Water quality in the Río Blanco Basin and Potrerillos Reservoir, Mendoza, Argentina

The strategic location of the Potrerillos Reservoir in Mendoza’s Northern Basin highlights its importance; however, neither the reservoir nor the tributaries of the Río Blanco have been comprehensively assessed in relation to water quality issues. Land-use changes in the Río Blanco basin over recent decades have generated negative impacts on both the quantity and quality of water resources, as documented by this research group since 2005. These impacts are primarily associated with increasing anthropogenic pressures and the consequent rise in wastewater discharges and solid waste inputs. This study aimed to monitor physicochemical and microbiological water parameters and to propose strategies for the sustainable management of local water resources. With funding from INA-CRA and SECTyP-UNCuyo for the 2012–2014 biennium, 18 sampling campaigns were conducted at 10 sites: Alto Las Vegas, Alto Manantial, Río Mendoza, Vertientes Manzanares, Vallecitos, Aº El Salto, Embalse Potrerillos, Pozo Romero, Río Las Mulas, and Río Blanco. The parameters analyzed included pH, electrical conductivity (EC), dissolved oxygen, temperature, nitrates, phosphates, mesophilic aerobic bacteria, total coliforms, and thermotolerant coliforms. Results were benchmarked against regulatory standards. Overall, waters exhibited acceptable physicochemical quality; however, mesophilic aerobic bacteria, total coliforms, and thermotolerant coliforms frequently exceeded regulatory thresholds for drinking water, recreational use (direct contact), and irrigation, posing potential risks to human health. In general, contaminant loads increased along the river continuum from the headwaters to the reservoir outlet, with Río Las Mulas—and, to a lesser extent, Aº El Salto—identified as the most impacted tributaries.