Ground-water Subsidence Model: A Management Tool

A finite difference computer modeling system has been developed to predict future subsidence as a function of ground-water pumpage in Harris and Galveston Counties, Texas. Two previously developed models, one for ground water, the other for subsidence, were specifically calibrated for the area and linked through the common parameter of potentiometric surface elevation. The two pumped aquifers, Chicot and Evangeline, are modeled using a modified Trescott, three-dimensional flow model, while subsidence is calculated at 21 specific subsectors within the Harris-Galveston Coastal Subsidence District using a modification of Helm's one-dimensional Terzaghi-consolidation model. Both models have been calibrated against historical data. The predictions run to date indicate changing trends in the location of future subsidence-prone areas. The modeling system will allow the District to make rapid, reproducible, documented predictions of land subsidence resulting from anticipated future pumpage of ground water.