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1

Hydraulic Properties of Unsaturated Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Many agrophysical applications require knowledge of the hydraulic properties of unsaturated soils. These properties reflect the ability of a soil to retain or transmit water and its dissolved constituents. The objective of this work was to develop an entry for the Encyclopedia of Agrophysics that w...

2

BOREAS HYD-1 Soil Hydraulic Properties  

NASA Technical Reports Server (NTRS)

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-1 team coordinated a program of data collection to measure and monitor soil properties in collaboration with other science team measurement needs. This data set contains soil hydraulic properties determined at the Northern Study Area (NSA) and Southern Study Area (SSA) flux tower sites based on analysis of in situ tension infiltrometer tests and laboratory-determined water retention from soil cores collected during the 1994-95 field campaigns. Results from this analysis are saturated hydraulic conductivity, and fitting parameters for the van Genuchten-Mualem soil hydraulic conductivity and water retention function at flux tower sites. The data are contained in tabular ASCII files. The HYD-01 soil hydraulic properties data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Hall, Forrest G. (Editor); Knapp, David E. (Editor); Kelly, Shaun F.; Stangel, David E.; Smith, David E. (Technical Monitor)

2000-01-01

3

Microbial effect on soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Although largely ignored, the soil contains large amount of biofilms (attached microbes) that can affect many processes. While biochemical processes are studied, biophysical processes receive only little attention. Biofilms may occupy some of the pore space, and by that affect the soil hydraulic properties. This effect on unsaturated soils, however, was not intensively studied. In this research we directly measure the hydraulic properties, namely the soil's unsaturated hydraulic conductivity function and retention curve, for soils containing real biofilm. To do that we inoculate soil with biofilm-forming bacteria and incubate it with sufficient amounts of nutrient until biofilm is formed. The hydraulic properties of the incubated soil are then measured using several techniques, including multi-step outflow and evaporation method. The longer measurements (evaporation method) are conducted under refrigeration conditions to minimize microbial activity during the experiment. The results show a clear effect of the biofilm, where the biofilm-affected soil (sandy loam in our case) behaves like a much finer soil. This qualitatively makes sense as the biofilm generates an effective pore size distribution that is characterized by smaller pores. However, the effect is much more complex and needs to be studied carefully considering (for example) dual porosity models. We compare our preliminary results with other experiments, including flow-through column experiments and experiments with biofilm analogues. Clearly a better understanding of the way microbial activity alters the hydraulic properties may help designing more efficient bioremediation, irrigation, and other soil-related processes.

Furman, Alex; Rosenzweig, Ravid; Volk, Elazar; Rosenkranz, Hella; Iden, Sascha; Durner, Wolfgang

2014-05-01

4

Scaling hydraulic properties of a macroporous soil Binayak P. Mohanty  

E-print Network

Scaling hydraulic properties of a macroporous soil Binayak P. Mohanty U.S. Salinity Laboratory, Riverside, California Abstract. Macroporous soils exhibit significant differences in their hydraulic properties for different pore domains. Multimodal hydraulic functions may be used to describe

Mohanty, Binayak P.

5

Soil Texture Triangle: Hydraulic Properties Calculator  

NSDL National Science Digital Library

Dr. Keith E. Saxton from Washington State Universities Department of Biological Systems Engineering offers the Soil Texture Triangle-Hydraulic Properties Calculator Web site. By simply entering its percent sand and clay, this online calculator allows users to find the wilting point, field capacity, bulk density, saturation, saturated hydraulic conductivity, and available water of particular soils. A great resource for researchers and professionals, the utility can even be downloaded free of charge to use on your own computer as a MS-DOS program. .

Saxton, Keith E., 1937-

6

Root effects on soil water and hydraulic properties  

Microsoft Academic Search

Plants can affect soil moisture and the soil hydraulic properties both directly by root water uptake and indirectly by modifying\\u000a the soil structure. Furthermore, water in plant roots is mostly neglected when studying soil hydraulic properties. In this\\u000a contribution, we analyze effects of the moisture content inside roots as compared to bulk soil moisture contents and speculate\\u000a on implications of

Horst H. Gerke; Rolf O. Kuchenbuch

2007-01-01

7

Saturated hydraulic conductivity and soil water retention properties across a soil-slope transition  

E-print Network

Saturated hydraulic conductivity and soil water retention properties across a soil-slope transition measured saturated hydraulic conductivity (Ksat) and soil water retention functions at two (15 and 30 cm Area Research and Extension Center, Santa Clara, California Abstract. The hydraulic properties of soil

Mohanty, Binayak P.

8

Effects of Long-term Soil and Crop Management on Soil Hydraulic Properties for Claypan Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Regional and national soil maps and associated databases of soil properties have been developed to help land managers make decisions based on soil characteristics. Hydrologic modelers also utilize soil hydraulic properties provided in these databases, in which soil characterization is based on avera...

9

Empirical equations for some soil hydraulic properties  

Microsoft Academic Search

with a power function relating soil moisture and hydraulic conductivitymis used to derive a formula for the wetting front suction required by the Green-Ampt equation. Representative parameters for the moisture charac- teristic, the wetting front suction, and the sorptivity, a parameter in the infiltration equation derived by Philip (1957), are computed by using the desorption data of Holtan et al.

Roger B. Clapp; George M. Hornberger

1978-01-01

10

USING ENSEMBLE PREDICTIONS TO SIMULATE FIELD-SCALE SOIL WATER TIME SERIES WITH UPSCALED AND DOWNSCALED SOIL HYDRAULIC PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Simulations of soil water flow require measurements of soil hydraulic properties which are particularly difficult at field scale. Laboratory measurements provide hydraulic properties at scales finer than the field scale, whereas pedotransfer functions (PTFs) integrate information on hydraulic prope...

11

FIELD DETERMINATION OF SOIL HYDRAULIC AND CHEMICAL TRANSPORT PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydraulic and chemical transport properties are the major inputs in predictive models that simulate the movement of water and chemicals through the vadose zone. However, there is a lack of field measurements of such properties to verify models describing water and chemical movement through the soil...

12

SOIL HYDRAULIC PROPERTIES INFLUENCED BY STIFF-STEMMED GRASS HEDGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Stiff-stemmed grass hedges planted in narrow rows within a field offer an opportunity for effective erosion control at a reasonable cost. The effectiveness of the hedges, however, may depend on soil hydraulic properties as influenced by a hedge. The objective of this study was to characterize and ...

13

Simplified evaporation method for determining soil hydraulic properties  

NASA Astrophysics Data System (ADS)

SummaryEvaporation experiments are commonly used to derive hydraulic properties of soils. In the simplified evaporation method, as proposed by Schindler [Schindler, U., 1980. Ein Schnellverfahren zur Messung der Wasserleitfähigkeit im teilgesättigten Boden an Stechzylinderproben. Arch. Acker- u. Pflanzenbau u. Bodenkd. Berlin 24, 1-7], the weight of a soil sample and pressure heads at two height levels are recorded at consecutive times. The evaluation of these measurements relies on linearization assumptions with respect to time, space and the water content-pressure head relationship. In this article, we investigate the errors that result from the linearization assumptions, and show how systematic and stochastic measurement errors affect the calculation of water retention and hydraulic conductivity data and the resulting fits of soil hydraulic functions. We find that linearization errors with respect to time are negligible if cubic Hermite splines are used for data interpolation. Linearizations in space lead to minor errors, even in the late stage of evaporation where strongly non-linear pressure head profiles emerge. A bias in the estimated retention function results from the negligence of a non-linear water content distribution in the sample at the begin of the evaporation process, and affects primarily coarse sands or soils with structured pore systems. This error can be avoided if an integral evaluation of the measurements is used. We introduce an applicable rejection criterion for unreliable hydraulic conductivity data near saturation, based on the error in the hydraulic gradient. Calibration errors of tensiometers lead to biased estimates of hydraulic properties in the wet range, whereas errors in tensiometer installation positions yield biases in the dry range. Random errors in data cause no significant bias, and parametric hydraulic functions can be estimated with small uncertainties, if water retention and conductivity functions are coupled and the underlying model structure is correct.

Peters, A.; Durner, W.

2008-07-01

14

Upscaling of soil hydraulic properties for steady state evaporation and infiltration  

E-print Network

Upscaling of soil hydraulic properties for steady state evaporation and infiltration Jianting Zhu September 2002. [1] Estimation of effective/average soil hydraulic properties for large land areas and guidelines for upscaling soil hydraulic properties in an areally heterogeneous field. In this study, we

Mohanty, Binayak P.

15

Measuring Hydraulic Properties of Soil-Foundry Sand Mixtures  

NASA Astrophysics Data System (ADS)

The foundry industry produces clay coated sand particles that have potential to affect soil water retention and conductivity if mixed with soils at the proper ratio. The purpose of our study was to determine the effects of mixing foundry sand on increasing the saturated hydraulic conductivity of slowly permeable soils. Our methods included mixing Walla-Walla silt loam soil with increasing volumes of foundry sand from 0% to 100%. We then used several packing methods to determine the optimum bulk density for our automated retention and outflow experiments. To increase the range of the retention function, we also measured soil water retention using pressure plates at pressures between 1000 and 15000 cm pressure head. We measured saturated hydraulic conductivity using the constant head method and a single blind approach (the Ksat was measured in two labs, one had knowledge of the mixtures and one had no knowledge of the mixtures). The single blind approach was used to reduce the chance of bias in measuring Ksat and water retention. Our results for the saturated hydraulic conductivity did indicate that additions of foundry sand had a limited effect on Ksat until a critical level of sand was added to the mixture. The retention function was similarly affected by increasing volumes of foundry sand. The rankings of the Ksat measurements between the labs was constant, but the values obtained did differ (some significantly). For the Walla-Walla soil, additions of foundry sands exceeding 40% were needed to affect the measured Ksat and retention function. At these large volumes of foundry sands, it may be more appropriate to use the sands for new installations of turf grass such as athletic fields, and/or golf greens. We are continuing to study the characteristics of different foundry sands and quantifying their effects on the hydraulic properties of clay soils.

Shouse, P. J.; Dungan, R. S.; Dees, N.; Fargerlund, J.

2005-12-01

16

Hydraulic properties of mine soils with embedded lignitic fragments  

NASA Astrophysics Data System (ADS)

Lignitic mine soils represent a typical two-scale dual-porosity medium consisting of a technogenic mixture of overburden sediments that include lignitic components as dust and as porous fragments embedded within a mostly coarse-textured matrix. Flow and transport processes in such soils are not sufficiently understood to predict the course of soil reclamation or of mine drainage. The objective of this contribution is to identify the most appropriate conceptual model for describing small-scale heterogeneity effects on flow on the basis of the physical structure of the system. Two-domain hydraulic properties were derived based on multi-step outflow data. The interface between fragments and sandy matrix represents an additional pore region that cannot be derived from information of either the matrix or the fragments. New information is required on the geometry (size and shape) and spatial distribution of fragments to describe the properties of the mine soil as a whole.

Gerke, Horst H.

2014-05-01

17

Spatial Association among Soil Hydraulic Properties, Soil Texture, and Geoelectrical Resistivity  

Microsoft Academic Search

Spatial variability of soil hydraulic properties causes considerable variations in water and solute flow and transport processes. It remains a difficult task to determine and describe the spatial pattern of soil physical properties for modeling landscape-scale vadose zone pro- cesses. Strategies that involve measurements of relevant variables and appropriate spatial modeling tools need to be identified for this pur- pose.

Ole Wendroth; Sylvia Koszinski; Eugenia Pena-Yewtukhiv

2006-01-01

18

MULTIMODEL ENSEMBLE PREDICTION OF SOIL HYDRAULIC PROPERTIES TO SIMULATE FIELD-SCALE SOIL WATER FLOW  

Technology Transfer Automated Retrieval System (TEKTRAN)

Using pedotransfer functions (PTF) to estimate soil hydraulic properties may be necessary in soil water flow simulations for large-scale projects or in a pilot studies. The accuracy of a PTF outside of its development dataset is unknown. Existence of several models that are developed and tested in o...

19

Measuring Particle Size Distribution Using Laser Diffraction: Implications for Predicting Soil Hydraulic Properties  

E-print Network

, a reasonable prediction of measured saturated hydraulic con- ductivity and water retention curve was achieved Hydraulic Properties Eran Segal,1 Peter J. Shouse,2 Scott A. Bradford,2 Todd H. Skaggs,2 and Dennis L. Corwin2 Abstract: Methods to predict soil hydraulic properties frequently re- quire information

Ahmad, Sajjad

20

Development and use of a database of hydraulic properties of European soils  

Microsoft Academic Search

Many environmental studies on the protection of European soil and water resources make use of soil water simulation models. A major obstacle to the wider application of these models is the lack of easily accessible and representative soil hydraulic properties. In order to overcome this apparent lack of data, a project was initiated to bring together the available hydraulic data

J. H. M. Wösten; A Lilly; A Nemes; C. Le Bas

1999-01-01

21

Effects of native forest restoration on soil hydraulic properties, Auwahi, Maui, Hawaiian Islands  

E-print Network

Effects of native forest restoration on soil hydraulic properties, Auwahi, Maui, Hawaiian Islands K forest restoration on soil hydraulic properties, Auwahi, Maui, Hawaiian Islands, Geophys. Res. Lett., 39] that was once an important resource for ancient Hawaiians [Medeiros, 2003; Medeiros et al., 1998]. A 10 acre

22

Variation of Surficial Soil Hydraulic Properties Across Land Uses in the Southern Blue Ridge Mountains  

Microsoft Academic Search

Soil hydraulic properties have been shown to affect watershed hydrology by influencing pathways and transmission rates of precipitation to stream networks, and human land use has been shown to influence these soil properties. Particle size distribution, saturated hydraulic conductivity, bulk density, and water holding capacity were measured at 90 points (30 points in each land use category of forest, lawn,

K. Price; C. R. Jackson; A. J. Parker

2008-01-01

23

SENSITIVITY OF TILE DRAINAGE FLOW AND CROP YIELD ON MEASURED AND CALIBRATED SOIL HYDRAULIC PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Process-based agricultural systems models require detailed description of soil hydraulic properties that are usually not available. The objectives of this study were to evaluate the sensitivity of model simulation results to uncertainty in measured soil hydraulic properties and to compare simulation...

24

Estimation of Soil Hydraulic Properties from Numerical Inversion of Tension Disk Infiltrometer Data  

Technology Transfer Automated Retrieval System (TEKTRAN)

Many applications involving variably saturated flow and transport require estimates of the unsaturated soil hydraulic properties. Numerical inversion of cumulative infiltration data during transient flow, complemented with initial or final soil water content data, is an increasingly popular approach...

25

Environmental and management influences on temporal variability of near saturated soil hydraulic properties?  

PubMed Central

Structural porosity is a decisive property for soil productivity and soil environmental functions. Hydraulic properties in the structural range vary over time in response to management and environmental influences. Although this is widely recognized, there are few field studies that determine dominant driving forces underlying hydraulic property dynamics. During a three year field experiment we measured temporal variability of soil hydraulic properties by tension infiltrometry. Soil properties were characterized by hydraulic conductivity, effective macroporosity and Kosugi's lognormal pore size distribution model. Management related influences comprised three soil cover treatment (mustard and rye vs. fallow) and an initial mechanical soil disturbance with a rotary harrow. Environmental driving forces were derived from meteorological and soil moisture data. Soil hydraulic parameters varied over time by around one order of magnitude. The coefficient of variation of soil hydraulic conductivity K(h) decreased from 69.5% at saturation to 42.1% in the more unsaturated range (? 10 cm pressure head). A slight increase in the Kosugi parameter showing pore heterogeneity was observed under the rye cover crop, reflecting an enhanced structural porosity. The other hydraulic parameters were not significantly influenced by the soil cover treatments. Seedbed preparation with a rotary harrow resulted in a fourfold increase in macroporosity and hydraulic conductivity next to saturation, and homogenized the pore radius distribution. Re-consolidation after mechanical loosening lasted over 18 months until the soil returned to its initial state. The post-tillage trend of soil settlement could be approximated by an exponential decay function. Among environmental factors, wetting-drying cycles were identified as dominant driving force explaining short term hydraulic property changes within the season (r2 = 0.43 to 0.59). Our results suggested that beside considering average management induced changes in soil properties (e.g. cover crop introduction), a dynamic approach to hydrological modeling is required to capture over-seasonal (tillage driven) and short term (environmental driven) variability in hydraulic parameters. PMID:24748683

Bodner, G.; Scholl, P.; Loiskandl, W.; Kaul, H.-P.

2013-01-01

26

Water infiltration and hydraulic conductivity in sandy cambisols: impacts of forest transformation on soil hydrological properties  

Microsoft Academic Search

Soil hydrological properties like infiltration capacity and hydraulic conductivity have important consequences for hydrological\\u000a properties of soils in river catchments and for flood risk prevention. They are dynamic properties due to varying land use\\u000a management practices. The objective of this study was to characterize the variation of infiltration capacity, hydraulic conductivity\\u000a and soil organoprofile development on forest sites with comparable

Oliver Bens; Niels Arne Wahl; Holger Fischer; Reinhard F. Hüttl

2007-01-01

27

Comparing hydraulic properties of soil-less substrates with natural soils: a more detailed look at hydraulic properties and their impact on plant water availability  

NASA Astrophysics Data System (ADS)

Moisture release curves are often used when assessing plant-water relationships in soil-less substrates. However, differences between natural soils and soilless substrates make traditional assumptions about plant available water potentially invalid. If soil-less substrates are supposed to be treated like natural soils; why do plants begin wilting at very low water potentials (-10 to -30 kPa) and there is anywhere between 20 to 40 % water left (on a volumetric basis) in the soil (Abad et al., 2005; Arguedas et al., 2006; Ristvey et al, 2008) . We hypothesize that the fault lies in the methods used and the assumption that water potential is the only limiting factor in water availability to plants. Hydraulic properties, including the relationships that exist between plant available water, water content, and hydraulic conductivity of soil-less substrates have traditionally been characterized using instrumentation such as pressure plates, hanging water columns, and tempe cells. These approaches typically take a months and only provide data on select segments of the soil moisture release curve, and in the case of pressure plates and hanging water columns hydraulic conductivity is ignored and not very well understood. Using the Wind/Schindler Evaporation method more detailed measurements of these hydraulic properties can be measured in a less than a week. A more detailed look at the hydraulic properties of soil-less substrates and how they compare with natural soils may give us more insight into soil-plant-water-relations and what limits availability of water to plants. Soil moisture release curves and hydraulic conductivity curves of different soil-less substrates were compared with curves from typical agriculture soils to give insight into how these properties compare. Results of the soil moisture release curves showed that some soil-less substrates had comparable moisture release curves to agricultural soils while others had bi-modal curves indicating gap-gradation in the pore size distribution. These soils that showed this non-typical curve had hydraulic conductivities that dropped very low (500 times lower than agricultural soils) at low water potentials (around 10 kPa). This dramatically lower hydraulic conductivity could lead to zones of depletion around the roots hindering plant water uptake.

Crawford, L.; Rivera, L. D.; van Iersel, M.

2013-12-01

28

Hydraulic and mechanical properties of soil aggregates under organic and conventional soil management  

NASA Astrophysics Data System (ADS)

Variation in hydraulic and mechanical properties of soil aggregates is an important factor affecting water storage and infiltration because the large inter-aggregate pores are dewatered first and the transport of water and solutes is influenced by the properties of the individual aggregates and contacts between them. A high mechanical stability of soil aggregates is fundamental for the maintenance of proper tilth and provides stable traction for farm implements, but limit root growth inside aggregates. The aggregate properties are largely influenced by soil management practices. Our objective was to compare the effects of organic and conventional soil management on hydraulic and mechanical properties of soil aggregates. Experimental fields subjected to long-term organic (14 years) and conventional managements were located on loamy soil at the Institute of Soil Science and Plant Cultivation - National Research Institute in Pulawy, Poland. Soil samples were collected from two soil depths (0-10 cm and 10-20 cm). After air-drying, two size fractions of soil aggregates (15-20 and 30-35 mm) were manually selected and kept in the dried state in a dessicator in order to provide the same boundary conditions. Following properties of the aggregates were determined: porosity (%) using standard wax method, cumulative infiltration Q (mm3 s-1) and sorptivity S (mm s -1/2) of water and ethanol using a tube with a sponge inserted at the tip, wettability (by comparison of sorptivity of water and ethanol) using repellency index R, crushing strength q (MPa) using strength testing device (Zwick/Roell) and calculated by Dexter's formula. All properties were determined in 15 replicates for each treatment, aggregates size and depth. Organic management decreased porosity of soil aggregates and ethanol infiltration. All aggregates revealed rather limited wettability (high repellency index). In most cases the aggregate wettability was lower under conventional than organic soil management. Crushing strength was higher for aggregates from organic managed field, especially for 30-35 mm aggregates.

Wójciga, A.; Ku?, J.; Turski, M.; Lipiec, J.

2009-04-01

29

Effects of long-term soil and crop management on soil hydraulic properties for claypan soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Regional and national soil maps have been developed along with associated soil property databases to assist users in making land management decisions based on soil characteristics. These soil properties include average values from soil characterization for each soil series. In reality, these propert...

30

Spatial and temporal variability of soil hydraulic properties of topsoil affected by soil erosion  

NASA Astrophysics Data System (ADS)

This study is focused on the comparison of soil hydraulic properties of topsoil that is affected by erosion processes. In order to include variable morphological and soil properties along the slope three sites - Brumovice, Vidim and Sedl?any were selected. Two transects (A, B) and five sampling sites along each one were chosen. Soil samples were taken in Brumovice after the tillage and sowing of winter wheat in October 2010 and after the wheat harvest in August 2011. At locality Vidim and Sedl?any samples were collected in May and August 2012. Soil hydraulic properties were studied in the laboratory on the undisturbed 100-cm3 soil samples placed in Tempe cells using the multi-step outflow test. Soil water retention data points were obtained by calculating water balance in the soil sample at each pressure head step of the experiment. The single-porosity model in HYDRUS-1D was applied to analyze the multi-step outflow and to obtain the parameters of soil hydraulic properties using the numerical inversion. The saturated hydraulic conductivities (Ks) and unsaturated hydraulic conductivities (Kw) for the pressure head of -2 cm of topsoil were also measured after the harvest using Guelph permeameter and Minidisk tensiometer, respectively. In general soil water retention curves measured before and after vegetation period apparently differed, which indicated soil material consolidation and soil-porous system rearrangement. Soil water retention curves obtained on the soil samples and hydraulic conductivities measured in the field reflected the position at the elevation transect and the effect of erosion/accumulation processes on soil structure and consequently on the soil hydraulic properties. The highest Ks values in Brumovice were obtained at the steepest parts of the elevation transects, that have been the most eroded. The Ks values at the bottom parts decreased due to the sedimentation of eroded soil particles. The change of the Kw values along transects didn't show similar trends. However, the variability of values within both transects was low. Higher values were obtained in transect B, where the soil was more affected by erosion. The highest values of Ks as well as the value of Kw were also obtained in the steepest part of transect A in Vidim. This trend was not observed in transect B. The results corresponded with measured retention curves. Two different trends were shown in Sedl?any. While the highest values of Ks and Kw were found in the upper part of transect A, in the case of transect B the highest values were measured at the bottom of transect. Differences observed at both localities were caused by the different terrain attributes of both transects and extent of soil erosion. Acknowledgement: Authors acknowledge the financial support of the Ministry of Agriculture of the Czech Republic (QJ1230319).

Nikodem, Antonin; Kodesova, Radka; Jaksik, Ondrej; Jirku, Veronika; Klement, Ales; Fer, Miroslav

2014-05-01

31

Modeling the hydraulic properties of a multiregion soil  

Microsoft Academic Search

Numerical techniques for modeling transport of solutes in multiple porosity systems have recently been developed to better represent the physical attributes of structured soils. Multiregion flow modeling requires characterization of the water content ([Theta]) and hydraulic conductivity (K) as a function of pressure head (h) for each region of the system. A technique is presented for determining the [Theta](h) and

G. V. Wilson; P. M. Jardine; J. P. Gwo

2009-01-01

32

TWENTY YEARS OF TILLAGE RESEARCH IN SUBARCTIC ALASKA:II. IMPACT ON SOIL HYDRAULIC PROPERTIES.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil management practices are needed in the subarctic that stabilize the soil against the forces of wind and water as well as conserve soil water for crop production. There is a paucity of information, however, regarding the long-term effects of conservation tillage on soil hydraulic properties in s...

33

Soil hydraulic properties of topsoil along two elevation transects affected by soil erosion  

NASA Astrophysics Data System (ADS)

This study is focused on the comparison of soil hydraulic properties of topsoil that is affected by erosion processes. Studied area is characterized by a relatively flat upper part, a tributary valley in the middle and a colluvial fan at the bottom. Haplic Chernozem reminded at the flat upper part of the area. Regosols were formed at steep parts of the valley. Colluvial Chernozem and Colluvial soils were formed at the bottom parts of the valley and at the bottom part of the studied field. Two transects and five sampling sites along each one were selected. The soil-water retention curves measured on the undisturbed 100-cm3 soil samples taken after the tillage and sowing of winter wheat (October 2010) were highly variable and no differences between sampling sites within the each transect were detected. Variability of soil-water retention curves obtained on soil samples taken after the wheat harvest (August 2011) considerably deceased. The parts of the retention curves, which characterized the soil matrix, were very similar. The main differences between the soil-water retention curves were found in parts, which corresponded to larger capillary pores. The fractions of the large capillary pores (and also saturated soil water-contents) were larger after the harvest (soil structure reestablishment) than that after the tillage and sawing (soil structure disturbance). Greater amount of capillary pores was observed in soils with better developed soil structure documented on the micromorphological images. The saturated hydraulic conductivities (Ks) and unsaturated hydraulic conductivities (K) for the pressure head of -2 cm of topsoil were also measured after the wheat harvest using Guelph permeameter and Minidisk tensiometer, respectively. The highest Ks values were obtained at the steepest parts of the elevation transects, that have been the most eroded. The Ks values at the bottom parts decreased due to the sedimentation processes of eroded soil particles. The change of the K values along transects didn't show similar trends. However, the variability of values within both transects was low. The undisturbed soil samples (3200 cm3) were also taken at 3 sampling sites and ponding infiltration experiment was performed in the laboratory. Cumulative inflow and outflow, and pressure heads at depths of 6.5, 11 a 15.5 cm were measured. Numerical inversion of measured data using HYDRUS-1D was performed to obtain parameters of van Genuchten hydraulic function. Data obtain from previous tests were used to characterize development of dual permeability system along the studied transects. Acknowledgment: Authors acknowledge the financial support of the Ministry of Agriculture of the Czech Republic (QJ1230319).

Nikodem, Antonin; Kodesova, Radka; Jaksik, Ondrej; Jirku, Veronika; Fer, Miroslav; Klement, Ales; Zigova, Anna

2013-04-01

34

Effect of soil hydraulic properties on the relationship between the spatial mean and variability of soil moisture  

NASA Astrophysics Data System (ADS)

Knowledge of spatial mean soil moisture and its variability over time is needed in many environmental applications. We analyzed dependencies of soil moisture variability on average soil moisture contents in soils with and without root water uptake using ensembles of non-stationary water flow simulations by varying soil hydraulic properties under different climatic conditions. We focused on the dry end of the soil moisture range and found that the magnitude of soil moisture variability was controlled by the interplay of soil hydraulic properties and climate. The average moisture at which the maximum variability occurred depended on soil hydraulic properties and vegetation. A positive linear relationship was observed between mean soil moisture and its standard deviation and was controlled by the parameter defining the shape of soil water retention curves and the spatial variability of saturated hydraulic conductivity. The influence of other controls, such as variable weather patterns, topography or lateral flow processes needs to be studied further to see if such relationship persists and could be used for the inference of soil hydraulic properties from the spatiotemporal variation in soil moisture.

Martínez García, Gonzalo; Pachepsky, Yakov A.; Vereecken, Harry

2014-08-01

35

Effect of soil water repellency on soil hydraulic properties estimated under dynamic conditions  

NASA Astrophysics Data System (ADS)

SummarySoil research done over the past decades has proven that water repellent soils are widespread in all climates. Water repellency enhances the leaching of contaminants in the unsaturated zone by introducing preferential flow. In order to predict soil water fluxes in the unsaturated zone the accurate knowledge of the soil hydraulic properties (SHP) is mandatory. In this study the effect of water repellency on both imbibition and drainage SHP was studied. Inflow/outflow experiments were conducted in the laboratory for two soils and two artificially created hydrophobic mixtures. In the inflow/outflow experiments the pressure head at the bottom of the soil column was increased/decreased and the estimated SHP functions were obtained by means of inverse modeling. Inflow/outflow experiments were also conducted using ethanol instead of water in order to estimate the effect of liquid wetting properties on the estimated characteristic curves of the materials under study. The results showed that the water retention functions and the unsaturated hydraulic conductivity functions estimated from the dynamic experiments are strongly dependent on the degree of water repellency and the wetting/drying process.

Diamantopoulos, E.; Durner, W.; Reszkowska, A.; Bachmann, J.

2013-04-01

36

Effective soil hydraulic properties in space and time: some field data analysis and modeling concepts  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil hydraulic properties, which control surface fluxes and storage of water and chemicals in the soil profile, vary in space and time. Spatial variability above the measurement scale (e.g., soil area of 0.07 m2 or support volume of 14 L) must be upscaled appropriately to determine “effective” hydr...

37

Tillage Effects on Soil Hydraulic Properties in Space and Time: State of the Science  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil tillage practices can affect soil hydraulic properties and processes in space and time with consequent and coupled effects on chemical movement and plant growth. This literature review addresses the quantitative effects of soil tillage and associated management (e.g., crop residues) on the tem...

38

Discrimination of soil hydraulic properties by combined thermal infrared and microwave remote sensing  

NASA Technical Reports Server (NTRS)

Using the De Vries models for thermal conductivity and heat capacity, thermal inertia was determined as a function of soil moisture for 12 classes of soil types ranging from sand to clay. A coupled heat and moisture balance model was used to describe the thermal behavior of the top soil, while microwave remote sensing was used to estimate the soil moisture content of the same top soil. Soil hydraulic parameters are found to be very highly correlated with the combination of soil moisture content and thermal inertia at the same moisture content. Therefore, a remotely sensed estimate of the thermal behavior of the soil from diurnal soil temperature observations and an independent remotely sensed estimate of soil moisture content gives the possibility of estimating soil hydraulic properties by remote sensing.

Vandegriend, A. A.; Oneill, P. E.

1986-01-01

39

Environmental and management impacts on temporal variability of soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Soil hydraulic properties underlie temporal changes caused by different natural and management factors. Rainfall intensity, wet-dry cycles, freeze-thaw cycles, tillage and plant effects are potential drivers of the temporal variability. For agricultural purposes it is important to determine the possibility of targeted influence via management. In no-till systems e.g. root induced soil loosening (biopores) is essential to counteract natural soil densification by settling. The present work studies two years of temporal evolution of soil hydraulic properties in a no-till crop rotation (durum wheat-field pea) with two cover crops (mustard and rye) having different root systems (taproot vs. fibrous roots) as well as a bare soil control. Soil hydraulic properties such as near-saturated hydraulic conductivity, flow weighted pore radius, pore number and macroporosity are derived from measurements using a tension infiltrometer. The temporal dynamics are then analysed in terms of potential driving forces. Our results revealed significant temporal changes of hydraulic conductivity. When approaching saturation, spatial variability tended to dominate over the temporal evolution. Changes in near-saturated hydraulic conductivity were mainly a result of changing pore number, while the flow weighted mean pore radius showed less temporal dynamic in the no-till system. Macroporosity in the measured range of 0 to -10 cm pressure head ranged from 1.99e-4 to 8.96e-6 m3m-3. The different plant coverage revealed only minor influences on the observed system dynamics. Mustard increased slightly the flow weighted mean pore radius, being 0.090 mm in mustard compared to 0.085 mm in bare soil and 0.084 mm in rye. Still pore radius changes were of minor importance for the overall temporal dynamics. Rainfall was detected as major driving force of the temporal evolution of structural soil hydraulic properties at the site. Soil hydraulic conductivity in the slightly unsaturated range (-7 cm to -10 cm) showed a similar time course as a moving average of rainfall. Drying induced a decrease in conductivity while wetting of the soil resulted in higher conductivity values. Approaching saturation however, the drying phase showed a different behaviour with increasing values of hydraulic conductivity. This may be explained probably by formation of cracks acting as large macropores. We concluded that aggregate coalescence as a function of capillary forces and soil rheologic properties (cf. Or et al., 2002) are a main predictor of temporal dynamics of near saturated soil hydraulic properties while different plant covers only had a minor effect on the observed system dynamics. Or, D., Ghezzehei, T.A. 2002. Modeling post-tillage soil structural dynamics. a review. Soil Till Res. 64, 41-59.

Bodner, G.; Scholl, P.; Loiskandl, W.; Kaul, H.-P.

2012-04-01

40

The effect of dynamic changes in soil bulk density on hydraulic properties: modeling approaches  

NASA Astrophysics Data System (ADS)

Natural and artificial processes, like rainfall-induced soil surface sealing or mechanical compaction, disturb the soil structure and enhance dynamic changes of the related pore size distribution. These changes may influence many aspects of the soil-water-plant-atmosphere system. One of the easiest measurable variables is the soil bulk density. Approaches are suggested that could model the effect of the change in soil bulk density on soil permeability, water retention curve (WRC) and unsaturated hydraulic conductivity function (HCF). The resulting expressions were calibrated and validated against experimental data corresponding to different soil types at various levels of compaction, and enable a relatively good prediction of the effect of bulk density on the soil hydraulic properties. These models allow estimating the impact of such changes on flow processes and on transport properties of heterogeneous soil profiles.

Assouline, Shmuel

2014-05-01

41

Impact of land management on soil structure and soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Study is focused on a comparison of a soil structure and soil hydraulic properties within soil profiles of a same soil type under different land management. Study was performed in Haplic Luvisol in Hnevceves the Czech Republic. Two soil profiles, which were in close distance from each other, were chosen: 1. under the conventional tillage, 2. under the permanent (30 years) grass cover. Soil sampling and field experiments were carried out immediately after the harvest of winter barley in 2008. The micromorphological images were used to evaluate the soil structure of all Ap, Bt1, Bt2 and C diagnostic horizons. The hydraulic properties of the diagnostic horizons were studied in the laboratory using multistep outflow experiments performed on the undisturbed 100-cm3 soil samples. A tension disc infiltrometer (with a disc radius of 10 cm) and minidisc tension infiltrometers (with a disc radius of 2.2 cm) were used to measure cumulative water infiltration under unsaturated conditions created using a pressure head of -2 cm. Measurements were performed at a depths of 5, 45, 75 and 110 cm, which corresponded to the Ap, Bt1, Bt2 and C horizons of studied Haplic Luvisol at both locations. The Guelph permeameter was used to measure cumulative water flux under surface ponding conditions. The depth of the drilled well was 10, 50, 80 and 115 cm, the well radius was 3 cm, and the well ponding depth was 5 cm. Both tests were used to evaluate hydraulic conductivity (K for h=-2cm, and Ks) values. Results showed, that while properties in the Bt2 and C horizons of both soil profiles were relatively similar, properties in the Ap and Bt1 horizons were different. The fraction of gravitational pores (which may cause preferential flow) in the Ap and Bt1 horizons of the soil profile under the convectional tillage was large than those in the Ap and Bt1 horizons of the soil profile under the permanent grass. This influenced for instance the Ks values measured using the Guelph permeametr. The Ks values were higher and more variable in the soil profile under the convectional tillage than those in the soil profile under the permanent grass. On the other hand, due to the periodical tillage and consequent soil structure breakdown, the fraction of the large capillary pores were smaller in the Ap horizon of the soil profile under the convectional tillage than that in the Ap horizon of the soil profile under the permanent grass. As result the K (h=-2cm) values measured using the tension infiltrometer in the soil profile under the permanent grass was higher than those in the soil profile under the convectional tillage. However, the fraction of the large capillary pores and K (h=-2cm) values were similar in the Bt1 horizons of both soil profiles. Thus the land management impacted both macropores and matrix pores in the Ap horizon and macropores (prismatic structure and biopores) in the Bt1 horizon. Acknowledgement: Authors acknowledge the financial support of the Grant Agency of the Czech Republic (grant No. GA CR 526/08/0434) and the Ministry of Education, Youth and Sports of the Czech Republic (grant No. MSM 6046070901).

Kodesova, Radka; Jirku, Veronika; Nikodem, Antonin; Muhlhanselova, Marcela; Zigova, Anna

2010-05-01

42

The Effect of Soil Hydraulic Properties vs. Soil Texture in Land Surface Models  

NASA Technical Reports Server (NTRS)

This study focuses on the effect of Soil Hydraulic Property (SHP) selection on modeled surface fluxes following a rain storm in a semi-arid environment. SHPs are often defined based on a Soil Texture Class (STC). To examine the effectiveness of this approach, the Noah land surface model was run with each of 1306 soils in a large SHP database. Within most STCs, the outputs have a range of 350 W/m2 for latent and sensible heat fluxes, and 8K for surface temperature. The average difference between STC median values is only 100 W/m2 for latent and sensible heat. It is concluded that STC explains 5-15% of the variance in model outputs and should not be used to determine SHPs.

Gutmann, E. D.; Small, E. E.

2005-01-01

43

Numerically predicting seepage gradient forces and erosion: Sensitivity to soil hydraulic properties  

NASA Astrophysics Data System (ADS)

SummaryResearch has suggested that streambank seepage can be an important mechanism of bank instability; however, limited information is available on the level of soil characterization necessary to accurately predict seepage gradient forces and erosion. The objective of this research was to quantify the expected range of predicted seepage gradients for various degrees of site characterization. Uncertainty analysis on seepage gradient predictions was performed relative to variability in soil hydraulic properties. A two-dimensional unsaturated/saturated groundwater flow model was used to simulate a homogeneous soil layer for sand and loamy sand soils packed at various bulk densities, ? b. A pedotransfer function (ROSETTA), designed to estimate unsaturated hydraulic properties from surrogate soil data (i.e., texture and bulk density), was used to derive the saturated hydraulic conductivity, K s, and water retention parameters for various levels of site information (i.e., only textural class; percent sand, silt, and clay (%SSC); %SSC and ? b; and %SSC, ? b, and K s). Statistical distributions were derived for each soil hydraulic parameter and Monte Carlo simulations were performed to generate distributions of maximum seepage gradient. The deviation in predicted seepage gradient was calculated using assumed baseline conditions. Ranges in predicted soil hydraulic parameters and maximum seepage gradients were considerably reduced when using %SSC as compared to soil texture. Therefore, at a minimum, soil samples should be taken for particle size analysis. For ? b between 1450 and 1500 kg m -3, soil hydraulic parameters could be derived using ROSETTA and inputting %SSC, with little additional benefit provided by measuring ? b and/or K s. When the ? b was less than 1450-1500 kg m -3, inputting ? b and/or K s consistently reduced the magnitude of deviations from the baseline and therefore should be measured from undisturbed soil samples. The opposite was observed for ? b greater than 1450-1500 kg m -3 due to discrepancies between ROSETTA-derived and actual values of soil hydraulic parameters other than K s. Considerable deviations (i.e., around 20%) were observed in seepage gradients under this scenario. When ROSETTA-derived and actual values of soil hydraulic parameters more closely matched, inputting ? b and/or K s benefitted seepage gradient predictions as deviations in seepage gradients were less than 5% for the sand and loamy sand soils. Therefore, it is vital to quantify all soil hydraulic parameters for high ? b soils and textures with a wide range in %SSC.

Fox, Garey A.; Heeren, Derek M.; Wilson, Glenn V.; Langendoen, Eddy J.; Fox, Amanda K.; Chu-Agor, Maria L.

2010-08-01

44

Identification of soil hydraulic properties over the full moisture range by inverse modeling of evaporation experiments  

NASA Astrophysics Data System (ADS)

Semi-arid regions represent a significant portion of earth's surface. Reliable quantification of the soil water balance in these regions plays a key role for estimating ground water recharge and a proper management of water use. However, modeling of soil water movement in relatively dry soils and the accurate prediction of the evaporative fluxes to the atmosphere and the deep drainage to the groundwater, pose considerable challenges. Simulation of these processes relies on a proper conceptual model for water flow and an adequate parameterization of the soil hydraulic properties. While the experimental characterization of soil water retention in dry soils has made significant progress, for instance by the introduction and more widespread use of the dewpoint method, the measurement of unsaturated hydraulic conductivity in medium to dry soils remains a challenge. In dry soils, the determination of hydraulic conductivity is difficult, because the measurement of the water potential gradient is not trivial. The aim of this study was to identify soil hydraulic properties by inverse modeling, with a particular focus on the medium to dry moisture range. We conducted evaporation experiments on large soil columns under laboratory conditions. An extended instrumentation using tensiometres and relative humidity sensors enabled us to monitor water potential in the columns from full wetness to air dryness. We found that the unsaturated hydraulic conductivity functions which lead to a good match between model-predicted and observed flux and potential data differed markedly from those obtained from traditional conceptual models of hydraulic conductivity. For validation purposes, we tested the predictive capabilities of the identified hydraulic functions under boundary conditions which were different from those used for parameter identification, and found them to be good predictors of system behavior.

Iden, Sascha C.; Diamantopoulos, Efstathios; Scharnagl, Benedikt; Durner, Wolfgang

2014-05-01

45

SOIL HYDRAULIC PROPERTIES INFLUENCED BY CORN STOVER REMOVAL FROM NO-TILL CORN IN OHIO  

Technology Transfer Automated Retrieval System (TEKTRAN)

Corn (Zea mays L.) stover removal for biofuel production and other uses may alter soil hydraulic properties, but site-specific information needed to determine the threshold levels of removal for the U.S. Corn Belt region is limited. We quantified impacts of systematic removal of corn stover on soil ...

46

Uncertainty in predicting soil hydraulic properties at the hillslope scale with indirect methods  

NASA Astrophysics Data System (ADS)

SummarySeveral hydrological applications require the characterisation of the soil hydraulic properties at large spatial scales. Pedotransfer functions (PTFs) are being developed as simplified methods to estimate soil hydraulic properties as an alternative to direct measurements, which are unfeasible for most practical circumstances. The objective of this study is to quantify the uncertainty in PTFs spatial predictions at the hillslope scale as related to the sampling density, due to: (i) the error in estimated soil physico-chemical properties and (ii) PTF model error. The analysis is carried out on a 2-km-long experimental hillslope in South Italy. The method adopted is based on a stochastic generation of patterns of soil variables using sequential Gaussian simulation, conditioned to the observed sample data. The following PTFs are applied: Vereecken's PTF [Vereecken, H., Diels, J., van Orshoven, J., Feyen, J., Bouma, J., 1992. Functional evaluation of pedotransfer functions for the estimation of soil hydraulic properties. Soil Sci. Soc. Am. J. 56, 1371-1378] and HYPRES PTF [Wösten, J.H.M., Lilly, A., Nemes, A., Le Bas, C., 1999. Development and use of a database of hydraulic properties of European soils. Geoderma 90, 169-185]. The two PTFs estimate reliably the soil water retention characteristic even for a relatively coarse sampling resolution, with prediction uncertainties comparable to the uncertainties in direct laboratory or field measurements. The uncertainty of soil water retention prediction due to the model error is as much as or more significant than the uncertainty associated with the estimated input, even for a relatively coarse sampling resolution. Prediction uncertainties are much more important when PTF are applied to estimate the saturated hydraulic conductivity. In this case model error dominates the overall prediction uncertainties, making negligible the effect of the input error.

Chirico, G. B.; Medina, H.; Romano, N.

2007-02-01

47

Vertical variations of soil hydraulic properties within two soil profiles and its relevance for soil water simulations  

NASA Astrophysics Data System (ADS)

Numerical simulations of soil water dynamics can be valuable tools for the assessment of different soil and land management practices. For accurate simulations, the soil hydraulic properties (SHP), i.e. the hydraulic conductivity and water retention function have to be properly known. They can be either estimated from physical soil properties by pedotransfer functions (PTF) or measured. In most studies, soil profiles are analyzed and sampled with respect to their pedogenic horizons. While considerable effort has been put on horizontal spatial SHP variations, vertical changes within soil profiles have not been analyzed in detail. Therefore, the objectives of this study were (i) the SHP measurement along vertical transects within two soil profiles, (ii) to evaluate their spatial variation and correlation with physical soil properties, and (iii) to assess the impact of the SHP determination method and its spatial discretization on simulated soil water balance components. Two soils, an agriculturally used silty-loam Chernozem and a forested sandy Cambisol were sampled in 0.05 m increments along vertical transects. The parameters of a dual porosity model were derived using the evaporation method and scaling was applied to derive representative mean SHP parameters and scaling factors as a measure of spatial variability. State-space models described spatial variations of the scaling factors by physical soil properties. Simulations with HYDRUS 1D delivered the soil water balance for different climatic conditions with the SHP being estimated from horizon-wise PTFs, or discretized either sample-wise, according to the pedogenic horizons, or as hydrologically relevant units (hydropedological approach). Considerable SHP variations were found for both soil profiles. In the Chernozem, variations of the hydraulic conductivity were largest within the ploughed Ap-horizon and could be attributed to variations in soil structure (macropores). In the subsoil, soil water retention showed a gradual decrease within each horizon. The observed water retention variations could be described by state-space models that comprised the contents of clay and total carbon, whereas variations of the hydraulic conductivity were described by clay content and total porosity. The hydraulic conductivity in the Cambisol was slightly undulating throughout the profile. Here, water retention was largest in the upper part of the profile and considerably decreased within the lower part of the Bhs-horizon. Simulated soil water balance components differed distinctly between the SHP discretizations. Compared to observed soil water contents, the simulations where the SHP were given by small-scale layers or hydropedological units performed best for both experimental sites. The different SHP discretizations mainly affected the estimated drainage losses and the simulated crop transpiration under medium to dry climatic conditions. The study confirmed the importance of an adequate spatial SHP discretization. The results indicate that SHP estimations by PTFs or the standard horizon-mean sampling strategy might fail to parameterize soil water simulations, especially in structured soils. The presented hydropedological approach showed a way to receive good simulation results by reducing the SHP observation density.

Schwen, Andreas; Zimmermann, Michael; Bodner, Gernot

2014-08-01

48

Variation of Surficial Soil Hydraulic Properties Across Land Uses in the Southern Blue Ridge Mountains  

NASA Astrophysics Data System (ADS)

Soil hydraulic properties have been shown to affect watershed hydrology by influencing pathways and transmission rates of precipitation to stream networks, and human land use has been shown to influence these soil properties. Particle size distribution, saturated hydraulic conductivity, bulk density, and water holding capacity were measured at 90 points (30 points in each land use category of forest, lawn, and pasture) in a 900km2 area in the North Carolina Blue Ridge. Forest soils demonstrated markedly lower bulk densities and higher infiltration rates, and water holding capacities than lawn and pasture soils, which did not differ. Mean values for each property were (forest = F, lawn = L, pasture = P): saturated hydraulic conductivity (cm/h) - F=7.7, L=1.1, P=1.2; bulk density (g/cm3) - F=0.8, L=1.2, P=1.2; water holding capacity (%) - F=72, L=42, P=39. Particle size distributions did not significantly differ among land use classes or parent materials, and the differences between the hydraulic properties of forest vs. nonforest soils were attributed to compaction associated with land management practices. These results suggests that widespread conversion of forest to other land uses in this region will be accompanied by decreased infiltration and increased overland flow, potentially significantly altering water budgets and leading to reduced baseflows.

Price, K.; Jackson, C. R.; Parker, A. J.

2008-12-01

49

Effects of native forest restoration on soil hydraulic properties, Auwahi, Maui, Hawaiian Islands  

USGS Publications Warehouse

Over historic time Hawai'i's dryland forests have been largely replaced by grasslands for grazing livestock. On-going efforts have been undertaken to restore dryland forests to bring back native species and reduce erosion. The reestablishment of native ecosystems on land severely degraded by long-term alternative use requires reversal of the impacts of erosion, organic-matter loss, and soil structural damage on soil hydraulic properties. This issue is perhaps especially critical in dryland forests where the soil must facilitate native plants' optimal use of limited water. These reforestation efforts depend on restoring soil ecological function, including soil hydraulic properties. We hypothesized that reforestation can measurably change soil hydraulic properties over restoration timescales. At a site on the island of Maui (Hawai'i, USA), we measured infiltration capacity, hydrophobicity, and abundance of preferential flow channels in a deforested grassland and in an adjacent area where active reforestation has been going on for fourteen years. Compared to the nearby deforested rangeland, mean field-saturated hydraulic conductivity in the newly restored forest measured by 55 infiltrometer tests was greater by a factor of 2.0. Hydrophobicity on an 8-point scale increased from average category 6.0 to 6.9. A 4-point empirical categorization of preferentiality in subsurface wetting patterns increased from an average 1.3 in grasslands to 2.6 in the restored forest. All of these changes act to distribute infiltrated water faster and deeper, as appropriate for native plant needs. This study indicates that vegetation restoration can lead to ecohydrologically important changes in soil hydraulic properties over decadal time scales.

Perkins, Kimberlie S.; Nimmo, John R.; Medeiros, Arthur C.

2012-01-01

50

Variability and scaling of hydraulic properties for 200 Area soils, Hanford Site  

SciTech Connect

Over the years, data have been obtained on soil hydraulic properties at the Hanford Site. Much of these data have been obtained as part of recent site characterization activities for the Environmental Restoration Program. The existing data on vadose zone soil properties are, however, fragmented and documented in reports that have not been formally reviewed and released. This study helps to identify, compile, and interpret all available data for the principal soil types in the 200 Areas plateau. Information on particle-size distribution, moisture retention, and saturated hydraulic conductivity (K{sub s}) is available for 183 samples from 12 sites in the 200 Areas. Data on moisture retention and K{sub s} are corrected for gravel content. After the data are corrected and cataloged, hydraulic parameters are determined by fitting the van Genuchten soil-moisture retention model to the data. A nonlinear parameter estimation code, RETC, is used. The unsaturated hydraulic conductivity relationship can subsequently be predicted using the van Genuchten parameters, Mualem`s model, and laboratory-measured saturated hydraulic conductivity estimates. Alternatively, provided unsaturated conductivity measurements are available, the moisture retention curve-fitting parameters, Mualem`s model, and a single unsaturated conductivity measurement can be used to predict unsaturated conductivities for the desired range of field moisture regime.

Khaleel, R.; Freeman, E.J.

1995-10-01

51

Bayesian inverse modelling of in situ soil water dynamics: using prior information about the soil hydraulic properties  

NASA Astrophysics Data System (ADS)

In situ observations of soil water state variables under natural boundary conditions are often used to estimate field-scale soil hydraulic properties. However, many contributions to the soil hydrological literature have demonstrated that the information content of such data is insufficient to reliably estimate all the soil hydraulic parameters. In this case study, we tested whether prior information about the soil hydraulic properties could help improve the identifiability of the van Genuchten-Mualem (VGM) parameters. Three different prior distributions with increasing complexity were formulated using the ROSETTA pedotransfer function (PTF) with input data that constitutes basic soil information and is readily available in most vadose zone studies. The inverse problem was posed in a formal Bayesian framework and solved using Markov chain Monte Carlo (MCMC) simulation with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. Synthetic and real-world soil water content data were used to illustrate our approach. The results of this study corroborate and explicate findings previously reported in the literature. Indeed, soil water content data alone contained insufficient information to reasonably constrain all VGM parameters. The identifiability of these soil hydraulic parameters was substantially improved when an informative prior distribution was used with detailed knowledge of the correlation structure among the respective VGM parameters. A biased prior did not distort the results, which inspires confidence in the robustness and effectiveness of the presented method. The Bayesian framework presented in this study can be applied to a wide range of vadose zone studies and provides a blueprint for the use of prior information in inverse modelling of soil hydraulic properties at various spatial scales.

Scharnagl, B.; Vrugt, J. A.; Vereecken, H.; Herbst, M.

2011-02-01

52

Using the NRCS National Soils Information System (NASIS) to provide soil hydraulic properties for engineering applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

Modern agricultural, biological, and environmental engineers have a multitude of uses for soil hydraulic parameters that quantify the ability of soils and sediments to retain and transmit water. These parameters are difficult and costly to obtain, especially if large areas of land need to be charac...

53

LANDSCAPE AND CONSERVATION MANAGEMENT EFFECTS ON SOIL HYDRAULIC PROPERTIES FOR AN EPIAQUALF  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage and conservation management systems have been developed to reduce the environmental impacts of crop production systems, and have been reported to influence soil hydraulic properties. However, the effects of landscape positions and their interaction with management systems have received less ...

54

Measuring Particle Size Distribution using Laser Diffraction: Implications for Predicting Soil Hydraulic Properties  

Technology Transfer Automated Retrieval System (TEKTRAN)

Methods to predict soil hydraulic properties frequently require information on the particle size distribution (PSD). The objectives of this study were to investigate various protocols for rapidly measuring PSD using the laser diffraction technique, compare the obtained PSDs with those determined usi...

55

Taking into account the heterogeneity and the temporal variability of the soil structure to implement relevant soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Due to its position at the interface between the atmosphere and the vadose zone, the soil significantly contributes to the partitioning of rainfall into infiltration and overland flow, and, as a consequence, to the water feeding to plants and to the water aquifer level. The characteristics of the soil are usually described at the scale of the horizon, the latter being considered as the elementary component of the pedological maps and soil databases. As far as hydraulic properties are concerned - the water retention curve and the unsaturated hydraulic conductivity, the two essential soil characteristics for the description of soil water transfers -, their estimation at the horizon scale is then of major interest. Nevertheless, even at this scale, the horizon can usually not be considered neither as a homogeneous volume, nor as a time-stable system. As a consequence, methodologies have to be developed to characterize i) the degree of heterogeneity of the soil structure, ii) the evolution of the structure with time, and iii) if possible, the equivalent properties of such heterogeneous horizons. The surface horizons and the stony horizons can be considered as representative models of soil horizons to test these methodologies: the first ones because their fine structure evolves rapidly, under the effect of human agricultural activities - compaction by wheeling, fragmentation by tillage - of climate, or of faunal and vegetal actions; the second ones because the strong difference in material and in bulk density between fine earth and rock fragments lead to complex hydric behaviors. Based on several examples, the objectives of this presentation will then be i) to describe the temporal evolution of soil hydraulic properties in cultivated horizons, ii) to present methodologies for the estimation of equivalent soil hydraulic properties in stony horizons, and iii) to discuss the contribution of this new methodologies compared to old ones to better estimate the soil hydric functioning at the local or regional scales.

Cousin, Isabelle; Tetegan, Marion; Chabbi, Abad; Korboulewski, Nathalie

2013-04-01

56

Quantitative Metrics of Soil Structure and Relationships to Hydraulic Properties in a Vertic Argiudoll  

E-print Network

to soil hydraulic parameters, especially saturated hydraulic conductivity (Ks) and water retention curve (WRC) parameters. Soil moisture data collected at the lysimeter, in conjunction with atmospheric data from an adjacent tower, were used as inputs...

Eck, Dennis V.

2014-05-31

57

SOIL HYDRAULIC AND ELECTRICAL PROPERTIES FOR DIFFERENT SOILS, SLOPES, AND CROP ROTATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Crop management can alter soil physical properties, but variability of these properties may mask treatment effects. The purpose of this study was to compare soil physical property variation under two crop rotations, and to examine interrelations among different soil physical properties. A six-year r...

58

Assessing agricultural management effects on structure related soil hydraulic properties by tension infiltrometry  

NASA Astrophysics Data System (ADS)

Soil structure is a dynamic property subject to numerous natural and human influences. It is recognized as fundamental for sustainable functioning of soil. Therefore knowledge of management impacts on the sensitive structural states of soil is decisive in order to avoid soil degradation. The stabilization of the soil's (macro)pore system and eventually the improvement of its infiltrability are essential to avoid runoff and soil erosion, particularly in view of an increasing probability of intense rainfall events. However structure-related soil properties generally have a high natural spatiotemporal variability that interacts with the potential influence of agricultural land use. This complicates a clear determination of management vs. environmental effects and requires adequate measurement methods, allowing a sufficient spatiotemporal resolution to estimate the impact of the targeted management factors within the natural dynamics of soil structure. A common method to assess structure-related soil hydraulic properties is tension infiltrometry. A major advantage of tension infiltrometer measurements is that no or only minimum soil disturbance is necessary and several structure-controlled water transmission properties can readily be derived. The method is more time- and cost-efficient compared to laboratory measurements of soil hydraulic properties, thus enabling more replications. Furthermore in situ measurements of hydraulic properties generally allow a more accurate reproduction of field soil water dynamics. The present study analyses the impact of two common agricultural management options on structure related hydraulic properties based on tension infiltrometer measurements. Its focus is the identification of the role of management within the natural spatiotemporal variability, particularly in respect to seasonal temporal dynamics. Two management approaches are analysed, (i) cover cropping as a "plant-based" agro-environmental measure, and (ii) tillage with different intensities including conventional tillage with a mouldboard plough, reduced tillage with a chisel plough and no-tillage. The results showed that the plant-based management measure of cover cropping had only minor influence on near-saturated hydraulic conductivity (kh) and flow weighted mean pore radius (?m). Substantial over-winter changes were found with a significant increase in kh and a reduction in the pore radius. A spatial trend in soil texture along the cover cropped slope resulted in a higher kh at lower pressure heads at the summit with higher fractions of coarse particles, while kh tended to be highest at the toeslope towards saturation. Cover crop management accounted for a maximum of 9.7% of the total variability in kh, with a decreasing impact towards the unsaturated range. A substantial difference to bare soil in the cover cropped treatments could be identified in relation to a stabilization of macro-pores over winter. The different tillage treatments had a substantial impact on near-saturated kh and pore radius. Although conventional tillage showed the highest values in kh and ?m, settling of the soil after the ploughing event tended to reduce differences over time compared to the other tillage methods. The long-term no-tillage (10 years) however had the lowest values of kh at all measurement dates. The high contents of silt and fine sand probably resulted in soil densification that was not counterbalanced sufficiently by biological structure forming agents. The study could show that soil structure related hydraulic properties are subject to a substantial seasonal variability. A comprehensive assessment of agricultural measures such as tillage or cover cropping requires an estimate of these temporal dynamics and their interaction with the management strategies. Particularly for plant-based management measures such as cover cropping, which represent a less intense intervention in the structural states of the soil compared to tillage, this was evident, as the main mechanism revealed for this measure was structure stabilization over

Bodner, G.; Loiskandl, W.; Kaul, H.-P.

2009-04-01

59

Multiobjective Optimization of Effective Soil Hydraulic Properties on a Lysimeter from a Layered, Gravelly Vadose Zone  

NASA Astrophysics Data System (ADS)

Estimation of effective soil hydraulic parameters for characterization of the vadose zone properties is important for many applications from prediction of solute and pesticide transport to water balance modeling in small catchments. Inverse modeling has become a common approach to infer the parameters of the water retention and hydraulic conductivity functions from dynamic experiments under varying boundary conditions. To gain further inside into to the water transport behavior of an agricultural field site with a layered, gravelly vadose zone, a lysimeter was taken and equipped with a total of 48 sensors (24 tensiometers and 24 water content probes). The sensors were arranged in 6 vertical arrays consisting of 4 sensor pairs, respectively. Pressure heads and water contents were measured in four depths in each of the arrays allowing for the estimation of the soil hydraulic properties of the three individual soil layers by inverse modeling. For each of the soil horizons, a separate objective function was defined to fit the model to the observation. We used the global multiobjective multimethod search algorithm AMALGAM (Vrugt et al., 2007) in combination with the water flow and solute transport model Hydrus1D (Šimúnek et al., 2008) to estimate the soil hydraulic properties of the Mualem van Genuchten model (van Genuchten, 1980). This experimental design served for the investigation of two important questions: a) do effective soil hydraulic properties at the lysimeter scale exist, more specifically: can a single representative parameter set be found which describes the hydraulic behavior in each of the arrays with acceptable performance? And b) which degree of freedom is necessary or required for an accurate description of the one dimensional water flow at each of the arrays? Effective soil hydraulic parameters were obtained for each of the sensor arrays individually, resulting in good agreement between the model predictions and the observations for the individual soil horizons. However, no general parameter set could be identified to describe the integral water flow over all arrays with acceptable performance due to the high degree of horizontal heterogeneity within the soil horizons. Furthermore it is shown that some of the hydraulic parameters are well defined, while others are associated with high uncertainties, e.g. the saturated hydraulic conductivity and the residual water content. van Genuchten, M. Th., 1980: A closed form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal, 44, 892-898. Šimúnek, J., Šejna, M., Saito, H., Sakai, M. & van Genuchten, M. Th., 2008: The Hydrus-1D Software Package for Simulating the Movement of Water, Heat, and Multiple Solutes in Variably Saturated Media, Version 4.0, HYDRUS Software Series 3, Department of Environmental Sciences, University of California Riverside, Riverside, California, USA, pp. 315. Vrugt, J.A. and Robinson, B.A. 2007: Improved evolutionary optimization from genetically adaptive multimethod search, Proc. Nat. Acad. Sci. USA, 104, 708 - 711.

Werisch, Stefan; Lennartz, Franz

2013-04-01

60

Modeling the impacts of soil hydraulic properties on temporal stability of soil moisture under a semi-arid climate  

NASA Astrophysics Data System (ADS)

Despite the significant spatiotemporal variability of soil moisture, the phenomenon of temporal stability of soil moisture (TS SM) has been widely observed in field studies. However, the lack of understandings of the factors that control TS SM has led to some contradictory findings about TS SM. To resolve this issue, numerical models may offer an alternative way to complement field studies by quantifying different controls on TS SM. In this study, a 1-D vadose zone model was adopted to simulate daily soil moisture contents, which were used to compute the mean relative difference (MRD) and standard deviation of relative difference (SDRD) of soil moisture. Different from recent modeling studies, a soil dataset was employed with 200 samples of correlated soil hydraulic parameters for sandy soils. Compared to the results of previous modeling studies, more reasonable patterns of MRD and SDRD that resembled field observations were produced. By varying soil hydraulic parameter values, different patterns of MRD and SDRD could also be generated, implying variations in soil hydraulic properties could partly control the patterns of MRD and SDRD. More specifically, the residual soil moisture content (?r) was found to be the primary control on MRD, mainly due to the semi-arid climate that was simulated. By fixing ?r, however, a highly nonlinear relationship emerged between MRD and the shape factor n in the van Genuchten model, which resulted in the positively skewed distributions of MRD widely observed for sandy soils in field experiments. Moreover, both the range and skewness of the distributions of MRD were affected by the range of n. In addition, with increasing n, a positive correlation between MRD and the shape factor l in the van Genuchten model was also found. The simulation results suggested that the control of soil hydraulic properties on MRD might weaken for areas under bare surface conditions or for regions with more humid climates due to elevated soil moisture contents. Therefore, the impacts of soil hydraulic properties on TS SM may vary under different climate regimes.

Wang, Tiejun

2014-11-01

61

Development of soil hydraulic soil properties below ancient forest, planted forest and grassland  

NASA Astrophysics Data System (ADS)

A number of serious flood events in recent years have focused attention on flood prevention and mitigation and modelling work suggests that climate change will lead to an increase in the intensity and frequency of flood events in many areas. To understand how soil hydraulic characteristics develops in relation to facilitating the infiltration and storage of storm rainfall, a hypothetical pedogensis sequence was first developed and then tested by investigating a grassland site and four Scots pine (Pinus sylvestris) forests of different ages in the Scottish Highlands. These sites are: grassland, six and 45 year-old Scots pine plantations, remnant 300 year old individual Scots pines and a 4000 year old Caledonian Forest. The soil characteristics measured were: field saturated hydraulic conductivity (Kfs) using a constant head well permeameter, root numbers and proportion were estimated from soil pits and soil cores were taken for three different soil depths (0.06 - 0.10, 0.16 - 0.20 and 0.26 to 0.40m) for laboratory measurements to estimate organic matter, soil water release curves, macro-pores, and X - ray tomography measured pore connectivity and soil pore structure. It was observed that cutting down of the plantation increased organic matter because of the increase of dead biomass and decreased pore connectivity, which resulted in reduced hydraulic conductivity during the early years of re-afforestation. Where older trees were left, after cutting and removing younger trees; the range of OM, hydraulic conductivity, pore connectivity, and macropores remained similar to and older Scots pine plantation (45 years old). The undisturbed Ancient Caledonian remnant forest (approximately 4000 years old) was observed to have remarkably heterogeneous soil characteristics, providing extreme values of Kfs (12 to 4992 mm hr-1), OM, and macropores. Such ranges of soil characteristics were considered to be the optimum to reduce local flooding, because the soil matrix could transport high intensity storm rainfall and re-direct storm rainfall to deeper layers and the presence of micropores and larger quantity of OM provides a greater area to store. This combination of soil characteristics would slow down the flow of rainfall to ground water reservoirs and rivers and reduce flood peaks.

Archer, Nicole; Otten, Wilfred; Schmidt, Sonja; Bengough, Glyn; Bonell, Mike; Shah, Nadeem

2014-05-01

62

Vegetation controls on soil hydraulic properties and implications for the hydrologic variability of soils: observations and modeling  

NASA Astrophysics Data System (ADS)

Soil properties and their associated spatial structure exert major controls on the storage and fluxes of water through surface soils and provide habitat and resources for life in the critical zone. Moreover it has been observed that a range of biotic processes are responsible for the formation and maintenance of these properties. For instance the build up of organic matter in soils can affect the water retention properties, particularly in coarse soils. This observation leads to the compelling possibility that the action of vegetation on its soil environment alters the hydrologic variability of soil, with consequences (positive and negative) for plant functions. This alteration was examined in four semi-arid ecosystems in southern Arizona using a combination of field data collection and modeling. It was expected that the extent and direction of biotic alteration would be dependent on the other factors determining soil formation, particularly the climate, lithology and landscape position. Controlling for the latter of these, soil samples were collected in the mid-slope sections of four north-facing hillslopes encompassing two lithologies and two climates. The effects of vegetation were examined by collecting paired samples from below and between woody-plant canopies. Samples were analyzed for their composition and hydraulic properties, including organic matter content, water retention, and permeability. The results demonstrate that the build-up of organic matter under vegetation can significantly alter soil hydraulic properties over small spatial scales. The effects of this alteration on the hydrologic variability of the soils, and the implications for vegetation water stress and nutrient cycling, will be examined using a simple model of soil-plant-atmosphere interactions.

Harman, C. J.; Lohse, K. A.; Troch, P. A.; Sivapalan, M.

2010-12-01

63

Laboratory evaporation experiments in undisturbed peat columns for determining peat soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Knowledge about hydraulic properties of organic soils is crucial for the interpretation of the hydrological situation in peatlands. This in turn is the basis for designing optimal rewetting strategies, for assessing the current and future climatic water balance and for quantifying greenhouse gas emissions of CO2, CH4 and N2O, which are strongly controlled by the depth of the peat water table. In contrast to mineral soils, the hydraulic properties of organic soils differ in several aspects. Due to the high amount of organic components, strong heterogeneity, and shrinkage and swelling of peat, accompanied by changing soil volume and bulk density, the applicability of standard hydraulic functions developed for mineral soils for describing peat soil moisture dynamics is often questioned. Hence, the objective of this study was to investigate the applicability of the commonly applied van Genuchten-Mualem (VGM) parameterization and to evaluate model errors for various peat types. Laboratory column experiments with undisturbed peat soils (diameter: 30 cm, height: 20 cm) from 5 different peatlands in Germany were conducted. In numerical simulations using HYDRUS-1D the experimental data were used for an inverse estimation of the soil hydraulic parameters. Using the VGM parameterization, the model errors between observed and measured pressure heads were quantified with a root mean square error (RMSE) of 20 - 65 cm. The RMSE increased for soils with higher organic carbon content and higher porosity. Optimizing the VGM 'tortuosity' parameter (?) instead of fixing it to its default of 0.5 strongly reduced the RMSE, especially for the soils that showed high pressure head gradients during the experiment. Due to the fact, that very negative pressure heads in peatlands occur rarely, we reduced the range of pressured heads in the inversion to a 'field-relevant' range from 0 to -200 cm which strongly reduced the RMSE to 6 - 12 cm and makes the VGM parameterization applicable for all investigated peat soils. For the field-relevant scale, especially for very wet conditions, we demonstrate the importance of macro-pores by using a simple macro-pore approach, with only 1 additional parameter, i.e. the macro-pore fraction, which strongly reduced the RMSE down to 1 - 7 cm. Since ? has not been identified as an important parameter for the field-relevant range, only 5 parameters were optimized in this approach. This keeps the derivation of the parameters manageable and thus provides a model that is applicable to practical issues.

Dettmann, U.; Frahm, E.; Bechtold, M.

2013-12-01

64

Linking hydraulic properties of fire-affected soils to infiltration and water repellency  

USGS Publications Warehouse

Heat from wildfires can produce a two-layer system composed of extremely dry soil covered by a layer of ash, which when subjected to rainfall, may produce extreme floods. To understand the soil physics controlling runoff for these initial conditions, we used a small, portable disk infiltrometer to measure two hydraulic properties: (1) near-saturated hydraulic conductivity, Kf and (2) sorptivity, S(??i), as a function of initial soil moisture content, ??i, ranging from extremely dry conditions (??i < 0.02 cm3 cm-3) to near saturation. In the field and in the laboratory replicate measurements were made of ash, reference soils, soils unaffected by fire, and fire-affected soils. Each has a different degrees of water repellency that influences Kf and S(??i). Values of Kf ranged from 4.5 ?? 10-3 to 53 ?? 10-3 cm s-1 for ash; from 0.93 ?? 10-3 to 130 ?? 10-3 cm s-1 for reference soils; and from 0.86 ?? 10-3 to 3.0 ?? 10-3 cm s-1, for soil unaffected by fire, which had the lowest values of Kf. Measurements indicated that S(??i) could be represented by an empirical non-linear function of ??i with a sorptivity maximum of 0.18-0.20 cm s-0.5, between 0.03 and 0.08 cm3 cm-3. This functional form differs from the monotonically decreasing non-linear functions often used to represent S(??i) for rainfall-runoff modeling. The sorptivity maximum may represent the combined effects of gravity, capillarity, and adsorption in a transitional domain corresponding to extremely dry soil, and moreover, it may explain the observed non-linear behavior, and the critical soil-moisture threshold of water repellent soils. Laboratory measurements of Kf and S(??i) are the first for ash and fire-affected soil, but additional measurements are needed of these hydraulic properties for in situ fire-affected soils. They provide insight into water repellency behavior and infiltration under extremely dry conditions. Most importantly, they indicate how existing rainfall-runoff models can be modified to accommodate a possible two-layer system in extremely dry conditions. These modified models can be used to predict floods from burned watersheds under these initial conditions.

Moody, J.A.; Kinner, D.A.; Ubeda, X.

2009-01-01

65

Relation between hydraulic properties and plant coverage of the closed-landfill soils in Piacenza (Po Valley, Italy)  

NASA Astrophysics Data System (ADS)

In this paper the results of a study of soil hydraulic properties and plant coverage of a landfill located in Piacenza (Po Valley, Italy) are presented, together with the attempt to put the hydraulic properties in relation with plant coverage. The measured soil water retention curve was first compared with the output of some pedotransfer functions taken from the literature and then with the output of the same pedotransfer functions applied to a reference soil. The landfill plant coverage was also studied. The relation between soil hydraulic properties and plant coverage showed that the landfill soils have a low water content available for plants and this fact, together with their lack of depth and compacted structure, justifies the presence of a nitrophilous, disturbed-soil vegetation type, dominated by ephemeral annual species (therophytes).

Cassinari, C.; Manfredi, P.; Giupponi, L.; Trevisan, M.; Piccini, C.

2015-02-01

66

Modeling biofilm dynamics and hydraulic properties in variably saturated soils using a channel network model  

NASA Astrophysics Data System (ADS)

Biofilm effects on water flow in unsaturated environments have largely been ignored in the past. However, intensive engineered systems that involve elevated organic loads such as wastewater irrigation, effluent recharge, and bioremediation processes make understanding how biofilms affect flow highly important. In the current work, we present a channel-network model that incorporates water flow, substrate transport, and biofilm dynamics to simulate the alteration of soil hydraulic properties, namely water retention and conductivity. The change in hydraulic properties due to biofilm growth is not trivial and depends highly on the spatial distribution of the biofilm development. Our results indicate that the substrate mass transfer coefficient across the water-biofilm interface dominates the spatiotemporal distribution of biofilm. High mass transfer coefficients lead to uncontrolled biofilm growth close to the substrate source, resulting in preferential clogging of the soil. Low mass transfer coefficients, on the other hand, lead to a more uniform biofilm distribution. The first scenario leads to a dramatic reduction of the hydraulic conductivity with almost no change in water retention, whereas the second scenario has a smaller effect on conductivity but a larger influence on retention. The current modeling approach identifies key factors that still need to be studied and opens the way for simulation and optimization of processes involving significant biological activity in unsaturated soils.

Rosenzweig, Ravid; Furman, Alex; Dosoretz, Carlos; Shavit, Uri

2014-07-01

67

An updated treatment of soil texture and associated hydraulic properties in a global land modeling system  

NASA Astrophysics Data System (ADS)

The advent of new data sets describing soil texture and associated soil properties offers the promise of improved hydrological simulation. Here we describe the composition of a new soil texture data set and its implementation into a specific land surface modeling system, namely, the Catchment land surface model (LSM) of the NASA Goddard Earth Observing System version 5 (GEOS-5) modeling and assimilation framework. First, global soil texture composites are generated using data from the Harmonized World Soil Database version 1.21 (HWSD1.21) and the State Soil Geographic (STATSGO2) project, with explicit consideration of different levels of organic material. Then, the LSM's soil parameters are upgraded using the new texture data, with hydraulic parameters derived for the more extensive set of texture classes using pedotransfer functions. Other changes to the LSM parameters are included to further support simulations at increasingly fine resolutions. A suite of simulations with the original and new parameter versions shows modest yet significant improvements in the Catchment LSM's simulation of soil moisture and surface hydrological fluxes. The revised LSM parameters will be used for the forthcoming Soil Moisture Active Passive (SMAP) soil moisture assimilation product.

De Lannoy, Gabriëlle J. M.; Koster, Randal D.; Reichle, Rolf H.; Mahanama, Sarith P. P.; Liu, Qing

2014-12-01

68

Water flow path interactions with soil hydraulic properties in till soil at Gårdsjön, Sweden  

NASA Astrophysics Data System (ADS)

In 1989, in a hydrological research programme within a deacidification project in the Gårdsjön area in southwest Sweden, flow paths and residence times of soil water and groundwater in microcatchments were examined to support the interpretation of the hydrochemical changes. Saturated hydraulic conductivity and soil water retention were analysed on more than 100 cylinder samples. The catchments have shallow sandy-silty till soil with a mean depth in the main catchment of 43 cm. Porosity of the mineral soil in the main catchment was high and ranged from 38 to 85%. The samples from the B-horizon had generally higher porosity. Porosity and the content of organic matter were correlated. The soil water retention was relatively high at all tensions, likely owing to the high content of organic matter. Dissolved organic substances were most probably transported from the shallow soil on the steep sides of the catchment down to the valley where it precipitated. The high porosities could be a consequence of long-term weathering, provided that the organic substances present have increased the leaching of the weathering products. Measured values of saturated hydraulic conductivity were close to log-normally distributed with a mean for all samples of 3 × 10 -5 m s -1. There was a significant increase in conductivity toward the ground surface with the mean conductivity of the samples in the uppermost 10 cm of the mineral soil of 4 × 10 -5 m s -1, which was about 13 times higher than the conductivity of 3 × 10 -6 m s -1 at 1 m depth. From the relationship between runoff at the catchment outlet and groundwater levels, the conductivity was estimated to be 15-200 times higher in the upper soil layer than in the deeper ones. In one profile, 44-64% of the yearly lateral flow was estimated to occur above 30 cm depth. The conductivity was correlated with the content of drainable water, which indicated the importance of the largest pores for the saturated hydraulic conductivity.

Nyberg, Lars

1995-08-01

69

Measurement of Physical and Hydraulic Properties of Organic Soil Using Computed Tomographic Imagery  

NASA Astrophysics Data System (ADS)

The Lower Liard River valley is located within the continental northern boreal region and the zone of discontinuous permafrost. Lying in the centre of the Mackenzie basin, this valley is an extensive flat headwater region with a high density of open water and peatlands. Several standard methods of measuring the physical properties of organic soils exist, although many of them have several drawbacks that limit their use. Organic soils, in particular, have unique properties that require special attention to ensure that the measured hydrological characteristics are represented as they exist in nature. The goal of this research was to devise an improved method of analyzing and measuring the physical and hydraulic properties of organic soil using MicroCT imagery. Specifically, this research seeks to determine if two and three-dimensional images of peat can be used to accurately characterize air-filled porosity, active porosity, pore size distribution, pore saturated area and capillarity of porous Sphagnum cells. Results indicate that measurements derived from these images are consistent with current literature. They also suggest that this non-destructive method is a valuable tool for measuring peat physical and hydraulic properties and that there is potential for additional research using CT technology.

Blais, K. E.; Quinton, W. L.; Heck, R. J.; Price, J. S.; Schmidt, M. G.

2005-12-01

70

Changes in soil hydraulic properties caused by construction of a simulated waste trench at the Idaho National Engineering Laboratory, Idaho  

USGS Publications Warehouse

In order to assess the effect of filled waste disposal trenches on transport-governing soil properties, comparisons were made between profiles of undisturbed soil and disturbed soil in a simulated waste trench. The changes in soil properties induced by the construction of a simulated waste trench were measured near the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory (INEL) in the semi-arid southeast region of Idaho. The soil samples were collected, using a hydraulically- driven sampler to minimize sample disruption, from both a simulated waste trench and an undisturbed area nearby. Results show that the undisturbed profile has distinct layers whose properties differ significantly, whereas the soil profile in the simulated waste trench is. by comparison, homogeneous. Porosity was increased in the disturbed cores, and, correspondingly, saturated hydraulic conductivities were on average three times higher. With higher soil-moisture contents (greater than 0.32), unsaturated hydraulic conductivities for the undisturbed cores were typically greater than those for the disturbed cores. With lower moisture contents, most of the disturbed cores had greater hydraulic conductivities. The observed differences in hydraulic conductivities are interpreted and discussed as changes in the soil pore geometry.

Shakofsky, S.M.

1995-01-01

71

Changes in soil hydraulic properties caused by construction of a simulated waste trench at the Idaho National Engineering Laboratory, Idaho  

SciTech Connect

In order to assess the effect of filled waste disposal trenches on transport-governing soil properties, comparisons were made between profiles of undisturbed soil and disturbed soil in a simulated waste trench. The changes in soil properties induced by the construction of a simulated waste trench were measured near the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory (INEL) in the semiarid southeast region of Idaho. The soil samples were collected, using a hydraulically-driven sampler to minimize sample disruption, from both a simulated waste trench and an undisturbed area nearby. Results show that the undisturbed profile has distinct layers whose properties differ significantly, whereas the soil profile in the simulated waste trench is, by comparison, homogeneous. Porosity was increased in the disturbed cores, and, correspondingly, saturated hydraulic conductivities were on average three times higher. With higher soil-moisture contents (greater than 0.32), unsaturated hydraulic conductivities for the undisturbed cores were typically greater than those for the disturbed cores. With lower moisture contents, most of the disturbed cores had greater hydraulic conductivities. The observed differences in hydraulic conductivities are interpreted and discussed as changes in the soil pore geometry.

Shakofsky, S.

1995-03-01

72

Impact of anthropomorphic soil genesis on hydraulic properties: the case of cranberry production  

NASA Astrophysics Data System (ADS)

The construction of a cranberry field requires the installation of a drainage system which causes anthropic layering of the natural sequence of soil strata. Over the years, the soil hydraulic properties may change under the influence of irrigation and water table control. In fact, natural consolidation (drainage and recharge cycles), filtration and clogging soil pores by colloidal particle accelerated by water management will alter the hydrodynamic behavior of the soil (Gaillard et al., 2007; Wildenschild and Sheppard, 2013; Bodner et al., 2013). Today, advances in the field of tomography imagery allows the study a number of physicals processes of soils (Wildenschilds and Sheppard, 2013) especially for the transport of colloidal particles (Gaillard et al., 2007) and consolidation (Reed et al, 2006; Pires et al, 2007). Therefore, the main objective of this work is to analyze the temporal evolution of hydrodynamic properties of a sandy soil during repeated drainage and recharge cycles using a medical CT-scan. A soil columns laboratory experiment was setup in fall 2013, pressure head, input and output flow, tracer monitoring (KBr and ZrO2) and tomographic analyses have been used to quantify the temporal variation of the soil hydrodynamic properties of these soil columns. The results showed that the water management (irrigation and drainage) has strong effect on soil genesis and causes significant alteration of soil hydraulic properties, which may reduce soil drainage capacity. Knowledge about the mechanisms responsible of anthropic cranberry soil genesis will allow us to predict soil evolution according to several conditions (soil type, drainage system design, water management) to better anticipate and control their future negative effects on cranberry production. References: Bodner, G., P. Scholl and H.P. Kaul. 2013. Field quantification of wetting-drying cycles to predict temporal changes of soil pore size distribution. Soil and Tillage Research 133: 1-9. doi:http://dx.doi.org/10.1016/j.still.2013.05.006. Gaillard, J.-F., C. Chen, S.H. Stonedahl, B.L.T. Lau, D.T. Keane and A.I. Packman. 2007. Imaging of colloidal deposits in granular porous media by X-ray difference micro-tomography. Geophysical Research Letters 34: L18404. doi:10.1029/2007GL030514. Pires, L.F., O.O.S. Bacchi and K. Reichardt. 2007. Assessment of soil structure repair due to wetting and drying cycles through 2D tomographic image analysis. Soil and Tillage Research 94: 537-545. doi:http://dx.doi.org/10.1016/j.still.2006.10.008. Reed, A. H., Thompson, K. E., Zhang, W., Willson, C. S., & Briggs, K. B. (2006). Quantifying consolidation and reordering in natural granular media from computed tomography images. Advances in X-ray Tomography for Geomaterials, 263-268. Wildenschild, D. and A.P. Sheppard. 2013. X-ray imaging and analysis techniques for quantifying pore-scale structure and processes in subsurface porous medium systems. Advances in Water Resources 51: 217-246. doi:http://dx.doi.org/10.1016/j.advwatres.2012.07.018.

Periard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean; Hallema, Dennis W.

2014-05-01

73

Time-lapse Ground-Penetrating Radar for Deriving Soil Hydraulic Properties  

NASA Astrophysics Data System (ADS)

A profound understanding of subsurface hydrological processes demands a detailed description of hydraulic parameter distributions at the pertinent scale of interest. However, characterizing soil hydraulic properties remains a challenge, especially for field scale studies. Accurate high-resolution GPR measurements of soil water dynamics have shown promise to alleviate this challenge. In recent years, ASSESS-GPR, a field scale test site for advancing Ground-Penetrating Radar methods has been successfully established in Heidelberg (e.g., Buchner et al, 2012 or Klenk, 2012). Permanently installed TDR sensor profiles allow for an independent, corroborating dataset which can serve as basis for hydrologic modeling. In such a well-controlled experimental setup, we can achieve a very high relative precision for non-invasively monitoring soil water dynamics with GPR (Klenk, 2012). We can furthermore study the dynamics of the capillary fringe in different materials through time-lapse GPR measurements during pumping experiments. For example, as Dagenbach et al (2013) have shown, information can be gained about the appropriate form of a hydraulic parameterization. We here expand on these previous works by presenting a set of experiments, where the water table has been raised and subsequently lowered in a multi-step fashion over the course of several days. We discuss the non-invasive, high-resolution monitoring of the corresponding subsurface water dynamics by time-lapse GPR and thoroughly assess potentials for deriving hydraulic parameters for the different materials through electromagnetic modeling of the GPR response for said materials under the measured forcing.

Klenk, Patrick; Jaumann, Stefan; Roth, Kurt

2014-05-01

74

Use of LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils  

NASA Technical Reports Server (NTRS)

The estimation of the spatially variable surface moisture and heat fluxes of natural, semivegetated landscapes is difficult due to the highly random nature of the vegetation (e.g., plant species, density, and stress) and the soil (e.g., moisture content, and soil hydraulic conductivity). The solution to that problem lies, in part, in the use of satellite remotely sensed data, and in the preparation of those data in terms of the physical properties of the plant and soil. The work was focused on the development and testing of a stochastic geometric canopy-soil reflectance model, which can be applied to the physically-based interpretation of LANDSAT images. The model conceptualizes the landscape as a stochastic surface with bulk plant and soil reflective properties. The model is particularly suited for regional scale investigations where the quantification of the bulk landscape properties, such as fractional vegetation cover, is important on a pixel by pixel basis. A summary of the theoretical analysis and the preliminary testing of the model with actual aerial radiometric data is provided.

Eagleson, Peter S.; Jasinski, Michael F.

1988-01-01

75

Assessing Tillage Effects on Soil Hydraulic Properties via Inverse Parameter Estimation using Tension Infiltrometry  

NASA Astrophysics Data System (ADS)

Hydraulic properties are key factors controlling water and solute movement in soils. While several recent studies have focused on the assessment of the spatial variability of hydraulic properties, the temporal dynamics are commonly not taken into account, primarily because its measurement is costly and time-consuming. However, there is extensive empirical evidence that these properties are subject to temporal changes, particularly in the near-saturated range where soil structure strongly influences water flow. One main source of temporal variability is soil tillage. It can improve macroporosity by loosening the soil and thereby changing the pore-size distribution. Since these modifications are quite unstable over time, the pore space partially collapses after tillage. This effect should be largest for conventional tillage (CT), where the soil is ploughed after harvest every year. Assessing the effect of different tillage treatments on the temporal variability of hydraulic properties requires adequate measurement techniques. Tension infiltrometry has become a popular and convenient method providing not only the hydraulic conductivity function but also the soil rentention properties. The inverse estimation of parameters from infiltration measurements remains challenging, despite some progress since the first approach of Šimůnek et al. (1998). Measured data like the cumulative infiltration, the initial and final volumetric water content, as well as independently measured retention data from soil core analysis with laboratory methods, have to be considered to find an optimum solution describing the soil's pore space. In the present study we analysed tension infiltration measurements obtained several times between August 2008 and December 2009 on an arable field in the Moravian Basin, Lower Austria. The tillage treatments were conventional tillage including ploughing (CT), reduced tillage with chisel only (RT), and no-tillage treatment using a direct seeding technique (NT). Infiltration measurements were supplemented by retention data for dryer conditions (-10 to -300 kPa) as determined by pressure plate extraction on steel core samples. The HYDRUS 2D/3D software package was used to inversely fit the parameters of suitable soil retention models to the data. Beside the most common model of Van Genuchten (1978), we also assessed the lognormal distribution model proposed by Kosugi (1994) and the dual porosity approach of Durner (1994). We will show that a dual porosity model best fits the infiltration data. It allows the retention curve to account for both the cumulative infiltration (structure-controlled flow) as well as the measured retention data points (texture-controlled flow). The pressure plate extraction data are used to determine one of the shape-determining parameter sets of the model equation. As the tillage effect on the temporal variability is expected to be negligible for texture-controlled water flow, these parameters are set constant with time for each tillage treatment. All remaining model parameters were inversely determined by the infiltration data. The advantage of a bimodal retention model is greatest when macropores strongly contribute to water movement. This can be observed especially under conventional tillage, where a strong increase of macropores is caused by annual ploughing, but also for reduced (oder minimum) tillage treatments, where biopores from earthworm burrows and dead plant roots increase macropore flow.

Schwen, Andreas; Bodner, Gernot; Loiskandl, Willibald

2010-05-01

76

A Comparison of Land Surface Model Soil Hydraulic Properties Estimated by Inverse Modeling and Pedotransfer Functions  

NASA Technical Reports Server (NTRS)

Soil hydraulic properties (SHPs) regulate the movement of water in the soil. This in turn plays an important role in the water and energy cycles at the land surface. At present, SHPS are commonly defined by a simple pedotransfer function from soil texture class, but SHPs vary more within a texture class than between classes. To examine the impact of using soil texture class to predict SHPS, we run the Noah land surface model for a wide variety of measured SHPs. We find that across a range of vegetation cover (5 - 80% cover) and climates (250 - 900 mm mean annual precipitation), soil texture class only explains 5% of the variance expected from the real distribution of SHPs. We then show that modifying SHPs can drastically improve model performance. We compare two methods of estimating SHPs: (1) inverse method, and (2) soil texture class. Compared to texture class, inverse modeling reduces errors between measured and modeled latent heat flux from 88 to 28 w/m(exp 2). Additionally we find that with increasing vegetation cover the importance of SHPs decreases and that the van Genuchten m parameter becomes less important, while the saturated conductivity becomes more important.

Gutmann, Ethan D.; Small, Eric E.

2007-01-01

77

Deep rooting plants influence on soil hydraulic properties and air conductivity over time  

NASA Astrophysics Data System (ADS)

Crop sequences are commonly suggested as an alternative to improve subsoil structure. A well structured soil can be characterized by enhanced transport properties. Our main hypothesis was, that different root systems can modify the soil's macro/mesopore network if enough cultivation time is given. We analyzed the influence of three crops with either shallower roots (Festuca arundinacea, fescue) or taproots (Cichorium intybus, chicory and Medicago sativa, alfalfa). The crops where cultivated on a Haplic Luvisol near Bonn (Germany) for one, two or three years. Undisturbed soil cores were taken for measurement of unsaturated hydraulic conductivity and air permeability. The unsaturated conductivity was measured using the evaporation method, monitoring the water content and tension at two depths of each undisturbed soil core. The van Genuchten-Mualem model (1991) was fitted to the measured data. Air permeability was measured in a permeameter with constant flow at low pressure gradient. The measurements were repeated at -1, -3, -6, -15, -30 and -50 kPa matric tension and the model of Ball et al. (1988) was used to describe permeability as function of matric tension. Furthermore, the cores equilibrated at -15 kPa matric tension were scanned with X-Ray computer tomography. By means of 3D image analysis, geometrical features as pore size distribution, tortuosity and connectivity of the pore network was analyzed. The measurements showed an increased unsaturated hydraulic conductivity associated to coarser pores at the taprooted cultivations. A enhanced pore system (related to shrink-swell processes) under alfalfa was observed in both transport measurements and was confirmed by the 3D image analysis. This highly functional pore system (consisting mainly of root paths, earthworm channels and shrinking cracks) was clearly visible below the 75 cm of depth and differentiated significantly from the other two treatments only after three years of cultivation, which shows the time needed to modify soil structure under these conditions.

Uteau, Daniel; Peth, Stephan; Diercks, Charlotte; Pagenkemper, Sebastian; Horn, Rainer

2014-05-01

78

Variation of surficial soil hydraulic properties across land uses in the southern Blue Ridge Mountains, North Carolina, USA  

Microsoft Academic Search

summary A full understanding of hydrologic response to human impact requires assessment of land-use impacts on key soil physical properties such as saturated hydraulic conductivity, bulk density, and moisture reten- tion. Such properties have been shown to affect watershed hydrology by influencing pathways and trans- mission rates of precipitation to stream networks. Human land use has been shown to influence

Katie Price; C. Rhett Jackson; Albert J. Parker

2010-01-01

79

An easily installable groundwater lysimeter to determine water balance components and hydraulic properties of peat soils Hydrology and Earth System Sciences, 7(1), 2332 (2003) EGU  

E-print Network

installable groundwater lysimeter to determine water balance components and hydraulic properties of peat soils. Moreover, they should allow the in situ determination of the hydraulic properties (water retentionAn easily installable groundwater lysimeter to determine water balance components and hydraulic

Boyer, Edmond

2003-01-01

80

Estimation of Effective Soil Hydraulic Properties Using Multi-Temporal Remote Sensing Data and Regional Inverse Modeling  

NASA Astrophysics Data System (ADS)

Soil moisture is known to significantly influence atmospheric boundary layer, cloud and precipitation predictions. This influence is one of the key justifications for deriving soil moisture initial conditions from offline land data assimilation systems. However, poor global knowledge of land-surface soil parameters is one of the key limits to our ability to accurately predict soil moisture. Soil hydraulic properties (hydraulic conductivity, water retention) are by far the most important land surface parameters to govern the partitioning of soil moisture between infiltration and evaporation fluxes at a range of spatial scales. However, an obstacle to their practical application in the field, catchment, watershed, or regional scale is the difficulty of quantifying the "effective" soil hydraulic functions (h) and K(h), where is the soil water, h is the pressure head and K is unsaturated hydraulic conductivity. Proper evaluation of the water balance near the land-atmosphere boundary depends strongly on appropriate characterization of soil hydraulic parameters under field conditions and at the appropriate process scale. Traditionally, process representation in the vadose zone is derived at the pore-scale and later extrapolated to larger scale without proper representation of and accounting for nonlinearity across space and time scales. With the deployment of MODIS and AQUA-E on TERRA and AQUA satellites that collect near-daily evolution of land cover parameters, states and fluxes as well as surface soil moisture on a global scale opens up a new avenue to quantify this critical land surface parameter. We will present a novel scheme to derive "effective" soil hydraulic properties at various remote sensing footprint resolutions by integrating multi-temporal remote sensing data of evapotranspiration and soil moisture, a land surface/vadose zone hydrologic model, and a suite of advanced inverse modeling algorithms such as Genetic Algorithms. We will test our proposed inverse modeling (top-down) approach at three hydro-climatic regions of Iowa, Oklahoma, and Arizona using developed upscaling (bottom-up) approach where supplemental air-borne and ground data are available during the SGP and SMEX field campaigns. Determining "effective" land surface soil hydraulic properties from global satellite remote sensing data opens up a new paradigm and will have tremendous impacts on our ability to predict terrestrial hydrology, weather, climate, and global circulation of water, energy, and chemicals in the environment.

Mohanty, B. P.; Ines, A. V.

2005-12-01

81

Soil hydraulic conductivity as affected by physical and chemical properties of effluents  

E-print Network

-chemical factors which may cause reduction in soil hydraulic conductivity (K!,) upon land disposal of sewage. Additional key words: Sewage water, physical plugging, suspended solids, polyvalent cations binding, sodium disposal has been explained in different ways. The clogging of soils has often been attributed

Paris-Sud XI, Université de

82

Effects of spatial variability of soil hydraulic properties in water budget modeling  

Microsoft Academic Search

There is appreciable spatial variability of soil properties on the scale of a watershed or a field even in a single soil type. The spatial variation of soil water characteristics in an area was simulated from average properties and the assumption of scale heterogeneity (Philip, 1967). Simulated soil water characteristics and other data representing forest vegetation were used in a

A. J. Peck; R. J. Luxmoore; Janice L. Stolzy

1977-01-01

83

Feasibility of using LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils  

NASA Technical Reports Server (NTRS)

Research activities conducted from February 1, 1985 to July 31, 1985 and preliminary conclusions regarding research objectives are summarized. The objective is to determine the feasibility of using LANDSAT data to estimate effective hydraulic properties of soils. The general approach is to apply the climatic-climax hypothesis (Ealgeson, 1982) to natural water-limited vegetation systems using canopy cover estimated from LANDSAT data. Natural water-limited systems typically consist of inhomogeneous vegetation canopies interspersed with bare soils. The ground resolution associated with one pixel from LANDSAT MSS (or TM) data is generally greater than the scale of the plant canopy or canopy clusters. Thus a method for resolving percent canopy cover at a subpixel level must be established before the Eagleson hypothesis can be tested. Two formulations are proposed which extend existing methods of analyzing mixed pixels to naturally vegetated landscapes. The first method involves use of the normalized vegetation index. The second approach is a physical model based on radiative transfer principles. Both methods are to be analyzed for their feasibility on selected sites.

Eagleson, P. S.

1985-01-01

84

Using pedotransfer functions to estimate the van Genuchten-Mualem soil hydraulic properties: A review  

Technology Transfer Automated Retrieval System (TEKTRAN)

In this paper, we review the use of the van Genuchten Mualem (VGM) model to parameterize the soil moisture retention characteristic (MRC) and the nsaturated hydraulic conductivity curve (HCC), as well as its use in developing pedotransfer functions (PFTs). Analysis of literature data showed that MRC...

85

Unsaturated hydraulic conductivity function based on a soil fragmentation process  

E-print Network

Unsaturated hydraulic conductivity function based on a soil fragmentation process Shmuel Assouline-parameter expression for relative hydraulic conductivity (RHC) of partially saturated soils. It is based on the premise. This assumption allows us to derive hydraulic properties of soils (water retention curves and unsaturated

Tartakovsky, Daniel M.

86

Variation of surficial soil hydraulic properties across land uses in the southern Blue Ridge Mountains, North Carolina, USA  

NASA Astrophysics Data System (ADS)

SummaryA full understanding of hydrologic response to human impact requires assessment of land-use impacts on key soil physical properties such as saturated hydraulic conductivity, bulk density, and moisture retention. Such properties have been shown to affect watershed hydrology by influencing pathways and transmission rates of precipitation to stream networks. Human land use has been shown to influence these soil physical properties as a result of erosion, compaction, and pore structure evolution. Our objective was to characterize soil physical properties under three land-use classes (forest, pasture, and managed lawn) in the southern Blue Ridge Mountains of southwestern North Carolina. A total of 90 points were sampled (30 in each land-use class) throughout a 983 km 2 study area. Saprolitic and alluvial soils were emphasized, and sites were selected that showed consistent land-use history over a period of at least 30 years. Particle size distribution, in situ saturated hydraulic conductivity (measured using an Amoozemeter compact constant head permeameter), bulk density, and volumetric moisture content at field capacity were measured at each point. Forest soils demonstrated markedly lower bulk densities and higher infiltration rates, and water holding capacities, than lawn and pasture soils. No soil property significantly differed between pasture and lawn. Mean values for each property were as follows (forest = F, lawn = L, pasture = P): saturated hydraulic conductivity (mm h -1) - F = 63, L = 7, P = 8; bulk density (g cm -3) - F = 0.8, L = 1.2, P = 1.2; volumetric moisture content (%) - F = 72%, L = 42%, P = 39%. Particle size distributions did not significantly differ among land-use classes or parent materials, and the differences between the hydraulic properties of forest vs. nonforest soils were attributed to compaction associated with land management practices. The magnitudes of differences between forest and nonforest infiltration rates suggest that widespread conversion of forest to other land uses in this region will be accompanied by decreased infiltration and increased overland flow, potentially significantly altering water budgets and leading to reduced baseflows and impaired water quality.

Price, Katie; Jackson, C. Rhett; Parker, Albert J.

2010-03-01

87

Laboratory analysis of soil hydraulic properties of G-5 soil samples  

SciTech Connect

The Hydrologic Testing Laboratory at DBS&A has completed laboratory tests on TA-54 samples from well G5 as specified by Daniel James and summarized in Table 1. Tables 2 through 8 give the results of the specified analyses. Raw laboratory data and graphical plots of data (where appropriate) are contained in Appendices A through G. Appendix H lists the methods used in these analyses. A detailed description of each method is available upon request. Several sample-specific observations are important for data interpretation. Sample G-5 @ 21.5 was a short core and showed indications of preferential flow. Sample G-5 @ 92.5 developed a visually apparent crack during drying which correlates with the higher air permeabilities observed at lower water contents. Several samples yielded negative estimates of extrapolated intrinsic permeability while measured apparent permeabilities were reasonable. For consistency, however, only intrinsic values are presented. While our defined task is to provide data for interpretation, the following comments are offered as a context for some of the common parameter extraction issues. Further details and a more comprehensive summary of TA-54 data can be found in Unsaturated hydraulic characteristics of the Bandelier tuff at TA-54 dated November 17, 1994.

NONE

1995-01-01

88

Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils  

NASA Astrophysics Data System (ADS)

The effects of saturation degree (or capillary pressure) on hydraulic conductivity anisotropy in unsaturated soils have not been fully understood. This study developed an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore the capillary pressure-dependent anisotropy in relation to soil texture and soil bulk density. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the mean particle diameter. When only one hydraulic parameter is related to the grain diameter or when both are not related to the same attribute simultaneously, the unsaturated soil anisotropy increases monotonically with the increasing capillary pressure head. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The correlation between the soil grain diameter and bulk density decreases the anisotropy effects of the unsaturated layered soils. The study illustrates that the inter-relationships of soil texture, bulk density, and hydraulic properties may cause vastly different characteristics of anisotropic unsaturated soils.

Sun, Dongmin; Zhu, Jianting

2010-05-01

89

TRANSLATING AVAILABLE BASIC SOIL DATA INTO MISSING SOIL HYDRAULIC CHARACTERISTICS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil hydraulic pedotransfer functions transfer simple-to-measure soil survey information into soil hydraulic characteristics, that are otherwise costly to measure. Examples are presented of different equations describing hydraulic characteristics and of pedotransfer functions used to predict paramet...

90

Organic Carbon Effects on Soil Physical and Hydraulic Properties in a Semi-arid Climate  

Technology Transfer Automated Retrieval System (TEKTRAN)

Increasing cropping intensity in the central Great Plains of the United States has led to increased organic carbon being stored in the soil. A study was conducted to investigate changes in soil physical properties associated with increased organic carbon levels. A cropping systems study was started ...

91

Microscale Pore Shape and Stress Anisotropy Effects on Macroscopic Soil Structural and Hydraulic Properties  

NASA Astrophysics Data System (ADS)

We study the impact of load application to wet soils of relatively high bulk density such as agricultural subsoils. An earlier model of bulk soil compaction under steady and uniform stress based on shrinkage of isolated spherical pores embedded in a homogeneous viscoplastic matrix was extended to consider spheroidal pore shapes and interactions among neighboring pores. The model describes pore shape evolution and deformation rates as functions of triaxial macroscopic stresses and soil rheological properties. The implementation of microscale models to real soils requires consideration of mechanical pore interactions due to nonuniform stress distribution (stress concentration). We applied the Mori-Tanaka theory for interacting pores as a means for upscaling to bulk soil behavior and derived bulk soil moduli comparable to those obtained from standard geotechnical tests. Soil pore closure rates increase with higher water contents (affecting soil rheology) and with pore size. This highlights the structural susceptibility of large pores and the significant impact of their closure on the hydrological behavior of compacted soils. Pore closure rate increases for pores with lower initial aspect ratio (i.e., oblate pores close faster than spherical pores of the same volume). Detailed pore scale stress distributions reveal formation of elastic (non-viscous) domains on pore surface due to soil yield stress higher than the local stress. Comparisons with measurements in bulk soil will be presented.

Or, D.; Berli, M.

2003-04-01

92

RETC CODE FOR QUANTIFYING THE HYDRAULIC FUNCTIONS OF UNSATURATED SOILS  

EPA Science Inventory

This report describes the RETC computer code for analyzing the soil water retention and hydraulic conductivity functions of unsaturated soils. hese hydraulic properties are key parameters in any quantitative description of water flow into and through the unsaturated zone of soils...

93

Spatial variability of soil hydraulics and remotely sensed soil parameters  

NASA Technical Reports Server (NTRS)

The development of methods to correctly interpret remotely sensed information about soil moisture and soil temperature requires an understanding of water and energy flow in soil, because the signals originate from the surface, or from a shallow surface layer, but reflect processes in the entire profile. One formidable difficulty in this application of soil physics is the spatial heterogeneity of natural soils. Earlier work has suggested that the heterogeneity of soil hydraulic properties may be described by the frequency distribution of a single scale factor. The sensitivity of hydraulic and energetic processes to the variation of this scale factor is explored with a suitable numerical model. It is believed that such an analysis can help in deciding how accurately and extensively basic physical properties of field soils need to be known in order to interpret thermal or radar waveband signals. It appears that the saturated hydraulic conductivity needs to be known only to its order of magnitude, and that the required accuracy of the soil water retention function is about 0.02 volume fraction. Furthermore, the results may be helpful in deciding how the total scene or view field, as perceived through a sensor, is composed from the actual mosaic of transient soil properties, such as surface temperature or surface soil moisture. However, the latter proposition presupposes a random distribution of permanent properties, a condition that may not be met in many instances, and no solution of the problem is apparent.

Lascano, R. J.; Van Bavel, C. H. M.

1982-01-01

94

Comparison of Methods for Determining Soil Hydraulic Characteristics  

E-print Network

An adequate description of soil moisture movement is necessary for solution of agriculturally oriented problems such as irrigation, drainage and runoff control. Three approaches for determining the hydraulic properties of soil are in situ...

Howell, T. A.; McFarland, M. J.; Reddell, D. L.; Brown, K. W.; Newton, R. J.; Humphreys, K. B.

95

Three-dimensional quantification of soil hydraulic properties using X-ray Computed Tomography and image-based modeling  

NASA Astrophysics Data System (ADS)

We demonstrate the application of a high-resolution X-ray Computed Tomography (CT) method to quantify water distribution in soil pores under successive reductive drying. We focus on the wet end of the water release characteristic (WRC) (0 to -75 kPa) to investigate changes in soil water distribution in contrasting soil textures (sand and clay) and structures (sieved and field structured) and to determine the impact of soil structure on hydraulic behavior. The 3-D structure of each soil was obtained from the CT images (at a 10 ?m resolution). Stokes equations for flow were solved computationally for each measured structure to estimate hydraulic conductivity. The simulated values obtained compared extremely well with the measured saturated hydraulic conductivity values. By considering different sample sizes we were able to identify the smallest possible representative sample size which is required to determine a globally valid hydraulic conductivity.

Tracy, Saoirse R.; Daly, Keith R.; Sturrock, Craig J.; Crout, Neil M. J.; Mooney, Sacha J.; Roose, Tiina

2015-02-01

96

Coupled water and heat flow in laboratory evaporation experiments and its effects on soil hydraulic properties estimated by the simplified evaporation method  

NASA Astrophysics Data System (ADS)

The prediction of water fluxes in the field requires an accurate determination of soil hydraulic parameters which define the soil water retention and hydraulic conductivity function. The evaporation method has become a standard tool to quickly and reliably determine soil hydraulic properties in the wet to medium pressure head range. Recently, the method has profited from a significant improvement of soil sensors and data evaluation methods. In most cases, the data obtained from a transient evaporation experiment are evaluated using simplifying assumptions, like the ones implicit to Schindler's or Wind's methods. In the past, the effect of these simplifications on the identification of hydraulic properties has been investigated and found to be relatively minor. These studies were based on the evaluation of computer-generated data which were created by numerical modeling of the evaporation process with the Richards equation, i.e. by assuming isothermal liquid flow. Since evaporation from bare soil will always lead to loss of energy, the assumption of constant temperature is questionable. In addition, the effects of thermal and vapor fluxes on simplified evaluation methods have so far hardly been investigated. In this contribution we analyze the effects of (1) coupled heat and water flow and (2) temperature effects on physical parameters. We firstly generated data by a numerical model which solves the coupled heat and water flow problem first derived by Philip and de Vries, and then used these data as source for the estimation of hydraulic properties with the evaluation methods of Schindler and Wind. The virtual realities covered different atmospheric forcings like changing wind speed and varying incoming shortwave radiation. The objective of this study was to identify under which atmospheric conditions, for which soil textures, and in which pressure head range the simplified evaluation methods lead to unbiased estimates of the soil hydraulic properties.

Iden, Sascha C.; Blöcher, Johanna; Diamantopoulos, Efstathios; Durner, Wolfgang

2014-05-01

97

Evaluation of land surface model simulations of evapotranspiration over a 12 year crop succession: impact of the soil hydraulic properties  

NASA Astrophysics Data System (ADS)

Evapotranspiration has been recognized as one of the most uncertain term in the surface water balance simulated by land surface models. In this study, the SURFEX/ISBA-A-gs simulations of evapotranspiration are assessed at local scale over a 12 year Mediterranean crop succession. The model is evaluated in its standard implementation which relies on the use of the ISBA pedotransfer estimates of the soil properties. The originality of this work consists in explicitly representing the succession of crop cycles and inter-crop bare soil periods in the simulations and assessing its impact on the dynamic of simulated and measured evapotranspiration over a long period of time. The analysis focuses on key soil parameters which drive the simulation of evapotranspiration, namely the rooting depth, the soil moisture at saturation, the soil moisture at field capacity and the soil moisture at wilting point. The simulations achieved with the standard values of these parameters are compared to those achieved with the in situ values. The portability of the ISBA pedotransfer functions is evaluated over a typical Mediterranean crop site. Various in situ estimates of the soil parameters are considered and distinct parametrization strategies are tested to represent the evapotranspiration dynamic over the crop succession. This work shows that evapotranspiration mainly results from the soil evaporation when it is continuously simulated over a Mediterranean crop succession. The evapotranspiration simulated with the standard surface and soil parameters of the model is largely underestimated. The deficit in cumulative evapotranspiration amounts to 24% over 12 years. The bias in daily daytime evapotranspiration is -0.24 mm day-1. The ISBA pedotransfer estimates of the soil moisture at saturation and at wilting point are overestimated which explains most of the evapotranspiration underestimation. The overestimation of the soil moisture at wilting point causes the underestimation of transpiration at the end of the crop cycles. The overestimation of the soil moisture at saturation triggers the underestimation of the soil evaporation during the wet soil periods. The use of field capacity values derived from laboratory retention measurements leads to inaccurate simulation of soil evaporation due to the lack of representativeness of the soil structure variability at the field scale. The most accurate simulation is achieved with the values of the soil hydraulic properties derived from field measured soil moisture. Their temporal analysis over each crop cycle provides meaningful estimates of the wilting point, the field capacity and the rooting depth to represent the crop water needs and accurately simulate the evapotranspiration over the crop succession. We showed that the uncertainties in the eddy-covariance measurements are significant and can explain a large part of the unresolved random differences between the simulations and the measurements of evapotranspiration. Other possible model shortcomings include the lack of representation of soil vertical heterogeneity and root profile along with inaccurate energy balance partitioning between the soil and the vegetation at low LAI.

Garrigues, S.; Olioso, A.; Calvet, J.-C.; Martin, E.; Lafont, S.; Moulin, S.; Chanzy, A.; Marloie, O.; Desfonds, V.; Bertrand, N.; Renard, D.

2014-10-01

98

Probing pore-scale modeling methods to determine saturated/unsaturated hydraulic properties of highly structured agricultural soils  

NASA Astrophysics Data System (ADS)

Novel pore-scale modelling methods are becoming popular in geophysical and petrophysical applications to determine single and multi-phase transport properties of sedimentary rocks (e.g., sandstones, carbonates, etc.). However, the implication of these techniques for soils is very limited to simple single phase flow simulations on small domains (without comparison to any laboratory measurements), or to simple pore-network approaches with more qualitative results which capture some important flow features (an especially strong limitation of these methods is usage of cylindrical pore-throats capable of containing only one fluid). In this contribution we try to determine saturated/unsaturated hydraulic properties and water retention curve (WRC) using computational fluid dynamics (CFD) and pore-network modelling approaches for three soil samples taken from different layers from an agricultural field in Suzdal area of Russian Plain. Cylindrical samples with radius of 5 cm and volume of approximately 100 cubic cm were scanned using X-ray microtomography device SkyScan-1172 with the resolution of around 15 microns. After thresholding and bunarization the biggest possible cubes were subcropped and used for further analysis. At first, single-phase velocity fields and permeabilities were determined numerically solving Stokes equation directly on digitized 3D images. Same images were used for extraction of the pore-networks using maximal inscribed ball method. Single and two-phase (water-air) flow properties, including drainage curve (WRC) and relative permeabilities, were determined in these networks considering triangular and rectangular pore cross sections. Due to the unconventional samplers it was impossible to measure transport properties on the samples used for scanning and modelling. All measurements (bulk density, grain/aggregate size distributions, hydraulic conductivity and WRC, etc.) were performed using numerous (30-50 samples for each soil layer) conventionally obtained samples and used for comparison against scanning and modelling results. Our results show that both modelling methods provide similar single-phase flow results, so that simplified pore-network geometry is representative for given soil samples. Comparison of simulated and measured values for unsaturated characteristics also showed very promising results. Finally, we compare simulated relative permeabilities to that obtained using conventional Mualem-van Genuchten approaches and its modifications (Durner's WRCs for multi-modal pore-sizes). Future prospects of the pore-scale modelling technique in soil science applications are outlined and current challenges are discussed.

Gerke, Kirill; Korost, Dmitry; Umarova, Aminat; Vasilyev, Roman; Karsanina, Marina

2013-04-01

99

Estimation of Effective Soil Hydraulic Properties Using Data From High Resolution Gamma Densiometry and Tensiometers of Multi-Step-Outflow Experiments  

NASA Astrophysics Data System (ADS)

Dynamic Multi Step Outflow (MSO) experiments serve for the estimation of the parameters from soil hydraulic functions like e.g. the Mualem van Genuchten model. The soil hydraulic parameters are derived from outflow records and corresponding matric potential measurements from commonly a single tensiometer using inverse modeling techniques. We modified the experimental set up allowing for simultaneous measurements of the matric potential with three tensiometers and the water content using a high-resolution gamma-ray densiometry measurement system (Bieberle et al., 2007, Hampel et al., 2007). Different combinations of the measured time series were used for the estimation of effective soil hydraulic properties, representing different degrees of information of the "hydraulic reality" of the sample. The inverse modeling task was solved with the multimethod search algorithm AMALGAM (Vrugt et al., 2007) in combination with the Hydrus1D model (Šimúnek et al., 2008). Subsequently, the resulting effective soil hydraulic parameters allow the simulation of the MSO experiment and the comparison of model results with observations. The results show that the information of a single tensiometer together with the outflow record result in a set of effective soil hydraulic parameters producing an overall good agreement between the simulation and the observation for the location of the tensiometer. Significantly deviating results are obtained for the other tensiometer positions using this parameter set. Inclusion of more information, such as additional matric potential measurements with the according water contents within the optimization procedure lead to different, more representative hydraulic parameters which improved the overall agreement significantly. These findings indicate that more information about the soil hydraulic state variables in space and time are necessary to obtain effective soil hydraulic properties of soil core samples. Bieberle, A., Kronenberg, J., Schleicher, E., Hampel, U., 2007: Design of a high resolution gamma ray detector module for tomography applications, Nuclear Instruments And Methods in Physics Research A, Vol. 572, pp. 668-675. Hampel, U., Bieberle, A., Hoppe, D., Kronenberg, J., Schleicher, E., Sühnel, T., Zimmermann, F., Zippe, C., 2007: High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications, Review of Scientific Instruments, Vol. 78, 103704. Šimúnek, J., Šejna, M., Saito, H., Sakai, M. & van Genuchten, M. Th., 2008: The Hydrus-1D Software Package for Simulating the Movement of Water, Heat, and Multiple Solutes in Variably Saturated Media, Version 4.0, HYDRUS Software Series 3, Department of Environmental Sciences, University of California Riverside, Riverside, California, USA, pp. 315. Vrugt, J.A. and Robinson, B.A. 2007: Improved evolutionary optimization from genetically adaptive multimethod search, Proc. Nat. Acad. Sci. USA, 104, 708 - 711.

Werisch, Stefan; Lennartz, Franz; Bieberle, Andre

2013-04-01

100

Flow at Low Water Contents: A Simple Approach for Inverse Estimation of van Genuchten-Mualem Soil Hydraulic Parameters  

E-print Network

BP 7021, Burkina Faso Abstract The unsaturated soil hydraulic properties (the soil water. The amount and energy status of water in a soil can affect considerably the soil hydraulic properties. While reflecting the soil hydraulic properties are conventionally expressed using two functions, namely the water

Paris-Sud XI, Université de

101

Can texture-based classification optimally classify soils with respect to soil hydraulics?  

NASA Astrophysics Data System (ADS)

In the past, texture-based classification of soils has been used for grouping soils in variably saturated water flow and solute transport studies. Classification of soils becomes especially important for large-scale studies where the spatial and temporal variability in the hydraulic properties of soils exceeds the field sampling capabilities. Although soil-texture-based classification has been widely used, questions remain about the validity of its use from a hydraulic perspective. In this study, we attempt to answer the following questions: (1) what is the optimal number of (soil hydraulic) classes that can adequately classify the soils from a hydraulic standpoint, and (2) how does such a classification compare to the soil texture classification currently used? To investigate these questions, the commonly used k-means clustering algorithm was integrated with the ROSETTA pedotransfer functions to predict the so-called soil hydraulic classes. The optimal soil hydraulic classifications and the associated uncertainty were estimated for numbers of soil hydraulic classes varying from 2 to 30. It was concluded that the optimal number of soil hydraulic classes is 12. The optimal soil hydraulic classes were represented in a ternary diagram called the soil hydraulic triangle. While there exist some surprising similarities in classification between the soil texture triangle and the soil hydraulic triangle for soils with high sand percentages (sand >60%), the opposite is true for soils with low sand contents. From a hydraulic standpoint, the texture-based classification does not classify soils well when there is a considerable impact of capillary forces. The soil texture and hydraulic classes were analyzed for accuracy using two databases. Compared to the soil texture classes, it was found that the soil hydraulic classes marginally improve the accuracy of classification. Even though the improvement is only marginal, it was observed that the optimality of soil texture triangle for hydraulic studies cannot be assured because of the nonuniform distribution of data across various textural possibilities in the two databases. As an extension of this research, we have also estimated the average soil hydraulic parameters for the different optimal soil hydraulic classes.

Twarakavi, Navin K. C.; Å Imå¯Nek, Jirka; Schaap, M. G.

2010-01-01

102

Effect of Tillage on Soil Hydraulic Conductivity in Two Contrasting Soil Textures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage profoundly affects soil physical and hydraulic properties. It is essential to select a tillage system that sustains the soil hydraulic properties required for successful growth of agricultural crops. We compared effects of conventional tillage (CT) and strip tillage (ST) systems on field-sat...

103

Hydraulic properties of layered soils influence survival of Rhodes grass ( Chloris gayana Kunth.) during water stress  

Microsoft Academic Search

Survival of vegetation on soil-capped mining wastes is often impaired during dry seasons due to the limited amount of water stored in the shallow soil capping. Growth and survival of Rhodes grass (Chloris gayana) during soil drying on various layered capping sequences constructed of combinations of topsoil, subsoil, seawater-neutralised residue sand and low grade bauxite was determined in a glasshouse.

JB Wehr; HB So; NW Menzies; I Fulton

2005-01-01

104

Hydraulic Property and Soil Textural Classification Measurements for Rainier Mesa, Nevada Test Site, Nevada  

USGS Publications Warehouse

This report presents particle size analysis, field-saturated hydraulic conductivity measurements, and qualitative descriptions of surficial materials at selected locations at Rainier Mesa, Nevada. Measurements and sample collection were conducted in the Rainier Mesa area, including unconsolidated sediments on top of the mesa, an ephemeral wash channel near the mesa edge, and dry U12n tunnel pond sediments below the mesa. Particle size analysis used a combination of sieving and optical diffraction techniques. Field-saturated hydraulic conductivity measurements employed a single-ring infiltrometer with analytical formulas that correct for falling head and spreading outside the ring domain. These measurements may prove useful to current and future efforts at Rainier Mesa aimed at understanding infiltration and its effect on water fluxes and radionuclide transport in the unsaturated zone.

Ebel, Brian A.; Nimmo, John R.

2010-01-01

105

Hydraulic Property and Soil Textural Classification Measurements for Rainier Mesa, Nevada Test Site, Nevada  

SciTech Connect

This report presents particle size analysis, field-saturated hydraulic conductivity measurements, and qualitative descriptions of surficial materials at selected locations at Rainier Mesa, Nevada. Measurements and sample collection were conducted in the Rainier Mesa area, including unconsolidated sediments on top of the mesa, an ephemeral wash channel near the mesa edge, and dry U12n tunnel pond sediments below the mesa. Particle size analysis used a combination of sieving and optical diffraction techniques. Field-saturated hydraulic conductivity measurements employed a single-ring infiltrometer with analytical formulas that correct for falling head and spreading outside the ring domain. These measurements may prove useful to current and future efforts at Rainier Mesa aimed at understanding infiltration and its effect on water fluxes and radionuclide transport in the unsaturated zone.

Ebel, Brian A.; Nimmo, John R.

2009-12-29

106

Virtual Soils - Assessment of the Effects of Soil Structure on the Hydraulic Behavior of Cultivated Soils  

NASA Astrophysics Data System (ADS)

The hydraulic behavior of soil is determined by the spatial heterogeneity of its hydraulic properties. The interplay between parent material, pedogenesis and tillage leads to characteristic structures in cultivated soils: sealed or loosened soil surface, compacted plow pan and traffic lanes. These structures overlay with natural features such as biopores and boundaries between soil horizons. To assess the individual or combined impact of such structural components on soil hydrology, the heterogeneity of the soil must be known at a scale of several meters and at a resolution in the range of centimeters. This, however, cannot be achieved in experimental setups. An alternative solution is the generation of synthetic but realistic structures together with their hydraulic properties as a basis for modeling the hydraulic behavior in response to different boundary conditions. This approach is extendable to an arbitrary number of structural components. With such 'virtual soils' at hand, comparative studies are possible, that help quantifying the relation between soil architecture and soil function. Further, the existence of effective soil hydraulic properties, which are capable to predict the average water dynamics at the field scale, can be tested by inverse modeling. The evaluation of different "measured" data sets in terms of information content and usefulness for identifying suitable effective models and effective model parameters can be analyzed. We introduce a structure generator and present comparative simulations between soils with increasing complexity for a period of several weeks with precipitation and evaporation. The simulations demonstrate, that the structure and the hydraulic properties close to the soil surface clearly govern evaporation, while the impact of heterogeneity on groundwater recharge is more complex.

Vogel, H.; Schlüter, S.; Ippisch, O.; Roth, K.; Schelle, H.; Durner, W.; Kasteel, R.; Vanderborght, J.

2011-12-01

107

Multivariate distributions of soil hydraulic parameters  

NASA Astrophysics Data System (ADS)

Statistical distributions of soil hydraulic parameters have to be known when synthetic fields of soil hydraulic properties need to be generated in ensemble modeling of soil water dynamics and soil water content data assimilation. Pedotransfer functions that provide statistical distributions of water retention and hydraulic conductivity parameters for textural classes are most often used in the parameter field generation. Presence of strong correlations can substantially influence the parameter generation results. The objective of this work was to review and evaluate available data on correlations between van Genuchten-Mualem (VGM) model parameters. So far, two different approaches were developed to estimate these correlations. The first approach uses pedotransfer functions to generate VGM parameters for a large number of soil compositions within a textural class, and then computes parameter correlations for each of the textural classes. The second approach computes the VGM parameter correlations directly from parameter values obtained by fitting VGM model to measured water retention and hydraulic conductivity data for soil samples belonging to a textural class. Carsel and Parish (1988) used the Rawls et al. (1982) pedotransfer functions, and Meyer et al. (1997) used the Rosetta pedotransfer algorithms (Schaap, 2002) to develop correlations according to the first approach. We used the UNSODA database (Nemes et al. 2001), the US Southern Plains database (Timlin et al., 1999), and the Belgian database (Vereecken et al., 1989, 1990) to apply the second approach. A substantial number of considerable (>0.7) correlation coefficients were found. Large differences were encountered between parameter correlations obtained with different approaches and different databases for the same textural classes. The first of the two approaches resulted in generally higher values of correlation coefficients between VGM parameters. However, results of the first approach application depend on pedotransfer relationships not only within a given textural class but also on pedotransfer relationships within other textural classes since the pedotransfer relationships are developed across the database containing data for several textural classes. Therefore, joint multivariate parameter distributions for a specific class may not be sufficiently accurate. Currently PTF may give the best prediction of the parameter itself, but they are not designed to estimate correlations between parameters. Covariance matrices for soil hydraulic parameters present an additional type of pedotransfer information that needs to be acquired and used whenever random sets of those parameters are to be generated.

Qu, Wei; Pachepsky, Yakov; Huisman, Johan Alexander; Martinez, Gonzalo; Bogena, Heye; Vereecken, Harry

2014-05-01

108

Soil Hydraulic Characteristics of a Small Southwest Oregon Watershed Following  

E-print Network

--------------------------------------------- Soil Hydraulic Characteristics of a Small Southwest by a high-intensity burn over areas of steep topography. The areal distribution of soil hydraulic of infiltration capacity, saturated hydraulic conductivity, and soil moisture characteristics. Also, measures

Standiford, Richard B.

109

Effects of trampling by cattle on the hydraulic and mechanical properties of soil  

Microsoft Academic Search

Destroyed soil structure can increase surface runoff water, with adverse environmental impacts. The effects of trampling by cattle on physical parameters of a heavy clay (a Typic Cryaquept) were studied at the followings four Site types of a pasture after grazing for three seasons: (1) grass with no visible trampling; (2) pasture with some trampling; (3) vicinity of a drinking

Liisa Pietola; Rainer Horn; Markku Yli-Halla

2005-01-01

110

UTILITY OF NON-PARAMETRIC 'K-NEAREST NEIGHBOR' ALGORITHMS TO ESTIMATE SOIL HYDRAULIC PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Non-parametric approaches are being used in various fields to address classification type problems, as well as to estimate continuous variables. One type of the non-parametric lazy learning algorithms, a k-Nearest Neighbor (k-NN) algorithm has been developed to estimate soil water retention at –33 a...

111

ERODIBLE AND SOIL HYDRAULIC PROPERTIES AFFECTED BY 20 YEARS OF TILLAGE IN SUBARCTIC ALASKA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wind erosion and lack of precipitation can impact crop production in arid and semi-arid regions of the world. A long term tillage and residue management was initiated 20 years ago in interior Alaska to identify practices that will minimize erosion and conserve soil moisture in a continuous barley c...

112

Use of LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils  

NASA Technical Reports Server (NTRS)

This work focuses on the characterization of natural, spatially variable, semivegetated landscapes using a linear, stochastic, canopy-soil reflectance model. A first application of the model was the investigation of the effects of subpixel and regional variability of scenes on the shape and structure of red-infrared scattergrams. Additionally, the model was used to investigate the inverse problem, the estimation of subpixel vegetation cover, given only the scattergrams of simulated satellite scale multispectral scenes. The major aspects of that work, including recent field investigations, are summarized.

Eagleson, Peter S.; Jasinski, Michael F.

1988-01-01

113

Evaluation of fly ash as a soil amendment for the Atlantic Coastal Plain: I. Soil hydraulic properties and elemental leaching  

Microsoft Academic Search

A major limitation to crop yields in the Atlantic Coastal Plain is drought stress caused by the low moisture-holding capacities of the coarse-textured soils common to the area. Because coal fly ash is comprised primarily of silt and clay-sized particles, it has the potential, if applied at high enough rates, to permanently change soil texture and increase moisture holding capacity.

M. Ghodrati; J. T. Sims; B. L. Vasilas

1995-01-01

114

Effects of Estimating Soil Hydraulic Properties and Root Growth Factor on Soil Water Balance and Crop Production  

Technology Transfer Automated Retrieval System (TEKTRAN)

Increasing water use efficiency (WUE) is one of the oldest goals in agricultural sciences, yet it is still not fully understood and achieved due to the complexity of soil-weather-management interactions. System models that quantify these interactions are increasingly used for optimizing crop WUE, es...

115

Efficient hydraulic properties of root systems  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms of ecosystem root water uptake (RWU) is paramount for parameterizing hydrological models. With the increase in computational power it is possible to calculate RWU explicitly up to the single plant scale using physical models. However, application of these models for increasing our understanding of ecosystem root water uptake is hindered by the deficit in knowledge about the detailed hydraulic parameter distribution within root systems. However, those physical models may help us to identify efficient parameterizations and to describe the influence of these hydraulic parameters on RWU profiles. In this research, we investigated the combined influence of root hydraulic parameters and different root topologies on shaping efficient root water uptake. First, we use a conceptual model of simple branching structures to understand the influence of branching location and transitions in root hydraulic properties on the RWU patterns in typical sub root structures. Second, we apply a physical model called "aRoot" to test our conclusions on complex root system architectures of single plants. aRoot calculates the distribution of xylem potential within arbitrary root geometries to satisfy a given water demand depending on the available water in the soil. Redistribution of water within the bulk soil is calculated using the Richards equation. We analyzed results using a measure of uptake efficiency, which describes the effort necessary for transpiration. Simulations with the conceptual model showed that total transpiration in sub root structures is independent of root hydraulic properties over a wide range of hydraulic parameters. On the other hand efficiency of root water uptake depends crucially on distribution hydraulic parameters in line with root topology. At the same time, these parameters shape strongly the distribution of RWU along the roots, and its evolution in time, thus leading to variable individual root water uptake profiles. Calculating RWU of three dimensional root architectures unveiled that the same effects can be observed at the single plant scale. Total transpiration is almost independent of root hydraulic properties. On the other hand, the arrangement of hydraulic properties significantly influences RWU efficiency. Furthermore the vertical root water uptake profiles are governed by the different root properties. They result from two combined re-distribution patterns over time: One within a rooting branch similar to the results mentioned above, and a second one between the different rooting branches within the root system. This leads to complex vertical uptake profiles, which cannot be predicted from a combination of root abundance and soil moisture, and depend strongly on the individual morphology.

Bechmann, Marcel; Schneider, Christoph; Carminati, Andrea; Hildebrandt, Anke

2013-04-01

116

Onset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water dynamics  

E-print Network

Onset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water hysteresis in canopy conductance, hydraulic lift, and compensatory root water uptake during extended drying effective is dictated by soil hydraulic properties and surrogates for atmospheric water vapor demand

Katul, Gabriel

117

Effective hydraulic parameters for steady state vertical flow in heterogeneous soils  

E-print Network

Effective hydraulic parameters for steady state vertical flow in heterogeneous soils Jianting Zhu August 2003. [1] In hydroclimate and land-atmospheric interaction models, effective hydraulic properties are needed at large grid scales. In this study, the effective soil hydraulic parameters of the areally

Mohanty, Binayak P.

118

Xylem Hydraulics and the SoilPlantAtmosphere Continuum: Opportunities and Unresolved Issues  

E-print Network

Xylem Hydraulics and the Soil­Plant­Atmosphere Continuum: Opportunities and Unresolved Issues John S. Sperry,* Volker Stiller, and Uwe G. Hacke ABSTRACT about the hydraulic properties of the plant vascular sys- tem. The traditional view of plant hydraulics being dom-Soil and xylem are similar

Stiller, Volker

119

THE RETC CODE FOR QUANTIFYING THE HYDRAULIC FUNCTIONS OF UNSATURATED SOILS  

EPA Science Inventory

This report describes the RETC computer code for analyzing the soil water retention and hydraulic conductivity functions of unsaturated soils. These hydraulic properties are key parameters in any quantitative description of water flow into and through the unsaturated zone of soil...

120

A sediment structure model for describing the 3D spatial distribution of soil hydraulic properties of an artificial catchment using pedotransfer functions  

NASA Astrophysics Data System (ADS)

Modelling the spatial heterogeneity of catchments is a prerequisite for the understanding of flow processes and the application of hydrological models. The initial structure represents also the starting point for catchment and ecosystem development. The quality of hydrologic modeling is often limited due to a lack of data or an oversimplification of aquifer properties. Predictions can be significantly improved by using spatial models that reproduce specific structural characteristics. Current geostatistical methods are unable the capture spatially complex conditions, e.g. abrupt changes in structures. More deterministic structure generator approaches are currently been discussed in hydrogeology for exploration. Process-based structure generators deduce structural characteristics e.g. from the known formation processes of the aquifer. The objective was to describe the spatial distribution of soil hydraulic properties in a catchment based on generated 3D sediments distributions. The approach was tested for the artificially constructed "Hühnerwasser" ("Chicken Creek") catchment. The catchment is located in the post-lignite mining area of Welzow-Süd in Lower Lusatia, Brandenburg, Germany. Here, the initial sediment distribution was governed primarily by dumping processes of the large-scale mining technology and the geological conditions at the excavation site. For the initially organic matter-free sandy sediments, the structure model generated the distributions of soil texture and soil bulk density within dumping spoil cones. These were represented by 2D cross sections with compacted central parts and particle-segregated flanks. The 3D geometry of the catchment was generated by sequencing of these basic structural elements along identified stacker trajectories, finally yielding a discretized 3D volume model using the GOCAD software. Based on these data, spatial distributions of hydraulic properties were calculated using well-established pedotransfer functions (Vereecken et al. 1989 and Arya and Paris 1981). Qualitative comparisons of estimated hydrostatic soil moisture conditions with wetness distributions derived from aerial images suggested relatively similar patterns reflecting highly-saturated stagnant areas near compacted impact zones that originated from sediment dumping. In order to account for the remaining uncertainty in sediment composition and mass balances, different scenarios of sediment distribution were analyzed. The generated 3D-spatial distribution patterns were analyzed on different scales to determine the effects of spatial upscaling and to understand local effects on hydrological processes at larger scales. The hydraulic property distributions will be coupled with hydrological modeling, and results will be validated using hydrological monitoring data.

Maurer, T.; Bartsch, R.; Schneider, A.; Gerke, H. H.

2012-04-01

121

www.VadoseZoneJournal.org Estimation of Soil Hydraulic  

E-print Network

hydraulic parameters from the GPR data in an inversion loop. To monitor the soil water con- tent dynamicswww.VadoseZoneJournal.org Estimation of Soil Hydraulic Parameters in the Field by Integrated approach was used to remotely infer the unsat- urated soil hydraulic parameters from time-lapse ground

Hubbard, Susan

122

DEMONSTRATION BULLETIN: HYDRAULIC FRACTURING OF CONTAMINATED SOIL  

EPA Science Inventory

Hydraulic fracturing is a physical process that creates fractures in silty clay soil to enhance its permeability. The technology, developed by the Risk Reduction Engineering Laboratory (RREL) and the University of Cincinnati, creates sand-filled horizontal fractures up to 1 in. i...

123

Effective Hydraulic Conductivity of Unsaturated Isotropic Soils with Multidimensional Heterogeneity  

SciTech Connect

Accurate simulation and prediction of flow and transport of solutes in a heterogeneous vadose zone requires the appropriate hydraulic properties corresponding to the spatial scale of interest. Upscaling techniques provide effective properties to describe the vadose zone system’s behavior with information collected at a much smaller scale. Realizing that a saturated system can be considered as a special state of the unsaturated system, the methodologies for upscaling the saturated hydraulic conductivity of heterogeneous isotropic porous media under steady-state flow conditions can be extended for upscaling the unsaturated hydraulic conductivity. An advantage of this approach is that the extended upscaling methods are independent of the choice of hydraulic function models. The Matheron, small-perturbation, and self-consistent upscaling methods were used to demonstrate the approach. The extended upscaling methods were tested using multi-step numerical experiments of gravity-induced flow into Miller-similar synthetic soils with different levels of heterogeneity. Results show that, under 3-D flow conditions in isotropic soils, the self-consistent method applies to all the soil heterogeneity conditions considered while the Matheron and small-perturbation methods are acceptable for soil of relatively low variability.

Zhang, Z. F.

2010-05-01

124

Project Summary. THE RETC CODE FOR QUANTIFYING THE HYDRAULIC FUNCTIONS OF UNSATURATED SOILS  

EPA Science Inventory

This summary describes the RETC computer code for analyzing the soil water retention and hydraulic conductivity functions of unsaturated soils. These hydraulic properties are key parameters in any quantitative description of water flow into and through the unsaturated zone of soi...

125

Estimating soil hydraulic parameters from transient flow experiments in a centrifuge using parameter optimization technique  

Microsoft Academic Search

A modified version of the Hydrus software package that can directly or inversely simulate water flow in a transient centrifugal field is presented. The inverse solver for parameter estimation of the soil hydraulic parameters is then applied to multirotation transient flow experiments in a centrifuge. Using time-variable water contents measured at a sequence of several rotation speeds, soil hydraulic properties

Jirka Šim?nek; John R. Nimmo

2005-01-01

126

Cautionary notes on the use of the Rawls et al. (1982) soil hydraulic pedotransfer functions  

Technology Transfer Automated Retrieval System (TEKTRAN)

Environmental and crop simulation models use a wide range of inputs that include soil hydraulic properties. For many applications, use of laboratory determined soil water retention and hydraulic conductivity data is not feasible; therefore those need to be estimated. The current version of the Agric...

127

Correspondence of Hydraulic Functions and Its Implication on Upscaling for Large Scale Flux and Surface Soil Moisture in Heterogeneous Soils  

NASA Astrophysics Data System (ADS)

This study investigates two major issues involving soil hydraulic properties: (1) hydraulic parameter correspondence between two commonly used soil hydraulic property functions, and (2) its implication in upscaling of hydraulic properties to large scale heterogeneous soils. We first establish parameter correspondence between the conductivity functions based on hydrologic process equivalence. Our approach forces predicted flux across the soil surface and the surface soil moisture content to be constant for different hydraulic property functions. We selected these two hydrologic quantities for correspondence purposes because these state variables are important for upscaling hydrologic processes from the local to large scales. We then investigate the implication of parameter equivalence on upscaling schemes for soil hydraulic parameters. This allows predictions of the ensemble characteristics for steady-state flow at large scales. To test the inference regarding the impact of hydraulic parameter correspondence and statistical structure on upscaling schemes, we will use the hydraulic property data measured from the Corn Creek Fan Complex located on the Desert National Wildlife Refuge north of Las Vegas, NV.

Zhu, J.; Young, M. H.

2005-12-01

128

TDR System for Hydraulic Characterization of Unsaturated Soils in the Centrifuge John S. McCartney1  

E-print Network

TDR System for Hydraulic Characterization of Unsaturated Soils in the Centrifuge John S. McCartney1@mail.utexas.edu Abstract A centrifuge permeameter has been developed to provide expedited determination of the hydraulic bucket. The hydraulic properties of a soil specimen are measured using the centrifuge permeameter

Zornberg, Jorge G.

129

Evaluating models for predicting hydraulic characteristics of layered soils  

NASA Astrophysics Data System (ADS)

Soil water characteristic curve (SWCC) and unsaturated hydraulic conductivity (K-coefficient) are critical hydraulic properties governing soil water activity on layered soils. Sustainable soil water conservation would not be possible without accurate knowledge of these hydraulic properties. Infield rainwater harvesting (IRWH) is one conservation technique adopted to improve the soil water regime of a number of clay soils found in the semi arid areas of Free State province of South Africa. Given that SWCC is much easier to measure, most soil water studies rely on SWCC information to predict in-situ K-coefficients. This work validated this practice on the Tukulu, Sepane and Swartland layered soil profiles. The measured SWCC was first described using Brooks and Corey (1964), van Genuchten (1980) and Kasugi (1996) parametric models. The conductivity functions of these models were then required to fit in-situ based K-coefficients derived from instantaneous profile method (IPM). The same K-coefficient was also fitted by HYDRUS 1-D using optimised SWCC parameters. Although all parametric models fitted the measured SWCC fairly well their corresponding conductivity functions could not do the same when fitting the in-situ based K-coefficients. Overestimates of more than 2 orders of magnitude especially at low soil water content (SWC) were observed. This phenomenon was pronounced among the upper horizons that overlaid a clayey horizon. However, optimized ? and n parameters using HYDRUS 1-D showed remarkable agreement between fitted and in-situ K-coefficient with root sum of squares error (RMSE) recording values not exceeding unity. During this exercise the Brooks and Corey was replaced by modified van Genuchten model (Vogel and Cislerova, 1988) since it failed to produce unique inverse solutions. The models performance appeared to be soil specific with van Genuchten-Mualem (1980) performing fairly well on the Orthic and neucutanic horizons while its modified form fitted very well the prismatic and pedo-cutanic horizons. The lognormal distribution model of Kasugi (1996) showed an extraordinary good fit among the Swartland profile horizons especially the saprolite rock layer. It was therefore concluded that in-situ KL-coefficient estimates from SWCC parameters could be acceptable if only rough estimates were required. Optimization of parameters for in-situ conditions especially for HYDRUS 1-D carried much prospects in characterising the hydraulic properties of most of the layered soils earmarked for IRWH in the province.

Mavimbela, S. S. W.; van Rensburg, L. D.

2012-01-01

130

The Soil Hydraulic Response to Disturbance and Recovery  

NASA Astrophysics Data System (ADS)

While the rate of deforestation in the humid tropics seems to wax and wane with the global demand for certain commodities, the rate of reforestation on degraded lands has been less spectacular. Nonetheless, this process has affected substantial tracts of land in the Amazon basin. We are interested in the rates at which soil hydraulic properties respond to deforestation and reforestation, and in the effect of land-use history before reforestation on these rates. The preliminary results from ongoing true and false time series experiments in the south-western Amazon basin of Brazil and the montane rainforest of eastern Ecuador emphasize a pronounced asymmetry of the soil hydraulic response to disturbance and recovery: whereas just one year of extensive grazing upon pasture establishment reduces infiltrability and topsoil permeability by more than half, more than ten years of secondary succession or afforestation with commercial tree species are required to elicit an increase in these soil properties. The rate of recovery depends on the kind and duration of land-use before abandonment and reforestation: it is slow after prolonged grazing and rapid after short agricultural use. We conclude that a soil hydraulic pasture imprint may be preserved for many years during secondary succession, and hence that secondary forests and plantations continue to behave hydrologically like pastures for many years.

Zimmermann, B.; Elsenbeer, H.

2006-12-01

131

Mucilage: The hydraulic bridge between roots and soil  

NASA Astrophysics Data System (ADS)

As plant roots take up water and the soil dries, water depletion is expected to occur in the soil near the roots, the so called rhizosphere. Ultimately, as the soil hydraulic conductivity drops and the soil cannot sustain the transpiration demand, roots shrink and lose contact to the soil. Both, water depletion in the rhizosphere and formation of air-filled gaps at the root-soil interface potentially limit the availability of water to plants. How can plants overcome these potential hydraulic barriers at the root-soil interface? One strategy consists in the exudation of mucilage from the root tips. Mucilage is a polymeric gel that is capable of holding large volumes of water. When exuded into the soil, mucilage remains in the vicinity of roots thanks to its relatively high viscosity and reduced surface tension. As mucilage is mainly made of water, its slow penetration into the soil results in higher water content and hydraulic conductivity of the rhizosphere compared to the adjacent bulk soil. Recent measurements with a root pressure probe technique demonstrated that mucilage exudation facilitates the water flow in dry soils. Additionally, mucilage increases the adhesion of soil particles to the roots, reducing the formation of gaps at the root-soil interface. Based on these observations, it is very tempting to conclude that mucilage acts as an optimal hydraulic bridge across the root-soil interface. However, as mucilage dries and ages, it turns hydrophobic. Consequently, the rhizosphere becomes water repellent and its rewetting time increases. Our former experiments showed that after irrigation subsequent to a drying cycle, the rhizosphere of lupines remained markedly dry for 2 days. Recently, we demonstrated that the rhizosphere water repellency is concomitant with a decrease in local water uptake of 4-8 times. We conclude that after drying and rewetting, the rhzisophere temporarily limits root water uptake. In summary, the hydraulic properties of the root-soil interface changes over time and along the root system. Young, well hydrated mucilage optimally connects the roots to the soil and facilitates the uptake of water from relatively dry soils. However, as mucilage ages and dries, it reduces the rhizosphere wettability and the water flow to the roots. Such a dual behavior of the rhizosphere, rather than a contradiction, seems a plant strategy to adapt to the typically heterogeneous distribution of water in soils. For instance, in a soil profile with water stored in the sub soil, mucilage would facilitate the water uptake of young, deep root segments and it would avoid water loss from the root segments into the dry top soil. These studies show that the root-soil interactions in the rhizosphere play a crucial role in regulating root water uptake. We believe that s better understanding and management of such interactions can bring a more efficient and sustainable use of water resources.

Carminati, Andrea; Zarabanadkouki, Mohsen; Kroener, Eva; Ahmed, Mutez A. A.

2014-05-01

132

Interaction between soil mineralogy and the application of crop residues on aggregate stability and hydraulic conductivity of the soil  

NASA Astrophysics Data System (ADS)

One of the main goals of modern agriculture is to achieve sustainability by maintaining crop productivity while avoiding soil degradation. Intensive cultivation could lead to a reduction in soil organic matter that could affect the structure stability and hydraulic conductivity of the soil. Moreover, crops extract nutrients from the soil that are taken away from the field when harvested, and as a consequence, the addition of fertilizers to the soil is necessary to maintain crop productivity. One way to deal with these problems is to incorporate crop residues into the soil after harvest. Crop residues are a source of organic matter that could improve soil physical properties, such as aggregate stability and soil hydraulic conductivity. However, this effect could vary according to other soil properties, such as clay content, clay mineralogy, and the presence of other cementing materials in the soil (mainly carbonates and aluminum and iron oxides). In the present work, the interaction between the addition of chickpea crop residues to the soil and clay mineralogy on aggregate stability and saturated hydraulic conductivity were studied. Chickpea plant residues were added at a rate of 0.5% (w/w) to smectitic, kaolinitic, illitic and non-phyllosilicate soils from different regions. The soils without (control) and with chickpea residues were incubated for 0, 3, 7 and 30 days, and the saturated hydraulic conductivity of the soils was measured in columns after each incubation time. The response of hydraulic conductivity to the addition of residues and incubation time was different in the soils with various mineralogies, although in general, the addition of chickpea residues increased the saturated hydraulic conductivity as compared with the control soils. This positive effect of crop residues on hydraulic conductivity was mainly a result of improved aggregate stability and resistance to slaking during wetting.

Lado, M.; Kiptoon, R.; Bar-Tal, A.; Wakindiki, I. I. C.; Ben-Hur, M.

2012-04-01

133

Spatial Averaging of van Genuchten Hydraulic Parameters for Steady-State Flow in Heterogeneous Soils: A Numerical Study  

E-print Network

Spatial Averaging of van Genuchten Hydraulic Parameters for Steady-State Flow in Heterogeneous properties and rainfall intensity on various statistical ters. Pixel-scale soil hydraulic parameters tries to answer a major question: What will be the effective and parameters in the hydraulic property

Mohanty, Binayak P.

134

Using random forests to explore the effects of site attributes and soil properties on near-saturated and saturated hydraulic conductivity  

NASA Astrophysics Data System (ADS)

Knowledge of the near-saturated and saturated hydraulic conductivity of soil is fundamental for understanding important processes like groundwater contamination risks or runoff and soil erosion. Hydraulic conductivities are however difficult and time-consuming to determine by direct measurements, especially at the field scale or larger. So far, pedotransfer functions do not offer an especially reliable alternative since published approaches exhibit poor prediction performances. In our study we aimed at building pedotransfer functions by growing random forests (a statistical learning approach) on 486 datasets from the meta-database on tension-disk infiltrometer measurements collected from peer-reviewed literature and recently presented by Jarvis et al. (2013, Influence of soil, land use and climatic factors on the hydraulic conductivity of soil. Hydrol. Earth Syst. Sci. 17(12), 5185-5195). When some data from a specific source publication were allowed to enter the training set whereas others were used for validation, the results of a 10-fold cross-validation showed reasonable coefficients of determination of 0.53 for hydraulic conductivity at 10 cm tension, K10, and 0.41 for saturated conductivity, Ks. The estimated average annual temperature and precipitation at the site were the most important predictors for K10, while bulk density and estimated average annual temperature were most important for Ks prediction. The soil organic carbon content and the diameter of the disk infiltrometer were also important for the prediction of both K10 and Ks. However, coefficients of determination were around zero when all datasets of a specific source publication were excluded from the training set and exclusively used for validation. This may indicate experimenter bias, or that better predictors have to be found or that a larger dataset has to be used to infer meaningful pedotransfer functions for saturated and near-saturated hydraulic conductivities. More research is in progress to further elucidate this question.

Jorda, Helena; Koestel, John; Jarvis, Nicholas

2014-05-01

135

Hydraulic parameter estimation by remotely-sensed top soil moisture observations with the particle filter  

NASA Astrophysics Data System (ADS)

SummaryIn a synthetic study we explore the potential of using surface soil moisture measurements obtained from different satellite platforms to retrieve soil moisture profiles and soil hydraulic properties using a sequential data assimilation procedure and a 1D mechanistic soil water model. Four different homogeneous soil types were investigated including loamy sand, loam, silt, and clayey soils. The forcing data including precipitation and potential evapotranspiration were taken from the meteorological station of Aachen (Germany). With the aid of the forward model run, a synthetic data set was designed and observations were generated. The virtual top soil moisture observations were then assimilated to update the states and hydraulic parameters of the model by means of a particle filtering data assimilation method. Our analyses include the effect of assimilation strategy, measurement frequency, accuracy in surface soil moisture measurements, and soils differing in textural and hydraulic properties. With this approach we were able to assess the value of periodic spaceborne observations of top soil moisture for soil moisture profile estimation and identify the adequate conditions (e.g. temporal resolution and measurement accuracy) for remotely sensed soil moisture data assimilation. Updating of both hydraulic parameters and state variables allowed better predictions of top soil moisture contents as compared with updating of states only. An important conclusion is that the assimilation of remotely-sensed top soil moisture for soil hydraulic parameter estimation generates a bias depending on the soil type. Results indicate that the ability of a data assimilation system to correct the soil moisture state and estimate hydraulic parameters is driven by the non linearity between soil moisture and pressure head.

Montzka, Carsten; Moradkhani, Hamid; Weihermüller, Lutz; Franssen, Harrie-Jan Hendricks; Canty, Morton; Vereecken, Harry

2011-03-01

136

Effect of exchangeable Mg on saturated hydraulic conductivity, disaggregation and clay dispersion of disturbed soils  

Microsoft Academic Search

Different opinions exist regarding the specific effect of Mg on soil physical and chemical properties. We hypothesized that Mg2+, compared with Ca2+, reduces saturated hydraulic conductivity (Ks) via promoting clay swelling, disaggregation, and clay dispersion. Two soils (mixed, mesic Typic Hapludalfs) in packed soil columns were leached with either Ca- or Mg-containing solutions at the successive concentrations of 250, 10,

X. C Zhang; L. D Norton

2002-01-01

137

Hydraulic Properties of Rice and the Response of Gas Exchange to Water Stress1  

E-print Network

Hydraulic Properties of Rice and the Response of Gas Exchange to Water Stress1 Volker Stiller*, H.R.L.) We investigated the role of xylem cavitation, plant hydraulic conductance, and root pressure-specific photosynthetic rate, leaf diffusive conductance, and soil-leaf hydraulic conductance that were associated

Stiller, Volker

138

Dynamic aspects of soil water availability for isohydric plants: Focus on root hydraulic resistances  

NASA Astrophysics Data System (ADS)

Soil water availability for plant transpiration is a key concept in agronomy. The objective of this study is to revisit this concept and discuss how it may be affected by processes locally influencing root hydraulic properties. A physical limitation to soil water availability in terms of maximal flow rate available to plant leaves (Qavail) is defined. It is expressed for isohydric plants, in terms of plant-centered variables and properties (the equivalent soil water potential sensed by the plant, ?s eq; the root system equivalent conductance, Krs; and a threshold leaf water potential, ?leaf lim). The resulting limitation to plant transpiration is compared to commonly used empirical stress functions. Similarities suggest that the slope of empirical functions might correspond to the ratio of Krs to the plant potential transpiration rate. The sensitivity of Qavail to local changes of root hydraulic conductances in response to soil matric potential is investigated using model simulations. A decrease of radial conductances when the soil dries induces earlier water stress, but allows maintaining higher night plant water potentials and higher Qavail during the last week of a simulated 1 month drought. In opposition, an increase of radial conductances during soil drying provokes an increase of hydraulic redistribution and Qavail at short term. This study offers a first insight on the effect of dynamic local root hydraulic properties on soil water availability. By better understanding complex interactions between hydraulic processes involved in soil-plant hydrodynamics, better prospects on how root hydraulic traits mitigate plant water stress might be achieved.

Couvreur, V.; Vanderborght, J.; Draye, X.; Javaux, M.

2014-11-01

139

rosetta: a computer program for estimating soil hydraulic parameters with hierarchical pedotransfer functions  

Microsoft Academic Search

Soil hydraulic properties are necessary for many studies of water and solute transport but often cannot be measured because of practical and\\/or financial constraints. We describe a computer program, rosetta, which implements five hierarchical pedotransfer functions (PTFs) for the estimation of water retention, and the saturated and unsaturated hydraulic conductivity. The hierarchy in PTFs allows the estimation of van Genuchten

Marcel G. Schaap; Feike J. Leij; Martinus Th. van Genuchten

2001-01-01

140

Inverse modelling in estimating soil hydraulic functions: a Genetic Algorithm approach Hydrology and Earth System Sciences, 6(1), 4965 (2002) EGS  

E-print Network

and Earth System Sciences, 6(1), 49­65 (2002) © EGS Inverse modelling in estimating soil hydraulic functionsInverse modelling in estimating soil hydraulic functions: a Genetic Algorithm approach 49 Hydrology is sometimes hindered by the difficulty of deriving the soil hydraulic properties of the study area

Paris-Sud XI, Université de

141

Observations and Analysis of dynamic non equilibrium effects on soil hydraulic parameters  

NASA Astrophysics Data System (ADS)

In the past years, many scientists have observed dynamic non equilibrium effects on water flow in unsaturated soil where the Richard's equation fails to express the relationship between water content and hydraulic potential in the unsaturated zone. Until now, traditional techniques for determining soil hydraulic parameters have been used involving stepwise equilibrium imbibition and drainage experiments. More recently, optimization of the parameters describing the soil hydraulic functions in a transient outflow experiment using conventional methods have proved to be promising to derive soil hydraulic parameters but the estimates from one step outflow experiments using only cumulative outflow data in the objective function are often unreliable and non-unique. This work is an attempt to calculate the soil hydraulic properties using multi step outflow experiment data with different soil samples from Little Washita watershed, Oklahoma. The new dual fraction model (Diamantopolous et. al., 2012) in which water flow is treated as two fractions, one fraction with water in equilibrium with the pressure head whereas water in the second fraction as in non-equilibrium, has been used to ascertain the soil hydraulic parameters. Genetic Algorithm (GA) has been used to optimize the inverse solution of soil hydraulic parameters and to estimate uncertainties of calculated parameters using multi-populations within GA and by considering data and modeling errors. The authors aim to use the present work to be a stepping stone for calculation of dynamic non-equilibrium effects on soil hydraulic parameters estimation on greater (field) scale. The concern about dynamic non equilibrium effect on larger scale is still unanswered satisfactorily, because of conflicting hypothesized reasons such as: 1. Air entrapment is not expected to occur under natural drainage conditions, 2. erratic change in pressure at the system boundary unlike MSO experiments differ from that occurring in natural conditions. Simulated soil moisture values will be validated against observed air borne remotely sensed data soil moisture data.

Rana, S.; Mohanty, B.

2013-12-01

142

Unsaturated soil hydraulic conductivity: The field infiltrometer method  

Technology Transfer Automated Retrieval System (TEKTRAN)

Theory: Field methods to measure the unsaturated soil hydraulic conductivity assume presence of steady-state water flow. Soil infiltrometers are desired to apply water onto the soil surface at constant negative pressure. Water is applied to the soil from the Marriott device through a porous membrane...

143

Hydraulic conductivity prediction for sandy soils.  

PubMed

The potential for petroleum-contaminated soils to impact ground water is evaluated using the soil leachability model in South Carolina and Georgia. In this model, the Green and Ampt (1911) equation is used to estimate unsaturated flow with saturated hydraulic conductivity (K(S)) values obtained using the Rawls and Brakensiek (1989) equation from inputs of percent sand- and clay-sized particles. However, many soils have > 70% sand-sized particles, which is the maximum amount for which the Rawls and Brakensiek equation is valid. Therefore, 70 sets of K(S) and particle-size data from the literature for southeastern United States sandy soils were analyzed to develop a new equation for estimating K(S). A multiple linear regression model with an adjusted R2 = 0.65 (p < 0.0001) was developed from percent clay- and sand-sized particle data. Eight additional sets of data were used to validate the model. The root mean square deviation and maximum squared difference, (yi - yi(2)), values for the new model are smaller than those obtained using the Rawls and Brakensiek equation, or Rosetta, a neural network-based model (Schaap 1999). The new model provides estimates that are within an order of magnitude for all but one of the test data sets. Rosetta predicts K(S) within one order of magnitude of measured values for six test data, and predicts K(S) within two orders of magnitude for the other two. The Rawls and Brakensiek predictions are within one order of magnitude for four test data, but are two or more orders of magnitude too high for the remaining four points. The new equation is recommended for estimating K(S) for sandy southeastern United States soils for which inputs are limited to percent sand and clay. PMID:15161164

Cronican, Amy E; Gribb, Molly M

2004-01-01

144

Using Remotely-Sensed Estimates of Soil Moisture to Infer Soil Texture and Hydraulic Properties across a Semi-arid Watershed 1856  

Technology Transfer Automated Retrieval System (TEKTRAN)

Near-surface soil moisture is a critical component of land surface energy and water balance studies encompassing a wide range of disciplines. However, the processes of infiltration, runoff, and evapotranspiration in the vadose zone of the soil are not easy to quantify or predict because of the diff...

145

HYDRAULIC REDISTRIBUTION OF SOIL WATER IN TWO OLD-GROWTH CONIFEROUS FORESTS: QUANTIFYING PATTERNS AND CONTROLS  

EPA Science Inventory

Although hydraulic redistribution of soil water (HR) by roots is a widespread phenomenon, the processes governing spatial and temporal patterns of HR are not well understood. We incorporated soil/plant biophysical properties into a simple model based on Darcy's law to predict sea...

146

Characterizing Scale and Location-Dependent Correlation of Water Retention Parameters with Soil Physical Properties Using Wavelet Techniques  

Microsoft Academic Search

Understanding the correlation between soil hydraulic parameters and soil physical properties is a prerequisite for the prediction of soil hydraulic properties from soil physical properties. Th e objective of this study was to examine the scale- and location-dependent correlation between two water retention parameters (? and n) in the van Genuchten (1980) function and soil physical properties (sand content, bulk

Qiaosheng Shu; Zuoxin Liu; Bingcheng Si

2008-01-01

147

FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS  

EPA Science Inventory

Hydraulic fracturing, a technique commonly used to increase the yields of oil wells, could improve the effectiveness of several methods of in situ remediation. This project consisted of laboratory and field tests in which hydraulic fractures were created in soil. Laboratory te...

148

Appendix A. Hydraulic Properties Statistics Tables Table A1. Hydraulic properties statistics for the alluvium (Stephens et al.).  

E-print Network

A-1 Appendix A. Hydraulic Properties Statistics Tables Table A1. Hydraulic properties statistics Deviation .1708 4.274 28.95 Harmonic Mean Number of Observations 9 8 8 2 2 2 2 2 Table A2. Hydraulic.3Ã?10-5 Number of Observations 10 10 10 34 34 4 4 4 #12;A-2 Table A3. Hydraulic properties statistics

149

[Spatial variation characteristics of surface soil water content, bulk density and saturated hydraulic conductivity on Karst slopes].  

PubMed

Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infiltration and runoff generation, which will contribute to the reasonable utilization of soil water resources in mountainous areas. Based on a grid sampling scheme (10 m x 10 m) and geostatistical methods, this paper aimed to study the spatial variability of surface (0-10 cm) soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope (90 m x 120 m, projected length) in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hydraulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi- ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively (P < 0.01) correlated with the bulk density and saturated hydraulic conductivity, while there was no significant correlation between the soil bulk density and saturated hydraulic conductivity. PMID:25223011

Zhang, Chuan; Chen, Hong-Song; Zhang, Wei; Nie, Yun-Peng; Ye, Ying-Ying; Wang, Ke-Lin

2014-06-01

150

Pedotransfer functions: bridging the gap between available basic soil data and missing soil hydraulic characteristics  

Microsoft Academic Search

Water retention and hydraulic conductivity are crucial input parameters in any modelling study on water flow and solute transport in soils. Due to inherent temporal and spatial variability in these hydraulic characteristics, large numbers of samples are required to properly characterise areas of land. Hydraulic characteristics can be obtained from direct laboratory and field measurements. However, these measurements are time

J. H. M. Wösten; Ya. A. Pachepsky; W. J. Rawls

2001-01-01

151

Hydraulic Resistance of Soil Surface Seals in Irrigated Furrows  

Microsoft Academic Search

Soil surface seals resulting from overland flow in irrigation furrows reduce infiltration rates. A method was developed to quantify the hydraulic resistance of furrow seals. Infiltration was measured with a recirculating infiltrometer on two southern Idaho soils, Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid) and Bahem loam (coarse-silty, mixed, mesic Xerollic Calciorthids). Sur- face sealing was prevented on half

Antonius G. Segeren; Thomas J. Trout

1991-01-01

152

SATURATED HYDRAULIC CONDUCTIVITY OF SOILS BLENDED WITH WASTE FOUNDRY SANDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Beneficial uses are being sought after for the large quantities of waste foundry sand (WFS) that are landfilled. Potential applications include their use in synthetic soils and incorporation into agricultural soils. In this laboratory study we investigated the saturated hydraulic conductivity (Ks)...

153

Functional Relationships among Soil-air Permeability, Soil-gas Diffusivity, and Saturated Hydraulic Conductivity in Undisturbed Soils  

Microsoft Academic Search

Soil-pore geometric parameters including size distribution, total and air-filled porosity, pore tortuosity and connectivity strongly influence water and air flow in soils, and characterize soil-water and soil-gas transport parameters such as saturated hydraulic conductivity, soil-air permeability and soil-gas diffusivity. This study investigated functional relationships among the soil-pore dependent physical parameters in undisturbed soils and developed predictive expressions for soil-air permeability

K. Kawamoto; P. Moldrup; P. Schjønning; B. V. Iversen; T. Komatsu

2005-01-01

154

Topographic and soil hydraulic control of flow paths and soil contact time: Effects on surface-water acidification  

SciTech Connect

Topography and soil hydraulic properties are catchment attributes thought to influence the contact time of water in the soils and rocks of a catchment and the flow path followed by water as it traverses the catchment. Soil contact time and flow path, in turn, may affect the chemical composition of surface waters. The main objective of this dissertation is to determine to what extent variability in the topographic and soil hydraulic characteristics of catchments explains differences in the surface water acidification of those catchments. The theoretical framework of the hydrological model TOPMODEL was analyzed to determine how topographic and soil hydraulic catchment characteristics can be used to derive theoretical indices of flow path and soil contact time. These hydrological induces were derived from observed topography and soil hydraulic attributes and compared to observations of base flow alkalinity for 145 catchments in the Northeast US and to observations of storm flow acidity for 8 catchments in Wales. A significant proportion of the variability in base flow alkalinity for the catchments in the Northeast US was attributable to differences in the soil contact time index derived from catchment topography, soil depth and saturated hydraulic conductivity data. Generally, catchments with long soil contact time indices had higher base flow alkalinities. In addition, a large component of the variability in storm flow acidity for the catchments in Wales was explained by catchment differences in a flow path index based on topography. Storm flow acidity was higher in the catchments that were theoretically most likely to produce surface and near-surface runoff.

Wolock, D.M.

1988-01-01

155

Polyacrylamide effect on hydraulic conductivity of hardsetting soils in Northeast of Brazil  

NASA Astrophysics Data System (ADS)

Among soil hydro-physical properties, hydraulic conductivity is more sensitive to changes in soil structure. Hydraulic conductivity describes the ease with which a fluid (usually water) can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation, and on the density and viscosity of the fluid. Hardsetting soils present very low hydraulic conductivity values. When dry, these soils show high penetration resistance and consistency extremely hard, but change to friable when moist. In this condition are poorly structured, slaking when moist, limit agricultural machinery use and it may reduce the growth of the root system. In Brazil, these soils occur throughout of coastal zone in flat areas called "coastal tableland". Chemical ameliorant, such as polymers based on anionic polyacrylamide (PAM), improve hydraulic conductivity of soil in hardsetting soils. The primary functions of polyacrylamide soil conditioners are to increase soil tilth, aeration, and porosity and reduce compaction and water run-off. PAM effect is attributed to its ability to expand when placed in water, storing it in soil pore space, releasing it gradually to the plants. This process occurs by reducing the water flow through the pores of the soil, due to water molecules can be absorbed by PAM, providing water gradually. Thus, this study tested the hypothesis that PAM reduces the soil hardsetting character. The area is located in coastal zone in Goiana city, Pernambuco, northeastern of Brazil. This soil is typical hardsetting soil. Intact soil cores were collected from four horizons until 70cm depth. In the laboratory, the soil cores were saturated with different PAM concentrations (0.01, 0.005, 0.00125%) and H2O (control). Saturated hydraulic conductivity (Ksat) was determined using a constant head method, according to Klute and Dirksen (1986). Four replicates were used for each horizon and Tukey test at 5% probability was used by Assistat 7.6 beta. The sandy horizon had higher hydraulic conductivity in natural conditions, and the PAM, especially the concentration of 0.010%, reduced Ksat. This result confirms the action agglutinant of PAM organizing sand particles on aggregates, providing higher water retention, reducing water drainage and also Ksat values. In the other, especially in hardsetting horizon, when the lowest concentration (0.00125%) was applied reduced the effect of cohesion realized by increasing Ksat value. In conclude, PAM in hardsetting soils improve its physico-water proprieties when low concentrations.

Silva, Laércio; Almeida, Brivaldo; Melo, Diego; Marques, Karina; Almeida, Ceres

2013-04-01

156

Hydraulic conductivity of compacted soils controlled by microbial activity.  

PubMed

The hydraulic conductivity defines the displacement of liquids inside porous media and affects the fate and transport of contaminants in the environment. In this research the influence of microbial growth and decay inside soil pores on hydraulic conductivity is analysed. Long-term tests performed in silt-bentonite mixtures permeated with distilled water and a nutrients solution demonstrated that hydraulic conductivity of compacted silt-bentonite samples decreases with time of permeation as a bioclogging mechanism develops. The injection of antibiotics and antifungals in the specimens produces a rebound in the hydraulic conductivity associated with the decay of microbial activity. These results show that biomediated reactions can be used to control the flow rate through compacted soil liners. PMID:24956782

Glatstein, Daniel Alejandro; Francisca, Franco Matías

2014-08-01

157

Spatial variability of soil physical properties in Lodi plain  

Microsoft Academic Search

The knowledge of both soil physical properties and their spatial variability it is of crucial relevance for the understanding of the soil processes and for the land management. Soil hydraulic properties vary more or less continuously in geographical space and they can be regarded as regionalized variables. Geostatistical methods provide us a valuable tool to study their spatial structure and

Piero Manna; Gabriele Buttafuoco; Angelo Basile; Antonello Bonfante; Fulvio Fragnito; Fabio Terribile

158

Inverse modelling of in situ soil water dynamics: investigating the effect of different prior distributions of the soil hydraulic parameters  

NASA Astrophysics Data System (ADS)

In situ observations of soil water state variables under natural boundary conditions are often used to estimate the soil hydraulic properties. However, many contributions to the soil hydrological literature have demonstrated that the information content of such data is insufficient to accurately and precisely estimate all the soil hydraulic parameters. In this case study, we explored to which degree prior information about the soil hydraulic parameters can help improve parameter identifiability in inverse modelling of in situ soil water dynamics under natural boundary conditions. We used percentages of sand, silt, and clay as input variables to the ROSETTA pedotransfer function that predicts the parameters in the van Genuchten-Mualem (VGM) model of the soil hydraulic functions. To derive additional information about the correlation structure of the predicted parameters, which is not readily provided by ROSETTA, we employed a Monte Carlo approach. We formulated three prior distributions that incorporate to different extents the prior information about the VGM parameters derived with ROSETTA. The inverse problem was posed in a formal Bayesian framework and solved using Markov chain Monte Carlo (MCMC) simulation with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. Synthetic and real-world soil water content data were used to illustrate the approach. The results of this study demonstrated that prior information about the soil hydraulic parameters significantly improved parameter identifiability and that this approach was effective and robust, even in case of biased prior information. To be effective and robust, however, it was essential to use a prior distribution that incorporates information about parameter correlation.

Scharnagl, B.; Vrugt, J. A.; Vereecken, H.; Herbst, M.

2011-10-01

159

www.VadoseZoneJournal.org | 12011, Vol. 10 Soil Hydraulic Functions  

E-print Network

of Air Permeability, Capillary Modeling and High-Dimensional Parameter Estimation Prediction of flow properties) is essential for prediction of flow and transport through unsaturated porous media such as soilswww.VadoseZoneJournal.org | 12011, Vol. 10 Soil Hydraulic Functions Determined from Measurements

Vrugt, Jasper A.

160

Centrifuge Permeameter for Unsaturated Soils. II: Measurement of the Hydraulic Characteristics  

E-print Network

Centrifuge Permeameter for Unsaturated Soils. II: Measurement of the Hydraulic Characteristics and hydraulic conductivity function K function , determined using a new centrifuge permeameter developed hydraulic characteristics of the compacted clay. The SWRCs and K functions defined using the centrifuge

Zornberg, Jorge G.

161

Numerical modeling of consolidation processes in hydraulically deposited soils  

NASA Astrophysics Data System (ADS)

Hydraulically deposited soils are encountered in many common engineering applications including mine tailing and geotextile tube fills, though the consolidation process for such soils is highly nonlinear and requires the use of advanced numerical techniques to provide accurate predictions. Several commercially available finite element codes poses the ability to model soil consolidation, and it was the goal of this research to assess the ability of two of these codes, ABAQUS and PLAXIS, to model the large-strain, two-dimensional consolidation processes which occur in hydraulically deposited soils. A series of one- and two-dimensionally drained rectangular models were first created to assess the limitations of ABAQUS and PLAXIS when modeling consolidation of highly compressible soils. Then, geotextile tube and TSF models were created to represent actual scenarios which might be encountered in engineering practice. Several limitations were discovered, including the existence of a minimum preconsolidation stress below which numerical solutions become unstable.

Brink, Nicholas Robert

162

Soil Properties and Geomorphology  

NSDL National Science Digital Library

To prepare for this exercise, the students have been lectured on soil formation and on a field trip, described a simple soil within loess. Here, the students use data collected from a chronosequence to compare the relative age and amount of soil formation on a series of fluvial terraces. The students are to insert the data into a graphic program and generate specific graphs of soil properties. The students then interpret the amount of soil formation compared to the relative age of the fluvial terraces. Finally, the students assess how the 5 soil forming factors (climate, organisms, relief, parent material, and time) influenced soil formation in this setting. Designed for a geomorphology course

Mark Sweeney

163

Experimental Determination of Hydraulic Properties of Unsaturated Calcarenites  

NASA Astrophysics Data System (ADS)

Understanding hydraulic properties is essential in the modeling of flow and solute transport through the vadose zone, to which problems of soil and groundwater pollution are related. The vadose zone, in fact, is of great importance in controlling groundwater recharge and transport of contaminants into and through the subsoil. The aim of this work is to determine experimentally in laboratory the hydraulic properties of unsaturated calcarenites using an approach including petrophysical determinations and methods for measuring water retention. For this purpose, samples of calcarenites belonging to the Calcarenite di Gravina Fm.(Pliocene-early Pleistocene), came from two different quarry districts located in Southern Italy (Canosa di Puglia and Massafra), were utilized. The water retention function, ?(h), which binds the water content, ?, to water potential, h, was determined in the laboratory by means two different experimental methods: the WP4-T psychrometer and the suction table. At last, a simple mathematical equation represented by van Genuchten's model is fitted to the experimental data and the unknown empirical parameters of this model are determined. Textural analysis on thin sections using optical petrographic microscopy and evaluation of total and effective porosity by means of standard geotechnical laboratory tests, mercury intrusion porosimetry and image analysis were also performed. In particular, a comparison between mercury porosimetry data and results of photomicrograph computer analysis through the methods of quantitative stereology was employed for providing pore size distributions. The results of this study identify the relationship between the hydraulic behavior, described by the water retention function, and pore size distribution for the calcarenites that are not easy to hydraulically characterize. This relationship could represent a useful tool to infer the unsaturated hydraulic properties of calcarenites and in general this approach could be applied to be used for different kinds of rocks.

Turturro, Antonietta Celeste; Andriani, Gioacchino Francesco; Clementina Caputo, Maria; Maggi, Sabino

2013-04-01

164

ORIGINAL PAPER Hydraulic properties and embolism in small-diameter  

E-print Network

ORIGINAL PAPER Hydraulic properties and embolism in small-diameter roots of five temperate broad & Context It has been estimated that about half of a plant's total hydraulic resistance is located belowground, but it is not well known how temperate tree species differ in root hydraulic properties and how

Paris-Sud XI, Université de

165

In situ separation of root hydraulic redistribution of soil water from liquid and vapor transport  

SciTech Connect

Nocturnal increases in water potential ( ) and water content (WC) in the upper soil profile are often attributed to root water efflux into the soil, a process termed hydraulic lift or hydraulic redistribution (HR). We have previously reported HR values up to ~0.29 mm day-1 in the upper soil for a seasonally dry old-growth ponderosa pine site. However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the diurnal patterns in WC, confounding efforts to determine the actual magnitude of HR. In this study, we estimated liquid (Jl) and vapor (Jv) soil water fluxes and their impacts on quantifying HR in situ by applying existing data sets of , WC, temperature (T) and soil physical properties to soil water transport equations. Under moist conditions, Jl between layers was estimated to be larger than necessary to account for measured nocturnal increases in WC of upper soil layers. However, as soil drying progressed unsaturated hydraulic conductivity declined rapidly such that Jl was irrelevant (< 2E-06 cm hr-1 at 0-60 cm depths) to total water flux by early August. In surface soil at depths above 15 cm, large T fluctuations can impact Jv leading to uncertainty concerning the role, if any, of HR in nocturnal WC dynamics. Vapor flux was estimated to be the highest at the shallowest depths measured (20 - 30 cm) where it could contribute up to 40% of hourly increases in nocturnal soil moisture depending on thermal conditions. While both HR and net soil water flux between adjacent layers contribute to WC in the 15-65 cm soil layer, HR was the dominant process and accounted for at least 80% of the diurnal increases in WC. While the absolute magnitude of HR is not easily quantified, total diurnal fluctuations in upper soil water content can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total ecosystem water flux.

Warren, Jeffrey [ORNL; Brooks, J Renee [U.S. Environmental Protection Agency, Corvallis, OR; Dragila, Maria [Oregon State University, Corvallis; Meinzer, Rick [USDA Forest Service

2011-01-01

166

Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net ecosystem  

E-print Network

Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net sap flow, soil water content, understory, water potential. Summary · Hydraulic redistribution (HR hydraulic redistribution (HR), involves passive transfer of water from moist to drier portions of the soil

Noormets, Asko

167

Hydraulic conductivity estimation for soils with heterogeneous pore structure  

Microsoft Academic Search

The hydraulic conductivity function, which is required to solve the Richards equation, is difficult to measure. Therefore prediction methods are frequently used where the shape of the conductivity function is estimated from the more easily measured water retention characteristic. Errors in conductivity estimations can arise either from an invalidity of the prediction model for a given soil, or from an

Wolfgang Durner

1994-01-01

168

FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS  

EPA Science Inventory

Hydraulic fracturing, a method of increasing fluid flow within the subsurface, should improve the effectiveness of several remedial techniques, including pump and treat, vapor extraction, bio-remediation, and soil-flushing. he technique is widely used to increase the yields of oi...

169

Influence of spatial variability of hydraulic characteristics of soils on surface parameters obtained from remote sensing data in infrared and microwaves  

NASA Technical Reports Server (NTRS)

The correct interpretation of thermal and hydraulic soil parameters infrared from remotely sensed data (thermal infrared, microwaves) implies a good understanding of the causes of their temporal and spatial variability. Given this necessity, the sensitivity of the surface variables (temperature, moisture) to the spatial variability of hydraulic soil properties is tested with a numerical model of heat and mass transfer between bare soil and atmosphere. The spatial variability of hydraulic soil properties is taken into account in terms of the scaling factor. For a given soil, the knowledge of its frequency distribution allows a stochastic use of the model. The results are treated statistically, and the part of the variability of soil surface parameters due to that of soil hydraulic properties is evaluated quantitatively.

Brunet, Y.; Vauclin, M.

1985-01-01

170

Seasonal variability of near-saturated hydraulic conductivity on cultivated soil  

NASA Astrophysics Data System (ADS)

The soil structure and hydraulic properties of arable soils considerably vary during the year due to the periodical tillage and fertilization activities, soil compaction, plant and root grow, climate impact etc. The knowledge of the effect of temporal soil variability is essential when assessing water regime and associated dissolved substance transport in soils. The main aim of this contribution is to describe the temporal development of unsaturated hydraulic conductivity on arable land during a year. The experimental site is located in Nucice catchment (Central Bohemia, Czech republic), where also rainfall-runoff and soil erosion processes are studied. The soil is classified as Cambisol, typical texture ranges from loam to clay loam classes. Soil is conservatively tilled till depth of approximately 17 cm, below the topsoil a compacted subsoil was observed. Tension infiltration experiments were performed repeatedly at single location in order to determine the unsaturated hydraulic conductivity of the topsoil. So far four tension infiltration campaigns were carried out under tension h0 = -3.0 cm with different field conditions: (i) young winter barley (October 2012), (ii) between postharvest stubble breaking and seeding (April 2013), (iii) full-grown oat (June 2013) and (iv) after fresh postharvest stubble breaking (October 2013). Measurements were carried out using newly introduced automated multi minidisk tension infiltrometer (Klipa et al., EGU2014-7230). All experiments were performed on the levelled soil surface after removing upper soil layer (1 to 3 cm). A thin layer of quartz sand (thickness 1 - 2 mm, grain size 0.1 - 0.6 mm) was applied to improve contact between the infiltrometer and the soil surface. Each infiltration campaign consisted of six tension infiltration experiments, the total number of 24 infiltration data sets was obtained for this study. Results show that unsaturated hydraulic conductivity was significantly smaller in April, but rather the same in the remaining cases. Based on the monitoring of the water regime on the catchment, the infiltration capacity of the soil profile is decreasing during the season. This indicates that the hydraulic properties of the aggregates are stable. The limited infiltration is caused by the changing ratio of the inter-aggregare voids and the soil crusting (Zumr et al., EGU2014-7292). Measured data are part of a broader data base which is formed in order to the study the rainfall runoff and erosion processes on the agriculturally managed catchment.

Klípa, Vladimír; Zumr, David; Sn?hota, Michal

2014-05-01

171

Onset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water dynamics from millimeters to meters  

NASA Astrophysics Data System (ADS)

Estimation of water uptake by plants and subsequent water stress are complicated by the need to resolve the soil-plant hydrodynamics at scales ranging from millimeters to meters. Using a simplified homogenization technique, the three-dimensional (3-D) soil water movement dynamics can be reduced to solving two 1-D coupled Richards' equations, one for the radial water movement toward rootlets (mesoscale, important for diurnal cycle) and a second for vertical water motion (macroscale, relevant to interstorm timescales). This approach allows explicit simulation of known features of root uptake such as diurnal hysteresis in canopy conductance, hydraulic lift, and compensatory root water uptake during extended drying cycles. A simple scaling analysis suggests that the effectiveness of the hydraulic lift is mainly controlled by the root vertical distribution, while the soil moisture levels at which hydraulic lift is most effective is dictated by soil hydraulic properties and surrogates for atmospheric water vapor demand.

Siqueira, Mario; Katul, Gabriel; Porporato, Amilcare

2008-01-01

172

USE OF LIMITED SOIL PROPERTY DATA AND MODELING TO ESTIMATE ROOT ZONE SOIL WATER CONTENT.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Modeling root zone soil water content at watershed scales is important for both the strategic and tactical management of water resources, but detailed soil physical and hydraulic property data required by most physically-based soil water models are generally not available over large land areas. Wit...

173

Description of the unsaturated soil hydraulic database UNSODA version 2.0  

NASA Astrophysics Data System (ADS)

Quantifying water flow and chemical transport in the vadose zone typically requires knowledge of the unsaturated soil hydraulic properties. The UNsaturated SOil hydraulic DAtabase (UNSODA) was developed to provide a source of unsaturated hydraulic data and some other soil properties for practitioners and researchers. The current database contains measured soil water retention, hydraulic conductivity and water diffusivity data as well as pedological information of some 790-soil samples from around the world. A first MS-DOS version of the database was released in 1996. It has been applied in numerous studies. In this paper, we describe the second version (UNSODA V2.0) for use with Microsoft Access-97 ®. The format and structure of the new database have been modified to provide additional and more convenient options for data searches, to provide compatibility with other programs for easy loading and downloading of data, and to allow users to customise the contents and look of graphical output. This paper reviews the structure and contents of the database as well as the operations that can be performed on the different data types in UNSODA V2.0. The use and application of the new database are illustrated with two examples. The retrieval of data is briefly illustrated, followed by a more detailed example regarding the interpolation of soil particle-size distribution data obtained according to different national definitions of particle-size classes. The interpolation procedure, which is based on finding similar particle-size distribution curves from a large European data set, also performed well for soils that originate from other geographical areas. Trade names are provided for the benefit of the reader and do not imply an endorsement by the authors or their organizations.

Nemes, A.; Schaap, M. G.; Leij, F. J.; Wösten, J. H. M.

2001-10-01

174

Systematic Variability of Soil Hydraulic Conductivity Across Three Vertisol Catenas  

E-print Network

Soil formation processes result in a systematic change of soil properties across the landscape, described in the concept of a catena (Opp, 1994). Although some studies have been conducted looking at the spatial and temporal variations of soil.... Characterizing the impacts of soil properties that might vary systematically with land use and terrain attributes on Ks rates would provide insight on how management and human activity affect local and regional hydrology. The overall objective of this research...

Rivera, Leonardo Daniel

2011-10-21

175

Novel method for the simultaneous quantification of soil hydraulic functions in the laboratory under consideration of shrinkage  

NASA Astrophysics Data System (ADS)

Knowledge about the soil hydraulic properties - water retention curve and unsaturated hydraulic conductivity - is required for soil water modelling and various soil hydrological studies. In general, soils and their pore size system are assumed to be rigid during the loss of water on drying. This is different from reality for many soils, especially for soils with high contents of clay or organic matter which are shrinking dependent on the pore pressure. As a result, the porosity, the pore size distribution and the bulk density of these soils are changing. Measurements of soil hydraulic functions with the classical methods are time consuming, the equipment is costly and the measuring results are affected by uncertainties. Methods enabling the quantification of soil hydraulic functions under consideration of shrinkage are missing. A method frequently used for the simultaneous determination of both the hydraulic functions of unsaturated soil samples is the evaporation method. Due to the limited range of common tensiometers, all methodological variations of the evaporation method in the past suffered from the limitation that the hydraulic functions could only be determined to a maximum tension of 50 kPa. The extended evaporation method (EEM) overcomes this restriction. Using new boyling delay tensiometers and applying the air-entry pressure of the tensiometer's porous ceramic cup as final tension value allows the quantification of the soil hydraulic functions in a range to close to the wilting point. Based on EEM a practicable method was developed which additionally allows the consideration of shrinkage. The experimental setup followed the system HYPROP which is a commercial device with vertically aligned tensiometers that is optimized to perform evaporation measurements. Preliminary investigations were conducted to study the geometrical change of 24 samples different in texture and origin. The samples were enwrapped with a rubber membrane impermeable for water and air. The sample height and the sample circumference were detected during drying. The results confirmed (i) isotropic shrinkage and (ii) a quite linear decrease of the sample circumference from the bottom to the top of the sample. As a conclusion, for quantifying the volume change of the sample during evaporation it should be sufficient to measure the changing circumference in the middle position of the cylindrical sample. Together with the recorded tensions and the sample mass, the soil hydraulic functions could be quantified in the range between saturation and close to the permanent wilting point in consideration of shrinkage. Common soil hydraulic data models could be fitted to the soil hydraulic and shrinkage data.

Schindler, Uwe; Mueller, Lothar

2013-04-01

176

HYDRAULIC AND PHYSICAL PROPERTIES OF MCU SALTSTONE  

SciTech Connect

The Saltstone Disposal Facility (SDF), located in the Z-Area of the Savannah River Site (SRS), is used for the disposal of low-level radioactive salt solution. The SDF currently contains two vaults: Vault 1 (6 cells) and Vault 4 (12 cells). Additional disposal cells are currently in the design phase. The individual cells of the saltstone facility are filled with saltstone., Saltstone is produced by mixing the low-level radioactive salt solution, with blast furnace slag, fly ash, and cement or lime to form a dense, micro-porous, monolithic, low-level radioactive waste form. The saltstone is pumped into the disposal cells where it subsequently solidifies. Significant effort has been undertaken to accurately model the movement of water and contaminants through the facility. Key to this effort is an accurate understanding of the hydraulic and physical properties of the solidified saltstone. To date, limited testing has been conducted to characterize the saltstone. The primary focus of this task was to estimate the hydraulic and physical properties of MCU (Modular Caustic Side Solvent Extraction Unit) saltstone relative to two permeating fluids. These fluids included simulated groundwater equilibrated with vault concrete and simulated saltstone pore fluid. Samples of the MCU saltstone were prepared by the Savannah River National Laboratory (SRNL) and allowed to cure for twenty eight days prior to testing. These samples included two three-inch diameter by six inch long mold samples and three one-inch diameter by twelve inch long mold samples.

Dixon, K; Mark Phifer, M

2008-03-19

177

Biochar-Induced Changes in Soil Hydraulic Conductivity and Dissolved Nutrient Fluxes Constrained by Laboratory Experiments  

PubMed Central

The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent. PMID:25251677

Barnes, Rebecca T.; Gallagher, Morgan E.; Masiello, Caroline A.; Liu, Zuolin; Dugan, Brandon

2014-01-01

178

Hydraulic properties of leaves from desert shrubs  

SciTech Connect

Changes in certain tissue hydraulic properties such as elasticity, capacitance, and resistance to water flow were considered as a function of leaf water content. It has been suggested in the literature that variation in such properties may be of significance during changes in leaf hydration. In addition, the author was interested in the potential role of changes in these same tissue properties for maintaining leaf water status during drought. Two shrubs occurring in the Mojave desert, mesquite and live-oak, were studied. Measurements suggest that over the range of leaf water potential from zero to turgor loss, the elastic modulus varies 5-fold, capacitance varies 2-fold, and the resistance to flow between the xylem and storage in the leaf parenchyma tissues 2 to 3-fold. A model for water flow was developed based on these and other tissue properties. This modeling approach is being used as a hypothesis-generating tool for future experimentation. Results of the modeling are discussed in the context of published speculations on the functional role of changes in properties such as elasticity for plants under water stress.

Schulte, P.J. (Univ. of Nevada, Las Vegas (United States))

1991-05-01

179

HYDRAULIC CONDUCTIVITY ESTIMATION IN PARTIALLY SATURATED SOILS USING THE ADJOINT METHOD  

E-print Network

HYDRAULIC CONDUCTIVITY ESTIMATION IN PARTIALLY SATURATED SOILS USING THE ADJOINT METHOD J. SANTOS for the estimation of the saturated hydraulic conductivity k in a partially saturated soil Q is proposed. Groundwater exam- ple showing the implementation of the algorithm to estimate the saturated hydraulic conductivity

Efendiev, Yalchin

180

ReproducedfromVadoseZoneJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Soil Hydraulic Parameter Upscaling for Steady-State Flow with Root Water Uptake  

E-print Network

Hydraulic Parameter Upscaling for Steady-State Flow with Root Water Uptake Jianting Zhu* and Binayak P in the upperIn this study we investigate effective soil hydraulic parameter aver- soil layer of spatially in heterogeneous soils. "Effective" soil hydraulic parameters of a hetero- ability of the saturated hydraulic

Mohanty, Binayak P.

181

Influence of urban land development and subsequent soil rehabilitation on soil aggregates, carbon, and hydraulic conductivity.  

PubMed

Urban land use change is associated with decreased soil-mediated ecosystem services, including stormwater runoff mitigation and carbon (C) sequestration. To better understand soil structure formation over time and the effects of land use change on surface and subsurface hydrology, we quantified the effects of urban land development and subsequent soil rehabilitation on soil aggregate size distribution and aggregate-associated C and their links to soil hydraulic conductivity. Four treatments [typical practice (A horizon removed, subsoil compacted, A horizon partially replaced), enhanced topsoil (same as typical practice plus tillage), post-development rehabilitated soils (compost incorporation to 60-cm depth in subsoil; A horizon partially replaced plus tillage), and pre-development (undisturbed) soils] were applied to 24 plots in Virginia, USA. All plots were planted with five tree species. After five years, undisturbed surface soils had 26 to 48% higher levels of macroaggregation and 12 to 62% greater macroaggregate-associated C pools than those disturbed by urban land development regardless of whether they were stockpiled and replaced, or tilled. Little difference in aggregate size distribution was observed among treatments in subsurface soils, although rehabilitated soils had the greatest macroaggregate-associated C concentrations and pool sizes. Rehabilitated soils had 48 to 171% greater macroaggregate-associated C pool than the other three treatments. Surface hydraulic conductivity was not affected by soil treatment (ranging from 0.4 to 2.3 cm h(-1)). In deeper regions, post-development rehabilitated soils had about twice the saturated hydraulic conductivity (14.8 and 6.3 cm h(-1) at 10-25 cm and 25-40 cm, respectively) of undisturbed soils and approximately 6-11 times that of soils subjected to typical land development practices. Despite limited effects on soil aggregation, rehabilitation that includes deep compost incorporation and breaking of compacted subsurface layers has strong potential as a tool for urban stormwater mitigation and soil management should be explicitly considered in urban stormwater policy. PMID:25064620

Chen, Yujuan; Day, Susan D; Wick, Abbey F; McGuire, Kevin J

2014-10-01

182

Atlas of soil reflectance properties  

NASA Technical Reports Server (NTRS)

A compendium of soil spectral reflectance curves together with soil test results and site information is presented in an abbreviated manner listing those soil properties most important in influencing soil reflectance. Results are presented for 251 soils from 39 states and Brazil. A narrative key describes relationships between soil parameters and reflectance curves. All soils are classified according to the U.S. soil taxonomy and soil series name for ease of identification.

Stoner, E. R.; Baumgardner, M. F.; Biehl, L. L.; Robinson, B. F.

1979-01-01

183

Agricultural use of soil, consequences in soil organic matter and hydraulic conductivity compared with natural vegetation in central Spain  

NASA Astrophysics Data System (ADS)

When ecosystems are under pressure due to high temperatures and water scarcity, the use of land for agriculture can be a handicap for soil and water conservation. The interactions between plants and soils are site-specific. This study provides information about the influence of the preence vs. The absence of vegetation on soil in a semi-arid area of the sout-east of Madrid (Spain, in the Tagus River basin. In this area soil materials are developed over a calcareous-evaporitic lithology. Soils can be classified as Calcisols, having horizons of accumulation with powdered limestone and irregular nodules of calcium carbonate. They can be defined as Haplic Cambisols and Leptic Calcisols (WRB 2006-FAO). The area is mainly used for rainfed agriculture, olive groves, vineyards and cereals. There are some patches of bushes (Quercus sp.) and grasses (Stipa tenacissima L.) although only found on the top of the hills. This study analyses the differences found in soils having three different covers: Quercus coccifera, Stipa tenacissima and lack of vegetation. This last condition was found in the areas between cultivated olive trees. Soil organic matter, porosity and hydraulic conductivity are key properties of soil to understand its ability to adapt to climate or land use changes. In order to measure the influence of different soil covers, four replicates of soil were sampled in each condition at two soil depth, (0-10 cm and 10-20 cm). Hydraulic conductivity was measured in each soil condition and replicate using a Mini-disk® infiltrometer. There were no differences between the two depths sampled. Similarly, there were no changes in electric conductivity (average 0.1±0.03 dS m-1); pH (8.7±0.2) or calcium carbonate content (43±20 %). Nevertheless, significant differences (p>0.001) were found in soil organic matter. The maximum was found in soils under Quercus (4.7±0.5 %), followed by Stipa (2.2±1.1 %). The soil without vegetation in the areas between olive trees had only 0.7±1.1 % soil organic matter; far from the usual limit advisable for cultivated soils. Soil porosity was also affected in cultivated soils, being 39±5% (total porosity), significantly less than those found under Stipa (46%) and Quercus (51%). Hydraulic conductivity presented a similar pattern to porosity, being higher in soils under Quercus, however further research is needed to clarify this result, as it can also be related to changes detected in soil texture. Sand content, which was different between soil conditions, is highly correlated to hydraulic conductivity. Changes in soil texture can be due to erosive processes that have to be studied to establish the causative relationships between these findings. Acknowledgements: Project CGL 2008-04296. Environmental Impact evaluation through the assessment of soil organic matter resilient forms in soils.

Vega, Verónica; Carral, Pilar; Alvarez, Ana Maria; Marques, Maria Jose

2014-05-01

184

Relationship between the hydraulic conductivity and electric properties for investigating the alluvium aquifer  

NASA Astrophysics Data System (ADS)

In this study, to understand relationship between hydraulic conductivity and electrical properties in alluvial aquifer, some indoor experiments and field electrical surveys were conducted. Soil sampled from alluvial aquifer and various size of quartz sand particles were saturated in NaCl solution which had 100 ohm-m. Then their porosity, hydraulic conductivity, time domain induced polarization and spectral induced polarization were measured. As a result, hydraulic conductivity and resistivity of quartz sand had proportional relation but, chargeability and phase difference of it showed small value also, hydraulic conductivity did not show clear tendency. Through this experiment, it was possible to identify which quartz sand had almost no response from induced polarization survey. Moreover, for silty sand, hydraulic conductivity and resistivity had proportional relation, hydraulic conductivity and chargeability had inverse proportional relation and hydraulic conductivity and phase difference had proportional relation. Through this experiment, silty sand showed correlation between hydraulic conductivity and electrical property. When field resistivity survey was conducted at alluvial aquifer, it showed wider range of values than the values from indoor experiment. Therefore, it is difficult to estimate accurate hydraulic conductivity of alluvial aquifer by applying hydraulic conductivity-resistivity interaction formula from indoor experiment to field resistivity survey. However, through comparison between resistivity survey result and borehole data, it was acknowledged that parts with low resistivity were clayey stratum and parts with high resistivity were gravel stratum. Consequently, estimating relative hydraulic conductivity distribution was able to be determined. However, followed by result of time domain induced polarization survey, clayey sand stratum did not have high chargeability. Through this field induced polarization survey experiment, it looks difficult to estimate hydraulic conductivity distribution.

Park, Samgyu; Kim, Soodong; Hamm, Se-Yeong

2014-05-01

185

ORIGINAL PAPER Genetic variation of xylem hydraulic properties shows  

E-print Network

ORIGINAL PAPER Genetic variation of xylem hydraulic properties shows that wood density is involved understanding of the role of wood density in the hydraulic properties of xylem and may clarify the role of wood to cell wall proportion of the xylem is closely related to wood density (Bucci et al. 2004; Hacke et al

Boyer, Edmond

186

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates  

NASA Astrophysics Data System (ADS)

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding the achievability of water quality targets.

Vero, S. E.; Ibrahim, T. G.; Creamer, R. E.; Grant, J.; Healy, M. G.; Henry, T.; Kramers, G.; Richards, K. G.; Fenton, O.

2014-12-01

187

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates.  

PubMed

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding the achievability of water quality targets. PMID:25444116

Vero, S E; Ibrahim, T G; Creamer, R E; Grant, J; Healy, M G; Henry, T; Kramers, G; Richards, K G; Fenton, O

2014-12-01

188

Percolation testing and hydraulic conductivity of soils for percolation areas.  

PubMed

The results of specific percolation tests are expressed in terms of field saturated hydraulic conductivity (Kfs) of the soil. The specific tests comprise the Irish SR 6 and the UK BS 6297 standard tests and the inversed auger hole and square hole tests employed for the design of land drainage. Percolation times from these tests are converted to Kfs values using unit gradient theory and the Elrick and Reynolds (Soil Sci. 142(5) (1986) 308) model which takes into account gravitational, pressure head and matric potential gradients. Kfs is then expressed as the inverse of the percolation rate times a constant, in this way the percolation rate can be directly related to Kfs of the soil. A plot of Kfs against percolation rate for the Irish SR 6 and the UK BS 6297 standard tests is asymptotic at Kfs values less than 0.2 m/d and greater than 0.8 m/d. This behaviour creates difficulty in setting limits for percolation rates in standards. Curves are provided which enable Kfs values to be read off from percolation tests without the restrictions of head range currently enforced, for example in the Irish SR 6 and BS 6297 standards. Experimental measurements of percolation rates and Kfs were carried out on two sands in the laboratory and in the field on two soils. Kfs of these four materials was also measured using a tension infiltrometer and the Guelph permeameter. The saturated hydraulic conductivities (Ks) of the sands were also estimated in a falling head laboratory apparatus and by the Hazen formula. There was good agreement between the different tests for Kfs on each material. Because percolation time continued to increase significantly in consecutive tests in the same test hole while Kfs became constant, the latter is a better measure of the suitability of soils for percolation. PMID:12230173

Mulqueen, J; Rodgers, M

2001-11-01

189

Simulating soil-water movement through loess-veneered landscapes using nonconsilient saturated hydraulic conductivity measurements  

USGS Publications Warehouse

Soil Survey Geographic Database (SSURGO) data are available for the entire United States, so are incorporated in many regional and national models of hydrology and environmental management. However, SSURGO does not provide an understanding of spatial variability and only includes saturated hydraulic conductivity (Ksat) values estimated from particle size analysis (PSA). This study showed model sensitivity to the substitution of SSURGO data with locally described soil properties or alternate methods of measuring Ksat. Incorporation of these different soil data sets significantly changed the results of hydrologic modeling as a consequence of the amount of space available to store soil water and how this soil water is moved downslope. Locally described soil profiles indicated a difference in Ksat when measured in the field vs. being estimated from PSA. This, in turn, caused a difference in which soil layers were incorporated in the hydrologic simulations using TOPMODEL, ultimately affecting how soil water storage was simulated. Simulations of free-flowing soil water, the amount of water traveling through pores too large to retain water against gravity, were compared with field observations of water in wells at five slope positions along a catena. Comparison of the simulated data with the observed data showed that the ability to model the range of conditions observed in the field varied as a function of three soil data sets (SSURGO and local field descriptions using PSA-derived Ksat or field-measured Ksat) and that comparison of absolute values of soil water storage are not valid if different characterizations of soil properties are used.

Williamson, Tanja N.; Lee, Brad D.; Schoeneberger, Philip J.; McCauley, W. M.; Indorante, Samuel J.; Owens, Phillip R.

2014-01-01

190

Application of EM38 and ERT methods in estimation of saturated hydraulic conductivity in unsaturated soil  

NASA Astrophysics Data System (ADS)

Soil apparent electrical conductivity is being considerably used as a surrogate measure for soil properties and hydraulic parameters. In this study, measurements of electrical conductivity were accomplished with electrical resistivity tomography (ERT) and EM38 to develop multiple datasets for defining spatiotemporal moisture content variations and estimating saturated hydraulic conductivity under natural conditions in an experimental site located in Lisbon, Portugal. In addition, EM38 capability in monitoring electrical conductivity variations in comparison with ERT method was examined. In order to achieve these objectives, appropriate relationships were derived based on determination of experimental curve resistivity vs. degree of saturation by in-situ investigation to convert electrical resistivity maps inferred from ERT and EM38 data to moisture content distribution maps. In addition, the surface temperature variations during the experiment were measured and the effects of the temperature variations were removed by assuming 2% change in electrical resistivity per °C change in temperature. The conducted experiment proves that the soil is fairly homogenous and semi-pervious sediment and the spatiotemporal moisture content variations during the experiment barely exceed 10%. Our calculations constrain the range of saturated hydraulic conductivity to be 3-9 (cm/day) range.

Farzamian, Mohammad; Monteiro Santos, Fernando A.; Khalil, Mohamed A.

2015-01-01

191

Gas diffusion-derived tortuosity governs saturated hydraulic conductivity in sandy soils  

NASA Astrophysics Data System (ADS)

The saturated hydraulic conductivity (Ksat) is an essential effective parameter for the development of improved distributed hydrological models and area-differentiated risk assessment of chemical leaching. Basic soil properties such as the particle size distribution or, more recently, air permeability are commonly used to estimate Ksat. Conversely, links to soil gas diffusivity (Dp/Do) have not been fully explored even though gas diffusivity is intimately linked to the connectivity and tortuosity of the soil pore network. Based on measurements for a coarse sandy soil, potential relationships between Ksat and Dp/Do were investigated. A total of 84 undisturbed soil cores were extracted from the topsoil of a field site, and Dp/Do and Ksat were measured in the laboratory. Water-induced and solids-induced tortuosity factors were obtained by applying a two-parameter Dp/Do model to measured data, and subsequently linked to the cementation exponent of the well-established Revil and Cathles predictive model for saturated hydraulic conductivity. Furthermore, a two-parameter model, analogue to the Kozeny-Carman equation, was developed for the Ksat - Dp/Do relationship. All analyses implied strong and fundamental relationships between Ksat and Dp/Do.

Masís-Meléndez, Federico; Chamindu Deepagoda, T. K. K.; de Jonge, Lis Wollesen; Tuller, Markus; Moldrup, Per

2014-05-01

192

Ecohydrological controls on soil moisture and hydraulic conductivity within a pinyon-juniper woodland  

USGS Publications Warehouse

The impact of pinyon-juniper woodland encroachment on rangeland ecosystems is often associated with a reduction of streamflow and recharge and an increase in soil erosion. The objective of this study is to investigate vegetational control on seasonal soil hydrologic properties along a 15-m transect in pinyon-juniper woodland with biocrust. We demonstrate that the juniper tree controls soil water content (SWC) patterns directly under the canopy via interception, and beyond the canopy via shading in a preferred orientation, opposite to the prevailing wind direction. The juniper also controls the SWC and unsaturated hydraulic conductivity measured close to water saturation (K(h)) under the canopy by the creation of soil water repellency due to needle drop. We use this information to refine the hydrologic functional unit (HFU) concept into three interacting hydrologic units: canopy patches, intercanopy patches, and a transitional unit formed by intercanopy patches in the rain shadow of the juniper tree. Spatial autoregressive state-space models show the close relationship between K(h) close to soil water saturation and SWC at medium and low levels, integrating a number of influences on hydraulic conductivity. Copyright 2007 by the American Geophysical Union.

Lebron, I.; Madsen, M.D.; Chandler, D.G.; Robinson, D.A.; Wendroth, O.; Belnap, J.

2007-01-01

193

Modelling the effect of rock fragment on soil saturated hydraulic conductivity  

NASA Astrophysics Data System (ADS)

Stoniness may be a key factor in determining the soil hydrological properties. Nevertheless, how coarse fraction takes part in some important processes (e.g., runoff, infiltration and percolation) is not univocally recognized, mainly because of the difficulties in obtaining reliable experimental data and, secondarily, for the employment of different approaches to evaluate the role of the coarse fraction. With that regard, equations developed by hydrogeologists to account for water fluxes in porous media, consider permeability as mere function of grain size distribution (particles >2 mm included), with permeability values increasing when passing from sand to gravel. Conversely, soil scientists consider the saturated hydraulic conductivity (Ksat) of soil exclusively as function of the fine-earth fraction and attribute a contrasting effect to the coarse fraction, both in relation to the decrease of porosity and to the increase of flow path tortuosity. Nevertheless, the Soil Survey Handbook includes all fragmental soils (gravel content ?35% by weight) into the highest class of soil hydraulic conductivity, and this partly disagrees with the mostly adopted soil scientists' approaches. At the same time, lab- experiments carried out by engineers on particle mixture point out that the addition of increasing amounts of coarse material to finer grains progressively reduces the overall porosity until a critical threshold is reached; beyond this level, the void proportion rises again. In relation to the engineers' results, the present paper attempts to conceptually approach the dual effects of rock fragment content on Ksat by considering a decay of the water transmission properties of the fine-earth fraction at low gravel contents and, conversely, a drastic improvement of the conductivity whenever the porosity increases. For that purpose a data set of 50 soils of different textural classes is used to define the procedure by virtually increasing the rock fragment fraction (SK) up to 99% by weight, meanwhile calculating the corresponding statistical descriptors (e.g., d10, dg, ??) of grain size distribution (GSD). For each sample of the data set, the procedure is based on the Ksat computation for increasing gravel content provided by both soil scientists' and hydrogeologists' approaches. Given that the two methods generate curves with different direction and slope, an intersection is obtained. Such a point indicates the minimum saturated hydraulic conductivity value, that can be conceptually interpreted as the minimum porosity (or the maximum density of the mixture) experimentally observed by engineers. Therefore, the procedure for assessing the resulting Ksat consists in adopting the soil scientists' approach until the intersection is reached and then following the hydrogeological curve beyond such threshold. The findings provided by two other approaches are compared with our results and discussed.

Pellegrini, Sergio; Costanza Andrenelli, Maria; Vignozzi, Nadia

2014-05-01

194

High-resolution hydraulic parameter maps for surface soils in tropical South America  

NASA Astrophysics Data System (ADS)

Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded datasets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten-Mualem and van Genuchten-Burdine soil hydraulic models, which are widely-used hydraulic sub-models in Land Surface Models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain database and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20 × higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally-parameterised and that are not just based on soil texture. Details are provided specifically on how to assemble the ancillary data files required for grid-based vegetation simulation using the Joint UK Land Environment Simulator (JULES). We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.

Marthews, T. R.; Quesada, C. A.; Galbraith, D. R.; Malhi, Y.; Mullins, C. E.; Hodnett, M. G.; Dharssi, I.

2013-12-01

195

High-resolution hydraulic parameter maps for surface soils in tropical South America  

NASA Astrophysics Data System (ADS)

Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded data sets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten-Mualem and van Genuchten-Burdine soil hydraulic models, which are widely used hydraulic sub-models in land surface models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain data base and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20x higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally parameterised and that are not just based on soil texture. We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.

Marthews, T. R.; Quesada, C. A.; Galbraith, D. R.; Malhi, Y.; Mullins, C. E.; Hodnett, M. G.; Dharssi, I.

2014-05-01

196

Hydraulic properties of the crystalline basement  

Microsoft Academic Search

Hydraulic tests in boreholes, up to 4.5 km deep, drilled into continental crystalline basement revealed hydraulic conductivity\\u000a (K) values that range over nine log-units from 10?13?10?4 m s?1. However, K values for fractured basement to about 1 km depth are typically restricted to the range from 10?8 to 10?6 m s?1. New data from an extended injection test at the KTB research site (part

Ingrid Stober; Kurt Bucher

2007-01-01

197

Hydraulic properties of adsorbed water films in unsaturated porous media  

SciTech Connect

Adsorbed water films strongly influence residual water saturations and hydraulic conductivities in porous media at low saturations. Hydraulic properties of adsorbed water films in unsaturated porous media were investigated through combining Langmuir's film model with scaling analysis, without use of any adjustable parameters. Diffuse double layer influences are predicted to be important through the strong dependence of adsorbed water film thickness (f) on matric potential ({Psi}) and ion charge (z). Film thickness, film velocity, and unsaturated hydraulic conductivity are predicted to vary with z{sup -1}, z{sup -2}, and z{sup -3}, respectively. In monodisperse granular media, the characteristic grain size ({lambda}) controls film hydraulics through {lambda}{sup -1} scaling of (1) the perimeter length per unit cross sectional area over which films occur, (2) the critical matric potential ({Psi}{sub c}) below which films control flow, and (3) the magnitude of the unsaturated hydraulic conductivity when {Psi} < {Psi}{sub c}. While it is recognized that finer textured sediments have higher unsaturated hydraulic conductivities than coarser sands at intermediate {Psi}, the {lambda}{sup -1} scaling of hydraulic conductivity predicted here extends this understanding to very low saturations where all pores are drained. Extremely low unsaturated hydraulic conductivities are predicted under adsorbed film-controlled conditions (generally < 0.1 mm y{sup -1}). On flat surfaces, the film hydraulic diffusivity is shown to be constant (invariant with respect to {Psi}).

Tokunaga, Tetsu K.

2009-03-01

198

Water repellency in an Alpine forest soil and its impact on hydraulic characteristics under simulated climate change  

NASA Astrophysics Data System (ADS)

The climate of Alpine environments is expected to change dramatically as a consequence of global climate change. In this ecologically sensitive environment, prolonged dry periods and an increased occurence of extreme rainfall events is forecasted by many climate change models. On the other hand, soil water repellency (SWR) is known to affect hydraulic processes in soils, particularly in acidic forest soils and as a consequence of prolonged dry periods. By changing the soil surface properties, SWR also changes the hydraulically effective properties of soils. The quantification of the spatial occurence and degree of hydrophobicity is a crucial prerequirement for ecological and hydrological impact assessment and developing new models. Therefore, the objective of the present study was to quantify soil water repellency in an Alpine forest with respect to its spatial variability and affected by different simulated climatic regimes. The study was accomplished in the Rosalian mountains, some 60 km south of Vienna, Austria. The vegetation was a mature beech forest and the soil was a Podsolic Cambisol over weathered granitic rock debris. As parts of the experimental plot were covered by plastic roofs and artificially irrigated, three different treatments were tested: Compared to the natural precipitation (control), the irrigation amount was reduced with two drought degrees (moderate and extreme). Within a small grid, 9 samples were taken per treatment in two depths (surface and 0.10 m). The contact angle was determined with the modified sessile drop method. Additionally, total and organic carbon contents and the hydraulic soil properties were quantified. Infiltration experiments were performed with a tension infiltrometer using water and ethanol. The results showed considerable water repellency with at least subcritical contact angles for all treatments. Contact angles increased to above 90 degree at the moderate and extreme drought treatments. Differences between intrinsic and apparent hydraulic properties as reflected by the ethanol and water infiltration, respectively, increased with increasing drought degree.

Schwen, Andreas; Zimmermann, Michael; Lamparter, Axel; Woche, Susanne; Bachmann, Jörg

2014-05-01

199

Soils - Part 2: Physical Properties of Soil and Soil Water  

NSDL National Science Digital Library

This lesson will help you understand the major components of the physical properties of soil. You will learn such terms as texture, aggregation, soil structure, bulk density, and porosity as it relates to soils. You will learn how soil holds and transmits water and cultural practices that enhance or degrade physical properties of the soil.[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.

200

Transport Properties of Soils and Spectral Electrical Response: Equivalent Circuit Models  

NASA Astrophysics Data System (ADS)

Non-invasive prediction of hydraulic properties of soils (hydraulic conductivity, porosity, and degree of saturation) from surface measurement techniques as provided by geophysical methods is appealing to geoscientists involved in groundwater and pollution control problems. There is the need, however, to understand how the hydraulic properties of soil influence their spectral electrical response (SER). Laboratory measurements of the spectral electrical response of over 30 soil samples taken from different sites across North Carolina were performed within the frequency range from 0.01 Hz to 10 kHz. The hydraulic conductivity, porosity, and moisture content of each soil sample were measured. Both the moisture content and the degree of compaction were controlled for each soil sample to simulate field conditions. The SER measurements are used to estimate the hydraulic conductivity and porosity of soils. The SER of a soil is modeled as a heterogeneous multiphase system using an equivalent circuit model. The intrinsic parameters, which describe the response of the model, are retrieved by an inversion scheme and are used in empirical regression models to predict the hydraulic conductivity and porosity. Multiple regression analyses suggest that the porosity and permeability can be well predicted by the parameters of the equivalent circuit model. Such direct relationships between parameters characterizing the spectral electrical response of soils and their hydraulic properties may provide versatile non-invasive methodology of obtaining hydraulic conductivity and porosity of soils using geophysical measurements.

Boadu, F. K.

2002-05-01

201

Impact of organic material incorporation with soil in relation to their shear strength and water properties  

Microsoft Academic Search

A b s t r a c t. A laboratory experiment was conducted to determine the quantitative effects of incorporating groundnut haulms, cow dung and chicken dung on hydraulic properties of compacted sandy loam, clay loam and clay soils. The consistency limits, shear strength, water retention and hydraulic conductivity of the three soil textures were measured. Groundnut haulms, cow dung

J. O. Ohu; E. Mamman; A. A. Mustapha

202

Prediction of spatially variable unsaturated hydraulic conductivity using scaled particle-size distribution functions  

E-print Network

] Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an effective means soil water content and saturated hydraulic conductivity. Our results demonstrate that the presented properties, namely the water retention function (WRF) and the unsaturated hydraulic conductivity function

Vrugt, Jasper A.

203

Vadose-zone monitoring strategy to evaluate desalted groundwater effects on hydraulic properties  

NASA Astrophysics Data System (ADS)

Desalinated brackish groundwater is becoming a new source of water supply to comply with growing water demands, especially in (semi) arid countries. Irrigation with desalinated or a blend of desalinated and ground/surface water, presents associated impacts on plants, soil and aquifer media. Mixed waters with different salinities can lead to the formation of unexpected chemical precipitates. The use of desalted groundwater for irrigation counts with potential drawbacks, among them: changes of hydraulic properties of soil-aquifer systems (e.g. hydraulic conductivity, porosity) as a consequence of mineral precipitation; root growth blockage and plant uptake of pollutants; as well as leaching of contaminants to groundwater. An experimental plot located at SE Spain, covered by grass and irrigated by sprinklers with a blend of desalted and groundwater from a brackish aquifer, has been monitored in order to characterize at field scale the possible impacts on soil hydraulic properties. The monitoring strategy to control water and heat flux includes traditional and more updated devices. The field instrumentation, vertically installed from the ground surface and spatially distributed, consisted of: ten tensiometers (Soilmoisture Equipment Corp, Goleta, CA, USA) at different depths (two per depth); and, two access tubes (fiber glass, 44mm diameter 2m length) for soil moisture measurements from TRIME-FM TDR probe (Imko GmbH, Ettlingen, Germany). Automatic logging is carried out from a trench located in the border of the experimental plot and it takes in: a set of five 5TE devices (Decagon Devices Inc, Pullman, WA, USA) vertically installed, which measure volumetric water content, electric conductivity and temperature; and additionally, a suction sensor at 0.6m depth. Finally, a periodic sampling of undisturbed soil cores (2m length) takes place for the purpose of imaging porosity changes from environmental scanning electron microscope (ESEM). First results about water and heat flux, as well as changes in the soil hydraulic properties, are presented in the current work.

Valdes-Abellan, J.; Candela, L.; Jiménez-Martínez, J.

2012-04-01

204

Hydraulic characterization of aquifers, reservoir rocks, and soils: A history of ideas  

NASA Astrophysics Data System (ADS)

Estimation of the hydraulic properties of aquifers, petroleum reservoir rocks, and soil systems is a fundamental task in many branches of Earth sciences and engineering. The transient diffusion equation proposed by Fourier early in the 19th century for heat conduction in solids constitutes the basis for inverting hydraulic test data collected in the field to estimate the two basic parameters of interest, namely, hydraulic conductivity and hydraulic capacitance. Combining developments in fluid mechanics, heat conduction, and potential theory, the civil engineers of the 19th century, such as Darcy, Dupuit, and Forchheimer, solved many useful problems of steady state seepage of water. Interest soon shifted towards the understanding of the transient flow process. The turn of the century saw Buckingham establish the role of capillary potential in governing moisture movement in partially water-saturated soils. The 1920s saw remarkable developments in several branches of the Earth sciences; Terzaghi's analysis of deformation of water-saturated earth materials, the invention of the tensiometer by Willard Gardner, Meinzer's work on the compressibility of elastic aquifers, and the study of the mechanics of oil and gas reservoirs by Muskat and others. In the 1930s these led to a systematic analysis of pressure transients from aquifers and petroleum reservoirs through the work of Theis and Hurst. The response of a subsurface flow system to a hydraulic perturbation is governed by its geometric attributes as well as its material properties. In inverting field data to estimate hydraulic parameters, one makes the fundamental assumption that the flow geometry is known a priori. This approach has generally served us well in matters relating to resource development primarily concerned with forecasting fluid pressure declines. Over the past two decades, Earth scientists have become increasingly concerned with environmental contamination problems. The resolution of these problems requires that hydraulic characterization be carried out at a much finer spatial scale, for which adequate information on geometric detail is not forthcoming. Traditional methods of interpretation of field data have relied heavily on analytic solutions to specific, highly idealized initial-value problems. The availability of efficient numerical models and versatile spreadsheets of personal computers offer promising opportunities to relax many unavoidable assumptions of analytical solutions and interpret field data much more generally and with fewer assumptions. Currently, a lot of interest is being devoted to the characterization of permeability. However, all groundwater systems are transient on appropriate timescales. The dynamics of groundwater systems cannot be understood without paying attention to capacitance. Much valuable insights about the dynamic attributes of groundwater systems could be gained by long-term passive monitoring of responses of groundwater systems to barometric changes, Earth tides, and ocean tides.

Narasimhan, T. N.

205

Saturated hydraulic conductivity of soils in the Horqin Sand Land of Inner Mongolia, northern China.  

PubMed

Water is a limiting factor to plant growth in Horqin Sand Land of China. Knowledge of soil saturated hydraulic conductivity (K(sat)) is of importance because K(sat) influences soil evaporation and water cycling at various scales. In order to analyze the variation of K(sat) along with sand types and soil depths, and its relationship with soil physiochemical properties, six typical lands were chosen, including mobile dune, fixed dune, pine woodland, poplar woodland, grassland, and cropland, and K(sat) was measured in situ by Guelph Permeameter at each type of land. Soil bulk density, organic matter content, and soil particle size distribution were determined in parallel with K(sat) measurement. The results showed that (1) The averaged K(sat) was decreased in the order: mobile dune > fixed dune > pine woodland > poplar woodland > grassland > cropland; changes in K(sat) varied considerably as soil depth increased, e.g., the changes of K(sat) along with soil depth in fixed dune was fitted by exponential model, but it was fitted by parabola model in the pine woodland and grassland. (2) The K(sat) values of fixed dune and mobile dune were varied considerably among three slope positions (dune top, windward slope, and leeward slope). (3) The relationships of K(sat) and soil physiochemical property revealed that soil bulk density, organic matter content, and coarse sand fraction (2?0.1 mm) were the key factors affecting K(sat) in Horqin Sand Land. Compared with clay and silt content proportion, sand fraction in this region showed a more significant positive correlation with K(sat). PMID:23179727

Yao, Shuxia; Zhang, Tonghui; Zhao, Chuancheng; Liu, Xinping

2013-07-01

206

Development of Property-Transfer Models for Estimating the Hydraulic Properties of Deep  

E-print Network

Development of Property-Transfer Models for Estimating the Hydraulic Properties of Deep Sediments. #12;Development of Property-Transfer Models for Estimating the Hydraulic Properties of Deep Sediments-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication

207

Hydraulics.  

ERIC Educational Resources Information Center

This curriculum guide contains a course in hydraulics to train entry-level workers for automotive mechanics and other fields that utilize hydraulics. The module contains 14 instructional units that cover the following topics: (1) introduction to hydraulics; (2) fundamentals of hydraulics; (3) reservoirs; (4) lines, fittings, and couplers; (5)…

Decker, Robert L.; Kirby, Klane

208

Soil properties controlling infiltration in volcanic soils  

NASA Astrophysics Data System (ADS)

Soil water infiltration is an important process whose behaviour depends on external factors and soil properties that vary depending on the type of soil. The soil parameters affecting the infiltration capacity of six soil orders all formed on volcanic materials (andisols, vertisols, alfisols, aridisols, inceptisols, and entisols) and contribute to the differences between them were studied in this paper. A total of 108 sites were selected on the island of Tenerife (Spain). The main soil properties were analysed and the steady-state infiltration rate measured using a double-ring infiltrometer. The relationship between the soil properties and infiltration was modelled using statistical Principal Components Analysis and regressions. The research concludes that the relation between structural development and texture play a decisive role. The high structural development of non-vitric andisols, due to the high organic matter and short-range-order mineral content, leads to an extremely fast infiltration rate. The structural instability and fine texture of aridisols produce low infiltration. In less developed soils (entisols and vitric andisols) where aggregate formation is minimal or non-existent, the coarse grain size is the relevant factor determining their very fast and extremely fast infiltration. In vertisols and alfisols, which have strong aggregation but low stability, clay type and content play an important role and lead to a moderate and moderately fast steady-state infiltration rate, respectively. In the most typic inceptisols, with moderate structural development and stability, the balance of the properties is largely responsible for the intermediate infiltration rate observed.

Neris, Jonay; Tejedor, Marisa; Jiménez, Concepción

2013-04-01

209

Root-induced hydraulic changes of soil matrix - an in-situ experimental study in the wetland of Poyang Lake  

NASA Astrophysics Data System (ADS)

Plant roots may change the structure of the surface soil layer and hence the groundwater flow in wetlands. Such modifications would affect the soil condition, which in turn may influence the growth of the plants and the structure of the natural vegetation community. In order to determine the relationship between the distribution of the roots and the hydraulic property of the soil matrix, we conducted a series of in-situ experiments based on falling head test at a field site in the wetland of Poyang Lake. Areas dominated by three typical plants in the wetland, Artemisia selengensis, Phalaris arundinacea and Carex tristachya, were examined. Comparisons were also made between areas with and without plants covered. The results show that the roots improved the flow conditions of soil matrix, especially for Carex tristachya, which had a great plant and root density. The volume fraction of the roots and the grain composition of the soil were also analyzed. The regression analyses show that the root density played an important role in affecting the saturated hydraulic conductivity near the surface where the soil matrix has a larger root volume fraction. Deep into soil (after 15cm from the surface), the root volume fraction decreased and the influence of the grain composition on changes of the saturated hydraulic conductivity became more significant. These results may improve the understandings of the relationship between hydrological conditions and the growth of vegetation in the wetland.

Zhao, Z.; Jin, G.; Hua, G.; Chen, B.; Tao, X.; Li, L.

2013-12-01

210

Hydraulic conductivity study of compacted clay soils used as landfill liners for an acidic waste.  

PubMed

Three natural clayey soils from Tunisia were studied to assess their suitability for use as a liner for an acid waste disposal site. An investigation of the effect of the mineral composition and mechanical compaction on the hydraulic conductivity and fluoride and phosphate removal of three different soils is presented. The hydraulic conductivity of these three natural soils are 8.5 × 10(-10), 2.08 × 10(-9) and 6.8 × 10(-10)m/s for soil-1, soil-2 and soil-3, respectively. Soil specimens were compacted under various compaction strains in order to obtain three wet densities (1850, 1950 and 2050 kg/m(3)). In this condition, the hydraulic conductivity (k) was reduced with increasing density of sample for all soils. The test results of hydraulic conductivity at long-term (>200 days) using acidic waste solution (pH=2.7, charged with fluoride and phosphate ions) shows a decrease in k with time only for natural soil-1 and soil-2. However, the specimens of soil-2 compressed to the two highest densities (1950 and 2050 kg/m(3)) are cracked after 60 and 20 days, respectively, of hydraulic conductivity testing. This damage is the result of a continued increase in the internal stress due to the swelling and to the effect of aggressive wastewater. The analysis of anions shows that the retention of fluoride is higher compared to phosphate and soil-1 has the highest sorption capacity. PMID:22980909

Hamdi, Noureddine; Srasra, Ezzeddine

2013-01-01

211

Plant hydraulic lift of soil water – implications for crop production and land restoration  

Microsoft Academic Search

Water more than other factors limits growth and productivity of terrestrial plants. Strategies of plants to cope with soil\\u000a drought include hydraulic redistribution of water via roots from moist to dry soil. During periods of drought, water may be\\u000a transported upward through root systems from moister subsurface to dry surface soil by a process known as “hydraulic lift”\\u000a (HL). On

Hans-Holger Liste; Jason C. White

2008-01-01

212

Hydraulic and thermal soil Parameter combined with TEM data at quaternary coastal regions  

NASA Astrophysics Data System (ADS)

In order to generate a more efficient method of planning and dimensioning small- and medium sized geothermal power plants at quaternary subsurface a basic approach has been attempted. Within the EU-project CLIWAT, the coastal region of Denmark, Germany, Netherlands and Belgium has been investigated and air borne electro magnetic data was collected. In this work the regional focus was put on the isle of Föhr. To describe the subsurface with relevant parameters one need the information from drillings and geophysical well logging data. The approach to minimize costs and use existing data from state agencies led the investigation to the combination of specific electrical resistivity data and hydraulic and thermal conductivity. We worked out a basic soil/hydraulic conductivity statistic for the isle of Föhr by gathering all well logging data from the island and sorted the existing soil materials to associated kf -values. We combined specific electrical resistivity with hydraulic soil properties to generate thermal conductivity values by extracting porosity. Until now we generated a set of rough data for kf - values and thermal conductivity. The air borne TEM data sets are reliable up to 150 m below surface, depending on the conductivity of the layers. So we can suppose the same for the differentiated parameters. Since this is a very rough statistic of kf -values, further more investigation has to be made. Although the close connection to each area of investigation either over existing logging data or laboratory soil property values will remain necessary. Literature: Ahmed S, de Marsily G, Talbot A (1988): Combined Use of Hydraulic and Electrical Properties of an Aquifer in a Geostatistical Estimation of Transmissivity. - Groundwater, vol. 26 (1) Burschil T, Scheer W, Wiederhold H, Kirsch R (2012): Groundwater situation on a glacially affected barrier island. Submitted to Hydrology and Earth System Sciences - an Interactive Open Access Journal of the European Geosciences Union Burval Working Group (2006) Groundwater Resources in buried valleys- a challenge for Geosciences. - Leibniz-Institut für Angewandte Geophysik, Hannover Scheer W, König B, Steinmann F (2012): Die Grundwasserverhältnisse von Föhr. - In: Der Untergrund von Föhr: Geologie, Grundwasser und Erdwärme - Ergebnisse des INTERREG-Projektes CLIWAT. - Landesamt für Landwirtschaft, Umwelt und ländliche Räume Schleswig-Holstein, Flintbek

Grabowski, Ima; Kirsch, Reinhard; Scheer, Wolfgang

2014-05-01

213

Effects of model layer simplification using composite hydraulic properties  

USGS Publications Warehouse

The effects of simplifying hydraulic property layering within an unconfined aquifer and the underlying confining unit were assessed. The hydraulic properties of lithologic units within the unconfined aquifer and confining unit were computed by analyzing the aquifer-test data using radial, axisymmetric two-dimensional (2D) flow. Time-varying recharge to the unconfined aquifer and pumping from the confined Upper Floridan aquifer (USA) were simulated using 3D flow. Conceptual flow models were developed by gradually reducing the number of lithologic units in the unconfined aquifer and confining unit by calculating composite hydraulic properties for the simplified lithologic units. Composite hydraulic properties were calculated using either thickness-weighted averages or inverse modeling using regression-based parameter estimation. No significant residuals were simulated when all lithologic units comprising the unconfined aquifer were simulated as one layer. The largest residuals occurred when the unconfined aquifer and confining unit were aggregated into a single layer (quasi-3D), with residuals over 100% for the leakage rates to the confined aquifer and the heads in the confining unit. Residuals increased with contrasts in vertical hydraulic conductivity between the unconfined aquifer and confining unit. Residuals increased when the constant-head boundary at the bottom of the Upper Floridan aquifer was replaced with a no-flow boundary.

Sepulveda, Nicasio; Kuniansky, Eve L.

2010-01-01

214

Soil hydraulic manipulation and organic amendment for the enhancement of selenium volatilization in a soil–pickleweed system  

Microsoft Academic Search

Biological volatilization of selenium (Se) in contaminated areas represents an environmentally friendly phytoremediation approach. Implementation of phytovolatilization technology for the remediation of Se-contaminated soils or sediments is oftentimes limited by its low remediation efficiency under field conditions. This greenhouse study determined the feasibility of manipulating soil organic content and hydraulic conditions in a soil–pickleweed (Salicornia bigelovii) system for the enhancement

B. Shrestha; S. Lipe; K. A. Johnson; T. Q. Zhang; W. Retzlaff; Z.-Q. Lin

2006-01-01

215

Comparison of Laboratory and Field Methods for Determining the Quasi-Saturated Hydraulic Conductivity of Soils  

SciTech Connect

Laboratory and field ponded infiltration tests in quasi-saturated soils (containing entrapped air) exhibit the same three-stage temporal variability for the flow rate and hydraulic conductivity. However, the values for the hydraulic conductivity may differ by as much as two orders of magnitude due to differences in the geometry and physics of flow when different laboratory and field methods are applied. The purpose of this paper is to investigate this variability using a comparison of results of ponded infiltration tests conducted under laboratory conditions using confined cores, with results of field tests conducted using partially isolated cores and double-ring infiltrometers. Under laboratory conditions in confined cores, during the firs stage, the water flux decreases over time because entrapped air plugs the largest pores in the soils; during the second stage, the quasi-saturated hydraulic conductivity increases by one to two orders of magnitude, essentially reaching the saturated hydraulic conductivity, when entrapped air is discharged from the soils; during the third stage, the hydraulic conductivity decreases to minimum values due to sealing of the soil surface and the effect of biofilms sealing the pores within the wetted zone. Under field conditions, the second stage is only partially developed, and when the surface sealing process begins, the hydraulic pressure drops below the air entry value, thereby causing atmospheric air to enter the soils. As a result, the soils become unsaturated with a low hydraulic conductivity, and the infiltration rate consequently decreases. Contrary to the laboratory experiments in confined cores, the saturated hydraulic conductivity cannot be reached under field conditions. In computations of infiltration one has to take into account the variations in the quasi-saturated and unsaturated hydraulic conductivities, moisture and entrapped air content, and the hydraulic gradient in the quasi-saturated or unsaturated soils.

Faybishenko, Boris

1997-08-01

216

High-quality unsaturated zone hydraulic property data for hydrologic applications  

E-print Network

High-quality unsaturated zone hydraulic property data for hydrologic applications Kim Perkins1, calculations based on property transfer models informed by hydraulic property databases are often used in lieu in this way and for theoretical and property transfer model development and testing. Hydraulic properties

217

Hydraulics.  

ERIC Educational Resources Information Center

These instructional materials provide an orientation to hydraulics for use at the postsecondary level. The first of 12 sections presents an introduction to hydraulics, including discussion of principles of liquids, definitions, liquid flow, the two types of hydraulic fluids, pressure gauges, and strainers and filters. The second section identifies…

Engelbrecht, Nancy; And Others

218

HYDRAULIC REDISTRIBUTION OF SOIL WATER: ECOSYSTEM IMPLICATIONS FOR PACIFIC NORTHWEST FORESTS  

EPA Science Inventory

The physical process of hydraulic redistribution (HR) is driven by competing soil, tree and atmospheric water potential gradients, and may delay severe water stress for roots and other biota associated with the upper soil profile. We monitored soil moisture characteristics across...

219

Soil Water Sensor Needs for the Evaluation of Hydraulic Lift in Crop Plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydraulic lift (HL) in plants is defined as the process by which water is redistributed from wet soil zones to drier soil zones through the plant root system in response to gradients in water potential. Water is released into the dry soil when plant transpiration is low (night) and reabsorbed by th...

220

CONVERGING PATTERNS OF UPTAKE AND HYDRAULIC REDISTRIBUTION OF SOIL WATER IN CONTRASTING WOODY VEGETATION TYPES  

EPA Science Inventory

We used concurrent measurements of soil water content and soil water potential (Ysoil) to assess the effects of Ysoil on uptake and hydraulic redistribution (HR) of soil water by roots during seasonal drought cycles in six sites characterized by different types and amounts of woo...

221

HYDRAULIC REDISTRIBUTION OF SOIL WATER DURING SUMMER DROUGHT IN TWO CONTRASTING PACIFIC NORTHWEST CONIFEROUS FORESTS  

EPA Science Inventory

The magnitude of hydraulic redistribution of soil water by roots and its impact on soil water balance were estimated by monitoring time courses of soil water status at multiple depths and root sap flow during droughted conditions in a dry ponderosa pine ecosystem and a moist Doug...

222

ReproducedfromVadoseZoneJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Correspondence and Upscaling of Hydraulic Functions for Steady-State Flow  

E-print Network

VadoseZoneJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Correspondence and Upscaling of Hydraulic Functions for Steady-State Flow in Heterogeneous Soils Jianting Zhu of hydraulic functions to correspond (i.e., to give similar or identical results for a given flowSoil hydraulic investigated two major issues involving soil hydraulic proper- parameters based on the shapes of retention

Mohanty, Binayak P.

223

Hydraulic properties and leachate level analysis of Kimpo metropolitan landfill, Korea.  

PubMed

Hydraulic properties of waste and cover soil from Kimpo Metropolitan Landfill were experimentally measured by laboratory tests. The degree of compaction was changed to identify the effect on hydraulic conductivity, field capacity, and permanent wilting point. Properties were utilized in developing a reliable numerical tool for leachate analysis. HELP, a simulation model for hydrologic evaluation of landfill performance, was adopted for that purpose. For calibration, results from simulation using the parameter values measured by laboratory tests were compared against the field data. The model was applied to predict the leachate level change according to the degree of compaction and cover soil thickness variation. It was found that the increase in the degree of compaction for intermediate cover soil and waste results in the decrease of field capacity and hydraulic conductivity, hence, the increase of leachate level. The effect of cover layer thickness on the leachate level was minor. Based on the findings from laboratory and numerical experiments, a guideline for reclamation practice was recommended. PMID:11952173

Jang, Y S; Kim, Y W; Lee, S I

2002-01-01

224

Uncertainty in the determination of soil hydraulic parameters and its influence on the performance of two hydrological models of different complexity  

NASA Astrophysics Data System (ADS)

Data of soil hydraulic properties forms often a limiting factor in unsaturated zone modelling, especially at the larger scales. Investigations for the hydraulic characterization of soils are time-consuming and costly, and the accuracy of the results obtained by the different methodologies is still debated. However, we may wonder how the uncertainty in soil hydraulic parameters relates to the uncertainty of the selected modelling approach. We performed an intensive monitoring study during the cropping season of a 10 ha maize field in Northern Italy. These data were used to: i) compare different methods for determining soil hydraulic parameters and ii) evaluate the effect of the uncertainty in these parameters on different outputs (i.e. evapotranspiration, water content in the root zone, fluxes through the bottom boundary of the root zone) of two hydrological models with different complexity: SWAP, a widely used model of soil moisture dynamics in unsaturated soils based on Richards equation, and ALHyMUS, a conceptual model of the same dynamics based on a reservoir cascade scheme. We employed five direct and indirect methods to determine soil hydraulic parameters for each horizon of the experimental field. Two methods were based on a parameter optimization of: a) laboratory measured retention and hydraulic conductivity data and b) field measured retention and hydraulic conductivity data. Three methods were based on the application of widely used Pedo-Transfer Functions: c) Rawls and Brakensiek; d) HYPRES; and e) ROSETTA. Simulations were performed using meteorological, irrigation and crop data measured at the experimental site during the period June-October 2006. Results showed a wide range of soil hydraulic parameter values evaluated with the different methods, especially for the saturated hydraulic conductivity Ksat and the shape parameter ? of the Van Genuchten curve. This is reflected in a variability of the modeling results which is, as expected, different for each model. The variability of the simulated water content in the root zone and of the fluxes at the root zone bottom for different soil hydraulic parameter sets is found to be often larger than the difference between modeling results of the two models using the same soil hydraulic parameter set. Also we found that a good agreement in simulated soil moisture patterns may occur even if evapotranspiration and percolation fluxes are significantly different. Therefore multiple output variables should be considered to test the performances of methods and models.

Baroni, G.; Facchi, A.; Gandolfi, C.; Ortuani, B.; Horeschi, D.; van Dam, J. C.

2009-06-01

225

Uncertainty in the determination of soil hydraulic parameters and its influence on the performance of two hydrological models of different complexity  

NASA Astrophysics Data System (ADS)

Data of soil hydraulic properties forms often a limiting factor in unsaturated zone modelling, especially at the larger scales. Investigations for the hydraulic characterization of soils are time-consuming and costly, and the accuracy of the results obtained by the different methodologies is still debated. However, we may wonder how the uncertainty in soil hydraulic parameters relates to the uncertainty of the selected modelling approach. We performed an intensive monitoring study during the cropping season of a 10 ha maize field in Northern Italy. The data were used to: i) compare different methods for determining soil hydraulic parameters and ii) evaluate the effect of the uncertainty in these parameters on different variables (i.e. evapotranspiration, average water content in the root zone, flux at the bottom boundary of the root zone) simulated by two hydrological models of different complexity: SWAP, a widely used model of soil moisture dynamics in unsaturated soils based on Richards equation, and ALHyMUS, a conceptual model of the same dynamics based on a reservoir cascade scheme. We employed five direct and indirect methods to determine soil hydraulic parameters for each horizon of the experimental profile. Two methods were based on a parameter optimization of: a) laboratory measured retention and hydraulic conductivity data and b) field measured retention and hydraulic conductivity data. The remaining three methods were based on the application of widely used Pedo-Transfer Functions: c) Rawls and Brakensiek, d) HYPRES, and e) ROSETTA. Simulations were performed using meteorological, irrigation and crop data measured at the experimental site during the period June - October 2006. Results showed a wide range of soil hydraulic parameter values generated with the different methods, especially for the saturated hydraulic conductivity Ksat and the shape parameter ? of the van Genuchten curve. This is reflected in a variability of the modeling results which is, as expected, different for each model and each variable analysed. The variability of the simulated water content in the root zone and of the bottom flux for different soil hydraulic parameter sets is found to be often larger than the difference between modeling results of the two models using the same soil hydraulic parameter set. Also we found that a good agreement in simulated soil moisture patterns may occur even if evapotranspiration and percolation fluxes are significantly different. Therefore multiple output variables should be considered to test the performances of methods and models.

Baroni, G.; Facchi, A.; Gandolfi, C.; Ortuani, B.; Horeschi, D.; van Dam, J. C.

2010-02-01

226

Flow Rate Dependence of Soil Hydraulic Characteristics D. Wildenschild,* J. W. Hopmans, J. Simunek  

E-print Network

Flow Rate Dependence of Soil Hydraulic Characteristics D. Wildenschild,* J. W. Hopmans, J. Simunek ABSTRACT referred to a study by Harris and Morrow (1964), who studied pendular rings in packs of relatively

Wildenschild, Dorthe

227

Soil Properties That Distinguish Ecological Sites  

E-print Network

that determines soil water amounts. Soil properties are features of a soil: · e.g. soil texture, depth #12Soil Properties That Distinguish Ecological Sites Mike Duniway USGS-Southwest Biological Science Properties · Within a climatic zone (e.g. MLRA), differentiation of ecological sites based on soil

228

Coevolution of hydraulic, soil and vegetation processes in estuarine wetlands  

NASA Astrophysics Data System (ADS)

Estuarine wetlands of south eastern Australia, typically display a vegetation zonation with a sequence mudflats - mangrove forest - saltmarsh plains from the seaward margin and up the topographic gradient. Estuarine wetlands are among the most productive ecosystems in the world, providing unique habitats for fish and many terrestrial species. They also have a carbon sequestration capacity that surpasess terrestrial forest. Estuarine wetlands respond to sea-level rise by vertical accretion and horizontal landward migration, in order to maintain their position in the tidal frame. In situations in which buffer areas for landward migration are not available, saltmarsh can be lost due to mangrove encroachment. As a result of mangrove invasion associated in part with raising estuary water levels and urbanisation, coastal saltmarsh in parts of south-eastern Australia has been declared an endangered ecological community. Predicting estuarine wetlands response to sea-level rise requires modelling the coevolving dynamics of water flow, soil and vegetation. This paper presents preliminary results of our recently developed numerical model for wetland dynamics in wetlands of the Hunter estuary of NSW. The model simulates continuous tidal inflow into the wetland, and accounts for the effect of varying vegetation types on flow resistance. Coevolution effects appear as vegetation types are updated based on their preference to prevailing hydrodynamic conditions. The model also considers that accretion values vary with vegetation type. Simulations are driven using local information collected over several years, which includes estuary water levels, accretion rates, soil carbon content, flow resistance and vegetation preference to hydraulic conditions. Model results predict further saltmarsh loss under current conditions of moderate increase of estuary water levels.

Trivisonno, Franco; Rodriguez, Jose F.; Riccardi, Gerardo; Saco, Patricia; Stenta, Hernan

2014-05-01

229

Soil hydraulic response to land-use change associated with the recent soybean expansion at the Amazon agricultural frontier  

Microsoft Academic Search

Clearing for large-scale soy production and the displacement of cattle-breeding by soybeans are major features of land-use change in the lowland Amazon that can alter hydrologic properties of soils and the runoff generation over large areas. We measured infiltrability and saturated hydraulic conductivity (Ksat) under natural forest, pasture, and soybeans on Oxisols in a region of rapid soybean expansion in

Raphael Scheffler; Christopher Neill; Alex V. Krusche; Helmut Elsenbeer

2011-01-01

230

HYDRAULIC AND PHYSICAL PROPERTIES OF SALTSTONE GROUTS AND VAULT CONCRETES  

SciTech Connect

The Saltstone Disposal Facility (SDF), located in the Z-Area of the Savannah River Site (SRS), is used for the disposal of low-level radioactive salt solution. The SDF currently contains two vaults: Vault 1 (6 cells) and Vault 4 (12 cells). Additional disposal cells are currently in the design phase. The individual cells of the saltstone facility are filled with saltstone. Saltstone is produced by mixing the low-level radioactive salt solution, with blast furnace slag, fly ash, and cement (dry premix) to form a dense, micro-porous, monolithic, low-level radioactive waste form. The saltstone is pumped into the disposal cells where it subsequently solidifies. Significant effort has been undertaken to accurately model the movement of water and contaminants through the facility. Key to this effort is an accurate understanding of the hydraulic and physical properties of the solidified saltstone. To date, limited testing has been conducted to characterize the saltstone. The primary focus of this task was to estimate the hydraulic and physical properties of three types of saltstone and two vault concretes. The saltstone formulations included saltstone premix batched with (1) Deliquification, Dissolution, and Adjustment (DDA) salt simulant (w/pm 0.60), (2) Actinide Removal Process (ARP)/Modular Caustic Side Solvent Extraction Unit (MCU) salt simulant (w/pm 0.60), and (3) Salt Waste Processing Facility (SWPF) salt simulant (w/pm 0.60). The vault concrete formulations tested included the Vault 1/4 concrete and two variations of the Vault 2 concrete (Mix 1 and Mix 2). Wet properties measured for the saltstone formulations included yield stress, plastic viscosity, wet unit weight, bleed water volume, gel time, set time, and heat of hydration. Hydraulic and physical properties measured on the cured saltstone and concrete samples included saturated hydraulic conductivity, moisture retention, compressive strength, porosity, particle density, and dry bulk density. These properties were determined following a minimum 28 day curing period. Additional testing of the three saltstone formulations was conducted following a minimum 90 day curing period. The compressive strength of each saltstone and concrete material was measured at approximately 14, 28, 56, and 90 days. Recommended hydraulic property values for each saltstone grout and the vault concretes are provided. The hydraulic properties provided for each material include the saturated hydraulic conductivity, dry bulk density, particle density, and porosity. In addition, water retention data are presented for each material along with the van Genuchten transport parameters as determined using the RETC code.

Dixon, K; John Harbour, J; Mark Phifer, M

2008-11-25

231

Characterizing Hydraulic Properties and Ground-Water Chemistry in Fractured-Rock Aquifers: A User's Manual  

E-print Network

Characterizing Hydraulic Properties and Ground-Water Chemistry in Fractured-Rock Aquifers: A User., 2007, Characterizing hydraulic properties and ground-water chemistry in fractured-rock aquifers: A user

232

Plasticity of rhizosphere hydraulic properties as a key for efficient utilization of scarce resources  

PubMed Central

Background It is known that the soil near roots, the so-called rhizosphere, has physical and chemical properties different from those of the bulk soil. Rhizosphere properties are the result of several processes: root and soil shrinking/swelling during drying/wetting cycles, soil compaction by root growth, mucilage exuded by root caps, interaction of mucilage with soil particles, mucilage shrinking/swelling and mucilage biodegradation. These processes may lead to variable rhizosphere properties, i.e. the presence of air-filled gaps between soil and roots; water repellence in the rhizosphere caused by drying of mucilage around the soil particles; or water accumulation in the rhizosphere due to the high water-holding capacity of mucilage. The resulting properties are not constant in time but they change as a function of soil condition, root growth rate and mucilage age. Scope We consider such a variability as an expression of rhizosphere plasticity, which may be a strategy for plants to control which part of the root system will have a facilitated access to water and which roots will be disconnected from the soil, for instance by air-filled gaps or by rhizosphere hydrophobicity. To describe such a dualism, we suggest classifying rhizosphere into two categories: class A refers to a rhizosphere covered with hydrated mucilage that optimally connects roots to soil and facilitates water uptake from dry soils. Class B refers to the case of air-filled gaps and/or hydrophobic rhizosphere, which isolate roots from the soil and may limit water uptake from the soil as well water loss to the soil. The main function of roots covered by class B will be long-distance transport of water. Outlook This concept has implications for soil and plant water relations at the plant scale. Root water uptake in dry conditions is expected to shift to regions covered with rhizosphere class A. On the other hand, hydraulic lift may be limited in regions covered with rhizosphere class B. New experimental methods need to be developed and applied to different plant species and soil types, in order to understand whether such dualism in rhizosphere properties is an important mechanism for efficient utilization of scarce resources and drought tolerance. PMID:23235697

Carminati, Andrea; Vetterlein, Doris

2013-01-01

233

Effect of urban waste compost application on soil near-saturated hydraulic conductivity.  

PubMed

Compost application tends to increase soil fertility and is likely to modify soil hydrodynamic properties by acting on soil structural porosity. Two composts, a municipal solid waste compost (MSW) and a co-compost of green wastes and sewage sludge (SGW), have been applied every other year for 6 yr to cultivated plots located on a silt loam soil in the Parisian Basin, France. Four soil zones were defined in the topsoil after plowing: the plowpan located at the base of the plowed layer, compacted (Delta) or noncompacted (Gamma) zones located within the plowed layer, and interfurrows created by plowing and containing a large quantity of crop residues together with the recently-applied compost. To assess the effect of compost application on the near-saturated soil hydraulic conductivity, infiltration rates were measured using a tension disc infiltrometer at three water pressure potentials -0.6, -0.2, and -0.05 kPa in the various zones of the soil profile. Compost addition decreased K((sat)) in the interfurrows after plowing by almost one order of magnitude with average values of 5.6 x 10(-5) m.s(-1) in the MSW plot and 4.1 x 10(-5) m.s(-1) in the SGW plot, against 2.2 x 10(-4) m.s(-1) in the control plot. This effect had disappeared 6 mo after plowing when the average K((sat)) in the control plot had decreased to 1.9 x 10(-5) m.s(-1) while that in the compost-amended plots remained stable. PMID:19244499

Schneider, S; Coquet, Y; Vachier, P; Labat, C; Roger-Estrade, J; Benoit, P; Pot, V; Houot, S

2009-01-01

234

Considerations for modeling bacterial-induced changes in hydraulic properties of variably saturated porous media  

NASA Astrophysics Data System (ADS)

Bacterial-induced changes in the hydraulic properties of porous media are important in a variety of disciplines. Most of the previous research on this topic has focused on liquid-saturated porous media systems that are representative of aquifer sediments. Unsaturated or variably saturated systems such as soils require additional considerations that have not been fully addressed in the literature. This paper reviews some of the earlier studies on bacterial-induced changes in the hydraulic properties of saturated porous media, and discusses characteristics of unsaturated or variably saturated porous media that may be important to consider when modeling such phenomena in these systems. New data are presented from experiments conducted in sand-packed columns with initially steady unsaturated flow conditions that show significant biomass-induced changes in pressure heads and water contents and permeability reduction during growth of a Pseudomonas fluorescens bacterium.

Rockhold, M. L.; Yarwood, R. R.; Niemet, M. R.; Bottomley, P. J.; Selker, J. S.

235

Considerations for Modeling Bacterial-Induced Changes in Hydraulic Properties of Variably Saturated Porous Media  

SciTech Connect

Bacterial-induced changes in the hydraulic properties of porous media are important in a variety of disciplines. Most of the pervious research on this topic has focused on liquid-saturated porous media systems that are representative of aquifer sediments. Unsaturated or variably saturated systems such as soils require additional considerations that have not been fully addressed in the literature. This paper reviews some of the earlier studies on bacterial-induced changes in the hydraulic properties of saturated porous media, and discusses characteristics of unsaturated or variably saturated porous media that may be important to consider when modeling such phenomena in these systems. New data are presented from experiments conducted in sand-packed columns with initially steady unsaturated flow conditions that show significant biomass-induced changes in pressure heads and water contents and permeability reduction during growth of a Pseudomonas fluorescens bacterium.

Rockhold, Mark L.; Yarwood, R. R.; Niemet, Michael R.; Bottomley, Peter J.; Selker, John S.

2002-07-26

236

F. Froux et al.Hydraulic properties of Mediterranean conifers Original article  

E-print Network

F. Froux et al.Hydraulic properties of Mediterranean conifers Original article Xylem hydraulic (Received 5 November 2001; accepted 11 February 2002) Abstract ­ We studied the xylem hydraulic traits specific hydraulic conductivity was much higher in Cupressus sempervirens and P. nigra than in Cedrus

Paris-Sud XI, Université de

237

Hydraulics.  

ERIC Educational Resources Information Center

Designed for use in courses where students are expected to become proficient in the area of hydraulics, including diesel engine mechanic programs, this curriculum guide is comprised of fourteen units of instruction. Unit titles include (1) Introduction, (2) Fundamentals of Hydraulics, (3) Reservoirs, (4) Lines, Fittings, and Couplers, (5) Seals,…

Decker, Robert L.

238

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture  

E-print Network

Change in the hydraulic properties of a Brazilian clay Ferralsol on clearing for pasture L. C 80 to 300 m in size. The aim of this study was to analyze how the hydraulic properties of a clay retention properties were determined by using pressure cell equipment. We determined the saturated hydraulic

Boyer, Edmond

239

Tillage effects on physical properties in two soils of the Northern Great Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage practices profoundly affect soil physical and hydraulic properties. It is essential to select a tillage practice that sustains the soil physical properties required for successful growth of agricultural crops. We evaluated the effects of conventional (CT) and strip (ST) tillage practices on ...

240

Systemic ozone effects on root hydraulic properties in pima cotton  

SciTech Connect

Ambient ozone concentrations have become problematic even in rural, agricultural areas such as the San Joaquin Valley of California. Pima cotton (cv. S6) has been shown to be relatively sensitive to ozone air pollution, at levels occurring in this production area. In this semi-arid area acquisition of water and nutrients may limit yield and biological productivity. Therefore maximal proliferation, exploration, and efficiency of root systems is desirable. Hydraulic conductance provides a parameter to characterize the efficiency of roots and shoots and their interaction. The authors have used a variety of transpiration and pressure vessel techniques to document ozone-induced reduction of root hydraulic conductance in cotton. They hypothesized that these effects are caused by reduced carbohydrate supply due to reduction of photosynthetic capacity of the shoot associated with direct oxidant damage to foliage. However, the authors simulated this reduced photosynthetic capacity by continuously removing leaf area to match that of ozone treated plants. This resulted in a reduction of whole plant biomass similar to ozone-treated plants, but a root/shoot biomass ratio and root hydraulic properties similar to control plants and contrasting with ozone-treated plants. Thus leaf removal did not simulate effects of ozone on root hydraulic properties. A systematic effect of ozone on whole plant function is indicated, perhaps mediated by direct effects on carbohydrate translocation throughout the plant.

Grantz, D.A.; Yang, S. [Univ. of California, Riverside, CA (United States); [Kearney Agricultural Center, Parlier, CA (United States)

1995-12-31

241

Measurement of soil saturated hydraulic conductivity: The method of constant pressure tubes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Field method to measure the saturated soil hydraulic conductivity is presented that does not require expensive equipment and preserves natural water flow pathways that may be bloked during soil core sampling for laboratory measurements. Vegetation must be removed from the plot prior the measurement...

242

Estimation of Hydraulic Property of an Unconfined Aquifer by GPR  

Microsoft Academic Search

Controlled water productions were performed at a water source area of Ulaanbaatar city, Mongolia to evaluate the effectiveness\\u000a of ground penetrating radar (GPR) for detecting and monitoring dynamic groundwater movements in the subsurface and for estimating\\u000a the hydraulic properties of the aquifer. Field experiments in Ulaanbaatar were carried out in 2001 and 2002. GPR data were\\u000a acquired using 100 MHz antennas.

Qi Lu; Motoyuki Sato

2007-01-01

243

Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality  

NASA Astrophysics Data System (ADS)

SummaryHydrophilic polymers can swell by absorbing huge volumes of water or aqueous solutions. This property has led to many practical applications of these new materials, particularly in arid regions for improving water retention in sandy soils and the water supply to plants grown on them. The effects of two hydrophilic polymers, carboxymethylcellulose (RF) and isopropyl acrylamide (BF) on the water holding capacity and saturated hydraulic conductivity ( KS) of a sandy soil at varying soil temperature and water quality were evaluated. The RF was less efficient in absorbing water than BF, but the efficiency of BF in retaining water was negatively affected by its thermo-sensitivity and the quality of water. The temperature dependence of the water absorption was not clear for the soils treated with RF, whereas, the efficiency of BF treatment in absorbing water decreased significantly ( P < 0.05) with increasing soil temperature. The dependence of the KS on soil temperature differed with the type of hydrophilic polymer used. The KS of the control soil remained nearly constant as the soil temperature increased. The KS of the BF treated soil increased significantly ( P < 0.05) and linearly with increasing soil temperature, while that of soil treated with RF showed a quadratic response. The soil-absorbent mixtures exhibited different water retention characteristics under different soil temperature conditions. The increase in soil temperature did not affect the water retention characteristics curve of the control. The effect of soil temperature on the water potential curve of the soil treated with RF was not clear particularly when the temperature increased from 25 to 35 °C. The water potential curve for soil-BF mixtures showed that the water content value at field capacity shifted from 0.21 to 0.10 cm 3 cm -3 for 0.1% and from 0.27 to 0.12 cm 3 cm -3 for 0.2%, as the soil temperature increased from 15 to 35 °C. This implies that the soil-BF absorbent mixtures would release some moisture as the soil temperature would increase from 15 to 35 °C, and this water could be lost by percolation or taken up by plant. It was found that available water content increased up to four times with RF as compared to control soil whereas it increased up to five times with BF treatment. At high temperature, the difference was much reduced except for RF at 0.2%. This understanding of the characteristics of the absorbents and the interactions among absorbents, soil, and temperature would be of help in water management in sandy soil.

Andry, H.; Yamamoto, T.; Irie, T.; Moritani, S.; Inoue, M.; Fujiyama, H.

2009-06-01

244

Evaluation of pedo-transfer functions for unsaturated soil hydraulic conductivity using an independent data set  

Microsoft Academic Search

The paper reviews eight well-known and accepted pedo-transfer functions used for evaluation of soil hydraulic conductivity (saturated and unsaturated) from routinely available soil data. A comprehensive data set containing detailed measurements of 63 German soil horizons, to which none of the models had been previously calibrated, were used for the evaluation of pedo-transfer functions. The paper considers only pedo-transfer functions

B. Wagner; V. R. Tarnawski; V. Hennings; U. Müller; G. Wessolek; R. Plagge

2001-01-01

245

Impact of land use on the hydraulic properties of the topsoil in a small French catchment  

E-print Network

to median hydraulic conductivity at a pressure of -20 mm of water, was about 50. The study suggestsImpact of land use on the hydraulic properties of the topsoil in a small French catchment E Processes 24, 17 (2010) p. 2382 - p. 2399" DOI : 10.1002/hyp.7640 #12;Abstract The hydraulic properties

Paris-Sud XI, Université de

246

Characterizing hydraulic properties of filter material of a Vertical Flow1 Constructed Wetland2  

E-print Network

Characterizing hydraulic properties of filter material of a Vertical Flow1 Constructed Wetland2 A Characterizing the hydraulic properties of filter material used in a vertical flow11 constructed wetland (VFCW of porous mineral material and13 organic matter that makes hydraulic characterization a difficult task. Here

Paris-Sud XI, Université de

247

Effect of physical property of supporting media and variable hydraulic loading on hydraulic characteristics of advanced onsite wastewater treatment system.  

PubMed

A laboratory-scale study was carried out to investigate the effects of physical properties of the supporting media and variable hydraulic shock loads on the hydraulic characteristics of an advanced onsite wastewater treatment system. The system consisted of two upflow anaerobic reactors (a septic tank and an anaerobic filter) accommodated within a single unit. The study was divided into three phases on the basis of three different supporting media (Aqwise carriers, corrugated ring and baked clay) used in the anaerobic filter. Hydraulic loadings were based on peak flow factor (PFF), varying from one to six, to simulate the actual conditions during onsite wastewater treatment. Hydraulic characteristics of the system were identified on the basis of residence time distribution analyses. The system showed a very good hydraulic efficiency, between 0.86 and 0.93, with the media of highest porosity at the hydraulic loading of PFF???4. At the higher hydraulic loading of PFF?6 also, an appreciable hydraulic efficiency of 0.74 was observed. The system also showed good chemical oxygen demand and total suspended solids removal efficiency of 80.5% and 82.3%, respectively at the higher hydraulic loading of PFF 6. Plug-flow dispersion model was found to be the most appropriate one to describe the mixing pattern of the system, with different supporting media at variable loading, during the tracer study. PMID:25428652

Sharma, Meena Kumari; Kazmi, Absar Ahmad

2015-06-01

248

Impact of Extreme Events and Soil Hydraulic Conductivity on the Evolution of a Mesa-top Waste Repository Cover  

NASA Astrophysics Data System (ADS)

The Siberia model was used to optimize the design of a mesa-top waste repository cover at Los Alamos National Laboratory on the Pajarito Plateau in Northern New Mexico, USA. The cover was designed to meet criteria that the depth to waste from the cover surface would be greater than 1 meter after 1000 years of erosion. The model was run using two steady-state landscape forming events (2 and 5 year return periods) derived from a 20 year data set at the Santa Rita Experimental Watershed in Arizona, and hydraulic properties of two soils, loam and sandy loam. Although we were able to show that the final design cover met the performance criteria for both high and moderate erosion scenarios, concerns remained about the impact of extreme events. In addition, Hydrus simulations, based on saturated hydraulic conductivity (Ksat) measurements from cores of cover material comprised of crushed tuff and a bentonite admixture, suggested that surface runoff on the cover might be orders of magnitude higher than the landscape forming runoff events used for the Siberia simulations. The Siberia runoff events were based on Ksat values for loam and sandy loam soils with identical texture (% sand , silt and clay) to the engineered cover soil, but these values assume soil structure that may or may not develop in the engineered cover. This work summarizes the impacts of both 1) the timing and size of extreme events and 2) the impact of soil structure and Ksat, on long-term repository cover evolution.

Crowell, K. J.; Wilson, C. J.; Lane, L. J.; Newman, B. D.; Schofield, T. G.

2005-12-01

249

Soil physical properties and preferential flow pathways in tropical rain forest, Bukit Tarek, Peninsular Malaysia  

Microsoft Academic Search

Soil physical properties and water movement within soil were investigated using dyes in a tropical rain forest, the Bukit\\u000a Tarek Experimental Watershed of Peninsular Malaysia. The saturated hydraulic conductivity (K\\u000a s) decreased with increasing soil depth. TheK\\u000a s values were higher than those reported for other tropical soils. The geometric means of theK\\u000a s values ranged from 4.6910?3 (80 cm)

Shoji Noguchi; Abdul Rahim Nik; Baharuddin Kasran; Makoto Tani; Toshiaki Sammori; Kazuhito Morisada

1997-01-01

250

Field determination of hydraulic conductivity of Norwood silt loam soil  

E-print Network

the soil when the tensiometers were inst alled . C Soil-Water Pressure Well-defined curves were obtained for the variation of soil-water pressure and its distribution and redistribution for the different depths of the profile during the infiltration.... This indicates the effect of evaporation on the downward movement of water, and the fact. that the variation in the rate of soil? water pressure with time will decrease when the lower depths of the soil are able to provide the soil surface with suffici- ent...

Saffaf, Adham Yassin

1966-01-01

251

Uncertainty in the determination of soil hydraulic parameters and its influence on the performance of two hydrological models of different complexity.  

NASA Astrophysics Data System (ADS)

Measurements of soil hydraulic properties is often a limiting factor in unsaturated zone modelling, especially at the larger scales. Investigations for the hydraulic characterization of soils are troublesome and the accuracy of the results obtained by the different methodologies is still under discussion. Therefore it is licit to wonder whether, in the simulation of water dynamics in the unsaturated zone, the uncertainty in the determination of the soil hydraulic parameters could be so high to become more important than the modelling approach selected for the simulation. In order to explore this issue, in this research the data collected in an intensive monitoring activity conducted in 2006 during the cropping season of a 10 ha maize field located in Northern Italy (Landriano - PV), were used to: i) compare different methods for determining soil hydraulic parameters and ii) evaluate the effect of the uncertainty in these parameters on different outputs (i.e. evapotranspiration, water content in the root zone, fluxes through the bottom boundary of the root zone) of two hydrological models of different complexity: SWAP, a widely used model of soil moisture dynamics in unsaturated soils based on Richards equation, and ALHyMUS, a conceptual model of the same dynamics based on a reservoir cascade scheme. Five are the direct and indirect methods executed to determine soil hydraulic parameters for each horizon of the experimental profile, two based on a parameter optimization to fit: a) the laboratory measured retention and hydraulic conductivity data and b) the field measured retention and hydraulic conductivity data; and three based on the application of widely used Pedo-Transfer Functions to the measurements of texture and organic matter: c) Rawls and Brakensiek (1989); d) HYPRES (Wösten et al., 1999); and e) ROSETTA (Schaap et al., 2001). Simulations were run using meteorological, irrigation and crop data measured at the experimental site for the time period June - October 2006. Results confirm the existence of a wide range of variation of the soil hydraulic parameter values evaluated with the different methods, remarkably in the case of the saturated hydraulic conductivity Ksat and the shape parameter alpha of the V-G curve (Van Genuchten, 1980). This is reflected in a variability which is, as expected, different for each model's output. This variability, in the case of the water content in the root zone and of the fluxes at the bottom of the root zone is found to be often larger than the difference between the same output simulated by the two models. Finally, it is shown that a good agreement in soil moisture patterns may occur even if evapotranspiration and percolation fluxes are significantly different, therefore multiple output variables shall be considered to test the performances of methods and models.

Baroni, G.; Facchi, A.; Gandolfi, C.; Ortuani, B.; Horeschi, D.; van Dam, J. C.

2009-04-01

252

Hydrology and Hydraulic Properties of a Bedded Evaporite Formation  

SciTech Connect

The Permian Salado Formation in the Delaware Basin of New Mexico is an extensively studied evaporite deposit because it is the host formation for the Waste Isolation Pilot Plant, a repository for transuranic wastes. Geologic and hydrologic studies of the Salado conducted since the mid-1970's have led to the development of a conceptual model of the hydrogeology of the formation that involves far-field permeability in anhydrite layers and at least some impure halite layers. Pure halite layers and some impure halite layers may not possess an interconnected pore network adequate to provide permeability. Pore pressures are probably very close to lithostatic pressure. In the near field around an excavation, dilation, creep, and shear have created and/or enhanced permeability and decreased pore pressure. Whether flow occurs in the far field under natural gradients or only after some threshold gradient is reached is unknown. If far-field flow does occur, mean pore velocities are probably on the order of a meter per hundreds of thousands to tens of millions of years. Flow dimensions inferred from most hydraulic-test responses are subradial, which is believed to reflect channeling of flow through fracture networks, or portions of fractures, that occupy a diminishing proportion of the radially available space, or through percolation networks that are not ''saturated'' (fully interconnected). This is probably related to the directional nature of the permeability created or enhanced by excavation effects. Inferred values of permeability cannot be separated from their associated flow dimensions. Therefore, numerical models of flow and transport should include heterogeneity that is structured to provide the same flow dimensions as are observed in hydraulic tests. Modeling of the Salado Formation around the WIPP repository should also include coupling between hydraulic properties and the evolving stress field because hydraulic properties change as the stress field changes.

BEAUHEIM,RICHARD L.; ROBERTS,RANDALL M.

2000-11-27

253

Sask method for testing hydraulic conductivity of soils by flat dilatometer (dmt)  

NASA Astrophysics Data System (ADS)

DMT is one of the most popular methods of determining soil parameters needed to design a safe construction. Apart from the basic outcome parameter obtained from DMT measurements hydraulic conductivity (k) can be determined, previously proposed DMTA and DMTC methods were modified. The basic idea of the method is that the return of the deformed membrane is due to soil and water pressure. In the proposed SASK method the hydraulic conductivity of the soil is determined by measuring time-varying pressures A and C. Research has been performed at the experimental site of the Department of Geotechnical Engineering, WULS. In the paper, the assumptions of the new method for determining the hydraulic conductivity k are presented. The proposed method allows us to determine a reliable value for the hydraulic conductivity of clay soils. Using this method, the value of hydraulic conductivity (k = 5,47*10-11) is similar to the results of BAT, DMTA and laboratory measurements.

Garbulewski, Kazimierz; ?akowicz, Stanis?aw; Rabarijoely, Simon; ?ada, Anna

2012-10-01

254

Relationships between soil erosion risk, soil use and soil properties in Mediterranean areas. A comparative study of three typical sceneries  

NASA Astrophysics Data System (ADS)

Generally, literature shows that the high variability of rainfall-induced soil erosion is related to climatic differences, relief, soil properties and land use. Very different runoff rates and soil loss values have been reported in Mediterranean cropped soils depending on soil management practices, but also in soils under natural vegetation types. OBJECTIVES The aim of this research is to study the relationships between soil erosion risk, soil use and soil properties in three typical Mediterranean areas from southern Spain: olive groves under conventional tillage, minimum tillage and no-till practices, and soils under natural vegetation. METHODS Rainfall simulation experiments have been carried out in order to assess the relationship between soil erosion risk, land use, soil management and soil properties in olive-cropped soils under different types of management and soils under natural vegetation type from Mediterranean areas in southern Spain RESULTS Results show that mean runoff rates decrease from 35% in olive grove soils under conventional tillage to 25% in olive (Olea europaea) grove soils with minimum tillage or no-till practices, and slightly over 22% in soils under natural vegetation. Moreover, considering the different vegetation types, runoff rates vary in a wide range, although runoff rates from soils under holm oak (Quercus rotundifolia), 25.70%, and marginal olive groves , 25.31%, are not significantly different. Results from soils under natural vegetation show that the properties and nature of the organic residues play a role in runoff characteristics, as runoff rates above 50% were observed in less than 10% of the rainfall simulations performed on soils with a organic layer. In contrast, more than half of runoff rates from bare soils reached or surpassed 50%. Quantitatively, average values for runoff water losses increase up to 2.5 times in unprotected soils. This is a key issue in the study area, where mean annual rainfall is above 600 mm. Regarding soil properties, the analysis shows that organic matter from soils under minimum tillage or no-till is strongly related with runoff, the amount of sediments in runoff and soil loss. In soils from olive groves, the amount of sediments in runoff was significantly related to soil pH. Moreover, for olive-cropped soils under conventional tillage, soil loss is strongly related with clayey texture, which is characteristic of these soils. Concerning this, the relationship between soil loss and coarse sand contents is highly significant, and shows that medium-sized soil particles are most prone to detachment and transport by runoff. Thus, the average content of these fractions in soils under conventional management is more than two times that from olive groves under minimal or no tillage, which are more coarsely textured. In fine-textured soils, hydraulic conductivity is reduced, thus increasing soil erosion risk. In addition, in sandy and silty soils with low clay content, infiltration rates are high even when soil sealing is observed. At the scale of this experiment, runoff generation and soil erosion risk decrease significantly in areas under natural vegetation, with lower clay contents

Gil, Juan; Priego-Navas, Mercedes; Zavala, Lorena M.; Jordán, Antonio

2013-04-01

255

Unsaturated soil hydraulic characterization using Full-Waveform Hydrogeophysical Inversion of Time-Lapse, GPR Data  

NASA Astrophysics Data System (ADS)

Geophysical methods are increasingly being used to provide quantitative information of subsurface distributions and hydrological properties. Traditionally, the geophysical data are inverted first, and the obtained information is subsequently used to calibrate the hydrological model. This ill-posed sequential inversion ignores the potential constraints that are provided by available hydrological information (e.g., mass balance, shape of wetting front, etc.). Additionally, artifacts of the geophysical data inversion (e.g., due to lack of sensitivity, high measurement and modeling errors, etc.) will be directly translated in errors of the hydrological model calibration. In this study, we explore an alternative method by resorting to integrated hydrogeophysical inversion of time-lapse, proximal ground penetrating radar (GPR) data to remotely estimate unsaturated soil hydraulic properties of a laboratory sand during four infiltration events. Hydrodynamic modeling was based on a one-dimensional solution of Richard's equation and was solved numerically using HYDRUS-1D code. The radar model involves a full-waveform solution of Maxwell's equations for wave propagation in three-dimensional multilayered media. Petrophysical relationships have been used to link radar and hydrological state variables. In total, 16 GPR observations were made with uneven time steps, to catch most of the observed water dynamics. Results were compared with TDR measurements and ground truth measurements. GPR-based predictions capture major features of TDR and better agree with visual observations. Finally, we tested the approach in real field conditions for a single profile and traditional reference methods were used for comparison. The results suggest that the proposed method is promising for characterizing the shallow subsurface hydraulic properties at the field scale with a high spatial resolution.

Jadoon, K. Z.; Lambot, S.; Slob, E. C.; Vereecken, H.

2009-04-01

256

Use of field and laboratory methods for estimating unsaturated hydraulic properties under different land-use  

NASA Astrophysics Data System (ADS)

Adequate water management is required to improve the efficiency and sustainability of agricultural systems when water is scarce or over-abundant, especially in the case of land-use changes. In order to quantify, to predict and eventually to control water and solute transport into soil, soil hydraulic properties need to be determined precisely. As their determination is often tedious, expensive and time-consuming, many alternative field and laboratory techniques are now available. The aim of this study was to determine unsaturated soil hydraulic properties under different land-uses and to compare the results obtained with different measurement methods (Beerkan, Disk infiltrometer, Evaporation, pedotransfer function). The study has been realised on a tropical sandy soil in a mini watershed in NE Thailand. The experimental plots were positioned in a rubber tree plantation in different positions along a slope, in ruzi grass pasture and in an original forest site. Non parametric statistics demonstrated that van Genuchten unsaturated soil parameters (Ks, ? and n), were significantly different according to the measurement methods employed whereas location was not a significant discriminating factor when all methods were considered together. However within each method, parameters n and ? were statistically different according to the sites. These parameters were used with Hydrus1D for a one year simulation and computed pressure head did not show noticeable differences for the various sets of parameters, highlighting the fact that for modelling, any of these measurement method could be employed. The choice of the measurement method would therefore be motivated by the simplicity, robustness and its low cost.

Siltecho, S.; Hammecker, C.; Sriboonlue, V.; Clermont-Dauphin, C.; Trelo-ges, V.; Antonino, A. C. D.; Angulo-Jaramillo, R.

2014-06-01

257

Use of field and laboratory methods for estimating unsaturated hydraulic properties under different land uses  

NASA Astrophysics Data System (ADS)

Adequate water management is required to improve the efficiency and sustainability of agricultural systems when water is scarce or over-abundant, especially in the case of land use changes. In order to quantify, to predict and eventually to control water and solute transport into soil, soil hydraulic properties need to be determined precisely. As their determination is often tedious, expensive and time-consuming, many alternative field and laboratory techniques are now available. The aim of this study was to determine unsaturated soil hydraulic properties under different land uses and to compare the results obtained with different measurement methods (Beerkan, disc infiltrometer, evaporation, pedotransfer function). The study has been realized on a tropical sandy soil in a mini-watershed in northeastern Thailand. The experimental plots were positioned in a rubber tree plantation in different positions along a slope, in ruzi grass pasture and in an original forest site. Non-parametric statistics demonstrated that van Genuchten unsaturated soil parameters (Ks, ? and n) were significantly different according to the measurement methods employed, whereas the land use was not a significant discriminating factor when all methods were considered together. However, within each method, parameters n and ? were statistically different according to the sites. These parameters were used with Hydrus1D for a 1-year simulation and computed pressure head did not show noticeable differences for the various sets of parameters, highlighting the fact that for modeling, any of these measurement methods could be employed. The choice of the measurement method would therefore be motivated by the simplicity, robustness and its low cost.

Siltecho, S.; Hammecker, C.; Sriboonlue, V.; Clermont-Dauphin, C.; Trelo-ges, V.; Antonino, A. C. D.; Angulo-Jaramillo, R.

2015-03-01

258

A Particle Smoother with Sequential Importance Resampling for soil hydraulic parameter estimation: A lysimeter experiment  

NASA Astrophysics Data System (ADS)

An adequate description of soil hydraulic properties is essential for a good performance of hydrological forecasts. So far, several studies showed that data assimilation could reduce the parameter uncertainty by considering soil moisture observations. However, these observations and also the model forcings were recorded with a specific measurement error. It seems a logical step to base state updating and parameter estimation on observations made at multiple time steps, in order to reduce the influence of outliers at single time steps given measurement errors and unknown model forcings. Such outliers could result in erroneous state estimation as well as inadequate parameters. This has been one of the reasons to use a smoothing technique as implemented for Bayesian data assimilation methods such as the Ensemble Kalman Filter (i.e. Ensemble Kalman Smoother). Recently, an ensemble-based smoother has been developed for state update with a SIR particle filter. However, this method has not been used for dual state-parameter estimation. In this contribution we present a Particle Smoother with sequentially smoothing of particle weights for state and parameter resampling within a time window as opposed to the single time step data assimilation used in filtering techniques. This can be seen as an intermediate variant between a parameter estimation technique using global optimization with estimation of single parameter sets valid for the whole period, and sequential Monte Carlo techniques with estimation of parameter sets evolving from one time step to another. The aims are i) to improve the forecast of evaporation and groundwater recharge by estimating hydraulic parameters, and ii) to reduce the impact of single erroneous model inputs/observations by a smoothing method. In order to validate the performance of the proposed method in a real world application, the experiment is conducted in a lysimeter environment.

Montzka, Carsten; Hendricks Franssen, Harrie-Jan; Moradkhani, Hamid; Pütz, Thomas; Han, Xujun; Vereecken, Harry

2013-04-01

259

Hydraulics  

NSDL National Science Digital Library

These interactive learning objects, created by instructors from Fox Valley Technical College and other colleges in the Wisconsin Technical College program, focus on concepts that cover a broad-based electromechanical program. Here visitors will find learning objects in Hydraulics with over 25 lessons in Actuators, Relief Valves, Basic Concepts, and Directional Control Valves.

260

Variations in hydrologic soil properties caused by mining activities  

SciTech Connect

Five land uses related to surface mining were selected for this study. The lands ranged from undisturbed forested soil to reclaimed spoil. The experiments were conducted at the J.J. Track and Sahara mines in Saline County, Illinois. On each land-use type, three 3 x 3 m/sup 2/ plots were selected and each plot was divided into nine subplots for conducting experiments. On each subplot, several hydrologic soil parameters were measured including bulk density, sorptivity, satiated hydraulic conductivity, and infiltration. The incipient ponding time for a 10-year 24-hour storm was calculated incorportated with the measured soil properties using the Parlange-Smith equation. Hydrologic properties among the land uses were compared by using the Weibull plotting position technique. The results show that the hydrologic soil properties of forested soil can become similar to those of unmined agricultural soil through the removal of vegetation. The infiltration properties of the mined land can be restored to a pre-mining condition (or even better), if the spoil receives proper reclamation. However, loss of water through evaporation from the reclaimed soil is higher than that of the unmined agricultural soil.

Chong, S.K.; Moore, S.M.

1982-12-01

261

Water retention and hydraulic conductivity of a loamy sand soil as influenced by crop rotation and fertilization  

Microsoft Academic Search

Measurements are reported of soil organic carbon content, dry bulk density, water retention characteristics, and saturated hydraulic conductivity of a sandy loam soil with two different crop rotations and two levels of fertilization. The water retention characteristics were fitted to the van Genuchten equation. Values of unsaturated hydraulic conductivity were estimated by calculation. It was found that crop rotation has

A. R. Dexter; E. A. Czy?; J. Niedzwiecki; C. Ma?kowiak

2001-01-01

262

Column-scale unsaturated hydraulic conductivity estimates in coarse-textured homogeneous and layered soils derived under steady-state evaporation from a water table  

NASA Astrophysics Data System (ADS)

Steady-state evaporation from a water table has been extensively studied for both homogeneous and layered porous media. For layered media it is of interest to find an equivalent homogeneous medium and define “effective” hydraulic properties. In this paper a new solution for steady-state evaporation from coarse-textured porous media is presented. Based on this solution, the evaporation rate represents a macroscopic (column-scale) measure of unsaturated hydraulic conductivity at the pressure head equal to the maximum extent of the hydraulically connected region above the water table. The presented approach offers an alternative method for determination of unsaturated hydraulic conductivity of homogeneous coarse-textured soils and a new solution for prediction of the effective unsaturated hydraulic conductivity of layered coarse-textured soils. The solution was evaluated with both experimental data and numerical simulations. Comparison with experimental data and numerical results for hypothetically layered soil profiles demonstrate the applicability of the proposed approach for coarse-textured soils.

Sadeghi, Morteza; Tuller, Markus; Gohardoust, Mohammad R.; Jones, Scott B.

2014-11-01

263

Status Report for Remediation Decision Support Project, Task 1, Activity 1.B – Physical and Hydraulic Properties Database and Interpretation  

SciTech Connect

The objective of Activity 1.B of the Remediation Decision Support (RDS) Project is to compile all available physical and hydraulic property data for sediments from the Hanford Site, to port these data into the Hanford Environmental Information System (HEIS), and to make the data web-accessible to anyone on the Hanford Local Area Network via the so-called Virtual Library. In past years efforts were made by RDS project staff to compile all available physical and hydraulic property data for Hanford sediments and to transfer these data into SoilVision{reg_sign}, a commercial geotechnical software package designed for storing, analyzing, and manipulating soils data. Although SoilVision{reg_sign} has proven to be useful, its access and use restrictions have been recognized as a limitation to the effective use of the physical and hydraulic property databases by the broader group of potential users involved in Hanford waste site issues. In order to make these data more widely available and useable, a decision was made to port them to HEIS and to make them web-accessible via a Virtual Library module. In FY08 the objectives of Activity 1.B of the RDS Project were to: (1) ensure traceability and defensibility of all physical and hydraulic property data currently residing in the SoilVision{reg_sign} database maintained by PNNL, (2) transfer the physical and hydraulic property data from the Microsoft Access database files used by SoilVision{reg_sign} into HEIS, which has most recently been maintained by Fluor-Hanford, Inc., (3) develop a Virtual Library module for accessing these data from HEIS, and (4) write a User's Manual for the Virtual Library module. The development of the Virtual Library module was to be performed by a third party under subcontract to Fluor. The intent of these activities is to make the available physical and hydraulic property data more readily accessible and useable by technical staff and operable unit managers involved in waste site assessments and remedial action decisions for Hanford. This status report describes the history of this development effort and progress to date.

Rockhold, Mark L.

2008-09-26

264

The effect of electrolyte composition on hydraulic conductivity of some Texas soils  

E-print Network

the soil was Ca-saturated (SAR=0), but almost the same degree of change occurred when the soil was in contact with the solution of SAR=10. This indicates a limited lack of stability of the soil under wet conditions rather than Na induced changes...THE EFFECT OF ELECTROLYTE COMPOSITION ON HYDRAULIC CONDUCTIVITY OF SOME TEXAS SOILS A Thesis By BIJAN NAGHSHINEH-POUR Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree...

Naghshineh-Pour, Bijan

1968-01-01

265

Land-use effects on flood generation - considering soil hydraulic measurements in modelling  

NASA Astrophysics Data System (ADS)

The investigation in the catchment of the Mulde (51°0'55" N, 13°15'54" E Saxony, Germany) researches the effect of afforestation measures on the soil hydraulic properties. The concept of a "false chronosequence" was used to quantify the time-dependent dynamical character of the forest impact. Four adjacent plots were identified at a test location with comparable pedological start conditions and a set of tree stands of different age: (1) arable field (initial state); (2) 6-year-old afforestation; (3) 50-year-old afforestation; (4) ancient natural forest ("target" stocking). Water retention curves and unsaturated conductivities were analysed in the lab. In the field, the undisturbed infiltration capacities were measured quantitatively (hood infiltrometer) and qualitatively (brilliant blue tracer). Pronounced differences between all 4 plots were detected. The afforestation causes an increased infiltration and soil water retention potential. Especially the topsoil layers showed a distinct increase in conductivity and portion of coarse/middle pores. The influence of these changes on rainfall-runoff calculations at the test location was analysed in this study.

Wahren, A.; Feger, K.-H.; Schwärzel, K.; Münch, A.

2009-08-01

266

Nitrate Control of Root Hydraulic Properties in Plants: Translating Local Information to  

E-print Network

between nitrate availability and water acquisition results from changes in cell membrane hydraulic that the increase in root hydraulic conductance in one part causes a decline of water uptake in the other part dueNitrate Control of Root Hydraulic Properties in Plants: Translating Local Information to Whole

Holbrook, N. Michele

267

1 Estimating aquifer hydraulic properties from the inversion of surface 2 Streaming Potential (SP) anomalies  

E-print Network

1 Estimating aquifer hydraulic properties from the inversion of surface 2 Streaming Potential (SP with the geometry of the water table. It follows that 11 SP measurements can be used to estimate aquifer hydraulic and found that we 14 are able to estimate the hydraulic conductivity and the depth 15 and the thickness

Sailhac, Pascal

268

Enrichment strategies and convergence properties of the XFEM for hydraulic fracture problems  

E-print Network

Enrichment strategies and convergence properties of the XFEM for hydraulic fracture problems Finite Ele- ment Method (XFEM) for modeling hydraulic fractures (HF), two classes of boundary value energy, is not suitable for modeling hydraulic fractures in which the uid and the fracture fronts

Peirce, Anthony

269

Mechanical and hydraulic properties of rocks related to induced seismicity  

USGS Publications Warehouse

Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now available that clearly demonstrates this stress-flow behavior. Two approaches have been used in attempting to numerically model such behavior: (1) continuum models, and (2) discrete models. The continuum approach only needs information as to average values of fracture spacing and material properties. But because of the inherent complexity of fractured rock masses and the corresponding decrease in symmetry, it is difficult to develop an equivalent continuum that will simulate the behavior of the entire system. The discrete approach, on the other hand, requires details of the fracture geometry and material properties of both fractures and rock matrix. The difficulty in obtaining such information has been considered a serious limitation of discrete models, but improved borehole techniques can enable one to obtain the necessary data, at least in shallow systems. The possibility of extending these methods to deeper fracture systems needs more investigation. Such data must be considered when deciding whether to use a continuum or discrete model to represent the interaction of rock and fluid forces in a fractured rock system, especially with regard to the problem of induced seismicity. When one is attempting to alter the pressure distribution in a fault zone by injection or withdrawal of fluids, the extent to which this can be achieved will be controlled in large measure by the behavior of the fractures that communicate with the borehole. Since this is essentially a point phenomenon, i.e., the changes will propagate from a relatively small region around the borehole, the use of a discrete model would appear to be preferable. ?? 1977.

Witherspoon, P.A.; Gale, J.E.

1977-01-01

270

Mechanical properties of lunar soil and simulants  

Microsoft Academic Search

Investigation of the physical and mechanical properties of lunar soil carried out by the USSR and the USA, both in situ and on returned samples, has resulted in considerable information regarding the soil properties. This has permitted the development of lunar soil simulants for purposes of evaluating lunar technologies. Comparison tests among lunar soil simulants that have different granulometric composition

Valerij V. Gromov; W. D. Carrier III

1992-01-01

271

Moisture retention properties of a mycorrhizal soil  

Microsoft Academic Search

The water relations of arbuscular mycorrhizal plants have been compared often, but virtually nothing is known about the comparative water relations of mycorrhizal and nonmycorrhizal soils. Mycorrhizal symbiosis typically affects soil structure, and soil structure affects water retention properties; therefore, it seems likely that mycorrhizal symbiosis may affect soil water relations. We examined the water retention properties of a Sequatchie

Robert M. Augel; Ann J. W. Stodola; Jayme E. Tims; Arnold M. Saxton

2001-01-01

272

An insight into the role of hydraulic history on the volume changes of anisotropic clayey soils  

NASA Astrophysics Data System (ADS)

Volume changes of natural and compacted soils induced by changes in their water content have many practical implications in the service life of earth dams, river and canal embankments, and waste disposal facilities. An insight into the overall strain response of a clayey soil upon gradual wetting and drying is provided here. Experimental data coming from oedometer and isotropic tests under suction and net stress control are presented for a compacted clay with an initial anisotropic fabric, highlighting the relevant role played by the hydraulic path on collapse, swelling, and shrinkage strains. Irreversible strains could be observed after wetting-drying paths and the subsequent drying-wetting cycle. Both stress and hydraulic histories play a role in the evolution of the directional fabric of clayey soils. The experimental data could be reproduced with a rather simple elastic-plastic constitutive model with a mixed isotropic-rotational hardening, previously conceived for saturated soils. The model is extended to unsaturated conditions by substituting the saturated effective stress with a measure of the average stress acting on the soil skeleton and by introducing generalized hardening rules governed by both plastic strains and degree of saturation. Coupling between the mechanical and the hydraulic behavior is provided by the water retention curve, in which degree of saturation is adopted as a useful measure of the soil water content.

Romero, Enrique; Jommi, Cristina

2008-05-01

273

Percolation and transport in a sandy soil under a natural hydraulic gradient  

Microsoft Academic Search

Unsaturated flow and transport under a natural hydraulic gradient in a Mediterranean climate were investigated with a field tracer experiment combined with laboratory analyses and numerical modeling. Bromide was applied to the surface of a sandy soil during the dry season. During the subsequent rainy season, repeated sediment sampling tracked the movement of bromide through the profile. Analysis of data

Christopher T. Green; David A. Stonestrom; Barbara A. Bekins; Katherine C. Akstin; Marjorie S. Schulz

2005-01-01

274

EFFECTS OF ROCK FRAGMENTS INCORPORATED IN THE SOIL MATRIX ON CONCENTRATED FLOW HYDRAULICS AND EROSION 1836  

Technology Transfer Automated Retrieval System (TEKTRAN)

Rock fragments can act as a controlling factor for erosional rates and patterns in the landscape. Thus, the objective of this study is to better understand the role that rock fragments incorporated into the soil matrix have on concentrated flow hydraulics and erosion . Laboratory flume experiments...

275

Predicting Saturated Hydraulic Conductivity from Percolation Test Results in Layered Silt Loam Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

The size of on-site waste disposal systems is usually determined by one or more percolation tests performed on the proposed site. The objectives of this study were to develop an empirical relationship between the saturated hydraulic conductivity (Ks) of layered soils and their percolation times (PT)...

276

EFFECTS OF ELECTROOSMOSIS ON SOIL TEMPERATURE AND HYDRAULIC HEAD: I. FIELD OBSERVATIONS  

EPA Science Inventory

A field test to quantify the changes of soil temperature and hydraulic head during electroosmosis was conducted. The anode (3.1 m x 3.4 m) was created by laying pieces of titanium mesh coated with mixed metal oxides on top of a 3 cm thick sand layer at a depth of 0.4 m. The catho...

277

EFFECTS OF ELECTROOSMOSIS ON SOIL TEMPERATURE AND HYDRAULIC HEAD: I. FIELD OBSERVATION  

EPA Science Inventory

A field test to quantify the changes of soil temperature and hydraulic head during electroosmosis has been conducted. The anode (3.1 m x 3.4m) was created by laying pieces of titanium mesh coated with mixed metal oxides on tope of a 3 cm thick sand layer at a depth of 0.4 m. The ...

278

A review of the Rawls et al. (1982) soil hydraulic pedotransfer function  

Technology Transfer Automated Retrieval System (TEKTRAN)

For many applications that involve the use of environmental simulation models, soil water retention and hydraulic conductivity data are not available and therefore need to be estimated. The current version of the APEX model – that is being used in the national scale CEAP project to evaluate on-site ...

279

Probability distributions for hydraulic conductivity of compacted soil liners  

SciTech Connect

This paper describes an analysis of hydraulic conductivity data collected from 57 landfill liners and covers throughout North America. Statistical characteristics of the data are summarized, and goodness-of-fit analyses are performed on each set to determine a distributional form that can be used to describe spatial variability of hydraulic conductivity. The statistics of hydraulic conductivity are shown to vary widely. The mean varied from 2.9 [times] 10[sup [minus]9] to 1 [times] 10[sup [minus]5] cm/s, the coefficient of variation varied between 27 and 767, the coefficient of skewness between [minus]0.23 and 7.7, and the coefficient of kurtosis from 1.75 to 58. Goodness-of-fit tests show that the two-parameter log-normal hypothesis is often rejected. The traditional two-parameter log-normal, generalized extreme value (GEV), the three-parameter gamma, and inverse Gaussian. The analyses show that the three-parameter log-normal and GEV result in superior fits to the data.

Benson, C.H. (Univ. of Wisconsin, Madison (United States))

1993-03-01

280

Lunar soil properties and soil mechanics  

NASA Technical Reports Server (NTRS)

The study to identify and define recognizable fabrics in lunar soil in order to determine the history of the lunar regolith in different locations is reported. The fabric of simulated lunar soil, and lunar soil samples are discussed along with the behavior of simulated lunar soil under dynamic and static loading. The planned research is also included.

Mitchell, J. K.; Houston, W. N.; Hovland, H. J.

1972-01-01

281

Effect of spatial variability of soil properties on infiltration  

NASA Astrophysics Data System (ADS)

Topography and soil properties are key determinants of spatial variability of water content. Prediction of soil hydraulic properties are essential for modeling water flow and solute transport. In the southeastern of Buenos Aires Province, the effect of the relief on soil spatial variability is result of the relationship between elevation and effective depth (ED). Digital elevation models (DEM) provide quantitive information about relief. The objective was to determine the effect of spatial variability of soil properties on infiltration. The field was 50 ha and the soil classes were vertic Hapludoll, typic and petrocalcic Argiudoll. ED was measured using Gidding_Soil_Sampler® in 30x30m grid size. Elevation data were measured ussing a DGPS Trimble_R3®. From this, a DEM was generated. Two elevation and ED areas were delineated named High and Low zones. Three soil samples were taken at each zone with three replications at depth 0-30 and 30-90 cm. Texture, bulk density (?b) and organic matter (OM) were determined. A disc infiltrometer was used to determine the water infiltration rate (i). Clay content (As) and OM were homogeneous in the profile of the High zone. However, As content at 30-90 cm decreased in the Low zone. At the High zone, ?b ranged from 1.31 to 1.34 g cm-3 and was higher than at the Low zone (?b=1.16 - 1.27 g cm-3). Also the i had less variation at the High zone. Under pressure head of -1 cm , the i increased in the Low zone. At lower pressure heads, the i was greater in the High zone. Higher i at the Low zone could be due to major ED, textural heterogeneity and higher OM content. Textural homogeneity, shallow ED and high ?b allowed a more stable i at the High zone. Using topography and ED is a promising way of characterizing soil hydraulic behavior and its spatial variability across a field.

Domenech, Marisa; Castro Franco, Mauricio; Aparicio, Virginia; Costa, José Luis

2013-04-01

282

WATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Saturated hydraulic conductivity determined by on1  

E-print Network

WATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Saturated hydraulic conductivity determined hydraulic conductivity. We used Hydrus-1D to simulate the water in-6 filtration. We generated water content Soil hydraulic properties, represented by the soil water retention (h) and hydraulic22 conductivity K

Boyer, Edmond

283

Temporal variability of selected chemical and physical properties of topsoil of three soil types  

NASA Astrophysics Data System (ADS)

Temporal variability of soil properties measured in surface horizons of three soil types (Haplic Cambisol, Greyic Phaeozem, Haplic Luvisol) was studied in years 2007, 2008, 2009 and 2010. Undisturbed soil samples were taken every month to evaluate the actual field soil-water content, bulk density, porosity and hydraulic properties. The grab soil samples were taken every month to evaluate aggregate stability using the WSA (water stable aggregates) index, pHH2O and pHKCl, soil organic matter content and quality. Unsaturated hydraulic conductivity for pressure head of -2 cm was measured directly in the field using the minidisk tension infiltrometer. In addition soil structure was documented on micromorphological images. In some cases, the similar trends of the pHH2O , pHKCl , A400/A600, rod, P, ?field or WSA values were observed in different soils. Interestingly, the similar trends were found mostly for the Haplic Cambisol and the Greyic Phaeozem despite the fact that these soils considerably differed (different soil substrate, pedogenetic processes, etc.) and that variable crops (winter wheat and spring wheat) were planted at both locations during two years (2007 and 2006). Mostly different trends were observed for the Haplic Luvisol and the Greyic Phaeozem (soil of the same substrate). The reason could be attributed to a high vulnerability of the Haplic Luvisol to soil degradation in comparison to that of the Greyic Phaeozem. Parameters of hydraulic properties were highly variable and did not show similar trends for different soils (except the saturated soil water content and the slope of the retention curve at the inflection point for Haplic Cambisol and Greyic Phaeozem). Soil structure, aggregate stability and soil hydraulic properties were interrelated and depended on plant growth, rainfall compaction and tillage. The drier conditions in some soils positively influenced the soil aggregate stability, the slope of the retention curve at the inflection point and hydraulic conductivity. Probably due to the high variation of soil hydraulic properties no closer correlation between them and other properties was detected. Despite that the slope of the retention curve at the inflection point (which should indicate physical quality of the soil, e.g. soil aggregation and consequently soil porosity system) in many cases increased (decreased) when also the soil aggregate stability and hydraulic conductivity values increased (decreased), no closer correlation was revealed when analyzing for the entire 4 year period. The study showed different trends during different years. This was anticipated in the Greyic Phaeozem where different cops (spring wheat, winter wheat and winter barley) were planted during different years. Different trends were however observed also in the Haplic Cambisol and the Haplic Luvisol, where the same or similar crops (in both cases mostly winter wheat and ones winter barley) was sown. Results showed that climatic conditions (mostly during he winter end spring) played dominant role. Thus data, which were obtained during one year period, could not be used to generalize a soil regime in a particular soil and crop. Our results showed that it is impossible to apply any model, which would be based on statistical analyses, to predict soil properties development during one year or even longer period. Results indicate that findings cannot be used to generalize soil properties for other soil types, plants or climates. Acknowledgment: Authors acknowledge the financial support of the Czech Science Foundation (GA CR 526/08/0434) and the Ministry of Agriculture of the Czech Republic (QJ1230319).

Jirku, Veronika; Kodesova, Radka; Nikodem, Antonin; Muhlhanselova, Marcela; Zigova, Anna

2013-04-01

284

Mechanical properties of lunar soil and simulants  

NASA Astrophysics Data System (ADS)

Investigation of the physical and mechanical properties of lunar soil carried out by the USSR and the USA, both in situ and on returned samples, has resulted in considerable information regarding the soil properties. This has permitted the development of lunar soil simulants for purposes of evaluating lunar technologies. Comparison tests among lunar soil simulants that have different granulometric composition have shown that there are significant variations in some soil properties. This fact could have a serious influence on the potential of lunar soil as a building material, and on the mechanical parameters related to lunar exploration and exploitation. These results also demonstrate the importance of further investigations, and the necessity of the development of soil simulants with specific properties. For future lunar surface mission planning, it is necessary to take into account the variety of the soil properties, and to develop new equipment for measuring in situ soil properties.

Gromov, Valerij V.; Carrier, W. D., III

285

Estimability analysis for optimization of hysteretic soil hydraulic parameters using data of a field irrigation experiment  

NASA Astrophysics Data System (ADS)

The estimability analysis has been proposed to improve the quality of parameter optimization. For field data, wetting and drying processes may complicate optimization of soil hydraulic parameters. The objectives of this study were to apply estimability analysis for improving optimization of soil hydraulic parameters and compare models with and without considering hysteresis. Soil water pressure head data of a field irrigation experiment were used. The one-dimensional vertical water movement in variably-saturated soil was described with the Richards equation using the HYDRUS-1D code. Estimability of the unimodal van Genuchten - Mualem hydraulic model parameters as well as of the hysteretic parameter model of Parker and Lenhard was classified according to a sensitivity coefficient matrix. The matrix was obtained by sequentially calculating effects of initial parameter variations on changes in the simulated pressure head values. Optimization was carried out by means of the Levenberg-Marquardt method as implemented in the HYDRUS-1D code. The parameters ?, Ks, ?s, and n in the nonhysteretic model were found sensitive and parameter ?s and n strongly correlated with parameter n in the nonhysteretic model. When assuming hysteresis, the estimability was highest for ?w and decreased with soil depth for Ks and ?d, and increased for ?s and n. The hysteretic model could approximate the pressure heads in the soil by considering parameters from wetting and drying periods separately as initial estimates. The inverse optimization could be carried out more efficiently with most estimable parameters. Despite the weaknesses of the local optimization algorithm and the inflexibility of the unimodal van Genuchten model, the results suggested that estimability analysis could be considered as a guidance to better define the optimization scenarios and then improved the determination of soil hydraulic parameters.

Ngo, Viet V.; Gerke, Horst H.; Badorreck, Annika

2014-05-01

286

Reforesting severely degraded grassland in the Lesser Himalaya of Nepal: Effects on soil hydraulic conductivity and overland flow production  

NASA Astrophysics Data System (ADS)

degraded hillslopes in the Lesser Himalaya challenge local communities as a result of the frequent occurrence of overland flow and erosion during the rainy season and water shortages during the dry season. Reforestation is often perceived as an effective way of restoring predisturbance hydrological conditions but heavy usage of reforested land in the region has been shown to hamper full recovery of soil hydraulic properties. This paper investigates the effect of reforestation and forest usage on field-saturated soil hydraulic conductivities (Kfs) near Dhulikhel, Central Nepal, by comparing degraded pasture, a footpath within the pasture, a 25 year old pine reforestation, and little disturbed natural forest. The hillslope hydrological implications of changes in Kfs with land-cover change were assessed via comparisons with measured rainfall intensities over different durations. High surface and near-surface Kfs in natural forest (82-232 mm h-1) rule out overland flow occurrence and favor vertical percolation. Conversely, corresponding Kfs for degraded pasture (18-39 mm h-1) and footpath (12-26 mm h-1) were conducive to overland flow generation during medium- to high-intensity storms and thus to local flash flooding. Pertinently, surface and near-surface Kfs in the heavily used pine forest remained similar to those for degraded pasture. Estimated monsoonal overland flow totals for degraded pasture, pine forest, and natural forest were 21.3%, 15.5%, and 2.5% of incident rainfall, respectively, reflecting the relative ranking of surface Kfs. Along with high water use by the pines, this lack of recovery of soil hydraulic properties under pine reforestation is shown to be a critical factor in the regionally observed decline in base flows following large-scale planting of pines and has important implications for regional forest management.

Ghimire, Chandra Prasad; Bonell, Mike; Bruijnzeel, L. Adrian; Coles, Neil A.; Lubczynski, Maciek W.

2013-12-01

287

Towards soil property retrieval from space: Proof of concept using in situ observations  

NASA Astrophysics Data System (ADS)

Soil moisture is a key variable that controls the exchange of water and energy fluxes between the land surface and the atmosphere. However, the temporal evolution of soil moisture is neither easy to measure nor monitor at large scales because of its high spatial variability. This is mainly a result of the local variation in soil properties and vegetation cover. Thus, land surface models are normally used to predict the evolution of soil moisture and yet, despite their importance, these models are based on low-resolution soil property information or typical values. Therefore, the availability of more accurate and detailed soil parameter data than are currently available is vital, if regional or global soil moisture predictions are to be made with the accuracy required for environmental applications. The proposed solution is to estimate the soil hydraulic properties via model calibration to remotely sensed soil moisture observation, with in situ observations used as a proxy in this proof of concept study. Consequently, the feasibility is assessed, and the level of accuracy that can be expected determined, for soil hydraulic property estimation of duplex soil profiles in a semi-arid environment using near-surface soil moisture observations under naturally occurring conditions. The retrieved soil hydraulic parameters were then assessed by their reliability to predict the root zone soil moisture using the Joint UK Land Environment Simulator model. When using parameters that were retrieved using soil moisture observations, the root zone soil moisture was predicted to within an accuracy of 0.04 m3/m3, which is an improvement of ?0.025 m3/m3 on predictions that used published values or pedo-transfer functions.

Bandara, Ranmalee; Walker, Jeffrey P.; Rüdiger, Christoph

2014-05-01

288

Sagebrush carrying out hydraulic lift enhances surface soil nitrogen cycling and nitrogen uptake into inflorescences.  

PubMed

Plant roots serve as conduits for water flow not only from soil to leaves but also from wetter to drier soil. This hydraulic redistribution through root systems occurs in soils worldwide and can enhance stomatal opening, transpiration, and plant carbon gain. For decades, upward hydraulic lift (HL) of deep water through roots into dry, litter-rich, surface soil also has been hypothesized to enhance nutrient availability to plants by stimulating microbially controlled nutrient cycling. This link has not been demonstrated in the field. Working in sagebrush-steppe, where water and nitrogen limit plant growth and reproduction and where HL occurs naturally during summer drought, we slightly augmented deep soil water availability to 14 HL+ treatment plants throughout the summer growing season. The HL+ sagebrush lifted greater amounts of water than control plants and had slightly less negative predawn and midday leaf water potentials. Soil respiration was also augmented under HL+ plants. At summer's end, application of a gas-based (15)N isotopic labeling technique revealed increased rates of nitrogen cycling in surface soil layers around HL+ plants and increased uptake of nitrogen into HL+ plants' inflorescences as sagebrush set seed. These treatment effects persisted even though unexpected monsoon rainstorms arrived during assays and increased surface soil moisture around all plants. Simulation models from ecosystem to global scales have just begun to include effects of hydraulic redistribution on water and surface energy fluxes. Results from this field study indicate that plants carrying out HL can also substantially enhance decomposition and nitrogen cycling in surface soils. PMID:24191007

Cardon, Zoe G; Stark, John M; Herron, Patrick M; Rasmussen, Jed A

2013-11-19

289

Sagebrush carrying out hydraulic lift enhances surface soil nitrogen cycling and nitrogen uptake into inflorescences  

PubMed Central

Plant roots serve as conduits for water flow not only from soil to leaves but also from wetter to drier soil. This hydraulic redistribution through root systems occurs in soils worldwide and can enhance stomatal opening, transpiration, and plant carbon gain. For decades, upward hydraulic lift (HL) of deep water through roots into dry, litter-rich, surface soil also has been hypothesized to enhance nutrient availability to plants by stimulating microbially controlled nutrient cycling. This link has not been demonstrated in the field. Working in sagebrush-steppe, where water and nitrogen limit plant growth and reproduction and where HL occurs naturally during summer drought, we slightly augmented deep soil water availability to 14 HL+ treatment plants throughout the summer growing season. The HL+ sagebrush lifted greater amounts of water than control plants and had slightly less negative predawn and midday leaf water potentials. Soil respiration was also augmented under HL+ plants. At summer’s end, application of a gas-based 15N isotopic labeling technique revealed increased rates of nitrogen cycling in surface soil layers around HL+ plants and increased uptake of nitrogen into HL+ plants’ inflorescences as sagebrush set seed. These treatment effects persisted even though unexpected monsoon rainstorms arrived during assays and increased surface soil moisture around all plants. Simulation models from ecosystem to global scales have just begun to include effects of hydraulic redistribution on water and surface energy fluxes. Results from this field study indicate that plants carrying out HL can also substantially enhance decomposition and nitrogen cycling in surface soils. PMID:24191007

Cardon, Zoe G.; Stark, John M.; Herron, Patrick M.; Rasmussen, Jed A.

2013-01-01

290

Hydraulic filling of dams constructed of silty soils, using a flattened profile  

Microsoft Academic Search

Conclusions  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Construction experience and experimental investigations established that it is advantageous to use silty soils for the construction\\u000a of dams with a flattened profile, consisting of a downstream impervious shoulder (hydraulic fill) and upstream wave-resistant\\u000a ramp (dumped material). This design eliminates the construction of massive shoulders of gravel-pebble material which are needed\\u000a in hydraulic filling of compressed dams of

D. L. Melamut; L. G. Borodulina

1973-01-01

291

Influence of irrigation and fertilization on transpiration and hydraulic properties of Populus deltoides.  

SciTech Connect

Summary Long-term hydraulic acclimation to resource availability was explored in 3-year-bld Populus deltoides Bartr. ex Marsh. clones by examining transpiration. leaf-specific hydraulic conductance (GL), canopy stomatal conductance (Gs) and leaf to sapwood area ratio (AL:Asi)n response to imgation (13 and 551 mm year in addition to ambient precipitation) and fertilization (0 and 120 kg N ha-' year-'). Sap flow was measured continuously over one growing season with thermal dissipation probes. Fertilization had a greater effect on growth and hydraulic properties than imgation, and fertilization effects were independent of irrigation treatment. Transpiration on a ground area basis (E) ranged between 0.3 and 1.8 mm day-', and increased 66% and 90% in response to imgation and fertilization, respectively. Increases in GL, Gs at a reference vapor pressure deficit of 1 kPa, and transpiration per unit leaf areain response to increases in resource availability were associated with reductions in AL:As and consequently a minimal change in the water potential gradient from soil to leaf. Imgation and fertilization increased leaf area index similarly, from an average 1.16 in control stands to 1.45, but sapwood area was increased from 4.0 to 6.3 m ha-' by irrigation and from 3.7 to 6.7 m2 ha-' by fertilization. The balance between leaf area and sapwood area was important in understanding long-term hydraulic acclimation to resource availability and mechanisms controlling maximum productivity in Populus deltoides.

Samuelson, Lisa, J.; Stokes, Thomas, A.; Coleman, Mark, D.

2007-02-01

292

On the Influence of Topography Upon Scaling Characteristics of Soil Hydraulic Parameters  

NASA Astrophysics Data System (ADS)

One of the most important issues concerning studies into the hydrologic cycle and climate prediction today is the upscaling of soil hydraulic parameters in the unsaturated zone. Ecological phenomena occur differently, and due to different causes, at a wide range of scales. Efforts to model hydrologic processes and phenomena, with particular emphasis on those occurring in the unsaturated zone, are currently ongoing at various scales. Input data are required for these models at their representative scales. However, measurement of parameter data at all such required scales is impractical as it entails huge outlay of finances, time and effort. Inter-connections often exist between information across these scales. However, the exact mathematical or physical nature of these connections is generally a mystery. Over the past few decades, numerous efforts have been conducted to either understand and solve these mysteries, or to find a way around them to obtain effective parameters at multiple scales. Most upscaling efforts thus far have opted to ignore the effect of topography in their derivation of effective parameter values. This approach is reasonable as long as the coarser support dimensions are smaller than hill slopes. When upscaling fine scale hydraulic parameter data to hillslope scales and beyond, however, topography plays a bigger role and cannot be ignored. We present a study of the influence of topographic variations on the effective, upscaled soil hydraulic parameters under different hillslope configurations. Fine resolution parameters were upscaled using the Power Averaging Operator methodology which incorporates features from both mean-type and mode-type aggregation. Simulations of multiple hypothetical scenarios were conducted using the HYDRUS- 3D hydrologic modeling software to develop empirical relationships between the topography and the soil hydraulic parameters for matching hydrologic responses. These relationships may be assimilated into currently existing schemes to derive a more comprehensive algorithm to upscale fine resolution soil hydraulic parameters to any footprint dimension.

Jana, R. B.; Mohanty, B. P.

2008-12-01

293

Soil property effects on wind erosion of organic soils  

NASA Astrophysics Data System (ADS)

Histosols (also known as organic soils, mucks, or peats) are soils that are dominated by organic matter (OM > 20%) in half or more of the upper 80 cm. Forty two states have a total of 21 million ha of Histosols in the United States. These soils, when intensively cropped, are subject to wind erosion resulting in loss of crop productivity and degradation of soil, air, and water quality. Estimating wind erosion on Histosols has been determined by USDA-Natural Resources Conservation Service (NRCS) as a critical need for the Wind Erosion Prediction System (WEPS) model. WEPS has been developed to simulate wind erosion on agricultural land in the US, including soils with organic soil material surfaces. However, additional field measurements are needed to understand how soil properties vary among organic soils and to calibrate and validate estimates of wind erosion of organic soils using WEPS. Soil properties and sediment flux were measured in six soils with high organic contents located in Michigan and Florida, USA. Soil properties observed included organic matter content, particle density, dry mechanical stability, dry clod stability, wind erodible material, and geometric mean diameter of the surface aggregate distribution. A field portable wind tunnel was used to generate suspended sediment and dust from agricultural surfaces for soils ranging from 17% to 67% organic matter. The soils were tilled and rolled to provide a consolidated, friable surface. Dust emissions and saltation were measured using an isokinetic vertical slot sampler aspirated by a regulated suction source. Suspended dust was sampled using a Grimm optical particle size analyzer. Particle density of the saltation-sized material (>106 ?m) was inversely related to OM content and varied from 2.41 g cm-3 for the soil with the lowest OM content to 1.61 g cm-3 for the soil with highest OM content. Wind erodible material and the geometric mean diameter of the surface soil were inversely related to dry clod stability. The effect of soil properties on sediment flux varied among flux types. Saltation flux was adequately predicted with simple linear regression models. Dry mechanical stability was the best single soil property linearly related to saltation flux. Simple linear models with soil properties as independent variables were not well correlated with PM10E values (mass flux). A second order polynomial equation with OM as the independent variable was found to be most highly correlated with PM10E values. These results demonstrate that variations in sediment and dust emissions can be linked to soil properties using simple models based on one or more soil properties to estimate saltation mass flux and PM10E values from organic and organic-rich soils.

Zobeck, Ted M.; Baddock, Matthew; Scott Van Pelt, R.; Tatarko, John; Acosta-Martinez, Veronica

2013-09-01

294

Pharmaceuticals' sorptions relative to properties of thirteen different soils.  

PubMed

Transport of human and veterinary pharmaceuticals in soils and consequent ground-water contamination are influenced by many factors, including compound sorption on soil particles. Here we evaluate the sorption isotherms for 7 pharmaceuticals on 13 soils, described by Freundlich equations, and assess the impact of soil properties on various pharmaceuticals' sorption on soils. Sorption of ionizable pharmaceuticals was, in many cases, highly affected by soil pH. The sorption coefficient of sulfamethoxazole was negatively correlated to soil pH, and thus positively related to hydrolytic acidity and exchangeable acidity. Sorption coefficients for clindamycin and clarithromycin were positively related to soil pH and thus negatively related to hydrolytic acidity and exchangeable acidity, and positively related to base cation saturation. The sorption coefficients for the remaining pharmaceuticals (trimethoprim, metoprolol, atenolol, and carbamazepine) were also positively correlated with the base cation saturation and cation exchange capacity. Positive correlations between sorption coefficients and clay content were found for clindamycin, clarithromycin, atenolol, and metoprolol. Positive correlations between sorption coefficients and organic carbon content were obtained for trimethoprim and carbamazepine. Pedotransfer rules for predicting sorption coefficients of various pharmaceuticals included hydrolytic acidity (sulfamethoxazole), organic carbon content (trimethoprimand carbamazepine), base cation saturation (atenolol and metoprolol), exchangeable acidity and clay content (clindamycin), and soil active pH and clay content (clarithromycin). Pedotransfer rules, predicting the Freundlich sorption coefficients, could be applied for prediction of pharmaceutical mobility in soils with similar soil properties. Predicted sorption coefficients together with pharmaceutical half-lives and other imputes (e.g., soil-hydraulic, geological, hydro-geological, climatic) may be used for assessing potential ground-water contamination. PMID:25569579

Kodešová, Radka; Grabic, Roman; Ko?árek, Martin; Klement, Aleš; Golovko, Oksana; Fér, Miroslav; Nikodem, Antonín; Jakšík, Ond?ej

2015-04-01

295

Integrating models to simulate emergent behaviour: effects of organic matter on soil hydraulics in the ICZ-1D soil-vegetation model  

NASA Astrophysics Data System (ADS)

Soil develops as a result of interacting processes, many of which have been described in more or less detailed models. A key challenge in developing predictive models of soil function is to integrate processes that operate across a wide range of temporal and spatial scales. Many soil functions could be classified as "emergent", since they result from the interaction of subsystems. For example, soil organic matter (SOM) dynamics are commonly considered in relation to carbon storage, but can have profound effects on soil hydraulic properties that are conventionally considered to be static. Carbon fixed by plants enters the soil as litterfall, root turnover or via mycorrhizae. Plants need water and nutrients to grow, and an expanding root system provides access to a larger volume of soil for uptake of water and nutrients. Roots also provide organic exudates, such as oxalate, which increase nutrient availability. Carbon inputs are transformed at various rates into soil biota, CO2, and more persistent forms of organic matter. The SOM is partly taken up into soil aggregates of variable sizes, which slows down degradation. Water availability is an important factor as both plant growth and SOM degradation can be limited by shortage of water. Water flow is the main driver for transport of nutrients and other solutes. The flow of water in turn is influenced by the presence of SOM as this influences soil water retention and hydraulic conductivity. Towards the top of the unsaturated zone, bioturbation by the soil fauna transports both solid material and solutes. Weathering rates of minerals determine the availability of many nutrients and are in turn dependent on parameters such as pH, water content, CO2 pressure and oxalate concentration. Chemical reactions between solutes, dissolution and precipitation, and exchange on adsorption sites further influence solute concentrations. Within the FP7 SoilTrEC project, we developed a model that incorporates all of these processes, to explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.

Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

2014-05-01

296

Temperature dependence of unsaturated hydraulic conductivity of two soils.  

USGS Publications Warehouse

The temperature dependence of the soil water matric potential, surface tension, and diffuse double-layer thickness are discussed in terms of their possible interaction with the unsaturated conductivity values obtained. A case is presented for further study to isolate these temperature-sensitive parameters as well as additional parameters related to fluid flow path changes with temperature.-from Author

Constantz, J.

1982-01-01

297

Interrelations among the soil-water retention, hydraulic conductivity, and suction-stress characteristic curves  

USGS Publications Warehouse

The three fundamental constitutive relations that describe fluid flow, strength, and deformation behavior of variably saturated soils are the soil-water retention curve (SWRC), hydraulic conductivity function (HCF), and suction-stress characteristic curve (SSCC). Until recently, the interrelations among the SWRC, HCF, and SSCC have not been well established. This work sought experimental confirmation of interrelations among these three constitutive functions. Results taken from the literature for six soils and those obtained for 11 different soils were used. Using newly established analytical relations among the SWRC, HCF, and SSCC and these test results, the authors showed that these three constitutive relations can be defined by a common set of hydromechanical parameters. The coefficient of determination for air-entry pressures determined independently using hydraulic and mechanical methods is >0.99, >0.98 for the pore size parameter, and 0.94 for the residual degree of saturation. One practical implication is that one of any of the four experiments (axis-translation, hydraulic, shear-strength, or deformation) is sufficient to quantify all three constitutive relations.

Lu, Ning; Kaya, Murat; Godt, Jonathan W.

2014-01-01

298

Importance of internal hydraulic redistribution for prolonging the lifespan of roots in dry soil.  

PubMed

Redistribution of water within plants could mitigate drought stress of roots in zones of low soil moisture. Plant internal redistribution of water from regions of high soil moisture to roots in dry soil occurs during periods of low evaporative demand. Using minirhizotrons, we observed similar lifespans of roots in wet and dry soil for the grapevine 'Merlot' (Vitis vinifera) on the rootstock 101-14 Millardet de Gramanet (Vitis riparia x Vitis rupestris) in a Napa County, California vineyard. We hypothesized that hydraulic redistribution would prevent an appreciable reduction in root water potential and would contribute to prolonged root survivorship in dry soil zones. In a greenhouse study that tested this hypothesis, grapevine root systems were divided using split pots and were grown for 6 months. With thermocouple psychrometers, we measured water potentials of roots of the same plant in both wet and dry soil under three treatments: control (C), 24 h light + supplemental water (LW) and 24 h light only (L). Similar to the field results, roots in the dry side of split pots had similar survivorship as roots in the wet side of the split pots (P = 0.136) in the C treatment. In contrast, reduced root survivorship was directly associated with plants in which hydraulic redistribution was experimentally reduced by 24 h light. Dry-side roots of plants in the LW treatment lived half as long as the roots in the wet soil despite being provided with supplemental water (P < 0.0004). Additionally, pre-dawn water potentials of roots in dry soil under 24 h of illumination (L and LW) exhibited values nearly twice as negative as those of C plants (P = 0.034). Estimates of root membrane integrity using electrolyte leakage were consistent with patterns of root survivorship. Plants in which nocturnal hydraulic redistribution was reduced exhibited more than twice the amount of electrolyte leakage in dry roots compared to those in wet soil of the same plant. Our study demonstrates that besides a number of ecological advantages to protecting tissues against desiccation, internal hydraulic redistribution of water is a mechanism consistent with extended root survivorship in dry soils. PMID:18028280

Bauerle, T L; Richards, J H; Smart, D R; Eissenstat, D M

2008-02-01

299

Vital Soil: Function, Value and Properties.  

Technology Transfer Automated Retrieval System (TEKTRAN)

This article is a review of the book, Vital Soil: Function, Value and Properties. Soil vitality has been defined as the ability of soil ecosystems to stay in balance in a changing world. The soil environment and the life that it supports developed over centuries and millennia, but careless human ac...

300

SATURATED HYDRAULIC CONDUCTIVITY OF SEMI-ARID SOILS: COMBINED EFFECTS OF SALINITY, SODICITY AND RATE OF WETTING  

Technology Transfer Automated Retrieval System (TEKTRAN)

Combined effects of soil conditions (wetting rate), soil sodicity and salinity on soil saturated hydraulic conductivity (HC) have not been studied systematically and were the objective of our study. We examined the effects of (i) exchangeable sodium percentage (ESP, 1-20) and fast wetting (50 mm h-1...

301

In situ separation of root hydraulic redistribution of soil water from liquid and vapor transport.  

PubMed

Nocturnal increases in water potential (?) and water content (?) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution (HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the daily recovery in ? (??), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J(l)) and vapor (J(v)) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ?, ? and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that J (l) was irrelevant (<2E-05 mm h(-1) at 0-60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0-15 cm), driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal ? dynamics. Within the 15-35 cm layer, J(v) contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent layers contribute to ? in the 15-65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily recovery in ?. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total ecosystem water flux. PMID:21400193

Warren, Jeffrey M; Brooks, J Renée; Dragila, Maria I; Meinzer, Frederick C

2011-08-01

302

Estimation of field-scale soil hydraulic and dielectric parameters through joint inversion of GPR and hydrological data  

SciTech Connect

A method is described for the joint use of time-lapse ground-penetrating radar (GPR) travel times and hydrological data to estimate field-scale soil hydraulic parameters. We build upon previous work to take advantage of a wide range of cross-borehole GPR data acquisition configurations and to accommodate uncertainty in the petrophysical function, which relates soil porosity and water saturation to the effective dielectric constant. We first test the inversion methodology using synthetic examples of water injection in the vadose zone. Realistic errors in the petrophysical function result in substantial errors in soil hydraulic parameter estimates, but such errors are minimized through simultaneous estimation of petrophysical parameters. In some cases the use of a simplified GPR simulator causes systematic errors in calculated travel times; simultaneous estimation of a single correction parameter sufficiently reduces the impact of these errors. We also apply the method to the U.S. Department of Energy (DOE) Hanford site in Washington, where time-lapse GPR and neutron probe (NP) data sets were collected during an infiltration experiment. We find that inclusion of GPR data in the inversion procedure allows for improved predictions of water content, compared to predictions made using NP data alone. These examples demonstrate that the complimentary information contained in geophysical and hydrological data can be successfully extracted in a joint inversion approach. Moreover, since the generation of tomograms is not required, the amount of GPR data required for analyses is relatively low, and difficulties inherent to tomography methods are alleviated. Finally, the approach provides a means to capture the properties and system state of heterogeneous soil, both of which are crucial for assessing and predicting subsurface flow and contaminant transport.

Kowalsky, M B.; Finsterle, Stefan A.; Peterson, John; Hubbard, Susan; Rubin, Yoram; Majer, Ernest L.; Ward, Andy L.; Gee, Glendon W.

2005-12-01

303

Trade-offs between xylem hydraulic properties, wood anatomy and yield in Populus.  

PubMed

Trees face the dilemma that achieving high plant productivity is accompanied by a risk of drought-induced hydraulic failure due to a trade-off in the trees' vascular system between hydraulic efficiency and safety. By investigating the xylem anatomy of branches and coarse roots, and measuring branch axial hydraulic conductivity and vulnerability to cavitation in 4-year-old field-grown aspen plants of five demes (Populus tremula L. and Populus tremuloides Michx.) differing in growth rate, we tested the hypotheses that (i) demes differ in wood anatomical and hydraulic properties, (ii) hydraulic efficiency and safety are related to xylem anatomical traits, and (iii) aboveground productivity and hydraulic efficiency are negatively correlated to cavitation resistance. Significant deme differences existed in seven of the nine investigated branch-related anatomical and hydraulic traits but only in one of the four coarse-root-related anatomical traits; this likely is a consequence of high intra-plant variation in root morphology and the occurrence of a few 'high-conductivity roots'. Growth rate was positively related to branch hydraulic efficiency (xylem-specific conductivity) but not to cavitation resistance; this indicates that no marked trade-off exists between cavitation resistance and growth. Both branch hydraulic safety and hydraulic efficiency significantly depended on vessel size and were related to the genetic distance between the demes, while the xylem pressure causing 88% loss of hydraulic conductivity (P88 value) was more closely related to hydraulic efficiency than the commonly used P50 value. Deme-specific variation in the pit membrane structure may explain why vessel size was not directly linked to growth rate. We conclude that branch hydraulic efficiency is an important growth-influencing trait in aspen, while the assumed trade-off between productivity and hydraulic safety is weak. PMID:25009155

Hajek, Peter; Leuschner, Christoph; Hertel, Dietrich; Delzon, Sylvain; Schuldt, Bernhard

2014-07-01

304

Transfer of Physical and Hydraulic Properties Databases to the Hanford Environmental Information System - PNNL Remediation Decision Support Project, Task 1, Activity 6  

SciTech Connect

This report documents the requirements for transferring physical and hydraulic property data compiled by PNNL into the Hanford Environmental Information System (HEIS). The Remediation Decision Support (RDS) Project is managed by Pacific Northwest National Laboratory (PNNL) to support Hanford Site waste management and remedial action decisions by the U.S. Department of Energy and one of their current site contractors - CH2M-Hill Plateau Remediation Company (CHPRC). The objective of Task 1, Activity 6 of the RDS project is to compile all available physical and hydraulic property data for sediments from the Hanford Site, to port these data into the Hanford Environmental Information System (HEIS), and to make the data web-accessible to anyone on the Hanford Local Area Network via the so-called Virtual Library.1 These physical and hydraulic property data are used to estimate parameters for analytical and numerical flow and transport models that are used for site risk assessments and evaluation of remedial action alternatives. In past years efforts were made by RDS project staff to compile all available physical and hydraulic property data for Hanford sediments and to transfer these data into SoilVision{reg_sign}, a commercial geotechnical software package designed for storing, analyzing, and manipulating soils data. Although SoilVision{reg_sign} has proven to be useful, its access and use restrictions have been recognized as a limitation to the effective use of the physical and hydraulic property databases by the broader group of potential users involved in Hanford waste site issues. In order to make these data more widely available and useable, a decision was made to port them to HEIS and to make them web-accessible via a Virtual Library module. In FY08 the original objectives of this activity on the RDS project were to: (1) ensure traceability and defensibility of all physical and hydraulic property data currently residing in the SoilVision{reg_sign} database maintained by PNNL, (2) transfer the physical and hydraulic property data from the Microsoft Access database files used by SoilVision{reg_sign} into HEIS, which is currently being maintained by CHRPC, (3) develop a Virtual Library module for accessing these data from HEIS, and (4) write a User's Manual for the Virtual Library module. The intent of these activities is to make the available physical and hydraulic property data more readily accessible and useable by technical staff and operable unit managers involved in waste site assessments and remedial action decisions for Hanford. In FY08 communications were established between PNNL and staff from Fluor-Hanford Co. (who formerly managed HEIS) to outline the design of a Virtual Library module that could be used to access the physical and hydraulic property data that are to be transferred into HEIS. Data dictionaries used by SoilVision{reg_sign} were also provided to Fluor-Hanford personnel (who are now with CHPRC). During ongoing work to ensure traceability and defensibility of all physical and hydraulic property data that currently reside in the SoilVision{reg_sign} database, it was recognized that further work would be required in this effort before the data were actually ported into HEIS. Therefore work on the Virtual Library module development and an accompanying User's Guide was deferred until an unspecified later date. In FY09 efforts have continued to verify the traceability and defensibility of the physical and hydraulic property datasets that are currently being maintained by PNNL. Although this is a work in progress, several of these datasets should be ready for transfer to HEIS in the very near future. This document outlines a plan for the migration of these datasets into HEIS.

Rockhold, Mark L.; Middleton, Lisa A.

2009-03-31

305

Laboratory evaluation of the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils  

E-print Network

This thesis evaluates the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils. A laboratory program compares hydraulic conductivity measurements made ...

Adams, Amy Lynn

2011-01-01

306

Measuring hydraulic properties of peat through inversion of pumping test data  

NASA Astrophysics Data System (ADS)

The hydraulic conductivity of peat affects flow patterns and rates that influence biogenic gas dynamics, vegetation patterns, and biomass accumulation rates in peatland ecosystems. Biogenic gasses, such as methane, trapped within the peat complicate this relationship by occluding pore space and changing the hydraulic conductivity of the peat. We have completed pumping tests at two locations, a forested bog and open lawn, within the Glacial Lake Agassiz Peatlands to characterize the hydraulic conductivity in this peatland. Traditional analysis of pumping tests provide bulk estimates of hydraulic conductivity. In contrast, the spatial distribution of hydraulic conductivity in our study area have been estimated using regularized inversion to calibrate a computer simulation with pumping test data. Computer models of pumping tests were developed using FiPy, a finite-volume modeling library. Parameter estimation software (PEST) was used to repeatedly run simulations while adjusting hydraulic properties assigned to cells within the computer model. Results from the regularized inversion of the pumping test data indicate that the hydraulic conductivity of the deeper peat at the bog and lawn sites typically ranged from 10-6 to 10-5 and 10-3 to 10-4 m/sec, respectively. Anomalous hydraulic conductivity bands were present in the deep peat and hydraulic conductivity did not systematically increase with depth. Lenses of low hydraulic conductivity peat are present in out calibrated models and may represent areas of trapped biogenic gas, but these lenses lie in regions of our computer model that are poorly constrained by the regularized inversion.

Rhoades, J.; Reeve, A. S.

2009-05-01

307

A Catalog of Vadose Zone Hydraulic Properties for the Hanford Site  

SciTech Connect

To predict contaminant release to the groundwater, it is necessary to understand the hydraulic properties of the material between the release point and the water table. Measurements of the hydraulic properties of the Hanford unsaturated sediments that buffer the water table are available from many areas of the site; however, the documentation is not well cataloged nor is it easily accessible. The purpose of this report is to identify what data is available for characterization of the unsaturated hydraulic properties at Hanford and Where these data can be found.

Freeman, Eugene J.; Khaleel, Raziuddin; Heller, Paula R.

2002-09-30

308

Quantifying the impact of livestock grazing on soil physical properties  

NASA Astrophysics Data System (ADS)

Livestock grazing is considered to have a noticeable influence on soil properties, when pedocompaction / soil pore reduction induced either by cattle or sheeps may curtail water residence time and accelerate the beginning and volume of overland flow. However, direct measurements of soil physical parameters and their changes under different pastoral management are seldom reported in central European conditions. Knowledge about these alterations are indispensable for setting the proper, soil and water conservative grazing management in the view of increasing areas of pastures, not only in the Czech Republic. Impact of cattle grazing on changes of soil properties was studied in three experimental upland catchments in the Czech Republic, differing in soil characteristics and grazing management. Values of soil saturated hydraulic conductivity (Ks), assessed three times a year in-situ during 2012 - 2013 with pressure infiltrometers, were compared for grazed and ungrazed cambisols, pseudogleys and gleysols, for grazing intensity ranging from 0.5 to 2 Livestock units / ha. Soil bulk density (BD) and macroporosity (MP) were determined before and after grazing season every year with ring 100 cm3 steel cyllinders. These parameters were measured also on heavily treaded plots by cattle - hotspots - in each catchment. Ks values on grazed plots were significantly lower (on average by 39 - 66 %) than on ungrazed sites, BD values were reduced on average by 15 % and MP values were lower roughly about 22 % on grazed plots. Ks values on hotspots were lower by 50 - 90 %, BD values by 5 - 18 % and MP values by 8 - 28 % comparing to the rest of grazed areas. Decrease of soil infiltration capacity was influenced by grazing intensity and soil characteristics. The greatest reductions concerning infiltration capacity were manifested in soils being periodically waterlogged (either by surface or by groundwater). A profound influence on the infiltration process was revealed in pasture soils rich on biotite, which together with clay minerals and the pseudogleyization process created an almost unpermeable layer, somewhere already in 25 cm below the surface. Off the grazing season, soils were recovering and in spring reached nearly similar properties, except for the hotspots, concerning the infiltration ability, as ungrazed soils. This research was supported by Czech Ministry of Agriculture, grant no. QI111C034.

Fu?ík, Petr; Zají?ek, Antonín; Holubík, Ond?ej

2014-05-01

309

An aerodynamic approach in soil hydraulic conductivity estimation for investigating soil erosion degree  

NASA Astrophysics Data System (ADS)

We propose a new method for determining the degree of erosion for zonal soils of the East European Plain. This new approach uses soil porosity and filtration to determine a coefficient of aerodynamic similarity. We evaluated the degree of soil erosion on ranges of the major zonal soils of the eastern part of European Russia by applying this new method. Based on these data, we developed a diagnostic scale to determine the extent of soil erosion in this area.

Sergey, V.; Vyacheslav, S.

2015-03-01

310

Communicating soil property variability in heterogeneous soil mapping units  

NASA Astrophysics Data System (ADS)

Soil properties and classes can change over very short distances. For the purpose of scale, clarity and field sampling density, soil maps in England and Wales commonly use mapping units which are groupings of taxonomic soil series, commonly found in association with each other in the landscape. These mixed units (Soil Associations), typically contain between 3 and 7 soil series with physical or chemical properties, which can vary across the mapping unit, or may be relatively homogeneous. The degree of variation is not constant between soil properties, for instance, pH may be relatively constant, but volumetric shrinkage potential may be highly variable. Over the past ten years, the number of users of GIS soil property maps has dramatically increased, yet the vast majority of these users do not have a soil or geoscience background. They are instead practitioners in specific industries. As a result, new techniques have been developed to communicate the variation in maps of soil properties to a non-expert audience. GIS data structures allow more flexibility in the reporting of uncertainty or variation in soil mapping units than paper-based maps. Some properties are categorical, others continuous. In England and Wales, the national and regional memberships of soil associations are available, with areal percentages of the comprising soil series being estimated for each association by a combination of expert judgment and field observations. Membership at a local scale can vary considerably from the national average. When summarizing across a whole map unit, for continuous variables, rarely is it appropriate to provide a mean value, or even a weighted average based on membership percentage of the association. Such approaches can make a nonsense of wide-ranging data. For instance a soil association comprising soil series with highly different percentages of sand, silt and clay may result in a 'loamy' mean soil texture which is not reflective of any of the comprising soils. For categorical data, the choice of the property of the spatially dominant soil series may provide the 'most likely' answer, but this may not be the most helpful answer for the end user. Additionally, when aggregating to select the dominant property or class, rather than the dominant taxonomic soil series, it is not uncommon for the 'dominant' class to change. One example of our new approach is to communicate the attributes of the soil associations on the basis of the worst-case scenario at various confidence levels, based on the percentage of the soil series of the association. As an example, when soil maps are used to help underwriters understand the vulnerability of an area to soil related subsidence, the maximum subsidence rating can be chosen from soils which comprise, for example, more than 5% or more than 30% of the soil association in question. Developing an understanding of end-user requirements allows optimization of soil datasets to suit their needs, and encourages engagement between soil scientists and industry.

Farewell, Timothy

2014-05-01

311

Physical and hydraulic characteristics of bentonite-amended soil from Area 5, Nevada Test Site  

SciTech Connect

Radioactive waste requires significant isolation from the biosphere. Shallow land burial using low-permeability covers are often used to prevent the release of impounded material. This report details the characterization of a soil mixture intended for use as the low-permeability component of a radioactive waste disposal site. The addition of 6.5 percent bentonite to the sandy soils of the site reduced the value of saturated hydraulic conductivity (K{sub s}) by more than two orders of magnitude to 7.6 {times} 10{minus}{sup 8} cm/sec. Characterization of the soil mixture included measurements of grain density, grain size distribution, compaction, porosity, dry bulk density, shear strength, desiccation shrinkage, K{sub s}, vapor conductivity, air permeability, the characteristic water retention function, and unsaturated hydraulic conductivity by both experimental and numerical estimation methods. The ability of the soil layer to limit infiltration in a simulated application was estimated in a one-dimensional model of a landfill cover.

Albright, W. [University and Community Coll. System of Nevada, Reno, NV (United States). Water Resources Center, Desert Research Institute

1995-08-01

312

High-order averaging method of hydraulic conductivity for accurate soil moisture modeling  

NASA Astrophysics Data System (ADS)

Richards' equation (RE) is the most common mathematical expression for soil water movement in a porous medium. Despite advancements in numerical schemes and high-performance computing, the requirements of iterative computations and fine grids hinder further extension of the RE to multi-dimensional and large-scale applications. Averaging methods of hydraulic conductivity have been known to be one of the significant factors affecting the accuracy of numerical solutions of the RE, especially when coarse grids are used. In this study, we developed a high-order averaging method of hydraulic conductivity for accurate numerical modeling of the RE, which has a straightforward formula regardless of the soil conditions and produces high simulation accuracy when used on coarse grids. The developed method is based on the high-order upwind scheme, which is widely used for hyperbolic partial differential equations within a finite volume framework in order to prevent numerical oscillations near a discontinuity while preserving high-order accuracy. Numerical simulations of several one- and two-dimensional cases performed in the study indicate that the proposed method outperforms existing simple averaging methods and is also superior, or at least equivalent, to complex averaging methods over a wide range of soil textures, especially on coarse grids. In addition, the proposed method is straightforwardly extended to nonorthogonal grids by being combined with the coordinate transformation method and the extension is verified through multi-dimensional test cases as well as tests on a heterogeneous soil domain.

An, Hyunuk; Noh, Seong Jin

2014-08-01

313

Applicability of Different Hydraulic Parameters to Describe Soil Detachment in Eroding Rills  

PubMed Central

This study presents the comparison of experimental results with assumptions used in numerical models. The aim of the field experiments is to test the linear relationship between different hydraulic parameters and soil detachment. For example correlations between shear stress, unit length shear force, stream power, unit stream power and effective stream power and the detachment rate does not reveal a single parameter which consistently displays the best correlation. More importantly, the best fit does not only vary from one experiment to another, but even between distinct measurement points. Different processes in rill erosion are responsible for the changing correlations. However, not all these procedures are considered in soil erosion models. Hence, hydraulic parameters alone are not sufficient to predict detachment rates. They predict the fluvial incising in the rill's bottom, but the main sediment sources are not considered sufficiently in its equations. The results of this study show that there is still a lack of understanding of the physical processes underlying soil erosion. Exerted forces, soil stability and its expression, the abstraction of the detachment and transport processes in shallow flowing water remain still subject of unclear description and dependence. PMID:23717669

Wirtz, Stefan; Seeger, Manuel; Zell, Andreas; Wagner, Christian; Wagner, Jean-Frank; Ries, Johannes B.

2013-01-01

314

Measurement of soil and rock fractural hydraulic conductivities using falling head infiltration experiment of single-ring permeameter  

NASA Astrophysics Data System (ADS)

Southwest China Karst is a fragile area for ecological system because of thin soil and underlying rock fracures. Soil and rock fractural hydraulic conductivities in this area determine infiltration, runoff and water retaining in soil and rock fractures for plant utilization. Determination of soil and rock fractural hydraulic conductivities is very tough due to strong heterogeneous. In this paper, we designed a single-ring permeameter to measure the hydraulic conductivities based on falling head infiltration experiment. The experiments were conducted in two karst areas in southwest China: a hillslope in Huanjiang County, northwest Guangxi for measuring soil hydraulic conductivities and a profile at the small catchment of Chenqi in the Puding basin of Guizhou for measuring fractural hydraulic conductivities. The results show that surface soil hydraulic conductivity is 2.386×10-4 m/s, much larger than 2.004×10-5 m/s for the soil at 30cm depth. Soil hydraulic conductivities are generally increased from the bottom to the top along the hillslope, and this increase is particularly significant for the soil at 30cm depth. The fractural hydraulic conductivities were determined for the limestone profile with three fractures crossing in vertical and horizontal directions. The effective fractural aperture was determined according to calibration of water head variations of the ponded water in the single ring permeameter, which can be simulated by a numerical model based on Navier-Stokes equations and measured with an automatic observation equipment. The hydraulic conductivities were then estimated in terms of the cubic law equation. The estimated effective fractural aperture is 0.25mm for the horizontal fracture, and 0.25 and 0.5mm for the two vertical fractures crossing the horizontal in the right and left sides, respectively. The corresponding hydraulic conductivity is 0.051 m/s for the horizontal fracture and 0.051 and 0.204m/s for the two vertical fractures in the right and left sides, respectively. Acknowledgments This research was supported by National Natural Science Foundation of China (No. 40930635, and 51079038)

Chen, X.; Zhang, Z. C.; Shi, P.; Cheng, Q. B.

2012-04-01

315

Relationship of catchment topography and soil hydraulic characteristics to lake alkalinity in the northeastern United States  

SciTech Connect

The authors undertook the task of determining whether base flow alkalinity of surface waters in the northeastern United States is related to indices of soil contact time and flow path partitioning that are derived from topographic and soils information. The influence of topography and soils on catchment hydrology has been incorporated previously in the variable source area model TOPMODEL as the relative frequency distribution of ln(a/Kb tan B), where ln is the Naperian logarithm, a is the area drained per unit contour, K is the saturated hydraulic conductivity, b is the soil depth, and tan B is the slope. Using digital elevation and soil survey data, the authors calculated the ln (a/Kb tan B) distribution for 145 catchments. Indices of flow path partitioning and soil contact time were derived from the ln(a/Kb tan B) distributions and compared to measurements of alkalinity in lakes to which the catchments drain. They found that alkalinity was, in general, positively correlated with the index of soil contact time, whereas the correlation between alkalinity and the flow path partitioning index was weak at best. A portion of the correlation between the soil contact time index and alkalinity was attributable to covariation with soil base saturation and cation exchange capacity, while another portion was found to be independent of these factors. Although their results indicate that catchments with long soil contact time indices are most likely to produce high alkalinity base flow, a sensitivity analysis of TOPMODEL suggests that surface waters of these same watersheds may be susceptible to alkalinity depressions during storm events, due to the role of flow paths.

Wolock, D.M.; Hornberger, G.M.; Beven, K.J.; Campbell, W.G.

1989-01-01

316

Influence of hydraulic hysteresis on the mechanical behavior of unsaturated soils and interfaces  

NASA Astrophysics Data System (ADS)

Unsaturated soils are commonly widespread around the world, especially at shallow depths from the surface. The mechanical behavior of this near surface soil is influenced by the seasonal variations such as rainfall or drought, which in turn may have a detrimental effect on many structures (e.g. retaining walls, shallow foundations, mechanically stabilized earth walls, soil slopes, and pavements) in contact with it. Thus, in order to better understand this behavior, it is crucial to study the complex relationship between soil moisture content and matric suction (a stress state variable defined as pore air pressure minus pore water pressure) known as the Soil Water Characteristic Curve (SWCC). In addition, the influence of hydraulic hysteresis on the behavior of unsaturated soils, soil-structure interaction (i.e. rough and smooth steel interfaces, soil-geotextile interfaces) and pavement subgrade (depicted herein mainly by resilient modulus, Mr) was also studied. To this end, suction-controlled direct shear tests were performed on soils, rough and smooth steel interfaces and geotextile interface under drying (D) and wetting after drying (DW). The shearing behavior is examined in terms of the two stress state variables, matric suction and net normal stress. Results along the D and DW paths indicated that peak shear strength increased with suction and net normal stress; while in general, the post peak shear strength was not influenced by suction for rough interfaces and no consistent trend was observed for soils and soil-geotextiles interfaces. Contrary to saturated soils, results during shearing at higher suction values (i.e. 25 kPa and above) showed a decrease in water content eventhough the sample exhibited dilation. A behavior postulated to be related to disruption of menisci and/or non-uniformity of pore size which results in an increase in localized pore water pressures. Interestingly, wetting after drying (DW) test results showed higher peak and post peak shear strength than that of the drying (D) tests. This is believed to be the result of many factors such as: (1) cyclic suction stress loading, (2) water content (less on wetting than drying), and (3) type of soil. The cyclic suction loading may have induced irrecoverable plastic strains, resulting in stiffer samples for wetting tests as compared to drying. Additionally, water may be acting as a lubricant and thus resulting in lower shear strength for test samples D with higher water contents than DW samples. Furthermore, various shear strength models were investigated for their applicability to the experimental data. Models were proposed for the prediction of shear strength with suction based on the SWCC. The models are able to predict the shear strength of unsaturated soil and interfaces due to drying and wetting (i.e. hydraulic hysteresis) by relating directly to the SWCC. The proposed models were used and partly validated by predicting different test results from the literature. In addition, an existing elastoplastic constitutive model was investigated and validated by comparing the predicted and experimental (stress-displacement, volume change behavior) results obtained from rough and geotextile interface tests. This study also explores the effect of hydraulic hysteresis on the resilient modulus (Mr) of subgrade soils. Suction-controlled Mr tests were performed on compacted samples along the primary drying, wetting, secondary drying and wetting paths. Two test types were performed to check the effect of cyclic deviatoric stress loading on the results. First, M r tests were performed on the same sample at each suction (i.e. 25, 50, 75, 100 kPa) value along all the paths (drying, wetting etc.). A relationship between resilient modulus (Mr) and matric suction was obtained and identified as the resilient modulus characteristic curve (MRCC). MRCC results indicated that Mr increased with suction along the drying curve. On the other hand, results on the primary wetting indicated higher Mr than that of the primary drying and the secondary drying. The second type of test

Khoury, Charbel N.

317

Lunar soil science. Physicomechanical properties of lunar soils  

Microsoft Academic Search

Current (1975) views of the genesis, structure and properties of lunar soils based on astronomical and radiophysical studies of the moon are presented. Lunar research from orbital spacecraft is discussed, and techniques and equipment employed to investigate lunar soils in soft-landed lunar stations are described in detail. A separate section is devoted to examinations of the first lunar rock samples

I. I. Cherkasov; V. V. Shvarev; A. Y. Ishlinskii

1975-01-01

318

Effect of rock fragment addition on hydro-dispersive properties of compacted soils  

NASA Astrophysics Data System (ADS)

Compaction of agricultural soils is an increasingly challenging problem for crop production and environment. Mechanization of agricultural practices is one of the main factors inducing degradation of soil structure, especially in fragile soils with little organic matter and low shrinking-swelling capacity. Moreover, rock picking from stony soils is a routine practice to avoid tillage problems in some agricultural productions, but stone removal can significantly increase soil compaction, which lowers water infiltration rates and increases surface runoff and soil erosion. The practice of crushing and returning smaller rock fragments to the field could reduce the above problems. The aim of this work was to test the addition of rock fragments as practice to restore soil physical quality of not-stony soils susceptible to compaction. We carried out a lab experiment mixing five different volume concentrations (5%, 10%, 15%, 25% and 35%) of 4-8mm rock fragments with an Alfisol and an Entisol, showing compact structure and water stagnation problems in field. The repacked samples have undergone nine wet/dry cycles in order to induce soil structure formation and its stabilization. Bulk density, porosity and soil hydraulic properties and hydro-dispersive characteristics were measured. Soil hydraulic properties, namely water retention and hydraulic conductivity, were inferred from an infiltration experiment performed by a tension infiltrometer disc coupled with an inverse parameter estimation method; hydro-dispersive characteristics were performed from a tracer inflow-outflow experiment conducted in unsaturated condition, followed by the analysis of the breakthrough curve. Soil image analysis was used to enhance parameterization of the hydrological models near saturation. Preliminary results showed that bulk density significantly changed only after addition of 35% of rock fragments and a good physical restoration was reached at 15% volume concentration in Entisol and at 25% in Alfisol where hydro-dispersive characteristics strongly changed.

Gargiulo, Laura; Mele, Giacomo; Coppola, Antonio; De Mascellis, Roberto; Di Matteo, Bruno; Terribile, Fabio; Basile, Angelo

2014-05-01

319

SOIL PHYSICAL PROPERTIES AND CROP PRODUCTIVITY OF AN ERODED SOIL AMENDED WITH CATTLE MANURE  

Microsoft Academic Search

Erosion changes soil properties, especially physical properties, mainly because it removes surface soil rich in organic materials and exposes lower soil layers. In 1988, a study was established to determine the effects of soil erosion and long-term manure applications on selected soil phys­ ical properties and corn (Zea mays L.) production. After 10 years of an­ nual manure applications, soil

Francisco J. Arriaga; Birl Lowery

2003-01-01

320

Combining multi-objective optimization and bayesian model averaging to calibrate forecast ensembles of soil hydraulic models  

SciTech Connect

Most studies in vadose zone hydrology use a single conceptual model for predictive inference and analysis. Focusing on the outcome of a single model is prone to statistical bias and underestimation of uncertainty. In this study, we combine multi-objective optimization and Bayesian Model Averaging (BMA) to generate forecast ensembles of soil hydraulic models. To illustrate our method, we use observed tensiometric pressure head data at three different depths in a layered vadose zone of volcanic origin in New Zealand. A set of seven different soil hydraulic models is calibrated using a multi-objective formulation with three different objective functions that each measure the mismatch between observed and predicted soil water pressure head at one specific depth. The Pareto solution space corresponding to these three objectives is estimated with AMALGAM, and used to generate four different model ensembles. These ensembles are post-processed with BMA and used for predictive analysis and uncertainty estimation. Our most important conclusions for the vadose zone under consideration are: (1) the mean BMA forecast exhibits similar predictive capabilities as the best individual performing soil hydraulic model, (2) the size of the BMA uncertainty ranges increase with increasing depth and dryness in the soil profile, (3) the best performing ensemble corresponds to the compromise (or balanced) solution of the three-objective Pareto surface, and (4) the combined multi-objective optimization and BMA framework proposed in this paper is very useful to generate forecast ensembles of soil hydraulic models.

Vrugt, Jasper A [Los Alamos National Laboratory; Wohling, Thomas [NON LANL

2008-01-01

321

Peat hydraulic conductivity in different landuses  

NASA Astrophysics Data System (ADS)

Information on hydraulic conductivity and water retention properties of peatlands is needed, e.g., for modelling hydrology and soil carbon balance of peat soils. Ability to model the behaviour of peat soils, especially those drained for agricultural use, is important as cultivated peatlands act as a major source of CO2 and N2O emissions in Nordic countries. Peat soil hydraulic conductivity and water retention properties vary greatly, and their relationship to soil depth and degree of decomposition is not straightforward. The aim of this study was to produce new information about peat physical properties in different land uses and the relationship between peat soil hydraulic conductivity and variables such as soil porosity and degree of humification. Peat hydraulic conductivity was measured in situ with infiltrometer (direct push piezometer) in six study sites (two pristine bogs, two sites drained for forestry, a cultivated peat land site and a peat extraction site). Measurements were made in several depths according to soil profile. To examine relationship of soil properties and the hydraulic conductivity, undisturbed peat cores of known volume and also disturbed peat samples were collected from the study sites for determination of von Post humification factor, ash content, porosity and bulk density. Surface layer of the agricultural site had high ash content and bulk density and low porosity compared to the soil beneath it and the soil in other study sites. This was due to added sand and compaction by agricultural practice. Bog, in contrast, had very low bulk density and high porosity. Results show a great variation in hydraulic conductivity within the study sites even when the observations were in the same soil layer. Hydraulic conductivity was lowest in the peat extraction site and the agricultural site, and had higher correlation with study site (= landuse) and the measured layer than with soil porosity.

Mustamo, Pirkko; Hyvärinen, Maarit; Ronkanen, Anna-Kaisa; Kløve, Bjørn

2013-04-01

322

Field-Obtained Soil Water Characteristic Curves and Hydraulic Conductivity Functions  

NASA Astrophysics Data System (ADS)

A compacted clay liner (test pad) was constructed and instrumented with volumetric water content and soil matric potential sensors to determine soil water characteristic curves (SWCC) and hydraulic conductivity (k) functions. Specifically, the compacted clay liner was subjected to an infiltration cycle during a sealed double ring infiltrometer (SDRI) test followed by a drying cycle. After the drying cycle, Shelby tube samples were collected from the compacted clay liner and flexible wall permeability (FWP) tests were conducted on sub-samples to determine the saturated hydraulic conductivity. Moreover, two computer programs (RETC and UNSAT-H) were utilized to model the SWCCs and k-functions of the soil based on obtained measurements including the volumetric water content, the soil matric potential, and the saturated hudraulic conductivity (ks). Results obtained from the RETC program (s, r, ?, n and ks) were ingested into UNSAT-H program to calculate the movement of water (rate and location) through the compacted clay liner. Although a linear wetting front (location of water infiltration as a function of time) is typically utilized for SDRI calculations, the use of a hyperbolic wetting front is recommended as a hyperbolic wetting front was modeled from the testing results. The suggested shape of the wetting front is associated with utilization of the desorption SWCC instead of the sorption SWCC and with relatively high values of ks (average value of 7.2E-7 cm/sec) were measured in the FWP tests while relatively low values of ks (average value of 1.2E-7 cm/sec) were measured in the SDRI test.

Elvis, Ishimwe

323

High-quality unsaturated zone hydraulic property data for hydrologic applications  

USGS Publications Warehouse

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

Perkins, K.; Nimmo, J.

2009-01-01

324

A harmonized vocabulary for soil observed properties  

NASA Astrophysics Data System (ADS)

Interoperability of soil data depends on agreements concerning models, schemas and vocabularies. However, observed property terms are often defined during different activities and projects in isolation of one another, resulting in data that has the same scope being represented with different terms, using different formats and formalisms, and published in various access methods. Significantly, many soil property vocabularies conflate multiple concepts in a single term, e.g. quantity kind, units of measure, substance being observed, and procedure. Effectively, this bundles separate information elements into a single slot. We have developed a vocabulary for observed soil properties by adopting and extending a previously defined water quality vocabulary. The observed property model separates the information elements, based on the Open Geospatial Consortium (OGC) Observations & Measurements model and extending the NASA/TopQuadrant 'Quantities, Units, Dimensions and Types' (QUDT) ontology. The imported water quality vocabulary is formalized using the Web Ontology Language (OWL). Key elements are defined as sub-classes or sub-properties of standard Simple Knowledge Organization System (SKOS) elements, allowing use of standard vocabulary interfaces. For the soil observed property vocabulary, terms from QUDT and water quality are used where possible. These are supplemented with additional unit of measure (Unit), observed property (ScaledQuantityKind) and substance being observed (SubstanceOrTaxon) vocabulary entries required for the soil properties. The vocabulary terms have been extracted from the Australian Soil and Land Survey Field Handbook and Australian Soil Information Transfer and Evaluation System (SITES) vocabularies. The vocabulary links any chemical substances to items from the Chemical Entities of Biological Interest (ChEBI) ontology. By formalizing the model for observable properties, and clearly labelling the separate elements, soil property observations may be more easily mapped to the OGC Observations & Measurements model for cross-domain applications.

Simons, Bruce; Wilson, Peter; Cox, Simon; Vleeshouer, Jamie

2014-05-01

325

Hydraulic properties of coarsely and finely ground woodchips  

NASA Astrophysics Data System (ADS)

Recent evidence suggests that leachate from woodchips stockpiled at recycling facilities could negatively impact water quality. Models that can be used to simulate water movement/leachate production require information on water retention and hydraulic conductivity functions of the stockpiled material. The objectives of this study were to (1) determine water retention and hydraulic conductivity functions of woodchips with particle size distributions (PSDs) representative of field stockpiled material by modeling multistep outflow and (2) assess the performance of three pore structure models for their ability to simulate outflow. Six samples with contrasting PSDs were assessed in duplicate. Samples were packed in cylindrical columns (15.3 cm high, 12.1 cm wide) to measure saturated hydraulic conductivity (Ks), cumulative outflow and water content at equilibrium with pressure potentials of -2, -10 and -40 cm. Water retention at pressure potentials between -200 and -10,000 cm were obtained using pressure plate extractors and used to supplement data from the outflow experiment. Hydraulic parameters of the pore models were derived from these measurements using HYDRUS-1D run by DREAM(ZS). Ks was independent of PSD with values between 55 and 80 cm/h. Cumulative outflow at each pressure potential was correlated with the PSD geometric mean diameters, and was best predicted by a model having two interacting pore domains, each with separate hydraulic conductivity and water retention functions (DPeM). Unsaturated conductivities were predicted to drop on an average to 0.24 cm/h at -10 cm and 3 × 10-3 cm/h at -50 cm for the DPeM model, suggesting that water would move slowly through stockpiles except during intense rainfalls.

Subroy, Vandana; Giménez, Daniel; Qin, Mingming; Krogmann, Uta; Strom, Peter F.; Miskewitz, Robert J.

2014-09-01

326

Soil properties and water regime of reclaimed surface dumps in the North Bohemian brown-coal region--a field study.  

PubMed

This paper attempts to characterise the water regime of reclaimed surface dumps in connection with their soil physical properties. The results of a research project based on field measurements of moisture content and hydraulic conductivity, supported by analyses of undisturbed soil samples, led to recommendations regarding technological procedures for such dumps. A dielectric soil moisture meter, in an improved version, was successfully used for field monitoring and further evaluation of moisture content. Hydraulic conductivity was also measured in the field (by repeated borehole infiltration) using the Guelph permeameter method. Laplace-Gardner analysis was used for evaluating the field saturated hydraulic conductivity results. PMID:11220179

Kuráz, V

2001-01-01

327

A hydraulic model is compatible with rapid changes in leaf elongation under fluctuating evaporative demand and soil water status.  

PubMed

Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1-2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture. PMID:24420931

Caldeira, Cecilio F; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

2014-04-01

328

Experimental and numerical study of infiltration into arid soils with contrasting physical and textural properties  

NASA Astrophysics Data System (ADS)

Dye infiltration tests were performed in the arid environments of the Ti Tree catchment, Central Australia. This area has a mean annual precipitation of 300 mm and is further known to have infrequent intensive rainfall events linked to short-term flooding. The mechanisms of groundwater recharge in these arid environments are generally unknown. The upper 1-2 m of soil play an important role in water redistribution with preferential flow often contributing to inhomogeneous moisture storage, soil water flow and groundwater recharge. Reducing uncertainty in recharge estimation thus requires a detailed study of water flow especially near the soil surface where heterogeneity may be enhanced by biological activity and geomorphological processes. Each of three infiltration tests involved application of 100 L of a mixed dye solution applied by using a standard 60-cm diameter ring infiltrometer under constant-head ponded conditions. After complete water infiltration several vertical soil sections were prepared in a soil block of approximately 1.5-2 m3. Staining patterns were photographed to provide evidence of preferential flow while numerous disturbed and undisturbed samples were collected and analysed in the laboratory to determine soil physical and hydraulic properties including saturated hydraulic conductivity, water retention curve, initial moisture content prior to dye application and bulk densities. Staining patterns in the top 30-40 cm were relatively homogeneous with some fingering. However, presence of a textural break (fine over coarse sand) hypothesized to represent a paleo-riverbed significantly affected redistribution of water, possibly acting as a capillary barrier. Measurements of soil physical properties and soil profile digital photos were used to build a 3D heterogeneous soil hydraulic property model in HYDRUS-3D. Model results for the infiltration tests were quantitatively and qualitatively compared to staining patterns obtained during field experiments. Such studies are important for building better vadose zone models capable of modeling large-scale recharge processes.

Gerke, Kirill; Edde, Ambre; Mallants, Dirk

2013-04-01

329

Towards soil property retrieval from space: A one-dimensional twin-experiment  

NASA Astrophysics Data System (ADS)

Soil moisture is among the key environmental variables controlling evaporation, infiltration and runoff. However, the temporal evolution of soil moisture is not easy to measure or monitor at large scales due to its spatial variability, which is largely driven by local variation in soil properties and vegetation cover. Consequently, soil moisture estimates using land surface models are typically made using effective physical parameterisations based on low-resolution and/or erroneous soil property information. Thus, land surface models have an urgent need for more accurate and detailed soil parameter data sets than are currently available, in order to undertake regional or global simulation studies at high spatial resolution and with the required accuracy. To overcome this limitation, the possibility of estimating the soil hydraulic properties through model calibration to remotely sensed near-surface soil moisture observation is explored. The study presents a methodology that demonstrates this potential using a synthetic twin experiment framework, thus avoiding the need to deal with possible model-observation biases. Moreover, it explores a range of scenarios, with the objective to determine the best meteorologic conditions for soil property retrieval and hence the most efficient use of computational resources when applying the methodology at large scales. These scenarios include: (a) short dry-down period, (b) short dry period, (c) short wet-up period, (d) short wet period and (e) full 12-months with multiple wetting and drying periods. The methodology was also tested for four different soil types including a homogeneous column of sand, a homogeneous column of clay, a duplex column of clay over sand, and a duplex column of silty sand over clay. The study showed that soil hydraulic parameters were best retrieved when using the full 12-month period, with the sequential retrieval of three parameters at a time being the most suitable approach when retrieving the six parameters, with the most sensitive parameters retrieved first.

Bandara, Ranmalee; Walker, Jeffrey P.; Rüdiger, Christoph

2013-08-01

330

Role of precipitation uncertainty in the estimation of hydrologic soil properties using remotely sensed soil moisture in a semi-arid environment 1891  

Technology Transfer Automated Retrieval System (TEKTRAN)

The focus of this study is the role of precipitation uncertainty in determining the accuracy and retrieveability of estimated soil texture and hydraulic properties. This work builds on and extends recent work conducted as part of the ongoing development of the Army Remote Moisture System (ARMS), in...

331

Hydraulic properties of three types of glacial deposits in Ohio  

USGS Publications Warehouse

The effects of thickness, grain size, fractures, weathering, and atmosphericconditions on vertical ground-water flow in glacial deposits were studied at three sites that represent ground moraine, end moraine, and lacustrine depositional environments. Vertical hydraulic conductivities computed from pumped-well tests were 3.24 x 10-1 to 6.47 x 10-1 ft/d (feet per day) at the site representing end moraine and 1.17 ft/d at the site representing lacustrine deposits. Analysis of test data for the ground moraine site did not yield estimates of hydraulic conductivities, but did indicate that ground water flows through the total thickness of deposits in response to discharge from a lower gravel unit. Vertical hydraulic conductivities computed from pumped-well tests of nested wells and data from drill-core analyses indicate that fractures affect the migration of ground water downward through the glacial deposits at these sites. Flow through glacial deposits is complex; it is controlled by fractures, gram-size distribution, clay content, thickness, and degree of weathering, and atmospheric conditions.

Strobel, M.L.

1993-01-01

332

Estimating hydraulic properties from tidal attenuation in the Northern Guam Lens Aquifer, territory of Guam, USA  

USGS Publications Warehouse

Tidal-signal attenuations are analyzed to compute hydraulic diffusivities and estimate regional hydraulic conductivities of the Northern Guam Lens Aquifer, Territory of Guam (Pacific Ocean), USA. The results indicate a significant tidal-damping effect at the coastal boundary. Hydraulic diffusivities computed using a simple analytical solution for well responses to tidal forcings near the periphery of the island are two orders of magnitude lower than for wells in the island’s interior. Based on assigned specific yields of ~0.01–0.4, estimated hydraulic conductivities are ~20–800 m/day for peripheral wells, and ~2,000–90,000 m/day for interior wells. The lower conductivity of the peripheral rocks relative to the interior rocks may best be explained by the effects of karst evolution: (1) dissolutional enhancement of horizontal hydraulic conductivity in the interior; (2) case-hardening and concurrent reduction of local hydraulic conductivity in the cliffs and steeply inclined rocks of the periphery; and (3) the stronger influence of higher-conductivity regional-scale features in the interior relative to the periphery. A simple numerical model calibrated with measured water levels and tidal response estimates values for hydraulic conductivity and storage parameters consistent with the analytical solution. The study demonstrates how simple techniques can be useful for characterizing regional aquifer properties.

Rotzoll, Kolja; Gingerich, Stephen B.; Jenson, John W.; El-Kadi, Aly I.

2013-01-01

333

Effect of Clay Fraction on Hydraulic Properties and DNAPL Distribution in Porous Media  

Microsoft Academic Search

Clays affect the hydraulic properties of natural porous media and commonly occur in all types of sedimentary deposits. Clay minerals and aggregates of clay minerals less than 2 microns in size are unique sediments that have physical and chemical properties much different than their silt and sand-sized counterparts. Even small amounts of clay have been observed to significantly impact the

A. J. Rossman; N. J. Hayden; D. Matmon

2001-01-01

334

Soil Properties as Influenced by Dust Emissions  

NASA Astrophysics Data System (ADS)

Wind erosion selectively removes the most fertile portion of the soil. When sediment balance from wind erosion is negative, soil quality is impoverished. Our objective was to determine the change in selected soil properties that are measures of soil quality as influenced by dust emissions from wind erosion. We sampled saltation drifts and near surface bulk soil from several recently eroded fields, measured selected soil properties, and compared results from the eroded saltation drifts with the non-eroded bulk soil. We found that sandy loams became loamy sands and loamy sands became sands with 10 to 30% increase of sand in the saltation drift with a corresponding decrease in organic matter and cation exchange capacity. Whereas the texture, organic matter, and cation exchange is not benefited by the millions of tons of nutrient and organic matter enriched soil that is deposited in the road ditches, reservoirs, and oceans. In general, wind erosion degrades soil and lowers its capacity to produce food and fiber needed to sustain an increasing population.

Skidmore, E. L.; Tatarko, J.

2003-12-01

335

Using electrical resistivity tomography (ERT) to image the topology of soil properties relevant to solute transport characteristics of soils  

NASA Astrophysics Data System (ADS)

It is widely recognized that not only the local hydraulic properties but also their topology and connectivity as well as interfaces between soil layers and domains are important to model the effective flow and transport characteristics of soils. In order to fully understand how the structural soil properties are related to solute transport properties, the above discussed features have to be imaged with 3-D spatial resolution. Recent studies have shown that electrical resistivity tomography (ERT) can be used to obtain quantitative information about the structure of solute transport (Koestel et al. 2009. Noninvasive 3-D Transport Characterization in a Sandy Soil Using ERT: 2. Transport Process Inference. Vadose Zone Journal 8: 723-734). In this study we demonstrate that ERT can also be applied to derive the topology of hydraulic property-related parameters, namely (i) the mineral surface electrical conductivity (sigma_s) which is a proxy for the clay content and (ii) the electrical formation factor (F) which is a parameter in which porosity, water saturation, and geometry of wetted and non-wetted pore space are lumped. We apply the method to image sigmas and F of four large lysimeters (height: 1.4 m, radius 0.58 m), three of them filled with an undisturbed soil sample and one containing a virtual porous medium (generated with Gaussian random fields). We discuss the result with respect to soil texture, water content measurements, and optically derived soil structures. In a next step, we compare the ERT-derived sigmas and F to the corresponding ERT-derived apparent convection-dispersion parameters. The results of the numerical experiment are used to investigate the accuracy of the ERT images and the benefits and caveats of our approach.

Koestel, John; Garré, Sarah; Javaux, Mathieu; Vanderborght, Jan; Vereecken, Harry

2010-05-01

336

Effects of surfactants and electrolyte solutions on the properties of soil  

NASA Astrophysics Data System (ADS)

Biosurfactants are frequently used in petroleum hydrocarbon and dense non-aqueous phase liquids (DNAPLs) remediation. The applicability of biosurfactant use in clayey soils requires an understanding and characterization of their interaction. Comprehensive effects of surfactants and electrolyte solutions on kaolinite clay soil were investigated for index properties, compaction, strength characteristics, hydraulic conductivities, and adsorption characteristics. Sodium dodecyl sulfate (SDS) and NaPO3 decreased the liquid limit and plasticity index of the test soil. Maximum dry unit weights were increased and optimum moisture contents were decreased as SDS and biosurfactant were added for the compaction tests for mixtures of 30% kaolinite and 70% sand. The addition of non-ionic surfactant, biosurfactant, and CaCl2 increased the initial elastic modulus and undrained shear strength of the kaolinite-sand mixture soils. Hydraulic conductivities were measured by fixed-wall double-ring permeameters. Results showed that the hydraulic conductivity was not significantly affected, but slightly decreased from 1×10-7 cm/s (water) to 0.3×10-7 cm/s for Triton X-100 and SDS. The adsorption characteristics of the chemicals onto kaolinite were also investigated by developing isotherm curves. SDS adsorbed onto soil particles with the strongest bonding strength of the fluids tested. Correlations among parameters were developed for surfactants, electrolyte solutions, and clayey soils.

Park, Junboum; Vipulanandan, Cumaraswamy; Kim, Jee Woong; Oh, Myoung Hak

2006-04-01

337

Estimation of field-scale soil hydraulic and dielectric parameters through joint inversion of GPR and hydrological data  

Microsoft Academic Search

A method is described for the joint use of time-lapse ground-penetrating radar (GPR) travel times and hydrological data to estimate field-scale soil hydraulic parameters. We build upon previous work to take advantage of a wide range of cross-borehole GPR data acquisition configurations and to accommodate uncertainty in the petrophysical function, which relates soil porosity and water saturation to the effective

Michael B. Kowalsky; Stefan A. Finsterle; John Peterson; Susan Hubbard; Yoram Rubin; Ernest L. Majer; Andy L. Ward; Glendon W. Gee

2005-01-01

338

Influence of leaf water status on stomatal response to humidity, hydraulic conductance, and soil drought in Betula occidentalis  

Microsoft Academic Search

Whole-canopy measurements of water flux were used to calculate stomatal conductance (gs) and transpiration (E) for seedlings of western water birch (Betula occidentalis Hook.) under various soil-plant hydraulic conductances (k), evaporative driving forces (?N; difference in leaf-to-air molar fraction of water vapor), and soil water potentials (?s). As expected, gs dropped in response to decreased k or ?S, or increased

Nicanor Z. Saliendra; John S. Sperry; Jonathan P. Comstock

1995-01-01

339

New Conceptual Model for Soil Treatment Units: Formation of Multiple Hydraulic Zones during Unsaturated Wastewater Infiltration.  

PubMed

Onsite wastewater treatment systems are commonly used in the United States to reclaim domestic wastewater. A distinct biomat forms at the infiltrative surface, causing resistance to flow and decreasing soil moisture below the biomat. To simulate these conditions, previous modeling studies have used a two-layer approach: a thin biomat layer (1-5 cm thick) and the native soil layer below the biomat. However, the effect of wastewater application extends below the biomat layer. We used numerical modeling supported by experimental data to justify a new conceptual model that includes an intermediate zone (IZ) below the biomat. The conceptual model was set up using Hydrus 2D and calibrated against soil moisture and water flux measurements. The estimated hydraulic conductivity value for the IZ was between biomat and the native soil. The IZ has important implications for wastewater treatment. When the IZ was not considered, a loading rate of 5 cm d resulted in an 8.5-cm ponding. With the IZ, the same loading rate resulted in a 9.5-cm ponding. Without the IZ, up to 3.1 cm d of wastewater could be applied without ponding; with the IZ, only up to 2.8 cm d could be applied without ponding. The IZ also plays a significant role in soil moisture distribution. Without the IZ, near-saturation conditions were observed only within the biomat, whereas near-saturation conditions extended below the biomat with the IZ. Accurate prediction of ponding is important to prevent surfacing of wastewater. The degree of water and air saturation influences pollutant treatment efficiency through residence time, volatility, and biochemical reactions. PMID:24216371

Geza, Mengistu; Lowe, Kathryn S; Huntzinger, Deborah N; McCray, John E

2013-07-01

340

A HYDRAULIC SOIL CORING SYSTEM FOR SOIL CARBON-ROOT STUDIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Reliable sampling of belowground components is an essential aspect of agroecosystems research. Factors such as difficult soil conditions (e.g., hardpans, rocky or wet conditions), restricted access, and remote sites can often limit adequate sampling in the field. The objective was to design and cons...

341

Estimation of field-scale soil hydraulic and dielectric parameters through joint inversion of GPR and hydrological data  

E-print Network

Estimation of field-scale soil hydraulic and dielectric parameters through joint inversion of GPR November 2005. [1] A method is described for the joint use of time-lapse ground-penetrating radar (GPR previous work to take advantage of a wide range of cross-borehole GPR data acquisition configurations

Hubbard, Susan

342

Long-term hydraulic properties of subsurface flow constructed wetlands  

E-print Network

, 000 Graded Bull Rock N/A (2-5 inches) * (EPA, 1993a; EPA, 1993b) 35 100, 000 It should be noted that EPA (1993a) intends that the listed values be used for preliminary information only. They recommend that the actual hydraulic conductivity 14... Media Dw Size Uniformity Coefficient Sand N/A 0. 27 1. 3 Pea Gravel 10 12 51 4. 7 4. 3 Medium Rock 25 10. 1 17. 2 1. 7 Bull Rock 76-127 51. 4 66. 1 1. 3 All of the wooden troughs leaked to some extent. The fiberglass resin and silicone...

Turner, Glenn Allen

1994-01-01

343

Hydraulic Properties of Rice and the Response of Gas Exchange to Water Stress1  

PubMed Central

We investigated the role of xylem cavitation, plant hydraulic conductance, and root pressure in the response of rice (Oryza sativa) gas exchange to water stress. In the field (Philippines), the percentage loss of xylem conductivity (PLC) from cavitation exceeded 60% in leaves even in watered controls. The PLC versus leaf water potential relationship indicated diurnal refilling of cavitated xylem. The leaf water potential causing 50 PLC (P50) was –1.6 MPa and did not differ between upland versus lowland rice varieties. Greenhouse-grown varieties (Utah) were more resistant to cavitation with a 50 PLC of –1.9 MPa but also showed no difference between varieties. Six-day droughts caused concomitant reductions in leaf-specific photosynthetic rate, leaf diffusive conductance, and soil-leaf hydraulic conductance that were associated with cavitation-inducing water potentials and the disappearance of nightly root pressure. The return of root pressure after drought was associated with the complete recovery of leaf diffusive conductance, leaf-specific photosynthetic rate, and soil-leaf hydraulic conductance. Root pressure after the 6-d drought (61.2 ± 8.8 kPa) was stimulated 7-fold compared with well-watered plants before drought (8.5 ± 3.8 kPa). The results indicate: (a) that xylem cavitation plays a major role in the reduction of plant hydraulic conductance during drought, and (b) that rice can readily reverse cavitation, possibly aided by nocturnal root pressure. PMID:12857848

Stiller, Volker; Lafitte, H. Renee; Sperry, John S.

2003-01-01

344

Sprinkler Irrigation Effects on Infiltration and Near-Surface Unsaturated Hydraulic Conductivity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil organic carbon (SOC) from dairy manure can help to restore productivity of eroded soil. SOC, irrigation, or both may alter soil hydraulic properties. We evaluated effects of SOC and simulated center-pivot irrigation on infiltration and near-surface hydraulic conductivity (K) measured under tens...

345

Predicting the hydraulic conductivity of saturated clays using plasticity-value correlations  

Microsoft Academic Search

Hydraulic conductivity is one of the important, basic engineering properties of soils. However, as a soil parameter it is difficult to measure and can be highly variable, necessitating the investigation of a large number of samples. For these reasons several researchers have proposed various indirect methods for predicting the hydraulic conductivity of soils from easily measured and routinely obtainable data.

Bojana Dolinar

2009-01-01

346

Coupled mechanics, hydraulics and sorption properties of mixtures to evaluate buffer/backfill materials  

NASA Astrophysics Data System (ADS)

The buffer materials that retarding the migration of nuclides and making the canisters stable in a geological deep repository of high-level radioactive waste play a very important role. This study coupled engineering and sorption properties to evaluate the buffer/backfill materials. The Rd values of Cs, Se and I (10 -4 M) with respect to various composite ratios of bentonite/laterite/quartz sand mixtures were measured using batch sorption tests in groundwater (GW) and seawater (SW) which simulate possible conditions for a deep geological disposal in an island. Deionized water (DIW) was used as the liquid phase for Atterberg limits tests, triaxial shear tests and hydraulic conductivity tests in order to determine the engineering properties of the mixtures. From the results of the Atterberg limits tests, seven samples were classified as inorganic clays of high plasticity and one sample was classified as inorganic clays of medium plasticity. Under the test condition of samples with dry density of 1.75 ± 0.05 g/cm 3, the samples with 30% quartz sand content demonstrated higher shear strength. Very low hydraulic conductivities of four selected samples were measured, ranging from 1.46 × 10 -11 m/s to 2.94 × 10 -11 m/s. The sorption behavior of Cs, Se and I on every individual solid material (laterite, bentonite and quartz sand) can be summed up as follows: the sorption of Se is significantly more affected by the solid phase (Rdlaterite>Rdbentonite) than by the liquid phase (GW or SW). Contrarily, the sorption of Cs is more affected by the nature of the liquid phase (RdGW>RdSW) rather than solid phase. On the mixtures used in this work, the sorption of Cs was higher in GW suspensions, when the plastic index (PI) = 40-50 and a 30% quartz sand content. Regarding the relationship between sorption of selenium and engineering characteristics, the mixtures with PI = 40-50 (30% quartz sand content) were the potentially more adequate composite materials. Slight sorption of I was observed on all mixtures in GW and SW. On the basis of the results presented in this work, the composition of 30% quartz sand content which PI = 40-50 might be the best choice for the buffer/backfill materials. Finally, a local soil, laterite, exhibited higher sorption capacity of Cs and Se in both GW and SW than bentonite.

Jan, Yi-Lin; Tsai, Shih-Chin; Wei, Yuan-Yaw; Tung, Ning-Chien; Wei, Chia-Chen; Hsu, Chun-Nan

347

Electrical and Hydraulic Properties of Humified Bog Peat as a Function of Pore-fluid Conductivity  

NASA Astrophysics Data System (ADS)

The electrical properties of organic sediments and their relationship to physical properties are poorly understood. A simple approach to relate electrical properties to physical properties commonly applied to inorganic sediments is to model the electrolytic conductivity and the surface conductivity as parallel conduction paths. Low-frequency electrical measurements were made in conjunction with hydraulic conductivity measurements on peat samples from an 11 m section collected in a large freshwater peatland. The electrical and hydraulic measurements were made as a function of NaCl concentration and depth of burial. In all cases, the electrical conductivity of the peat was not well modeled by the parallel conduction path model, with the model yielding formation factor values close to one. Sample measurements along the section suggest a slight increase in the formation factor and surface conductivity values with depth. Hydraulic conductivity measured by constant head method shows a marked increase with increasing NaCl concentration, which we believe results from expansion of macropore porosity by chemical dilation as proposed by others. Attempts to return the samples to their original conditions by decreasing the salinity only partially restored the hydraulic conductivity values, indicating a permanent disruption of the hydraulic properties of the peat. The increase of surface electrical conductivity and hydraulic conductivity with depth may indicate a close correlation with the high cation exchange capacity of organic matter and its tendency for chemical dilation as decomposition of organic matter increases with depth. We propose that the electrical conductivity of peat cannot be modeled by an electrolytic and a surface conduction path in parallel. The increase in the electrolytic conduction causes ionic accumulation and dispersion processes, expanding the macropore porosity and hence inducing a decrease in the formation factor values. A proper electrical model for organic materials such as peat needs to include this pore dilation effect caused by the increase in electrolytic conduction.

Comas, X.; Slater, L.

2003-12-01

348

Dynamic properties of cemented soils from Cyprus  

Microsoft Academic Search

The paper presents results from a laboratory investigation into the dynamic properties of natural cemented sandy and cohesive\\u000a soils from Cyprus, as expressed by shear modulus and damping ratio. The influence of various soil parameters, such as strain\\u000a level, confining stress, undrained shear strength, void ratio, plasticity index, cementation and organic matter content is\\u000a discussed. The test results show that

Th. Tika; P. Kallioglou; G. Koninis; P. Michaelidis; M. Efthimiou; K. Pitilakis

2010-01-01

349

The effect of soil moisture on thermal properties in some typical Japanese upland soils  

Microsoft Academic Search

The effects of soil moisture on thermal properties of some typical Japanese upland soils were studied. Thermal properties which were studied here were volumetric heat capacity, thermal conductivity, and thermal diffusivity. Sample taken at various horizons of volcanic ash (Yachimata) soil, alluvial (Kiyosu) soil, and diluvial (Toyoilashi) soil were used. The results are summarized as follows. 1) Volumetric heat capacity

Tatsuaki Kasubuchi

1975-01-01

350

UNSATURATED SOIL HYDRAULIC PROPERTIES FROM REDISTRIBUTION OF INJECTED WATER  

EPA Science Inventory

An analytical and experimental investigation of a matching method for the determination of the parameters in the Brooks-Corey K(h) and h(theta) relationships is presented. The method is based upon fitting an analytically derived response function to the corresponding measured one...

351

Measuring Hysteretic Hydraulic Properties of Peat and Pine Bark using a Transient Method  

Microsoft Academic Search

However, until now, most studies dealing with the phys- ical properties of substrates have only attempted to char- The precise and continuous measurement of the hydraulic proper- acterizewaterandgasdistributionrelatedtowaterpoten- ties of growing media is of vital importance for the effective manage- ment of irrigation and fertilization. The main purpose of this study tial (Bunt, 1961; De Boodt and Verdonck, 1972; Riviere

R. Naasz; J.-C. Michel; S. Charpentier

2005-01-01

352

LEACHING AND HYDRAULIC PROPERTIES OF RETORTED OIL SHALE INCLUDING EFFECTS FROM CODISPOSAL OF WASTEWATER  

EPA Science Inventory

The report discusses the development of methods and data on the leaching and hydraulic properties of solid residues from oil shale processing. A column test, the Equilibrated Soluble Mass (ESM) test, was developed as an aid to characterizing the chemical quality of the first leac...

353

Minimum property dataset and sampling requirement tool for soil change studies in soil survey  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dynamic soil properties (DSP) are those properties that change over human time scales. The new sampling guide “Soil and Resource Inventory Guide for Dynamic Soil Properties and Soil Change” includes a minimum DSP dataset and an interactive tool to determine sampling requirements. The minimum dataset...

354

Quasi-steady centrifuge method for unsaturated hydraulic properties  

USGS Publications Warehouse

[1] We have developed the quasi-steady centrifuge (QSC) method as a variation of the steady state centrifuge method that can be implemented simply and inexpensively with greater versatility in terms of sample size and other features. It achieves these advantages by somewhat relaxing the criterion for steadiness of flow through the sample. This compromise entails an increase in measurement uncertainty but to a degree that is tolerable in most applications. We have tested this new approach with an easily constructed apparatus to establish a quasi-steady flow of water in unsaturated porous rock samples spinning in a centrifuge, obtaining measurements of unsaturated hydraulic conductivity and water retention that agree with results of other methods. The QSC method is adaptable to essentially any centrifuge suitable for hydrogeologic applications, over a wide range of sizes and operating speeds. The simplified apparatus and greater adaptability of this method expands the potential for exploring situations that are common in nature but have been the subject of few laboratory investigations. Copyright 2005 by the American Geophysical Union.

Caputo, M.C.; Nimmo, J.R.

2005-01-01

355

Scaling of material properties for Yucca Mountain: literature review and numerical experiments on saturated hydraulic conductivity  

SciTech Connect

A review of pertinent literature reveals techniques which may be practical for upscaling saturated hydraulic conductivity at Yucca Mountain: geometric mean, spatial averaging, inverse numerical modeling, renormalization, and a perturbation technique. Isotropic realizations of log hydraulic conductivity exhibiting various spatial correlation lengths are scaled from the point values to five discrete scales through these techniques. For the variances in log{sub 10} saturated hydraulic conductivity examined here, geometric mean, numerical inverse and renormalization adequately reproduce point scale fluxes across the modeled domains. Fastest particle velocities and dispersion measured on the point scale are not reproduced by the upscaled fields. Additional numerical experiments examine the utility of power law averaging on a geostatistical realization of a cross-section similar to the cross-sections that will be used in the 1995 groundwater travel time calculations. A literature review on scaling techniques for thermal and mechanical properties is included. 153 refs., 29 figs., 6 tabs.

McKenna, S.A.; Rautman, C.A.

1996-08-01

356

Status Report on Transfer of Physical and Hydraulic Properties Databases to the Hanford Environmental Information System - PNNL Remediation Decision Support Project, Task 1, Activity 6  

SciTech Connect

This document provides a status report on efforts to transfer physical and hydraulic property data from PNNL to CHPRC for incorporation into HEIS. The Remediation Decision Support (RDS) Project is managed by Pacific Northwest National Laboratory (PNNL) to support Hanford Site waste management and remedial action decisions by the U.S. Department of Energy and their contractors. The objective of Task 1, Activity 6 of the RDS project is to compile all available physical and hydraulic property data for sediments from the Hanford Site, to port these data into the Hanford Environmental Information System (HEIS), and to make the data web-accessible to anyone on the Hanford Local Area Network via the so-called Virtual Library. These physical and hydraulic property data are used to estimate parameters for analytical and numerical flow and transport models that are used for site risk assessments and evaluation of remedial action alternatives. In past years efforts were made by RDS project staff to compile all available physical and hydraulic property data for Hanford sediments and to transfer these data into SoilVision{reg_sign}, a commercial geotechnical software package designed for storing, analyzing, and manipulating soils data. Although SoilVision{reg_sign} has proven to be useful, its access and use restrictions have been recognized as a limitation to the effective use of the physical and hydraulic property databases by the broader group of potential users involved in Hanford waste site issues. In order to make these data more widely available and useable, a decision was made to port them to HEIS and to make them web-accessible via a Virtual Library module. In FY08 the original objectives of this activity on the RDS project were to: (1) ensure traceability and defensibility of all physical and hydraulic property data currently residing in the SoilVision{reg_sign} database maintained by PNNL, (2) transfer the physical and hydraulic property data from the Microsoft Access database files used by SoilVision{reg_sign} into HEIS, which is currently being maintained by CH2M-Hill Plateau Remediation Company (CHRPC), (3) develop a Virtual Library module for accessing these data from HEIS, and (4) write a User's Manual for the Virtual Library module. The intent of these activities is to make the available physical and hydraulic property data more readily accessible and useable by technical staff and operable unit managers involved in waste site assessments and remedial action decisions for Hanford. In FY08 communications were established between PNNL and staff from Fluor-Hanford Co. (who formerly managed HEIS) to outline the design of a Virtual Library module that could be used to access the physical and hydraulic property data that are to be transferred into HEIS. Data dictionaries used by SoilVision{reg_sign} were also provided to Fluor-Hanford personnel who are now with CHPRC. During ongoing work to ensure traceability and defensibility of all physical and hydraulic property data that currently reside in the SoilVision{reg_sign} database, it was recognized that further work would be required in this effort before the data were actually ported into HEIS. Therefore work on the Virtual Library module development and an accompanying User's Guide was deferred until an unspecified later date. In FY09 efforts have continued to verify the traceability and defensibility of the physical and hydraulic property datasets that are currently being maintained by PNNL. Although this is a work in progress, several of these datasets are now ready for transfer to CHRPC for inclusion in HEIS. The actual loading of data into HEIS is performed by CHPRC staff, so after the data are transferred from PNNL to CHPRC, it will be the responsibility of CHPRC to ensure that these data are loaded and made accessible. This document provides a status report on efforts to transfer physical and hydraulic property data from PNNL to CHPRC for incorporation into HEIS.

Rockhold, Mark L.; Middleton, Lisa A.; Cantrell, Kirk J.

2009-06-30

357

Prototype Data Models and Data Dictionaries for Hanford Sediment Physical and Hydraulic Properties  

SciTech Connect

The Remediation Decision Support (RDS) project, managed by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) and the CH2M HILL Plateau Remediation Company (CHPRC), has been compiling physical and hydraulic property data and parameters to support risk analyses and waste management decisions at Hanford. In FY09 the RDS project developed a strategic plan for a physical and hydraulic property database. This report documents prototype data models and dictionaries for these properties and associated parameters. Physical properties and hydraulic parameters and their distributions are required for any type of quantitative assessment of risk and uncertainty associated with predictions of contaminant transport and fate in the subsurface. The central plateau of the Hanford Site in southeastern Washington State contains most of the contamination at the Site and has up to {approx}100 m of unsaturated and unconsolidated or semi-consolidated sediments overlying the unconfined aquifer. These sediments contain a wide variety of contaminants ranging from organic compounds, such as carbon tetrachloride, to numerous radionuclides including technetium, plutonium, and uranium. Knowledge of the physical and hydraulic properties of the sediments and their distributions is critical for quantitative assessment of the transport of these contaminants in the subsurface, for evaluation of long-term risks and uncertainty associated with model predictions of contaminant transport and fate, and for evaluating, designing, and operating remediation alternatives. One of the goals of PNNL's RDS project is to work with the Hanford Environmental Data Manager (currently with CHPRC) to develop a protocol and schedule for incorporation of physical property and hydraulic parameter datasets currently maintained by PNNL into HEIS. This requires that the data first be reviewed to ensure quality and consistency. New data models must then be developed for HEIS that are approved by the HTAG that oversees HEIS development. After approval, these new data models then need to be implemented in HEIS by the EDM before there is an actual repository for the data. This document summarizes modifications to previously developed data models, and new data models and data dictionaries for physical and hydraulic property data and parameters to be transferred to HEIS. A prototype dataset that conforms to the specifications of these recommended data models has been identified and processed, and is ready for transfer to CHPRC for inclusion in HEIS. Additional datasets are planned for transfer from PNNL to CHPRC in FY11.

Rockhold, Mark L.; Last, George V.; Middleton, Lisa A.

2010-09-30

358

Flow property and self-similarity in steady hydraulic jumps  

NASA Astrophysics Data System (ADS)

The flow structure in a steady hydraulic jump in both the non-aerated and aerated regions was measured using the image-based particle image velocimetry and bubble image velocimetry techniques, respectively. Three highly aerated steady jumps with Froude numbers varying from 4.51 to 5.35 were tested, and a weak jump with a Froude number of 2.43 was generated for comparison. Mean velocities and turbulence statistics were obtained by ensemble averaging the repeated velocity measurements. Based on the mean velocities, the flow structure in the steady jumps was classified into four regions to distinguish their distinct flow behaviors; they are the potential core region, the boundary layer region, the mixing layer region, and the recirculation region. The flow structure in the weak jump features only three regions without the recirculation region. In addition, spatial variations of mean velocities, turbulence intensity, and Reynolds stresses were also presented. It was observed that the maximum horizontal bubble velocity and maximum horizontal water velocity occur at the same location in the overlapping regions of potential core and mixing layer. The ratio between the maximum horizontal bubble velocity and maximum horizontal water velocity is between 0.6 and 0.8, depending on the Froude number. Examining the mean horizontal bubble velocities in the mixing layer, a similarity profile was revealed with representative mixing layer thickness as the characteristic length scale and the difference between the maximum positive and maximum negative velocities as the characteristic velocity scale. It was also found that the mean horizontal water velocities in the near-wall region are self-similar and behave like a wall jet. Further analyzing autocorrelation functions and energy spectra of the water and bubble velocity fluctuations found that the energy spectra in the water region follow the -5/3 slope, whereas the spectra in the bubble region follow a -2/5 slope. In addition, the integral length scale of bubbles is one order of magnitude shorter than that of water.

Lin, Chang; Hsieh, Shih-Chun; Lin, I.-Ju; Chang, Kuang-An; Raikar, Rajkumar V.

2012-11-01

359

Hydraulic testing around Room Q: Evaluation of the effects of mining on the hydraulic properties of Salado Evaporites  

SciTech Connect

Room Q is a 109-m-long cylindrical excavation in the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site. Fifteen boreholes were drilled and instrumented around Room Q so that tests could be conducted to determine the effects of room excavation on the hydraulic properties of the surrounding evaporate rocks. Pressure-buildup and pressure-pulse tests were conducted in all of the boreholes before Room Q was mined. The data sets from only eight of the boreholes are adequate for parameter estimation, and five of those are of poor quality. Constant-pressure flow tests and pressure-buildup tests were conducted after Room Q was mined, producing eleven interpretable data sets, including two of poor quality. Pre-mining transmissivities interpreted from the three good-quality data sets ranged from 1 x 10{sup -15} to 5 x 10{sup -14} m{sup 2}/s (permeability-thickness products of 2 x 10{sup -22} to 9 x 10{sup -21} m{sup 3}) for test intervals ranging in length from 0.85 to 1.37 m. Pre-mining average permeabilities, which can be considered representative of undisturbed, far-field conditions, were 6 x 10{sup -20} and 8 x 10{sup -20} m{sup 2} for anhydrite, and 3 x 10{sup -22} m{sup 2} for halite. Post-mining transmissivities interpreted from the good-quality data sets ranged from 1 x 10{sup -16} to 3 x 10{sup -13} m{sup 2}/s (permeability-thickness products of 2 x 10{sup -23} to 5 x 10{sup -20} m{sup 3}). Post-mining average permeabilities for anhydrite ranged from 8 x 10{sup -20} to 1 x 10{sup -19} m{sup 2}. The changes in hydraulic properties and pore pressures that were observed can be attributed to one or a combination of three processes: stress reduction, changes in pore connectivity, and flow towards Room Q. The effects of the three processes cannot be individually quantified with the available data.

Domski, P.S.; Upton, D.T. [INTERA, Inc., Albuquerque, NM (United States); Beauheim, R.L. [Sandia National Laboratories, Albuquerque, NM (United States)

1996-03-01

360

Properties of lunar soil simulant JSC-1  

NASA Astrophysics Data System (ADS)

With the establishment of a lunar base, many tasks will require direct interaction between the in-situ lunar soil and a wide variety of instruments and implements. The individual tasks may be scientific in nature, or simply the manipulation of the lunar soil. To help fulfill the need for relatively large quantities of lunar soil simulant in researching these operations, Johnson Space Center has developed a new simulant called JSC-1. It is produced from a basaltic pyroclastic sheet deposit located in the San Francisco volcanic field near Flagstaff, Arizona. JSC-1 is a crushed, ground, and sieved material that was developed to have similar mechanical properties and characteristics of the lunar soil. Furthermore, this glass-rich basaltic ash can be used in chemical or mineralogical resource studies. The Lunar Soil Simulant Laboratory, at the Civil Engineering Department, at Texas A&M University, is responsible for analyzing, storing, and distributing this material to qualified researchers. Information regarding the availability of JSC-1 is provided at the end of the paper. The purpose of this paper is to assess JSC-1 as a close terrestrial analog of the lunar soil and to inform the research community of the availability of the new simulant.

Willman, Brian M.; Boles, Walter W.; McKay, David S.; Allen, Carlton C.

1995-04-01

361

Electrokinetic properties of soil minerals and soils modified with polyelectrolytes  

NASA Astrophysics Data System (ADS)

The formation features of nanoadsorption polyelectrolyte (PE) layers with the formation of a mineral-organic matrix on the surface of clay minerals and soils (kaolinite, montmorillonite, quartz sand, gray forest soil, and chernozemic soil) have been elucidated by direct adsorption measurements. It has been found that the experimental values for the limit adsorption of polyacrylamide (PAM) and polyacrylic acid (PAA) on all the minerals are significantly higher than the calculated values for the formation of a monolayer. This indicates adsorption on the surface of not only separate macromolecules but also secondary PE structures as packets or fibrils determining the cluster-matrix structure of the modified surface. The study of the electro-surface properties (electrophoretic mobility, electrokinetic potential, pH, and electroconductivity) of mineral and soil particles adsorption-modified with PEs has confirmed the differences in the adsorption mechanisms (from physical sorption to chemisorption) with the formation of surface compounds depending on the different polar groups of PEs and the mineral type.

Kurochkina, G. N.; Pinskii, D. L.; Haynos, M.; Sokolowska, Z.; Tsesla, I.

2014-07-01

362

Soil characteristics and landcover relationships on soil hydraulic conductivity at a hillslope scale: A view towards local flood management  

NASA Astrophysics Data System (ADS)

There are surprisingly few studies in humid temperate forests which provide reliable evidence that soil permeability is enhanced under forests. This work addresses this research gap through a detailed investigation of permeability on a hillslope in the Eddleston Catchment, Scottish Borders UK, to evaluate the impact of land cover, superficial geology and soil types on permeability using measurements of field saturated hydraulic conductivity (Kfs) supported by detailed topsoil profile descriptions and counting of roots with diameters >2 mm. Kfs was measured at depth 0.04-0.15 m using a constant head well permeameter across four paired landcover sites of adjacent tree and intensely grazed grassland. The measured tree types were: 500-year-old mixed woodland; 180-year-old mixed woodland; 45-year-old Pinus sylvestris plantation; and 180-year-old Salix caprea woodland. The respective paired grids of trees and grassland were compared on similar soil texture and topography. This study highlights the significant impact of broadleaf woodland at a hillslope scale on Kfs in comparison to grassland areas: median Kfs values under 180-year-old S. caprea woodland (8 mm h-1), 180-year-old mixed woodland (119 mm h-1) and 500-year-old broadleaf woodland (174 mm h-1) were found to be respectively 8, 6 and 5 times higher than neighbouring grazed grassland areas on the same superficial geology. Further statistical analysis indicates that such Kfs enhancement is associated with the presence of coarse roots (>2 mm diameter) creating conduits for preferential flow and a deeper organic layer in the topsoil profile under woodlands. By contrast the P. sylvestris forest had only slightly higher (42 mm h-1), but not statistically different Kfs values, when compared to adjacent pasture (35 mm h-1). In the grassland areas, in the absence of course roots, the superficial geology was dominant in accounting for differences in Kfs, with the alluvium floodplain having a significantly lower median Kfs (1 mm h-1) than surrounding hillslope sites, which had a range of median Kfs from 21 to 39 mm h-1. The data were used to infer areas of runoff generation by comparing Kfs values with modelled 15 min maximum intensity duration rainfall with a 1 in 10 year return period. Infiltration prevailed in the 180- and 500-year-old mixed and broadleaf woodland, whereas some grassland areas and the floodplain were inferred to generate overland flow. The significantly higher Kfs under broadleaf mature forests suggests that planting broadleaf woodlands on hillslopes in clusters or as shelterbelts within grasslands would provide areas of increased capacity for rainfall infiltration and arrest runoff generation during flood-producing storm events.

Archer, N. A. L.; Bonell, M.; Coles, N.; MacDonald, A. M.; Auton, C. A.; Stevenson, R.

2013-08-01

363

DESIGN AND MANAGEMENT OF SUBSURFACE SOIL ABSORPTION SYSTEMS  

EPA Science Inventory

The results of two studies are reported: (1) the effects of construction practices upon soil hydraulic properties; and (2) field examination of the effects of operational strategies upon soil infiltration properties. The investigation of construction practices showed that heavy m...

364

TILL AND NO-TILL SOIL MANAGEMENT EFFECTS ON SOIL PHYSICAL PROPERTIES AND CORN YIELD  

Technology Transfer Automated Retrieval System (TEKTRAN)

Compacted soils generally have higher bulk density, increased mechanical impedance, and lower levels of water movement and oxygen than soils that are not compacted. Our objectives were to measure soil physical properties of soil under tilled and no-till soil management and to investigate the relati...

365

A full probabilistic description of infiltration into soils with uncertain hydraulic parameters  

NASA Astrophysics Data System (ADS)

Heterogeneity and the lack of sufficient characterizations of the vadose zone render predictions of unsaturated flow and transport inherently uncertain. Quantification of predictive uncertainty is facilitated by treating relevant parameters (e.g., saturated hydraulic conductivity and coefficients in constitutive models) as random fields. Flow and transport equations become stochastic, and their solutions are typically reported in terms of the first two ensemble moments. Thus, predictions are given by the ensemble means (averages) of the system states (e.g., pressure, saturation, and moisture flux), while their variances serve to quantify the corresponding predictive uncertainty. Such approaches are insufficient for risk analysis, which requires one to evaluate probabilities of rare events (distribution tails). Such information is incapsulated in the probability density function (PDF) of a system state. We derive such PDFs for the evolution of a wetting front described by Green-Ampt model. We investigate the relative effects of different sources of uncertainty, the choice of constitutive models, and the degree of correlation between various soil parameters on the temporal evolution of the PDFs.

Wang, P.; Tartakovsky, D. M.

2009-12-01

366

Submitted to WRR 1 Use of hydraulic tests at different scales to characterize fracture network properties in  

E-print Network

Submitted to WRR 1 Use of hydraulic tests at different scales to characterize fracture network, hydraulic conductivity, fracture, anisotropy 1. INTRODUCTION Hard rocks and their associated aquifers occur properties in the weathered-fractured layer of a hard rock aquifer J.C. Maréchala,b* , B. Dewandela , K

Boyer, Edmond

367

Impact of Sub-grid Soil Textural Properties on Simulations of Hydrological Fluxes at the Continental Scale Mississippi River Basin  

NASA Astrophysics Data System (ADS)

Knowledge of soil hydraulic properties such as porosity and saturated hydraulic conductivity is required to accurately model the dynamics of near-surface hydrological processes (e.g. evapotranspiration and root-zone soil moisture dynamics) and provide reliable estimates of regional water and energy budgets. Soil hydraulic properties are commonly derived from pedo-transfer functions using soil textural information recorded during surveys, such as the fractions of sand and clay, bulk density, and organic matter content. Typically large scale land-surface models are parameterized using a relatively coarse soil map with little or no information on parametric sub-grid variability. In this study we analyze the impact of sub-grid soil variability on simulated hydrological fluxes over the Mississippi River Basin (?3,240,000 km2) at multiple spatio-temporal resolutions. A set of numerical experiments were conducted with the distributed mesoscale hydrologic model (mHM) using two soil datasets: (a) the Digital General Soil Map of the United States or STATSGO2 (1:250 000) and (b) the recently collated Harmonized World Soil Database based on the FAO-UNESCO Soil Map of the World (1:5 000 000). mHM was parameterized with the multi-scale regionalization technique that derives distributed soil hydraulic properties via pedo-transfer functions and regional coefficients. Within the experimental framework, the 3-hourly model simulations were conducted at four spatial resolutions ranging from 0.125° to 1°, using meteorological datasets from the NLDAS-2 project for the time period 1980-2012. Preliminary results indicate that the model was able to capture observed streamflow behavior reasonably well with both soil datasets, in the major sub-basins (i.e. the Missouri, the Upper Mississippi, the Ohio, the Red, and the Arkansas). However, the spatio-temporal patterns of simulated water fluxes and states (e.g. soil moisture, evapotranspiration) from both simulations, showed marked differences; particularly at a shorter time scale (hours to days) in regions with coarse texture sandy soils. Furthermore, the partitioning of total runoff into near-surface interflows and baseflow components was also significantly different between the two simulations. Simulations with the coarser soil map produced comparatively higher baseflows. At longer time scales (months to seasons) where climatic factors plays a major role, the integrated fluxes and states from both sets of model simulations match fairly closely, despite the apparent discrepancy in the partitioning of total runoff.

Kumar, R.; Samaniego, L. E.; Livneh, B.

2013-12-01

368

Estimating hydraulic properties of volcanic aquifers using constant-rate and variable-rate aquifer tests  

USGS Publications Warehouse

In recent years the ground-water demand of the population of the island of Maui, Hawaii, has significantly increased. To ensure prudent management of the ground-water resources, an improved understanding of ground-water flow systems is needed. At present, large-scale estimations of aquifer properties are lacking for Maui. Seven analytical methods using constant-rate and variable-rate withdrawals for single wells provide an estimate of hydraulic conductivity and transmissivity for 103 wells in central Maui. Methods based on constant-rate tests, although not widely used on Maui, offer reasonable estimates. Step-drawdown tests, which are more abundantly used than other tests, provide similar estimates as constant-rate tests. A numerical model validates the suitability of analytical solutions for step-drawdown tests and additionally provides an estimate of storage parameters. The results show that hydraulic conductivity is log-normally distributed and that for dike-free volcanic rocks it ranges over several orders of magnitude from 1 to 2,500 m/d. The arithmetic mean, geometric mean, and median values of hydraulic conductivity are respectively 520, 280, and 370 m/d for basalt and 80, 50, and 30 m/d for sediment. A geostatistical approach using ordinary kriging yields a prediction of hydraulic conductivity on a larger scale. Overall, the results are in agreement with values published for other Hawaiian islands. ?? 2007 American Water Resources Association.

Rotzoll, K.; El-Kadi, A. I.; Gingerich, S.B.

2007-01-01

369

Fallow Effects on Improving Soil Properties and Decreasing Erosion: Atlantic Forest, Southeastern Brazil  

NASA Astrophysics Data System (ADS)

Soil tillage plays a major role in changing physical and hydrological properties of soils through time, and in consequence, in the dynamics of infiltration, soil water and erosion. In the hilly landscape of southeastern Brazil, many areas originally occupied by the Atlantic Forest (one the most threatened biomes on the planet) have been continuously transformed in the last decades into agricultural systems, usually associated with small farming properties. Traditionally, the agricultural activities in these areas incorporate rotational systems which include a fallow period, where previously farmed areas repose for at least five years. In some areas, vegetation grows so fast that after 7 or 8 years these sites may be considered by regulator agencies as forests, impeding their use again for farming. As a consequence, farmers tend to decrease the amount of time used fallow impeding the recovery of original soil properties, reducing in consequence the infiltration rate, and increasing the runoff and erosion. Currently, the Brazilian laws allow that the farmers use the fallow system for 10 years in areas where this technique has been used traditionally. So, a major issue here is for how long the farming plots should be left reposing. Therefore, this study aims both to characterize the effects of continuous farming on soil physical and hydrological properties, as well as to define the impacts of different fallow periods on the improvement of soil properties and in the reduction of runoff and erosion. The experiments were carried out in a cultivation site located at Bom Jardim city, close to Rio de Janeiro city. The area is situated at about 800m of elevation in the hilly steep topography of the Serra do Mar, a coast range in southeastern Brazil, with an average total annual rainfall of 2000 mm. In this study, carried out in a typical farm of the area, we compared the effects of 5 different soil usages on soil properties: banana, coffee, F2 (2-year fallow), F5 (5-year fallow) and forest. For each case, 12 soil samples were collected at 4 depths: 0-5, 5-10, 10-20 and 20-30cm, with 3 repetitions, leading to a total of 60 soil samples, where the following properties were characterized: porosity (micro, macro and total), bulk density and aggregate stability. Besides, in situ measurements of saturated hydraulic conductivity were conducted with a Guelph permeameter. The results obtained in this study attested that all the soil properties analyzed were affected by soil usage, especially at shallow depths, in particular macroporosity and total porosity, which have major influences on infiltration rates, runoff and soil erosion. Besides, the results suggested that the 5-year fallow (F5) was able to recover from 72% to 100% of total porosity for the 0-10cm depth layer (considering forest values as reference), while in the 2-year fallow (F2) this recovery was lower, ranging from 66 to 80%. A similar trend was observed for macroporosity, showing recovering values from 60% to 90% and from 50% to 76%, for F5 and F2, respectively. However, aggregate stability values did not show significant variations between the two fallows. Saturated hydraulic conductivity, on the other hand, presented the lowest recovering values for all the studied properties: between 13% and 58% for F5 and between 6% and 33% for F2. Comparing to the natural forest (reference value), the coffee plantations presented the worst soil conditions in terms of soil hydrology and erosion. The results presented here attested important improvements in soil physical and hydrological properties after a 5-year fallow, leading to decrease in surface runoff and soil erosion in the area.

Miranda, J. P.; Silva, L. M.; Lima, R. L.; Donagemma, G. K.; Bertolino, A. V. A.; Fernandes, N. F.; Correa, F. M.; Polidoro, J. C.; Tato, G.

2009-04-01

370

Tillage system affects microbiological properties of soil  

NASA Astrophysics Data System (ADS)

Soil tillage significantly affects organic carbon accumulation, microbial biomass, and subsequently enzymatic activity in surface soil. Microbial activity in soil is a crucial parameter contributing to soil functioning, and thus a basic quality factor for soil. Since enzymes remain soil after excretion by living or disintegrating cells, shifts in their activities reflect long-term fluctuations in microbial biomass. In order to study the effects of no-till on biochemical and microbiological properties in comparison to conventional tillage in a representative soil from South Spain, an experiment was conducted since 1982 on the experimental farm of the Institute of Agriculture and Fisheries Research of Andalusia (IFAPA) in Carmona, SW Spain (37o24'07''N, 5o35'10''W). The soil at the experimental site was a very fine, montomorillonitic, thermic Chromic Haploxerert (Soil Survey Staff, 2010). A randomized complete block design involving three replications and the following two tillage treatments was performed: (i) Conventional tillage, which involved mouldboard plowing to a depth of 50 cm in the summer (once every three years), followed by field cultivation to a depth of 15 cm before sowing; crop residues being burnt, (ii) No tillage, which involved controlling weeds before sowing by spraying glyphosate and sowing directly into the crop residue from the previous year by using a planter with double-disk openers. For all tillage treatments, the crop rotation (annual crops) consisted of winter wheat, sunflower, and legumes (pea, chickpea, or faba bean, depending on the year), which were grown under rainfed conditions. Enzymatic activities (ß-glucosidase, dehydrogenase, aryl-sulphatase, acid phosphatase, and urease), soil microbial biomass by total viable cells number by acridine orange direct count, the density of cultivable groups of bacteria and fungi by dilution plating on semi-selective media, the physiological profiles of the microbial communities by BiologR, and the Shannon (H') and Gini (1-G) diversity index of microbial communities were determined in soil samples (0-10 cm depth) taken in autumn 2009. All the enzymatic activities and the biomass estimated by viable cell counting were significantly higher under no-till than under conventional tillage. However, only fluorescents pseudomonas population was increased under no-till, meanwhile oligotrophic bacteria and actinomycetes populations were higher with conventional tillage than with no-till. Overall, there was a higher use all the group of carbon sources used in the BiologR test with conventional tillage than with no-till, by except amines and phenols which showed non-significant differences. This reveals different physiological profiles in the microbial communities under both tillage systems. The Gini diversity was significantly lower with no-till than with conventional tillage. It can be concluded that no-till increases microbial biomass in soil and subsequently enzymatic activities likely ascribed to an increased organic matter content. Under low availability of hydrocarbon sources in soil due to conventional tillage, which promotes a decrease in the organic matter content of the soil, populations of oligotrophods and the diversity of microbial communities are increased. Under these conditions, there must not be dominant carbon sources promoting the selection of microorganisms with a given physiological profile. The reduced hydrocarbon availability and the higher diversity contribute to explain the increased use of carbon sources used in Biolog with conventional tillage than with no-till.

Delgado, A.; de Santiago, A.; Avilés, M.; Perea, F.

2012-04-01

371

INFLUENCE OF ORGANIC MATTER ON THE ESTIMATION OF SATURATED HYDRAULIC CONDUCTIVITY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Estimation of soil hydraulic properties by pedotransfer functions (PTFs) can be used in many applications. Some of existing PTFs estimate saturated hydraulic conductivity (Ks) of the soil, using organic matter (OM) content as one of the input variables. Several authors have shown an increase in Ks w...

372

Joint estimation of soil moisture profile and hydraulic parameters by ground-penetrating radar data assimilation with maximum likelihood ensemble filter  

NASA Astrophysics Data System (ADS)

Ground-Penetrating Radar (GPR) has recently become a powerful geophysical technique to characterize soil moisture at the field scale. We developed a data assimilation scheme to simultaneously estimate the vertical soil moisture profile and hydraulic parameters from time-lapse GPR measurements. The assimilation scheme includes a soil hydrodynamic model to simulate the soil moisture dynamics, a full-wave electromagnetic wave propagation model, and petrophysical relationship to link the state variable with the GPR data and a maximum likelihood ensemble assimi