Shallow water table dynamics in irrigation districts.

摘要

A numerical model for water transfer simulation in shallow water tables is presented. The model is based on a differential equation resulting from the integration of Richards' equation in the vertical direction. The numerical scheme to solve this equation is obtained from its integration using a finite element approach in space, and from the integration using a finite difference-centred-scheme approach in time. The solution domain used in the construction, calibration, and application of the modelwas an irrigation district in the northern part of the State of Sinaloa, Mexico. The application of the model was carried out in two stages: the first is an inverse simulation to estimate the recharge flow for several periods of time, and the second is adirect simulation of the response of the system under different scenarios. It was concluded that the model is very useful for planning purposes. Additionally, a study on spatial variability of shallow water-table fluctuation in the domain study is presented, where semivariograms of this variate can be adequately represented by a potential theoretical semivariogram with an exponent beta=1.5, and this is uniquely related to the fractal dimension (D?.25) for shallow water-table surfaces.