Abstract

The Barton Springs segment of the Edwards Aquifer, a karstic aquifer in Central Texas, is the source of drinking water for an estimated 60,000 people, and its springs are habitat for endangered species. A substantial increase in the total discharge from the aquifer has occurred over the past 60 years. This paper reviews historical precipitation and hydrologic data from Central Texas and characterizes temporal trends proximate to the aquifer. The analyses focus on precipitation, streamflow, water-level, and springflow sites with long-term data (since 1930s) and within a 75-mile radius of Barton Springs. Data were analyzed with hydrographs, best-fit linear temporal trend lines, and statistical evaluations. Over the period of record by decade, annual mean temperatures increased up to 3%, annual precipitation increased about 13%, streamflows increased about 112%, and discharges at Barton Springs increased about 86%. Streamflow and springflow data indicate that a change to a wetter climate has occurred since the 1960s. For the period of record, low stream baseflows and springflows have increased only modestly compared to higher flows. However, over the past 30 to 40 years stream baseflows and low springflows have been decreasing despite the wetter climate since the 1960s. Significant increases in pumping during the last 40 years in the area are likely the major cause for this trend of decreasing stream baseflows and springflows. Decreasing stream baseflows and increased pumping will cause decreased water availability during future droughts. Higher flows during wet periods will not significantly decrease the impacts of droughts.