Goal programming models for determining freshwater inflows to estuaries

This paper presents two multiobjective models for the estuary-management problem based upon goal-programming procedures. The multiobjectives are the minimization of freshwater inflow into bays and estuaries and the maximization of commercial-fish harvest for five fish species. Salinity is expressed as a function of freshwater inflow in a nonlinear-regression equation, which is used as a constraint. Additional nonlinear constraints are the harvest-regression equations for the various species that express harvest as a function of the quantity of freshwater inflow. The goal programming model is a nonlinear-programming problem solved by using the general algebraic modeling system/modular in-core non-linear optimization system (GAMS/MINOS) programming code. Because of the uncertainty associated with the regression equations for salinity and harvest, a second formulation was developed in which the constraints are expressed in a chance-constrained formulation. The chance-constrained goal-programming model is solved by using the GRG2 programming code. The models for both formulations are applied to the Lavaca-Tres Palacios Estuary in Texas.