New Mexico Geological Society Annual Spring Meeting — Abstracts

Under the Rio Grande Compact, New Mexico is obligated to deliver a specified amount of water to satisfy demands in New Mexico and Texas below Elephant Butte reservoir. This indicates that a finite amount of water is available to New Mexico north of Elephant Butte reservoir for habitat preservation and agricultural, industrial, and domestic uses. Previous investigations have observed significant seepage losses from the Rio Grande to the shallow aquifer between Socorro and the Bosque del Apache. Small scale modeling of a 6-mile reach of the river between Brown Arroyo and San Antonio is aimed at determining the causes for surface water loss and investigating methods for minimizing such losses. Simulations will include alternative river channel locations, riparian vegetation changes, and changes in river/aquifer interactions. Layers included in the model extend upward from the Santa Fe Group and lie within the lateral extent of the floodplain. Grid cell size is 100 by 100 feet. Information collected to help calibrate the model includes; floodplain geologic cross sections, monthly groundwater elevations,
monthly surface water elevations in drains, canals, and the river; surface water flow data; precipitation records; aquifer pump tests, seepage run results; and three water chemistry snapshots in 2002, including the stable isotopes ²H and ¹⁸O . This model is a telescopic version of a regional model of the Rio Grande reach from San Acacia to Elephant Butte reservoir which is being developed by the New Mexico Interstate Stream Commission.