A water balance approach to the sustainable management in the San Salvador Aquifer

Abstract

A thorough understanding of the interaction between the different components, that integrate all the phases of the hydrological cycle, is crucial and of vital importance in the use, conservation and protection of water. In urban environments, quantification of water balance components becomes particularly challenging. This study presents the spatial analysis of the sustainability of the San Salvador aquifer, a typical urban aquifer, which provides part of the water supply of the San Salvador Metropolitan Area (AMSS) in conjunction with three water import systems. Thus, the hydrogeological system and its flow systems have been characterized, likewise the components of the water balance have been identified, refined and quantified, defining the inputs, outputs and returns to the system. At the same time, the water balance equation has been proposed for the aquifer based on these components. Results show that the San Salvador aquifer is in an "apparent state of sustainability" that is supported by urban recharge, which represents multi-million-dollar annual pumping costs. That money could be reoriented to minimize water system leakage as well as to reduce withdrawals in the aquifer. Thus, the volume of water saved could be used to improve the water supply to the AMSS, store a reserve to face dry years or the recovery of dependent ecosystems. Additionally, the urban development of the northern slope of the San Salvador volcano, which reflects the areas with the highest water availability, must be carried out with caution since it entails a reduction in groundwater recharge. This would imply a decrease in base flow of the San Antonio and El Ángel rivers, which represent important sources of water supply for the AMSS users.