A methodology to analyse and assess pumping management strategies in coastal aquifers to avoid degradation due to seawater intrusion problems

摘要

In this paper we will focus on an interesting and complex problem, the analysis ofcoastal aquifer management alternatives in aquifers affected by seawater intrusion problems. Asysthematic method based on an approximation of the safe yield concept for coastal aquifersand a simple model approach to the problem is proposed to help in the decision makingprocess. It is based on the assessment of an index, that we have called the Pumping Reductionto Achieve a Natural Good Status (PRANGS), which we have defined as the minimumreduction in pumped abstractions necessary to maintain seawater intrusion below the valueestimated for the natural regime under different climate conditions: humid (PRANGSh),intermediate (PRANGSi) and dry years (PRANGSd). It requires to solve an optimizationproblem (for each of the climate conditions: humid, intermediate and dry years), whoseobjective function is to minimize the reduction in pumping whilst ensuring intrusion doesnot exceed the natural regime ones. A simulation model that provides a valid approximation ofseawater intrusion is needed. The methodology was applied to a well-known SpanishMediterranean aquifer, the Oropesa-Torreblanca Plain aquifer. The optimization problemwas solved using an iterative process from a constant density flow simulation model of theaquifer, assuming a direct relationship between piezometric drawdown and seawater intrusion.