Publication ID: 9529
Title: Applying Geochemistry to Predict Water Quality at Managed Aquifer Recharge Sites
Abstract: Managed aquifer recharge is an important water resource management tool being implemented at sites in New Mexico. This method uses surplus water to recharge aquifers, and to store and recover the water for later use. Predicting water quality of the recovered water is an important part of the initial site characterization. Chemical reactions of the recharged water with both groundwater and the aquifer matrix may be predicted using site-specific data. Several examples from New Mexico will be presented, illustrating the use of geochemical techniques to predict the water quality of the recovered water.
In the Santa Rosa-Chinle aquifer system, potential reactions between treated surface water and the aquifer materials that may mobilize iron (Fe) and manganese (Mn) were evaluated, and the calculated saturation indices (SI) and oxidation reactions indicate that Fe and Mn solubility should be limited during recharge operations.
In the Tesuque Formation, fluoride concentrations were predicted to exceed the U.S. Environmental Protection Agency maximum contaminant level (MCL) in the recovered water, based on fluorite solubility and mixing calculations. This information was used to identify treatment requirements for potable use of the recovered water.
In the Santa Fe Group aquifer system, arsenic concentrations were initially diluted by the injected water but quickly rebounded during recovery pumping, as a result of dissolving iron coatings on aquifer sediments, releasing iron and adsorbed arsenic into solution.
These geochemistry studies provided critical information about operations and treatment of waters recovered from these managed aquifer recharge systems.
Citation: Wolf, C., Marley, R., and Ewing, E. Applying Geochemistry to Predict Water Quality at Managed Aquifer Recharge Sites. New Mexico Water Conference, Taos, New Mexico, October 7-9, 2015.