Caracterización hidrogeoquímica en La cuenca hidrológica El Carrizal, Baja California Sur, México

The El Carrizal hydrological basin is located in the southwest zone of the state of Baja California Sur, Mexico. The El Triunfo-San Antonio mining district, where mine tailings are located with high concentrations of potentially toxic elements (PTEs), is located in the higher part of the basin. The demographic growth of the city of La Paz has pushed to transfer water from this basin, so the aim of this work was to characterize the hydrogeochemical composition of groundwater and to evaluate the water quality for human consumption. In the year 2015, 19 wells in the El Carrizal basin and 11 wells in the basins of La Paz, La Matanza and Santa Inés-La Muela were sampled during the dry (April-May) and rainy (November-December) seasons. The physicochemical parameters were measured in situ, the major ions (Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ , Cl ^- , SO ₄ ^2- , HCO ₃ ^- and NO ₃ ^- ) and PTEs (As, Cd) were determined in the laboratory. The results indicated that the types of water are mainly associated with the lithology of the area in the upper part of the El Carrizal basin, and that the type of water that predominates contains Ca ²⁺ and HCO ₃ ^- . In the study area, 67 % of the wells in the dry season exceeded the concentration limit of As (10 µg/L). A continuous monitoring of these groundwater wells is necessary to support the supply programs for the population.