TR-30 : Study of soil moisture movement during rainfall by Green and Ampt equation and comparison of the study by numerical model

Abstract

Soil moisture movement during a rainfall event has been studied using Green and Ampt approximate solution of infiltration. The soil moisture movement has also been predicted by solving Richard's equation. The solution obtained by Green and Ampt approximate has been compared with the numerical solution of Richard's equation.

Green and Ampt assume that water moves like a piston. Thus the soil behind the moving front is assumed to be completely saturated and the soil infront of the front is at the uniform initial soil moisture. This assumption leads to the fact that velocity of water at a particular time is invariant with depth.

In reality the soil moisture distribution with depth will be gradual. The velocity of soil water at different depth have been obtained using the numerical solution and compared with that corresponding to Green and Ampt equation.

Numerical solution is used to study the soil moisture movement taking into consideration the presence of capillary zone above the water table. The positions of saturation front at a particular time computed by both the methods have been compared.