On the physical and mathematical modeling of the coupling of rivers and aquifers as sustainable water supply systems

Abstract

A physical and mathematical model is presented to simulate realistic hydrological conditions and to evaluate coupled river and aquifer as water supply system. The approach is applied to estimate the extraction effects on the river and related aquifers under different conditions, with the purpose of determining the water supply potential and sustainability of the coupled system. The model consists of the conceptual and numerical coupling of two structures that take into account different aspects of the systems being considered. The first is a free-surface flow structure, and it carries out the balance of mass and momentum along the river course, whereas the second one is of hydrogeological type that performs the mass balance in combination with Darcy's law in each aquifer of interest for evaluation purposes. The two parts of the model are coupled by their source terms with a very simple linear relationship; the numerical implementation is carried out by using MODFLOW and ISIS codes. After calibrating the models with field parameters, an iterative coupling process is given where each structure must satisfy their criteria of internal convergence. The complete model is satisfactory whenever the iterative coupling process and the hydrogeological and hydraulic models converge. The conceptual approach is applied to the real and natural system constituted by the Papagayo river and the aquifers located in the river banks locally known as Norte, Obra de Toma, and Lomas de Chapultepec, in the State of Guerrero, México to determine their sustainable water supply potential. © 2013 WIT Press.