EVALUATION OF GROUNDWATER/SURFACE WATER INTERACTIONS IN THE MIDDLE RIO GRANDE BASIN

The goal of this research is to quantify interconnections between the river and shallow groundwater along the Rio Grande between San Acacia Diversion Dam and Elephant Butte Reservoir. Understanding this reach of the river is crucial to assure proper allocation of water by New Mexico to its stakeholders and downstream consumers. Previous investigations have observed significant losses from the river to the groundwater in this region. This reach of the river is critical for riparian habitat, endangered species, industrial uses, and irrigated agriculture. Groundwater and surface water elevations are being measured on a monthly basis using an extensive monitoring network. Water chemistry including ²H and ¹⁸O are being determined quarterly. Data from the winter of 2001-2002 and the summer of 2002 show that surface water and groundwater exhibit distinct chemical and isotopic signatures, and that the river is losing water to the aquifer along most of the reach. Collected water chemistry and elevation data will be used to calibrate a model being developed to aid management of water resources in the Middle Rio Grande Basin.