An analytical solution of the boussinesq equation for subsurface drainage in the presence of evapotranspiration

A linearized form of the Boussinesq equation was solved analytically to predict water table fluctuations in subsurface-drained farmlands in the presence of evapotranspiration. It was assumed that the evapotranspiration rate decreases linearly with a decrease in water table height above the drains. The analytical solution was verified with the existing analytical and numerical solutions. There was a close match between the solutions. A few numerical examples are given to highlight the characteristics of the various parameters used in the analytical solution and to justify, the inclusion of evapotranspiration into drainage design procedures for semi-arid regions. It is shown that if field parameters, representative of a semi-arid region, are used, the drain spacing can be increased by 18 to 25% when evapotranspiration is taken into account.