Modeling on the high-concentration water intrusion in Hanting-Changyi area, China

In the Hanting-Changyi area, China, due to the long-term hydrodynamic dispersion, there exist brackish water (TDS 1-10 g/l) and salt water (TDS>10-100 g/l) in the area between the brine (TDS>100 g/l) and the fresh water (TDS<1 g/l), and there is an unrest equilibrium among them. Excessive pumping of the fresh groundwater will destroy.the equilibrium and lead to the landward advancing of such types of groundwater. In the enriching process, some chemical reaction occurred, such as the cations exchange of Ca2+-Na+ in the contraction zone between the marine deposition and the land deposition, the inverse cations exchange of Na+-Ca2+ in the transition zone between the brine and the fresh water. Therefore, all the models for sea water intrusion cannot be used to simulate the high-concentration water intrusion in the study area. We develop a three-dimensional mathematical model for the high-concentration water intrusion in a phreatic aquifer. The model considers not only the existence of transition zone and great discharge pumping wells, the effect of variable density and viscosity on fluid flow, the effect of precipitation infiltration and phreatic surface fluctuation in the process of the high-concentration water intrusion, but also the cations exchange of Ca2+-Na+, the inverse cations exchange of Na+ (2+)-Ca between water and soil. It was successfully applied to simulate the high-concentration water intrusion problem in the Hanting-Changyi area, China. The simulated values agree very well with the field data.