A FOUR-YEAR COMPARATIVE STUDY OF THE GEOCHEMISTRY AND HYDROLOGY OF SELECT SPRINGS IN THE SEVILLETA NATIONAL WILDLIFE REFUGE

Water scarcity and management is a major concern in the Rio Grande rift corridor of central NM. High salinity and trace element concentrations are known to impair water quality, and identifying sources of these contaminants remains ongoing. Research conducted with the Sevilleta LTER and NSF Research Experience for Undergraduates (REU) program compared a four-year study of multiple perennial spring compositions in the Sevilleta National Wildlife Refuge (SNWR).

Geochemical data from 2007-2009 were compared to new data collected during summer 2010 for three springs (Cibola, San Lorenzo, and Ladron springs) in the SNWR, both before and after the onset of the monsoon season. To compare these systems over multiple years, water quality was determined via measurement of field parameters (pH, conductivity, temperature, TDS, and DO), analyses of major and trace elements and geochemical modeling.

Major ion and trace element concentrations of these three spring systems were not found to vary over the cumulative four year study. Geochemical modeling with PHREEQc was conducted to calculate saturation indices for ubiquitous minerals such as calcite and gypsum. The saturation indices in the spring systems were found to correspond to major ion chemistry of the springs. Cibola spring was found to have a consistent Ca/SO₄ chemistry, San Lorenzo spring consistently yielded a Na/HCO₃ chemistry, and the Ladron springs had a mixed ion chemistry. No distinct change was detected in the chemistries after the start of the monsoon season. A lack of variation in geochemical parameters has implications for the extent of subsurface flow, controlled by regional tectonic features, that feeds these three hydrologically distinct systems.