New Mexico Geological Society Annual Spring Meeting — Abstracts

The rate and distribution of groundwater recharge to New Mexico's aquifers is the least understood aspect of the state's water budget. Despite a history of precise and distributed measurements quantifying surface water flow, water table elevations, precipitation amounts, as well as current models that describe evapotranspiration, a statewide assessment of recharge has not been completed. While recharge estimates and studies of recharge processes have been conducted, the effort to date has been on the basin scale, or by county or water planning region. With a long-term goal of estimating groundwater recharge on a statewide scale, we have undertaken recharge modeling based on the soil water balance approach in order to represent relevant physical parameters affecting the rate of recharge. We use raster grids representing spatially distributed physical parameters including precipitation, soils, geology, reference evapotranspiration, and vegetation as inputs to the model. Implementing methodology developed by the United Nations Food and Agriculture Program, we calculate actual evapotranspiration and tabulate a daily soil water depletion from three one-dimensional soil layers. We then calculate recharge based on modeled soil saturation and saturated bedrock hydraulic conductivity. With support from the New Mexico Water Resources Research Institute’s Statewide Water Assessment we have compiled recharge estimates from around the state and have constructed our recharge model. We plan on using funds provided by NMGS to field-verify this model using the chloride mass balance technique.