Abstract |
The objectives were (1) to determine the principal factors affecting deep seepage in the Piedmont, and (2) to develop relationships to express percolation in terms of measurable physical quantities. A field experiment was conducted which included measurements of precipitation, surface runoff, interflow, soil moisture to a depth of 32 feet, and water table levels. The high-clay content, B2t horizon was found to act as a restricting layer for deep seepage. However, considerable quantities of deep seepage occur principally during the winter and early spring when precipitation is normally heavy and evapotranspiration low. Time lags, between the occurrence of excess moisture near the soil surface and a resulting effect on the water table, varied from 5 1/2 months for an initially low-moisture profile, down to only 4 weeks for an initially high-moisture profile. An empirical model for predicting deep seepage was developed and tested and a stochastic model of soil moisture in the profile is under development. Graphs are presented showing measured soil moisture profiles at different times under both wetting and draining conditions. Graphs and tables also show moisture excess predicted by the empirical model, and the predicted water table hydrograph compared to that observed. (Author) |