Water table draw down during drainage with evaporation/evapotranspiration

Abstract

Groundwater table behavior in drained lands in addition to tile flow depends upon several other factors. Evaporation/evapotranspiration (E/ET) from the shallow water table is one of them. The Boussinesq equation for non-steady state groundwater flow with variable drainable porosity was suitably modified by incorporating a non-linear function simulating E/ET from the shallow water table. The modified equation was solved numerically for predicting the groundwater table behavior with respect to space and time. Column studies and soil tank model experiments were conducted to find out the functional relationship between the evaporation rate and water table height as well as for determination of other parameters required in the mathematical model. The water table fluctuation data were recorded in the soil tank model when both the process of evaporation and drainage were operative. The result of this study revealed that groundwater table behavior, predicted by modified Boussinesq equation was quite comparable with corresponding observed data. The quality of the predictions were much better compared to the conventional approach in which drainable porosity is assumed constant and the process of E/ET is neglected.