Effects of Climate Change on Hydrology of the Nueces River Basin in South Texas

Abstract. Freshwater availability in arid and semi-arid regions is threatened due to climate change as well as by increase in water demands. Several studies projected increase in drought risks and frequent water shortages in the arid and semi-arid regions. Therefore, we estimated the effects of historic climate change on hydrology of the Nueces River Basin (NRB) - a semi-arid basin in South Texas, which would be useful in effectively utilizing climate change information in improving water resources management during the overlapping observations. The NRB supplies freshwater to ~500,000 residents and provides inflows to the Nueces Bay, which serves as a habitat for aquatic species. We utilized historical simulations (1981-2005) from four General Circulation Models (GCMs) under medium emission scenario to implement a semi-distributed Variable Infiltration Capacity (VIC) hydrological model at 1/8° resolution to estimate effects of climate change on water availability. The VIC model was calibrated and validated at two USGS streamflow gauging sites that were not impacted by reservoir operations. Then the VIC model was driven by statistically downscaled and bias-corrected climate forcings from four different GCMs from 1956 to 2005. Our results indicate that the warming pattern was captured under all the four GCMs during 1985-2005period but the warming magnitude was underestimated by ~0.5°C. Most GCMs were able to capture reduced streamflow by 20-60% during 1985-2005 in the southern part of the NRB; however, increase in runoff in the northern part was not captured by the GCM historic simulations.