Freshwater‐Inflow Need of Estuary Computed by Texas Estuarine MP Model

Abstract

The Texas Estuarine Mathematical Programming (TxEMP) model was developed as a tool to study the effect of freshwater inflow to the bays and estuaries in Texas and to help establish longterm objectives of maintaining and enhancing an ecologically healthy environment for the estuaries. The model is a nonlinear, stochastic, multiobjective mathematical programming model. It represents needs of the biological system through the use of salinity‐inflow regression equations and fishery‐harvest‐inflow regression equations. If quantitative information is available, nutrient and sediment requirements can be taken into account. Hydrological information is incorporated as the monthly lower bounds and upper bounds on inflows. Salinity constraints and fishery harvest constraints are treated as chance constraints. The objective function can be inflow minimization or maximization, fishery‐harvest maximization or minimization, maximization of satisfying the salinity constraint, or satisfying the fishery‐harvest constraint. A multiobjective approach is taken to resolving the estuarine management problem by presenting results as a performance curve that contains a series of solutions ranging from a minimum required inflow, maximum harvest solutions, and a maximum allowable inflow. This paper presents mathematical details of the TxEMP model and an actual application to determine the release policy from the upstream reservoirs to the Nueces Estuary.