2007 Ground Water Summit

Tuesday, May 1, 2007 : 11:40 a.m.

Forensic Isotopic Hydrology Applied by a Multi-Agency Technical Team to Better Define Salinity Sources of the Lower Rio Grande Valley, New Mexico

R.L. Bassett, PhD, Geochemical Technologies Corp., Stephanie J. Moore, Daniel B. Stephens & Associates Inc., Beiling Liu, PhD, New Mexico Interstate Stream Commission, Christopher P. Wolf, Daniel B Stephens & Associates Inc. and Dale Doremus, New Mexico Environment Dept.

The Rio Grande Basin in New Mexico exemplifies the far-reaching and complex issues currently facing water management in the west.  In this study, investigation of Rio Grande salinity issues focused on identification of relative salinity contributions from anthropogenic and natural sources. A geochemical forensic approach was utilized to isolate specific contributors to observed salinization in the Rio Grande.  Success in our approach was assisted greatly by engaging multiple state agencies, technical firms, and analytical laboratories early in the design phase of the project.  Collaborative tasks included historical data review and quality assurance, sample collection, and final data interpretation.  This joint technical team relied on an existing conceptual model of the Rio Grande hydrologic environment to design the sampling schemes and select appropriate chemical and isotopic components to evaluate the hydrologic system.  In particular, the technical team selected isotopic candidates based on their applicability to this hydrologic system and the cost-effectiveness of the analysis.  Results using boron (δ11B), sulfur (δ34S), oxygen (δ18O), hydrogen (δD), strontium (87Sr/86Sr) as well as basic chemical data, confirmed the pre-project hypothesis of dominant salinity contributions from deep groundwater inflow to the Rio Grande.  The stable isotopic ratios identified the deep groundwater inflow as distinctive, and identified characteristic isotopic signatures.  The analytical results combined with simulated multi-component isotopic mixing and mass transfer modeling effectively eliminated evapotranspiration as the primary factor in observed Rio Grande salinization.  Although many forensic isotopic and chemical tools are potentially useful, utilizing the partnership of affected state agencies, technical firms, and laboratories allowed for development of a protocol that was efficient, focused, defensible, and cost-effective.

R.L. Bassett, PhD, Geochemical Technologies Corp. Dr. Bassett is president of Geochemical Technologies Corp., which is a geochemical consulting firm with an associated stable isotope laboratory. He was a Professor in the Department of Hydrology and Water Resources at the University of Arizona for 14 years, where he continues as an adjunct Professor. He holds a B.S. in Geology from Baylor University, a M.S. in Geochemistry from Texas Tech University, and a Ph.D. in Environmental Geochemistry from Stanford University. He has been principal investigator for numerous field and laboratory research projects. He has published extensively in peer-reviewed journals on issues related to radioactive waste geochemistry, ground water geochemistry, siting, isotopic geochemistry, contaminant migration and transport. He was a Darcy Distinguished Lecturer and an Associate Editor for the journals of Water Resources Research, Ground Water, and Applied Geochemistry. He has served on numerous review panels and boards, such as the University of Waterloo Centre for Groundwater Research Advisory Committee; National Academy of Sciences Committee on Low Level Radioactive Waste; Argonne National Laboratory Radioactive Waste Review Panel; Board of Directors of the National Ground Water Association, Association of Ground Water Scientists and Engineers; and the Hanford Ground Water/Vadose Zone Expert Panel.

Stephanie J. Moore, Daniel B. Stephens & Associates Inc. Stephanie Moore is a Hydrologist with Daniel B. Stephens & Associates. She spent eight years with the U.S. Geological Survey before joining DBS&A in early 2005. She holds a B.S. degree in Environmental Science and an M.S. degree in Earth and Planetary Sciences. Stephanie’s key areas of expertise include quantitative analysis of stream-aquifer interactions, vadose-zone processes, and spatial and temporal variations in water quality. She has successfully managed a variety of hydrogeologic investigations throughout New Mexico, including several comprehensive water quality studies. Ms. Moore has authored and co-authored several peer-reviewed papers and reports.


The 2007 Ground Water Summit