Note: This page contains sample records for the topic hydraulic properties soil from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

75: Determining Soil Hydraulic Properties  

Microsoft Academic Search

Hydraulic properties are required for modeling water and solute transport in unsaturated soils. The bottleneck for the successful application of numerical simulation models lays usually in their parameter estimation requirements. Methods to determine hydraulic properties can be classified into indirect and direct approaches. Indirect methods encompass the estimation of hydraulic properties by pedotransfer functions from more easily measured soil properties,

WOLFGANG DURNER; KAI LIPSIUS

2005-01-01

2

Land Use Effects on Soil Hydraulic Properties  

Microsoft Academic Search

Tillage alters the pore structure and hydraulic properties of soils. Likewise, reestablishment of grass on cropland will, over time, produce changes in soil hydraulic properties that can influence the amount of plant available water. We conducted a study to characterize and compare soil hydraulic properties on adjacent native grassland, cropland, and Conservation Reserve Program (CRP) sites at three locations in

R. C. Schwartz; P. W. Unger; S. R. Evett

3

Methods for Determination of soil Hydraulic Properties  

Microsoft Academic Search

The results of different procedures for the determination of soil hydraulic properties (soil-water retention and unsaturated hydraulic conductivity curves) are presented. Tests were performed for three uniform sandy soils at adjacent sites. Differences in results from the various tests are attributable to a number of factors including volume of soil tested, test conditions, dimensionality of imposed flow, method of analysis,

Radka Kodešová; Molly M. Gribb

4

Comparing Conventional and Inverse Methods for Determining Soil Hydraulic Properties  

Microsoft Academic Search

Models describing water and transport processes in the vadose zone require information on soil hydraulic properties. Currently there exist many laboratory, field and analytical methods to determine the highly non-linear relations between soil water content, soil water conductivity and soil water pressure head. This paper presents results of the comparison of three different methods, used to determine the soil hydraulic

Farkas Cs

5

Fractal models for predicting soil hydraulic properties: a review  

Microsoft Academic Search

Modern hydrological models require information on hydraulic conductivity and soil-water retention characteristics. The high cost and large spatial variability of measurements makes the prediction of these properties a viable alternative. Fractal models describe hierarchical systems and are suitable to model soil structure and soil hydraulic properties. Deterministic fractals are often used to model porous media in which scaling of mass,

D. Giménez; E. Perfect; W. J. Rawls; Ya. Pachepsky

1997-01-01

6

Effect of Application of Surfactants on Hydraulic Properties of Soils  

Microsoft Academic Search

This study explores the effect of surfactants, commonly found in detergents, on the hydraulic properties of soils. The soil properties examined included hydraulic conductivity, infiltration characteristics, and effective suction at the wetting front, capillary rise and soil penetrability. Two agricultural soils—a loam and a sandy loam, and three surfactants—one anionic surfactant (Sulphonic) and two non-ionic surfactants (Rexol and Rexonic), were

M. Abu-Zreig; R. P. Rudra; W. T. Dickinson

2003-01-01

7

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...

8

Variation of Desert Soil Hydraulic Properties with Pedogenic Maturity  

NASA Astrophysics Data System (ADS)

Older alluvial desert soils exhibit greater pedogenic maturity, having more distinct desert pavements, vesicular (Av) horizons, and more pronounced stratification from processes such as illuviation and salt accumulation. These and related effects strongly influence the soil hydraulic properties. Older soils have been observed to have lower saturated hydraulic conductivity, and possibly greater capacity to retain water, but the quantitative effect of specific pedogenic features on the soil water retention or unsaturated hydraulic conductivity (K) curves is poorly known. With field infiltration/redistribution experiments on three different-aged soils developed within alluvial wash deposits in the Mojave National Preserve, we evaluated effective hydraulic properties over a scale of several m horizontally and to 1.5 m depth. We then correlated these properties with pedogenic features. The selected soils are (1) recently deposited sediments, (2) a soil of early Holocene age, and (3) a highly developed soil of late Pleistocene age. In each experiment we ponded water in a 1-m-diameter infiltration ring for 2.3 hr. For several weeks we monitored subsurface water content and matric pressure using surface electrical resistance imaging, dielectric-constant probes, heat-dissipation probes, and tensiometers. Analysis of these data using an inverse modeling technique gives the water retention and K properties needed for predictive modeling. Some properties show a consistent trend with soil age. Progressively more developed surface and near-surface features such as desert pavement and Av horizons are the likely cause of an observed consistent decline of infiltration capacity with soil age. Other properties, such as vertical flow retardation by layer contrasts, appear to have a more complicated soil-age dependence. The wash deposits display distinct depositional layering that has a retarding effect on vertical flow, an effect that may be less pronounced in the older Holocene soil, where the original depositional structure has a relatively modest influence. Anisotropy at the scale of centimeters is of major importance in the Pleistocene soil, with developed horizons that tend to hold water within about 0.5 m of the surface for a longer duration than in the two younger soils. Correlation of these and related pedogenic features with soil hydraulic properties is a first step toward the estimation of effective hydraulic properties of widely varying Mojave Desert soils, as needed for large-scale evaluation of soil moisture dynamics in relation to ecological habitat quality.

Nimmo, J. R.; Perkins, K. S.; Mirus, B. B.; Schmidt, K. M.; Miller, D. M.; Stock, J. D.; Singha, K.

2006-12-01

9

Modeling soil hydraulic properties for a wide range of soil conditions  

Microsoft Academic Search

This paper presents equations for estimating soil hydraulic properties such as bulk density (Db), field capacity (FC), permanent wilting point (PWP), and saturated hydraulic conductivity (Ksat) from soil composition (sand, silt, clay, organic matter, coarse fragments), and with increasing soil depth, for a wide range of natural soil types and conditions. The equations, derived from New Brunswick and Nova Scotia

Vincent Balland; Joseph A. P. Pollacco; Paul A. Arp

2008-01-01

10

Laboratory-field scaling of soil hydraulic properties: numerical validation based on soil water content measurements  

Microsoft Academic Search

Hydraulic properties should be determined at the scale of the process modeled. The methods to hydraulically characterize a soil in situ remain extremely difficult to implement, needing measurements of water content and pressure head with adequate time-depth resolution. The authors recently proposed a method of scaling, physically based, that allows to obtain the field soil hydraulic parameters from the laboratory

Antonello Bonfante; Antonio Coppola; Angelo Basile

2010-01-01

11

Hydraulic properties of fen peat soils in Poland  

Microsoft Academic Search

The hydraulic properties of fen peat soils from the Biebrza River Valley in the north-east of Poland were investigated. 87 soil samples were collected from nine typical peat-moorsh soil profiles representing three types of peat: moss with fibrous structure, herbaceous and wooden peat characterised by amorphous structure with high humus content. The multi-step outflow method was used to determine the

Tomasz Gnatowski; Jan Szaty?owicz; Tomasz Brandyk; Cedric Kechavarzi

2010-01-01

12

A new model for soil hydraulic properties based on a stochastic conceptualization of porous media  

Microsoft Academic Search

The nature and distribution of soil particles and pores plays a strong role in determining the soil hydraulic properties (specifically the soil water retention curve and the relative hydraulic conductivity curve) that govern water movement. A new mathematical model for these hydraulic properties was developed by conceptualizing the soil as a random assemblage of soil particles represented by randomly sized

T. P. Chan; R. S. Govindaraju

2003-01-01

13

LANDSCAPE AND CONSERVATION MANAGEMENT EFFECTS ON HYDRAULIC PROPERTIES ON A CLAYPAN-SOIL TOPOSEQUENCE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Information on effects of landscape and its interaction with management on soil hydraulic properties is scarce. This study investigated effects and interactions of landscape position and conservation management systems on soil bulk density, saturated hydraulic conductivity (Ksat), soil water retenti...

14

Effect of soil compaction on hydraulic properties of two loess soils in China  

Microsoft Academic Search

Soil compaction affects hydraulic properties, and thus can lead to soil degradation and other adverse effects on environmental quality. This study evaluates the effects of three levels of compaction on the hydraulic properties of two silty loam soils from the Loess Plateau, China. Undisturbed soil cores were collected from the surface (0–5cm) and subsurface (10–15cm) layers at sites in Mizhi

Shulan Zhang; Harald Grip; Lars Lövdahl

2006-01-01

15

Impact of land management on soil structure and soil hydraulic properties  

Microsoft Academic Search

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

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

2010-01-01

16

DIVISION S-1—SOIL PHYSICS Estimating Soil Hydraulic Properties During Constant Flux Infiltration: Inverse Procedures  

Microsoft Academic Search

ment of water and chemicals into and through the unsat- urated zone. These models have become indispensable There is a need for accurate and cost-effective methods to estimate tools for quantifying and integrating transport processes the hydraulic properties of soils. Past work indicated measurements of a single hydraulic response will not necessarily result in unique in the unsaturated soil zone.

B. C. Si; R. G. Kachanoski

17

Using IR-measured soil surface temperatures to estimate hydraulic properties of the top soil layer  

Microsoft Academic Search

The temporal and spatial development of soil surface temperatures (SST) depends on water availability in the near-surface soil layer. Since the soil loses latent heat during evaporation and water available for evaporation depends on soil hydraulic properties (SHP), the temporal variability of SST should contain information about the near-surface SHP. This study was conducted to investigate the information content of

Christian Steenpass; Jan Vanderborght; Michael Herbst; Jirka Simunek; Harry Vereecken

2010-01-01

18

Field measurement of soil surface hydraulic properties by disc and ring infiltrometers  

Microsoft Academic Search

Soil management influences physical properties and mainly the soil hydraulic functions. Their measurement becomes one of the research preferences in this branch of applied soil science. Tension disc and pressure ring infiltrometers have become very popular devices for the in situ estimates of soil surface hydraulic properties. Their use for measuring solute–water transfer parameters of soils is now well established

Rafael Angulo-Jaramillo; Jean-Pierre Vandervaere; Stéphanie Roulier; Jean-Louis Thony; Jean-Paul Gaudet; Michel Vauclin

2000-01-01

19

Sensitivity of tile drainage flow and crop yield on measured and calibrated soil hydraulic properties  

Microsoft Academic Search

Process-based agricultural system 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 variability in measured soil hydraulic properties and to compare simulation results using measured and default soil parameters. To do so, we measured soil water retention curves and saturated soil

L. Ma; R. W. Malone; P. Heilman; L. R. Ahuja; T. Meade; S. A. Saseendran; J. C. Ascough II; R. S. Kanwar

2007-01-01

20

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

Microsoft Academic Search

Many applications involving variably saturated flow and transport require estimates of the unsaturated soil hydraulic properties. Nu- merical inversion of cumulative infiltration data during transient flow, complemented with initial or final soil water content data, is an in- creasinglypopular approach for estimating the hydraulic curves. In this study, we compared Mualem-van Genuchten (MVG) soil hydraulic parameters obtained from direct laboratory

T. B. Ramos; M. C. Gonçalves; J. C. Martins; M. Th. van Genuchten; F. P. Pires

2006-01-01

21

Hydraulic Properties in a Silt Loam Soil under Natural Prairie, Conventional Till, and No-Till  

Microsoft Academic Search

undergo this dramatic cyclic change in soil structure; although seasonal variations in hydraulic conductivities Tillage in the Palouse region of Washington State over the past occur through root development, earthworm activity, 100 yr has influenced the soil physical and biological properties. In particular, hydraulic properties are significantly affected by soil culti- and other natural processes such as freezing and thaw-

Juan P. Fuentes; Markus Flury; David F. Bezdicek

2004-01-01

22

Soil hydraulic properties of two loess soils in China measured by various field-scale and laboratory methods  

Microsoft Academic Search

Knowledge of hydraulic properties is essential for understanding water movement in soil. However, very few data on these properties are available from the Loess Plateau of China. We determined the hydraulic properties of two silty loam soils on agricultural land at sites in Mizhi and Heyang in the region. Undisturbed soil cores were collected from seven layers to one meter

Shulan Zhang; Lars Lövdahl; Harald Grip; Yanan Tong

2007-01-01

23

Soil hydraulic properties near saturation, an improved conductivity model  

Microsoft Academic Search

The hydraulic properties near saturation can change dramatically due to the presence of macropores that are usually difficult to handle in traditional pore size models. The purpose of this study is to establish a data set on hydraulic conductivity near saturation, test the predictive capability of commonly used hydraulic conductivity models and give suggestions for improved models. Water retention and

Christen D. Børgesen; Ole H. Jacobsen; Søren Hansen; Marcel G. Schaap

2006-01-01

24

Analysing problems in describing field and laboratory measured soil hydraulic properties  

Microsoft Academic Search

Accurate in situ determination of unsaturated soil hydraulic properties is often not feasible becauseof natural variability of most field soils, and because of instrumental limitations. Therefore the soilhydraulic properties are often measured in the laboratory, or derived by computer models using simplestandard laboratory methods.This paper analyses problems in describing field hydraulic properties of a Ap horizon of a siltyloam, basing

G. Wessolek; R. Plagge; F. J. Leijb; M VANGENUCHTEN

1994-01-01

25

IN-SITU CHARACTERIZATION OF UNSATURATED SOIL HYDRAULIC PROPERTIES OF A LATERITE SOIL PROFILE IN COASTAL KARNATAKA  

Microsoft Academic Search

Unsaturated laterite soil formations play an important hydrologic role in the West Coast region of India. However, very little information on the hydraulic\\/hydrologic properties of lateritic soils exists in literature. The present study was taken up to characterize the unsaturated soil water retention curves and hydraulic conductivity function of a sandy lateritic soil profile located in the coastal district of

Lakshman Nandagiri; S. B. Bore Gowda; Amba Shetty

2006-01-01

26

Determination of Soil Hydraulic Properties Using Magnetic Resonance Techniques and Classical Soil Physics Measurements  

NASA Astrophysics Data System (ADS)

Water and solute movement as any other transport processes through soil are influenced by the hydraulic properties of the soils. The heterogeneities of the soils imply heterogeneous spatial distribution of the hydraulic properties leading to heterogeneous distribution of soil water content. This may affects the water availability for plant growth, the groundwater contamination and nutrients losses within the root zone. The measurement techniques available today for the estimation of soil hydraulic parameters do not account for the heterogeneity of the sample and treat each measurement sample as a homogeneous representative volume. On the other side natural soils contain large heterogeneities mostly in terms of inclusions of different materials. Therefore the purpose of this study is to estimate soil hydraulic properties of a heterogeneous sample by combining classical multi-step-outflow (MSO) with magnetic resonance imaging (MRI) experiments. MSO experiments were performed on a sample filled with sand and sand-clay mixture in a coaxial structure. During each pressure application MRI images at 4.7 T (200 MHz) were recorded using a pure phase-encoding MRI sequence in order to provide information about the soil water content at specific locations within the coaxial sample. The recorded cumulative outflow and water content data were used as input data in the inversion of the MSO experiment. For the simulation and inversion of the MSO experiment we used the hydrological model HYDRUS-2D3D in which the initial hydraulic parameters of the two materials were estimated based on CPMG-T2 relaxation measurements on homogeneous sub-samples. The results show conclusively that the combination of the two MRI and MSO methods leads to a unique estimation of the hydraulic properties of two materials simultaneously.

Stingaciu, Laura R.; Weihermüller, Lutz; Pohlmeier, Andreas; Stapf, Siegfried; Vereecken, Harry

2011-03-01

27

Effects of agricultural practices on hydraulic properties and water movement in soils in Brittany (France)  

Microsoft Academic Search

The intensive agricultural use of soils in the Brittany region (western France) has increased the need for a better understanding of soil water dynamics. The aim of the present study is to compare quantitatively the differences produced by two agricultural practices on soil hydraulic properties (water retention curve and hydraulic conductivity) as well as the infiltration and drainage fluxes in

Babacar Ndiaye; Jérôme Molénat; Vincent Hallaire; Chantal Gascuel; Yannick Hamon

2007-01-01

28

Estimating Hydraulic Properties of a Fine-textured Soil Using a Disc Infiltrometer  

Microsoft Academic Search

This infiltration-based method is particularly suitable for quantifying changes in near surface hydrology resulting Inverse optimization of parameters offers an economical means to from soil management activities such as tillage (Sauer infer soil hydraulic properties from in situ measurements of infiltra- tion. We evaluated optimization strategies to inversely estimate soil et al., 1990; Logsdon et al., 1993). Although unconfined hydraulic

R. C. Schwartz; S. R. Evett

2002-01-01

29

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

30

Effects of Soil Morphology on Hydraulic Properties: II. Hydraulic Pedotransfer Functions  

Microsoft Academic Search

years as an approach to translate simple soil characteristics found in soil surveys into more complicated model input parameters. However, However, existing pedotransfer functions have not yet existing pedotransfer functions have not yet incorporated critical soil incorporated critical soil structural information such as structural information. This study showed that soil hydraulic proper- pedality and macroporosity. This, in part, may be

H. S. Lin; K. J. McInnes; L. P. Wilding; C. T. Hallmark

31

Using Remotely-Sensed Estimates of Soil Moisture to Infer Spatially Distributed Soil Hydraulic Properties  

NASA Astrophysics Data System (ADS)

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 unsaturated (vadose) zone of the soil are not easy to estimate or predict because of the difficulty in accurately representing soil texture and hydraulic properties in land surface and hydrologic models. This study approaches the problem of parameterizing soils from a unique perspective based on components originally developed for semi-operational estimation of soil moisture for vehicle mobility assessments. Estimates of 0-5 cm soil moisture derived from radar imagery were acquired over the Walnut Gulch watershed in Arizona. The resultant fields of soil moisture were then used to calibrate a land surface model and infer information on the soil hydraulic properties of the region. Specifically, a well-established parameter estimation routine was incorporated into the Noah land surface model, and run at very high spatial resolutions during the Monsoon 90 field experiment. Optimizations of sand, clay, and silt percentages for each soil type were then related to specific hydraulic parameters using pedotransfer functions. By estimating a more continuous range of widely applicable soil properties such as sand and clay percentages, rather than prescribing soil texture classes or attempting multi-objective optimizations over large parameter sets as in previous studies, the accuracy and consistency of the resulting properties could be more easily assessed. In addition, the strong influence of temporal and spatial patterns in precipitation is addressed, and the methodology is tested using a more recent radar-based soil moisture product and independent dataset at Walnut Gulch. Overall, results demonstrate the potential for this method to gain physically meaningful information on soil properties given limited microwave retrievals from remote sensing.

Santanello, J. A.; Peters-Lidard, C.; Garcia, M.; Mocko, D.

2006-05-01

32

Soil hydraulic properties of cropland compared with reestablished and native grassland  

Microsoft Academic Search

Conversion of cropland to perennial grasses will, over time, produce changes in soil hydraulic properties. The objective of this study was to characterize and compare hydraulic properties of fine-textured soils on adjacent native grassland, recently tilled cropland, and reestablished grassland in the Conservation Reserve Program (CRP) at three locations in the Southern Great Plains. A tension infiltrometer was used to

Robert C. Schwartz; Steven R. Evett; Paul W. Unger

2003-01-01

33

Estimation of depth averaged unsaturated soil hydraulic properties from infiltration experiments  

Microsoft Academic Search

Soil hydraulic properties determined from laboratory experiments often are non-representative of field conditions. An inverse method was developed to estimate hydraulic properties of unsaturated uniform soil from intermediate- and field-scale infiltration data, where there is no significant preferential flow during the infiltration experiment. Four parameters, (?, n, Ks and ?r) in van Genuchten's model were estimated by numerical inversion of

Z.-Y Zou; M. H Young; Z Li; P. J Wierenga

2001-01-01

34

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...

35

Lognormal distribution model for unsaturated soil hydraulic properties  

Microsoft Academic Search

The soil water retention model developed by Kosugi was modified to be compatible with Mualem's model in order to derive an analytical expression for the relative hydraulic conductivity Kr. The modified water retention model is to be derived by applying a lognormal distribution law to the soil pore radius distribution function. Parameters of this retention model have physical significance on

Ken'ichirou Kosugi

1996-01-01

36

Unimodal and Bimodal Descriptions of Hydraulic Properties for Aggregated Soils  

Microsoft Academic Search

are often advantageously represented through analyti- cal expressions in which there are parameters to be This study was conducted to investigate the capability of bimodal defined with reference to the soils in question (van Gen- approaches in describing water retention data and predicting hydraulic uchten and Nielsen, 1985; Bruce and Luxmoore, 1986; conductivity of 18 samples from an aggregated soil.

Antonio Coppola

2000-01-01

37

Lognormal Distribution Model for Unsaturated Soil Hydraulic Properties  

Microsoft Academic Search

The soil water retention model developed by Kosugi was modified to be compatible with Mualem's model in order to derive an analytical expression for the relative hydraulic conductivity Kr. The modified water retention model is to be derived by applying a lognormal distribution law to the soil pore radius distribution function. Parameters of this retention model have physical significance on

Ken'ichirou Kosugi

1996-01-01

38

Errors in water retention curves determined with pressure plates and their effect on soil hydraulic properties  

Microsoft Academic Search

Pressure plates are commonly used to measure the soil water retention curve. Low plate and soil conductance, lack of plate-soil contact, and soil dispersion, however, make this method often unreliable at low water potentials. In this paper, we investigate how errors in the determination of the water retention curve affect the soil hydraulic properties and the computation of plant available

M. Bittelli; M. Flury

2009-01-01

39

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

40

Testing an Infiltration Method for Estimating Soil Hydraulic Properties in the Laboratory  

Microsoft Academic Search

uniqueness of the solution may be in question. Recent application of neural network analysis to estimate soil Solving soil unsaturated flow problems requires knowledge of the hydraulic properties showed that artificial neural net- water retention, (h ), and unsaturated hydraulic conductivity, K(), works were generally efficient, especially when data were relationships. The purpose of this study was to adapt to

L. Bruckler; P. Bertuzzi; R. Angulo-Jaramillo; S. Ruy

2002-01-01

41

Hydraulic properties of soils derived from marine sediments of Cyprus  

Microsoft Academic Search

Laboratory soil-water characteristic curves (SWCCs) were obtained for compacted marine soils of different lithologies and genesis taken from three different locations in North Cyprus. van Genuchten's model was used to determine the best fit for the laboratory data of the SWCC, and indirect predictions of hydraulic conductivity and diffusivity functions were obtained using the closed-form solution of van Genucten–Mualem's model.

Huriye Bilsel

2004-01-01

42

Soil hydraulic properties in one-dimensional layered soil profile using layer-specific soil moisture assimilation scheme  

NASA Astrophysics Data System (ADS)

We developed a layer-specific soil-moisture assimilation scheme using a simulation-optimization framework, Soil-Water-Atmosphere-Plant model with genetic algorithm (SWAP-GA). Here, we explored the quantification of the soil hydraulic properties in a layered soil column under various combinations of soil types, vegetation covers, bottom boundary conditions and soil layering using idealized (synthetic) numerical studies and actual field experiments. We demonstrated that soil layers and vertical heterogeneity (layering arrangements) could impact to the uncertainty of quantifying soil hydraulic parameters. We also found that, under layered soil system, when the subsurface flows are dominated by upward fluxes, e.g., from a shallow water table, the solution to the inverse problem appears to be more elusive. However, when the soil profile is predominantly draining, the soil hydraulic parameters could be fairly estimated well across soil layers, corroborating the results of past studies on homogenous soil columns. In the field experiments, the layer-specific assimilation scheme successfully matched soil moisture estimates with observations at the individual soil layers suggesting that this approach could be applied in real world conditions.

Shin, Yongchul; Mohanty, Binayak P.; Ines, Amor V. M.

2012-06-01

43

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

44

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...

45

Unbiased simultaneous estimation of soil hydraulic properties and dynamic nonequilibrium parameters from transient outflow experiments  

NASA Astrophysics Data System (ADS)

Simulation of variably saturated water flow in soils requires accurate knowledge of soil hydraulic properties. Transient flow experiments like the multistep outflow and evaporation methods are now routinely applied to determine soil hydraulic parameters by inverse modelling. Recent experimental evidence suggests that the water content dynamics during such flow experiments is subject to dynamic non-equilibrium. The extent to which this affects the accuracy of determining the equilibrium soil hydraulic properties is still unknown. Conversely, any bias in the equilibrium soil hydraulic properties caused by an inappropriate parameterization must be expected to lead to biased estimates of the parameters describing the hydraulic non-equilibrium. We coupled a dual porosity non-equilibrium model which combines the Richards equation and the Ross and Smettem approach for non-equilibrium with a free-form inversion algorithm. The free-form method has been shown before to guarantee an unbiased estimation of soil hydraulic properties. The freeform non-equilibrium estimation method was applied to data from various multistep outflow experiments. The results confirm that errors in the parameterization of the soil hydraulic properties cause biased estimates of non-equilibrium parameters. Such bias can be minimized or even eliminated with the free-form approach.

Iden, S. C.; Diamantopoulos, E.; Durner, W.

2012-04-01

46

Determining soil hydraulic properties from infiltration experiments monitored with time domain reflectometry  

Microsoft Academic Search

Experimental methods are needed to determine the spatial variability of soil hydraulic properties within a field plot in acceptable time. Vertically installed Time Domain Reflectometry (TDR) probes have been used during constant flux and constant head infiltration experiments to determine hydraulic properties. Because these studies only determined cumulative water storage or depth to the wetting front from the TDR measurements,

J. A. Huisman; L. Weihermüller; H. Vereecken

2009-01-01

47

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

48

Time-variable soil hydraulic properties in near-surface soil water simulations for different tillage methods  

Microsoft Academic Search

Simulating near-surface soil water dynamics is challenging since this soil compartment is temporally highly dynamic as response to climate and crop growth. For accurate simulations the soil hydraulic properties have to be properly known. Although there is evidence that these properties are subject to temporal changes, they are set constant over time in most simulations studies. The objective of this

Andreas Schwen; Gernot Bodner; Willibald Loiskandl

2011-01-01

49

Hydraulic properties of typical salt-affected soils in Jiangsu Province, China  

Microsoft Academic Search

Every year about 1,500 ha of land is reclaimed from the sea along the coastline of Jiangsu Province, China. It is important\\u000a to characterize the hydraulic properties of this reclaimed land to be able to predict and manage salt and water movement for\\u000a amelioration of these saline soils. In this paper, we report hydraulic properties of these salt-affected soils. The

Xiaomin Chen; Qirong Shen; Yangchun Xu

2007-01-01

50

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...

51

Effects of coarse-grained material on hydraulic properties and shear strength of top soil  

Microsoft Academic Search

Sidewalk failures associated with top soil of low shear strength are a common problem in urban areas. Mixing top soil with granite chips can be used to increase its permeability and shear strength. The effects of mixing granite chips with top soils on the hydraulic properties and shear strength under saturated and unsaturated conditions were investigated in this study. The

H. Rahardjo; I. G. B. Indrawan; E. C. Leong; W. K. Yong

2008-01-01

52

A comparison of land surface model soil hydraulic properties estimated by inverse modeling and pedotransfer functions  

Microsoft Academic Search

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

Ethan D. Gutmann; Eric E. Small

2007-01-01

53

Field determination of soil hydraulic properties for simulation of the optimum watertable regime  

Microsoft Academic Search

A field experiment to evaluate accurate cost and time efficient methodologies for determining soil hydraulic properties was done at the NIAB Research Station at Faisalabad, Pakistan. The experiment was performed on a freely draining loamy soil. This soil type is representative of 75% of the topsoil in a tile drainage area known as the Fourth Drainage Project. Redistribution of water

Muhammad Ashraf Moghal; Jelle Beekma; Wouter Beekman; Javed Akhter

1993-01-01

54

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...

55

Free-form estimation of the unsaturated soil hydraulic properties by inverse modeling using global optimization  

Microsoft Academic Search

Inverse modeling is a powerful technique for identifying the hydraulic properties of unsaturated porous media. However, the selection of an appropriate parameterization of the soil water retention and hydraulic conductivity function remains a challenge. In this article, we present an improved algorithm for estimating these two relationships without assigning an a priori shape to them. The approach uses cubic Hermite

S. C. Iden; W. Durner

2007-01-01

56

TOPOGRAPHICAL ATTRIBUTES TO PREDICT SOIL HYDRAULIC PROPERTIES ALONG A HILLSLOPE TRANSECT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Basic soil properties have long been used to predict unsaturated soil hydraulic properties with pedotransfer function (PTFs). Implementation of such PTFs is usually not feasible for catchment-scale studies because of the experimental effort that would be required. On the other hand, topographical at...

57

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

Microsoft Academic Search

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

R. Khaleel; E. J. Freeman

1995-01-01

58

Estimating soil hydraulic properties from time series of remotely sensed and in-situ measured topsoil water contents  

Microsoft Academic Search

Soil hydraulic properties are needed in many applications. One of the most difficult quantities to assess is the hydraulic conductivity function. One reason for this is the influence of soil structure on the infiltration capacity. In this paper we present an approach to estimate the hydraulic properties based on time-series of water contents measured in the topsoil of an experimental

Christian Stamm; Katrin Schneeberger; Hannes Fluehler; Christian Maetzler

2003-01-01

59

Predicting unsaturated hydraulic conductivity of soil based on some basic soil properties  

Microsoft Academic Search

Soil hydraulic conductivity is a crucial parameter in modeling flow process in soils and deciding water management. In this study, by combining the non-similar media concept (NSMC) to the one-parameter model of Brooks and Corey, a new NSMC-based model for estimating unsaturated hydraulic conductivity of various soils was presented. The main inputs are soil bulk density, particle-size distribution, soil water

J Zhuang; K Nakayama; G. R Yu; T Miyazaki

2001-01-01

60

Ant burrow effects on water flow and soil hydraulic properties of Sparta sand  

Microsoft Academic Search

Macropores generally have a significant influence on soil hydrologic processes. Ants create large burrows that may function as macropores, thus creating a potential for rapid movement of water and water-soluble chemicals in soil. This study was conducted to characterize the impact of ant burrows on hydraulic properties of a Sparta sand (uncoated, mesic Typic Quartzipsamments), and to determine the potential

D. Wang; B. Lowery; J. M. Norman; K. McSweeney

1996-01-01

61

Andosols of Terceira, Azores: measurement and significance of soil hydraulic properties  

Microsoft Academic Search

The Azores Islands are of recent volcanic origin and their soils, classified as Andosols, have characteristics peculiar to their formation and constituents. Several other areas in the world, including parts of Europe, have Andosols, but their hydraulic properties are not well known. To improve understanding of the hydrologic behaviour of these soils, two experimental sites were selected for in situ

J. C. Fontes; M. C. Gonçalves; L. S. Pereira

2004-01-01

62

A MODEL TO PREDICT THE UNSATURATED HYDRAULIC CONDUCTIVITY FROM BASIC SOIL PROPERTIES  

Microsoft Academic Search

The relative hydraulic conductivity kr of unsaturated soils is typically obtained from their water retention curve (WRC). In this paper, the modified Kovács (MK) model developed to predict the WRC is combined with the Mualem model to predict the kr function using basic geotechnical properties of granular soils. The ensuing equations, which have been implemented into MATLAB, have been validated

Mamert Mbonimpa; Bruno Bussière

63

Estimating unsaturated soil hydraulic properties from laboratory tension disc infiltrometer experiments  

Microsoft Academic Search

Four tension disc infiltration experiments were carried out on a loamy soil in the laboratory for the purpose of estimating the unsaturated soil hydraulic properties. Sixteen tensiometers were installed in pairs at the following coordinate (r,z) positions: (10, 2.5), (10, 5), (10, 10), (15, 5), (15, 10), (15, 15), (15, 20), and (15, 30), where r represents the distance from

Jirí Simunek; Ole Wendroth; Martinus T. van Genuchten

1999-01-01

64

Estimating unsaturated soil hydraulic properties from laboratory tension disc infiltrometer experiments  

Microsoft Academic Search

Four tension disc infiltration experiments were carried out on a loamy soil in the laboratory for the purpose of estimating the unsaturated soil hydraulic properties. Sixteen tensiometers were installed in pairs at the following coordinate (r, z) positions: (10, 2.5), (10, 5), (10, 10), (15, 5), (15, 10), (15, 15), (15, 20), and (15, 30), where r represents the distance

Ji?í Šim?nek; Ole Wendroth; Martinus T. van Genuchten

1999-01-01

65

Estimating Soil Hydraulic Properties from Time Series of Remotely Sensed and In-situ Measured Topsoil Water Contents  

Microsoft Academic Search

Knowledge of soil hydraulic properties is important for many fields of meteorology, climatology or hydrology. These applications often require information on the soil properties over large areas. In this paper we present an approach to estimate the hydraulic properties based on time-series of water content measurements in the topsoil at the plot scale. The data base consists of series of

K. Schneeberger; C. Stamm; C. Maetzler; H. Fluehler

2003-01-01

66

Towards an improved database of soil hydraulic properties for The Netherlands  

NASA Astrophysics Data System (ADS)

Soil hydraulic functions underpin many results of research for advise on environmental policy in The Netherlands. Examples include numerical simulations of the leaching of pesticides, nitrate and phosphate, the drying of natural areas due to the lowering of groundwater levels to benefit the agricultural sector, and of the soil water storage capacity in agricultural land and natural areas. Since the 1980s, the Staring series (Wösten et al. 1987, 1994, 2001) is used as the source of information for soil hydraulic functions of soils in The Netherlands. This database classifies soil hydraulic functions in groups of similar soil texture and organic matter content for topsoils and subsoils. Recent research has shown that the classification in the Staring series does not sufficiently differentiate soils with regard to their hydrological behaviour (Wesseling, 2009), and that there is an urgent need for the improvement of the measurement, functional description, and documentation of soil hydraulic functions. The objective of this study was to evaluate the measurements, functional description and documentation of the soil hydraulic functions included in the Staring Series, and to give recommendations for improvement. The results show the measuring techniques applied in The Netherlands generally yield data for pressure heads between approx. -100 and -600 cm. Both the wet range (h > -100 cm) and the dry range (h < -600 cm) are not measured but generally estimated with the Mualem-Van Genuchten approximation by fitting a curve through the measured calues and extrapolating at the wet and dry ends, thus yielding a high uncertainty. The application of the Mualem-Van Genuchten equations appear to limit the quality of the fits It appears to be impossible to fit a ulti-curved line with these kinds of equations. Mathematical alternatives like cubical splines were demonstrated to offer a promising alternative. The study shows that the systematic documentation of basic properties of the soil horizons to which the soil hydraulic functions refer offers the possibility to select soil hydraulic functions from broader groups in soil classifications, like the one employed in the Staring Series. The study demonstrates the set-up and implementation of a new database for soil hydraulic properties for The Netherlands.

Wesseling, Jan; Vroon, Henk; Verzandvoort, Simone

2010-05-01

67

Long-term effects of restoration on soil hydraulic properties in revegetation-stabilized desert ecosystems  

NASA Astrophysics Data System (ADS)

Improving structure of soils found at 0-5 cm depth, and increasing the thickness of biological soil crusts are both associated with sand dune revegetation-stabilization in arid northwestern China. Since 1956, research on sand dune stabilization has included the use of straw chequer-boards to facilitate development of soil structure. One method to gauge the degree of stabilization is to compare undisturbed soil hydraulic properties, including water retention [h($\\theta$)] and hydraulic conductivity [K(h)] functions, with properties from stabilized sites of different ages. This study examined properties at five experimental sites of different ages since revegetation (51, 42, 34, 20 and 0 years). Saturated hydraulic conductivity (K s ) was determined in-situ from all five sites, and the h($\\theta$) curve was determined from samples collected from three sites. A significant negative correlation existed between K s and the clay, silt and organic matter contents. Differences in most van Genuchten parameters for h($\\theta$) were observed between the revegetated plots and the migrating sand dune area. Results of this long-term study show that changes in soil hydraulic properties and improvement in soil structure were associated with migrating dune stabilization.

Wang, X.-P.; Young, M. H.; Yu, Z.; Li, X.-R.; Zhang, Z.-S.

2007-12-01

68

Effect of biofilm on soil hydraulic properties: laboratory studies using xanthan as surrogate  

NASA Astrophysics Data System (ADS)

Many soil bacteria produce extracellular polymeric substances (EPS) in which they are embedded while residing in the porous matrix. EPS are often attached as a biofilm to both the bacteria cell and the soil particles. As a consequence, their influence on water flow through variably saturated porous media often cannot be neglected. While the influence of attached microbial biomass and EPS on saturated water flow has been studied extensively, its investigation for unsaturated flow in soils has found significantly less attention. The objective of this study was the quantification of the effect of biofilms on the unsaturated soil hydraulic properties. We determined the soil water retention and unsaturated hydraulic conductivity functions of biofilm-affected soils by using xanthan as an EPS surrogate. Evaporation experiments were conducted on two sandy soil materials. The amount of added xanthan was varied in 6 stages from zero to 0.25 %. Additional measurements of soil water retention using the dewpoint method closed the remaining gap from the evaporation method to air-dryness. The experimental data were evaluated by the simplified evaporation method of Schindler. The results show that the unsaturated hydraulic conductivity is reduced markedly by added xanthan and the shape of the soil water retention curve is alterated significantly for all stages of xanthan addition. The reduction in hydraulic conductivity is high enough to fully suppress stage-one evaporation for xanthan-sand mixtures. The water-holding capacity of the xanthan and the alteration of the effective pore size distribution explain these results.

Rosenkranz, H.; Iden, S. C.; Durner, W.

2012-04-01

69

Soil Hydraulic Property Uniqueness as Determined From Inverse Modeling Using Surface Temperature : the Role of Soil Type  

Microsoft Academic Search

Knowledge of the spatial distribution of soil hydraulic properties (SHPs) is critical for a broad range of earth system problems, from predicting the hydrologic implications of climate variability to understanding how land cover and land use change modify water, energy, and carbon cycling at the earth's land surface. SHPs strongly control how water and energy flow through soils, and therefore

E. D. Gutmann; E. Small

2003-01-01

70

Continuous Flow Method for Rapid Measurement of Soil Hydraulic Properties: I. Experimental Considerations  

Microsoft Academic Search

nation with water flux and\\/or soil water pressure mea- surements to identify parameters of (h) and K(h )b y Soil hydraulic properties are important in many vadose zone pro- a least-squares numerical iteration. An attractive advan- cesses, but the measurement of these properties is usually tedious and often difficult. We describe a continuous flow method that allows very tage of

G. L. Butters; P. Duchateau

2002-01-01

71

Estimation of soil hydraulic properties using proximal spectral reflectance in visible, near-infrared, and shortwave-infrared (VIS–NIR–SWIR) region  

Microsoft Academic Search

Characterization of soil hydraulic properties is an important step for assessing soil water regime in agricultural fields. Because direct measurement of soil hydraulic properties at multiple locations is costly and time-consuming, pedotransfer functions (PTF) are conveniently used to estimate these properties from easily measurable basic soil properties. Over the last two decades, several studies have demonstrated that basic soil properties

Priyabrata Santra; Rabi Narayan Sahoo; Bhabani Sankar Das; Ravindra Nath Samal; Ajit Kumar Pattanaik; Vinod Kumar Gupta

2009-01-01

72

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

73

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

NASA Astrophysics Data System (ADS)

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, K. S.; Nimmo, J. R.; Medeiros, A. C.

2012-03-01

74

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

75

Estimation of effective soil hydraulic properties at field scale via ground albedo neutron sensing  

NASA Astrophysics Data System (ADS)

Upscaling of soil hydraulic parameters is a big challenge in hydrological research, especially in model applications of water and solute transport processes. In this contest, numerous attempts have been made to optimize soil hydraulic properties using observations of state variables such as soil moisture. However, in most of the cases the observations are limited at the point-scale and then transferred to the model scale. In this way inherent small-scale soil heterogeneities and non-linearity of dominate processes introduce sources of error that can produce significant misinterpretation of hydrological scenarios and unrealistic predictions. On the other hand, remote-sensed soil moisture over large areas is also a new promising approach to derive effective soil hydraulic properties over its observation footprint, but it is still limited to the soil surface. In this study we present a new methodology to derive soil moisture at the intermediate scale between point-scale observations and estimations at the remote-sensed scale. The data are then used for the estimation of effective soil hydraulic parameters. In particular, ground albedo neutron sensing (GANS) was used to derive non-invasive soil water content in a footprint of ca. 600 m diameter and a depth of few decimeters. This approach is based on the crucial role of hydrogen compared to other landscape materials as neutron moderator. As natural neutron measured aboveground depends on soil water content, the vertical footprint of the GANS method, i.e. its penetration depth, does also. Firstly, this study was designed to evaluate the dynamics of GANS vertical footprint and derive a mathematical model for its prediction. To test GANS-soil moisture and its penetration depth, it was accompanied by other soil moisture measurements (FDR) located at 5, 20 and 40 cm depths over the GANS horizontal footprint in a sunflower field (Brandenburg, Germany). Secondly, a HYDRUS-1D model was set up with monitored values of crop height and meteorological variables as input during a four-month period. Parameter estimation (PEST) software was coupled to HYDRUS-1D in order to calibrate soil hydraulic properties based on soil water content data. Thirdly, effective soil hydraulic properties were derived from GANS-soil moisture. Our observations show the potential of GANS to compensate the lack of information at the intermediate scale, soil water content estimation and effective soil properties. Despite measurement volumes, GANS-derived soil water content compared quantitatively to FDRs at several depths. For one-hour estimations, root mean square error was estimated as 0.019, 0.029 and 0.036 m3/m3 for 5 cm, 20 cm and 40 cm depths, respectively. In the context of soil hydraulic properties, this first application of GANS method succeed and its estimations were comparable to those derived by other approaches.

Rivera Villarreyes, C. A.; Baroni, G.; Oswald, S. E.

2012-04-01

76

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

77

PARAMETER ESTIMATION OF SOIL HYDRAULIC PROPERTIES FROM TENSION INFILTROMETER DATA IN PORTUGAL  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mathematical models are increasingly used to address a broad range of variably-saturated flow and contaminant transport problems. Such simulations are generally based on numerical solutions of the Richards equation, which in turn require knowledge of the unsaturated soil hydraulic properties. These...

78

Temporal dynamics of soil hydraulic properties and the water-conducting porosity under different tillage  

Microsoft Academic Search

Soil hydraulic properties are subject to temporal changes as a response to both tillage and natural impact factors. As the temporal and spatial variability might exceed cultivation-induced differences, there is a need to better differentiate between those influence factors. Thus, the objective of the present study was to assess the impact of different tillage techniques – conventional (CT), reduced (RT),

Andreas Schwen; Gernot Bodner; Peter Scholl; Graeme D. Buchan; Willibald Loiskandl

2011-01-01

79

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 ...

80

A global multilevel coordinate search procedure for estimating the unsaturated soil hydraulic properties  

Microsoft Academic Search

We present a new inverse modeling procedure to characterize the hydraulic properties of partially saturated soils from soil moisture measurements during a natural transient flow experiment. The inversion of the governing one-dimensional Richards equation is carried out using the Global Multilevel Coordinate Search optimization algorithm in sequential combination with the local Nelder-Mead Simplex algorithm (GMCS-NMS). We introduce this optimization method

S. Lambot; M. Javaux; F. Hupet; M. Vanclooster

2002-01-01

81

Development and evaluation of closed-form expressions for hysteretic soil hydraulic properties  

Microsoft Academic Search

A concise representation of hysteretic soil hydraulic properties is given based on a combination of M. T. van Genuchten's (1980) parametric K-?-h model and P. S. Scott et al.'s (1983) empirical hysteresis model modified to account for air entrapment. The resulting model yields compact closed-form expressions for the hysteretic water retention curve ?(h) and soil water capacity C(h), as well

J. B. Kool; J. C. Parker

1987-01-01

82

Extended multistep outflow method for the accurate determination of soil hydraulic properties close to water saturation  

NASA Astrophysics Data System (ADS)

Multistep outflow experiments are a well-established method to determine soil hydraulic properties. In the medium pressure head range where the specific water capacity is sufficiently high, the method yields reliable results. However, in the pressure head range corresponding to conditions close to and at water saturation, the method suffers from considerable uncertainties, in particular with respect to the determination of the hydraulic conductivity function. This is caused by the insensitivity of the experimental design with respect to the saturated hydraulic conductivity Ks. It is therefore generally recommended to perform an additional percolation experiment in order to determine Ks. The disadvantages resulting from this are an increased experimental cost and the necessity to combine information from two different experiments. In the case treated in this study the latter bears the risk of data inconsistency. We present a new experimental design which combines a water saturated percolation with an unsaturated multistep outflow experiment in a consecutive manner. The saturated percolation resembles a falling-head experiment with an initial ponding of 2-4 cm of water at the soil surface. The onset of unsaturated flow can be identified unambiguously by pressure head measurements inside the sample. We test this extended multistep outflow method (XMSO) by inversions using synthetic and real laboratory data. The soil hydraulic properties are parameterized with free-form functions in order to avoid model errors in the constitutive relationships and to quantify robustly the uncertainties of determination close to water saturation. Our results confirm that the XMSO method allows to identify correctly the soil hydraulic properties in the pressure head range near and at water saturation. In particular, the saturated hydraulic conductivity can be determined without bias and with great accuracy. Because of the improved information content and since the experiment is quick to perform and evaluated easily by inverse modelling, it can replace the MSO design in future applications.

Iden, Sascha; Durner, Wolfgang

2010-05-01

83

Geostatistical co-regionalization of soil hydraulic properties in a micro-scale catchment using terrain attributes  

Microsoft Academic Search

Any effort of distributed hydrological modeling requires the spatially distributed input of soil hydraulic properties and soil thickness. Most of the hydrological models are sensitive concerning these soil properties, thus the use of point measurements and co-variables should be optimized for a most accurate spatial prediction. During this study, we focus on the use of terrain attributes as co-variables. In

M. Herbst; B. Diekkrüger; H. Vereecken

2006-01-01

84

Fire Induced Changes in Soil Structure: Implications for Soil Hydraulic Properties and Aeolian Suspension Potential in the Great Basin, USA  

NASA Astrophysics Data System (ADS)

Most studies on post-fire effects lack a true comparison to pre-fire conditions. The Upper Gleason controlled burn in a Pinus monophylla/Juniperus Osteosperma (single-leaf pinyon pine/Utah juniper) and Artemisia sp. (sagebrush) transition zone in east central Nevada (elevation range 2183 to 2397 m) was used to test hypotheses on how fire-induced changes in soil structure affect soil hydraulic and aeolian suspension properties. The area to be burned had moderate subangular blocky soil structure. However, where other controlled burns had been done nearby, this structure had collapsed into a structureless soil, rich in fine particles. Prior to the fire, a plot within the area to be burned and a control plot were established where soil samples were collected for bulk density, total C, and total organic C analyses; and a multi-disc tension infiltrometer and an air permeameter were used to measure saturated hydraulic conductivity (Ks) and air permeability (ka). Water drop penetration time (WDPT) was measured for detection of hydrophobic conditions, and a portable wind tunnel (PI-SWERLTM) was used to measure wind shear required to induce aeolian transport of fine particles. For both the soil hydraulic and aeolian transport properties, measurements were made in both intercanopy and undercanopy microsites. Thermocouples were buried at 0.10 m depth for point measurements of near surface soil temperature during the fire. The 470 hectare burn was conducted on 12 August 2009. Post-fire samples and measurements of the same soil property parameters are being made at the burned plot as well as in the control area. WDPT tests conducted one-week after the fire indicated slight water repellency at intercanopy sites. The soils most susceptible to aeolian erosion were on undercanopy sites that burned. Hypotheses include that 1) the fire will alter soil structure, increasing soil bulk density, and decreasing soil hydraulic conductivity and air permeability, a set of conditions that would increase the potential for soil erosion by water; and 2) the loss of soil structure will disaggregate soil material that would be more prone to suspension by wind at lower wind velocities compared to pre-burn conditions. The Upper Gleason fire caused uneven breakdown of the subangular structure on the surface. Additional changes in soil structure (e.g., compaction) may occur following other post-fire events such as heavy precipitation (rain or snowfall).

Shafer, D. S.; Dubois, D. W.; Chief, K.; Berli, M.; Miller, J. J.; Young, M.

2009-12-01

85

The effect of rock fragments on the hydraulic properties of soils  

SciTech Connect

Many soils contain rock fragments the sizes of which are much larger than the average pore size of the sieved soil. Due to the fact that these fragments are often fairly large in relation to the soil testing apparatus, it is common to remove them before performing hydrologic tests on the soil. The question then arises as to whether or not there is a simple way to correct the laboratory-measured values to account for the fragments, so as to arrive at property values that can apply to the soil in situ. This question has arisen in the surface infiltration studies that are part of the site characterization program at Yucca Mountain, where accurate values of the hydraulic conductivities of near-surface soils are needed in order to accurately estimate infiltration rates. Although this problem has been recognized for some time, and numerous review articles have been written there are as yet no proven models to account for the effect of rock fragments on hydraulic conductivity and water retention. In this report we will develop some simple physically-based models to account for the effects of rock fragments on gross hydrological properties, and apply the resulting equations to experimental data taken from the literature. These models are intended for application to data that is currently being collected by scientists from the USGS on near-surface soils from Yucca Mountain.

Zimmerman, R.W.; Bodvarsson, G.S.

1995-04-01

86

Dynamic non-equilibrium effects in soil hydraulic properties: experimental and modeling approach  

NASA Astrophysics Data System (ADS)

The knowledge of soil hydraulic properties along with the right understanding of the mechanisms which govern water retention and flow in soils is important in many soil hydrologic applications. Although we are able today to model and accurately predict water movement in soils for various scales and boundary conditions, questions about the theory for the description of hydraulic properties and the physics of water flow in soils still remain. One of these questions addresses the occurrence of "dynamic non-equilibrium effects" on water flow in porous media. The existence of these effects is known since the 1960s, and one of the evident effects of dynamic non-equilibrium is an apparent flow dependence of soil hydraulic properties. To investigate the occurrence and extent of dynamic effects in transient flow experiments, we conducted multistep outflow and evaporation experiments with flow interruptions. In the multistep outflow experiments, the non-equilibrium effects show up as a relaxation of the water content over time, while the pressure head profile is at hydrostatic equilibrium. In the evaporation experiments, non-equilibrium effects appear as a relaxation of the pressure head over time, while the macroscopic water content distribution appears static. Our results show that the concept of dynamic contact angle can be a significant contributing factor for this kind of effects in sandy soils. We developed a simple non-equilibrium model to quantitatively describe the observations. The model considers two continua at the macroscopic scale: one continuum is described by the Richards equation and the second, associated with non-equilibrium water flow, is described by an extended Richards equation using the Ross and Smettem non-equilibrium approach. We propose a superposition of these models with coupled water potential. It turns out that this model can describe the dynamic effects occurring in both multistep outflow and evaporation experiments.

Diamantopoulos, E.; Durner, W.

2011-12-01

87

Effect of soil hydraulic properties on the relationship between spatial variation and spatial mean of soil water contents  

NASA Astrophysics Data System (ADS)

Understanding soil moisture variability and its relationship with water content at various scales is a key issue in hydrological research. In this work we analyze this relationship by using the Monte-Carlo simulations of unsaturated flow in bare soils for eleven USDA textural classes. Parameters of the water retention characteristic and their spatial variability determine to a large extent the shape of the soil moisture variance-mean water content dependence. It was found that the Brooks-Corey parameter, which describes the pore size distribution of soils, controls the maximum value of the soil moisture standard deviation which varied in the range from 0.17 to 0.23 in simulations. Results of this work indicate the potential opportunity to estimate soil hydraulic properties and their variability from spatially distributed measurements of soil moisture content.

Martinez, Gonzalo; Pachepsky, Yakov A.; Vereecken, Harry

2013-04-01

88

Effect of Mineral Reactions on the Hydraulic Properties of Unsaturated Soils: Model Development and Application  

Microsoft Academic Search

Precipitation\\/dissolution induces changes in the pore radii of water-filled pores, and, consequently, affects flow in porous media. The selective radius shift model was developed to relate changes in mineral volume due to precipitation\\/dissolution reactions to changes in hydraulic properties of unsaturated soils. The model considers the dependency of the amount of mineral precipitation\\/dissolution within a pore on the local pore

L. C. Wissmeier; D. A. Barry

2008-01-01

89

Effective Hydraulic Properties Determined from Transient Unsaturated Flow in Anisotropic Soils  

SciTech Connect

Hydraulic parameters including the pore connectivity/tortuosity tensor (L_i) were inversely estimated using the STOMP numerical simulator coupled with the parameter estimation code, UCODE. Results show that six of eight parameters required for a modified van Genuchten-Mualem model could be inversely estimated using water content measured during transient infiltration from a surface line source and approximated prior information. Soils showed evidence of saturation-dependent anisotropy that was well described with the connectivity tensor. Variability of the vertical saturated hydraulic conductivity was larger than the horizontal. The autocorrelation ranges for the horizonatal and vertical Ks; the inverse of the air-entry value, and the horizontal connectivity were between 2.4 and 4.6 m whereas the van Genuchten shape parameter, n, and saturated water content showed no autocorrelation. Accurate upscaling of hydraulic properties requires the correct assessment of the connectivity of facies.

Ward, Andy L.; Zhang, Z. F.

2007-11-01

90

Hydraulic Property Determination of Vesiculated Soil Peds in Desert Pavement Environments  

NASA Astrophysics Data System (ADS)

Desert pavements are prominent features in arid and semi-arid environments, and can be found on a variety of landforms of significantly diverse ages ranging from Holocene to Tertiary. Desert pavements consist of a surface layer of closely packed gravel, typically one stone thick, that overlies a silt-rich vesicular A (Av) soil horizon. The vesicular horizon is composed of highly structured, prismatic soil peds, typically about 10 cm in diameter and less than 10 cm thick. Highly structured soils can greatly affect desert ecosystem development due to the impacts on local water balances. The concentration of silt and clay significantly reduces the infiltration rate and increases the water holding capacity, thereby reducing the penetration of wetting fronts. Field and laboratory studies were conducted to quantify the hydraulic properties of individual peds and pavement surfaces, and to ultimately use the information in a process-based evaluation of the soil moisture balance in arid environments. Field sites

Meadows, D. G.; Young, M. H.; Caldwell, T. G.; McDonald, E. V.

2003-12-01

91

Estimating unsaturated soil hydraulic properties from laboratory tension disc infiltrometer experiments  

NASA Astrophysics Data System (ADS)

Four tension disc infiltration experiments were carried out on a loamy soil in the laboratory for the purpose of estimating the unsaturated soil hydraulic properties. Sixteen tensiometers were installed in pairs at the following coordinate (r,z) positions: (10, 2.5), (10, 5), (10, 10), (15, 5), (15, 10), (15, 15), (15, 20), and (15, 30), where r represents the distance from the axis of symmetry and z is the location below the soil surface. A time domain reflectometry (TDR) probe was used to measure water contents at a depth of 2 cm directly below the tension disc. The first three experiments involved supply pressure heads at the disc of -20, -10, -5, and -1 cm, with the experiment lasting for ~5 hours. The same supply pressure heads were also used for the fourth experiment, which lasted 6.25 days so as to reach steady state at each applied tension. The measured data were analyzed using Wooding's [1968] analytical solution and by numerical inversion. The parameter estimation method combined a quasi three-dimensional numerical solution of the Richards equation with the Marquardt-Levenberg optimization scheme. The objective function for the parameter estimation analysis was defined using different combinations of the cumulative infiltrated volume, TDR readings, and tensiometer measurements. The estimated hydraulic properties were compared against results obtained with an evaporation experiment as analyzed with Wind's [1968] method. Water contents in the retention curves were underestimated when both transient and quasi steady state experiments were analyzed by parameter estimation. Unsaturated hydraulic conductivities obtained by parameter estimation and using Wooding's [1968] analysis corresponded well. Drying branches of the hydraulic conductivity function determined by parameter estimation also corresponded well with those obtained with the evaporation method.

Šim?nek, Ji?í; Wendroth, Ole; van Genuchten, Martinus T.

92

May We Identify The Spatial Variability of Soil Hydraulic Properties Based On Measurements With  

Microsoft Academic Search

A dynamic system left without external disturbances, will always tend to a stable equilibrium state that is consistent with the internal physics. For natural soils such an equilibrium state is reached when the gradients of the total hydraulic potential tend to zero. This statement is still valid for heterogeneous soils, because the hydraulic po- tential is an intensive state variable

E. Zehe; R. Becker; W. Schädel

2002-01-01

93

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

NASA Astrophysics Data System (ADS)

For monitoring the vadose zone, different strategies can be chosen, depending on the objectives and scale of observation. The effects of non-conventional water use on the vadose zone might produce impacts in porous media which could lead to changes in soil hydraulic properties, among others. Controlling these possible effects requires an accurate monitoring strategy that controls the volumetric water content, ?, and soil pressure, h, along the studied profile. According to the available literature, different monitoring systems have been carried out independently, however less attention has received comparative studies between different techniques. An experimental plot of 9x5 m2 was set with automatic and non-automatic sensors to control ? and h up to 1.5m depth. The non-automatic system consisted of ten Jet Fill tensiometers at 30, 45, 60, 90 and 120 cm (Soil Moisture®) and a polycarbonate access tube of 44 mm (i.d) for soil moisture measurements with a TRIME FM TDR portable probe (IMKO®). Vertical installation was carefully performed; measurements with this system were manual, twice a week for ? and three times per week for h. The automatic system composed of five 5TE sensors (Decagon Devices®) installed at 20, 40, 60, 90 and 120 cm for ? measurements and one MPS1 sensor (Decagon Devices®) at 60 cm depth for h. Installation took place laterally in a 40-50 cm length hole bored in a side of a trench that was excavated. All automatic sensors hourly recorded and stored in a data-logger. Boundary conditions were controlled with a volume-meter and with a meteorological station. ET was modelled with Penman-Monteith equation. Soil characterization include bulk density, gravimetric water content, grain size distribution, saturated hydraulic conductivity and soil water retention curves determined following laboratory standards. Soil mineralogy was determined by X-Ray difractometry. Unsaturated soil hydraulic parameters were model-fitted through SWRC-fit code and ROSETTA based on soil textural fractions. Simulation of water flow using automatic and non-automatic date was carried out by HYDRUS-1D independently. A good agreement from collected automatic and non-automatic data and modelled results can be recognized. General trend was captured, except for the outlier values as expected. Slightly differences were found between hydraulic properties obtained from laboratory determinations, and from inverse modelling from the two approaches. Differences up to 14% of flux through the lower boundary were detected between the two strategies According to results, automatic sensors have more resolution and then they're more appropriated to detect subtle changes of soil hydraulic properties. Nevertheless, if the aim of the research is to control the general trend of water dynamics, no significant differences were observed between the two systems.

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

2013-04-01

94

Using a modeling approach to predict soil hydraulic properties from passive microwave measurements  

Microsoft Academic Search

A soil water and energy budget model coupled with a microwave emission model (MICRO-SWEAT) was used to predict the diurnal courses of soil surface water content and microwave brightness temperatures during a number of drying cycles on soils of contrasting texture that were either cropped or bare. The parameters describing the soil water retention and conductivity characteristics [saturated hydraulic conductivity,

E. J. Burke; R. J. Gurney; L. P. Simmonds; P. E. O'Neill

1998-01-01

95

Effect of Aggregates Compaction in Soil Hydraulic Properties, due to Root Growth  

NASA Astrophysics Data System (ADS)

The rhizosphere is critical for soil-root interactions, however, physical processes within the soil around roots and implications of these processes, such as plant water and nutrient uptake, continue to raise questions. Soil compaction, due to root growth, results in favorable physical conditions in the rhizosphere to foster plant growth by providing aeration under wet conditions and improving water storage and flow toward the roots under dry conditions. In unsaturated conditions, the air transfer occurs through the macropores, while the water transfer occurs through the aggregates; providing the plant with these two vital elements, continuously. At the aggregate-scale, compaction gives connectivity within the aggregates. As the contact area between the aggregates increases, more water may be transfer to the plant. As result, the hydraulic conductivity of the rhizosphere may be higher than that at initial conditions (i.e., before compaction). This idea is important, as usually compaction is associated with decreasing water conductivity. This study focuses on understanding the role of roots to modify the soil, and in particular, their impact on rhizosphere hydraulic properties at the aggregate-scale. Using HYDRUS 3D, an aggregate system was modeled. It was found that the saturated hydraulic conductivity of the system increased following an S-shape as contact area increased due to compaction. This result differs from previous studies that assumed a quadratic relation. In addition, it was found that the compaction of big pores within the aggregates will be more beneficial for water extraction purposes, than the change in pore-size distribution within the aggregates due to compaction.

Aravena, J. E.; Tyler, S. W.; Berli, M.

2009-12-01

96

Comparison of three hydraulic property measurement methods  

Microsoft Academic Search

Hydraulic functions of soils may differ depending on the different measuring methods used. The performance of three different methods for measuring soil-hydraulic properties of a heterogeneous field were evaluated. The experiments were conducted using three different sizes of undisturbed soil cores collected systematically along a 31 m long transect of a well drained sandy loam soil having three soil horizons

Dirk Mallants; Diederik Jacques; Peng-Hsiang Tseng; Martinus Th. van Genuchten; Jan Feyen

1997-01-01

97

Consecutive combination of multistep outflow and evaporation method to determine soil hydraulic properties over a wide pressure head range  

NASA Astrophysics Data System (ADS)

Simulation of water flow in unsaturated soils requires accurate knowledge of the soil hydraulic properties. The two standard methods for the simultaneous determination of the water retention and hydraulic conductivity function in the laboratory are the multistep outflow and the evaporation method. The multistep outflow method provides data only in the pressure head range corresponding to relatively moist conditions, whereas the evaporation method has its highest information content in the medium to dry range. A comparison of both methods showed very similar results in the pressure head region where both provide reliable information on the soil hydraulic properties, but distinct differences become evident if results are extrapolated beyond this range. To obtain reliable estimates of soil hydraulic properties in a wider range of soil moisture, we propose to combine both methods in a consecutive manner. The combined experiment we present starts with a multistep outflow experiment which is directly followed by an evaporation experiment. We test this experimental design with both synthetic data and real laboratory experiments. In the evaluation of the combined experiment, data points for the retention and conductivity functions are calculated from the evaporation experiment and included into the objective function for the inverse simulation of the multistep outflow experiment. The combined evaluation leads to a greatly improved estimate of the hydraulic properties in a wide moisture range, circumvents the unreliable extrapolation beyond the different pressure head ranges of the separate experiments and significantly reduces the model error induced by such extrapolations.

Schelle, Henrike; Iden, Sascha C.; Durner, Wolfgang

2010-05-01

98

Characterization and prediction of spatial variability of unsaturated hydraulic properties in a field soil: Las Cruces, New Mexico  

SciTech Connect

A 91-m transect was set up in an irrigated field near Las Cruces, New Mexico to investigate the spatial variability of unsaturated soil properties. A total of 455 sampling points were monitored along a grid consisting of 91 stations placed 1 m apart by 5 depths per station. Post-irrigation soil water tension and water content measurements were recorded over 45 days at 11 time periods. The instantaneous profile was used to estimate the unsaturated hydraulic conductivity at the 455 sampling points. Fifty soil samples were also taken for analyzing sand, silt, and clay content distributions. The spatial and temporal variability of soil water tension and water content were investigated along with the spatial variability of parameters of an unsaturated hydraulic conductivity model. Results of the analysis show that spatial variation in soil water tension and water content is consistent with the soil texture spatial variability. In addition, the spatial distribution of the estimated parameter value of unsaturated hydraulic conductivity reflects the soil texture distribution. Using the statistics of the estimated hydraulic parameter values, a stochastic soil water tension model was employed to reproduce the variability of observed soil water tension. Although many assumptions were made, the results of the simulation appear promising.

Yeh, T.C.J.; Greenholtz, D.E. (Arizona Univ., Tucson, AZ (United States). Dept. of Hydrology and Water Resources); Nash, M.S. (New Mexico State Univ., Las Cruces, NM (United States). Dept. of Crop and Soil Sciences); Wierenga, P.J. (Arizona Univ., Tucson, AZ (United States). Dept. of Soil and Water Science)

1991-01-01

99

Characterization and prediction of spatial variability of unsaturated hydraulic properties in a field soil: Las Cruces, New Mexico  

SciTech Connect

A 91-m transect was set up in an irrigated field near Las Cruces, New Mexico to investigate the spatial variability of unsaturated soil properties. A total of 455 sampling points were monitored along a grid consisting of 91 stations placed 1 m apart by 5 depths per station. Post-irrigation soil water tension and water content measurements were recorded over 45 days at 11 time periods. The instantaneous profile was used to estimate the unsaturated hydraulic conductivity at the 455 sampling points. Fifty soil samples were also taken for analyzing sand, silt, and clay content distributions. The spatial and temporal variability of soil water tension and water content were investigated along with the spatial variability of parameters of an unsaturated hydraulic conductivity model. Results of the analysis show that spatial variation in soil water tension and water content is consistent with the soil texture spatial variability. In addition, the spatial distribution of the estimated parameter value of unsaturated hydraulic conductivity reflects the soil texture distribution. Using the statistics of the estimated hydraulic parameter values, a stochastic soil water tension model was employed to reproduce the variability of observed soil water tension. Although many assumptions were made, the results of the simulation appear promising.

Yeh, T.C.J.; Greenholtz, D.E. [Arizona Univ., Tucson, AZ (United States). Dept. of Hydrology and Water Resources; Nash, M.S. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Crop and Soil Sciences; Wierenga, P.J. [Arizona Univ., Tucson, AZ (United States). Dept. of Soil and Water Science

1991-12-31

100

Development and Evaluation of Closed-Form Expressions for Hysteretic Soil Hydraulic Properties  

NASA Astrophysics Data System (ADS)

A concise representation of hysteretic soil hydraulic properties is given based on a combination of M. T. van Genuchten's (1980) parametric K-?-h model and P. S. Scott et al.'s (1983) empirical hysteresis model modified to account for air entrapment. The resulting model yields compact closed-form expressions for the hysteretic water retention curve ?(h) and soil water capacity C(h), as well as for the hydraulic conductivity function K(h). Depending on the degree of simplification involved, the model entails a total of 6-9 parameters which can be calibrated from direct measurements of ?(h) and saturated conductivity or by an inverse solution approach from transient flow experiments. Comparison of model-predicted and measured K-?-h relations for eight soils revealed one case in which model predictions were very poor. Model accuracy was judged to be acceptably good in the other cases. Mualern's modified (Y. Mualem, 1984) dependent domain model was found to be more accurate for soils with very narrow pore size distributions. Use of a simplified version of the proposed model with two parameters eliminated provided overall accuracy very similar to that of the more complex model. Numerical simulations of flow during transient infiltration and drainage using the proposed model and a variant of Y. Mualem's (1984) modified dependent domain model did not differ greatly and agreed reasonably well with experimental water content distributions, even when scanning curves were not described very accurately. By contrast, simulations without consideration of hysteresis produced highly unacceptable results. It is concluded that the proposed model provides a convenient and simple means of incorporating hysteretic effects into numerical flow models to provide significant improvement in prediction accuracy with little additional effort and with minimal data requirements.

Kool, J. B.; Parker, J. C.

1987-01-01

101

Cautionary notes on the use of pedotransfer functions for estimating soil hydraulic properties  

Microsoft Academic Search

The performance of published pedotransfer functions was evaluated in terms of predicted soil water content, pressure heads, and drainage fluxes for a layered profile. The pedotransfer functions developed by Vereecken et al. (1989), Vereecken et al. (1990) were used to determine parameters of the soil hydraulic functions ?(h) and K(h) which were then used as input to SWATRER, a transient

A. Espino; D. Mallants; M. Vanclooster; J. Feyen

1996-01-01

102

PHYSICAL AND HYDRAULIC PROPERTIES OF ENGINEERED SOIL MEDIA FOR BIORETENTION BASINS  

Microsoft Academic Search

The composition of engineered soil media largely determines the stormwater treatment efficiency of urban bioretention basins. Laboratory flow-through experiments were conducted to quantify infiltration, bulk density, and moisture holding capacity as a function of different composite mixtures of sand, soil, and compost, and to assess the effect of compaction on bulk density, moisture holding capacity, and saturated hydraulic conductivity. Eleven

A. M. Thompson; A. C. Paul; N. J. Balster

103

Comparative analysis of three methods to generate soil hydraulic functions  

Microsoft Academic Search

An accurate determination of the soil hydraulic functions is crucial for using soil water simulation models. The purpose of this study is to compare different methods to estimate hydraulic properties and their effects on the simulation of soil water movement. Soil water retention and hydraulic conductivity functions were either measured in the laboratory (core method) and in the field (instantaneous

A. Mermoud; D. Xu

2006-01-01

104

A scaling based estimation of soil unsaturated hydraulic properties at a field scale  

Microsoft Academic Search

This paper deals with the prediction of the soil water retention h(S) and the soil unsaturated hydraulic conductivity K(S) functions of a clay-loam soil at a field scale (1 ha) where the variable S represents water saturation. The Van Genuchten model and the corresponding Mualem-Van Genuchten model were used to predict\\u000a h(S) and K(S) functions respectively. The field data (tensiometric

P. Bertuzzi; L. Bruckler

1996-01-01

105

An Analysis of the Impacts of Sodic Soil Amelioration on Soil Hydraulic Properties, Deep Drainage and Groundwater Using the HYDRUS Model  

NASA Astrophysics Data System (ADS)

Groundwater tables are rising beneath irrigated fields in some areas of the lower Burdekin in North Queensland, Australia. The soils where this occurs are predominantly sodic clay soils with low hydraulic conductivities. Many of these soils have been treated by applying gypsum or by increasing the salinity of irrigation water by mixing saline groundwater with fresh river water. While the purpose of these treatments is to increase infiltration into the surface soils and improve productivity of the root zone, the treatments appear to have altered the soil hydraulic properties well below the root zone leading to increased groundwater recharge and rising water tables. In this paper we discuss application of the HYDRUS model with major ion reaction and transport and soil water chemistry-dependent hydraulic conductivity to assess the likely depth, magnitude and timing of the impacts of surface soil amelioration on soil hydraulic properties below the root zone and hence groundwater recharge. We highlight in particular the role of those factors which might influence the impacts of the soil treatment, particularly at depth, including the large amounts of rain during the relatively short wet season and the presence of thick low permeability clay layers.

Reading, L.; Lockington, D. A.; Bristow, K. L.; Baumgartl, T.

2009-12-01

106

Laboratory analysis of soil hydraulic properties of CDBM 2 and CDBM 3 samples  

SciTech Connect

Daniel B. Stephens & Associates, Inc. (DBS&A) was requested by Dr. Alan Stoker of Los Alamos National Laboratory to perform laboratory analysis for properties of CDBM 2 and CDBM 3 samples, as outlined in Subcontract No. 9-XTI-027EE-1. The scope of work included conducting tests for the following properties: Initial moisture content, dry bulk density, and calculated porosity; Saturated hydraulic conductivity; Moisture characteristics; Unsaturated hydraulic properties (calculated); and Transient outflow.

NONE

1992-12-01

107

Near-surface soil moisture assimilation for quantifying effective soil hydraulic properties using genetic algorithm: 1. Conceptual modeling  

Microsoft Academic Search

We used a genetic algorithm (GA) to identify soil water retention $\\\\theta$(h) and hydraulic conductivity K(h) functions by inverting a soil-water-atmosphere-plant (SWAP) model using observed near-surface soil moisture (0-5 cm) as search criterion. Uncertainties of parameter estimates were estimated using multipopulations in GA and considering data and modeling errors. Three hydrologic cases were considered: (1) homogenous free-draining soil column, (2)

Amor V. M. Ines; Binayak P. Mohanty

2008-01-01

108

Laboratory analysis of soil hydraulic properties of TA-49 soil samples. Volume I: Report summary  

SciTech Connect

The Hydrologic Testing Laboratory at Daniel B. Stephens & Associates, Inc. (DBS&A) has completed laboratory tests on TA-49 soil samples as specified by Mr. Daniel A. James and summarized in Table 1. Tables 2 through 12 give the results of the specified analyses. Raw laboratory data and graphical plots of data (where appropriate) are contained in Appendices A through K. Appendix L lists the methods used in these analyses. A detailed description of each method is available upon request. Thermal properties were calculated using methods reviewed by Campbell and covered in more detail in Appendix K. Typically, soil thermal conductivities are determined using empirical fitting parameters (five in this case), Some assumptions are also made in the equations used to reduce the raw data. In addition to the requested thermal property measurements, calculated values are also presented as the best available internal check on data quality. For both thermal conductivities and specific heats, calculated and measured values are consistent and the functions often cross. Interestingly, measured thermal conductivities tend to be higher than calculated thermal conductivities around typically encountered in situ moisture contents ({plus_minus}5 percent). While we do not venture an explanation of the difference, sensitivity testing of any problem requiring nonisothermal modeling across this range is in order.

NONE

1995-04-01

109

Applicability of site-specific pedotransfer functions and rosetta model for the estimation of dynamic soil hydraulic properties under different vegetation covers  

Microsoft Academic Search

Background, Aims, and Scope  During the last decades, different methods have been developed to determine soil hydraulic properties in the field and laboratory.\\u000a These methodologies are frequently time-consuming and\\/or expensive. An indirect method, named Pedotransfer Functions (PTFs),\\u000a was developed to predict soil hydraulic properties using other easily measurable soil (physical and chemical) parameters.\\u000a This work evaluates the use of the PTFs

Carles M. Rubio; Ferran El Catolic

2008-01-01

110

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...

111

Consistent parameter constraints for soil hydraulic functions  

Microsoft Academic Search

Parameters of functions to describe soil hydraulic properties are derived from measurements by means of parameter estimation. Of crucial importance here is the choice of correct constraints in the parameter space. Often, the parameters are mere shape parameters without physical meaning, giving flexibility to the model. A fundamental requirement is that the hydraulic functions are monotonic: the retention function and

Andre Peters; Wolfgang Durner; Gerd Wessolek

2011-01-01

112

Near-surface soil moisture assimilation for quantifying effective soil hydraulic properties using genetic algorithms: 2. Using airborne remote sensing during SGP97 and SMEX02  

NASA Astrophysics Data System (ADS)

Pixel-based effective soil hydraulic parameters are crucial inputs for large-scale hydroclimatic modeling. In this paper, we extend/apply a genetic algorithm (GA) approach for estimating these parameters at the scale of an airborne remote sensing (RS) footprint. To estimate these parameters, we used a time series of near-surface RS soil moisture data to invert a physically based soil-water-atmosphere-plant (SWAP) model with a (multipopulated) modified-microGA. Uncertainties in the solutions were examined in two ways: (1) by solving the inverse problem under various combinations of modeling conditions in a respective way; and (2) the same as the first method but the inverse solutions were determined in a collective way aimed at finding the robust solutions for all the modeling conditions (ensembles). A cross validation of the derived soil hydraulic parameters was done to check their effectiveness for all the modeling conditions used. For our case studies, we considered three electronically scanned thinned array radiometer (ESTAR) footprints in Oklahoma and four polarimetric scanning radiometer (PSR) footprints in Iowa during the Southern Great Plains 1997 (SGP97) Hydrology Experiment and Soil Moisture Experiment 2002 (SMEX02) campaigns, respectively. The results clearly showed the promising potentials of near-surface RS soil moisture data combined with inverse modeling for determining average soil hydrologic properties at the footprint scale. Our cross validation showed that parameters derived by method 1 under water table (bottom boundary) conditions are applicable also for free-draining conditions. However, parameters derived under free-draining conditions generally produced too wet near-surface soil moisture when applied under water table conditions. Method 2, on the other hand, produced robust parameter sets applicable for all modeling conditions used. These results were validated using distributed in situ soil moisture and soil hydraulic properties measurements, and texture-based data from the UNSODA database. In this study, we conclude that inverse modeling of RS soil moisture data is a promising approach for parameter estimation at large measurement support scale. Nevertheless, the derived effective soil hydraulic parameters are subject to the uncertainties of remotely sensed soil moisture data and from the assumptions used in the soil-water-atmosphere-plant modeling. Method 2 provides a flexible framework for accounting these sources of uncertainties in the inverse estimation of large-scale soil hydraulic properties. We have illustrated this flexibility by combining multiple data sources and various modeling conditions in our large-scale inverse modeling.

Ines, Amor V. M.; Mohanty, Binayak P.

2009-01-01

113

Inverse Estimation of the Unsaturated Soil Hydraulic Properties from Column Outflow Experiments Using Free-Form Parameterizations  

Microsoft Academic Search

is often still limited by the ill-posedness of the problem being considered. Ill-posedness in general is affected Inverse methods are increasingly used to estimate the hydraulic by nonoptimal experimental design, poor measurement properties of unsaturated soils. The method generally uses a weighted least-squares approach in which numerically simulated data are fitted quality, errors in the assumed process model, or unsuit-

S. Bitterlich; W. Durner; S. C. Iden; P. Knabner

2004-01-01

114

Impact of spruce forest and grass vegetation cover on soil micromorphology and hydraulic properties of organic matter horizon  

Microsoft Academic Search

Two organic matter horizons developed under a spruce forest and grass vegetation were chosen to demonstrate the impact of\\u000a a different vegetation cover on the micromorphology, porous system and hydraulic properties of surface soils. Micromorphological\\u000a studies showed that the decomposed organic material in the organic matter horizon under the grass vegetation was more compact\\u000a compared to the decomposed organic material

Radka Kodešová; Lenka Pavl?; Vít Kodeš; Anna Žigová; Antonín Nikodem

2007-01-01

115

Effective Hydraulic Properties Determined from Transient Unsaturated Flow in Anisotropic Soils  

Microsoft Academic Search

Hydraulic parameters including the pore connectivity\\/tortuosity tensor (L_i) were inversely estimated using the STOMP numerical simulator coupled with the parameter estimation code, UCODE. Results show that six of eight parameters required for a modified van Genuchten-Mualem model could be inversely estimated using water content measured during transient infiltration from a surface line source and approximated prior information. Soils showed evidence

Andy L. Ward; Z. Fred Zhang

2007-01-01

116

Physical and hydraulic properties of soils of the Sudano-Sahelian regions of Nigeria  

Microsoft Academic Search

The inadequacy of rainfall and poor soil fertility in the Sudano-Sahelian zone of West Africa are responsible for the hunger, misery and desertification in the area. It is therefore important to understand the soils and their properties for effective management strategies. In Nigeria, the soils are formed from aeolian, lacustrine and basement complex parent materials and are classified mostly as

H. O. MADUAKOR

117

Uniqueness and stability analysis of hydrogeophysical inversion for time-lapse ground-penetrating radar estimates of shallow soil hydraulic properties  

Microsoft Academic Search

Precise measurement of soil hydraulic properties at field scales is one of the prerequisites to simulate subsurface flow and transport processes, which is crucial in many research and engineering areas. In our study, we numerically analyze uniqueness and stability for integrated hydrogeophysical inversion of time-lapse, off-ground ground-penetrating radar (GPR) data in estimating the unsaturated soil hydraulic properties. In the inversion,

Khan Zaib Jadoon; Evert Slob; Marnik Vanclooster; Harry Vereecken; Sébastien Lambot

2008-01-01

118

Using geostatistical, artificial neural network and inverse models to estimate 3D soil type and hydraulic property distributions in a deep volume of unsaturated soil  

NASA Astrophysics Data System (ADS)

We use geostatistical and neural network analyses to estimate the three-dimensional distributions of soil types and hydraulic properties in a relatively large volume of vadose zone underlying the Maricopa Agriculture Center near Phoenix, Arizona. Geostatistical analysis of soil texture and bulk density data from the site are analyzed geostatistically to reveal the underlying stratigraphy as well as finer features of their three-dimensional variability in space. Such fine features are revealed by cokriging soil texture (as primary variable) and water content measured prior to large-scale long-term infiltration experiments (as secondary variable). Resultant estimates of soil texture and bulk density data across the site are then used as input into a neural network model to produce estimates of soil hydraulic parameter (saturated and residual water content, saturated hydraulic conductivity, van Genuchten parameters alpha and n) distributions across the site in three dimensions. We compare these estimates with laboratory-measured values of these same hydraulic parameters and with estimates obtained by inversion using a three-dimensional flow simulator.

Fang, Z.; Neuman, S. P.; Schaap, M.; Yao, T.

2008-12-01

119

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

120

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

121

Estimation of ``effective'' soil hydraulic properties by topsoil moisture and evaporation modeling applied to an arable site in central Spain  

NASA Astrophysics Data System (ADS)

A surface moisture model for large-scale semiarid land application has been extended with a moisture flow routine for capillary flow. The model has been applied to a field-scale data set of topsoil moisture and latent heat flux of an arable site in central Spain. A comparison of the soil hydraulic properties, determined by model simulations and measurements in the field, demonstrates the capability of the model to determine these properties out of a range of soil classes as defined according to the parameterization by Clapp and Hornberger [1978]. Estimation of area average or "effective" soil physical parameters according to this approach requires time series of topsoil moisture and actual evapotranspiration on a patch or regional scale. Therefore this approach has potential for use with remotely sensed data.

Gouweleeuw, Ben T.; van de Griend, Adriaan A.; Owe, Manfred

1996-05-01

122

Effect of Compaction and Deep Tillage on Soil Hydraulic and Aeration Properties and Wheat Yield  

Microsoft Academic Search

The effects of deep tillage and annual compaction (1996–1997) of two axle loads resulting from wheeled traffic on soil were evaluated by measuring the changes in soil physical properties (cone index, air porosity, and infiltration rate) and by measuring changes in crop yield in comparison with control plots. Results included the effects of these parameters at four depths (10 to

Nidal H. Abu-Hamdeh

2003-01-01

123

Constraining GPR data inversion using hydrodynamic laws for noninvasive soil hydraulic and electric property determination  

Microsoft Academic Search

We constrain full-wave inversion of time-lapse radar data using hydrodynamic modeling to simultaneously identify the shallow subsurface hydraulic properties and continuous vertical electric profiles. Radar data are acquired in the frequency domain using a vector network analyzer combined with an off-ground monostatic antenna. This permits to accurately filter antenna effects and to derive Green functions from which the inversion is

S. Lambot; S. Guillasot; H. Vereeckent; E. Slob

2007-01-01

124

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application  

Microsoft Academic Search

The selective radius shift model was used to relate changes in mineral volume due to precipitation\\/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation\\/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation\\/dissolution within a pore depends on the local

L. Wissmeier; D. A. Barry

2009-01-01

125

Impact of rooting depth and soil hydraulic properties on the transpiration peak of an evergreen forest in northern Thailand in the late dry season  

Microsoft Academic Search

Previous research showed that transpiration in an evergreen broad-leaved forest in northern Thailand (18°48?N, 98°54?E) peaked at the end of the dry season. However, rooting depth limitations on soil water use were not investigated. This study examined the impact of rooting depth and soil hydraulic properties on transpiration using a newly developed soil plant air continuum model. The soil texture

Katsunori Tanaka; Hideki Takizawa; Tomonori Kume; Jianqing Xu; Chatchai Tantasirin; Masakazu Suzuki

2004-01-01

126

Impact of rooting depth and soil hydraulic properties on the transpiration peak of an evergreen forest in northern Thailand in the late dry season  

Microsoft Academic Search

Previous research showed that transpiration in an evergreen broad-leaved forest in northern Thailand (18°48'N, 98°54'E) peaked at the end of the dry season. However, rooting depth limitations on soil water use were not investigated. This study examined the impact of rooting depth and soil hydraulic properties on transpiration using a newly developed soil plant air continuum model. The soil texture

Katsunori Tanaka; Hideki Takizawa; Tomonori Kume; Jianqing Xu; Chatchai Tantasirin; Masakazu Suzuki

2004-01-01

127

Strength, Durability And Hydraulic Properties Of Clayey Soil Stabilized With Lime And Industrial Waste Lime  

Microsoft Academic Search

This research aims to study the effect of utilization of industrial waste\\/lime (by-product of sugar factory) on some engineering properties of clayey soil selected from Mosul city. These characteristics are unconfined compressive strength, permeability, soil-water characteristic curve and Durability. The tests were performed at different percentages of lime (2, 4 and 6) % and industrial waste\\/lime (2, 4, 6 and

Suhail A. A. Khattab; Khawla A. K. Al-Juari; Ibrahaim M. A. Al-Kiki

2007-01-01

128

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

Microsoft Academic Search

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

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

2005-01-01

129

Parameter conditioning with a noisy Monte Carlo genetic algorithm for estimating effective soil hydraulic properties from space  

Microsoft Academic Search

The estimation of effective soil hydraulic parameters and their uncertainties is a critical step in all large-scale hydrologic and climatic model applications. Here a scale-dependent (top-down) parameter estimation (inverse modeling) scheme called the noisy Monte Carlo genetic algorithm (NMCGA) was developed and tested for estimating these effective soil hydraulic parameters and their uncertainties. We tested our method using three case

Amor V. M. Ines; Binayak P. Mohanty

2008-01-01

130

Estimating Saturated Hydraulic Conductivity from Soil Water Retention Curve using Neural Networks  

Microsoft Academic Search

Study of soil hydraulic properties like saturated and unsaturated hydraulic conductivity is required in the environmental investigations. Since, direct measurement of soil hydraulic properties is time consuming and expensive, indirect methods such as pedotransfer function and artificial neural networks (ANN) have been developed based on the readily available soil characteristics. In this study, we used soil water retention data i.e.

B. Ghanbarian-Alavijeh; A. M. Liaghat; S. Sohrabi

2009-01-01

131

Gaining insight into the spatial distribution of soil hydraulic properties on the soil profile scale by high resolution TDR and tensiometer measurements  

NASA Astrophysics Data System (ADS)

Measurement of the spatial distribution of hydraulic properties in a field with high resolution and good precision is still depending on the laborious and time consuming measurement with invasive equipment, such as TDR probes and tensiometers. If measurements are available, their spatial resolution is often rather coarse. When sensors are applied to monitor soil water dynamics under natural or artificial boundary conditions, the typical distance between probes is in the range of several decimetres. Finer resolutions are usually not realized because they are likely to influence the flow field in an unwanted manner. On the other hand, spatial correlation length especially of the water content in soils is often smaller leaving a question mark on how to interpolate gaps and get the hydraulic structure right. An alternative approach is the destructive measurement of these properties once an experiment has ended. The measurement of soil hydraulic functions on soil cores is very time consuming and if taken on a grid, a spacing of about 15 cm between individual cores is the resolution limit. In this study, we approach the problem by cutting several soil profiles through the experimental plot at the end of an infiltration experiment from a site north of Hannover, Germany. Using TDR and microtensiometer, data pairs of water content and tension are measured on a grid with a resolution of 5 x 5 cm. The measurement is relatively quick once a soil profile is prepared. However, only a single pair of water content and water tension is acquired per measuring location. For a soil profile of approx. 1 by 2 m this adds up to about 700 data pairs. By a visual inspection of the data measured on the profile, bordering structures having similar tensions but different water contents are identified. Some of these structures are much smaller than the usually encountered measuring resolution of several decimetres. In a second step, data pairs are grouped according to their location within the different structures visible in the soil profile. For these groups, water characteristic reference functions are calculated and heterogeneity is formulated using different scaling approaches. The resulting heterogeneous distributions are compared and evaluated with regard to their ability to capture the characteristics of the true heterogeneity in the profile. Results of this investigation will eventually be fed into a soil water transport model that will be used for a hindcast model exercise aiming at remodelling the infiltration experiment. Model results will be compared to electrical resistivity tomography measurements carried out parallel to the infiltration experiment.

Altfelder, S.; Ganz, C.; Noell, U.; Duijnisveld, W. H. M.; Bachmann, J.

2010-05-01

132

A method for the determination of the hydraulic properties of soil from MODIS surface temperature for use in land-surface models  

Microsoft Academic Search

Soil hydraulic properties (SHPs) play an important role in land-surface models, but their spatial distribution is poorly known, and it is not feasible to make field measurements of SHPs everywhere they are needed. In addition, the scale SHPs are measured on (10 cm) is substantially smaller than the scale at which land-surface models are run (>1 km). As a result,

Ethan D. Gutmann; Eric E. Small

2010-01-01

133

Using an inverse method to estimate the hydraulic properties of crusted soils from tension-disc infiltrometer data  

Microsoft Academic Search

An inverse procedure was used to estimate the soil hydraulic characteristics of a two-layered soil system—soil surface crust and subsoil—from data obtained during a tension-disc infiltration experiment. The inverse procedure combined the Levenberg–Marquardt nonlinear parameter optimization method with a numerical solution of the axisymmetric variably-saturated flow equation. The objective function was defined in terms of the cumulative infiltration curve and

Ji??? Šim?nek; Rafael Angulo-Jaramillo; Marcel G. Schaap; Jean-Pierre Vandervaere; Martinus Th. van Genuchten

1998-01-01

134

Anisotropy of Soil Hydraulic Properties Along Arable Slopes 1 1 Project supported by the National Natural Science Foundation of China (NSFC) (No. 40071044) and the Deutsche Forschungsgemeinschaft (DFG) (No. ZE 254\\/4)  

Microsoft Academic Search

The spatial variations of the soil hydraulic properties were mainly considered in vertical direction. The objectives of this study were to measure water-retention curves, ?(?), and unsaturated hydraulic conductivity functions, K(?), of the soils sampled at difierent slope positions in three directions, namely, in vertical direction, along the slope and along the contour, and to determine the efiects of sampling

Yuan-Shu JING; Bin ZHANG; A. THIMM; H. ZEPP

2008-01-01

135

USING FRACTAL MODELS IN SCALING AND PEDOTRANSFER FUNCTIONS OF SOIL HYDRAULIC PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Geometric irregularity and heterogeneity are inherent features of soils. Fractal geometry provides explicit parameterization of the irregularity in surfaces and outlines, and fractal models can be fitted to many types of soil data. Using fractal geometry in soil studies strives for (a) quantifying c...

136

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

137

The efficiency of various approaches to obtaining estimates of soil hydraulic properties  

Microsoft Academic Search

A formal analysis was carried out to evaluate the efficiency of the different methods in predicting water retention and hydraulic conductivity. Efficiency can be defined in terms of effort, cost or value of information. The analysis identified the contribution of individual sources of measurement errors to the overall uncertainty. The value of information summarises the quality of the prediction, the

Budiman Minasny; Alex B McBratney

2002-01-01

138

Laboratory Hydraulic Testing in Unsaturated Soils  

Microsoft Academic Search

This paper synthesizes the state-of-the art of the various laboratory testing techniques presently available for measuring\\u000a the water hydraulic constitutive functions of unsaturated soils. Emphasis is on the laboratory testing techniques for measuring\\u000a the soil–water retention curves and the water hydraulic conductivity functions of unsaturated soils. The significant recent\\u000a advances in the investigation of the hydraulic behaviour of unsaturated swelling

Farimah Masrouri; Kátia V. Bicalho; Katsuyuki Kawai

2008-01-01

139

Prediction of unsaturated soil hydraulic conductivity with electrical conductivity  

Microsoft Academic Search

Soil hydraulic conductivity (K) varies greatly with matric potential (h) and exhibits a high variability at the field scale. However, this key property for estimating water flux in soils is difficult to measure. In contrast, soil electrical conductivity (?) is easier to measure and is influenced by the same parameters affecting K. We derive a simple relationship between ? and

Claude Doussan; Stéphane Ruy

2009-01-01

140

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

141

Discrimination of Soil Hydraulic Properties by Combined Thermal Infrared and Microwave Remote Sensing.  

National Technical Information Service (NTIS)

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 ...

A. A. Vandegriend P. E. Oneill

1986-01-01

142

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

143

Extended multistep outflow method for the accurate determination of soil hydraulic properties near water saturation  

Microsoft Academic Search

Combining percolation and multistep outflow experiments leads to improved estimatesMore accurate estimation of near-saturated conductivitySimultaneous and accurate estimation of plate conductance and the soil conductive

W. Durner; S. C. Iden

2011-01-01

144

Influence of soil texture on hydraulic properties and water relations of a dominant warm-desert phreatophyte.  

PubMed

We investigated hydraulic constraints on water uptake by velvet mesquite (Prosopis velutina Woot.) at a site with sandy-loam soil and at a site with loamy-clay soil in southeastern Arizona, USA. We predicted that trees on sandy-loam soil have less negative xylem and soil water potentials during drought and a lower resistance to xylem cavitation, and reach E(crit) (the maximum steady-state transpiration rate without hydraulic failure) at higher soil water potentials than trees on loamy-clay soil. However, minimum predawn leaf xylem water potentials measured during the height of summer drought were significantly lower at the sandy-loam site (-3.5 +/- 0.1 MPa; all errors are 95% confidence limits) than at the loamy-clay site (-2.9 +/- 0.1 MPa). Minimum midday xylem water potentials also were lower at the sandy-loam site (-4.5 +/- 0.1 MPa) than at the loamy-clay site (-4.0 +/- 0.1 MPa). Despite the differences in leaf water potentials, there were no significant differences in either root or stem xylem embolism, mean cavitation pressure or Psi(95) (xylem water potential causing 95% cavitation) between trees at the two sites. A soil-plant hydraulic model parameterized with the field data predicted that E(crit) approaches zero at a substantially higher bulk soil water potential (Psi(s)) on sandy-loam soil than on loamy-clay soil, because of limiting rhizosphere conductance. The model predicted that transpiration at the sandy-loam site is limited by E(crit) and is tightly coupled to Psi(s) over much of the growing season, suggesting that seasonal transpiration fluxes at the sandy-loam site are strongly linked to intra-annual precipitation pulses. Conversely, the model predicted that trees on loamy-clay soil operate below E(crit) throughout the growing season, suggesting that fluxes on fine-textured soils are closely coupled to inter-annual changes in precipitation. Information on the combined importance of xylem and rhizosphere constraints to leaf water supply across soil texture gradients provides insight into processes controlling plant water balance and larger scale hydrologic processes. PMID:16356903

Hultine, K R; Koepke, D F; Pockman, W T; Fravolini, A; Sperry, J S; Williams, D G

2006-03-01

145

Spatial Variability of Physical Properties of a Tropical Soil. II. Soil Water Retention Curves and Hydraulic Conductivity.  

National Technical Information Service (NTIS)

The characterization of a field site from the soil physics point of view, the improvement of the use of soil and water resources under a particular condition and the development of means for controlling the dynamics of soil-water movement are presented. S...

K. Reichardt P. L. Libardi S. V. Queiroz F. Grohmann

1976-01-01

146

Hydraulic and thermal properties of soil samples from the buried waste test facility  

SciTech Connect

In shallow land burial, the most common disposal method for low-level waste, waste containers are placed in shallow trenches and covered with natural sediment material. To design such a facility requires an in-depth understanding of the infiltration and evaporation processes taking place at the soil surface and the effect these processes have on the amount of water cycling through a burial zone. At the DOE Hanford Site in Richland, Washington, a field installation called the Buried Waste Test Facility (BWTF) has been constructed to study unsaturated soil water and contaminant transport. PNL is collecting data at the BWTF to help explain soil water movement at shallow depths, and specifically evaporation from bare sols. The data presented here represent the initial phase of a cooperative effort between PNL and Washington State University to use data collected at the BWFT.

Cass, A.; Campbell, G.S.; Jones, T.L.

1981-10-01

147

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

148

Hydraulic Property Determination of Vesiculated Soil Peds in Desert Pavement Environments  

Microsoft Academic Search

Desert pavements are prominent features in arid and semi-arid environments, and can be found on a variety of landforms of significantly diverse ages ranging from Holocene to Tertiary. Desert pavements consist of a surface layer of closely packed gravel, typically one stone thick, that overlies a silt-rich vesicular A (Av) soil horizon. The vesicular horizon is composed of highly structured,

D. G. Meadows; M. H. Young; T. G. Caldwell; E. V. McDonald

2003-01-01

149

Quantifying Saturation-Dependent Anisotropy in Soil Hydraulic Conductivity  

NASA Astrophysics Data System (ADS)

The anisotropy in unsaturated hydraulic conductivity is saturation-dependent. Accurate characterization of soil anisotropy is very important in simulating flow and contaminants (e.g., radioactive nuclides in Hanford) transport. A recently proposed tensorial connectivity-tortuosity (TCT) concept describes the hydraulic conductivity tensor of the unsaturated anisotropic soils as the product of a scalar variable, the symmetric connectivity tortuosity tensor, and the hydraulic conductivity tensor at saturation. In this study, the TCT model is used to quantify soil anisotropy in unsaturated hydraulic conductivity. The results show that the anisotropy coefficient, A, is independent of soil water retention properties. At a certain saturation, A can be characterized by the ratio of the saturated hydraulic conductivities and the difference in the tortuosity-connectivity coefficients in orthogonal directions. The model was tested using directional measurements of unsaturated hydraulic conductivity of undisturbed soil cores. Results show that the TCT model can describe different types of soil anisotropy, previously ignored in other models. The TCT model can be used to describe either monotonic increases or decreases in A with saturation and allows the principal direction of hydraulic conductivity to rotate when saturation varies. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract DE-AC06-76RL01830.

Zhang, Z. F.; Ward, A. L.; Gee, G. W.; White, M. D.; Keller, J. M.

2004-12-01

150

A DRIPPER-TDR METHOD FOR INSITU DETERMINATION OF HYDRAULIC CONDUCTIVITY AND CHEMICAL TRANSPORT PROPERTIES OF SURFACE SOILS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Field determined hydraulic and chemical transport properties can be useful for the protection of groundwater resources from land-applied chemicals. Most field methods to determine flow and transport parameters are either time or energy consuming and/or they provide a single measurement for a given t...

151

Evaluation of pedotransfer functions for estimating soil hydraulic properties of prevalent soils in a catchment of the Bavarian Alps  

Microsoft Academic Search

In this study, two types of pedotransfer functions (PTFs) were evaluated for their accuracy and applicability to a broad range\\u000a of Alpine soils in the Halbammer area in southern Bavaria (Germany). The first model is ROSETTA, which is based on neural\\u000a network analyses. It implements five hierarchical PTFs using limited to more extend input data. The second model is SOILPROP

Christine Stumpp; S. Engelhardt; M. Hofmann; B. Huwe

2009-01-01

152

Unsaturated Hydraulic Conductivity for Layered Heterogeneous Soils  

Microsoft Academic Search

This study investigates the effective hydraulic conductivities of unsaturated soils for one-dimensional structured heterogeneity. The heterogeneity is defined using homogeneous sublayers forming repeated unit cells. Results from previous studies indicated that for a large cell length, the effective hydraulic conductivity approaches an arithmetic average of the pressure heads which develop in each sublayer. For a cell of length approaching zero,

J. Zhu

2008-01-01

153

Soil Properties  

NSDL National Science Digital Library

In order to introduce soil properties, students will determine the texture and color of a variety of local soils brought in by their classmates. Each student will describe their soil to the class, indicating where the soil came from and any interesting features regarding the site. Students will group the soils based on this little bit of knowledge and then re-evaluate their groupings after texture and color have been determined. This activity concludes with a discussion of regional soils and variations in soils.

Todd, Carrie D.

154

Impact of polypropylene fibers on desiccation cracking and hydraulic conductivity of compacted clay soils  

Microsoft Academic Search

Compacted clay soils are commonly used as hydraulic barriers in waste containment systems such as in liners and covers for landfills, impoundments, reservoirs, and ponds. Compacted clays can minimize infiltration of fluid into waste or control the release of contaminated fluids to the surrounding soils and groundwater. The hydraulic properties of these soil-based structures can be adversely affected by desiccation

Sami Mansour Rifai

2000-01-01

155

ESTIMATION OF THE UNSATURATED HYDRAULIC CONDUCTIVITY OF PEAT SOILS: LABORATORY VERSUS FIELD DATA  

Technology Transfer Automated Retrieval System (TEKTRAN)

As compared to mineral soils, few in-situ measurements are currently available of the unsaturated hydraulic properties of peat soils. We used parameter estimation (inverse) methods to estimate the water retention and hydraulic conductivity functions of drained peat soils from both laboratory and fi...

156

Impact of soil hydraulic parameter uncertainty on soil moisture modeling  

NASA Astrophysics Data System (ADS)

For simulations in basins where soil information is limited to soil type maps, a methodology is presented to quantify the uncertainty of soil hydraulic parameters arising from within-soil-class variability and to assess the impact of this uncertainty on soil moisture modeling. Continuous pedotransfer functions were applied to samples with different texture within each soil class to construct discrete probability distributions of the soil hydraulic parameters. When propagating the parameter distributions through a hydrologic model, a wide range of simulated soil moisture was generated within a single soil class. The pedotransfer function was found to play a crucial role in assessing the uncertainty in the modeled soil moisture, and the geographic origin of the pedotransfer function (region specific versus nonregion specific) highly affected the range and shape of the probability distribution of the soil hydraulic parameters. Furthermore, the modeled soil moisture distribution was found to be non-Gaussian. An accurate uncertainty assessment therefore requires the characterization of its higher-order moments. As an extension of this research, we have shown that applying continuous region-specific pedotransfer functions to the central point of a soil class is a better alternative to standard (often nonregion-specific) class pedotransfer functions for determining an average set of soil hydraulic parameters.

Loosvelt, Lien; Pauwels, Valentijn R. N.; Cornelis, Wim M.; de Lannoy, GabriëLle J. M.; Verhoest, Niko E. C.

2011-03-01

157

Calculated Hydraulic Conductivity of Soil in Seoul, Korea  

NASA Astrophysics Data System (ADS)

Because of growing evidence and public concern that the quality of the subsurface environment is being adversely affected by industrial, municipal and agricultural activities, environmental issue relating the unsaturated zone has dramatically increased in recent years. Especially, advection and dispersion mechanism of contaminants should be studied first for accurate prediction and optimal conservation of environmental system in metropolitan area. In this study, physical properties and water retention characteristics of soil samples collected through Seoul area were obtained as primary input data for evaluating unsaturated hydraulic conductivities of the samples. Comparing results of grain size analyses of 11 soil samples with detailed soil map, loam may covers about 50.83% of Seoul area and sandy loam, silt loam, fine sandy loam and silt clay loam account for about 20.9%, 10.18%, 7.93% and 0.86%, respectively. As physical properties of the samples, porosity, wet, saturate and dry densities of 11 soil samples ranged 0.33-0.51, 1.68-2.01, 1.81-2.07, and 1.37-1.78, respectively. In addition, soil water characteristic function of 11 soil samples showing the relation between volumetric moisture content of soil and hydraulic head were obtained. Unsaturated hydraulic conductivities of the samples were also calculated on the basis of theoretical method which predict the conductivity more easily from measured soil water retention data. The calculated conductivities of the samples ranged 1.08-101.44 cm/sec.

Lee, D.

2001-12-01

158

Consistent parameter constraints for soil hydraulic functions  

NASA Astrophysics Data System (ADS)

Parameters of functions to describe soil hydraulic properties are derived from measurements by means of parameter estimation. Of crucial importance here is the choice of correct constraints in the parameter space. Often, the parameters are mere shape parameters without physical meaning, giving flexibility to the model. A fundamental requirement is that the hydraulic functions are monotonic: the retention function and the conductivity function can only decrease as the capillary suction increases. A stricter physical requirement for the conductivity function is that its decrease with respect to saturation is at least linear. This linear decrease would occur if all pores of a capillary bundle had an equal radius. In the first part of this contribution, we derive constraints for the so-called tortuosity parameter of the Mualem conductivity model, which allow highest possible flexibility on one hand and guarantee physical consistency on the other hand. In combination with the retention functions of Brooks and Corey, van Genuchten, or Durner, such a constraint can be expressed as a function of the pore-size distribution parameters. In the second part, we show that a common modification of retention models, which is applied to reach zero water content at finite suction, can lead to the physically unrealistic case of increasing water content with increasing suction. We propose a solution for this problem by slightly modifying these models and introducing a correct parameter constraint.

Peters, Andre; Durner, Wolfgang; Wessolek, Gerd

2011-10-01

159

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

160

Is the hydraulic behaviour of linearly similar soils different than non-similar soils?  

NASA Astrophysics Data System (ADS)

Construction of virtual soil domains for hydrological modeling often assumes that the hydraulic properties can be scaled according to linear scaling theory (e.g., Miller-Miller scaling or Warrick-Nielsen scaling). While linear similarity is an appropriate model of the hydraulic properties for some soils, it is likely not appropriate for all soils. The primary objectives of this work are: 1) to discuss the pore domain characteristics of linearly similar and nonlinearly similar soils; 2) explore the hydraulic behaviour (i.e., the spatial patter of soil water fluxes) of linearly similar and nonlinearly similar soils with the aid of a numerical simulation model (Hydrus 2D); and 3) discuss how the results and conclusions of the numerical simulations might be used to aid in the interpretation of data from field experiments and monitoring. It is also hoped that the results of this work will contribution to the understanding of how the spatial variability of hydraulic properties influence the spatial variability of soil hydraulic processes and the appropriateness of scaling the Richards equation.

Dyck, M. F.

2012-04-01

161

Hydraulic properties comparison in the calibration of CropSyst, SWAP and MACRO models in simulating soil water content for 3 years  

NASA Astrophysics Data System (ADS)

The quantification of the water balance components within soil-crop-climate system is strictly required to derive proper management conditions for plant growth and environmental protection. Numerical models are currently accepted as helpful tools to gain into the processes occurring in the soil-crop-climate system and to extrapolate data. A large number of available models solves, at field scale, the water balance components by the well known Richard's equation. Despite their common basis of the representation of water flow in the unsaturated zone, it is possible that with the same pedological, climatic and agronomic management conditions, apparently similar hydrological models give different answers. Therefore, to test the capability of a model to represent reality, model simulation must be compared with experimental data and with simulations by other models. The objective of the present study was to evaluate and compare the performances of three well known models (SWAP, MACRO and CropSyst based on the solution of the Richard's equation). Main attention was focussed on the effects of the calibration of the three models on the soil hydraulic properties parameterization. The performance of SWAP, MACRO and CropSyst is compared using field data collected from a structured fine soil (Vertic Calciustepts located in Cerese, Mantova, Italy) cropped to maize. The models are tested and compared on the basis of their ability to predict in situ the measured soil water content at different depths during the years 2002-2004. Water contents was measured with a TDR equipment at 5 depth, where possible with daily frequency. All three models produce acceptable predictions, as evidence by an average root mean square error (RMSE) within ± 0.031 and an average coefficient of residual mass (CRM) within ± 0.66. The SWAP and CropSyst models produces the better performance, but in absolute none of the models is consistently more accurate than the others. In any case the different behavior between the models can be attributed primarily to differences in how the models manage numerical solutions close to the bottom an upper boundaries and on the hydraulic properties parameterization. In particular, the CropSyst model has shown some limitations in following soil water dynamic for the numerical constraints in the parameterization of the Campbell's equation. Keywords: Models comparison, SWAP, MACRO, CropSyst

Bonfante, A.; Fragnito, F.; Manna, P.; Orefice, N.; Pastori, M.; Perego, A.

2009-04-01

162

On the Choice of Soil Hydraulic Models in Land-Surface Schemes  

NASA Astrophysics Data System (ADS)

The uncertainties in soil hydraulic functions and soil hydraulic parameters affect the performance of land-surface schemes used in climate and weather prediction models. The Clapp-Hornberger soil hydraulic model of is most widely used in land-surface modelling, while other models favoured by soil physicists are hardly used for the purpose. In this study, we give a summary of four soil hydraulic models and examine the impact of these models on the performance of a land-surface scheme. It is found that inconsistency in soil hydraulic functions and parameters leads to different outcomes in land-surface modelling. We introduce a technique to match the soil hydraulic parameters for different models, so that the disagreement in the description of soil hydraulic properties among different models is reduced, while intrinsic differences in the soil hydraulic functions remain. The numerical tests also show that the land-surface model has a degree of tolerance to the uncertainties in soil hydraulic models, at least in the case of off-line simulations. The van Genuchten model performs well, but is numerically expensive. The Brooks-Corey and Clapp-Hornberger models are sufficiently accurate with numerical efficiency, and are therefore more suitable for land-surface schemes used in atmospheric models.

Shao, Yaping; Irannejad, Parviz

163

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

164

Soil Hydraulic Parameter Estimation and Analysis of Flow Paths under Evaporation in undisturbed Soil Columns  

NASA Astrophysics Data System (ADS)

In general, spatial heterogeneity has an important impact on the local and effective soil hydraulic properties. Hence, one of the objectives of this study was to determine the effective soil hydraulic parameters of a highly heterogeneous, undisturbed soil sample using the evaporation method in combination with inverse modeling. Therefore, pressure heads, water contents, and the weight loss of an undisturbed soil column in course of an evaporation experiment were measured. The inverse estimation of the soil hydraulic parameters was performed using the HYDRUS-1D software package in combination with a global optimization algorithm SCE-UA. Most reported studies for soil hydraulic parameter estimation in soil column experiments used either pressure heads or water contents in the inverse routine. In this study, three scenarios were performed. Initially, only the pressure heads were used in the objective function, in the second scenario only the water content measurements were used to constrain the optimization, and in the third scenario both information from water content and pressure head readings were considered. As result three different soil hydraulic parameter sets were obtained which show strong differences. Including only pressure head or water content data would yield in serious misinterpretation of the effective soil hydraulic parameters of the soil monolith. The second objective of this study was to mark the flow paths of a Brilliant Blue solution in a heterogeneous soil monolith under evaporation conditions. As a result the Brilliant Blue solution preferentially flowed upwards close to the column wall. According to the fact that tracer experiments under evaporation conditions were rarely performed, this study shows that border effects have to be considered in further research.

Bartsch, S.; Bechtold, M.; Weihermüller, L.; Vereecken, H.

2009-04-01

165

Upscaling Schemes and Relationships for the Gardner and van Genuchten Hydraulic Functions for Heterogeneous Soils  

Microsoft Academic Search

Upscaled soil hydraulic properties are needed for many large-scale hydrologic applications such as regional and global climate studies and investigations of land-atmosphere interactions. Many larger scale sub- surface flow and contaminant transport studies also require upscaled hydraulic property estimates. The objectives of this study were to de- velop a methodology for upscaling hydraulic property functions using a p-norm approach, to

Jianting Zhu; Michael H. Young; Martinus Th. van Genuchten

2007-01-01

166

Comparison of artificial neural network and regression pedotransfer functions for prediction of soil water retention and saturated hydraulic conductivity  

Microsoft Academic Search

Modeling water flow and solute transport in vadose zone requires knowledge of soil hydraulic properties, which are water retention and hydraulic conductivity curves. As an alternative to direct measurement, indirect determination of these functions from basic soil properties using pedotransfer functions (PTFs) has attracted the attention of researchers in a variety of fields such as soil scientists, hydrologists, and agricultural

Hasan Merdun; Özer Ç?nar; Ramazan Meral; Mehmet Apan

2006-01-01

167

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

168

Incorporating Soil Hydraulic Parameter Statistics in Developing Pedo-transfer Functions  

NASA Astrophysics Data System (ADS)

In this study, we develop artificial neural network (ANN) based pedotransfer functions (PTFs) to predict soil hydraulic properties. The PTF approach is an efficient way of translating less costly available data, such as particle-size distributions, soil textures and other geophysical measurements, to soil hydraulic parameters required for numerical simulations and other applications. The ANN PTFs need to be trained before being used to transfer indirect measurements to soil hydraulic parameters. The traditional training process, in general, is to adjust ANN's coefficients to solely minimize the difference between the estimated and measured soil hydraulic parameters. The training process, however, did not consider the distributions of soil hydraulic parameters and the trained neural networks may yield improper distributions, which may severely affect probabilistic predictions. We incorporate the distributions of the soil hydraulic parameters into the ANN PTF development. In addition, it has been observed that PTFs can introduce unrealistic correlations between the output parameters. The unwanted artificial correlations need to be penalized during the training process, since it is well known that parameter correlations have significant effect on predictions. We achieve these two goals by adding two regularization terms to the ANN objective functions. A suite of new neural network models are developed to estimate soil hydraulic parameters. These neural network models have the same input and output variables, but different objective functions, which incorporate sequentially the site soil hydraulic parameter measurements, parameter probability distributions, and parameter correlations.

Zhao, Y.; Zhu, J.; Ye, M.; Meyer, P. D.; Pan, F.; Hassan, A. E.

2007-12-01

169

The Effect of the Spatial Sensitivity of TDR on Inferring Soil Hydraulic Properties from Water Content Measurements Made during the Advance of a Wetting Front  

Microsoft Academic Search

ing designs during the advance of a wetting front is presented. Numeri- umes farther from the rods. Despite these advances, cal inversion of these water breakthrough curves is performed to es- timate the soil hydraulic parameters. Time domain reflectometry there has been little consideration of the effects of this probes with larger rod separations show less impact on the flow

Ty P. A. Ferré; Henrik H. Nissen; Jirka Šim?nek

2002-01-01

170

A preliminary assessment of soil hydraulic properties, and their implications for agro forestry management in Grenada, West Indies  

Microsoft Academic Search

Soil texture, bulk density, air capacity and soil permeability at six sites showed considerable varia- tions between sites and within profiles. Differences between sites are related to variations in land use, site position and geomorphic history, and eluviation processes within the profile. Near surface horizons are charac- terized by low bulk density, high air capacity and high permeability with Ks

J. L. TERNAN; A. G. WILLIAMS; K. SOLMAN

171

Scaling Approach to Deduce Field Unsaturated Hydraulic Properties and Behavior from Laboratory Measurements on Small Cores  

Microsoft Academic Search

Hydraulic properties should be determined at the scale of the pro- cess modeled. The methods to hydraulically characterize a soil in situ remain extremely difficult to implement, requiring measurements of water content and pressure head with adequate time-depth resolution. We recently proposed a method that reduced the number of field measurements required for complete field hydraulic characteriza- tion. In this

A. Basile; A. Coppola; R. De Mascellis; L. Randazzo

2006-01-01

172

The sensitivity of convective precipitation to soil texture distribution and soil hydraulic characteristics  

NASA Astrophysics Data System (ADS)

The formation of convective clouds is regulated by both the characteristics of the atmosphere and the land surface. The effect of land-surface properties can be significant via the thermal and hydraulic exchange between the soil-vegetation system and the atmosphere. In this study the sensitivity of convective precipitation to soil texture distribution and to soil hydraulic characteristics is analyzed. Case studies were performed by Version 3 of the Penn State - NCAR MM5 (Fifth-generation Mesoscale Model) modeling system. Its land-surface model is the Noah Land Surface Model. It consists of a multilayer soil model and a single-layer snow and canopy model. The ten case studies include storm events, mostly with heavy rain, without any preference on the synoptic features. In simulations the effect of soil texture distribution was investigated by replacing the original distribution in Hungary according to measurements given by the RISSAC (Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences). All of the USA soil hydraulic properties were also replaced by mostly recalculating them from Hungarian field measurements. 24 hours accumulated precipitation fields were analyzed using skill score analysis and significance tests. Results indicate that the aforementioned characteristics have a not negligible effect on precipitation intensity and distribution in heavy precipitation events without disturbing the large scale pattern of the atmospheric circulation.

Breuer, H.; Ács, F.; Rubel, F.; Horváth, Ž.

2009-09-01

173

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

USGS Publications Warehouse

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 were successfully estimated by numerical inversion of transient experiments. The inverse method was then evaluated by comparing estimated soil hydraulic properties with those determined independently using an equilibrium analysis. The optimized soil hydraulic properties compared well with those determined using equilibrium analysis and steady state experiment. Multirotation experiments in a centrifuge not only offer significant time savings by accelerating time but also provide significantly more information for the parameter estimation procedure compared to multistep outflow experiments in a gravitational field. Copyright 2005 by the American Geophysical Union.

Simunek, J.; Nimmo, J. R.

2005-01-01

174

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

NASA Astrophysics Data System (ADS)

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 were successfully estimated by numerical inversion of transient experiments. The inverse method was then evaluated by comparing estimated soil hydraulic properties with those determined independently using an equilibrium analysis. The optimized soil hydraulic properties compared well with those determined using equilibrium analysis and steady state experiment. Multirotation experiments in a centrifuge not only offer significant time savings by accelerating time but also provide significantly more information for the parameter estimation procedure compared to multistep outflow experiments in a gravitational field.

Šim?nek, Jirka; Nimmo, John R.

2005-04-01

175

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

Microsoft Academic Search

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

T. N. Narasimhan

1998-01-01

176

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

177

Influence of long-term tillage and crop rotations on soil hydraulic properties in the U.S. Pacific Northwest  

Technology Transfer Automated Retrieval System (TEKTRAN)

In the semi-arid region of the Pacific Northwest, USA, no-tillage continuous spring cereal and spring cereal/chemical fallow rotations are being examined as alternatives to the traditional winter wheat/summer fallow rotation for improving soil and water conservation. There is limited information, ho...

178

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...

179

Evaluation of Pedo-transfer Functions For Unsaturated Soil Hydraulic  

NASA Astrophysics Data System (ADS)

Eight well known and accepted pedo-transfer functions used for evaluation of soil hy- draulic conductivity (saturated and unsaturated) from routinely available soil data are reviewed. A comprehensive data set containing detailed measurements of 63 German soil horizons, to which none of the models had been calibrated before, was used for evaluation of the pedo-transfer functions. Only pedo-transfer functions which have shown good results in the past were considered for the comparison. The statistical analysis of the eight functions shows, that the models of Vereecken et al. (1990) and Wösten (1997) perform best in terms of prediction of the unsaturated hydraulic con- ductivity of soils. Evaluation of the unsaturated hydraulic conductivity by the pedo- transfer functions shows on average better correlations if the saturated hydraulic con- ductivity (an input parameter) is also obtained from predictions of pedo-transfer func- tions rather than directly from experiments. This outcome is attributed to a dependence of the saturated hydraulic conductivity on soil structure i.e. macropores, while the unsaturated hydraulic conductivity is generally more dependent on soil texture. The deviating results of estimated soil hydraulic conductivity as compared to the experi- mental data indicate that the use of pedo-transfer functions based only on estimated soil hydraulic parameters, must be carried out with great caution.

Wagner, B.; Tarnawski, V. R.; Hennings, V.; Müller, U.; Wessolek, G.; Stoffregen, H.

180

Hydraulically powered soil core sampler and its application to soil density and porosity estimation  

Microsoft Academic Search

The design of a hydraulically powered soil core sampler used to collect undisturbed soil samples at different depths in the field is presented. The hydraulic actuation of the coring probe reduces the physical effort and time required by the operators. The device is constructed from a three-point hitch frame equipped with a gearbox, retractable legs, hydraulic cylinder and probe. The

Nidal H Abu-Hamdeh; Hamid F Al-Jalil

1999-01-01

181

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...

182

Study on The Spatial Variability of Soil Hydraulic Conductivities in Heterogenic Karst Slopes  

NASA Astrophysics Data System (ADS)

The understanding of the spatial variability of soil hydraulic property is crucial to the study of several hydrological and ecological processes in karst environments. Karst environments are extremely fragile because of thin soil, small soil water holding capacity and quite high soil distribution heterogeneity. A marked intensification of agricultural land use and deforestation due to increase of population and thus expansion of agricultural areas has made the karst environment even more delicate. In this study, soil properties and soil hydraulic conductivities (K) along six land use types karst slopes were measured, each of which has a different karst microhabitats including the Soil Surface (thick soil layer), Rock-Soil (thin soil layer contacting rock surface) and Karren Soil (soil filled in rock crevices or fractures). The statistical results from the measurements show that: 1. The soil hydraulic conductivities in forest area were quite high compared to non-karst areas because of the thin soil and cracks and fractures well development in carbonate rocks. 2. Land use changes strongly affect the soil properties and soil hydraulic conductivities (K) in these karst microhabitats. Compared with undisturbed forest karst slopes, the K values are 54.5% and 61.8% smaller in the fire or cut and the pasture human disturbed areas, respectively. Human activities significantly change soil properties and decrease permeability of soils when the forest was destroyed. Measured K values were 0.3~1cm/min and 0.2~0.3 cm/min for the forest soils and the human disturbed areas, respectively. However, these decreasing trends of the K values in the three types of karst microhabitats were different. The K values were decreased significantly in the Soil Surface and Rock-Soil microhabitats, compared to that of Karren Soil microhabitats when the land use change from forest to cutting or pasture area. The K values decreased 71.9% and 79.6% in Soil Surface and Rock-Soil microhabitats, and it were reduced by 36.5% in Karren Soil. It means that soil in rock crevices or fractures microhabitats in karst slopes were less influenced by the land use changes. These results offer useful information to further investigate the response of ecosystem evolution to hydrodynamic processes in highly heterogeneity karst slopes.

Peng, Tao; Fang, Sheng; Meng, Fan-De; Wang, Shi-Jie

2013-04-01

183

Mechanical and hydraulic resistance relations in crust-topped soils  

Microsoft Academic Search

The formation of soil surface crusts leads to increased mechanical and hydraulic resistances. In this study, changes and relationships of both resistances under simulated sprinkle irrigation (or rainfall), and sprinkle followed by flooding, were examined. Results indicated that a silt-loam soil developed a thicker surface crust than a clay soil for any given kinetic energy (KE). Crusts as thick as

M. N. A. Bedaiwy

2008-01-01

184

Mass transfer in soils with local stratification of hydraulic conductivity  

Microsoft Academic Search

The two-region model was developed originally to describe nonsorbing chemical transport in soils with dead-end pores based on the concept of mobile and immobile regions in the soil. It has been shown that the model can simulate solute transport in soils with local stratification, or inhomogeneity, of hydraulic conductivity. However, the physical basis of the model becomes questionable, since the

L. Li; D. A. Barry; P. J. Culligan-Hensley; K. Bajracharya

1994-01-01

185

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...

186

FACTORS AFFECTING THE HYDRAULIC BARRIER PERFORMANCE OF SOIL-BENTONITE MIXTURE CUT-OFF WALL  

NASA Astrophysics Data System (ADS)

Containment technique using cut-off walls is a valid method against contaminants in subsurface soil and/or groundwater. This paper states laboratory testing results on hydraulic barrier performance of Soil-Bentonite (SB), which is made by mixing bentonite with in-situ soil. Since the bentonite swelling is sensitive to chemicals, chemical compatibility is important for the hydraulic barrier performance of SB. Hydraulic conductivity tests using flexible-wall permeameter were conducted on SB specimens with various types and concentrations of chemicals in the pore water and/or in the permeant and with various bentonite powder contents. As a result, hydraulic barrier performance of SB was influenced by the chemical concentration in the pore water of original soil and bentonite powder content. In the case that SB specimens have damage parallel to the permeating direction, no significant leakage in the SB occurs by the self-sealing property of SB. In addition, the hydraulic conductivity values of SB have excellent correlation with their plastic indexes and swelling pr essures, thus these properties of SB have some possibility to be indicators for estimation of the hydraulic barrier performance of SB.

Takai, Atsushi; Inui, Toru; Katsumi, Takeshi; Kamon, Masashi; Araki, Susumu

187

Indirect estimation of near-saturated hydraulic conductivity from readily available soil information  

Microsoft Academic Search

Application of process-based water flow and solute transport models is often hampered by insufficient knowledge of soil hydraulic properties. This is certainly true for dual- or multi-porosity models that account for non-equilibrium flow of water in macropores, where the saturated ‘matrix’ hydraulic conductivity is a particularly critical parameter. Direct measurement is possible, but this is impractical for larger scale studies

N. J. Jarvis; L. Zavattaro; K. Rajkai; W. D. Reynolds; Pa Olsen; M. McGechan; M. Mecke; B. Mohanty; P. B. Leeds-Harrison; D. Jacques

2002-01-01

188

[Ecological effect of recirculated landfill leachate with different hydraulic loading on plant-soil system].  

PubMed

The ecological effect of irrigating recirculated leachate with different hydraulic loading on bermudagrass (Cynodon dactylon) and soil system was evaluated. The results show that leachate irrigation with hydraulic loading of 2.77-12.00 mm d(-1) leads to high chlorophyll content, low proline (Pro) content, as well as low malondialdehyde (MDA) and H2O2 content. Soil enzyme activities, respirations, microbial biomass and ratio of biomass carbon to organic carbon (Cmic/Corg) are rather higher. Among leachte irrigation group, leachate irrigation with hydraulic loading of 6.46-10.15 mm x d(-1) leads to declined proline, increased chlorophyll content, low POD activity and low content of MDA and H2O2. Soil bio-activity related parameters, such as soil enzyme activities, respirations, microbial biomass and Cmic/Corg are all enhanced at 6.46-10.15 mm x d(-1) of hydraulic loading. However, when hydraulic loading increases to 12.00 mm x d(-1) or declines to 2.77-4.16 mm x d(-1), the stress of irrigation on bermudagrass is aggravated, and soil bioactivity declines. The results reveal that leachate irrigation could alleviate the stress of environment on bermudagrass and improve the bio-activity of soil. The positive effect of leachate irrigation on the plant-soil system might be contributed to changes of soil water and physico-chemical property after leachate irrigated to the soil. The experimental results suggest that leachate irrigation could benefit plant-soil system, especially when controlled at suitable hydraulic loading. PMID:16850839

Wang, Ru-yi; He, Pin-jing; Shao, Li-ming; Yuan, Li; Li, Guo-jian

2006-05-01

189

Estimating sphagnum peat hydraulic properties from laboratory evaporation experiments  

NASA Astrophysics Data System (ADS)

In ombrotrophic peatlands, the equilibrium between the production and decay of organic matter is principally controlled by the moisture state and its oxic/anoxic conditions in the vadose zone. In order to predict a peatland's fate, it is necessary to describe the hydraulic processes with models correctly. However, no suitable systematic and mechanistic model exists to date. This knowledge gap is attributed to the complexity of peatland ecosystem processes. The reasons for this probably include spatial and temporal heterogeneities, swelling and shrinkage phenomena, hydrophobicity and difficulties in representative sampling. For a valid description of the non-linear processes involved, peat soil hydraulic properties play an intricate part. Their determination requires taking the characteristics mentioned into considered. Our research aims to quantify these characteristics and, eventually, to establish a model in order to numerically simulate the water fluxes in the unsaturated zone. We started with laboratory measurements with which we determined peat soil hydraulic properties. Our study is based on an ombrotrophic peatland site in the Harz Mountains (Germany). Samples were taken over the entire unsaturated part of a Histosol profile. Before the laboratory experiments, samples were frozen, cut to shape and subsequently fully saturated in a vacuum. We used the same sample specimen for the saturated hydraulic conductivity and the simplified evaporation method. Results show that the hydraulic properties rapidly change in the upper-most layers with a step-like change over a small distance, close to the permanently saturated zone. We also show that the swelling and shrinkage is considerable, which means that traditional concepts based on the rigidity of the porous media are not applicable. Furthermore, the results indicate that the frequently used van Genuchten model cannot describe our data very well.

Weber, Tobias K. D.; Durner, Wolfgang

2013-04-01

190

Multi-scale hydraulic pedotransfer functions for Hungarian soils  

Microsoft Academic Search

Water and nutrient balance are among the main concerns about the sustainability of our soils. Numerous computer models have been developed to simulate soil water and solute transport and plant growth. However, use of these models has often been limited by lack of accurate input parameters. Often, the limiting input parameters are water retention and hydraulic conductivity. For many applications,

A. Nemes

2003-01-01

191

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

192

Soil Hydraulic Characteristics of a Small Southwest Oregon Watershed Following High-Intensity Wildfires1  

Microsoft Academic Search

The Angel Fire of September, 1987 caused extensive damage to second growth forest in the south fork drainage of Cow Creek, 55 km northeast of Grant's Pass, Oregon, USA. The fire was characterized by a high-intensity burn over areas of steep topography. The areal distribution of soil hydraulic properties in a small, tributary watershed following high-intensity wildfire is examined using

David S. Parks; Terrance W. Cundy

1989-01-01

193

Soil Taxonomy and Soil Properties.  

National Technical Information Service (NTIS)

The 16 papers in this report deal with the following areas: soil taxonomy; an overview; diagnostic soil horizons in soil taxonomy; soil moisture and temperature regimes in soil taxonomy; particle size and mineralogy in soil taxonomy; soil series and soil ...

1977-01-01

194

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

195

Influence of three-parameter conversion methods between van Genuchten and Brooks-Corey Functions on soil hydraulic properties and water-balance predictions  

NASA Astrophysics Data System (ADS)

The Brooks-Corey functions are commonly used in hydrologic models, with parameters obtained by fitting the functions directly to measured soil water retention data or by conversion methods from the van Genuchten functions which are continuous across the domain of matric suctions. Problems in fitting the BC functions directly to the retention data motivated use of the conversion methods. However, differences in converted parameters could significantly influence model predictions. We compared the direct fitting method and the conversion methods of Lenhard et al., Morel-Seytoux et al., and van Genuchten using measured water retention data during drainage and determined the influence of these methods on hydrological predictions when the converted parameters were used in the root zone water quality model. The conversion methods had significant influence on predictions of water retention, hydraulic conductivity, runoff, and evapotranspiration, with the observed level of significance (p ? 0.006) much lower than the test level of significance (? = 0.05). The method of Morel-Seytoux et al. inadequately described measured water retention data (p=0.027), whereas the other two methods adequately described the data at relatively high suctions (p ? 0.687), deviations occurred around the air-entry suction. The method of Lenhard et al. best reproduced the characteristics of the Brooks-Corey functions (p ? 0.31) and could be used to obtain the Brooks-Corey parameters simply and reproducibly.

Ma, Qingli; Hook, James E.; Ahuja, Laj R.

1999-08-01

196

Pedotransfer function application for estimation of soil hydrophysical properties using parametric methods  

Microsoft Academic Search

Soil hydraulic properties are needed as input data to describe and simulate the transport of water and solutes in the soil profile. The most important characteristics are the soil moisture retention curve (SMRC) ?(h) and the hydraulic conductivity function k(?) or k(h), where ? is the soil moisture content, h is the pressure head and k is the hydrau- lic

S. Matula

2007-01-01

197

Comparison of Soil Hydraulic Parameterizations for Mesoscale Meteorological Models.  

NASA Astrophysics Data System (ADS)

Soil water contents, calculated with seven soil hydraulic parameterizations, that is, soil hydraulic functions together with the corresponding parameter sets, are compared with observational data. The parameterizations include the Campbell/Clapp-Hornberger parameterization that is often used by meteorologists and the van Genuchten/Rawls-Brakensiek parameterization that is widespread among hydrologists. The observations include soil water contents at several soil depths and atmospheric surface data; they were obtained within the Regio Klima Projekt (REKLIP) at three sites in the Rhine Valley in southern Germany and cover up to 3 yr with 10-min temporal resolution. Simulations of 48-h episodes, as well as series of daily simulations initialized anew every 24 h and covering several years, were performed with the “VEG3D” soil-vegetation model in stand-alone mode; furthermore, 48-h episodes were simulated with the model coupled to a one-dimensional atmospheric model. For the cases and soil types considered in this paper, the van Genuchten/Rawls-Brakensiek model gives the best agreement between observed and simulated soil water contents on average. Especially during episodes with medium and high soil water content, the van Genuchten/Rawls-Brakensiek model performs better than the Campbell/Clapp-Hornberger model.

Braun, Frank J.; Schädler, Gerd

2005-07-01

198

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...

199

Estimating Saturated Hydraulic Conductivity from Soil Water Retention Curve using Neural Networks  

NASA Astrophysics Data System (ADS)

Study of soil hydraulic properties like saturated and unsaturated hydraulic conductivity is required in the environmental investigations. Since, direct measurement of soil hydraulic properties is time consuming and expensive, indirect methods such as pedotransfer function and artificial neural networks (ANN) have been developed based on the readily available soil characteristics. In this study, we used soil water retention data i.e. fractal dimension, air entry value and effective porosity, as well as bulk density and developed artificial neural networks in order to estimate saturated hydraulic conductivity. Total of 142 soil samples of the UNSODA, GRIZZLY and Puckett et al. (1985) databases was divided into two groups as 114 for the development and 28 for the validation of ANN model. We used multi-layer perceptron model with 4 layers as the inputs and one layer as the output of ANN model and back propagation algorithm for training procedure. The activation function was selected LOGSIG in the middle and exist layers. The values of statistical parameters such as coefficient of determination (R2) and mean square error (MSE) showed that the best number of neurons in the middle layer of ANN model was 24. We also compared the developed ANN model with Rawls et al. (1993) and Rawls et al. (1998) models using 28 soil samples. The results showed that developed ANN model estimates saturated hydraulic conductivity better than the other methods. The AIC values of ANN, Rawls et al. (1993) and Rawls et al. (1998) were obtained 291.8, 322.3 and 316.4, respectively.

Ghanbarian-Alavijeh, B.; Liaghat, A. M.; Sohrabi, S.

2009-04-01

200

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

201

Effective Hydraulic Conductivity of Unsaturated Isotropic Soils with Multidimensional Heterogeneity  

Microsoft Academic Search

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 systems behavior with information collected at a much smaller scale. Realizing that a saturated system can be considered as a special state of

Z. Fred Zhang

2010-01-01

202

Upscaling the Unsaturated Hydraulic Conductivities of Isotropic Soils  

Microsoft Academic Search

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

Z. F. Zhang

2008-01-01

203

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...

204

Three-region Campbell Model for Unsaturated Hydraulic Conductivity in Undisturbed Soils  

Microsoft Academic Search

region is often better described using multimodal-distri- bution functions. A three-region Campbell (TRC) type model for predicting undis- A limited number of models for predicting the unsatu- turbed soil unsaturated hydraulic conductivity from water retention rated hydraulic conductivity (K) in soils with multimodal is presented. The model assumes that hydraulic conductivity follows separate Campbell functions within the macropore (matric head

T. G. Poulsen; P. Moldrup; B. V. Iversen; O. H. Jacobsen

2002-01-01

205

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

Microsoft Academic Search

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

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

2002-01-01

206

Salinity and sodicity induced changes in dispersible clay and saturated hydraulic conductivity in sulfatic soils  

Microsoft Academic Search

Irrigation is becoming a more commonly used practice on glacially derived soils of the Northern Great Plains. Threshold salinity and sodicity water quality criteria for soil?water compatibility in these sulfatic soils are not well defined. This study was conducted to relate soil salinity and sodicity to clay dispersion and saturated hydraulic conductivity (Ksat) in four representative soils. Soil salinity (EC

Gene Springer; Brian J. Wienhold; J. L. Richardson; L. A. Disrud

1999-01-01

207

Electromagnetic Inversion of GPR Signals and Subsequent Hydrodynamic Inversion to Estimate Effective Vadose Zone Hydraulic Properties  

Microsoft Academic Search

ABSTRACT,methods, intensive efforts have been undertaken to sup- plement,the scarcity of hydrogeological,data with densely Wecombineelectromagneticinversionofgroundpenetratingradar sampled geophysical data (Beres and Haeni, 1991; Ru- (GPR) signals with hydrodynamic inverse modeling to identify the effective soil hydraulic properties of a sand in laboratory conditions. bin et al., 1992; Hubbard et al., 1997; Hubbard and Ru- Ground penetrating radar provides soil moisture time

S. Lambot; M. Antoine; I. van den Bosch; E. C. Slob; M. Vanclooster

2004-01-01

208

Determination of till hydraulic properties for modelling flow and solute transport in a forested hillslope  

NASA Astrophysics Data System (ADS)

Shallow till layers typically overlay bedrock in forested areas in the boreal region. In forested tills, preferential flowpaths related to the soil structure have a decisive influence on hydrogeological properties such as the soil hydraulic conductivity. Hydraulic conductivity is also proven to depend on the observation scale. Traditional soil core samples cannot capture the impact of soil structure on hillslope scale conductivities. Measurements and observations made at different scales, combined with simulation models, are essential for investigating conductivity properties and flow and transport processes in forest soils. This study combined a set of soil analyses and field experiments with physics-based modelling to investigate the hydraulic properties of a forested till slope in Finland. The main objective was to i) determine the saturated hydraulic conductivity in the study slope with methods related to different scales, and to ii) study the utilisation of the conductivity results in modelling flow and solute transport in the slope. Soil sampling, dye, and ion tracer experiments were conducted in a forested hillslope in Eastern Finland. In the 20 m long study section of the slope the mean slope was about 15 %. The haplic podsol profile above bedrock had a thickness of 0.8 m and was formed of sandy till. The soil was very stony and heterogeneous in terms of granularity and pore size distribution. Granularity, porosity and proportion of macropores reduced clearly with depth. Dye tracer experiments revealed three types of preferential flow routes in the slope: i) stone surfaces, ii) areas of coarse-grained soil material, and iii) decayed root channels. Both living roots and preferential flowpaths reached the transitional zone of the podsol at about 0.5 m depth, but living roots were not found to function unequivocally as preferential flowpaths. The saturated hydraulic conductivity was determined using three methods: i) from soil core samples in laboratory, ii) with Guelph permeameter in the field, iii) and by means of inverse modelling. The inverse model application was based on calibration of a one-dimensional groundwater model against data on groundwater levels in the study slope. Conductivities of the different soil horizons were adjusted to reproduce the measured groundwater levels of a recession period after artificial irrigation. Conductivity results, together with soil physical and water retention data were applied to parameterise a three-dimensional flow and advection-dispersion model. The model was used to simulate the transport of a chloride tracer plume in the study slope during artificial irrigation. A line-type irrigation source was installed upslope from the study section of the slope. Changes in groundwater levels and chloride concentrations within the study section were observed through well screens. Chloride as a conservative tracer provided an indicator for subsurface flow in the study slope. Intensive irrigation rates were applied to initiate fast lateral preferential flow. Saturated hydraulic conductivities obtained with the three methods were remarkably different. Conductivities obtained with the Guelph permeameter and the groundwater model reduced clearly with soil depth. Higher conductivities near soil surface were due to loose soil structure and preferential flowpaths. Soil core samples yielded the lowest estimates for the saturated hydraulic conductivity, as they represented the small-scale conductivity of the soil texture and soil matrix. The hillslope-scale groundwater model produced the highest estimates that characterised the large-scale structural properties and their impact on lateral preferential flow. Average saturated hydraulic conductivities in the soil core samples were 6E-6 m/s in the eluvial horizon, transition zone and subsoil, and 1E-5 m/s in the illuvial horizon. The average conductivities based on the Guelph measurements varied from 2E-5 m/s in the subsoil to 5E-5 m/s in the eluvial horizon, and based on the groundwater model from 6E-5 m/s in the subsoil to 3E-4 m/s in the elu

Laine-Kaulio, H.; Karvonen, T.; Koivusalo, H.; Lauren, A.; Saastamoinen, S.

2009-04-01

209

Root Water Extraction and Limiting Soil Hydraulic Conditions Estimated by Numerical Simulation  

Microsoft Academic Search

Root density, soil hydraulic functions, and hydraulic head gra- dients play an important role in the determination of transpiration- rate-limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water extraction. The average soil water con- tent at the moment root water potential dropped below a

Quirijn de Jong van Lier; Klaas Metselaar; Jos C. van Dam

2006-01-01

210

Spatio-temporal variation of anisotropy of saturated hydraulic conductivity in a tilled sandy loam soil  

Microsoft Academic Search

Knowledge on anisotropy of saturated hydraulic conductivity can improve the understanding of transport phenomena in soil. We hypothesized that saturated hydraulic conductivity (Ks) in the upper part of the root zone of an agricultural sandy loam soil was anisotropic at different soil depths and times after tillage. Ks was measured on undisturbed 100cm3 core samples taken in the horizontal and

C. T. Petersen; A. Trautner; S. Hansen

2008-01-01

211

Effect of sheep stocking intensity on soil physical properties and dry matter production on a Pallic Soil in Southland  

Microsoft Academic Search

This 3?year study examined the extent of damage to soil physical properties of a Pukemutu silt loam (Pallic Soil) and the loss of ryegrass?white clover pasture production caused by intensive winter grazing at 1800 sheep ha. Macroporosity, pore size distribution, bulk density, and hydraulic conductivity were measured at 5?cm incremental soil depths to 15 cm to assess changes in soil

J. J. Drewry; J. A. H. Lowe; R. J. Paton

1999-01-01

212

Hydraulic properties of adsorbed water films in unsaturated porous media  

Microsoft Academic Search

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

Tetsu K. Tokunaga

2009-01-01

213

Hydraulic properties of adsorbed water films in unsaturated porous media  

Microsoft Academic Search

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

Tetsu K. Tokunaga; Tetsu K

2009-01-01

214

Impact of soil hydraulic parameter uncertainty on soil moisture modeling  

Microsoft Academic Search

the geographical origin of a PTF has a high impact on the pdf of the SHPshigher-order moments should be included when assessing the soil moisture pdfcentral point is an alternative to standard SHPs to determine an average SHP set

Lien Loosvelt; Valentijn R. N. Pauwels; Wim M. Cornelis; Gabriëlle J. M. De Lannoy; Niko E. C. Verhoest

2011-01-01

215

A Statistical Model for Predicting Unsaturated Hydraulic Properties of Deep Sediments at the Idaho National Engineering and Environmental Laboratory  

Microsoft Academic Search

The development and application of property-transfer functions is an important approach for predicting unsaturated hydraulic properties from more easily measured bulk properties. At the Idaho National Engineering and Environmental Laboratory (INEEL), the unsaturated zone is comprised of thick basalt flow sequences interbedded with thinner sedimentary layers. Buried hazardous waste in the surficial soil is a possible source of contamination to

K. A. Winfield; J. R. Nimmo

2003-01-01

216

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

217

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

NASA Astrophysics Data System (ADS)

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.

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

2007-08-01

218

Effect of land use change on the dynamic behaviour of structural properties of an Andisol in southern Chile under saturated and unsaturated hydraulic conditions  

Microsoft Academic Search

Soil structure dependent properties are normally dynamic due to different processes occurring in the soil. However, in classic hydraulic modelling these interactions are generally ignored and may result in higher uncertainty of predicted effects. Such investigations are especially relevant in volcanic ash soils in southern Chile because of their intrinsic properties and the climatic conditions of the region. Therefore, the

J. Dörner; D. Dec; X. Peng; R. Horn

2010-01-01

219

Influence of soil, land use and climatic factors on the hydraulic conductivity of soil  

NASA Astrophysics Data System (ADS)

Due to inadequate data support, existing algorithms used to estimate soil hydraulic conductivity, K, in (eco)hydrological models ignore the effects of key site factors such as land use and climate and neglect the significant effects of soil structure on water flow at and near saturation. These limitations may introduce serious bias and error into predictions of terrestrial water balances and soil moisture status, and thus plant growth and rates of biogeochemical processes. To resolve these issues, we collated a new global database of hydraulic conductivity measured by tension infiltrometer under field conditions. The results of our analyses on this dataset contrast markedly with those of existing algorithms used to estimate K. We show that the saturated hydraulic conductivity, Ks, in topsoil (< 0.3 m depth) is only very weakly related to texture. Instead, Ks depends more strongly on bulk density, organic carbon content and land use and management factors. In this respect, the results show that arable sites have, on average, ca. 2 to 3 times smaller Ks values than natural vegetation, forests and perennial agriculture. The data also clearly demonstrates that clay soils have smaller K in the soil matrix and thus a larger contribution of soil macropores to K at and near saturation.

Jarvis, N.; Koestel, J.; Messing, I.; Moeys, J.; Lindahl, A.

2013-08-01

220

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

221

Monitoring infiltration with time-lapse relative gravity: An option for non-invasive determination of soil hydraulic parameters?  

NASA Astrophysics Data System (ADS)

Various hydrogeophysical methods have been proposed to monitor infiltration and determine soil hydraulic parameters using coupled hydrogeophysical inversion. Methods include electrical resistivity tomography (ERT), ground penetrating radar (GPR, both surface and cross-hole) as well as passive microwave radiometry. Depending on the measurement set-up, both ERT and GPR can provide high-resolution images of soil water content. However, soil water content monitoring with both ERT and GPR depends on the validity and accuracy of empirical relationships linking soil water content to electrical resistivity (ERT) and dielectric permittivity (GPR). This has emerged as one of the main limitations for the performance of soil water monitoring with both GPR and ERT. As an alternative, ground-based time-lapse relative gravity (TLRG) is proposed for infiltration monitoring. The method is based on the fact that water content changes in the subsurface constitute changes in subsurface density and can be monitored as changes in the gravitational field. The advantage of TLRG over GPR and ERT is that TLRG directly senses mass changes. Thus, no empirical relationship is required to link water content changes to changes in a geophysical property. This study evaluates the performance of TLRG for infiltration monitoring and hydrogeophysical inversion of soil hydraulic parameters. Results include both synthetic infiltration experiments and a real-world infiltration experiment monitored with TLRG. In the synthetic experiments, soil water content profiles are generated using analytical infiltration solutions. Soil water content profiles are translated into gravity signals and are corrupted with random noise to produce synthetic data. The synthetic data is subsequently used in a hydrogeophysical inversion of soil hydraulic parameters. Fitted parameter confidence intervals and covariances are evaluated. The same inversion procedure is used on the real-world data. The results show that TLRG data contains information that constrains soil hydraulic parameters. However, useful signal-to-noise ratios require large amounts of infiltration. TLRG sensing of infiltration is thus limited to deep soil profiles and long-duration infiltration events.

Bauer-Gottwein, P.

2012-04-01

222

HYDRAULIC CONDUCTIVITY OF A SILT LOAM SOIL AS AFFECTED BY SAMPLE LENGTH  

Microsoft Academic Search

Soil hydraulic conductivity is often measured with small laboratory samples. Due to sampling artifacts or spatial variability, smallscale laboratory samples may not yield representative conductivity measurements. The objective of this study was to analyze the effect of sample length on the saturated and nearsaturated hydraulic conductivity (K). An undis- turbed soil core of 9 cm diameter and 25 cm length

P. Fuentes; M. Flury

223

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

EPA Science Inventory

Nocturnal increases in water potential (¿) and water content (¿) 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 ...

224

EFFECTS OF ELECTROOSMOSIS ON SOIL TEMPERATURE AND HYDRAULIC HEAD: II. NUMERICAL SIMULATION  

EPA Science Inventory

A numerical model to simulate the distributions of voltage, soil temperature, and hydraulic head during the field test of electroosmosis was developed. The two-dimensional governing equations for the distributions of voltage, soil temperature, and hydraulic head within a cylindri...

225

Sensitivity Screening the van Genuchten/Mualem Soil Hydraulic Parameters  

NASA Astrophysics Data System (ADS)

A screening evaluation, including a Morris one-factor-at-a-time (OAT) sensitivity analysis (SA), was performed to evaluate the relative elementary and secondary effects for six of the seven van Genuchten Mualem (VGM) hydraulic model parameters used in predicting water retention and movement through a coarse-textured soil profile under atmospheric boundary conditions. The tortuosity parameter (l) was not evaluated in the OAT analysis because it is generally considered a fitting parameter with little physical significance, and the lack of reliable data concerning the parameters value and distribution as a function of soil texture. Simulated data sets were created based on coarse textural classes using the HYDRUS-1D code, a one dimensional finite element water and solute transport model based on Richards’ equation, to eliminate bias and uncertainty associated with site heterogeneity and measurement error inherent to field data, as well as evapo-transpiration. For each textural class, the simulated data set consisted of hourly estimates of volumetric water content values at 30 and 60 cm soil depths, assuming a homogeneous 100 cm soil profile with atmospheric boundary conditions based on hourly precipitation for the month of February. Initial water distribution profiles were based on average sensor readings for the field site recorded at the beginning of the simulation interval. For the Morris OAT analysis, a set of random input parameter values was chosen from within the upper and lower parameter bounds defined by the extreme 95% confidence intervals reported for coarse-textured soil materials assuming an even parameter distribution. Each parameter was then varied independently consistent with the Morris method. Model results for the new parameter set were then compared to the ideal simulated data for each soil texture, i.e., RSSE. Of the five parameters evaluated, SA indicated that n and ?sat were the most sensitive parameters, and ? was found to be the least.

Seaman, J. C.; Singer, J. H.; Radcliffe, D. E.

2009-12-01

226

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

227

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.

228

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

229

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.

230

Changes in soil water content in the rhizosphere of Artemisia ordosica: Evidence for hydraulic lift  

Microsoft Academic Search

Hydraulic lift by Artemisia ordosica was investigated in a greenhouse study. The root system was grown in two soil compartments: a drier, upper soil and a wetter, deep soil. Diurnal soil water content (Øv) at 10, 25, and 35cm in the top pots was measured at 4-h intervals with time domain reflectometry. There was an increase in Øv at all

D.-H. Xu; J.-h. Li; X.-W. Fang; G. Wang

2007-01-01

231

Stress–strain effects in structured unsaturated soils on coupled mechanical and hydraulic processes  

Microsoft Academic Search

The stress–strain processes in structured unsaturated arable and forest soils depend very much on the internal soil strength and on the existing hydraulic and mechanical boundary conditions. These variables affect soil deformation by compaction and shearing to a great extent. As soon as the internal soil strength, defined as the precompression stress value, is exceeded by external forces, an intense

Rainer Horn

2003-01-01

232

Role of precipitation uncertainty in the estimation of hydrologic soil properties using remotely sensed soil moisture in a semiarid environment  

Microsoft Academic Search

The focus of this study is on the role of precipitation uncertainty in the estimation of soil texture and soil hydraulic properties for application to land-atmosphere modeling systems. This work extends a recent study by Santanello et al. (2007) in which it was shown that soil texture and related physical parameters may be estimated using a combination of multitemporal microwave

Christa D. Peters-Lidard; David M. Mocko; Matthew Garcia; Joseph A. Santanello Jr; Michael A. Tischler; M. Susan Moran; Yihua Wu

2008-01-01

233

Characterizing scale-dependent spatial relationships between soil properties using multifractal techniques  

Microsoft Academic Search

Measurement of soil hydraulic properties under field conditions is expensive and time consuming. Indirect methods that include estimating soil water properties from readily available soil physical data (known generally as pedotransfer functions) are preferred options. However, since environmental factors and processes operate at multiple spatial scales, the accuracy and reliability of these indirect techniques is often below expectations. The objective

Takele B. Zeleke; Bing C. Si

2006-01-01

234

Porous Media With Linearly Variable Hydraulic Properties  

Microsoft Academic Search

The similar media concept is reformulated and extended to allow for analysis of unsaturated or saturated flow in a system of parallel nonhomogeneous one-, two-, or three-dimensional soil profiles. The resulting invariance of Richards' equation for a set of soil profiles is valid for certain initial and boundary conditions only. Simple techniques are outlined and demonstrated by examples for direct

T. Vogel; M. Cislerova; J. W. Hopmans

1991-01-01

235

Characterization and cartography of topsoil hydraulic properties in a French mountainous peri-urban catchment  

NASA Astrophysics Data System (ADS)

Due to the increase of urbanization and modification of agricultural practices, peri-urban areas experiment a quick change in land use. The impact of such change on the catchment hydrological cycle must be quantified. To achieve this goal, distributed hydrological models offer the ability to take into account land use change, and more specifically its effect on surface infiltration capacity. A distributed assessment of infiltration properties and their variability at the catchment scale is thus of great importance if accurate simulation of the water balance are expected on such catchments. This paper presents a field campaign conducted in a 7 km2 peri-urban catchment, located in the "Mont du Lyonnais" area, close to the city of Lyon (France) in order to document the topsoil hydraulic properties. The sampling strategy was set up in order to sample the largest number of soil/land use combinations. The locations were chosen from a GIS analysis based on the overlapping of the pedology and land use maps, and accessibility consideration. At each location, two types of infiltration tests were performed: infiltration tests under suction using mini-disk infiltrometers and single ring infiltration tests under positive head. Three replicates were performed for each method. Particle size data and organic matter analysis were also conducted at each location. Results will be discussed in terms of soil hydraulic properties and particle size data statistics. Relationship with external factors such as pedological unit, land use, slope, texture will be explored. Preliminary results show that forest and pasture soils exhibit the highest hydraulic conductivity and sorptivity. In order to provide models with values at the modelling unit scale (field and/or sub-catchment scale), existing pedotransfer function will be assessed and if necessary calibrated using the local measurements. Finally a methodology for the cartography of the soil hydraulic properties will be proposed.

Gonzalez-Sosa, E.; Braud, I.; Gonzalez-Sosa, E.; Dehotin, J.; Branger, F.; Lagouy, M.

2009-04-01

236

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

237

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…

Engelbrecht, Nancy; And Others

238

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

239

The role of estimation error in probability density function of soil hydraulic parameters: Pedotop scale  

NASA Astrophysics Data System (ADS)

For modeling of transport processes and for prognosis of their results, the knowledge of hydrodynamic parameters is required. Soil hydrodynamic parameters are determined in the field by methods based upon certain approximations and the procedure of inverse solution is applied. The estimate of a parameter P includes therefore an error e. Hydrodynamic parameters are variable to a different degree like other soil properties even over the region of one pedotaxon and the knowledge of their probability density function PDF is frequently required. We have used five approximate infiltration equations for the estimation of sorptivity S and saturated hydraulic conductivity K. Distribution of both parameters was determined with regard to the type of applied infiltration equation. PDF of parameters was not identical when we compared the parameter estimates derived by various infiltration equations. As it follows from this comparative study, the estimation error e deforms PDF of the parameter estimates.

Kutílek, Miroslav; Krejca, Miroslav; Kupcová-Vlašimská, Jana

240

Estimating the three-dimensional hydraulic structure of soils from ground-penetrating radar measurements  

Microsoft Academic Search

We investigate the application of ground-penetrating radar (GPR) as a proxy to estimate the three-dimensional hydraulic structure of soils at the field scale. The soil at a test site was first explored with GPR in great detail. Soil profiles were excavated to obtain ground truth information about the dielectric structure observed from the radargrams. Time series of radargrams are measured

U. WollschIager; Kurt Roth

2004-01-01

241

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...

242

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...

243

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...

244

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...

245

Evaluation of multimodal hydraulic functions in characterizing a heterogeneous field soil  

Microsoft Academic Search

Soil water retention curves are often used to estimate the hydraulic conductivity function. Unfortunately, single S-shaped functions cannot adequately describe water retention curves of structured soil, especially near saturation. The approach of superposition of two or more unimodal retention functions such as the van Genuchten model was used here to describe retention data of a macroporous soil. A total of

Dirk Mallants; Peng-H. Tseng; Nobuo Toride; Anthony Tinunerman; Jan Feyen

1997-01-01

246

Seasonal and spatial variability of surface hydraulic properties  

Microsoft Academic Search

Monitoring, using remote sensing, of seasonal changes of land surface properties such as: freezing and thawing of wetland, freezing and thawing of soil, as well as soil moisture and snow cover mapping, relies on capabilities to relate physical characteristics of the study area and satellite observations. The water and ice content of soil are very important parameters for determination of

Irene G. Rubinstein; Richard Fernandes; Bradley Corner

2002-01-01

247

LIMITING DRILLING SLURRY PRESSURES TO CONTROL HYDRAULIC FRACTURING DURING HDD THROUGH PURELY COHESIVE SOIL  

Microsoft Academic Search

Hydraulic fracturing is a problem associated with Horizontal Directional Drilling that is still inadequately understood and can result in serious consequences. During insertion of utility conduits and other buried pipe infrastructure, drilling slurry is used to stabilize the soil around the excavation zone prior to pulling the new pipeline into place. Hydraulic fracturing occurs when the drilling slurry flows through

Matthew J. Kennedy; Graeme D. Skinner; Ian D. Moore

248

The effect of microorganisms, salinity and turbidity on hydraulic conductivity of irrigation channel soil  

Microsoft Academic Search

The introduction of polysaccharide producing benthic algae and bacteria could provide a low cost technique for seepage control in irrigation channels. The ability of algae and bacteria to produce polysaccharides proved to be successful in reducing the hydraulic conductivity of irrigation channel soil. Hydraulic conductivity was reduced to less than 22% of its original value within a month of inoculating

S. R. Ragusa; D. S. Zoysa; P. Rengasamy

1994-01-01

249

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

250

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

251

Physical top soil properties in pure stands of Norway spruce ( Picea abies) and mixed species stands in Austria  

Microsoft Academic Search

This study was done to evaluate the impact of pure Norway spruce stands on physical soil properties of top soil in comparison to mixed species stands on comparable sites. It was hypothesized that the flat root system of spruce causes soil compaction, which would have a negative impact on the soil aeration and hydraulic properties and consequently on seedbed quality,

Torsten W Berger; Herbert Hager

2000-01-01

252

Parameter equivalence for the Gardner and van Genuchten soil hydraulic conductivity functions for steady vertical flow with inclusions  

Microsoft Academic Search

The analytic element method is well suited for the Gardner hydraulic conductivity function, but is limited in describing real soils. Therefore, parameter equivalence between the van Genuchten and Gardner hydraulic conductivity functions is explored for the case of steady vertical flow through a homogeneous medium with a single inclusion, i.e., a binary soil. The inclusion has different hydraulic parameters than

Dale F. Rucker; Arthur W. Warrick; Ty P. A. Ferreb

2005-01-01

253

Hydraulic and physical properties of stonewool substrates in horticulture  

Microsoft Academic Search

Hydraulic conductivity and water content dependence on the substrate suction are certainly among the most crucial physical parameters because they are responsible for water movement and retention in the substrate. Only few data are currently available in the literature and it is the reason why an experimental study was undertaken to characterize more precisely the properties of two slab types

S. Bougoul; S. Ruy; F. de Groot; T. Boulard

2005-01-01

254

Fractal approach to hydraulic properties in unsaturated porous media  

Microsoft Academic Search

Modelling flow and solute transport in unsaturated porous media on the basis of the Richards equation requires specifying values for unsaturated hydraulic conductivity and water potential as a function of saturation. The high cost and large spatial variability of measurements makes the prediction of these properties a viable alternative. Fractal approach seems to be a potentially useful tool to describe

Y. F. Xu; Ping Dong

2004-01-01

255

Constant Flow Method for Concurrently Measur- ing Soil-Water Characteristic Curve and Hydraulic Conductivity Function  

Microsoft Academic Search

A constant-flow laboratory testing method CFM is presented for concurrently measuring the soil-water characteristic curve SWCC and hydraulic conductivity function HCF of unsaturated coarse-grained soils. Two computer-automated syringe pumps are employed to control the volumetric water content of a specimen and to periodically impose constant volumetric flow rates through the specimen, respectively. Hydraulic conductivity k corresponding to each water content

Ning Lu; Alexandra Wayllace; Jiny Carrera; William J. Likos

256

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

257

Kriging analysis of soil properties  

Microsoft Academic Search

Background, aim, and scope  Soil as a landscape body contains wide ranges of physical, chemical, morphological, and mineralogical properties, both laterally\\u000a and vertically. Soils with similar properties and environments are expected to behave similarly. A statement on land use potential\\u000a will depend in part on the precision and accuracy of the statements that can be made about the soils. This information

Gilbert C. Sigua; Wayne H. Hudnall

2008-01-01

258

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.

259

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

2009-02-25

260

Hydraulic charcterization of carbonatic rock  

Microsoft Academic Search

The hydraulic conductivity, K(theta), and the water retention, theta(h), are needed to predict the flow of water and solute transport in unsaturated porous media. During recent decades methods have been developed to determine these hydraulic properties for rock. We have developed a methodology, based on Wind's evaporation method for soils, to measure in the laboratory the water retention and hydraulic

M. C. Caputo; A. Basile; R. de Mascellis; J. R. Nimmo; M. Vurro; N. Walsh

2003-01-01

261

Water utilization, plant hydraulic properties and xylem vulnerability in three contrasting coffee (Coffea arabica) cultivars.  

PubMed

Water use, hydraulic properties and xylem vulnerability to cavitation were studied in the coffee (Coffea arabica L.) cultivars San Ramon, Yellow Caturra and Typica growing in the field under similar environmental conditions. The cultivars differed in growth habit, crown morphology and total leaf surface area. Sap flow, stomatal conductance (g(s)), crown conductance (g(c)), apparent hydraulic conductance of the soil-leaf pathway (G(t)), leaf water potential (Psi(L)) and xylem vulnerability to loss of hydraulic conductivity were assessed under well-watered conditions and during a 21-day period when irrigation was withheld. Sap flow, g(c), and G(t) were greatest in Typica both with and without irrigation, lowest in San Ramon, which was relatively unresponsive to the withholding of irrigation, and intermediate in Yellow Caturra. The cultivars had similar g(s) when well watered, but withholding water decreased g(s) more in Typica and Yellow Caturra than in San Ramon. Typica had substantially lower Psi(L) near the end of the unirrigated period than the other cultivars (-2.5 versus -1.8 MPa), consistent with the relatively high sap flow in this cultivar. Xylem vulnerability curves indicated that Typica was less susceptible to loss of hydraulic conductivity than the other cultivars, consistent with the more negative Psi(L) values of Typica in the field during the period of low soil water availability. During soil drying, water use declined linearly with relative conductivity loss predicted from vulnerability curves. However, cultivar-specific relationships between water use and predicted conductivity loss were not observed because of pronounced hysteresis during recovery of water use following soil water recharge. All cultivars shared the same functional relationship between integrated daily sap flow and G(t), but they had different operating ranges. The three cultivars also shared common functional relationships between hydraulic architecture and water use despite consistent differences in water use under irrigated and dry soil conditions. We conclude that hydraulic architectural traits, rate of water use per plant and crown architecture are important determinants of short- and long-term variations in the water balance of Coffea arabica. PMID:12651468

Tausend, Peter C.; Goldstein, Guillermo; Meinzer, Frederick C.

2000-02-01

262

Testing Soil Encasing Materials for Measuring Hydraulic Conductivity of a Sandy-Loam Soil by the Cube Methods  

Microsoft Academic Search

The Cube Method (CM) and the Modifi ed Cube Method (MCM) were developed for measur- ing vertical (Kv) and horizontal (Kh) saturated hydraulic conductivity of a single soil sample. By these methods, a cube of soil is carved out in situ and a suitable material is applied to enclose the cube in a tightly fi tting casing before moving the

V. Bagarello; A. Sgroi

2008-01-01

263

Time-dependent hydraulic resistance of the soil crust: Henry's law  

Microsoft Academic Search

In earlier experiments on steady infiltration into crust-topped soil columns an additional resistance was observed in the vicinity of the boundary between the crust and the soil below it. I have performed laboratory tests in order to check the following hypothesis: high hydraulic resistance of the crust results in steep drop of the water pressure between the top and bottom

Miroslav Kutílek

2003-01-01

264

EFFECT OF SYNTHETIC LEACHATE ON THE HYDRAULIC CONDUCTIVITY OF CLAYEY SOIL IN URMIA CITY LANDFILL SITE  

Microsoft Academic Search

The effect of synthetic leachate on the hydraulic conductivity of a clayey soil in the Urmia city landfill site, Iran, was investigated using a triaxial permeability apparatus. The bladder accumulators were fabricated for flexible wall triaxial permeability apparatus to facilitate synthetic leachate permeation in the apparatus. The landfill soil was tested and classified as silty clayey sand (SM-SC) and did

K. BADV; A. OMIDI

265

Prediction of saturated hydraulic conductivity of compacted soils using empirical scaling factors  

Microsoft Academic Search

A new empirical-based scaling method is introduced to predict saturated hydraulic conductivity (Ks) of compacted soils. This method is an improvement of the former non-similar media concept (NSMC) model that is generalized for tilled and untilled conditions. In this method, geometric mean particle size diameter (dg), geometric standard deviation (?g) and saturated soil water content (total porosity) are successfully incorporated

Seyed Hamid Ahmadi; Ali Reza Sepaskhah

2011-01-01

266

HYDRAULIC REDISTRIBUTION OF SOIL WATER BY ROOTS IN FORESTS OF THE PACIFIC NORTHWEST  

EPA Science Inventory

One aspect of structural complexity of forest canopies is the root system structure belowground, which influences patterns of soil water utilization by trees. Deeply rooted trees and other plants can hydraulically lift water via their roots from several m below the soil surface ...

267

Hydraulic conductivity, residue cover and soil surface roughness under different tillage systems in semiarid conditions  

Microsoft Academic Search

The objective of this study was to investigate the effect of tillage and cropping system on near-saturated hydraulic conductivity, residue cover and surface roughness to improve soil management for moisture conservation under semiarid Mediterranean conditions. Three tillage systems were compared (subsoil tillage, minimum tillage and no-tillage) under three field situations (continuous crop, fallow and crop after fallow) on two soils

J. Lampurlanés; C. Cantero-Martínez

2006-01-01

268

Geoelectrical evaluation of soil properties  

NASA Astrophysics Data System (ADS)

Major efforts are directed lately worldwide in order to establish proper strategies for the preservation of soil quality, its protection and sustainable use. Therefore there is a great interest in finding new techniques able to offer information in real time on the soil properties (porosity, bulk density), compaction, salinity or moisture content. Aiming at getting information on soil properties and relate their spatial modifications to variations of electric resistivity, laboratory analyses have been performed on soil samples taken on several lines. The data obtained on the selected line are presented in the following, as variation ranges: density 2.4 - 2.6 g/cm3; porosity 51 - 79%; moisture content 8 - 20%; electric resistivity 45 - 110 ohm*m. The variations of such physical properties along the soil line showed correlation between resistivity highs and lows of moisture content and porosity. High values of resistivity correlate well with high densities on this particular type of soil, meaning in both cases sectors of low porosity and lack of water. In order to get information on the geoelectric measurements resolution on shallow layers of soil, a soil model have been built for the studied line, the depth between the surface and the depth of 0.63 m being divided in vertical sectors with resistivity contrasts. The electric resistivity values obtained on soil samples have been placed in the corresponding sectors, in order to reproduce the physical conditions on the surveyed line. Resistivity measurements on this line were simulated for different geoelectric techniques: Wenner, Schlumberger, Wenner-Schlumberger and Gradient-Dipole. The results obtained using these techniques consisted in variations of resistivity for the considered soil model. The interpretation of such geoelectric data led to soil models for each employed technique. By comparing these results to the starting soil resistivity model, the capability of these techniques for shallow soil layer investigations has been evaluated.

Chitea, F.; Ioane, D.; Kodom, K.

2009-04-01

269

Hydraulic and purification behaviors and their interactions during wastewater treatment in soil infiltration systems.  

PubMed

Four three-dimensional lysimeters were established in a pilot laboratory with the same medium sand and either an aggregate-laden (AL) or aggregate-free (AF) infiltration surface and a 60- or 90-cm soil vadose zone depth to ground water. During 48 weeks of operation, each lysimeter was dosed 4 times daily with septic tank effluent (STE) at 5 cm/d (AL) or 8.4 cm/d (AF). Weekly monitoring was done to characterize the STE, percolate flow and composition, and water content distributions within the lysimeters. Bromide tracer tests were completed at weeks 0, 8, and 45 and during the latter two times, ice nucleating active (INA) bacteria and MS-2 and PRD-1 bacteriophages were used as bacterial and viral surrogates. After 48 weeks, soil cores were collected and analyzed for chemical and microbial properties. The observations made during this study revealed a dynamic, interactive behavior for hydraulic and purification processes that were similar for all four lysimeters. Media utilization and bromide retention times increased during the first two months of operation with the median bromide breakthrough exceeding one day at start-up and increasing to two days or more. Purification processes were gradually established over four months or longer, after which there were high removal efficiencies (>90%) for organic constituents, microorganisms, and virus, but only limited removal of nutrients. Soil core analyses revealed high biogeochemical activity within the infiltrative zone from 0 to 15 cm depth. All four lysimeters exhibited comparable behavior and there were no significant differences in performance attributable to infiltrative surface character or soil depth. It is speculated that the comparable performance is due to a similar and sufficient degree of soil clogging genesis coupled with bioprocesses that effectively purified the wastewater effluent given the adequate retention times and high volumetric utilization's of the sand media. PMID:11235891

Van Cuyk, S; Siegrist, R; Logan, A; Masson, S; Fischer, E; Figueroa, L

2001-03-01

270

A comparative study of multiple approaches to soil hydraulic parameter scaling applied at the hillslope scale  

NASA Astrophysics Data System (ADS)

Soil hydraulic parameters were upscaled from a 30 m resolution to a 1 km resolution using four different aggregation schemes across the Little Washita watershed in Oklahoma. A topography-based aggregation scheme, a simple homogenization method, a Markov chain Monte Carlo (MCMC)-based stochastic technique, and a Bayesian neural network (BNN) approach to the upscaling problem were analyzed in this study. The equivalence of the upscaled parameters was tested by simulating water flow for the watershed pixels in HYDRUS-3-D, and comparing the resultant soil moisture states with data from the electronically scanned thin array radiometer (ESTAR) airborne sensor during the SGP97 hydrology experiment. The watershed was divided into pixels of 1 km resolution and the effective soil hydraulic parameters obtained for each pixel. The domains were then simulated using the physics-based HYDRUS-3-D platform. Simulated soil moisture states were compared across scales, and the coarse scale values compared against the ESTAR soil moisture data products during the SGP97 hydrology experiment period. Results show considerable correlations between simulated and observed soil moisture states across time, topographic variations, location, elevation, and land cover for techniques that incorporate topographic information in their routines. Results show that the inclusion of topography in the hydraulic parameter scaling algorithm accounts for much of the variability. The topography-based scaling algorithm, followed by the BNN technique, were able to capture much of the variation in soil hydraulic parameters required to generate equivalent soil moisture states in a coarsened domain. The homogenization and MCMC methods, which did not account for topographic variations, performed poorly in providing effective soil hydraulic parameters at the coarse scale.

Jana, Raghavendra B.; Mohanty, Binayak P.

2012-02-01

271

Hydraulic lift may buffer rhizosphere hyphae against the negative effects of severe soil drying in a California Oak savanna  

Microsoft Academic Search

Many studies have shown that the total abundance of hyphae in the soil covaries seasonally with soil moisture. We investigated the extent to which soil hyphal abundance varies as a function of depth and moisture availability within the soil profile during the dry season, and determined whether soil moisture compensation via hydraulic lift (HL) buffers rhizosphere fungi from the effects

J. I. Querejeta; L. M. Egerton-Warburton; M. F. Allen

2007-01-01

272

Description of hydraulic and strength properties of anisotropic geomaterials  

NASA Astrophysics Data System (ADS)

In this paper, a simple generalization of Darcy's law is proposed for the description of hydraulic properties of anisotropic porous materials. The coefficient of permeability is defined as a scalarvalued function of orientation. The principal directions of permeability are determined from a fabric descriptor specifying the distribution of average pore size. An example is provided for identification of material parameters, which is based on an idealized "pipe network model". A procedure for defining the anisotropy in strength properties, which incorporates a conceptually similar approach, is also reviewed and an illustrative example is provided.

Pietruszczak, S.; Pande, G. N.

2012-10-01

273

Decoupling the Influence of Leaf and Root Hydraulic Conductances on Stomatal Conductance and its Sensitivity to Vapor Pressure Deficit as Soil Dries in a Drained Loblolly Pine Plantation  

Microsoft Academic Search

The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on plant hydraulic properties and water balances are not well studied. Precipitation and soil moisture in North America will be modified in the future and forest trees in the US will be challenged by warmer temperature, higher leaf-to-air water vapor pressure deficit

J. Domec; A. Noormets; J. S. King; S. G. McNulty; G. Sun; M. J. Gavazzi; J. L. Boggs

2008-01-01

274

A topography-based scaling algorithm for soil hydraulic parameters at hillslope scales: Field testing  

NASA Astrophysics Data System (ADS)

Soil hydraulic parameters were upscaled from a 30 m resolution to a 1 km resolution using a new aggregation scheme (described in the companion paper) where the scale parameter was based on the topography. When soil hydraulic parameter aggregation or upscaling schemes ignore the effect of topography, their application becomes limited at hillslope scales and beyond, where topography plays a dominant role in soil deposition and formation. Hence the new upscaling algorithm was tested at the hillslope scale (1 km) across two locations: (1) the Little Washita watershed in Oklahoma, and (2) the Walnut Creek watershed in Iowa. The watersheds were divided into pixels of 1 km resolution and the effective soil hydraulic parameters obtained for each pixel. Each pixel/domain was then simulated using the physically based HYDRUS-3-D modeling platform. In order to account for the surface (runoff/on) and subsurface fluxes between pixels, an algorithm to route infiltration-excess runoff onto downstream pixels at daily time steps and to update the soil moisture states of the downstream pixels was applied. Simulated soil moisture states were compared across scales, and the coarse scale values compared against the airborne soil moisture data products obtained during the hydrology experiment field campaign periods (SGP97 and SMEX02) for selected pixels with different topographic complexities, soil distributions, and land cover. Results from these comparisons show good correlations between simulated and observed soil moisture states across time, topographic variations, location, elevation, and land cover. Stream discharge comparisons made at two gauging stations in the Little Washita watershed also provide reasonably good results as to the suitability of the upscaling algorithm used. Based only on the topography of the domain, the new upscaling algorithm was able to provide coarse resolution values for soil hydraulic parameters which effectively captured the variations in soil moisture across the watershed domains.

Jana, Raghavendra B.; Mohanty, Binayak P.

2012-02-01

275

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.

2011-01-03

276

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

277

Effect of subsoiling on soil physical properties and dry matter production on a Brown Soil in Southland, New Zealand  

Microsoft Academic Search

This study examined the effect of shallow subsoiling on soil physical properties and ryegrass?white clover pasture production on a Waikiwi silt loam (Brown Soil) over 2.5 years. Macroporosity, hydraulic conductivity, and air permeability were measured in 6?cm increments down to 30 cm soil depth. The topsoil was loosened by pulling both conventional tines or wing?shaped tines set at 50 cm

J. J. Drewry; R. J. Paton

2000-01-01

278

Simultaneous scaling of soil water retention and unsaturated hydraulic conductivity functions assuming lognormal pore-size distribution  

Microsoft Academic Search

Using simultaneous scaling, soil spatial variability of hydraulic functions can be described from a single set of scaling factors. The conventional scaling approach is based on empirical curve fitting, without paying much attention to the physical significance of the scaling factors. In this study, the concept of simultaneous scaling of the soil water retention and unsaturated hydraulic conductivity functions is

A. Tuli; K. Kosugi; J. W. Hopmans

2001-01-01

279

Field methods for measuring hydraulic properties of peat deposits  

NASA Astrophysics Data System (ADS)

New field techniques were developed and tested to evaluate peat storativity and hydraulic conductivity in a Boreal fen. Enclosed drainage tests and pumping tests were successfully completed in the thawed peat above an impermeable frozen layer and then repeated when the peat was fully thawed. A loading test experiment constrained values of vertical hydraulic conductivity within an order of magnitude for the peat below a depth of 2 m. An inherent advantage of these tests is that volumes of undisturbed peat on the scale of cubic metres may be characterized. Storativity of the fen peat as determined by enclosed drainage tests ranged from about 1.0 at the peat surface to 0.35 at a water table depth of 0.15 m. Laboratory drainage tests of peat cores gave similar, but widely scattered results. Hydraulic conductivity near the surface was as high as 9.0 × 10-3 ms-1 determined with pumping tests and in the range of 10-6 to 10-5 ms-1 below a depth of 2 m, estimated with the loading test. Slug tests gave similar results. Pumping tests, enclosed storativity tests and loading tests are practical large-scale field tests for determining peat properties. Copyright

Hogan, J. M.; van der Kamp, G.; Barbour, S. L.; Schmidt, R.

2006-11-01

280

Spatial Bias in Field-Estimated Unsaturated Hydraulic Properties  

SciTech Connect

Hydraulic property measurements often rely on non-linear inversion models whose errors vary between samples. In non-linear physical measurement systems, bias can be directly quantified and removed using calibration standards. In hydrologic systems, field calibration is often infeasible and bias must be quantified indirectly. We use a Monte Carlo error analysis to indirectly quantify spatial bias in the saturated hydraulic conductivity, K{sub s}, and the exponential relative permeability parameter, {alpha}, estimated using a tension infiltrometer. Two types of observation error are considered, along with one inversion-model error resulting from poor contact between the instrument and the medium. Estimates of spatial statistics, including the mean, variance, and variogram-model parameters, show significant bias across a parameter space representative of poorly- to well-sorted silty sand to very coarse sand. When only observation errors are present, spatial statistics for both parameters are best estimated in materials with high hydraulic conductivity, like very coarse sand. When simple contact errors are included, the nature of the bias changes dramatically. Spatial statistics are poorly estimated, even in highly conductive materials. Conditions that permit accurate estimation of the statistics for one of the parameters prevent accurate estimation for the other; accurate regions for the two parameters do not overlap in parameter space. False cross-correlation between estimated parameters is created because estimates of K{sub s} also depend on estimates of {alpha} and both parameters are estimated from the same data.

HOLT,ROBERT M.; WILSON,JOHN L.; GLASS JR.,ROBERT J.

2000-12-21

281

Hydraulic Properties of Unsaturated Porous Media From Percolation Theory  

NASA Astrophysics Data System (ADS)

Percolation theory can be used to calculate transport properties in disordered media, such as solute diffusion and the hydraulic conductivity. Experiments have shown that diffusion of solutes in porous media vanishes linearly as threshold moisture content is approached. An empirical relationship gives the threshold moisture content as approximately the square root of the surface area to volume ratio of the medium. The first relationship demonstrates the relevance of percolation theory in its continuum application (non-zero transport in a given phase requires phase continuity), while the second can be shown to be based on the validity of a fractal description of the medium. Percolation-type scaling behavior of the unsaturated hydraulic conductivity is not observed; in fact critical path analysis from percolation theory using the threshold moisture content for the critical moisture content for percolation gives the hydraulic conductivity in agreement with experiment. However, cross-over from the validity of critical path analysis to the percolation scaling regime is accompanied by a rapid change in the slope of the conductivity, leading to rapid increases in experimental equilibration times, failure to observe equilibrium pressure-saturation relations, and excess water in the medium for a given tension. These effects confound interpretation of experiments, but unification within a percolation perspective allows quantitative predictions of both the equilibrium and non-equilibrium behavior.

Hunt, A. G.

2004-05-01

282

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

283

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

284

Properties and variability of soil and trench fill at an arid waste-burial site  

Microsoft Academic Search

During fall construction of two test trenches next to the waste facility on the Amargosa Desert near Beatty, NV, samples were collected to: (i) characterize physical and hydraulic properties of native soil (upper 5 m) and trench fill, (ii) determine effects of trench construction on selected properties and vertical variability of these properties, and (iii) develop conceptual models of vertical

B. J. Andraski

1996-01-01

285

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

286

A model for hydraulic redistribution incorporating coupled soil-root moisture transport  

NASA Astrophysics Data System (ADS)

One of the adaptive strategies of vegetation, particularly in water limited ecosystems, is the development of deep roots and the use of hydraulic redistribution which enables them to make optimal use of resources available throughout the soil column. Hydraulic redistribution refers to roots acting as a preferential pathway for the movement of water from wet to dry soil layers driven by the moisture gradient - be it from the shallow to deep layers or vice versa. This occurs during the nighttime while during the daytime moisture movement is driven to fulfill the transpiration demand at the canopy. In this study, we develop a model to investigate the effect of hydraulic redistribution by deep roots on the terrestrial climatology. Sierra Nevada eco-region is chosen as the study site which has wet winters and dry summers. Hydraulic redistribution enables the movement of moisture from the upper soil layers to deeper zones during the wet months and this moisture is then available to meet the transpiration demand during the late dry season. It results in significant alteration of the profiles of soil moisture and water uptake as well as increase in the canopy transpiration, carbon assimilation, and the associated water-use-efficiency during the dry summer season. This also makes the presence of roots in deeper soil layers much more important than their proportional abundance would otherwise dictate. Comparison with observations of latent heat from a flux tower demonstrates improved predictability and provides validation of the model results. Hydraulic redistribution serves as a mechanism for the interaction between the variability of deep layer soil-moisture and the land-surface climatology and could have significant implications for seasonal and sub-seasonal climate prediction.

Amenu, G. G.; Kumar, P.

2007-10-01

287

A model for hydraulic redistribution incorporating coupled soil-root moisture transport  

NASA Astrophysics Data System (ADS)

One of the adaptive strategies of vegetation, particularly in water limited ecosystems, is the development of deep roots and the use of hydraulic redistribution which enables them to make optimal use of resources available throughout the soil column. Hydraulic redistribution refers to roots acting as a preferential pathway for the movement of water from wet to dry soil layers driven by the moisture gradient - be it from the shallow to deep layers or vice versa. This occurs during the nighttime while during the daytime moisture movement is driven to fulfill the transpiration demand at the canopy. In this study, we develop a model to investigate the effect of hydraulic redistribution by deep roots on the terrestrial climatology. Sierra Nevada eco-region is chosen as the study site which has wet winters and dry summers. Hydraulic redistribution enables the movement of moisture from the upper soil layers to deeper zones during the wet months and this moisture is then available to meet the transpiration demand during the late dry season. It results in significant alteration of the profiles of soil moisture and water uptake as well as increase in the canopy transpiration, carbon assimilation, and the associated water-use-efficiency during the dry summer season. This also makes the presence of roots in deeper soil layers much more important than their proportional abundance would otherwise dictate. Comparison with observations of latent heat from a flux tower demonstrates improved predictability and provides validation of the model results. Hydraulic redistribution serves as a mechanism for the interaction between the variability of deep layer soil-moisture and the land-surface climatology and could have significant implications for seasonal and sub-seasonal climate prediction.

Amenu, G. G.; Kumar, P.

2008-01-01

288

Hydraulic lift: soil processes and transpiration in the Mediterranean leguminous shrub Retama sphaerocarpa (L.) Boiss  

Microsoft Academic Search

Hydraulic lift (HL) is the process by which plants can passively transfer water from deep, moist soil layers to shallow, dry\\u000a soil layers. Although it has attracted recent research interest, a mechanistic understanding and its implications for ecosystem\\u000a functioning are still lacking. Here we describe HL seasonal patterns in a semi-arid shrub species and its influence on plant\\u000a water dynamics.

Iván Prieto; Zaal Kikvidze; Francisco I. Pugnaire

2010-01-01

289

Hydraulic Conductivity, Immobile Water Content, and Exchange Coefficient in Three Soil Profiles  

Microsoft Academic Search

We used tension disk infiltrometers to determine the hydraulic con- ductivity at the matric potential of 20.1 kPa (K20.1), the immobile water fraction (uim\\/u), and the mass exchange coefficient (a) in three soil profiles of an agricultural field cropped with winter wheat (Triticum aestivum L.). A significant effect of soil horizonation was found for K20.1, uim\\/u, and a and could

L. Alletto; Y. Coquet; P. Vachier; C. Labat

2006-01-01

290

Application of In-situ Lysimetric Studies for Determining Soil Hydraulic Conductivity  

Microsoft Academic Search

Several techniques such as laboratory column studies, under normal and accelerated gravity environments, numerical modeling\\u000a and pedo-transfer functions have been employed by previous researchers to determine hydraulic conductivity of soils. However,\\u000a these methods suffer with several limitations, particularly, as far as regeneration of in-situ soil conditions and boundary\\u000a conditions, in an exceptionally small model, are concerned. Under these circumstances, in-situ

B. Hanumantha Rao; V. Sridhar; R. R. Rakesh; D. N. Singh; P. K. Narayan; P. K. Wattal

2009-01-01

291

Field-Measured Infiltration Properties of Mojave Desert Soils  

NASA Astrophysics Data System (ADS)

Characteristics typical of alluvial desert soils, such as depositional stratification, desert pavement, biotic crusts, and vesicular horizons strongly influence soil moisture and its variability. Knowledge of infiltration capacity, water retention, and unsaturated hydraulic conductivity is central to the assessment of water availability to plants and animals after infiltration events. These hydraulic parameters are directly related to the degree of soil development. The frequency and magnitude of storm events in conjunction with degree of soil development also affect runoff and erosion. Our purpose is to examine field soil-water behavior and determine unsaturated hydraulic properties needed for large-scale modeling of soil moisture. The results of this study will be used in conjunction with surficial geologic mapping of the Mojave Desert in evaluations of ecological habitat quality. We conducted infiltration/redistribution experiments on three different-aged deposits in the Mojave National Preserve: (1) recently deposited wash sediments, (2) a soil of early Holocene age, and (3) a highly developed soil of late Pleistocene age. In each experiment we ponded water in a 1-m-diameter infiltration ring for 2.3 hr. For several weeks we monitored water content and matric pressure to depths of 1.5 m, and distances of 6 m from the infiltration ring. Measuring techniques included surface electrical resistance tomography, dielectric-constant probes, heat-dissipation probes, and tensiometers. Analysis of the subsurface measurements using an instantaneous-profile technique gives the retention and K properties that will be used in predictive modeling. In each experiment the infiltration rate was nearly constant in time, with infiltration capacity 4 times greater in the youngest than in the oldest soil. Average infiltration flux densities within the ring during the period of ponding were 0.80 m/hr in the active wash, 0.45 m/hr in the Holocene soil, and 0.21 m/hr in the Pleistocene soil. All three deposits have significant gravel (30-70% within the uppermost 1.5 m) with the percentage of silt and clay increasing with deposit age. The low infiltration capacity in the oldest soil is consistent with the presence of the more highly developed vesicular horizon and accumulation of illuvial silt. Depositional stratification in the active wash did not impede downward flow to the same degree as in the early Holocene-age soil, which has some soil horizon development and sparse biotic crust. Infiltrated water spread laterally to at least 1 m beyond the ring perimeter at all sites; the presence of a buried clay-rich horizon in the active wash enhanced spreading at depth to 2 m.

Perkins, K. S.; Nimmo, J. R.; Winfield, K. A.; Schmidt, K. M.; Miller, D. M.; Stock, J. D.; Singha, K.

2005-12-01

292

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

293

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

294

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 ...

295

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...

296

Testing the concentric-disk tension infiltrometer for field measurement of soil hydraulic conductivity  

Microsoft Academic Search

The concentric-disk tension infiltrometer (CDTI) may be used to simultaneously measure the confined (Kc) and the unconfined (Ku) soil hydraulic conductivity, but it has received little testing. Comparison between Kc and Ku can be affected by the calculation approach applied to analyze unconfined steady-state infiltration rates. The objectives of this investigation were to: i) establish the effect of the calculation

V. Bagarello; M. Castellini; M. Iovino; A. Sgroi

2010-01-01

297

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 ...

298

Capillary bundle model of hydraulic conductivity for frozen soil  

Microsoft Academic Search

We developed a capillary bundle model to describe water flow in frozen soil. We assume that the soil can be represented as a bundle of cylindrical capillaries. We consider that the freezing point in the capillaries is depressed according to the Gibbs-Thomson effect and that when stable ice forms in a capillary, the ice forms in the center of the

Kunio Watanabe; Markus Flury

2008-01-01

299

Parameter estimation for determining hydraulic properties of a fine sand from transient flow measurements  

Microsoft Academic Search

A cone penetrometer method for measuring hydraulic conductivity of unsaturated soils at depth is under development. Successful advancement of this method hinges on using parameter estimation to obtain hydraulic parameter values from pore water pressure and flow rate data. A finite element model is employed to predict flow responses, and objective functions describe differences between ``true'' and simulated responses. Contour

Molly M. Gribb

1996-01-01

300

Comparison of Aquifer Recharge Estimates Based on Measured and Estimated Hydraulic Properties  

Microsoft Academic Search

Because unsaturated hydraulic properties, which are used to estimate recharge, are difficult and time consuming to measure accurately, models that estimate these properties indirectly are often used. Using data from six locations in southern New Jersey that appear to have steady-state flow conditions, five hydraulic property prediction and parameterization techniques were evaluated for recharge estimation. The unsaturated zone at this

K. S. Perkins

2003-01-01

301

Polymer/bentonite/soil admixtures as hydraulic barriers  

SciTech Connect

Preventing waste fluids retained in on-site earthen pits from leaching into the surrounding environment has become a growing concern in the oil and gas industry. One possible solution is to incorporate a pit liner that acts as an impervious barrier between the contained fluids and adjacent soil or groundwater outside the pit. Such materials as flexible membranes, recompacted native soils, and polymeric/soil admixtures are commercially available for pit-lining applications. This paper briefly discusses the relative merits of each type of liner for oilfield waste. Among these liner materials, polymer/bentonite/soil admixtures, which consist of a blend of high-molecular-weight linear and crosslinked polymers, have many advantages, including self-sealing capability, inertness to degradation, and easy installation at low cost. The objective of the study was to compare the permeability and the susceptibility to chemical degradation of a variety of modified clay liners designed for oilfield waste pits.

Liao, W.A.

1989-06-01

302

Construction of Flexible Subterranean Hydraulic Barriers in Soil and Rock  

SciTech Connect

In the management of radioactive waste sites, there is sometimes a need to divert infiltration water; or contain or divert contaminated groundwater. This paper discusses several experimental techniques based on super permeating molten wax. Many of the methods are suited to form both vertical or horizontal barriers in-situ in the ground. The first method is based on thermally controlled permeation grouting between drilled holes that produces a very thick barrier in soil, rock, or even fractured rock up to 600 meters deep. The second method is a variation on jet grouting for producing a thin low cost barrier in soil. Also discussed is a technique for forming an infiltration barrier within the surface soil over an underground tank farm and a method for encapsulating a buried waste without excavation. These new methods can produce durable subterranean barriers of high integrity. These barriers are made with a special malleable wax that soaks into the soil or rock matrix. The wax is far more impermeable than clay or cement and can flex and stretch in response to soil movements. The wax contains no water and is not prone to damage from soil moisture changes. (authors)

Carter, E.E.; Carter, P.E. [Technologies Co, Sugar Land, Texas (United States); Cooper, D.C. [Ph.D. Idaho National Laboratory, Idaho Falls, ID (United States)

2008-07-01

303

Hydrogen peroxide effects on root hydraulic properties and plasma membrane aquaporin regulation in Phaseolus vulgaris.  

PubMed

In the last few years, the role of reactive oxygen species as signaling molecules has emerged, and not only as damage-related roles. Here, we analyzed how root hydraulic properties were modified by different hydrogen peroxide (H2O2) concentrations applied exogenously to the root medium. Two different experimental setups were employed: Phaseolus vulgaris plants growing in hydroponic or in potted soils. In both experimental setups, we found an increase of root hydraulic conductance (L) in response to H2O2 application for the first time. Twenty millimolar was the threshold concentration of H2O2 for observing an effect on L in the soil experiment, while in the hydroponic experiment, a positive effect on L was observed at 0.25 mM H2O2. In the hydroponic experiment, a correlation between increased L and plasma membrane aquaporin amount and their root localization was observed. These findings provide new insights to study how several environmental factors modify L. PMID:19437122

Benabdellah, Karim; Ruiz-Lozano, Juan Manuel; Aroca, Ricardo

2009-05-13

304

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

305

Relating sulfate adsorption to soil properties in Michigan forest soils  

Microsoft Academic Search

Six Michigan forest soil series comprising several gradients in soil physical and chemical properties were studied to relate SOâ adsorption to soil properties. The series studied were Grayling (mixed, frigid Typic udipsamments), Rubicon (sandy, mixed, frigid Entic Haplorthods), Kalkaska (sandy, mixed, frigid Typic Haplorthods), Montcalm (coarse-loamy, mixed Eutric Glossoboralfs), Spinks (sandy, mixed, mesic Psammentic Hapludalfs), and Oshtemo (coarse-loamy, mixed, mesic

N. W. MacDonald; J. B. Jr. Hart

2009-01-01

306

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

307

MEASURING SOIL HYDROLOGIC PROPERTIES USING DIELECTRIC SENSORS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of soil hydrologic properties is essential to many aspects of environmental research. Soil hydrologic properties determined from laboratory analyses often are non-representative of field conditions. In this work, we compare soil hydrologic properties determined in the field with values obt...

308

Evaluation of the physical properties of water treatment residue for use as a soil substitute compared with decomposed granite soil  

Microsoft Academic Search

To evaluate water treatment residue (WTR) as a soil substitute material, its physical properties were investigated and compared with decomposed granite soil (DGS). For comparison purposes, relative gas diffusivity (D\\/D0), saturated hydraulic conductivity (Ks), water retention curve, porosity and readily available water were measured for both the WTR and the DGS. The measured D\\/D0, Ks, water retention ability and porosity

Seok-Gon Park; Mizue Ohashi; Kiyoshi Kurosawa; Young-Jin Kim; Hisashi Yahata

2010-01-01

309

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...

310

Determination of the pore size distribution and hydraulic properties from Nuclear Magnetic Resonance relaxometry  

NASA Astrophysics Data System (ADS)

Known pore size distributions can be directly linked to the water retention characteristic which is essential for the prognosis of water and solute movement through the material. In our study, we evaluated the feasibility to use Nuclear Magnetic Resonance (NMR) relaxometry measurements for the characterization of pore size distribution in four porous samples with different texture and composition. Therefore, NMR T2 and T1 relaxation measurements at 6.47 MHz were carried out for three model samples (medium sand; fine sand; and a homogenous sand / kaolin clay mixture) and a natural soil. To quantify the goodness of the approach, the NMR measurements were compared in terms of cumulated pore size distribution functions and mean pore diameter with the two classical techniques based on water retention and mercury porosimetry measurements. The results showed that T1 and T2 derived mean pore size diameters are in good agreement with each other but deviate from retention curve derived ones. This is especially the case for well sorted sands with n values > 2.7. For finer materials differences are less pronounced. A short study was performed to evaluate the influence of the variations observed in the pore diameter distributions on the hydraulic properties of the samples: ?S, ?, and n. In conclusion, NMR T1 and T2 relaxation measurements can be used to estimate pore size distribution, mean pore diameter, as well as the retention function and corresponding hydraulic properties.

Stingaciu, Laura R.; Weihermüller, Lutz; Haber-Pohlmeier, Sabina; Stapf, Siegfried; Vereecken, Harry; Pohlmeier, Andreas

2010-05-01

311

Physical properties of Amazonian soils: A modeling study using the Anglo-Brazilian Amazonian Climate Observation Study data  

NASA Astrophysics Data System (ADS)

The hydraulic properties of some Amazonian soils differ significantly from the properties of the temperate soils. Most of the soil water release functions implemented in the atmospheric models used in deforestation studies were developed for temperate soils. It is necessary to check the validity of these soil water models with in situ data. In this study, the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) soil data have been used to modify the parameter values of Clapp and Hornberger's water release model. Different relations between hydraulic parameters and texture are proposed. These relations are included in the ISBA land surface scheme which is used to simulate the longterm evolution of the soil water content and the surface energy balance of three contrasting ABRACOS sites: two pasture sites with distinct soil properties and a forest site. The sensitivity of the simulations to the use of either the original Clapp and Hornberger water release model or the ABRACOS-derived one is shown.

Delire, C.; Calvet, J.-C.; Noilhan, J.; Wright, I.; Manzi, A.; Nobre, C.

1997-12-01

312

Aggregation of vertical flow in the vadose zone with auto- and cross-correlated hydraulic properties  

NASA Astrophysics Data System (ADS)

Quantifying water flow across larger areas of the vadose zone has applications in water resources management and climate modeling. The nonlinearity of unsaturated flow and the variability of vadose zone parameters make it difficult, if not impossible, to accurately simulate near-surface water content and flux with large-scale models. Monte Carlo simulations of one-dimensional infiltration and evaporation were conducted with the Richards equation to simulate moisture content and flux in a heterogeneous field according to the streamtube concept. A set of 126 retention curves and saturated hydraulic conductivities from the UNSODA database was used to generate random fields of hydraulic parameters with pre-defined auto- and cross-correlation. Two stochastic parameters were used: the retention shape factor, ln mn, and either the retention scale parameter ?s or ln hG or the saturated hydraulic conductivity, ln Ks. Infiltration is mostly governed by ln Ks. The evaporative flux is strongly determined by the “structural” parameter ln hG and also by the “textural” parameter ln mn. The water content in the upper part of the soil depends mostly on ln mn and somewhat on ?s. Cross-correlations all resulted in clusters with consistently low or high water contents and moisture fluxes. Aggregation to obtain results at larger scales was done by a posteriori averaging of local results. This procedure is a convenient benchmark for large-scale modeling approaches. In an example of a priori aggregation, effective retention parameters were optimized to synthetic retention curves for the larger pixel scale and subsequently used in the Richards equation. The amount of infiltrated water was overestimated by up to 40%, large parts of the upper profile were erroneously predicted to be saturated. Although effective hydraulic properties have been used successfully in evaporation studies, considerable errors, which increased with pixel size, also occurred for evaporation. The stream tube modeling offers a convenient and accurate, albeit mundane, approach to elucidate the role of hydraulic properties and to obtain large-scale hydrological data.

Leij, Feike J.; Sciortino, Antonella; Haverkamp, Randel; Soria Ugalde, José M.

2007-05-01

313

Uncertainty Assessment of Soil Hydraulic Parameter Estimated From Cokriging and Artificial Neural Network  

NASA Astrophysics Data System (ADS)

To characterize heterogeneity of soil hydraulic parameters, we developed a method to incorporate measurements of soil texture, bulk density, soil hydraulic parameter, and moisture content. The method first uses cokriging to estimate heterogeneous soil texture and bulk density (pedotransfer variables) using the moisture content as secondary variables that are abundant at the site. The heterogeneous pedotransfer variables are then used as input to an artificial neural network (ANN) developed to estimate heterogeneous soil hydraulic parameters, which are then used to simulate a field injection experiment at the U.S. Department of Energy's Hanford Site, WA. Although a large amount of uncertainty exists in the cokriging and ANN estimates, only the mean estimates are used for the numerical simulation. It is unknown to what extent the estimation uncertainty of cokriging and ANN affects the simulated injection experiment, and hence the motivation for this study. The uncertainty of parameter estimates is investigated in two steps. First, uncertainty of the ANN estimates is quantified using mean and variance of the estimates obtained from a bootstrap method. A total of 10,000 bootstraps are generated to obtain a statistically meaningful variance. The bootstrap estimates are Gaussian. A Latin Hypercube Sampling (LHS) method is used to generate 10 realizations from the entire distribution. A Monte Carlo simulation is conducted to evaluate propagation of uncertainty of the ANN estimates via numerical simulation of the field injection experiment. In the second step, uncertainty of cokriging estimates is assessed in a similar manner. Based on cokriging mean and variance and the assumed Gaussian distribution of cokriging estimates, 10 realizations of the pedotransfer variables are generated using the LHS method. For each of the realization, 10 realizations of soil hydraulic parameters are generated by the ANN. As a result, a total 100 realizations of the soil hydraulic parameters are generated for a Monte Carlo simulation. Uncertainty of the simulated injection experiment is evaluated next. Results indicate that the uncertainty of the cokriging estimates affects the injection experiment simulations considerably more than uncertainty of the ANN estimates.

Deng, H.; Ye, M.; Schaap, M. G.; Khaleel, R.

2007-12-01

314

The relationship between hydrodynamic properties and weathering of soils derived from volcanic rocks, Galapagos Islands (Ecuador)  

NASA Astrophysics Data System (ADS)

The aim of this interdisciplinary study is to examine a component of the hydrological cycle in Galapagos by characterizing soil properties. Nine soil profiles were sampled on two islands. Their physical and hydrodynamic properties were analyzed, along with their mineralogical composition. Two groups of soils were identified, with major differences between them. The first group consists of soils located in the highlands (>350 m a.s.l.), characterized by low hydraulic conductivity (<10-5 m s-1) and low porosity (<25%). These soils are thick (several meters) and homogeneous without coarse components. Their clay fraction is considerable and dominated by gibbsite. The second group includes soils located in the low parts of the islands (<300 m a.s.l.). These soils are characterized by high hydraulic conductivity (>10-3 m s-1) and high porosity (>35%). The structure of these soils is heterogeneous and includes coarse materials. The physical properties of the soils are in good agreement with the variations of the rainfall according to the elevation, which appears as the main factor controlling the soil development. The clayey alteration products constrain soils physical and hydrodynamic properties by reducing the porosity and consequently the permeability and also by increasing water retention.

Adelinet, M.; Fortin, J.; D'Ozouville, N.; Violette, S.

2008-11-01

315

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...

316

Soil hydraulic properties and their effect on surface and subsurface water transfer in a tropical rainforest catchment \\/ Propriétés hydrauliques du sol et leur effet sur les transferts d'eau de surface ou hypodermique dans un bassin de forêt en zone tropicale humide  

Microsoft Academic Search

This paper examines spatial and temporal heterogeneity of the surface, subsurface and vertical drainage components within and between three sites in a 25.7 ha tropical rainforest catchment. Our analysis indicates that saturation overland flow depends on the relationships between temporal variations in rainfall intensity, the upper soil store capacity, and the spatial variation of saturated hydraulic conductivity in the subsoil

M. BONELL; D. A. GILMOUR; D. F. SINCLAIR

1981-01-01

317

Analysis of flow behavior in a landfill with cover soil of low hydraulic conductivity  

Microsoft Academic Search

This paper presents the results of field tests of hydrologic parameters in a landfill and the results of numerical simulation\\u000a to find the efficiency of the pumping method to reduce leachate levels in the landfill. The field hydraulic conductivity and\\u000a storativity of waste and buried cover soils in the landfill are measured by pumping and slug tests. The hydrologic condition

Y.-S. Jang

2000-01-01

318

Post-fire Changes in Air Permeability and Hydraulic Conductivity of Soils Following 2003 Aspen Fire in Sabino Canyon, AZ  

NASA Astrophysics Data System (ADS)

As part of a project to study the hydrologic effects of fire on the Sabino Canyon Watershed, the Soil Corer Air Permeameter (SCAP) was developed to rapidly measure in-situ air permeability (k_a) of unburned and burned desert soils while providing a standard soil sample for additional laboratory analysis. Twenty-two unburned and burned plots were selected in woodland-chaparral and coniferous zones with low and high slopes, and low, medium, and high fuel loads or burn severities. Air permeability was measured on a 25-point square grid on each 100 m2 plot (n=445). Hydraulic conductivity (Ksat), water permeability (k_w), soil physical properties, and hydrophobicity measurements were made on extracted soil samples in the laboratory. There was a slight decrease in the median k_a from 95 to 80 ?m2 for the woodland- chaparral zone as a result of the wildfire. There was a greater decrease for the coniferous zone where the median decreased from 152 to 110 ?m2 following the fire. The k_w of woodland-chaparral soils increased from 192 to 425 ?m2; but the median k_w decreased for the coniferous zone from 862 to 444 ?m2 after the fire. In addition, hydrophobic measurements show that there was a significant increase in hydrophobicity for post-fire woodland-chaparral soils but not for coniferous soils. The log k_a and log Ksat measurements were highly correlated for the unburned woodland-chaparral soils, but this correlation decreased for burned woodland-chaparral soils. The unburned coniferous data set had the least k_a and Ksat correlation, but was reasonable for burned coniferous soils. The decrease in correlation may be due to increases of hydrophobicity, uneven wetting and preferential flow in Ksat measurements, or extremely rocky terrain. However, the overall, log k_a-log Ksat correlation for all unburned and burned soils including previous measurements on agricultural and alluvial soils follow the trend of the Iversen et al. (2001) log k_a-log Ksat correlation.

Chief, K.; Ferre, T. P.; Nijssen, B.

2006-12-01

319

Hydraulic Conductance and Mercury-Sensitive Water Transport for Roots of Opuntia acanthocarpa in Relation to Soil Drying and Rewetting  

Microsoft Academic Search

Drought-induced changes in root hydraulic conductance (LP) and mercury-sensitive water transport were examined for distal (immature) and mid-root (mature) regions of Opuntia acanthocarpa. During 45 d of soil drying, LP decreased by about 67% for distal and mid-root regions. Afte r8di nrewetted soil, LP recovered to 60% of its initial value for both regions. Axial xylem hydraulic conductivity was only

Pierre Martre; Gretchen B. North; Park S. Nobel

2001-01-01

320

Comparison of empirical, semi-empirical and physically based models of soil hydraulic functions derived for bi-modal soils.  

PubMed

The accelerated flow in soil pores is responsible for a rapid transport of pollutants from the soil surface to deeper layers up to groundwater. The term preferential flow is used for this type of transport. Our study was aimed at the preferential flow realized in the structural porous domain in bi-modal soils. We compared equations describing the soil water retention function h(theta) and unsaturated hydraulic conductivity K(h), eventually K(theta) modified for bi-modal soils, where theta is the soil water content and h is the pressure head. The analytical description of a curve passing experimental data sets of the soil hydraulic function is typical for the empirical equation characterized by fitting parameters only. If the measured data are described by the equation derived by the physical model without using fitting parameters, we speak about a physically based model. There exist several transitional subtypes between empirical and physically based models. They are denoted as semi-empirical, or semi-physical. We tested 3 models of soil water retention function and 3 models of unsaturated conductivity using experimental data sets of sand, silt, silt loam and loam. All used soils are typical by their bi-modality of the soil porous system. The model efficiency was estimated by RMSE (Root mean square error) and by RSE (Relative square error). The semi-empirical equation of the soil water retention function had the lowest values of RMSE and RSE and was qualified as "optimal" for the formal description of the shape of the water retention function. With this equation, the fit of the modelled data to experiments was the closest one. The fitting parameters smoothed the difference between the model and the physical reality of the soil porous media. The physical equation based upon the model of the pore size distribution did not allow exact fitting of the modelled data to the experimental data due to the rigidity and simplicity of the physical model when compared to the real soil porous system. On the other hand, the "optimal" unsaturated conductivity equation was obtained for a model based on the pore size distribution where the additional fitting parameters allowed a good agreement between the model and the reality of the measured data. We denoted this equation as semi-physical. PMID:19022525

Kutílek, M; Jendele, L; Krejca, M

2008-11-05

321

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

322

Nitrate Control of Root Hydraulic Properties in Plants: Translating Local Information to Whole Plant Response1[OA  

PubMed Central

The sessile lifestyle of plants constrains their ability to acquire mobile nutrients such as nitrate. Whereas proliferation of roots might help in the longer term, nitrate-rich patches can shift rapidly with mass flow of water in the soil. A mechanism that allows roots to follow and capture this source of mobile nitrogen would be highly desirable. Here, we report that variation in nitrate concentration around roots induces an immediate alteration of root hydraulic properties such that water is preferentially absorbed from the nitrate-rich patch. Further, we show that this coupling between nitrate availability and water acquisition results from changes in cell membrane hydraulic properties and is directly related to intracellular nitrate concentrations. Split-root experiments in which nitrate was applied to a portion of the root system showed that the response is both localized and reversible, resulting in rapid changes in water uptake to the portions of the roots exposed to the nitrate-rich patch. At the same time, water uptake by roots not supplied with nitrate was reduced. We believe that the increase in root hydraulic conductance in one part causes a decline of water uptake in the other part due to a collapse in the water potential gradient driving uptake. The translation of local information, in this case nitrate concentration, into a hydraulic signal that can be transmitted rapidly throughout the plant and thus coordinate responses at the whole plant level, represents an unexpected, higher level physiological interaction that precedes the level of gene expression.

Gorska, Anna; Ye, Qing; Holbrook, N. Michele; Zwieniecki, Maciej A.

2008-01-01

323

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

324

Geotechnical Properties of Soil-Ball Milled Soil Mixtures  

NASA Astrophysics Data System (ADS)

Laboratory experiments were conducted to study the fundamental geotechnical properties of mixtures of natural soils and its product after ball milling operation. The product after ball milling process is termed nano-soil herein. SEM analysis showed that much more nano size particles were obtained after the milling process. Testing and comparison of the properties of original kaolinite, montmorillonite and UKM soil with regard to its liquid limit, plastic limit, plasticity index, and specific surface and after addition of its nano-soil were also conducted. Laboratory tests results showed that the values of liquid limit and plastic limits were higher after nano-soil addition. However, its plasticity index reduces which is advantageous in many geotechnical constructions. Compressive strength of original soil-cement-1% nano-soil mixture showed almost double its value without nano-soil. It demonstrated that a small amount of these crushed particles or nano-soil can provide significant improvement in the geotechnical properties of soil. Thus, nanoparticles are potentially suitable for improving the properties of soil/clay for various applications.

Taha, M. R.

325

Composted municipal waste effect on chosen properties of calcareous soil  

NASA Astrophysics Data System (ADS)

A 3-year field study was conducted to assess effects of composted municipal waste on some properties, distribution of Zn, Cu in a calcareous soil and uptake of these metals by wheat. The treatments were 0, 25, 50 and 100 Mg ha-1 of municipal solidwastewhichwas applied in three consecutive years. The application of composted municipal waste increased the saturated hydraulic conductivity, the aggregate stability,the organic carbon content and electrical conductivity, whereas it slightly decreased the soil pH and bulk density. A significant increase in the concentration of Zn and Cu were observed with increasing number and rate of compost application. The distribution of Zn and Cu between the different fractions in untreated and treated soils showed that the majority of Zn and Cu were in the residual form. Finally, the levels of Zn and Cu were higher in grains of wheat grown in composttreated plots compared to that grown in the control plots.

Hamidpour, M.; Afyuni, M.; Khadivi, E.; Zorpas, A.; Inglezakis, V.

2012-10-01

326

Hydraulic properties of sphagnum peat moss and tuff (scoria) and their potential effects on water availability  

Microsoft Academic Search

The potential rate of water and nutrient supply to plant roots depends on the hydraulic properties of the container medium (growth medium, substrate), primarily on its unsaturated hydraulic conductivity, which is a measure of the medium's resistance to water flow. Water availability to plants grown in containers is usually being evaluated using criteria based exclusively on water characteristic curves of

F. F. Silva; R. Wallach; Y. Chen

1993-01-01

327

Soil hydraulic conductivity function based on specific liquid–vapor interfacial area around the soil particles  

Microsoft Academic Search

Water in soils flows through a tortuous path which depends on the specific liquid–vapor interfacial area around the soil particles (Aws) and tortuosity factor (?). This specific area is defined as the area of liquid–vapor interfacial around the soil particles per unit bulk volume of soil. The objective of this study was to develop a new approach for determining unsaturated

Sh Zand-Parsa; A. R Sepaskhah

2004-01-01

328

Testing soil water retention estimation with the MUUF pedotransfer model using data from the southern United States  

Microsoft Academic Search

Soil hydraulic properties have often been estimated rather than measured. Such estimates are made using pedotransfer functions (PTFs), i.e. regression equations relating soil hydraulic properties to soil basic properties. PTFs were developed from about 18,000 samples from the national soil characterization database that used the clay activity ratio along with texture to characterize the effect of soil minerals on soil

W. J Rawls; Y Pachepsky; M. H Shen

2001-01-01

329

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

330

Characterizing Soil Hydraulic Parameter Heterogeneity Using Cokriging and Artificial Neural Network: A Framework of Integrating Hard and Soft Data  

NASA Astrophysics Data System (ADS)

Characterization of the heterogeneity of hydraulic parameters that control transport processes in the vadose zone is always difficult due to prohibitive investments involved with direct parameter measurements (so-called `hard' data). `Soft' data such as moisture content (?) and results derived from geophysical measurements, however, carry significant information about media heterogeneity and should be included in site characterization, where possible. We developed a method to incorporate both `hard' and `soft' data using cokriging and artificial neural network (ANN) analyses to generate 3D spatially correlated structures of hydraulic parameters. This method was applied to a field injection experiment carried out in 2000 at the `Sisson and Lu' injection site at the U.S. Department of Energy's Hanford Site, WA. Available data included limited measurements of soil hydraulic parameters (i.e., saturated hydraulic conductivity and van Genuchten parameters, totaling 70 datasets) and soil characterization data (bulk density and percentages of gravel, coarse and fine sand, silt, and clay). A 3D initial ? field reflecting the geologic layering was available at 32 observation wells (1344 locations). We used variograms and cross-variograms to investigate the spatial correlation and cross-correlation of the initial ? measurements and soil characterization data variables. We used ANN-based pedotransfer functions to map soil characterization data to hydraulic parameters. Using initial ? as a secondary variable, we used a cokriging scheme to estimate 3D heterogeneous fields of the primary variables, the soil characterization data and, subsequently, 3D fields of the hydraulic parameters with the pedotransfer functions. These hydraulic parameter fields were then used to simulate the field injection experiment. The spatial moments of the measured and simulated ? were compared to evaluate the robustness of the developed method. The ? profiles at observation wells were investigated to explore the effect of soil hydraulic parameter heterogeneity on the movement and distribution of moisture due to injected fluid.

Ye, M.; Schaap, M. G.; Khaleel, R.; Zhu, J.

2005-12-01

331

The hydraulic conductivity of low permeability wet soils used as landfill lining and capping material: analysis of pressure infiltrometer measurements  

Microsoft Academic Search

The analysis of pressure infiltrometer measurements on low permeability wet soils used for landfill lining and capping material provided an estimate of values of field saturated hydraulic conductivity. Since the soil was almost saturated, steady-state flow through the ring was obtained soon after the start of a test without a significant initial unsteady absorption period. With the assumption that the

E. G. Youngs; P. B. Leeds-Harrison; D. E. Elrick

1995-01-01

332

Effect of the shape of the soil hydraulic functions near saturation on variably-saturated flow predictions  

Microsoft Academic Search

Relatively small changes in the shape of the soil water retention curve near saturation can significantly affect the results of numerical simulations of variably saturated flow, including the performance of the numerical scheme itself in terms of stability and rate of convergence. In this paper, we use a modified form of the van Genuchten–Mualem (VGM) soil hydraulic functions to account

T. Vogel; M. Th. van Genuchten; M. Cislerova

2000-01-01

333

AUTOMATION OF A FALLING HEAD PERMEAMETER FOR RAPID DETERMINATION OF HYDRAULIC CONDUCTIVITY ON MULTIPLE SAMPLES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil management can be improved if soil spatial variability is taken into account. We initiated a study to quantify spatial variability of soil hydraulic properties. Initially we focused on hydraulic conductivity of saturated soil (Ks) by horizons. In situ Ks measurements made in the Ap, Bt, and t...

334

Mulching effects on selected soil physical properties  

Microsoft Academic Search

The suitability of soil for sustaining plant growth and biological activity is a function of physical and chemical properties, many of which depend on the quantity and quality of soil organic matter. The equilibrium level of soil organic matter depends on the balance between input through plant residues and other biosolids and output through decomposition, erosion and leaching. However crop

Lukman Nagaya Mulumba; Rattan Lal

2008-01-01

335

Predicting soil properties in the tropics  

NASA Astrophysics Data System (ADS)

It is practically impossible to measure soil properties continuously at each location across the globe. Therefore, it is necessary to have robust systems that can predict soil properties at a given location. That is needed in many tropical countries where the dearth of soil property measurements is large. This paper reviews the use of pedotransfer functions (PTF) for predicting properties of soils in the tropics. First, the guiding principles of prediction and the type of predictors are discussed, including laboratory data, field description and soil morphology, electromagnetic spectrum, proximal and remote sensed data. In the subsequent section, PTFs are discussed for soil physical and chemical properties followed by infrared spectroscopy, proximal sensing and remote sensing. An analysis of ISRIC (mainly tropical) and USDA (mainly temperate) soil databases showed that soils in the tropics have higher clay content, lower cation exchange capacity, higher bulk density, lower water content at - 10 kPa and - 1500 kPa than soils in the temperate regions. Various methods developed in temperate regions can be applied for the soils in the tropical regions although calibration and careful selection of predictors remains necessary. It is concluded that PTFs are an important tool to overcome the dearth of soil data in many tropical countries.

Minasny, Budiman; Hartemink, Alfred E.

2011-05-01

336

The Influence of Glass Leachate on the Hydraulic, Physical, Mineralogical and Sorptive Properties of Hanford Sediment  

SciTech Connect

The Immobilized Low Activity Waste (ILAW) generated from the Hanford Site will be disposed of in a vitrified form. It is expected that leachate from the vitrified waste will have a high pH and high ionic strength. The objective of this study was to determine the influence of glass leachate on the hydraulic, physical, mineralogical, and sorptive properties of Hanford sediments. Our approach was to put solutions of NaOH, a simplified surrogate for glass leachate, in contact with quartz sand, a simplified surrogate for the Hanford subsurface sediment, and Warden soil, an actual Hanford sediment. Following contact with three different concentrations of sodium hydroxide solutions, changes in hydraulic conductivity, porosity, moisture retention, mineralogy, aqueous chemistry, and soil-radionuclide distribution coefficients were determined. Under chemical conditions approaching the most caustic glass leachate conditions predicted in the near-field of the ILAW disposal site, approximated by 0.3 M NaOH, significant changes in mineralogy were observed. The clay minerals of the Hanford sediment evidenced the greatest dissolution thereby increasing the relative proportions of the more resistant minerals, e.g., quartz, feldspar, and calcite, in the remaining mass. Some re-precipitation of solids (mostly amorphous gels) was observed after caustic contact with both solids; these precipitates increased the moisture retention in both sediments, likely because of water retained within the gel coatings. The hydraulic conductivities were slightly lower but, because of experimental artifacts, these reductions should not be considered significant. Thus, there does not seem to be large differences in the hydraulic properties of the quartz sand or Warden silt loam soil after 192 days of contact with caustic fluids similar to glass leachate. The long term projected impact of the increased moisture retention has not been evaluated but likely will not make past simplified performance projections invalid. Despite the fact that some clay minerals, smectites and kaolinite, almost totally dissolved within a year of contact with 3.0 M NaOH (and by inference after longer time frames for 0.3 M NaOH, a more realistic surrogate for ILAW glass leachate) other sorbing minerals such as illite and chlorite do not appreciably react. The net result on sorption of common and risk relevant mobile radionuclides is not expected to be significant. Specifically, little change in Cs-Kd values and a significant increase in Sr-Kd values were measured in the simulated glass leachates versus natural groundwater. The difference in the sorptive responses of the radionuclides was attributed to differences in sorption mechanisms (Cs sorbs strongly to high-energy sites, whereas Sr sorbs primarily by cation exchange but also is sensitive to pH mediated precipitation reactions). Caustic treated sediments contacted with NaOH solutions radiotraced with Sr exhibited high Kd’s likely because of precipitation with CaCO3. In caustic solutions there was no appreciable adsorption for the three anions I-, SeO42-, or TcO4-. In the “far field” vadose zone in past performance projections, some sorption has been allowed for selenate. Even if the caustic glass leachate completely dominates the entire vadose zone below the repository, such that there will be no sorption of selenate, the dilution and pH neutralization that will occur in the upper unconfined aquifer will allow selenate adsorption to occur onto the aquifer sediments. It is recommended that a future performance assessment sensitivity run be performed to address this point.

Kaplan, Daniel I.; Serne, R. Jeffrey; Schaef, Herbert T.; Lindenmeier, Clark W.; Parker, Kent E.; Owen, Antionette T.; McCready, David E.; Young, James S.

2003-08-26

337

Estimating the water retention curve from soil properties: comparison of linear, nonlinear and concomitant variable methods  

Microsoft Academic Search

The unsaturated soil hydraulic functions involving the soil–water retention curve (SWRC) and the hydraulic conductivity provide useful integrated indices of soil quality. Existing and newly devised methods were used to formulate pedotransfer functions (PTFs) that predict the SWRC from readily available soil data. The PTFs were calibrated using a large soils database from Hungary. The database contains measured soil–water retention

Kálmán Rajkai; Sándor Kabos; M. Th. van Genuchten

2004-01-01

338

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

Microsoft Academic Search

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)

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

2007-01-01

339

The use of One-Dimensional Laboratory Experiments to Assess Hydraulic Processes in Wastewater Soil Absorption Systems  

Microsoft Academic Search

Sixteen, one-dimensional column lysimeters have been developed to evaluate the influence of loading regime and infiltrative surface character on hydraulic performance in wastewater soil absorption systems. A duplicate design was utilized to evaluate two infiltrative surface conditions (gravel-free vs. gravel-laden) under four hydraulic loading regimes representative of possible field conditions. By loading the columns at rates of 25 to 200

D. N. Huntzinger; J. E. McCray; R. Siegrist; K. Lowe; S. VanCuyk

2001-01-01

340

Impact of soil water property parameterization on atmospheric boundary layer simulation  

NASA Astrophysics Data System (ADS)

Both the form of functional relationships applied for soil water properties and the natural field-scale variability of such properties can significantly impact simulation of the soil-plant-atmosphere system on a diurnal timescale. Various input parameters for soil water properties including effective saturation, residual water content, anerobiosis point, field capacity, and permanent wilting point are incorporated into functions describing soil water retention, hydraulic conductivity, diffusivity, sorptivity, and the plant sink function. The perception of the meaning of these values and their variation within a natural environment often differs from the perspective of the soil physicist, plant physiologist, and atmospheric scientist. This article investigates the sensitivity of energy balance and boundary layer simulation to different soil water property functions using the Oregon State University coupled atmosphere-plant-soil (CAPS) simulation model under bare soil conditions. The soil parameterizations tested in the CAPS model include those of Clapp and Hornberger [1978], van Genuchten [1980], and Cosby et al. [1984] using initial atmospheric conditions from June 16, 1986 in Hydrologic Atmospheric Pilot Experiment-Modélisation du Bilan Hydrique (HAPEX-MOBILHY). For the bare soil case these results demonstrate unexpected model sensitivity to soil water property parameterization in partitioning all components of the diurnal energy balance and corresponding boundary layer development.

Cuenca, Richard H.; Ek, Michael; Mahrt, Larry

1996-03-01

341

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

342

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

343

A Statistical Model for Predicting Unsaturated Hydraulic Properties of Deep Sediments at the Idaho National Engineering and Environmental Laboratory  

NASA Astrophysics Data System (ADS)

The development and application of property-transfer functions is an important approach for predicting unsaturated hydraulic properties from more easily measured bulk properties. At the Idaho National Engineering and Environmental Laboratory (INEEL), the unsaturated zone is comprised of thick basalt flow sequences interbedded with thinner sedimentary layers. Buried hazardous waste in the surficial soil is a possible source of contamination to the underlying Snake River Plain aquifer, which can be as deep as 200 m below land surface. Determining the unsaturated hydraulic properties of the sedimentary layers is one step in understanding water flow and solute transport processes through this complex unsaturated system. This study uses multiple linear regression analysis to construct simple property-transfer functions for estimating the water retention curve for deep sediments at the INEEL. The regression models were developed using laboratory measurements on 109 sediment core samples collected at depths of 9 m to 175 m at two facilities within the southwestern portion of the INEEL. These data included water retention measurements, the curve fit parameters for which are the dependent variables of the property-transfer functions, and bulk properties (such as bulk density and various representations of the particle-size distribution), which are the potential independent variables. The Rossi-Nimmo junction model was used to represent the water retention measurements. Three parameters define this retention curve model: 1) saturated water content (? sat), 2) a scaling parameter for matric pressure (? o), and 3) a curve shape parameter (? ). The bulk property data and optimized hydraulic parameter values were used to develop a separate regression model for each parameter. The predicted parameters were then used to calculate the water retention curve from saturation to oven dryness. A selection process for the independent variables, referred to as "all possible subsets regression," was used to determine the best predictive model for each hydraulic parameter. Preliminary regression results show that textural class percentages were consistently better able to explain the hydraulic parameters than were other potential representations of the particle-size distribution. The adjusted coefficient of determination (adjusted R2) for the best models, which consisted of some linear combination of textural class percentages and bulk density, ranged between 0.2 and 0.5 when all observations were included in the regression analyses. The residuals were close to normally distributed and were fairly homoscedastic when plotted versus the predicted dependent variable values. The low adjusted R2 values may indicate that the bulk property data used in calibrating the models are not sufficient to completely predict the hydraulic parameters or may indicate significant measurement errors in the dependent or independent variables. Other bulk property data not available for calibrating the property-transfer functions, such as mineralogy, specific surface areas, or adsorption capacities, might correlate more strongly with the hydraulic parameters, and thus may be useful in future regression analyses. The property-transfer functions from this study provide a basis for development of a theoretical model that relies on physical relationships between the pore-size distribution and the bulk properties of the media and that should be more universal in its application throughout the INEEL and other geographic locations.

Winfield, K. A.; Nimmo, J. R.

2003-12-01

344

Setting properties and sealing ability of hydraulic temporary sealing materials  

Microsoft Academic Search

This study sought to investigate the setting progress and sealing ability of hydraulic temporary sealing materials used in endodontic treatment: Lumicon, Caviton, and HY-Seal. To evaluate setting progress, the materials were fi lled into glass tubes with one end sealed and immersed in water. After immersion, a measurement apparatus was inserted from the non- immersed end and the set area

Yoko OGURA; Ichiroh KATSUUMI

2008-01-01

345

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

346

Chapter 34 Fitting Soil Property Spatial Distribution Models in the Mojave Desert for Digital Soil Mapping  

Microsoft Academic Search

We developed models from soil profile descriptions and GIS landscape analysis to estimate the spatial distribution of soil properties to assist soil scientists with soil-landscape information. Soil profile descriptions were obtained within soil survey projects in the Mojave Desert of southeastern California, USA. Sites were located on broad alluvial fans. Soil development varied from young soils with little or no

D. Howell; Y. Kim; C. Haydu-Houdeshell; P. Clemmer; R. Almaraz; M. Ballmer

2006-01-01

347

Development and Testing of a Model to Assess Subsurface Moisture Gradients From Diurnal Surface Temperatures and Soil Thermophysical Properties  

Microsoft Academic Search

A one-dimensional, finite difference coupled heat and moisture transfer model for unsaturated zone porous media flow has been developed and tested. Inputs to the model include soil surface excursions, site topography, meteorological data, and detailed information about the soil thermophysical and hydraulic properties. Assuming homogeneity or knowledge of the stratification of the soil column and steady-state conditions (i.e. no recharge),

L. E. Griggs; R. E. Arvidson

2002-01-01

348

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

349

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

NASA Astrophysics Data System (ADS)

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.

2013-05-01

350

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

351

High-quality unsaturated zone hydraulic property data for hydrologic applications  

Microsoft Academic Search

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

Kim Perkins; John Nimmo

2009-01-01

352

Biochemical Properties of Soil Contaminated by Petrol  

Microsoft Academic Search

In this experiment the effects of lead and lead-free petrol applied at the following doses of: 0, 2, 4 and 6 cm 3 • kg' 1 of soil on growth and development of triticale and biochemical properties of the soil were studied. For detoxication of petrol organic amendment with barley straw was applied. The experiment was performed in two experimental

J. Wyszkowska; J. Kucharski

353

Generating hydraulic properties from non-equilibrium water-retention curves  

NASA Astrophysics Data System (ADS)

Water retention curves, particularly those obtained from ceramic plate experiments, tend overestimate the equilibrium water content at high tensions and thus imply unrealistic amounts of water present in films etc. We have previously reported a method to predict non-equilibrium water-retention data from known fractal equilibrium water-retention curves. This method relates actual water loss to the product of the equilibrium water loss and the ratio of two different percolation-based calculations of the hydraulic conductivity. Here we reverse the process and generate the equilibrium water-retention curve from data. No particular form of pore- size distribution is assumed, although extrapolation procedures and a posteriori checks are used. The results we obtained make sense and imply water film contents of roughly 0.01 instead of 0.05 or higher in the coarse Hanford site soils investigated. From a reliable equilibrium pore-size distribution, percolation theory yields all flow and transport properties. Work supported by NSF grant EAR-0609884.

Hunt, A. G.; Skinner, T. E.

2008-12-01

354

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...

355

Hydraulic Lift Increases Herbivory by Diaprepes abbreviatus Larvae and Persistence of Steinernema riobrave in Dry Soil.  

PubMed

Citrus seedlings were grown in double pots that separated the root systems into discrete lower and upper zones to test the hypothesis that hydraulic lift affects persistence and efficacy of entomopathogenic nematodes. Three treatments were established: (i) both pots were irrigated at water potential soil in the top pots of all treatments. During 27 days, the water potential in soil in the top pots of both the partial and complete drought treatments declined to ca. -160 kPa. A greater number of nematodes (P soil as motile IJ under conditions of partial drought (143/pot) than under no drought (6.1/pot) or complete drought (4.4/pot). A second experiment was initiated with the same treatments as the first, except that only half of the 20 replicates in each moisture regime were inoculated with nematodes. After 15 days, all top pots were irrigated and two larvae of the insect Diaprepes abbreviatus were added to all of the top pots in each treatment. Irrigation regimes were reinstituted until water potential in the top pots under partial and complete drought had again declined to ca. -150 kPa and the experiment was terminated. In the absence of nematodes, the damage to tap roots caused by D. abbreviatus feeding under partial drought and complete drought was 80% and 32%, respectively, of that under no drought. Numbers of motile IJ in soil were greater under conditions of partial drought (736/pot) than under complete drought (2.0/pot) or no drought (7.2/pot). Survival of D. abbreviatus and insect damage to roots were reduced by the presence of S. riobrave to a greater extent under partial drought as compared to other treatments. Hydraulic lift from the lower to the upper rhizosphere appears to have modulated the effect of dry soil conditions on feeding behavior of D. abbreviatus and created favorable conditions for persistence and efficacy of the entomopathogenic nematode. PMID:19266011

Duncan, L W; McCoy, C W

2001-06-01

356

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

357

Physical properties of tilled soils  

Microsoft Academic Search

The key areas of soil physics: structure, water, aeration, and strength and stability are discussed. Recent developments in experimental techniques and theory are reviewed. In addition, some older research is discussed where it is thought to be worthy of re-examination. It is concluded that for studies of tilled and other structured soils, measurements of bulk density and gravimetric water content

A. R. Dexter

1997-01-01

358

Analytic Description of the Unsaturated Hydraulic Properties of Structured Media  

Microsoft Academic Search

Dual-porosity and dual-permeability models are increasingly used to describe preferential flow in unsaturated structured media (macroporous soils, fractured rock). Such models assume that the medium consists of two interacting pore regions, one associated with the macropore or fracture network, and one with micropores inside soil aggregates or rock matrix blocks. Different formulations arise depending upon how water and\\/or solute movement

M. T. van Genuchten; M. G. Schaap; J. Simunek

2001-01-01

359

Shear Strength and Elastic Properties of Lime-Soil Mixtures.  

National Technical Information Service (NTIS)

The shear strength and elastic properties of soil-lime mixtures and the effects of curing time and soil type on these properties were studied using four typical Illinois soils. Regression equations relating cohesion and modulus of elasticity to unconfined...

M. R. Thompson

1967-01-01

360

Passive characterization of hydrofracture properties using signals from hydraulic pumps  

SciTech Connect

Massive hydraulic fracturing is used to enhance production from the low-permeability diatomite fields of Kern County, CA. Although critical for designing injection and recovery well patterns, the in-situ hydraulic fracture geometry is poorly understood. In 1990, Shell conducted an extensive seismic monitoring experiment on several hydrofractures prior to a steam drive pilot to characterize hydrofracture geometry. The seismic data were recorded by cemented downhole geophone arrays in three observation holes (MO-1, MO-2, and MO-3) located near the hydraulic fracture treatment wells. Using lowpass filtering and moveout analysis, events in the geophone recordings are identified as conical shear waves radiating from tube waves traveling down the treatment well. These events appear to be created by the hydraulic pumps, since their amplitudes are correlated with the injection rate and the wellhead pressure. Conical wave amplitudes are related to the tube wave attenuation in the treatment well and to wave-propagation characteristics of the shear component traveling in the earth. During the main fracturing stage, geophones above the fracture zone for wells MO-1 and MO-2 (both roughly along the inferred vertical fracture plane) exhibited conical-wave amplitude increases that are caused by shear wave reflection/scattering off the top of a fracture zone. From changes in the reflection amplitude as a function of depth, we interpret that the fracture zone initially extends along a confined vertical plane at a depth that correlates with many of the microseismic events. Toward the end of the main fracturing stage, the fracture zone extends upward and also extends in width, although we cannot determine the dimensions of the fracture from the reflection amplitudes alone. For all wells, we observe that the reflection (and what we infer to be the initial fracture) begins during a time period where no marked change in fracture pressure or injection rate or slurry concentration is observed. As the main fracturing stage progressed, we observed a significant decrease in amplitude for geophones below the top of the fracture zone. The attenuation was most pronounced for wells MO-1 and MO-2 (along the fracture plane). However, near the end of the main stage, well MO-3 also exhibited a significant amplitude decrease, suggesting the development of a fractured ''process zone'' around the main fracture plane. In addition, well MO-3 also exhibited an amplitude decrease in an interval well below the initial fracture zone. Both the interval and the direction (toward MO-3) correspond with temperature log increases observed during later steam injection.

Rector III, J.W.; Dong, Q.; Patzek, T.W.

1999-01-02

361

Wavelet-based multifractal analysis of field scale variability in soil water retention  

Microsoft Academic Search

Better understanding of spatial variability of soil hydraulic parameters and their relationships to other soil properties is essential to scale-up measured hydraulic parameters and to improve the predictive capacity of pedotransfer functions. The objective of this study was to characterize scaling properties and the persistency of water retention parameters and soil physical properties. Soil texture, bulk density, organic carbon content,

Takele B. Zeleke; Bing C. Si

2007-01-01

362

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

363

Development of a New Apparatus for Investigating Acoustic Effects on Hydraulic Properties of Low-Permeability Geo-Materials  

NASA Astrophysics Data System (ADS)

Remediation of polluted soils and groundwater contaminated by heavy metals and non-aqueous phase liquids has been one of the challenging issues in the field of geo-environments. In-situ removal of the contaminants from low permeable soils, such as clay strata, is particularly difficult because of the low mobility, strong adsorption, and/or other various interactions within soils. Thus current remediation techniques, such as pump- and-treat method and even eletrokinetic method, generally suffer from low recovery rates and/or economically unacceptable long remediation periods. A perspective improvement in remediation technology is to couple the electrokinetic method with an application of acoustic waves. This so-called Electro-Acoustic Soil Decontamination (EASD) method has been proposed by Battelle Columbus Labs.(Muralidhara et al. 1990). Simultaneous application of an electric field and an acoustic field may produce a synergistic effect and result in further enhancement of water transport by electro-osmosis in principle, but there is still no fundamental data for the design of EASD method in practical applications. A number of investigations have shown that an application of acoustic waves can increase hydraulic conductivity and mobility of non-aqueous phase liquids in porous media. Most of the prior and ongoing researches in this area have been focused on increasing production from declining oil and gas reservoirs. During several field tests by the oil and gas industries, increases in oil production rates by 20% or more have been reported. However, underlying physical mechanisms for acoustically enhanced fluid transport are not adequately understood. In addition, majority of the past investigations has dealt with applications of large amplitude of acoustic waves to relatively permeable soils or fractured rocks, and there is little information if acoustic wave effectively enhances flow and contaminant transport for less permeable clayey soils. To evaluate the feasibility of the EASD method and to obtain the fundamental but important knowledge for the design of this method, it is first necessary to understand the effects of acoustic wave application on pore water flow behavior. A new apparatus is developed to investigate the effects of acoustic wave on hydraulic properties of soil sample. This test apparatus enables to confine a cylindrical specimen under hydrostatic pressure conditions and to apply acoustic wave simultaneously. Preliminary results associated with the effects of acoustic wave frequency on changes of permeability of kaolin clay samples are illustrated in this report. A program investigating the effects of electricity and pore water chemistry on efficiency of decontamination using the same samples is also ongoing and briefly presented. The two strategies for enhancing the efficiency of remediation for low permeable soils will be combined in the near future

Nakajima, H.; Sawada, A.; Sugita, H.; Takeda, M.; Komai, T.; Zhang, M.

2006-12-01

364

THE BALANCED ENTROPY INDEX TO CHARACTERIZE SOIL TEXTURE FOR SOIL WATER RETENTION ESTIMATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pedotransfer procedures are often used to estimate soil hydraulic properties from soil basic data available from soil surveys. Soil particle size distribution, or texture, is known to be a leading soil property affecting soils' ability to retain and transmit water and solutes. A substantial effort h...

365

In-Situ Hydraulic Conductivities of Soils and Anomalies at a Future Biofuel Production Site  

NASA Astrophysics Data System (ADS)

Forested hillslopes of the Upper Coastal Plain at the Savannah River Site, SC, feature a shallow clay loam argillic layer with low median saturated hydraulic conductivity. Observations from a grid of shallow, maximum-rise piezometers indicate that perching on this clay layer is common. However, flow measurements from an interflow-interception trench indicate that lateral flow is rare and most soil water percolates through the clay layer. We hypothesize that the lack of frequent lateral flow is due to penetration of the clay layer by roots of pine trees. We used ground penetrating radar (GPR) to map the soil structure and potential anomalies, such as root holes, down to two meters depth at three 10×10-m plots. At each plot, a 1×10-m trench was later back-hoe excavated along a transect that showed the most anomalies on the GPR maps. Each trench was excavated at 0.5-m intervals until the clay layer was reached (two plots were excavated to a final depth of 0.875 m and the third plot was excavated to a final depth of 1.0 m). At each interval, compact constant-head permeameters (CCHPs) were used to measure in-situ hydraulic conductivities in the clay-loam matrix and in any visually apparent anomalies. Conductivity was also estimated using a second 1×10-m transect of CCHP measurements taken within randomly placed augur holes. Additional holes targeted GPR anomalies. The second transect was created in case the back-hoe impacted conductivity readings. High-conductivity anomalies were also visually investigated by excavating with a shovel. Photographs of soil wetness were taken at visually apparent anomalies with a multispectral camera. We discovered that all visually apparent anomalies found are represented on the GPR maps, but that not all of the predicted anomalies on the GPR maps are visually apparent. We discovered that tree root holes create anomalies, but that there were also many conductivity anomalies that could not be visually distinguished from low-conductivity soil.

Williamson, M. F.; Jackson, C. R.; Hale, J. C.; Sletten, H. R.

2010-12-01

366

Characterizing scale- and location-dependent correlation of water retention parameters with soil physical properties using wavelet techniques.  

PubMed

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. The objective of this study was to examine the scale- and location-dependent correlation between two water retention parameters (alpha and n) in the van Genuchten (1980) function and soil physical properties (sand content, bulk density [Bd], and organic carbon content) using wavelet techniques. Soil samples were collected from a transect from Fuxin, China. Soil water retention curves were measured, and the van Genuchten parameters were obtained through curve fitting. Wavelet coherency analysis was used to elucidate the location- and scale-dependent relationships between these parameters and soil physical properties. Results showed that the wavelet coherence between alpha and sand content was significantly different from red noise at small scales (8-20 m) and from a distance of 30 to 470 m. Their wavelet phase spectrum was predominantly out of phase, indicating negative correlation between these two variables. The strong negative correlation between alpha and Bd existed mainly at medium scales (30-80 m). However, parameter n had a strong positive correlation only with Bd at scales between 20 and 80 m. Neither of the two retention parameters had significant wavelet coherency with organic carbon content. These results suggested that location-dependent scale analyses are necessary to improve the performance for soil water retention characteristic predictions. PMID:18948482

Shu, Qiaosheng; Liu, Zuoxin; Si, Bingcheng

2008-10-23

367

Electrical-impedance spectroscopy of sedimentary rocks: prediction of hydraulic conductivity and soil water retention curves  

Microsoft Academic Search

The broadband electrical-impedance response of rocks and soils is a complex function of the pore solution chemistry, the sample microgeometry, and the surface chemical properties of the system. The conductivity and dielectric responses, which are obtained from impedance measurements, are also strong functions of the measurement frequency. The dispersion in the conductivity and dielectric responses is controlled by physiochemical polarization

D. Lesmes

2003-01-01

368

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...

369

Decoupling the Influence of Leaf and Root Hydraulic Conductances on Stomatal Conductance and its Sensitivity to Vapor Pressure Deficit as Soil Dries in a Drained Loblolly Pine Plantation  

NASA Astrophysics Data System (ADS)

The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on plant hydraulic properties and water balances are not well studied. Precipitation and soil moisture in North America will be modified in the future and forest trees in the US will be challenged by warmer temperature, higher leaf-to-air water vapor pressure deficit (D), and more frequent summer droughts. Many studies have examined the relationships between whole tree hydraulic conductance (Ktree) and stomatal conductance (gs), but Ktree remains an ill-defined quantity because it depends on a series of resistances, mainly controlled by the conductance in roots (Kroot) and leaves (Kleaf). To explain the variation in Ktree, we characterized Kroot and Kleaf and how they responded to environmental drivers such as soil moisture availability and D. In addition, the role of dynamic variations in Kroot and Kleaf in mediating stomatal control of transpiration and its response to D was studied. The 2007 summer drought was used as a means to challenge the hydraulic system, allowing testing how broadly predictions about its behaviour hold outside the range of typical conditions. Roots and leaves were the weakest points in the whole tree hydraulic system, and contributed for more than 75% of the total tree hydraulic resistance. Effects of drought on Ktree altered the partitioning of the resistance between roots and leaves and as soil moisture declined below 50% relative extractable water (REW), Kroot declined faster than Kleaf and became the dominant hydraulic fuse regulating Ktree. Although Ktree depended on soil moisture, its dynamics was tempered by current-year needle elongation that increased significantly Kleaf during the dry months when REW was below 50%. To maintain the integrity of the xylem hydraulic continuum from roots to leaves, stomata were highly responsive in coordinating transpiration with dynamic variation in Ktree. Daily maximum gs and its sensitivity to D decreased exponentially with decreasing soil moisture below 50% REW. After correcting for the effect of D on gs, the seasonnal decline in Ktree caused a 35% decrease in gs and in its sensitivity to D, response that was mainly driven by the decrease in Kroot with declining soil moisture. While the mechanism remains unknown, stomatal closure occurred as a feedback response to some aspect of transpiration related to Ktree, rather than as a direct response to D. The present study appears to be the first showing the respective role of woody vs. leaf component on the seasonal changes in Ktree, and the effect of such changes on gs and its sensitivity to D. We conclude that even in wet forests of North Carolina, dynamic water stress in response to climate change would reduce Ktree and impose a series of constraints on the water and carbon economy of the plant, such as lower gs and lower stomatal control. Furthermore, any factors influencing leaf phenology would impair the tight coordination between Ktree and gs and would affect the acclimation of trees to changing environmental conditions.

Domec, J.; Noormets, A.; King, J. S.; McNulty, S. G.; Sun, G.; Gavazzi, M. J.; Boggs, J. L.

2008-12-01

370

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...

371

Evolution of unsaturated hydraulic properties of municipal solid waste with landfill depth and age  

Microsoft Academic Search

Successful modeling of liquid and air flow and hence designing of liquid and air addition systems in the landfills are constrained by the lack of key parameters of unsaturated hydraulic properties of municipal solid waste (MSW), which are strongly dependent on the depth of burial and the degree of decomposition. In this study, water retention curves (WRC) of MSW are

Huayong Wu; Hongtao Wang; Yan Zhao; Tan Chen; Wenjing Lu

372

Normal-stress dependence of fracture hydraulic properties including two-phase flow properties  

NASA Astrophysics Data System (ADS)

A systematic approach has been developed for determining relationships between normal stress and fracture hydraulic properties, including two-phase flow properties. The development of a relationship between stress and fracture permeability (or fracture aperture and fracture closure) is based on a two-part Hooke's model (TPHM) that captures heterogeneous elastic-deformation processes at a macroscopic scale by conceptualizing the rock mass (or a fracture) into two parts with different mechanical properties. The developed relationship was verified using a number of datasets in the literature for fracture closure versus stress, and satisfactory agreements were obtained. TPHM was previously shown to be able to accurately represent testing data for porous media as well. Based on the consideration that fracture-aperture distributions under different normal stresses can be represented by truncated-Gaussian distributions, closed-form constitutive relationships were developed between capillary pressure, relative permeability and saturation, for deformable horizontal fractures. The usefulness of these relationships was demonstrated by their consistency with a laboratory dataset.

Liu, Hui-Hai; Wei, Ming-Yao; Rutqvist, Jonny

2013-03-01

373

A comparison of indexing methods to evaluate quality of soils subjected to different erosion: the role of soil microbiological properties.  

NASA Astrophysics Data System (ADS)

Soil quality assessment is needed to evaluate the soil conditions and sustainability of soil and crop management properties, and thus requires a systematic approach to select and interpret soil properties to be used as indicators. The aim of this work was to evaluate and compare different indexing methods to assess quality of an undisturbed grassland soil (UN), a degraded pasture soil (GL) and a no tilled soil (NT) with four different A horizon depths (25, 23, 19 and 14 cm) reflecting a diverse erosion. Twenty four soil properties were measured from 0 to10 (1) and 10 to 20 cm. (2) and a minimum data set was chosen by multivariate principal component analysis (PCA) considering all measured soil properties together (A), or according to their classification in physical, chemical or microbiological (B) properties. The measured soil properties involved either inexpensive or not laborious standard protocols, to be used in routine laboratory analysis (simple soil quality index - SSQI), or a more laborious, time consuming and expensive protocols to determine microbial diversity and microbial functionality by methyl ester fatty acids (PLFA) and catabolic response profiles (CRP), respectively (complex soil quality index - CSQI). The selected properties were linearly normalized and integrated by the weight additive method to calculate SSQI A, SSQI B, CSQI A and CSQI B indices. Two microbiological soil quality indices (MSQI) were also calculated: the MSQI 1 only considered microbiological properties according to the procedure used for calculating SQI; the MSQI 2 was calculated by considering microbial carbon biomass (MCB), microbial activity (Resp) and functional diversity determined by CPR (E). The soil quality indices were SSQI A = MCB 1 + Particulate Organic Carbon (POC)1 + Mean Weight Diameter (MWD)1; SSQI B = Saturated hydraulic conductivity (K) 1 + Total Organic Carbon (TOC) 1 + MCB 1; CSQI A = MCB 1 + POC 1 + MWD 1; CSQI B = K 1+ TOC 1+ 0.3 * (MCB 1+ i/a +POC 1) + 0,05 * (E + cy/pre), where i/a and cy/pre are the iso/anteiso and cyclopropyl/precursors ratios determined by PLFA; MSQI 1 (0,3 * (MCB 1+ i/a 1 +POC 1) + 0,05 * (E 1+ cy/pre 1) ) and MSQI 2 (MCB 1+Resp 1+ E 1). All the calculated indices differentiated references plots (UN and GL), from those under no tillage (NT) system. Values were similar in NT plots with low erosion levels (NT 25 and 23) but higher than values of plots with high erosion (NT 19 and 14). Soil quality indices constructed by procedure B, (SSQI B and CSQI B) differentiated among the studied plots with the same or higher sensitivity than the other indices and allowed evaluating the impact of soil management practices and erosion on soil physical, chemical and microbiological properties. The lack of indicators representing all soil properties (physical, chemical and biological) in SQI constructed by procedure A could decrease the index sensitivity to changes in management; and the same may happen when physical, chemical and biological properties present different weights into the calculated SQI. The inclusion of CRP and PLFA data in the indices slightly increased or did not increase the index sensitivity (CSQI A and CSQI B). Generally microbiological indices (MSQI 1 and MSQI 2) were highly sensitive to soil erosion. However, we suggest that indices integrating physical, chemical and microbiological properties may give a more complete view of the soil quality than indices only based on measurement of a few microbiological properties.

Romaniuk, Romina; Lidia, Giuffre; Alejandro, Costantini; Norberto, Bartoloni; Paolo, Nannipieri

2010-05-01

374

Comparison of methods for measuring vertical hydraulic properties in a sedimentary rock aquifer  

NASA Astrophysics Data System (ADS)

The characterization of groundwater flow in fractured bedrock aquifers is presently based on a variety of hydraulic testing methods. Pumping tests are often employed, the interpretation of which are based on models derived for porous media environments that do not fully represent the complexities of fractured rock settings. In this paper, we measure aquifer properties using a variety of testing methods in order to evaluate which methods are best capable of producing reliable parameter estimates. The study was performed in a fractured sedimentary rock aquifer using four different field methods: constant head tests conducted using a straddle-packer system, pulse interference tests conducted under open-hole conditions, 12-hour isolated interval pumping tests and 48-hour open-hole pumping tests. Using the results of the constant head tests as the most reliable method for estimation of hydraulic conductivity and specific yield, the results obtained using the other three methods were compared with particular emphasis on the estimation of vertical hydraulic parameters in this setting. The effects of test measurement scale on hydraulic parameter estimates were also investigated. Evaluation of the open-hole pumping test data was performed using an analytical model that accommodates multiple horizontal fractures and a connection to a free surface boundary. The comparison shows that estimates of horizontal hydraulic conductivity were not dependent on test method with all methods providing equivalent results. Open-well pumping tests, however, were found not to reliably estimate values of vertical hydraulic conductivity and specific yield for this setting. Alternatively, pulse interference tests conducted under open-hole conditions may offer a less time-intensive option to constant head injection tests for determining vertical hydraulic parameters in a sedimentary rock setting.

Novakowski, Kent; Worley, Jessica

2013-04-01

375

Estimating the Effective Soil Temperature at L-Band as a Function of Soil Properties  

Microsoft Academic Search

To retrieve soil moisture from L-band microwave radiometry, it is necessary to account for the effects of temperature within both vegetation and soil media. To compute the effective soil temperature TG, several simple formulations accounting for soil temperatures at the surface and at depth and surface soil moisture have been developed. However, the effects of the soil physical properties in

Jean-Pierre Wigneron; André Chanzy; Patricia de Rosnay; Christoph Rudiger; Jean-Christophe Calvet

2008-01-01

376

Method for Coincidentally Determining Soil Hydraulic Conductivity and Moisture Retention Characteristics.  

National Technical Information Service (NTIS)

A constant-head permeameter has been modified to include the essential components of a Tempe cell moisture extractor. With this equipment, tests for saturated hydraulic conductivity (permeability), unsaturated hydraulic conductivity and moisture retention...

J. Ingersoll

1981-01-01

377

Near Surface Electrical Characterization of Hydraulic Conductivity: From Petrophysical Properties to Aquifer Geometries—A Review  

Microsoft Academic Search

This paper reviews the recent geophysical literature addressing the estimation of saturated hydraulic conductivity (K) from static low frequency electrical measurements (electrical resistivity, induced polarization (IP) and spectral induced\\u000a polarization (SIP)). In the first part of this paper, research describing how petrophysical relations between electrical properties\\u000a and effective (i.e. controlling fluid transport) properties of (a) the interconnected pore volumes and

Lee Slater

2007-01-01

378

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

379

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

NASA Astrophysics Data System (ADS)

Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an effective means to characterize the heterogeneity and spatial variability of soil hydraulic properties in a given study area. The statistical significance of this approach largely depends on the number of soil samples collected. Unfortunately, direct measurement of the soil hydraulic functions is tedious, expensive and time consuming. Here we present a simple and cost-effective hybrid scaling approach that combines the use of ancillary information (e.g., particle-size distribution and soil bulk density) with direct measurements of saturated soil water content and saturated hydraulic conductivity. Our results demonstrate that the presented approach requires far fewer laboratory measurements than conventional scaling methods to adequately capture the spatial variability of soil hydraulic properties.

Nasta, Paolo; Romano, Nunzio; Assouline, Shmuel; Vrugt, Jasper A.; Hopmans, Jan W.

2013-07-01

380

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

381

The effect of hydraulic lift on organic matter decomposition, soil nitrogen cycling, and nitrogen acquisition by a grass species  

Microsoft Academic Search

Hydraulic lift (HL) is the passive movement of water through plant roots, driven by gradients in water potential. The greater\\u000a soil–water availability resulting from HL may in principle lead to higher plant nutrient uptake, but the evidence for this\\u000a hypothesis is not universally supported by current experiments. We grew a grass species common in North America in two-layer\\u000a pots with

Cristina ArmasJohn; John H. Kim; Timothy M. Bleby; Robert B. Jackson

382

Radial Hydraulic Conductivity of Individual Root Tissues of Opuntia ficus-indica(L.) Miller as Soil Moisture Varies  

Microsoft Academic Search

The constraints on water uptake imposed by individual root tissues were examined forOpuntia ficus-indicaunder wet, drying, and rewetted soil conditions. Root hydraulic conductivity (LP) and axial conductance (Kh) were measured for intact root segments from the distal region with an endodermis and from midroot with a periderm;LPwas then measured for each segment with successive tissues removed by dissection. Radial conductivity

GRETCHEN B. NORTH; PARK S. NOBEL

1996-01-01

383

Property-Transfer Modeling to Estimate Unsaturated Hydraulic Conductivity of Deep Sediments at the Idaho National Laboratory, Idaho  

USGS Publications Warehouse

The unsaturated zone at the Idaho National Laboratory is complex, comprising thick basalt flow sequences interbedded with thinner sedimentary layers. Understanding the highly nonlinear relation between water content and hydraulic conductivity within the sedimentary interbeds is one element in predicting water flow and solute transport processes in this geologically complex environment. Measurement of unsaturated hydraulic conductivity of sediments is costly and time consuming, therefore use of models that estimate this property from more easily measured bulk-physical properties is desirable. A capillary bundle model was used to estimate unsaturated hydraulic conductivity for 40 samples from sedimentary interbeds using water-retention parameters and saturated hydraulic conductivity derived from (1) laboratory measurements on core samples, and (2) site-specific property transfer regression models developed for the sedimentary interbeds. Four regression models were previously developed using bulk-physical property measurements (bulk density, the median particle diameter, and the uniformity coefficient) as the explanatory variables. The response variables, estimated from linear combinations of the bulk physical properties, included saturated hydraulic conductivity and three parameters that define the water-retention curve. The degree to which the unsaturated hydraulic conductivity curves estimated from property-transfer-modeled water-retention parameters and saturated hydraulic conductivity approximated the laboratory-measured data was evaluated using a goodness-of-fit indicator, the root-mean-square error. Because numerical models of variably saturated flow and transport require parameterized hydraulic properties as input, simulations were run to evaluate the effect of the various parameters on model results. Results show that the property transfer models based on easily measured bulk properties perform nearly as well as using curve fits to laboratory-measured water retention for the estimation of unsaturated hydraulic conductivity.

Perkins, Kim S.; Winfield, Kari A.

2007-01-01

384

Hydraulic properties of Pinus halepensis, Pinus pinea and Tetraclinis articulata in a dune ecosystem of Eastern Spain  

Microsoft Academic Search

The hydraulic properties of Pinus pinea, Pinus halepensis and Tetraclinis articulata were studied in a coastal dune area from Eastern Spain. The measured variables include vulnerability to xylem embolism (vulnerability curves), hydraulic conductivity and carbon isotopic discrimination in leaves. Leaf water potentials were also monitored in the three studied populations during an extremely dry period. Our results showed that roots

Imma Oliveras; Jordi Martínez-Vilalta; Teresa Jimenez-Ortiz; Maria José Lledó; Antoni Escarré; Josep Piñol

2003-01-01

385

Antifungal properties of chitinolytic dune soil bacteria  

Microsoft Academic Search

Anti-fungal properties of chitinolytic soil bacteria may enable them to compete successfully for chitin with fungi. Additionally, the production of chitinase may be part of a lytic system that enables the bacteria to use living hyphae rather than chitin as the actual growth substrate, since chitin is an important constituent of most fungal cell walls. Lysis of living fungal hyphae

Wietse De Boer; Paulien J. A. Klein Gunnewiek; Petra Lafeber; Jaap D. Janse; Bendien E. Spit; Jan W. Woldendorp

1998-01-01

386

Properties of unsaturated weathered granitic soils with varying clay contents  

Microsoft Academic Search

For analyzing stabilities of soil slopes, banks and dams, engineering properties of dry or saturated soils are commonly applied. However, analysis and final designs adopting the partially-saturated or unsaturated soil parameters are steadily increasing. In this study, experiments on the soil water characteristic curve(SWCC) were performed to investigate the characteristics of unsaturated granitic soils with varying clay contents. Weathered granitic

D. Kim; G. Kim; H. Baek

2009-01-01

387

ESTIMATING THE WATER RETENTION CURVE FROM SOIL PROPERTIES: COMPARISON OF LINEAR, NONLINEAR AND CONCOMITANT VARIABLE METHODS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The unsaturated soil hydraulic functions involving the soil-water retention curve (SWRC) and the hydraulic conductivity provide useful integrated indices of soil quality. Existing and newly devised methods were used to formulate pedotransfer functions (PTFs) that predict the SWRC from readily avail...

388

Quantification of soil shrinkage in 2D by digital image processing of soil surface  

Microsoft Academic Search

Knowledge of soil shrinkage behavior is needed to improve the understanding and prediction of changes of unsaturated hydraulic properties in non-rigid soils. The heterogeneity and interaction of horizontal and vertical soil shrinkages that produce soil cracks and associated soil subsidence require additional quantification. Vertical shrinkage can be calculated easily by soil height with vernier caliper. However, a quantitative and feasible

X. Peng; R. Horn; S. Peth; A. Smucker

2006-01-01

389

Effect of root refuse of liquorice on different characteristics of soils from southern regions of Iran. III. Structure and hydraulic conductivity of soils under saline sodic conditions  

Microsoft Academic Search

Population increase and increasing demand for food have extended agriculture to troublesome lands with different problems, e.g., salinity and deficiency of organic matter. Although, even the application of a little amount of organic matter may have great effects in improving microbial, chemical, and physical properties of soil, but organic matter management in all soils, especially saline–sodic soils is difficult, and

M. Sameni; A. Tajabadi Pour

2001-01-01

390

Quantifying Soil Variability in GIS Applications: II Spatial Distribution of Soil Properties  

Microsoft Academic Search

Application of Geographical Information Systems (GIS) to environmental problems requires a spatial delineation of soil properties and some a priori knowledge of their variability. In the U.S.A. estimated soil properties are available from soil surveys published by the National Cooperative Soil Survey. However, information on the extent and nature of their variability is generally lacking. To remedy the situation, variability

A. S. Rogowski

1996-01-01

391

Fractional flow dimensions and hydraulic properties of a fracture-zone aquifer, Leppävirta, Finland  

Microsoft Academic Search

In order to characterize the hydraulic properties of an aquifer in Finland comprising two subvertical fracture zones, observation-well\\u000a responses were matched with generalized radial flow (GRF) type curves. The responses in six wells out of seven are consistent\\u000a with the GRF model. The fractional flow dimensions (1–1.2 and 1.5) were determined by regression analysis of straight-line\\u000a slopes and type-curve matching.

J. Leveinen; E. Rönkä; J. Tikkanen; E. Karro

1998-01-01

392

Prototype Database and User's Guide of Saturated Zone Hydraulic Properties forthe Hanford Site  

SciTech Connect

Predicting the movement of contaminants in groundwater beneath the Hanford Site is important for both understanding the impacts of these contaminants and for planning effective cleanup activities. These predictions are based on knowledge of the distribution of hydraulic properties within the aquifers underlying the Hanford Site. The Characterization of Systems (CoS) Task, under the Groundwater/Vadose Integration Project, is responsible for establishing a consistent set of data, parameters, and conceptual models to support estimates contaminant migration and impact.

Thorne, Paul D.; Newcomer, Darrell R.

2002-09-01

393

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

Microsoft Academic Search

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

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

2010-01-01

394

In-situ oxidation of trichloroethene by permanganate: effects on porous medium hydraulic properties  

Microsoft Academic Search

In-situ oxidation of dense nonaqueous-phase liquids (DNAPLs) by strong oxidants such as potassium permanganate (KMnO4) has been proposed as a possible DNAPL remediation strategy. In this study, we investigated the effects of in-situ trichloroethene (TCE) oxidation by KMnO4 on porous medium hydraulic properties. In particular, we wanted to determine the overall effects of concurrent solid phase (MnO2) precipitation, gas (CO2)

M. H. Schroth; M. Oostrom; T. W. Wietsma; J. D. Istok

2001-01-01

395

Digital Soil Mapping of Soil Properties in Honduras Using Readily Available Biophysical Datasets and Gaussian Processes  

Microsoft Academic Search

Creating detailed soil maps is an expensive and time consuming task that most developing nations cannot afford. In recent years, there has been a significant shift towards digital representation of soil maps and environmental variables and the associated activity of predictive soil mapping, where statistical analysis is used to create predictive models of soil properties. Predictive soil mapping requires less

Juan Pablo Gonzalez; Andy Jarvis; Simon E. Cook; Thomas Oberth; Mauricio Rincon-Romero; J. Andrew Bagnell; M. Bernardine

2008-01-01

396

Numerical evaluation of effective unsaturated hydraulic properties for fractured rocks  

SciTech Connect

To represent a heterogeneous unsaturated fractured rock by its homogeneous equivalent, Monte Carlo simulations are used to obtain upscaled (effective) flow properties. In this study, we present a numerical procedure for upscaling the van Genuchten parameters of unsaturated fractured rocks by conducting Monte Carlo simulations of the unsaturated flow in a domain under gravity-dominated regime. The simulation domain can be chosen as the scale of block size in the field-scale modeling. The effective conductivity is computed from the steady-state flux at the lower boundary and plotted as a function of the averaging pressure head or saturation over the domain. The scatter plot is then fitted using van Genuchten model and three parameters, i.e., the saturated conductivity K{sub s}, the air-entry parameter {alpha}, the pore-size distribution parameter n, corresponding to this model are considered as the effective K{sub s}, effective {alpha}, and effective n, respectively.

Lu, Zhiming [Los Alamos National Laboratory; Kwicklis, Edward M [Los Alamos National Laboratory

2009-01-01

397

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

398

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

PubMed

*Hydraulic redistribution (HR) of water via roots from moist to drier portions of the soil occurs in many ecosystems, potentially influencing both water use and carbon assimilation. *By measuring soil water content, sap flow and eddy covariance, we investigated the temporal variability of HR in a loblolly pine (Pinus taeda) plantation during months of normal and below-normal precipitation, and examined its effects on tree transpiration, ecosystem water use and carbon exchange. *The occurrence of HR was explained by courses of reverse flow through roots. As the drought progressed, HR maintained soil moisture above 0.15 cm(3) cm(-3) and increased transpiration by 30-50%. HR accounted for 15-25% of measured total site water depletion seasonally, peaking at 1.05 mm d(-1). The understory species depended on water redistributed by the deep-rooted overstory pine trees for their early summer water supply. Modeling carbon flux showed that in the absence of HR, gross ecosystem productivity and net ecosystem exchange could be reduced by 750 and 400 g C m(-2) yr(-1), respectively. *Hydraulic redistribution mitigated the effects of soil drying on understory and stand evapotranspiration and had important implications for net primary productivity by maintaining this whole ecosystem as a carbon sink. PMID:20406402

Domec, Jean-Christophe; King, John S; Noormets, Asko; Treasure, Emrys; Gavazzi, Michael J; Sun, Ge; McNulty, Steven G

2010-04-06

399

A Modified Mualem–van Genuchten Formulation for Improved Description of the Hydraulic Conductivity Near Saturation  

Microsoft Academic Search

The unsaturated soil hydraulic properties are often described using Mualem-van Genuchten (MVG) type analytical functions. Recent studies suggest several shortcomings of these functions near satura- tion, notably the lack of second-order continuity of the soil water retention function at saturation and the inability of the hydraulic conductivity function to account for macroporosity. We present a modified MVG formulation that improves

Marcel G. Schaap; Martinus Th. van Genuchten

2006-01-01

400

Measuring Hydraulic Conductivity to Wilting Point Using Polymer Tensiometers in an Evaporation Experiment  

Microsoft Academic Search

The polymer tensiometer is a novel instrument to measure soil water pressure heads from saturation to permanent wilting conditions. We used tensiometers of this type in an experiment to determine the hydraulic properties of evaporating soil samples in the laboratory. Relative errors in the hydraulic conductivity function in the wet part were high due to the relatively low accuracy of

A. Durigon; H. P. A. Gooren; Lier van Q. D; K. Metselaar

2011-01-01

401

Biological properties of soils on mine tips  

NASA Astrophysics Data System (ADS)

The biological properties of soils forming on coalmine spoils composed of loose non-toxic rocks were studied. In ten years of observation, fungal biomass in the studied soils increased by 6 times; the population density of the main groups of bacteria, by 3-7 times, and the respiration intensity, by 5-6 times. The biochemical activity of the soils increased significantly; in particular, the enzymatic activity (especially, the hydrolase activity) increased by 3-8 times, and the processes of cellulose destruction and accumulation of ninhydrinpositive products intensified. The obtained results attest to colonization of the substrate by microorganisms and the development of microbial cenoses. This process is particularly active upon application of phytoameliorants.

Naprasnikova, E. V.

2008-12-01

402

Field Measurement of Saturated Hydraulic Conductivity at the Hillslope Scale under different Soil Series and Management Practices  

NASA Astrophysics Data System (ADS)

Heterogeneity of saturated hydraulic conductivity (Ksat) was investigated at the hillslope scale in the South Amana Subwatershed (SAS), IA. Three fields of different soil series, and management practices (tilled, no-till, CRP) were examined at the SAS. Ksat was measured using 30 semi-automated double ring infiltrometer. Soil cores were also collected in the vicinity of the Ksat measurements via a truck-mounted Giddings Probe. Core sample analysis suggests that the spatial variability in Ksat very much reflects the overall soil texture variability found in the tested fields. The spatial variability of Ksat was log-normally distributed, which closely follows the distribution of the surface microroughness. Ksat varied over 3-orders of magnitude within the tested fields. The high sensitivity of Ksat was a good index to identify soil heterogeneity. Comparison between the published soil maps and observed soil series of the collected cores shows that erosion to varying degrees has occurred along the hillslope. Along the sides of the hillslope as we move downhill, the loam layer was found much deeper than along the centerline of the hillslope. This finding was indicative that significant erosion has occurred along the centerline of the hillslope. An outcome of the severe erosion was that the soil texture differed between the centerline and the sides. This different texture was found to affect Ksat at similar slope positions and land cover.

Elhakeem, M.; Chang, Y.; Wilson, C. G.; Papanicolaou, T.

2009-12-01

403

Do stone bunds affect soil physical properties? - A case study in northern Ethiopia  

NASA Astrophysics Data System (ADS)

Central issue of rain fed agriculture systems in the Ethiopian highlands is to store rain water in the soil during the rainy season (June to September). The aim is to maximize plant available water and to reduce surface runoff and soil erosion. Stone bunds are a common practice for soil and water conservation, influencing the translation processes of surface runoff. However, changes in surface hydrology affect the temporal and spatial properties of soil physical parameters. The objective of this research is to find a relationship between the spatial distribution of soil properties and the location of the stone bunds, but also to monitor the temporal behavior of those soil parameters, to better understand the impact of stone bunds on soil water movement. The research area is located in the Gumara Watershed, Maksegnit in Northern Ethiopia. There two representative transects were selected: One transect crosses three fields with conservation measures applied perpendicular to the stone bunds at a length of approximately 71 m. The second transect crosses a similar hill slope without conservation structures at a length of 55 m. During the rainy season in 2012 soil physical properties were monitored in specific spatial and temporal intervals. The measurements included bulk density, soil texture and volumetric water content. Tension infiltrometer tests were conducted to determine saturated and near saturated hydraulic conductivity for areas near stone bunds and the center of the fields on one hand, but also to derive van Genuchten parameters for those points inversely with Hydrus 2D. Slope steepness and stone cover along the transects were assessed, using survey and photogrammetric analysis. Preliminary results show an increase in the water content of topsoils within a range of approximately 2 m above the stone bunds but only random fluctuations in the field without conservation measures. At depths greater than 20 cm no significant differences in water content were found. Bulk density shows lower values in the areas above the stone bunds where sedimentation takes place. Slope steepness and stone cover also decrease in a range of a few meters above the stone bunds that also indicates sedimentation processes. Further analysis with consideration of the spatial and temporal distribution of the measurements may show influences on soil physical properties but also relationships between soil parameters (cross correlation). Showing a cyclic behavior of soil physical properties at the same spatial scale as the conservation measurements are placed may indicate a relationship between soil conditions and man-made conservation structures. Significant temporal changes of specific soil physical properties over the rainy season may allow a deeper insight in the impact of conservative measures on soil water balance.

Schürz, Christoph; Schwen, Andreas; Strohmeier, Stefan; Klik, Andreas

2013-04-01

404

Rheological Properties of Wet Soils and Clays under Steady and Oscillatory Stresses  

Microsoft Academic Search

In engineering soil mechanics, it is very common to determine stress-strain relationship of soils (under equi- Tilled agricultural soils are in a constant state of change induced librium conditions) empirically from simultaneous mea- by variations in soil strength due to wetting and drying and compaction by farm implements. Changes in soil structure affect many hydraulic surements of stress and strain,

Teamrat A. Ghezzehei; Dani

2001-01-01

405

Spatial Characteristics of Claypan Soil Properties in an Agricultural Field  

Microsoft Academic Search

Spatial variability in soil properties has long been observed within uniformly managed fields. Understanding the spatial characteristics of soil properties would be helpful in understanding soil-landscape rela- tionships and in the development of site-specific management. The primary objective of this research was to quantify the spatial char- acteristics of claypan soil properties for a 4-ha agricultural field located in north-central

W. K. Jung; N. R. Kitchen; K. A. Sudduth; S. H. Anderson

2006-01-01

406

Remote assessment of the degree of soil degradation from radiation properties of soils  

NASA Astrophysics Data System (ADS)

The effect of the water and salt contents, the soil texture, and the groundwater level on the radiation properties of soils was studied. A methodology was developed for the remote assessment of the degree of soil degradation on the basis of measuring the brightness temperature and emissivity of soils in the microwave region. Criteria based on the remote measurements of radiation parameters of soils for recording changes in the water-physical and other properties of soils, which are necessary for detecting degradation processes at early stages, were substantiated. For the remote assessment of soil degradation, it was proposed to analyze trends in changes with time concerning the emissivities of unfrozen soils occurring at a positive temperature (depending on the soil water content and the groundwater level), the emissivities of frozen nonsaline soils (depending on the soil texture and thermodynamic temperature), and the brightness temperature (depending on the soil salinity and thermodynamic temperature).

Romanov, A. N.

2009-03-01

407

Modeling as a tool for management of saline soils and irrigation waters  

Technology Transfer Automated Retrieval System (TEKTRAN)

Optimal management of saline soils and irrigation waters requires consideration of many interrelated factors including, climate, water applications and timing, water flow, plant water uptake, soil chemical reactions, plant response to salinity and solution composition, soil hydraulic properties and ...

408

Estimated hydraulic properties for the surficial-and bedrock-aquifer system, Meddybemps, Maine  

USGS Publications Warehouse

Analytical and numerical-modeling methods were used to estimate hydraulic properties of the aquifer system underlying the Eastern Surplus Company Superfund Site in Meddybemps, Maine. Estimates of hydraulic properties are needed to evaluate pathways for contaminants in ground water and to support evaluation and selection of remediation measures for contaminated ground water at this site. The hydraulic conductivity of surficial materials, determined from specific-capacity tests, ranges from 17 to 78 feet per day for wells completed in coarse-grained glaciomarine sediments, and from about 0.1 to 1.Ofoot per day for wells completed in till. The transmissivity of fractured bedrock determined from specific-capacity tests and aquifer tests in wells completed in less than 200 feet of bedrock ranges from about 0.09 to 130 feet squared per day. Relatively high values of transmissivity at the south end of the study area appear to be associated with a high-angle fracture or fracture zone that hydraulically connects two wells completed in bedrock. Transmissivities at six low-yielding (less than 0.5 gallon per minute) wells, which appear to lie within a poorly transmissive block of the bedrock, are consistently in a range of about 0.09 to 0.5 foot squared per day. The estimates of hydraulic conductivity and transmissivity in the southern half of the study area are supported by results of steady-state calibration of a numerical model and simulation of a 24-hour pumping test at a well completed in bedrock. Hydraulic conductivity values for the surficial aquifer used in the model were 30 feet per day for coarse-grained glaciomarine sediments, 0.001 to 0.01 foot per day for fine-grained glaciomarine sediments, and 0.1 to 0.5 foot per day for till. As part of model calibration, a relatively transmissive zone in the surficial aquifer was extended beyond the hypothesized extent of coarse-grained sediments eastward to the Dennys River. Hydraulic conductivity values used for bedrock in the model ranged from 3x10-4 to 1.5 feet per day. The highest values were in the fracture zone that hydraulically connects two wells and apparently extends to the Dennys River. The transmissivity of bedrock used in the model ranged from 0.03 to 150 feet squared per day, with the majority of the bedrock transmissivities set at 0.3 foot squared per day. Numerical modeling results indicated that a very low ratio of vertical hydraulic conductivity to thickness (1x10-9 days-l) was required to simulate a persistent cone of depression near a residential well that lies in the previously identified poorly transmissive block of bedrock.

Lyford, Forest P.; Garabedian, Stephen P.; Hansen, Bruce P.

1999-01-01

409

Hydraulic and mechanical properties of young Norway spruce clones related to growth and wood structure.  

PubMed

Stem segments of eight five-year-old Norway spruce (Picea abies (L.) Karst.) clones differing in growth characteristics were tested for maximum specific hydraulic conductivity (k(s100)), vulnerability to cavitation and behavior under mechanical stress. The vulnerability of the clones to cavitation was assessed by measuring the applied air pressure required to cause 12 and 50% loss of conductivity (Psi(12), Psi(50)) and the percent loss of conductivity at 4 MPa applied air pressure (PLC(4MPa)). The bending strength and stiffness and the axial compression strength and stiffness of the same stem segments were measured to characterize wood mechanical properties. Growth ring width, wood density, latewood percentage, lumen diameter, cell wall thickness, tracheid length and pit dimensions of earlywood cells, spiral grain and microfibril angles were examined to identify structure-function relationships. High k(s100) was strongly and positively related to spiral grain angle, which corresponded positively to tracheid length and pit dimensions. Spiral grain may reduce flow resistance of the bordered pits of the first earlywood tracheids, which are characterized by rounded tips and an equal distribution of pits along the entire length. Wood density was unrelated to hydraulic vulnerability parameters. Traits associated with higher hydraulic vulnerability were long tracheids, high latewood percentage and thick earlywood cell walls. The positive relationship between earlywood cell wall thickness and vulnerability to cavitation suggest that air seeding through the margo of bordered pits may occur in earlywood. There was a positive phenotypic and genotypic relationship between k(s100) and PLC(4MPa), and both parameters were positively related to tree growth rate. Variability in mechanical properties depended mostly on wood density, but also on the amount of compression wood. Accordingly, hydraulic conductivity and mechanical strength or stiffness showed no tradeoff. PMID:17472942

Rosner, Sabine; Klein, Andrea; Müller, Ulrich; Karlsson, Bo

2007-08-01

410

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

USGS Publications Warehouse

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 In (a/Kb tan B), where In is the Naperian logarithm, "a' is the area drained per unit contour, K is the saturated hydraulic conductivity, b is the total depth, and tan B is the slope. Using digital elevation and soil survey data, the In (a/Kb tan B) distribution for 145 catchments was calculated. Indices of flow path partitioning and soil contact time were derived from the In (a/Kb tan B) distributions and compared to meas