Modeling Flow and Transport in Drainage Areas with Shallow Ground Water

Abstract

A new modified linked approach is introduced to solve the governing partial differential equations for subsurface flow and salt transport by finite difference. It combines the attractive features of the standard linked and continuous (composite) modeling approaches. The standard linked approach can be adopted to model irrigation-drainage systems that are traditionally based on a purely agricultural objective of maintaining crop productivity despite the presence of a saline shallow ground-water table. With current concerns on the water quality of agricultural drainage, a more rigorous modeling approach (i.e., continuous approach) is required, however, at the expense of a large increase in the computational requirement. By using one- (1D), two- (2D), and three-dimensional (3D) flow and salt transport problems, it is shown that the modified linked approach efficiently satisfies current modeling requirements of both crop productivity and water quality protection. Results of applying the model to estimate the effectiveness of the drains to intercept soil water from shallow layers (<2 m deep) as affected by drain spacing, drain depth, surface recharge, and depth to impermeable layer are presented.