primarily agricultural) and decreased baseflow because of groundwater production. For example, in 2002 the Before recent drilling and characterization efforts in the vicinity State of New Mexico was unable to honor interstate of Los Alamos National Laboratory (LANL), conceptual models had been developed for recharge and discharge in the regional aquifer on stream compacts for surface water delivery to Texas and the basis of sparse data. By integrating site-wide data into a numerical incurred substantial penalties. There are also concerns model of the aquifer beneath the plateau we provide new insight into about water quality at the regional scale because of a large-scale aquifer properties and fluxes. This model is useful for variety of contaminants, both nonanthropogenic and anunderstanding hydrologic mechanisms, assessing the magnitudes of thropogenic. Beneath the Pajarito Plateau, there is subdifferent terms in the overall water budget, and, through sampling, for stantial contamination from various LANL sources in interpreting contaminant migration velocities in the overlying vadose shallow groundwaters in some locations (primarily alluzone. Modeling results suggest that the majority of water produced vial aquifers), and it is unclear what the ultimate impact in well fields on the plateau, extracted at rates approaching 70% ofof this contamination will be on the regional aquifer in total annual recharge, is derived from storage. This result is insensitive the future. Some of the LANL-derived contamination to assumptions about the percentage of total recharge that occurs in the near vicinity of water supply wells, because of strong anisotropy has been observed in the regional aquifer at trace conin the aquifer that prevents fast transport of local recharge to deeper centrations much below the EPA drinking water stanunits from which production occurs. Robust estimates of fluxes in the dards. To assess the future water quality and quantity shallow portion of the aquifer immediately down gradient of LANL issues, 21 deep characterization wells have been drilled are important for contaminant transport simulations. Our model calsince 1995, and flow and transport models have been culations show that these fluxes have decreased in the past 50 years developed both at the site-and basin-scale.by approximately 10% because of production in water supply wells.
Historical liquid effluent discharges in canyons areTo explore the role of parameter uncertainty in flux prediction, a the most likely sources of this deep groundwater conpredictive analysis method was applied. Results showed that predicted tamination. These contaminants must migrate through flux through older basalts in the aquifer can vary by a factor of three the unsaturated rocks of the vadose zone before reachbecause of uncertainty in aquifer properties and total recharge. We explored the impact of model parameter uncertainty on these results; ing the regional aquifer. Some of the most convenient however, the true uncertainty of our predictions, including the imp...