Analysis of bi-level drainage problem with sloping aquifer

In this research, an analytical solution has been developed to describe falling water table in a bi-level drainage system on a sloping aquifer. This is done by analytically solving (i.e., employing Laplace transform and its inverse) the one-dimensional linearized Boussinesq equation incorporating slope and depth-dependent evapotranspiration term along with appropriate initial and boundary conditions. The results are compared with the solutions reported by Upadhyaya and Chauhan (in Agric Water Manag 45:169–184, 2000)). Spacing between two bi-level drains and level drains has also been computed employing unsteady state drainage criteria (i.e., fall of 30 cm midpoint water level from initial water level near land surface within 2 days). It is concluded that there is a direct relation between spacing of two bi-level drains and rate of evapotranspiration as well as slope, whereas the relation of spacing is inverse with depth-dependent reduction factor.