Study examines inflows to Pedernales River

Meadows Center

The Meadows Center for Water and the Environment at Texas State University has released a series of reports that indicate groundwater provides a significant contribution of flow to the Pedernales River and Lake Travis.

The Pedernales River is an important source of water to Lake Travis, which supplies drinking water to millions of people in Austin and many other downstream municipalities along the Colorado River. As part of a larger study to answer “How Much Water is in the Pedernales?” Th e Meadows Center conducted a base flow and dye trace study in late 2017 to examine the Pedernales River’s complex, interconnected surface and groundwater systems.

According to the base flow report, the Pedernales River contributes 23 percent of its annual inflow to Lake Travis with a significant amount of this inflow originating from groundwater. The Meadows Center worked alongside the Blanco-Pedernales Groundwater Conservation District and the Hays Trinity Groundwater Conservation District (HTGCD) to collect data from more than 40 wells along the Pedernales River and determine groundwater fl ow patterns.

“We hope the findings from these studies will help guide decision makers in developing appropriate management strategies to ensure that fresh water is available for the future,” said Doug Wierman, geoscientist and Meadows Center fellow.

The base flow study also confirmed that groundwater from the Paleozoic and Cretaceous aquifers recharge the river and provide a majority of the water gained, particularly on the north side of the river, downstream from Johnson City.

“Future groundwater management actions in the Pedernales River need to consider the importance of this area (downstream of Johnson City) to maintaining adequate flows and adequate water supplies,” Wierman said.

Following the base flow study, The Meadows Center conducted a dye trace study to find the source of water to the major spring at the base of the falls at Pedernales Falls State Park. The report confirmed the source to be mainly a diversion of river water from several miles upstream.

“What I did not expect to find was that the gain we saw from the spring (approximately 15 cubic feet per second, or cfs) was about twice of what we were actually losing in the river (10-11 cfs),” Wierman said. “The river was gaining more than it was losing, which tells me there is another source of water to that spring—which is probably groundwater interflow.”

Partners involved in the dye trace study include the Barton Springs/Edwards Aquifer Conservation District, HTGCD, Texas Parks and Wildlife Department and the City of Austin.

To read the full reports and for more information on The Meadows Center’s work in the Pedernales River at the Meadows Center for water and Environment's website.

San Marcos Daily Record

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