Applying Geochemistry to Managed Aquifer Recharge Projects

Wednesday, February 24, 2016: 1:00 p.m.
Christopher P. Wolf, PG , Water Resources Division, Daniel B. Stephens & Associates, Inc., Albuquerque, NM
Robert Marley, M.S. Hydrology , Water Resources Division, Daniel B. Stephens & Assoicates, Inc., Albuquerque, NM
Amy Ewing, P.G. , Daniel B. Stephens & Associates, Inc., Albuquerque, NM

Managed aquifer recharge is being implemented at sites across the southwestern United States as an important water resource management tool, in order to recharge and store surplus water within aquifers, and to recover this water for later use. Compatibility of the recharged water with both groundwater and the aquifer matrix may be predicted using geochemical models and mixing calculations supported by 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, and to track recharged water in the aquifer.

In the Santa Rosa-Chinle aquifer system, the potential for reactions between treated surface water and the aquifer materials that would mobilize iron (Fe) and manganese (Mn) was 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 water use.

In the Santa Fe Group aquifer system, arsenic concentrations were initially diluted by the injected water but quickly rebounded during recovery, as a result of dissolving iron coatings on aquifer sediments releasing iron and adsorbed arsenic into solution. In another case, sulfur hexafluoride (SF6) was injected into the recharge water as a conservative tracer used to monitor recharge water movement in the aquifer. The SF6 tracer was observed in the monitor well network eight days after injection operations started, at a distance of 75 feet from the injection well.

These geochemistry studies provided critical information about the operation and treatment of waters recovered from these managed aquifer recharge systems.

Christopher P. Wolf, PG, Water Resources Division, Daniel B. Stephens & Associates, Inc., Albuquerque, NM
Christopher Wolf is a senior scientist specializing in geochemistry and geology with 20 years of experience at Daniel B. Stephens & Associates and working in New Mexico. He holds M.S. and B.S. degrees in geochemistry and geology, respectively, from the New Mexico Institute of Mining and Technology. Wolf’s experience includes evaluating water quality for managed aquifer recharge and water resources projects.

Robert Marley, M.S. Hydrology, Water Resources Division, Daniel B. Stephens & Assoicates, Inc., Albuquerque, NM
Robert Marley has 25 years of environmental and water resource consulting experience. Areas of expertise include vadose zone and groundwater characterization and remediation; water quality monitoring and management; groundwater tracer studies; water resource planning and permitting; implementation of artificial recharge systems; and stakeholder involvement. His current focus is on water reuse applications, development of alternate water sources, and water treatment technologies.

Amy Ewing, P.G., Daniel B. Stephens & Associates, Inc., Albuquerque, NM
Amy Ewing is a Hydrogeologist at Daniel B. Stephens & Associates, specializing in water supply and conservation planning, water resources investigations, aquifer storage and recovery, and watershed restoration projects. She is a licensed Professional Geoscientist in Texas, and holds bachelor’s and master’s degrees in Earth Science and Water Resources.