Hydrochemistry of the Mocorito river coastal aquifer, Sinaloa, Mexico: water quality assessment for human consumption and agriculture suitability

Background. Groundwater is a vital source of water for domestic and agricultural activities and the water of the Mocorito River Coastal Aquifer (MORCA), located in the agricultural valley of Culiacan, Sinaloa, Mexico, is not an exception. Goals. To assess MORCA's groundwater quality for drinking and irrigation purposes and the geochemical processes affecting its composition. Methods. Twenty-two well samples were collected during the dry and rainy seasons. Physical and chemical parameters, major ions, drinking quality (WQI and PHASECH water quality index), and irrigation suitability Richards (1954) and Wilcox diagrams) were studied. Results. Total Dissolved Solid (TDS) ranged from 1688 - 8762 mg L-1 for the dry season and 89-10016 mg L-1 for the rainy season. From inland to the coastal zone, MORCA's groundwater was considered hard and very hard, with non-dominant hydrochemical facies in the dry season and calcium, magnesium and sodium (cationic), and bicarbonate and chloride (anionic) types, in the rainy season. US Salinity Staff and Wilcox diagrams revealed that MORCA's groundwater is not suitable for use in irrigation. Further, the geochemical processes controlling the chemical composition of MORCA were evaporation and weathering. Conclusions. According to the TDS and water quality index (WQI and PHASECH) classifying just 4.5 % and over 50 % of the samples, respectively, MORCA water can be considered suitable for human consumption; only the groundwater from site EE-1, in the rainy season, was considered suitable for human consumption. US Salinity staff and Wilcox diagrams indicate that almost 50% of MORCA's groundwater is not suitable for irrigation use. MORCA's groundwater composition is dominated by evaporation and weathering of minerals such as anorthite, illite, and kaolinite.