delta-Form approximating problem for a conjunctive water resource management model

A nonlinear coupled simulation and optimization model is formulated to find the optimal operating policies with a minimal cost for the conjunctive man agement of hydraulically interacting surface and ground water supplies. The term representing the pumpage cost in the objective function of the manage ment model causes nonlinearity that cannot be put in a quadratic form as in the traditional approach, since drawdown in that term is a function of wel l pumpage and other parameters. To eliminate the nonlinearity, F-form appro ximating model is formulated with a particular emphasis on the concave func tion of the transformed objective function. The original problem in a nonli near form is solved by coupling the solver with a random number generator t o provide the model with a different initial guess each time. However, the delta-form approximating problem is formulated as a linear mixed integer pr ogramming model. Optimal operating policies and the operation costs obtaine d from both models are found to be in good agreement. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.