Origin of Salinity in Groundwater of Neighboring Villages of the Cerro Prieto Geothermal Field

The residual brine of the Cerro Prieto Geothermal Field (CPGF) is disposed in an evaporation pond. The seepage of this pond has contaminated the water and agricultural soil around it. The contamination of the groundwater towards the southwest by the evaporation pond, in the direction of the regional flow, has been shown before. Hydrogeochemical modeling (PHREEQCI) and Schoeller and Piper diagrams have been used in this work to show that the chemical composition of the groundwater in villages neighboring CPGF is the product of mixing between irrigation water from the Colorado River and brine from the evaporation pond. The high potassium concentration in the water and the relative increase in concentration of sodium and chlorides along the flow path as well as the hydrogeochemical models for this system explain this mixing process. This work will allow proposing new managing techniques to avoid the presence of the residual brine in the groundwater of agricultural lands.