Groundwater flow and solute transport in the industrial well fields of the Texcoco saline aquifer system near Mexico City

Abstract

The hydraulic behavior of the Texcoco saline aquifer system near Mexico City is investigated through the evaluation of historical data, field studies, and numerical analysis of groundwater flow and solute transport within a large well field which is extracting the saline water for industrial purposes. The two thin aquifers under production in this area are bounded by highly compressible aquitards which supply tremendous volumes of water to the aquifers through leakage. A quasi three-dimensional integrodifferential equation scheme is used for the Flow modelling and is solved numerically with a triangular finite element scheme. The solute mass transport model is based on the method of characteristics combined with a particle tracking scheme. The models are accurately calibrated to piezometric field measurements and concentration distribution data from the production wells. Piezometric nests installed in the surficial cJay aquitard indicate that in the heavily pumped areas, infiltrating rainfall is diJuting the pore water concentrations in the aquitard which may account for declining concentrations in the production wells which have been recently observed. Analysis of the field data also indica tes that the surficíal aquitard is fractured and that the fracture network may play an important role in the movement of solutes in the aquitard. The models are currently being used to investigate alternative management strategies to optimize production from the industrial well field.