Gain-Loss Studies in the Colorado River Basin of Texas: Drought of 2011–2012 Update

Geoffrey P. Saunders
3700 Lake Austin Blvd., Austin, Texas 78703

The Highland Lakes consist of two large storage reservoirs and four smaller passthrough lakes in the Texas Hill Country used as a system to supply water to the lower Colorado River, which is a gaining stream from Austin, Texas to the Gulf Coast. The drought of 2011–2012 in Texas has put a focus on groundwater–surface water interactions. In this study, multiple approaches were used to estimate groundwater contribution to the Highland Lakes and Colorado River of Texas. These approaches included gain-loss field studies, hydrograph separation analyses, gauge flow differential analyses, and mass balance accounting. In addition, information from hydrogeologic studies and groundwater availability models were used to support estimates of stream flow gains from groundwater contribution. The sources of groundwater contribution were identified as major and minor aquifers intercepted by the Colorado River, and less-recognized formations that drain into and contribute to the river system. These sources impart a component of base flow to a highly regulated, regional water supply operation.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012