A nested optimization model for sustainable groundwater development in South Texas

Sustainable groundwater management, balancing the competing economic and ecological objectives using decision support tools is the focus of this thesis. In this study the major water demand centers are identified using Texas Water Development Board (TWDB) Regional Water Planning Group data and potential supply areas are identified using GIS based multi-criteria decision making analysis. A simulation-optimization technique was applied to estimate the amount of groundwater available at each supply center. The Groundwater Availability Model (GAM) developed by the Texas Water Development Board (TWDB) was used as the simulation model and the constraints on the optimization model included: restrictions on drawdown at the well and in the vicinity as well as ensuring sufficient freshwater inflows into surface water bodies including the coast and other policy considerations. Using the estimated groundwater availability as the basis, a transportation-type optimization model was then developed. Considerations for optimization here included the distance over which the water was to be transported to as well as the gradient over which the water was to be moved along with satisfying pertinent mass balances. The three-pronged methodology developed here provides a sound basis for decision makers and regional planners to identify potential ways to meet water deficits without compromising on the ecological and environmental issues and as such promotes sustainable planning in this semi-arid region.