Reliability in Multi-Objective Management of Saltwater Intrusion under Uncertainly of Hydraulic Conductivities.

Document Type : Research Studies

Author

Irrigation and Hydraulics Engineering Department, Faculty of Civil Engineering, El-Mansoura University, Mansoura, Egypt.

Abstract

Most optimization models for management of coastal aquifers have ignored the effects of uncertainty due to spatial variability of hydraulic conductivity. This research explicitly incorporates uncertainty, in the hydraulic properties of coastal aquifer, into a procedure for optimal management of multi objectives. The sharp interface philosophy is adopted to simulate dynamics of the freshwater flow. Finite element method (FEM) was applied on the linear formulation of Strack to simulate the hydraulic response of the studied aquifer under different suggested rates of pumping. The LU-decomposition method was exploited to inverse the conductance matrix, that significantly decreases the computation time. The constraint technique was applied to simplify, without any relaxation, the multi objective management problem to single objective management problem. Genetic a logarithm (GA) was used to solve the nonlinear optimization problem. Two approaches were used to incorporate uncertainties of the hydraulic conductivity field through the management process. The first one solved the problem for multi realizations of hydraulic conductivity simultaneously. Then the post-optimality Monte Carlo (MC) analysis was performed to assess the reliability of the optimal solution. While the second approach applied the MC simulation method to the studied problem.  A Fortran program was developed to apply the present methodology on a hypothetical coastal unconfined aquifer.

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