Inverse modeling of the recharge of shallow water tables in irrigation districts

Abstract

Shallow water tables, deficient root zone aeration, and progressive soil salinization have stemmed from irrigation water application. Subsurface land drainage has represented an alternative for soil reclamation; however, it is very important to know the recharge rate of the water table in order to design an adequate field drainage system. The recharge can be estimated through different field methods. or by considering the Boussinesq equation of water dynamics as an inverse problem derived from hydraulic head, storage capacity and saturated hydraulic conductivity. The inverse recharge modeling was applied in Irrigation District 076, Valle del Carrizo, in Sinaloa, Mexico. A potential semivariogram-based kriging method was used to interpolate the hydraulic head and subsequently, to calculate the derivatives. Both the hydraulic conductivity and storage capacity were interpolated by using an exponential semivariogram. Tliese semivariograms adequately represent the experimentaldata. The results show that the flux divergence term in the Boussinesq equation does not have a significant effect on recharge estimation. Recharge estimation fundamentally depends on the precise determinationo f the storage capacity.