In hydrologic studies, especially those that include dynamic unsaturated zone moisture modeling, data from published hydraulic property databases are often used in lieu of measured unsaturated hydraulic properties from the site of interest. Reliance on such databases has become increasingly common with the use of neural network models that yield hydraulic property parameter values for specific applications based on the values in databases. High quality data, including unsaturated hydraulic conductivity, are also desirable for use in theoretical and property-transfer model development and testing. Hydraulic properties from databases may be adequate in some applications, but not others. An obvious problem occurs when the available database has few or no data for samples that are closely related to the medium of interest. For example, when undisturbed field properties are needed, the available data may be from measurements on repacked material.
Samples are from diverse geographic, climatic, and geomorphic environments, and the data were originally generated for various research purposes including recharge estimation, simulation of variably saturated flow and transport, theoretical studies of porous media, and property transfer model development. Samples were from various depths, including many from below the root zone. Data include bulk density, particle density, particle-size distribution, saturated hydraulic conductivity, hydraulic conductivity as a function of water content, and water content as a function of matric potential. Also included are particle size statistics, Rossi-Nimmo(1994) water retnetion curve fit parameters, and paramters from power law fits to unsaturated hydraulic conductivity. Additional information includes sample location, collection method, sampling date, latitude, longitude, approximated elevation, depth to the water table, climatic regime, mean annual precipitation, geologic environment, layer character, and any other notable features
The figure (left) shows examples of hydraulic conductivity curves measured using the steady state centrifuge method (A), water retention curves measured with tensiometers (B) and particle size distributions measured with optical scattering (C).
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Kim Perkins.| National Research Program | USGS | Water Resources | UZ Flow Homepage |