Estimation Of Groundwater Recharge By Soil Moisture Modelling

摘要

In this paper, groundwater recharge is estimated using soil moisture modelling of unsaturated zone, which considers the subsurface flow component along with the evapotranspiration from the crop or actual evaporation from soil and vegetative covers. The subsurface flow component is represented using one-dimensional Richards equation with root water uptake as the evapotranspiration from crop. The root water uptake is calculated considering the crop coefficient, potential evaporation, and soil moisture available at different depth and the distribution of the root density along the root zone depth. Conceptualizing the unsaturated zone depth as a vertical soil column comprised of number of cells, in which flow calculated using Darcy's law for the unsaturated flow from one cell to another takes place in accordance with the gradient of the suction head. The unsaturated hydraulic conductivity in such case is computed at the cell face. A strongly implicit finite-difference procedure is used to solve the subsurface flow equation with the suitable initial and boundary conditions. The model is used to simulate a single soil column having sandy loam soil in Jammu (J & K). Groundwater recharge is estimated for one complete crop year with daily rainfall and pan evaporation data of Jammu. Evapotranspiration accounted for 36 % of the total water applied (irrigation plus rainfall) whereas 12 % contributed to wards change in soil moisture storage and remaining 52 % is the recharge below the root zone.