. A model for this softening, based on classical theories of precipitate coarsening and isothermal softening data, was developed and found to provide a reasonable description for weld thermal cycle simulation (Gleeble) experiments. Recent work has shown, however, that softening in real welds is not always well predicted by this model, so that additional effects, which are not captured in conventional Gleeble thermal cycle simulations must be addressed. In particular, the stresses associated with real weld HAZ's may modify the softening kinetics. In the current work, Gleeble simulations in both stress-free and stressed conditions have been conducted and the kinetics compared. The accuracy of the thermal model predictions have also been considered regarding their impact on estimated hardness values.

  4. Moessbauer analysis of heat affected zones of an SA 508 steel weld

    SciTech Connect

    Kwon, S.J.; Oh, S.J.; Kim, S.; Lee, S.; Kim, J.H.

    1998-12-18

    Microstructure of a heat affected zone (HAZ) in a weld is influenced by many factors such as chemical composition, welding condition, and peak temperature. It is more complex under multi-pass welding because of the repeated heat input. For the analysis of the HAZ microstructure, optical microscope, electron microscope, and X-ray diffraction techniques have been widely used. However, their application is limited since they can hardly make quantitative analysis of HAZ where numerous phases such as martensite, bainite, ferrite, pearlite, austenite, and carbides are co-existing. Moessbauer spectroscopy, in such a case, is particularly useful due to the capability of quantitative analysis on the fraction of each phase. In this study, phases present in the HAZ of an SA 508 steel were identified, and their fractions were quantitatively determined by Moessbauer spectroscopy in conjunction with microscopic observations.

  5. Plant hybrid zones affect biodiversity: Tools for a genetic-based understanding of community structure

    SciTech Connect

    Whitham, T.G.; Martinsen, G.D.; Keim, P.; Floate, K.D.; Dungey, H.S. |; Potts, B.M.

    1999-03-01

    Plant hybrid zones are dynamic centers of ecological and evolutionary processes for plants and their associated communities. Studies in the wild and in gardens with synthetic crosses showed that hybrid eucalypts supports the greatest species richness and abundances of insect and fungal taxa. In an updated review of 152 case studies of taxa associated with diverse hybridizing systems, there were 43 (28%) cases of hybrids being more susceptible than their parent species, 7 (5%) resistant, 35 (23%) additive, 35 (23%) dominant, and 32 (21%) showed no response to hybridization. Thus, most taxa respond to hybrids in ways that result in equal or greater abundance, and hybrids tend to accumulate the taxa of their parent species. These studies suggest that genetic-based plant traits affect the distribution of many species and that the variation in hybrids can be used as tools to examine the genetic components of community structure and biodiversity.

  6. Prediction of laser cutting heat affected zone by extreme learning machine

    NASA Astrophysics Data System (ADS)

    Anicic, Obrad; Jović, Srđan; Skrijelj, Hivzo; Nedić, Bogdan

    2017-01-01

    Heat affected zone (HAZ) of the laser cutting process may be developed based on combination of different factors. In this investigation the HAZ forecasting, based on the different laser cutting parameters, was analyzed. The main goal was to predict the HAZ according to three inputs. The purpose of this research was to develop and apply the Extreme Learning Machine (ELM) to predict the HAZ. The ELM results were compared with genetic programming (GP) and artificial neural network (ANN). The reliability of the computational models were accessed based on simulation results and by using several statistical indicators. Based upon simulation results, it was demonstrated that ELM can be utilized effectively in applications of HAZ forecasting.

  7. The use of multiobjective calibration and regional sensitivity analysis in simulating hyporheic exchange

    USGS Publications Warehouse

    Naranjo, Ramon C.; Niswonger, Richard G.; Stone, Mark; Davis, Clinton; McKay, Alan

    2012-01-01

    We describe an approach for calibrating a two-dimensional (2-D) flow model of hyporheic exchange using observations of temperature and pressure to estimate hydraulic and thermal properties. A longitudinal 2-D heat and flow model was constructed for a riffle-pool sequence to simulate flow paths and flux rates for variable discharge conditions. A uniform random sampling approach was used to examine the solution space and identify optimal values at local and regional scales. We used a regional sensitivity analysis to examine the effects of parameter correlation and nonuniqueness commonly encountered in multidimensional modeling. The results from this study demonstrate the ability to estimate hydraulic and thermal parameters using measurements of temperature and pressure to simulate exchange and flow paths. Examination of the local parameter space provides the potential for refinement of zones that are used to represent sediment heterogeneity within the model. The results indicate vertical hydraulic conductivity was not identifiable solely using pressure observations; however, a distinct minimum was identified using temperature observations. The measured temperature and pressure and estimated vertical hydraulic conductivity values indicate the presence of a discontinuous low-permeability deposit that limits the vertical penetration of seepage beneath the riffle, whereas there is a much greater exchange where the low-permeability deposit is absent. Using both temperature and pressure to constrain the parameter estimation process provides the lowest overall root-mean-square error as compared to using solely temperature or pressure observations. This study demonstrates the benefits of combining continuous temperature and pressure for simulating hyporheic exchange and flow in a riffle-pool sequence. Copyright 2012 by the American Geophysical Union.

  8. Root-zone acidity affects relative uptake of nitrate and ammonium from mixed nitrogen sources

    NASA Technical Reports Server (NTRS)

    Vessey, J. K.; Henry, L. T.; Chaillou, S.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

    1990-01-01

    Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.

  9. Root-zone acidity affects relative uptake of nitrate and ammonium from mixed nitrogen sources

    NASA Technical Reports Server (NTRS)

    Vessey, J. K.; Henry, L. T.; Chaillou, S.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

    1990-01-01

    Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.

  10. Flavor of oranges as impacted by abscission zone formation for trees affected by huanglongbing disease and Lasiodiploida infection

    USDA-ARS?s Scientific Manuscript database

    Trees affected by Huanglongbing (HLB) exhibit excessive fruit drop, which is exacerbated by secondary infection of the abscission zone by the fungus Lasiodiplodia. ‘Hamlin’ orange trees, both healthy and affected by HLB, Candidatus Liberibacter asiaticus (CLas, determined by Polymerase chain reactio...

  11. Hyporheic Microbial Biofilms as Indicators of Heavy and Rare Earth Metals in the Clark Fork Basin, Montana

    NASA Astrophysics Data System (ADS)

    Barnhart, E. P.; Hornberger, M.; Hwang, C.; Dror, I.; Bouskill, N.; Short, T.; Cain, D.; Fields, M. W.

    2016-12-01

    The ability to effectively monitor the impact of hard rock mining activities on rivers and streams is a growing concern given the large number of active and abandoned mines in the western United States. One such example, the Clark Fork Basin (CFB), western Montana, was extensively mined for copper in the early 20th century: it is now one of largest U.S. EPA superfund sites. Microbial biofilms are at the base of the lotic food chain and may provide a useful biomonitoring tool for the assessment of metal toxicity due to their environmental ubiquity, rapidity of response to environmental perturbation, and importance in determining metal mobility. Hyporheic microbial biofilms from the CFB were sampled in 2014, concurrent with the USGS National Research Programs (NRP) long-term site monitoring of metals in bed sediment and aquatic benthic insects. Integration of the DNA sequencing results from the hyporheic biofilms with the sediment and insect metal concentrations correlated several bacterial phyla with metal contamination. For example, the genus Lysobacter was strongly associated with copper (Cu) bioaccumulation in the aquatic insect Hydropsyche. These results support previous studies identifying Lysobacter as a bacterial genus that is resistant to Cu ions. Our analysis is the first to indicate that specific microorganisms can act as biomarkers of Cu contamination in rivers. Moreover, our work demonstrates that changes at the microbial community level in the hyporheic zone can be coupled to observed perturbations across higher trophic levels. In 2015, extensive remediation occurred at several of the sites sampled in 2014, providing an excellent opportunity to revisit the sites and examine the temporal variability of identified biomarkers and the short-term effectiveness of remediation. In addition, samples were analyzed for rare earth metals, of which little is known, and could provide additional insight into other metals that change the microbial community structure.

  12. Characterization of microstructure, local deformation and microchemistry in Alloy 690 heat-affected zone and stress corrosion cracking in high temperature water

    NASA Astrophysics Data System (ADS)

    Lu, Zhanpeng; Chen, Junjie; Shoji, Tetsuo; Takeda, Yoichi; Yamazaki, Seiya

    2015-10-01

    With increasing the distance from the weld fusion line in an Alloy 690 heat-affected zone, micro-hardness decreases, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Chromium depletion at grain boundaries in the Alloy 690 heat-affected zone is less significant than that in an Alloy 600 heat-affected zone. Alloy 690 heat-affected zone exhibits much higher IGSCC resistance than Alloy 600 heat-affected zone in simulated pressurized water reactor primary water. Heavily cold worked Alloy 690 exhibits localized intergranular stress corrosion cracking. The effects of metallurgical and mechanical properties on stress corrosion cracking in Alloy 690 are discussed.

  13. Hyporheic exchange in mountain rivers II: Effects of channel morphology on mechanics, scales, and rates of exchange

    Treesearch

    John M. Buffington; Daniele Tonina

    2009-01-01

    We propose that the mechanisms driving hyporheic exchange vary systematically with different channel morphologies and associated fluvial processes that occur in mountain basins, providing a framework for examining physical controls on hyporheic environments and their spatial variation across the landscape. Furthermore, the spatial distribution of hyporheic environments...

  14. Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys

    USGS Publications Warehouse

    Gooseff, M.N.; McKnight, Diane M.; Lyons, W.B.; Blum, A.E.

    2002-01-01

    In the McMurdo Dry Valleys, Antarctica, dilute glacial meltwater flows down well-established streambeds to closed basin lakes during the austral summer. During the 6-12 week flow season, a hyporheic zone develops in the saturated sediment adjacent to the streams. Longer Dry Valley streams have higher concentrations of major ions than shorter streams. The longitudinal increases in Si and K suggest that primary weathering contributes to the downstream solute increase. The hypothesis that weathering reactions in the hyporheic zone control stream chemistry was tested by modeling the downstream increase in solute concentration in von Guerard Stream in Taylor Valley. The average rates of solute supplied from these sources over the 5.2 km length of the stream were 6.1 ?? 10-9 mol Si L-1 m-1 and 3.7 ?? 10-9 mol K L-1 m-1, yielding annual dissolved Si loads of 0.02-1.30 tool Si m-2 of watershed land surface. Silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering. Two strategies were evaluated to compute sediment surface area normalized weathering rates. The first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient, dC/dx (constant weathering rate contribution, CRC method); the second uses a transient storage model to simulate dC/dx, representing both hyporheic exchange and chemical weathering (hydrologic exchange, HE method). Geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0.6 ?? 10-12 mol Si m-2 s-1 to 4.5 ?? 10-12 mol Si m-2 s-1 and 0.4 ?? 10-12 mol K m-2 s-1 to 1.9 ?? 10-12 mol K m-2 s-1. These values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer, wetter

  15. Initial Evaluation of the Heat-Affected Zone, Local Embrittlement Phenomenon as it Applies to Nuclear Reactor Vessels

    SciTech Connect

    McCabe, D.E.

    1999-09-01

    The objective of this project was to determine if the local brittle zone (LBZ) problem, encountered in the testing of the heat-affected zone (HAZ) part of welds in offshore platform construction, can also be found in reactor pressure vessel (RPV) welds. Both structures have multipass welds and grain coarsening along the fusion line. Literature was obtained that described the metallurgical evidence and the type of research work performed on offshore structure welds.

  16. Crack growth rates of irradiated austenitic stainless steel weld heat affected zone in BWR environments.

    SciTech Connect

    Chopra, O. K.; Alexandreanu, B.; Gruber, E. E.; Daum, R. S.; Shack, W. J.; Energy Technology

    2006-01-31

    Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure vessels because of their superior fracture toughness. However, exposure to high levels of neutron irradiation for extended periods can exacerbate the corrosion fatigue and stress corrosion cracking (SCC) behavior of these steels by affecting the material microchemistry, material microstructure, and water chemistry. Experimental data are presented on crack growth rates of the heat affected zone (HAZ) in Types 304L and 304 SS weld specimens before and after they were irradiated to a fluence of 5.0 x 10{sup 20} n/cm{sup 2} (E > 1 MeV) ({approx} 0.75 dpa) at {approx}288 C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading in simulated boiling water reactor environments on Type 304L SS HAZ of the H5 weld from the Grand Gulf reactor core shroud and on Type 304 SS HAZ of a laboratory-prepared weld. The effects of material composition, irradiation, and water chemistry on growth rates are discussed.

  17. Hyporheic flow patterns in relation to large river floodplain attributes Journal

    EPA Science Inventory

    Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

  18. Hyporheic flow patterns in relation to large river floodplain attributes Journal

    EPA Science Inventory

    Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

  19. Spatio-temporal variability of hyporheic exchange through a pool-riffle-pool sequence

    Treesearch

    Frank P. Gariglio; Daniele Tonina; Charles H. Luce

    2013-01-01

    Stream water enters and exits the streambed sediment due to hyporheic fluxes, which stem primarily from the interaction between surface water hydraulics and streambed morphology. These fluxes sustain a rich ecotone, whose habitat quality depends on their direction and magnitude. The spatio-temporal variability of hyporheic fluxes is not well understood over several...

  20. 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

  1. Simulation of the weld heat affected zone of a 0.5Cr-Mo-V steel

    SciTech Connect

    Radhakrishnan, B.; Zacharia, T.

    1995-12-01

    By using a Monte Carlo grain growth algorithm and a methodology for obtaining a one-to-one correlation between Monte Carlo and real parameters of grain size and time, the grain structure in the weld heat affected zone of a 0.5 Mo-Cr-V steel has been simulated. The simulations clearly show that the kinetics of grain growth can be retarded by the presence of steep temperature gradients in the weld heat affected zone. Additional pinning, due to the formation of grain boundary liquid near the solidus temperature, has also been simulated. It is shown that in order to accurately predict the observed grain size in the weld heat affected zone of the 0.5Cr-Mo-V steel, the retardation in growth kinetics due to temperature gradients as well as liquid pinning should be considered.

  2. Effects of Hyporheic Exchange Flows on Egg Pocket Water Temperature in Snake River Fall Chinook Salmon Spawning Areas, 2002-2003 Final Report.

    SciTech Connect

    Hanrahan, T.; Geist, D.; Arntzen, C.

    2004-09-01

    The development of the Snake River hydroelectric system has affected fall Chinook salmon smolts by shifting their migration timing to a period (mid- to late-summer) when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River Chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations (e.g., summer flow augmentation) to improve water temperature and flow conditions during the juvenile Chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall Chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated. This report describes research conducted by the Pacific Northwest National Laboratory (PNNL) that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall Chinook salmon spawning areas. This was a pilot-scale study to evaluate these relationships under existing operations of Hells Canyon Dam (i.e., without any prescribed manipulations of river discharge) during the 2002-2003 water year. The project was initiated in the context of examining the potential for improving juvenile Snake River fall Chinook salmon survival by modifying the discharge operations of Hells Canyon Dam. The potential for improved survival would be gained by increasing the rate at which early life history events proceed (i.e., incubation and emergence), thereby allowing smolts to migrate through downstream reservoirs during early- to mid-summer when river conditions are more favorable for survival. PNNL implemented this research project at index sites throughout 160 km of the Hells Canyon Reach (HCR) of the Snake River. The HCR extends from Hells Canyon Dam (river kilometer [rkm] 399

  3. How Hospitable Are Space Weather Affected Habitable Zones? The Role of Ion Escape

    NASA Astrophysics Data System (ADS)

    Airapetian, Vladimir S.; Glocer, Alex; Khazanov, George V.; Loyd, R. O. P.; France, Kevin; Sojka, Jan; Danchi, William C.; Liemohn, Michael W.

    2017-02-01

    Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds of Myr, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri’s terrestrial planet.

  4. Microstructural response to heat affected zone cracking of prewelding heat-treated Inconel 939 superalloy

    SciTech Connect

    Gonzalez, M.A.; Garza, A.

    2011-12-15

    The microstructural response to cracking in the heat-affected zone (HAZ) of a nickel-based IN 939 superalloy after prewelding heat treatments (PWHT) was investigated. The PWHT specimens showed two different microstructures: 1) spherical ordered {gamma} Prime precipitates (357-442 nm), with blocky MC and discreet M{sub 23}C{sub 6} carbides dispersed within the coarse dendrites and in the interdendritic regions; and 2) ordered {gamma} Prime precipitates in 'ogdoadically' diced cube shapes and coarse MC carbides within the dendrites and in the interdendritic regions. After being tungsten inert gas welded (TIG) applying low heat input, welding speed and using a more ductile filler alloy, specimens with microstructures consisting of spherical {gamma} Prime precipitate particles and dispersed discreet MC carbides along the grain boundaries, displayed a considerably improved weldability due to a strong reduction of the intergranular HAZ cracking associated with the liquation microfissuring phenomena. - Highlights: Black-Right-Pointing-Pointer Homogeneous microstructures of {gamma} Prime spheroids and discreet MC carbides of Ni base superalloys through preweld heat treatments. Black-Right-Pointing-Pointer {gamma} Prime spheroids and discreet MC carbides reduce the intergranular HAZ liquation and microfissuring of Nickel base superalloys. Black-Right-Pointing-Pointer Microstructure {gamma} Prime spheroids and discreet blocky type MC carbides, capable to relax the stress generated during weld cooling. Black-Right-Pointing-Pointer Low welding heat input welding speeds and ductile filler alloys reduce the HAZ cracking susceptibility.

  5. Bead tempering effects on flux cored arc welding heat-affected zone hardness

    SciTech Connect

    Kiefer, J.H.

    1994-12-31

    Bead tempering is a technique used to control the maximum heat-affected zone (HAZ) hardness in the base metal. Applications have included pressure vessel repairs, pipeline hot tapping, and structural welding. Although this technique can be effective if closely controlled, its use as standard welding practice is questionable because precise control of bead placement is required. Experimental design software was used to define a test matrix to evaluate the effects of base plate carbon equivalent, heat input, and weld fusion line proximity on HAZ softening of flux cored arc welds. Some quantitative limits have been identified for the application of temperbead techniques. The results showed that tempering increased with base metal carbon equivalent and temperbead cooling time. An empirical formula was developed that is useful for estimating the amount of HAZ hardness reduction from the plate chemistry, welding parameters, and temperbead placement. The formula can determine the welding conditions needed to achieve a desired hardness reduction. Temperbead techniques can be effective for reducing HAZ hardness where very close quality control of the bead placement is possible. however, the use of bead tempering to pass welding procedure qualifications for standard production welding should be avoided because the level of close control is usually not practical.

  6. Effect of welding parameters on the heat-affected zone of AISI409 ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Ranjbarnodeh, Eslam; Hanke, Stefanie; Weiss, Sabine; Fischer, Alfons

    2012-10-01

    One of the main problems during the welding of ferritic stainless steels is severe grain growth within the heat-affected zone (HAZ). In the present study, the microstructural characteristics of tungsten inert gas (TIG) welded AISI409 ferritic stainless steel were investigated by electron backscattered diffraction (EBSD), and the effects of welding parameters on the grain size, local misorientation, and low-angle grain boundaries were studied. A 3-D finite element model (FEM) was developed to predict the effects of welding parameters on the holding time of the HAZ above the critical temperature of grain growth. It is found that the base metal is not fully recrystallized. During the welding, complete recrystallization is followed by severe grain growth. A decrease in the number of low-angle grain boundaries is observed within the HAZ. FEM results show that the final state of residual strains is caused by competition between welding plastic strains and their release by recrystallization. Still, the decisive factor for grain growth is heat input.

  7. A model for heat-affected zone hardness profiles in Al-Li-X alloys

    SciTech Connect

    Rading, G.O.; Berry, J.T.

    1998-09-01

    A model based on reaction kinetics and elemental diffusion is proposed to account for the presence of double inflection in the hardness profiles of the heat-affected zone (HAZ) in weldments of Al-Li-X alloys tested without postweld heat treatment (PWHT). Such profiles are particularly evident when (1) the base metal is in the peak-aged (T8 or T6) temper condition prior to welding; (2) the welding process is a high-heat input process, i.e., gas tungsten arc (GTA), gas metal arc (GMA) or plasma arc (PA) welding; and (3) a filler alloy deficient in lithium (i.e., AA 2319) is used. In the first part of this paper, the theoretical mechanisms are presented. It is proposed that the double inflection appears due to complete or partial reversion of the semi-coherent, plate-like precipitates (i.e., {theta}{prime}, T{sub 1} or S{prime}); coarsening of the plate-like precipitates at constant volume fraction; precipitation of {delta}{prime} as a result of natural aging; and diffusion of lithium from the HAZ into the weld pool due to the concentration gradient between the weld pool and the base metal. In the second part (to be published in next month`s Welding Journal), experimental validation of the model is provided using weldments of the Al-Li-Cu Alloy 2095.

  8. Use of coastal zone color scanner imagery to identify nearshore ocean areas affected by land-based pollutants. Final report

    SciTech Connect

    LaPointe, T.F.; Basta, D.J.

    1981-01-01

    The purpose of the analysis was to use remotely sensed satellite imagery to determine the spatial boundaries of nearshore areas or zones likely to be affected by pollutants from land-based sources, so that data collected on the presence or absence of living marine resources could be combined with information on land-based pollutant discharges in a preliminary relative assessment of potential risk. Ocean zones of impact related to East Coast estuaries and embayments were approximated using reflectance patterns from data transmitted from the Coastal Zone Color Scanner (CZCS) instrument mounted on the NASA Nimbus-7 satellite. Data were transformed from numerical measures of radiance to photographic images suitable for identifying and mapping ocean impact zones through a simple enhancement technique.

  9. Quantifying the impact on hyporheic flow of assuming homogenous hydraulic conductivity distributions within permeameters

    NASA Astrophysics Data System (ADS)

    Stonedahl, S. H.; Cooper, D. G.; Everingham, J. M.; Kraciun, M. K.; Stonedahl, F.

    2012-12-01

    Hydraulic conductivity (K) is an important sediment property related to the speed with which water flows through sediments. It affects hyporheic uptake and residence time distributions, which are critical to assessing solute transport and nutrient depletion in streams. In this study we investigated the effect of millimeter-scale K variability on measurements that use one of the simplest in situ measurement techniques, the falling-head permeameter test. In a laboratory setting vertical K values and their variability were calculated for a variety of sands. We created composite systems by layering these sands and measured their respective K values. Spatial head distributions for these composite systems were modeled using the finite difference capability of MODFLOW with inputs of head levels, boundaries, and known localized K values. These head distributions were then used to calculate the volumetric flux through the column, which was used in the Hvorslev constant-head equation to calculate vertical K values. We found that these simulated system K values reproduced the same qualitative trends as the laboratory measurements, and provided a good quantitative match in some cases. We then used the model to select distinct heterogeneous K distributions (i.e. layered, randomly distributed, and systematically increasing) that have the same simulated system K value. These K distributions were used in a two-dimensional dune/ripple-scale pumping model to approximate hyporheic residence time distributions and provide estimates of the error associated with the assumed homogeneity of the K distributions. The results have direct implications for both field studies where hydraulic conductivity is being measured and also for determining the level of detail that should be included in computational models.inite difference model of the constant-head permeameter

  10. Factors Affecting Motivation and Job Satisfaction of Academic Staff of Universities in South-South Geopolitical Zone of Nigeria

    ERIC Educational Resources Information Center

    Osakwe, Regina N.

    2014-01-01

    This study determined the factors affecting motivation and job satisfaction of non-management academic staff of universities in South-South geopolitical zone of Nigeria. It employed an expost-facto research design. Three research questions and two hypotheses were raised for the study. A sample of four hundred and fifty non-management academic…

  11. Factors affecting the dynamics of the honeybee (Apis mellifera) hybrid zone of South Africa.

    PubMed

    Beekman, M; Allsopp, M H; Wossler, T C; Oldroyd, B P

    2008-01-01

    Hybrid zones are found wherever two populations distinguishable on the basis of heritable characters overlap spatially and temporally and hybridization occurs. If hybrids have lower fitness than the parental types a tension zone may emerge, in which there is a barrier to gene flow between the two parental populations. Here we discuss a hybrid zone between two honeybee subspecies, Apis mellifera capensis and A. m. scutellata and argue that this zone is an example of a tension zone. This tension zone is particularly interesting because A. m. capensis can be a lethal social parasite of A. m. scutellata. However, despite its parasitic potential, A. m. capensis appears to be unable to increase its natural range unassisted. We propose three interlinked mechanisms that could maintain the South African honeybee hybrid zone: (1) low fitness of intercrossed and genetically mixed colonies arising from inadequate regulation of worker reproduction; (2) higher reproductive success of A. m. scutellata via both high dispersal rates into the hybrid zone and increased competitiveness of males, countered by (3) the parasitic nature of A. m. capensis.

  12. Coupled Effects of Hyporheic Flow Structure and Metabolic Pattern on Reach-scale Nutrient Uptake

    NASA Astrophysics Data System (ADS)

    Li, A.; Aubeneau, A. F.; Bolster, D.; Tank, J. L.; Packman, A. I.

    2015-12-01

    Co-injections of conservative tracers and nutrients are commonly used to assess net reach-scale nutrient transformation rates and benthic/hyporheic uptake parameters. However, little information is available on spatial metabolic patterns in the benthic and hyporheic regions. Based on observations from real systems, we used particle tracking simulations to explore the effects of localized metabolism on estimates of reach-scale nutrient uptake rates. Metabolism locally depletes nutrient concentrations relative to conservative tracers, causing their concentration profiles of injected nutrients and conservative tracers to diverge. At slow rates of hyporheic exchange relative to rates of metabolism, overall hyporheic nutrient uptake is limited by delivery from the stream, and effective reach-scale nutrient uptake parameters will be controlled by the hyporheic exchange rate. At high rates of hyporheic exchange relative to rates of metabolism, the injected tracer can propagate beyond regions of high microbial activity, which commonly occur near the streambed surface. In this case, the injected tracer may not adequately capture timescales of nutrient replenishment in the most bioactive regions. Reach-scale nutrients uptake rate increases with increasing heterogeneity in local metabolic patterns, altering the shape of breakthrough curves downstream. More observations of hyporheic rates and metabolic patterns are needed to understand how flow heterogeneity and reaction heterogeneity interact to control nutrient dynamics at reach-scale.

  13. Evaluation of Heat-affected Zone Hydrogen-induced Cracking in High-strength Steels

    NASA Astrophysics Data System (ADS)

    Yue, Xin

    Shipbuilding is heavily reliant on welding as a primary fabrication technique. Any high performance naval steel must also possess good weldability. It is therefore of great practical importance to conduct weldability testing of naval steels. Among various weldability issues of high-strength steels, hydrogen-induced cracking (HIC) in the heat-affected zone (HAZ) following welding is one of the biggest concerns. As a result, in the present work, research was conducted to study the HAZ HIC susceptibility of several naval steels. Since the coarse-grained heat-affected zone (CGHAZ) is generally known to be the most susceptible to HIC in the HAZ region, the continuous cooling transformation (CCT) behavior of the CGHAZ of naval steels HSLA-65, HSLA-100, and HY-100 was investigated. The CGHAZ microstructure over a range of cooling rates was characterized, and corresponding CCT diagrams were constructed. It was found that depending on the cooling rate, martensite, bainite, ferrite and pearlite can form in the CGHAZ of HSLA-65. For HSLA-100 and HY-100, only martensite and bainite formed over the range of cooling rates that were simulated. The constructed CCT diagrams can be used as a reference to select welding parameters to avoid the formation of high-hardness martensite in the CGHAZ, in order to ensure resistance to hydrogen-induced cracking. Implant testing was conducted on the naval steels to evaluate their susceptibility to HAZ HIC. Stress vs. time to failure curves were plotted, and the lower critical stress (LCS), normalized critical stress ratio (NCSR) and embrittlement index (EI) for each steel were determined, which were used to quantitatively compare HIC susceptibility. The CGHAZ microstructure of the naval steels was characterized, and the HIC fracture behavior was studied. Intergranular (IG), quasi-cleavage (QC) and microvoid coalescence (MVC) fracture modes were found to occur in sequence during the crack initiation and propagation process. This was

  14. Integrating hydraulic conductivity with biogeochemical gradients and microbial activity along river-groundwater exchange zones in a subtropical stream

    NASA Astrophysics Data System (ADS)

    Claret, Cécile; Boulton, Andrew J.

    2009-02-01

    The pervious lateral bars (parafluvial zone) and beds (hyporheic zone), where stream water and groundwater exchange, are dynamic sites of hydrological and biological retention. The significance of these biogeochemical ‘hotspots’ to stream and groundwater metabolism is largely controlled by filtration capacity, defined as the extent to which subsurface flowpaths and matrix hydraulic conductivity modify water characteristics. Where hydraulic conductivity is high, gradients in biogeochemistry and microbial activity along subsurface flowpaths were hypothesized to be less marked than where hydraulic conductivity is low. This hypothesis was tested in two riffles and gravel bars in an Australian subtropical stream. At one site, gradients in chemical and microbial variables along flowpaths were associated with reduced hydraulic conductivity, longer water residence time and reduced filtration capacity compared with the second site where filtration capacity was greater and longitudinal biogeochemical trends were dampened. These results imply that factors affecting the sediment matrix in this subtropical stream can alter filtration capacity, interstitial microbial activity and biogeochemical gradients along subsurface flowpaths. This hydroecological approach also indicates potential for a simple field technique to estimate filtration capacity and predict the prevailing hyporheic gradients in microbial activity and biogeochemical processing efficiency, with significant implications for stream ecosystem function.

  15. Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation.

    PubMed

    Stonedahl, Susa H; Roche, Kevin R; Stonedahl, Forrest; Packman, Aaron I

    2015-11-18

    Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

  16. Factors affecting carbon-14 activity of unsaturated zone CO2 and implications for groundwater dating

    NASA Astrophysics Data System (ADS)

    Wood, Cameron; Cook, Peter G.; Harrington, Glenn A.; Meredith, Karina; Kipfer, Rolf

    2014-11-01

    Unsaturated zone processes may influence the carbon-14 (14C) activity of infiltrating groundwater and thus introduce error in derived groundwater residence times. However unsaturated zone 14C activities are rarely measured and there is little understanding of how they may vary spatially in a groundwater basin. In this study we measured 14C activity in unsaturated zone gas at five sites with different watertable depths (8.2-31.5 m) in the arid Ti Tree Basin, central Australia. We observed a relatively uniform decrease in 14C activity of unsaturated zone gas with depth at most sites, with variation in unsaturated zone depths leading to variation in 14C activities directly above the watertable at each site (ranging from 54 to 106 percent Modern Carbon (pMC)). Through modelling we show that the profiles are influenced by CO2 production at different depths from sources with different isotopic ratios, including production of ‘modern' CO2 in the root zone and production of ‘old' CO2 above the watertable. Scenario modelling showed that these processes are independent of recharge when recharge is low (0-10 mm y-1) but that higher recharge rates (>100 mm y-1) result in more advective transport of atmospheric CO2 to the watertable. The variation in 14C above the watertable was more sensitive to watertable depth and shallow and deep CO2 production rates. These findings offer insight into how unsaturated zone 14C activities may vary spatially and provide guidance as to when 14C depletion in unsaturated zone CO2 may become important for groundwater dating, particularly in arid settings.

  17. Soil organic matter and salinity affect copper bioavailability in root zone and uptake by Vicia faba L. plants.

    PubMed

    Matijevic, Lana; Romic, Davor; Romic, Marija

    2014-10-01

    Processes that control the mobility, transformation and toxicity of metals in soil are of special importance in the root-developing zone. For this reason, there is a considerable interest in understanding trace elements (TEs) behavior in soil, emphasising the processes by which plants take them up. Increased root-zone salinity can affect plant TEs uptake and accumulation in plant tissue. Furthermore, copper (Cu) complexation by soil organic matter (SOM) is an effective mechanism of Cu retention in soils, controlling thus its bioavailability. Therefore, a greenhouse pot experiment was conducted to study the effects of soil Cu contamination in a saline environment on faba bean (Vicia faba L.) element uptake. Treatment with NaCl salinity was applied (control, 50 mM NaCl and 100 mM NaCl) on faba bean plants grown in a control and in a soil spiked with Cu (250 and 500 mg kg(-1)). Low and high SOM content trial variants were studied. Cu accumulation occurred in faba bean leaf, pod and seed. Cu contamination affected plant element concentrations in leaves (Na, Ca, Mg, Mn), pod (Zn, Mn) and seed (Mn, Mo, Zn). Root-zone salinity also affected faba bean element concentrations. Furthermore, Cu contamination-salinity and salinity-SOM interactions were significant for pod Cu concentration, suggesting that Cu phytoavailability could be affected by these interactions. Future research will be focused on the mechanisms of Cu translocation in plant and adaptation aspects of abiotic stress.

  18. Study on the Toughness of X100 Pipeline Steel Heat Affected Zone

    NASA Astrophysics Data System (ADS)

    Li, Xueda; Shang, Chengjia; Ma, Xiaoping; Subramanian, S. V.

    Microstructure-property correlation of heat affected zone (HAZ) in X100 longitudinal submerged arc welding (LSAW) real weld joint was studied in this paper. Coarse grained (CG) HAZ and intercritically reheated coarse grained (ICCG) HAZ were characterized by optical microscope (OM), electron backscattered diffraction (EBSD). The microstructure of CGHAZ is mostly composed of granular bainite with low density of high angle boundaries (HAB). Prior austenite grain size is 80μm. In ICCGHAZ, coarse prior austenite grains were decorated by coarse necklacing martensite-austenite (M-A) constituents. Different layers were observed within M-A constituent, which may be martensite and austenite layers. Charpy absorbed energy of two different HAZ regions (ICCGHAZ containing and non-containing regions) was recorded using instrumental Charpy impact test machine. The results showed that the existence of ICCGHAZ resulted in the sharp drop of Charpy absorbed energy from 180J to 50J, while the existence of only CGHAZ could still lead to good toughness. The fracture surface was 60% brittle in the absence of ICCGHAZ, and 100% brittle in the presence of ICCGHAZ in the impact tested samples. The underlying reason is the microstructure of ICCGHAZ consisted of granular bainite and upper bainite with necklace-type M-A constituent along the grain boundaries. Cleavage fracture initiated from M-A constituent, either through cracking of M-A or debonding from the matrix, was observed at the fracture surface of ICCGHAZ. The presence of necklace type M-A constituent in ICCGHAZ notably increases the susceptibility of cleavage microcrack nucleation. Furthermore, the study of secondary microcracks beneath the CGHAZ and the ICCGHAZ through EBSD suggested that the fracture mechanism changes from nucleation-controlled in the CGHAZ to propagation-controlled in the ICCGHAZ because of the presence of necklace-type M-A constituent in the ICCGHAZ region. Both fracture mechanism contribute to the poor

  19. Inverse Thermal Analysis of Ti-6Al-4V Laser Welds Using Solidification and Heat-Affected Zone Boundaries

    NASA Astrophysics Data System (ADS)

    Lambrakos, S. G.

    2017-03-01

    Temperature histories of Ti-6Al-4V laser welds are presented, which are calculated using numerical-analytical basis functions and boundary constraints based on measured solidification and heat-affected zone cross sections. These weld temperature histories can be adopted as input data to various types of computational procedures, which include numerical models for prediction of solid-state phase transformations and mechanical response. In addition, these temperature histories can be used parametrically for inverse thermal analysis of welds corresponding to other welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that uses three-dimensional constraint conditions whose two-dimensional projections are mapped within transverse cross sections of experimentally measured solidification and heat-affected zone boundaries.

  20. Inverse Thermal Analysis of Ti-6Al-4V Laser Welds Using Solidification and Heat-Affected Zone Boundaries

    NASA Astrophysics Data System (ADS)

    Lambrakos, S. G.

    2017-02-01

    Temperature histories of Ti-6Al-4V laser welds are presented, which are calculated using numerical-analytical basis functions and boundary constraints based on measured solidification and heat-affected zone cross sections. These weld temperature histories can be adopted as input data to various types of computational procedures, which include numerical models for prediction of solid-state phase transformations and mechanical response. In addition, these temperature histories can be used parametrically for inverse thermal analysis of welds corresponding to other welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that uses three-dimensional constraint conditions whose two-dimensional projections are mapped within transverse cross sections of experimentally measured solidification and heat-affected zone boundaries.

  1. Numerical simulation of friction stir welding (FSW): Prediction of the heat affect zone using a softening model

    NASA Astrophysics Data System (ADS)

    Paulo, R. M. F.; Carlone, P.; Valente, R. A. F.; Teixeira-Dias, F.; Palazzo, G. S.

    2016-10-01

    In this work a numerical model is proposed to simulate Friction Stir Welding (FSW) process in AA2024-T3 plates. This model included a softening model that account for the temperature history and the hardness distribution on a welded plate can thus be predicted. The validation of the model was performed using experimental measurements of the hardness in the plate cross-section. There is an acceptable prediction of the material softening in the Heat Affected Zone (HAZ) using the adopted model.

  2. Prediction of the Properties of Heat-Affected Zone of Welded Joints of Sheets from Aluminum Alloys with Structured Surface

    NASA Astrophysics Data System (ADS)

    Mikhailov, V. G.

    2016-05-01

    Welded joints of light structured sheets from aluminum alloy EN AW-6181-T4 (DIN EN 515) of the Al - Si - Mg system are studied. The welding is performed in an argon environment with a short arc by the method of cold metal transfer (CMT®). The results of the study are used in an amended Leblond model for describing the variation of the properties of the heat-affected zone of welded joints of structured sheets.

  3. Interpreting lateral 2-D bank hyporheic flux based on GA-VS2DH

    NASA Astrophysics Data System (ADS)

    Su, Xiaoru; Shu, Longcang; Wen, Zhonghui; Lu, Chengpeng; Eshete, Abunu

    2015-04-01

    Hyporheic flux is of great significance for evaluating water resources and protecting ecosystem health. Heat as a tracer was widely used in recognizing the hyporheic flux with high precision, low cost and great convenience. The hyporheic flux in bank cross-section occurs in vertical and lateral directions. In order to depict the hyporheic flow path and its spatial distribution in bank area, a GA-VS2DH nested loop method was developed based on Microsoft Visual Basic 6.0. VS2DH was applied to model 2-D bank hyporheic flow and GA was used to calibrate the model automatically by minimizing the difference between observed and simulated temperatures of sediments in bank area. A hypothetic model was developed to assess the reliability of GA-VS2DH in simulating hyporheic flux and parameters estimation in river bank system. Some numerical experiments were conducted to recognize the capability of GA-VS2DH. Then the GA-VS2DH was applied in two field sites with river bank sediments made by sand and clay, respectively, to verify the reliability of the method. The results indicated that the simulated hyporheic flux and parameters of GA-VS2DH were reliable. GA-VS2DH could be applied in interpreting lateral 2-D bank hyporheic flux. Hydraulic conductivity (K) and dispersivity (D) are the two most sensitive parameters and the estimates of these two parameters have more reliability than the others. The estimates of hydraulic conductivity at Dawen River site and Qinhuai River site are 1.293 and 0.019 m/d, respectively, which corresponded to sand and clay sediment in the two sites.

  4. Characterization of hole circularity and heat affected zone in pulsed CO2 laser drilling of alumina ceramics

    NASA Astrophysics Data System (ADS)

    Bharatish, A.; Narasimha Murthy, H. N.; Anand, B.; Madhusoodana, C. D.; Praveena, G. S.; Krishna, M.

    2013-12-01

    Circularity of drilled hole at the entry and exit, heat affected zone and taper are important attributes which influence the quality of a drilled hole in laser drilling. This paper examines the effect of laser parameters on the quality of drilled holes in Alumina ceramics which are widely used in microelectronic devices, based on orthogonal array experimentation and response surface methodology. Both entrance and exit circularities were significantly influenced by hole diameter and laser power. Heat affected zone was influenced by frequency. Taper was also significantly influenced by laser power. Response surface model predicted nominal entrance circularity at 2.5 kHz, 240 W, 2.5 mm/s, 1 mm hole, exit circularity and taper at 7.5 kHz, 240 W, 4.5 mm/s, and 1 mm hole. The model predicted lowest heat affected zone at 7.5 kHz, 240 W, 2.5 mm/s, and 1 mm. Multiobjective optimization achieved using both response surface model and gray relational analysis indicated that all the four quality parameters are optimized at 7.5 kHz, 240 W, 3.85 mm/s and 1 mm.

  5. Factors affecting surf zone phytoplankton production in Southeastern North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Cahoon, Lawrence B.; Bugica, Kalman; Wooster, Michael K.; Dickens, Amanda Kahn

    2017-09-01

    The biomass and productivity of primary producers in the surf zone of the ocean beach at Wrightsville Beach, North Carolina, USA, were measured during all seasons, along with environmental parameters and nutrient levels. Variation in biomass (chlorophyll a) was associated with temperature. Primary production (PP), measured by in situ 14-C incubations, was a function of chlorophyll a, tide height at the start of incubations, and rainfall in the preceding 24-hr period. Biomass-normalized production (PB) was also a function of tide height and rainfall in the preceding 24-hr period. We interpreted these results as evidence of surf production 1) as combined contributions of phytoplankton and suspended benthic microalgae, which may confound application of simple P-E models to surf zone production, and 2) being regulated by nutrient source/supply fluctuations independently from other factors. Surf zone biomass and production levels are intermediate between relatively high estuarine values and much lower coastal ocean values. Surf zone production may represent an important trophic connection between these two important ecosystems.

  6. Streamside Management Zones Affect Movement of Silvicultural Nitrogen and Phosphorus Fertilizers to Piedmont Streams

    Treesearch

    Joseph M. Secoges; Wallace M. Aust; John R. Seiler; C. Andrew Dolloff; William A. Lakel

    2013-01-01

    Forestry best management practices (BMP) recommendations for streamside management zones (SMZs) are based on limited data regarding SMZ width, partial harvests, and nutrient movements after forest fertilization. Agricultural fertilization is commonly linked to increased stream nutrients. However, less is known about effectiveness of SMZ options for controlling nutrient...

  7. The Affective Establishment and Maintenance of Vygotsky's Zone of Proximal Development

    ERIC Educational Resources Information Center

    Levykh, Michael G.

    2008-01-01

    Many recent articles, research papers, and conference presentations about Lev Vygotsky's zone of proximal development (ZPD) emphasize the "extended" version of the ZPD that reflects human emotions and desires. In this essay, Michael G. Levykh expands on the extant literature on the ZPD through developing several new ideas. First, he maintains that…

  8. Root-zone temperature and water availability affect early root growth of planted longleaf pine

    Treesearch

    M.A. Sword

    1995-01-01

    Longleaf pine seedlings from three seed sources were exposed to three root-zone temperatures and three levels of water availability for 28 days. Root growth declined as temperature and water availability decreased. Root growth differed by seed source. Results suggest that subtle changes in the regeneration environment may influence early root growth of longleaf pine...

  9. Interactions between hyporheic flow produced by stream meanders, bars, and dunes

    USGS Publications Warehouse

    Stonedahl, Susa H.; Harvey, Judson W.; Packman, Aaron I.

    2013-01-01

    Stream channel morphology from grain-scale roughness to large meanders drives hyporheic exchange flow. In practice, it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers. As a result, many studies only characterize isolated exchange processes at a single spatial scale. In this work, we simulated hyporheic flows induced by a range of geomorphic features including meanders, bars and dunes in sand bed streams. Twenty cases were examined with 5 degrees of river meandering. Each meandering river model was run initially without any small topographic features. Models were run again after superimposing only bars and then only dunes, and then run a final time after including all scales of topographic features. This allowed us to investigate the relative importance and interactions between flows induced by different scales of topography. We found that dunes typically contributed more to hyporheic exchange than bars and meanders. Furthermore, our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to, but not linearly additive. These findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers.

  10. Effects of stream discharge, alluvial depth and bar amplitude on hyporheic flow in pool-riffle channels

    NASA Astrophysics Data System (ADS)

    Tonina, Daniele; Buffington, John M.

    2011-08-01

    Hyporheic flow results from the interaction between streamflow and channel morphology and is an important component of stream ecosystems because it enhances water and solute exchange between the river and its bed. Hyporheic flow in pool-riffle channels is particularly complex because of three-dimensional topography that spans a range of partially to fully submerged conditions, inducing both static and dynamic head variations. Hence, these channels exhibit transitional conditions of streambed pressure and hyporheic flow compared to previous studies of fully submerged, two-dimensional bed forms. Here, we conduct a series of three-dimensional simulations to investigate the effects of bed topography, depth of alluvium, and stream discharge on hyporheic flow in pool-riffle reaches with variable bed form submergence, and we propose three empirical formulae to predict the mean depth of hyporheic exchange and characteristic values of the residence time distribution (mean and standard deviation). Hyporheic exchange is predicted with a three-dimensional pumping model, and hyporheic flow is modeled as a Darcy flow. We find that the hyporheic residence time is well approximated by a lognormal distribution for both partially and entirely submerged pool-riffle topography, with the parameters of the distribution defined by the mean and variance of the log-transformed residence time. Depth of alluvium has a substantial effect on hyporheic flow when alluvial depth is less than a third of the bed form wavelength for the conditions examined.

  11. Fundamental Studies of Phase Transformations and Mechanical Properties in the Heat Affected Zone of 10 wt% Nickel Steel

    NASA Astrophysics Data System (ADS)

    Barrick, Erin J.

    United States naval applications require the use of steels with high strength and resistance to fracture at low temperatures to provide good ballistic properties. In recent years, 10 wt% Ni steel has been developed with strength and toughness values exceeding those of steels currently used, and is now being considered as a candidate material to replace existing high-strength, low alloy steels. This steel has excellent toughness from the mechanically induced transformation of interlath austenite films to martensite. These austenite films are formed via a carefully developed quenching, lamellarizing, and tempering heat treatment. However, before 10 wt% Ni steel can be implemented for full-scale applications, the effects of the rapid heating and cooling rates associated with welding thermal cycles on phase transformations and mechanical properties must be understood. In this research, a fundamental understanding of phase transformations and mechanical properties in the heat-affected zone of fusion welds in 10 wt% Ni steel was developed through heating and cooling rate dilatometry experiments, gas tungsten arc welding, and simulation of gas metal arc welding. First, an investigation into the effects of heating and cooling rate on the phase transformations in 10 wt% Ni steel was performed. The Ac1 and Ac3 temperatures during heating were determined as a function of heating rate, and sluggish transformation during fast heating rates manifested itself as a high Ac3 temperature of 1050°C as opposed to a temperature of 850°C at slow heating rates. A continuous cooling transformation diagram produced for 10 wt% Ni steel reveals that martensite will form over a very wide range of cooling rates, which reflects a very high hardenability of this alloy. This is significant because the range of cooling rates for which the diagram was constructed over easily covers the range associated with fusion welding, so there would not be the need for precise control over the weld

  12. Visualization of microcrack anisotropy in granite affected by afault zone, using confocal laser scanning microscope

    SciTech Connect

    Onishi, Celia T.; Shimizu, Ichiko

    2004-01-02

    Brittle deformation in granite can generate a fracture system with different patterns. Detailed fracture analyses at both macroscopic and microscopic scales, together with physical property data from a drill-core, are used to classify the effects of reverse fault deformation in four domains: (1) undeformed granite, (2) fractured granite with cataclastic seams, (3) fractured granite from the damage zone, and (4) foliated cataclasite from the core of the fault. Intact samples from two orthogonal directions, horizontal (H) and vertical (V), from the four domains indicate a developing fracture anisotropy toward the fault, which is highly developed in the damage zone. As a specific illustration of this phenomenon, resin impregnation, using a confocal laser scanning microscope (CLSM) technique is applied to visualize the fracture anisotropy developed in the Toki Granite, Japan. As a result, microcrack networks have been observed to develop in H sections and elongate open cracks in V sections, suggesting that flow pathways can be determined by deformation.

  13. Hydrogen-induced cold cracking in heat-affected zone of low-carbon high-strength steel

    NASA Astrophysics Data System (ADS)

    Lan, Liangyun; Kong, Xiangwei; Hu, Zhiyong; Qiu, Chunlin

    2014-12-01

    The Y-groove cracking test by submerged arc welding was employed to study the susceptibility of a low-carbon high-strength steel to hydrogen-induced cold cracking (HICC). The morphology of hydrogen cracks was observed using an electron probe microscope. The results showed that the heat-affected zone (HAZ) has a higher susceptibility to HICC than the weld metal and that increasing heat input can improve the HICC resistance of the weldment. The intergranular microcracking is the main HICC mode at the lowest heat input condition, accompanied with some transgranular microcracks attached to complex inclusions. In combination with phase transformation behaviour in sub-zones, the effect of the phase transformation sequence is proposed to try to illustrate the fact that the fine-grained HAZ has higher probability of hydrogen cracking than the coarse-grained HAZ owing to the occurrence of hydrogen enrichment in the fine-grained HAZ after the transformation.

  14. The study on microstructural and mechanical properties of weld heat affected zone of 7075-T651 aluminum alloy

    SciTech Connect

    Hwang, R.Y.; Chou, C.P.

    1997-12-22

    Aluminum alloys play an important role in aerospace industry due to their high strength and low density. The general accepted precipitation behavior of 7075 alloy was represented as: supersaturated solid solution {alpha}{sub ss} {yields} Gp zones {yields} {eta}{prime}(MgZn{sub 2}) {yields} {eta}(MgZn{sub 2}). The Addition of Cu in Al-Zn-Mg alloy would promote the transformation of GP zones into {eta}{prime}(MgZn{sub 2}) phase and stabilize the {eta}(MgZn{sub 2}) phase. The T6 temper has the maximum strength but lower ductility. The T73 temper may lose some strength, but can gain higher corrosion resistance and lower susceptibility to stress corrosion cracking as compared to the T6 temper. The welding fabrication can produce thermal cycling on the weldment. In the heat affected zone (HAZ) beside the fusion zone, different temperatures can be obtained. This would cause change of microstructure in the HAZ of aluminum alloy weldment. Many workers studied the behavior of weld HAZ by cutting the HAZ into many small pieces or using short time isothermal heat treatment to simulate the HAZ. This may lose some information, especially near the fusion zone, because high temperature gradient occurred in this region. In this study, the Gleeble system was used to simulate the weld HAZ. It can accurately simulate every point of weld HAZ by heating and cooling the specimen to the thermal history of weld HAZ as the same as measured. The microstructural and mechanical properties of weld HAZ of 7075-T651 alloy were investigated.

  15. An investigation of reheat cracking in the weld heat affected zone of type 347 stainless steel

    NASA Astrophysics Data System (ADS)

    Phung-On, Isaratat

    2007-12-01

    microvoid corresponds to the size of precipitate that forms. In addition, there was intragranular cracking in some location indicating that another failure mechanism may also be possible. It was believed that failure may occur along a precipitate free zone. However, the distinct PFZ could not be detected. A SS-DTA technique was also implemented in order to determine precipitation temperatures of the material. The results showed the possible precipitation temperatures in the range of 850°C to 650°C. However, the results were not confidently reliable due to the small amount of carbide formed that affects the sensitivity of the SS-DTA. A simple grain boundary sliding model was generated proposing that the sliding is operated by the shear stress resulting from the formation of precipitate in the grain interior. Then, the sliding results in the microvoid formation and coalescence followed by cracking. In addition, a simple finite element model was generated to provide the illustration of the shear stress built up by the formation of precipitate. The model showed that shear stress can cause the grain boundary movement/sliding. Based on the results from this study, the recommendation for the selection of post weld heat treatment schedule as well as welding procedures can be determined for the prevention of the reheat cracking. A residual stress should be kept below the critical value during welding and post weld heat treating. The testing procedures used in this study can be applied as the guidelines to conduct the reheat cracking susceptibility test for material selection.

  16. Carbon and Nitrogen Response to Forced Inundation of Hyporheic Sediment along an Elevational Transect of the Columbia River

    NASA Astrophysics Data System (ADS)

    Goldman, A. E.; Graham, E.; Crump, A.; Kennedy, D.; Romero, E. B.; Anderson, C.; Dana, K. L.; Fredrickson, J.; Stegen, J.

    2016-12-01

    Diel and seasonal fluctuations of river water discharge in the dam-controlled Hanford Reach of the Columbia River (Washington State, USA) result in irregular wetting and drying of hyporheic sediments within ten meters of the shoreline. As such, nearshore inundation histories vary from seconds to years since last river water exposure and have generated a gradient in groundcover ranging from barren gravel to sparse grasses to trees. In order to understand how history of inundation influences the response of carbon and nitrogen cycling to rewetting, we conducted 0.5-hour and 25-hour forced-inundation laboratory incubations on samples collected every two meters along three 6-meter elevational transects of shoreline along the Hanford Reach. At the time of sample collection, sediment along our elevational transect ranged from currently inundated to one year since last inundation. Incubation sediments were characterized based on spatial and temporal changes in nitrogen and carbon characteristics. We measured headspace CO2, non-particulate organic carbon (NPOC), total organic matter, organic acids, C/N, NO3-, NO2-, NH4+, pH, and moisture content. We found high rates of aerobic respiration at the lowest elevations, attributed to an initial pulse of CO2 not seen at higher elevations, and accumulation of labile organic carbon (i.e., glucose, NPOC) at the highest elevations. We are currently investigating microbial communities with 16S and ITS sequencing in order to explore potential community shifts along the transect and linkages between fungal communities and nitrogen cycling. Our results suggest that inundation history may lead to spatial isolation of microbial communities with subsequent differences in ability to respond to wet-dry cycles. Examining how variations in hydrology impact carbon and nitrogen cycling allows for a more robust understanding of how climate change may alter microbially-mediated interactions and transformations within the hyporheic zone.

  17. Interaction of Physical and Chemical Processes Controlling the Environmental Fate and Transport of Lampricides Through Stream-Hyporheic Systems

    NASA Astrophysics Data System (ADS)

    Hixson, J.; Ward, A. S.; Schmadel, N.; McConville, M.; Remucal, C.

    2016-12-01

    The transport and fate of contaminants of emerging concern through the environment is complicated by the heterogeneity of natural systems and the unique reaction pathways of individual compounds. Our current evaluation of risk is often simplified to controls assumed to be homogeneous in space and time. However, we know spatial heterogeneity and time-variable reaction rates complicate predictions of environmental transport and fate, and therefore risk. These complications are the result of the interactions between the physical and chemical systems and the time-variable equilibrium that exists between the two. Compounds that interact with both systems, such as photolytic compounds, require that both components are fully understood in order to predict transport and fate. Release of photolytic compounds occurs through both unintentional releases and intentional loadings. Evaluating risks associated with unintentional releases and implementing best management practices for intentional releases requires an in-depth understanding of the sensitivity of photolytic compounds to external controls. Lampricides, such as 3-trifluoromethyl-4-nitrophenol (TFM), are broadly applied in the Great Lakes system to control the population of invasive sea lamprey. Over-dosing can yield fish kills and other detrimental impacts. Still, planning accounts for time of passage and dilution, but not the interaction of the physical and chemical systems (i.e., storage in the hyporheic zone and time-variable decay rates). In this study, we model a series of TFM applications to test the efficacy of dosing as a function of system characteristics. Overall, our results demonstrate the complexity associated with photo-sensitive compounds through stream-hyporheic systems, and highlight the need to better understand how physical and chemical systems interact to control transport and fate in the environment.

  18. Heat tracing to determine spatial patterns of hyporheic exchange across a river transect

    NASA Astrophysics Data System (ADS)

    Lu, Chengpeng; Chen, Shuai; Zhang, Ying; Su, Xiaoru; Chen, Guohao

    2017-09-01

    Significant spatial variability of water fluxes may exist at the water-sediment interface in river channels and has great influence on a variety of water issues. Understanding the complicated flow systems controlling the flux exchanges along an entire river is often limited due to averaging of parameters or the small number of discrete point measurements usually used. This study investigated the spatial pattern of the hyporheic flux exchange across a river transect in China, using the heat tracing approach. This was done with measurements of temperature at high spatial resolution during a 64-h monitoring period and using the data to identify the spatial pattern of the hyporheic exchange flux with the aid of a one-dimensional conduction-advection-dispersion model (VFLUX). The threshold of neutral exchange was considered as 126 L m-2 d-1 in this study and the heat tracing results showed that the change patterns of vertical hyporheic flux varied with buried depth along the river transect; however, the hyporheic flux was not simply controlled by the streambed hydraulic conductivity and water depth in the river transect. Also, lateral flow dominated the hyporheic process within the shallow high-permeability streambed, while the vertical flow was dominant in the deep low-permeability streambed. The spatial pattern of hyporheic exchange across the river transect was naturally controlled by the heterogeneity of the streambed and the bedform of the stream cross-section. Consequently, a two-dimensional conceptual illustration of the hyporheic process across the river transect is proposed, which could be applicable to river transects of similar conditions.

  19. Heat tracing to determine spatial patterns of hyporheic exchange across a river transect

    NASA Astrophysics Data System (ADS)

    Lu, Chengpeng; Chen, Shuai; Zhang, Ying; Su, Xiaoru; Chen, Guohao

    2017-03-01

    Significant spatial variability of water fluxes may exist at the water-sediment interface in river channels and has great influence on a variety of water issues. Understanding the complicated flow systems controlling the flux exchanges along an entire river is often limited due to averaging of parameters or the small number of discrete point measurements usually used. This study investigated the spatial pattern of the hyporheic flux exchange across a river transect in China, using the heat tracing approach. This was done with measurements of temperature at high spatial resolution during a 64-h monitoring period and using the data to identify the spatial pattern of the hyporheic exchange flux with the aid of a one-dimensional conduction-advection-dispersion model (VFLUX). The threshold of neutral exchange was considered as 126 L m-2 d-1 in this study and the heat tracing results showed that the change patterns of vertical hyporheic flux varied with buried depth along the river transect; however, the hyporheic flux was not simply controlled by the streambed hydraulic conductivity and water depth in the river transect. Also, lateral flow dominated the hyporheic process within the shallow high-permeability streambed, while the vertical flow was dominant in the deep low-permeability streambed. The spatial pattern of hyporheic exchange across the river transect was naturally controlled by the heterogeneity of the streambed and the bedform of the stream cross-section. Consequently, a two-dimensional conceptual illustration of the hyporheic process across the river transect is proposed, which could be applicable to river transects of similar conditions.

  20. Hyporheic Geophysics: D.C. Resistivity Imaging of Valley-bottom Alluvium in a 3rd-order Mountain Stream, HJ Andrews Experimental Forest, Oregon, USA

    NASA Astrophysics Data System (ADS)

    Zarnetske, J. P.; Haggerty, R.; Crook, N.; Robinson, D. A.

    2006-12-01

    The hyporheic zone (HZ) can serve as either a source or a sink for nutrients (e.g., nitrogen) and moderates biogeochemical and temperature signals in stream ecosystems. Understanding of the HZ is hampered by lack of subsurface images, particularly ones that are non-invasive and fast. Geophysical imaging, combined with extant empirical methods and hydrodynamic models provides an opportunity to improve precision in modeling HZ transport and nutrient retention. With the aid of CUAHSI HMF, we completed a d.c. resistivity survey of an existing stream denitrification study site (Mack Creek, H.J. Andrews Experimental Forest, OR, a Long-term Ecological Research site) to quantify the geometry of the valley bottom alluvial aquifer and HZ. The non- invasive d.c. resistivity survey successfully produced a quantitative 3-dimensional image of the variable alluvial aquifer thickness below and adjacent to the stream channel. We extensively imaged one area, 50 m x 28 m with 10 transects, in an old growth Douglas fir (Pseudotsuga menziesii) stand which incorporated a large woody debris log jam, to determine that alluvial thickness averages 4.1 m and varies between 0 m and 8 m. We completed a single 50 m longitudinal section in an adjacent downstream logged block (harvested 1964-65) to determine that alluvial thickness averages 0.3 m and varies between 0 m and 1 m. The presence of valley- bottom bedrock exposures at the study site helped to constrain and verify the d.c. resistivity interpretation of the bedrock-alluvium interface. Some d.c. survey challenges were encountered, including the confinement of electrode lines to the channel or near channel because dry organic layers or fallen trees across much of the forest floor prevented good electrode contact with the ground. Ultimately, this geophysics-enhanced knowledge of the stream-adjacent aquifer will allow for more accurate interpretation of hyporheic observations and parameterization of hyporheic hydraulic and denitrification

  1. Carbon and nitrogen mobilization along thermokarst-affected permafrost coasts and its degradation mechanisms before entering the near shore zone

    NASA Astrophysics Data System (ADS)

    Tanski, G.; Ruttor, S.; Lantuit, H.; Knoblauch, C.; Strauss, J.; Radosavljevic, B.; Ramage, J. L.; Fritz, M.

    2016-12-01

    The Arctic is more than any other region on Earth affected by changing climate conditions. Ice-rich and unlithified permafrost coasts are particularly susceptible for these changes. These coasts erode at a great pace, which is facilitated by thermokarst processes and wave action due to longer open water periods. Organic matter that has been frozen for millennia is mobilized and can be either emitted as greenhouse gases to the atmosphere, redeposited on the land surface, or transported into the nearshore zone of the ocean. However, only little is known about the degradation processes after mobilization from permafrost until entering the aquatic system. It is the aim of this study to capture the degradation dynamics of organic carbon and nitrogen at the land-ocean-interface before entering nearshore zone, where it can potentially affect marine chemistry and ecosystems. In this study we investigated a retrogressive thaw slump, a thermokarst feature that is abundant along the ice-rich permafrost coast of the Canadian Arctic. Samples have been taken systematically along transects in undisturbed, i.e. not affected by thermokarst yet (tundra, permafrost headwall), and disturbed areas (mudpool, slump deposits, thaw stream). Total and dissolved organic carbon (TOC and DOC) as well as total and dissolved nitrogen (TN and DN) were analyzed to estimate the loss from undisturbed to disturbed areas. Stable carbon isotopes, C/N-ratios, inorganic nutrients, and lipid biomarkers have been analyzed to determine potential degradation processes. The results show no substantial changes of stable carbon isotopes and C/N-ratios (for TOC). However, high concentrations of ammonium in the mudpool (fresh thawed material) and low C/N-rations (for DOC) within the thaw stream indicate rapid metabolization of organic material. In conclusion we show that organic carbon and nutrients undergo substantial changes upon thaw and are subject to degradation before entering the nearshore zone.

  2. Control of Softening Processes in the Heat-Affected Zone During Welding of High-Strength Steels

    NASA Astrophysics Data System (ADS)

    Efimenko, L. A.; Kapustin, O. E.; Ramus', A. A.; Ramus', R. O.

    2016-11-01

    The hardness and the structure of the heat-affected zone (HAZ) under welding of tube steels of strength category K60 - K70 are studied. The steels are treated by regimes imitating the thermal cycles of different welding processes applied to tubes starting with manual arc welding and ending with energy-intensive automatic submerged-arc welding. The welding modes causing maximum decrease in the hardness of HAZ regions are determined. The conditions preventing softening under one-pass and multipass welding of high-strength steels are presented.

  3. Antimony-induced embrittlement in welding heat-affected zones in a Cr-Mo low-alloy steel

    NASA Astrophysics Data System (ADS)

    Zheng, L.; Song, S.-H.

    2013-07-01

    Heat-affected zones (HAZs) were simulated with a peak temperature of 1320 °C at different welding heat inputs for a Cr-Mo low-alloy steel. The ductile-to-brittle transition temperature (DBTT) of the HAZs increased with increasing heat input. When 0.05 wt.% Sb was added to the steel, the DBTTs of the HAZs became 1 and 10 °C higher than those for the undoped steel at heat inputs of 36 and 60 kJ/cm, respectively. Sb segregation to austenite grain boundaries during thermal cycling was found to be mainly responsible for the DBTT increase.

  4. Spatially distributed characterization of hyporheic solute transport during baseflow recession in a headwater mountain stream using electrical geophysical imaging

    Treesearch

    Adam S. Ward; Michael N. Gooseff; Michael Fitzgerald; Thomas J. Voltz; Kamini Singha

    2014-01-01

    The transport of solutes along hyporheic flowpaths is recognized as central to numerous biogeochemical cycles, yet our understanding of how this transport changes with baseflow recession, particularly in a spatially distributed manner, is limited. We conducted four steady-state solute tracer injections and collected electrical resistivity data to characterize hyporheic...

  5. Effects of stream discharge, alluvial depth and bar amplitude on hyporheic flow in pool-riffle channels

    Treesearch

    Daniele Tonina; John M. Buffington

    2011-01-0