Theme 5-9-Simulation of soil moisture movement in a forested watershed.

Abstract

Prediction of soil moisture retention and movement is very important for irrigation scheduling, crop planning, runoff estimation and drought monitoring. Application of numerical techniques provides estimates for different hydrologic variables including soil moisture. Soil moisture in the root zone is best predicted by the simulation models which consider withdrawal of water from the root zone. The changes in soil water content is predicted generally by one-dimensional continuity equation coupled with volumetric root sink term. The present study has been carried out to simulate soil moisture, evapotranspiration, runoff and drainage in Barchi forested watershed. Hydrologic parameters such as infiltration, hydraulic conductivity and soil moisture retention characteristics under different types of forest covers were determined by using Disc Permeameter and Guelph Permeameters and pressure plate apparatus. A simulation model, SWIM (Soil Water Infiltration and Movement) developed by CSIRO, division of Soils, Australia) was applied. It deals with the numerical solution of one-dimensional Richard's equation based on the assumption that the soil column may be vertically inhomogeneous and horizontally uniform. Predicted soil moisture profiles for post-monsoon and pre-monsoon period closely follow the trend of observed moisture profile in the watershed. Runoff, evaporation and drainage were also estimated. The results are quite comparable with earlier studies.