New Mexico Geological Society Annual Spring Meeting — Abstracts

The central Rio Grande Valley in Valencia County, New Mexico, is marked by shallow water tables (~1-5 m depth), flat topography dominated by agricultural use, and a complex system of acequias (irrigation canals) that distribute Rio Grande water out of the river and onto fields on the floodplain. These three factors, among others, can lead to rapid and complex changes in surficial aquifer conditions in this region. The focus of this project is to illustrate chemical, biological, and physical properties of the groundwater at two specific locations in Valencia County: Whitfield Wildlife Conservation Area (WWCA), a former commercial dairy; and the University of New Mexico-Valencia campus, which contains large parking lots and building footprints leading to significant runoff during rain events. The water table depth and pH in wells at WWCA have been monitored monthly for approximately 10 years since their installation in 2009. Baseline geochemical data from these wells were collected in December 2009. Our study seeks to better understand the effects of land use on local aquifer properties; to include developing a partnership with the community for future research opportunities; and to understand the timing of effects of land use and management on our local groundwater. We have analyzed groundwater from these wells for the presence of bacteria in low concentrations; our results show that bacteria are present in several wells and we have identified them via DNA isolation and metagenomic analysis. We re-analyzed geochemical properties of the WWCA wells in early 2019 and present here the decade-long change in surficial aquifer geochemistry in this protected natural area. Our work has included the chemical and physical monitoring of local wells, mathematical analysis of well hydrological data, and comparison to climate, weather, water depth history, and irrigation data.