Abstract
Abstract The increased pumping of freshwater from coastal aquifers, to meet growing demands, causes an environmental problem called saltwater intrusion. Consequently, proper management schemes are necessary to tackle such a situation and permit the optimal development of coastal groundwater basins. In this research, a probabilistic search algorithm, namely Probabilistic Global Search Lausanne (PGSL), is used to calculate optimal pumping rates of unconfined coastal aquifer. The results of using PGSL are compared with a stochastic search optimization technique, Shuffled Frog Leaping Algorithm (SFLA). The finite element method is applied to simulate the hydraulic response of the steady state homogenous aquifer. The lower and upper (LU) decomposition method is adapted to invert the conductance matrix, which noticeably decreases the computation time. The results of both the PGSL and the SFLA are verified through the application on the aquifer system underlying the City of Miami Beach in the north of Spain. Multiple independent optimization runs are carried out to provide more insightful comparison outcomes. Consequently, a statistical analysis is performed to assess the performance of each algorithm. The two optimization algorithms are then applied on the Quaternary aquifer of El-Arish Rafah area, Egypt. The results show that both algorithms can effectively be used to obtain nearly global solutions compared with other previous published results.
Highlights
Groundwater contamination through saltwater intrusion threatens the health of many people living in coastal areas
The results of the Probabilistic Global Search Lausanne (PGSL) are compared with the well-known Shuffled Frog Leaping Optimization Algorithm (SFLA)
The Finite Element Method (FEM) is applied on the linear formulation of Strack ( ) to simulate the hydraulic response of the steady state homogenous aquifer
Summary
Groundwater contamination through saltwater intrusion threatens the health of many people living in coastal areas. Stochastic optimization combined with flow simulation has been widely used to control saltwater intrusion and the general management of coastal groundwater. The use of numerical or analytical methods for coastal aquifer simulation along with optimization algorithms is constrained by the huge computational burden involved. Studies of the application of stochastic optimization algorithms for the management of coastal aquifers are reported in the literature. The objective of the current study is to calculate the optimal pumping rates in an unconfined coastal aquifer under steady-state conditions and assuming a sharp saltwater interface. For the unconfined aquifer, the following assumptions are considered (Figure 1): (1) sharp interface between saltwater and freshwater, (2) the three-dimensional geometry flow equation is reduced to two-dimensional by Dupuit’s assumption, (3) steady-state flow condition, (4). The PGSL involves the following steps: 1. Initialization: The PDF of each decision variable is assumed having a uniform distribution over the entire domain
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