Green-Ampt Model for Layered Soils with Nonuniform Initial Water Content Under Unsteady Infiltration.

The Green-Ampt equation is often used to estimate infiltration in hydrologic modeling. Only a few of the currently used simulation models, however, can simulate infiltration into a heterogeneous soil with nonuniform initial soil water content by the Green-Ampt equation during nonsteady rainfall. In this study, we derived an infiltration model for layered soils under nonsteady infiltration based on the Green-Ampt method (Green-Ampt for Layered Soils, or GALS). In the GALS model, a formula for estimating average suction (5) was derived to include initial soil water effect, and the soil profile was divided into several layers to consider both soil texture and initial soil moisture effects on infiltration. The new model can predict infiltration capacity, ponding time, and cumulative infiltration. Three infiltration experiments, steady-state infiltration into a layered soil with nonuniform initial soil water content, nonsteady infiltration into a layered soil with uniform soil water content; and nonsteady-state infiltration into a layered soil with nonuniform soil water content, were conducted for model testing. Comparison showed that the GALS model was in good agreement with another Green-Ampt-based model and the measured data. [ABSTRACT FROM AUTHOR]