KWRRI Research Reports


A laboratory system was fabricated to measure infiltration and runoff from spoil and soil profiles constructed in rectangular bins. Construction, calibration and operation of a rainfall simulator is discussed and instrumentation used to measure transient infiltration and transmittance of water through experimental profiles is described.

Spoil and soil materials from surface mines in Eastern and Western Kentucky were transported to the laboratory and used in constructing experimental profiles in rectangular bins (0.91 x 1.83 x 1.07 m). An extensive series of infiltration experiments were conducted utilizing a rainfall simulator and soil moisture monitoring instrumentation. A dual probe gamma density gauge was used to measure moisture content and tensiometers were used to measure soil matric suction. Initial moisture content, bulk density and rainfall rate were varied and respective responses of infiltration characteristics determined.

Extremely low infiltration rates in Western Kentucky spoil material was attributed to relatively high bulk densities and well-graded particle constituency. Conversely, extremely high infiltration rates were observed for Eastern Kentucky shale material even at very high bulk densities. The sandstone material, however, exhibited infiltration rates of the same order of magnitude as that of Western Kentucky spoil material.

Soil water characteristic curves were developed using the Brooks-Corey and Gardner procedures, based upon desortpion tensiometer data. Unsaturated hydraulic conductivity values were determined using the "plane of zero flux" procedure and compared with predictions resulting from models described by Campbell, Burdine and Mualem for situations involving "reconstructed" soil and spoil materials. There was generally good agreement between the models and "plane of zero flux" results, and excellent agreement with Campbell's predictions.

The infiltration process was modeled with the SCS curve number method, a modified form of Holtan's equation, the Green-Ampt model and Richard's equation. SCS curve numbers were determined by fitting the method to the observed results. Richards' equation gave very good estimates of the infiltration process through the spoil profiles, but was only slightly better than the Green-Ampt model. None .of the models worked well for the profiles where macropore flow occurred through a two layer topsoil over spoil system.

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Funding Information

The work upon which this report is based was supported in part by funds provided by the United State Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. Public Law 95-467.