Tracking Deep Groundwater in Northwest New Mexico: Water Chemistry Evolution and Potential Recharge Implications

Water quality data was utilized to construct a model across the southeastern Colorado Plateau (CP) to the Albuquerque basin (AB) using groundwater ages within the AB as residence times of the groundwater.  This model was developed because to date no study has assessed the amount of recharge the San Andres-Glorieta (SAG) aquifer provides to the AB.  Several groundwater flow models have suggested recharge contributes up to 25,000 acre-feet per year.  Recharge amounts may determine how fast this deep aquifer is replenished as well as understanding the effects of pumping from the SAG aquifer since most of the 576 recently (2009) contemplated well sites listed in “notices of intention” filed with the New Mexico Office of the State Engineer are listing the SAG aquifer as target.  Eighty percent of these notices of intention involve well sites within the transition zone between the AB and the CP, where relay ramps provide a complex network of connections between aquifers.
To build a representative model, we relied on existing USGS studies characterizing the SAG aquifer, utilized existing NMBGMR cross sections, and categorized geochemical data in order to develop a hydrogeological model of groundwater within the CP. The Plummer et al. (2004) dataset was utilized to constrain the final composition of the average groundwater sample in the western AB, whereas the evolution of a theoretical SAG groundwater sample was constrained by water quality sample data from the USGS NWIS.  Our model suggests there is some variation in SAG aquifer water quality that could be explained by some groundwater moving quite fast, whereas older (and slower) groundwater may contribute the bulk of the salinity but not the volume.  The groundwater flow to the AB may therefore be concentrated into several pathways; some that preferentially move along dominant (karstic) corridors within the Rio San Jose corridor.