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Infiltration Tests (infiltration + test)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Determining soil saturated hydraulic conductivity and sorptivity from single ring infiltration tests

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007
J. Touma
Summary The difference between the cumulative infiltration occurring during three-dimensional axisymmetric and one-dimensional vertical flow is a linear function of time. The slope of this line is a function of the source radius, initial and final volumetric soil water contents and the soil sorptivity. This allows the determination of the sorptivity and saturated conductivity of the soil from data of axisymmetric flow in a single ring of small diameter under negligible head of water. The method is based on the optimization of the sorptivity and saturated conductivity on the one-dimensional vertical cumulative infiltration inferred from axisymmetric flow data. To examine the reliability of the method to determine these parameters, numerical three- and one-dimensional data are generated on soils with known hydrologic properties from the literature. The linearity versus time of the difference of the two types of flow is verified. Several physically based expressions for the vertical cumulative infiltration as a function of time are considered. The optimized values of the sorptivity and saturated conductivity are compared to the their real known values. Despite the large errors on the optimized parameters, namely the saturated conductivity, the error on the vertical predicted cumulative infiltration is limited to 10%. This makes possible the application of this method on a large scale for hydrological modelling purposes. [source]

Analysis of Transient Data from Infiltrometer Tests in Fine-Grained Soils

GROUND WATER, Issue 3 2000
Dominique Guyonnet
Data collected during ring infiltrometer tests are often analyzed while assuming either that the effect of gravity is negligible (early-time, transient data) or that it is dominant (late-time, steady-state data). In this paper, an equation is proposed for inter-preting both early-time and late-time data measured during infiltration tests under falling head conditions. It is shown that the method used by previous authors for interpreting both early-time data is a special case of the proposed equation. The equation is applied to data collected during tests performed in fine-grained soils, and results are discussed. The analysis suggests that to assume a priori values of the soil sorptive number, as indicated in the literature for various soils, may in some cases lead to severely underes-timated values of the saturated hydraulic conductivity. Conversely, in low permeability soils, to assume steady-state gravity drainage may lead to order of magnitude overestimates of the saturated hydraulic conductivity. A dimensionless analysis provides characteristic times that correspond either to the duration of the log-log half slope displayed by early-time data or to the log-log unit slope characteristic of late-time data. [source]

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

HYDROLOGICAL PROCESSES, Issue 17 2010
E. Gonzalez-Sosa
Abstract The hydraulic properties of the topsoil control the partition of rainfall into infiltration and runoff at the soil surface. They must be characterized for distributed hydrological modelling. This study presents the results of a field campaign documenting topsoil hydraulic properties in a small French suburban catchment (7 km2) located near Lyon, France. Two types of infiltration tests were performed: single ring infiltration tests under positive head and tension-disk infiltration using a mini-disk. Both categories were processed using the BEST,Beerkan Estimation of Soil Transfer parameters,method to derive parameters describing the retention and hydraulic conductivity curves. Dry bulk density and particle size data were also sampled. Almost all the topsoils were found to belong to the sandy loam soil class. No significant differences in hydraulic properties were found in terms of pedologic units, but the results showed a high impact of land use on these properties. The lowest dry bulk density values were obtained in forested soils with the highest organic matter content. Permanent pasture soils showed intermediate values, whereas the highest values were encountered in cultivated lands. For saturated hydraulic conductivity, the highest values were found in broad-leaved forests and small woods. The complementary use of tension-disk and positive head infiltration tests highlighted a sharp increase of hydraulic conductivity between near saturation and saturated conditions, attributed to macroporosity effect. The ratio of median saturated hydraulic conductivity to median hydraulic conductivity at a pressure of , 20 mm of water was about 50. The study suggests that soil texture, such as used in most pedo-transfer functions, might not be sufficient to properly map the variability of soil hydraulic properties. Land use information should be considered in the parameterizations of topsoil within hydrological models to better represent in situ conditions, as illustrated in the paper. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Comparing the hydrology of grassed and cultivated catchments in the semi-arid Canadian prairies

HYDROLOGICAL PROCESSES, Issue 3 2003
G. van der Kamp
Abstract At the St Denis National Wildlife Area in the prairie region of southern Saskatchewan, Canada, water levels in wetlands have been monitored since 1968. In 1980 and 1983 a total of about one-third of the 4 km2 area was converted from cultivation to an undisturbed cover of brome grass. A few years after this conversion all the wetlands within the area of grass dried out; they have remained dry since, whereas wetlands in adjacent cultivated lands have held water as before. Field measurements show that introduction of undisturbed grass reduces water input to the wetlands mainly through a combination of efficient snow trapping and enhanced infiltration into frozen soil. In winter, the tall brome grass traps most of the snowfall, whereas in the cultivated fields more wind transport of snow occurs, especially for short stubble and fallow fields. Single-ring infiltration tests were conducted during snowmelt, while the soil was still frozen, and again in summer. The infiltrability of the frozen soil in the grassland is high enough to absorb most or all of the snowmelt, whereas in the cultivated fields the infiltration into the frozen soil is limited and significant runoff occurs. In summer, the infiltrability increases for the cultivated fields, but the grassland retains a much higher infiltrability than the cultivated land. The development of enhanced infiltrability takes several years after the conversion from cultivation to grass, and is likely due to the gradual development of macropores, such as root holes, desiccation cracks, and animal burrows. Copyright ©2002 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source]