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Corresponding Author

El-Ghandour, Hamdy

Subject Area

Civil and Environmental Engineering

Article Type

Original Study

Abstract

Groundwater is considered as an important source of freshwater for several purposes. The increasing demand of groundwater has resulted in an indiscriminate of this source causing environmental hazards such as decline of groundwater levels and well interference. This paper presents a new methodology for optimal management of groundwater in unconfined aquifers in case of uncertainty due to spatial variability of hydraulic conductivities. The suggested methodology includes application of two main consecutive approaches. In the first approach, Monte Carlo simulation is adopted to generate multiple realizations of the hydraulic conductivity values depend on limited field measurements, then a simulation-optimization model is developed and applied to solve the groundwater management problem for each realization. The results of the simulation-optimization model are several Pareto-front optimal solutions for each realization. A unique Pareto-compromise solution for each Pareto-front is determined. In the second approach, to assess the reliability analysis, Pareto-compromise solutions are divided into groups according to the number of wells to detect the most reliable number of wells. The most reliable locations of wells (also their discharges) are detected by splitting these Pareto-compromise solutions into groups according to a new suggested term called radius of gyration. For each group, the performance/state function is assumed as a function of the two objectives corresponding to each Pareto-compromise solution. Then, Monte Carlo simulation, Latin Hypercube sampling, and First Order Reliability Method are applied to study the reliability of the estimated function corresponding to each realization. The methodology is then illustrated by the application on the Quaternary Aquifer of Wadi El-Tumilat, Egypt. The proposed methodology shows its ability to suggest only one system of wells of high level of reliability.

Keywords

Reliability; multi-objective optimization; uncertainty; Unconfined aquifer; Hydraulic Conductivity; Genetic Algorithm; Finite element method; Quaternary aquifer

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