MODFLOW-NWT model for risk-based decision-support groundwater modeling for the lower San Antonio River Basin, Texas, USA

A MODFLOW-NWT groundwater/surface-water model was developed to evaluate the responses of low-flow conditions and groundwater levels within the lower San Antonio River Basin, Texas, USA under conditions of reduced recharge and increased groundwater withdrawals. There was concern that decreased recharge and increased groundwater withdrawals may adversely affect streamflow and groundwater levels. History-matching was carried out for the historical conditions of 2006-2013 using highly-parameterized inversion with PEST++ which produced a maximum a posteriori model parameter set which formed the central tendency of a posterior parameter ensemble using FOSM-based Monte Carlo uncertainty analysis. The ensembles were also created for two scenarios of 25% reduced recharge and 1% increased groundwater withdrawals or 25% increased groundwater withdrawals. This USGS data release contains all of the input and output files for the simulations described in the associated journal article (https://doi.org/10.1111/gwat.13107).