Assessing the impacts of cooling methods of energy plants on groundwater resources in an arid basin and the delayed influence on the Colorado River leakance

Abstract:

Different cooling methods associated will utility-scale solar energy production utilize vastly different amounts of water. In a hyper-arid Southwestern US basin, where new energy projects are being developed, groundwater is the only available water for such cooling needs. The hydrologic impacts of groundwater withdrawal remain unclear, as recharge to the aquifer and exchange with the Colorado River are poorly quantified. The basin is also a data-scarce region, with few available groundwater parameter measurements for most of the basin. Characterized by a thick alluvium layer and deep aquifer, the basin also has a long response time to forcings. We employ both an integrated, physically-based surface-subsurface processes model (PAWS+CLM) and the MODFLOW+PEST package. The integrated model PAWS+CLM is used to estimate recharge while MODFLOW+PEST is used to estimate the groundwater conductivity fields. Calibration of the two models are iterated to obtain the best estimates of parameter values. We have identified the main area of recharge by forcing the model with both station-based measurements and NLDAS. The Colorado River is losing water in this reach. Using the combined, coupled model, we estimate the influence of cooling methods on the water table and its effect on the land-river exchange.