Isotopic and geochemical characterization of recharge and salinity in a shallow floodplain aquifer near El Paso, Texas

The shallow alluvial aquifer of the Rio Grande floodplain near El Paso, Texas is a dynamic intermediary of recharge, discharge, and salinization processes between the deeper Hueco Bolson Aquifer and the overlying Rio Grande. Environmental tracer analyses suggest that (1) shallow aquifer groundwater is primarily of either Modern-Day Rio Grande origin or from older, less evaporated Pre-Dam Rio Grande waters, with modern local meteoric waters contributing a dominant fraction generally only near mountain fronts and (2) salinization of the Rio Grande and shallow aquifer in the southeastern portion of the Hueco Bolson is due to both near-surface agricultural impacts as well as the influx of naturally saline deep groundwater. With leakage from the shallow aquifer providing significant recharge to the deep Hueco Bolson Aquifer, any future development which may potentially decrease river infiltration must be carefully considered. Additionally, efforts to increase local irrigation efficiencies may have limited effects on water quality given the presence of natural solute sources.