Theme 2-11-Evolution of water table with subsurface drainage for variable recharge and constant ET

Abstract

Subsurface drainage plays an important role in lowering the water table in case of excess irrigation and recharge due to rainfall. The shallow groundwater table affected by the recharge in the presence of drainage is required for the design of subsurface drains and management of crop practices. Another important factor affecting the shallow groundwater table is the evapotranspiration or evaporation from groundwater table. Many analytical studies have been reported in the literature for the evolution of water table with subsurface drainage. In most of the studies, constant recharge has been considered. Only in few studies variable recharge has been considered but without considering evapotranspiration (ET).

In the present study, the analytical solution has been proposed for the combination of variable recharge functions and constant rate evapotranspiration. Linear and exponential variation of recharge with time have been considered. For obtaining the solution the Boussinesq equation has been linearized by suitable substitution and the approaches applicable for the linear system have been adopted. The solutions, thus obtained have been shown to converge to the existing solution under specific conditions. The results have been presented to show the effects of variation in recharge and ET on the evolution of the water table.