The Use of Historical Data and Global Climate Models to Assess Historical and Future Surface Water and Groundwater Availability in the Trinity River Basin in Texas

Abstract

As part of the Integrated Water Availability Assessment Program, the U.S. Geological Survey (USGS) and local partners, compiled historical data and developed surface-water (1980-2099) and groundwater (1949-2087) models to assess changes in recent historical and future water availability in the Trinity River Basin in Texas. A Trinity River Basin surface-water model and a Trinity River alluvium aquifer groundwater model were created to evaluate future water availability and long-term trends under different global climate model scenarios. The Trinity River Basin is divided into two regional water planning groups: Region C Water Planning Group and Region H Water Planning Group. Trend analyses using historical data (1900-2017) indicated an increase of annual precipitation on the watersheds that drain into the reservoirs in Region C Water Planning Group. However, the global climate model ensemble mean for the Trinity River Basin surface-water model indicates a downward trend in annual precipitation, resulting in a downward trend in Hortonian runoff. Additionally, the global climate model ensemble mean for the Trinity River Basin surface-water model and the Trinity River alluvium aquifer groundwater model both indicate a downward trend in recharge. The results show that the change in future water availability that can be attributed to climate change is small, assuming the average of the ensembles is the best predictor of the future.