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All-time lows for Burnet County groundwater

Central Texas Groundwater Conservation District groundwater technician Shrader Davis

Central Texas Groundwater Conservation District groundwater technician Shrader Davis points to a map of Burnet County’s complicated hydrology, which includes a half-dozen aquifers. Staff photo by Dakota Morrissiey

Aquifers in Burnet County don’t just need “some” rain to refill, they need “significantly above-average” precipitation to adequately recharge, according to the Central Texas Groundwater Conservation District. The county remains in an extreme drought, and some wells are approaching or have surpassed their lowest levels on record. 

“Even if we were to receive inches’ worth of rainfall, that merely gets us back to what we’re supposed to be getting this time of year,” district General Manager Mitchell said at the Sept. 15 board meeting. “We need much above-average rainfall to get any kind of recharge into these systems.”

Boar directors agreed to maintain the Stage 4 drought status that has been in effect since June 2022, which recommends that all groundwater users reduce use by 30 percent. The district’s drought stage is heavily influenced by the Palmer Hydrological Drought Index, which currently indicates Burnet County is at a negative 4 or below on its scale, the most severe ranking. Burnet County is also under mandatory 15 percent reductions to overall allowed groundwater use for high-volume permit holders. The mandatory restrictions were imposed for the first time ever in December 2022.

The county has been in either negative 4 or negative 3 conditions since at least April 2022. The PHDI takes into account lake and groundwater levels, which often require more time to recover than soil moisture and precipitation levels used by most drought-monitoring systems.

Sodek referred to data from monitoring wells in four different aquifers in Burnet County. The Ellenburger-San Saba, Trinity, Hickory, and Granite Gravel aquifers all show significant declines in water levels that are near or below the lowest on record.

“Not many counties have as complicated of a geology and complicated aquifer system that we have,” district groundwater technician Shrader Davis said at the meeting. “Just depending where you are geographically, you could be going into any of those aquifers.”

historical well levels on the Ellenburger-San Saba Aquifer
Two graphs from the Central Texas Groundwater Conservation District show historical well levels on the Ellenburger-San Saba Aquifer, which are currently near or below all-time lows. The well level is depicted in red; the blue line shows drought levels from the Palmer Hydrological Drought Index. Central Texas Groundwater Conservation District image

The county has four to six aquifers, depending on state designations. asked Davis to explain the significance of the low levels depicted across the district’s monitoring well network. 

“We’ve been monitoring since 2009 in certain places and its relative drawdown,” he said. “It doesn’t mean everybody’s well is going dry, but there are significant differences in the last 10 years.”

For example, Ellenburger-San Saba monitoring well No. 4042 indicates water levels are currently at about 51 feet below surface, which is close to its all-time low of 52.5 feet below surface reached in 2011. For comparison, the well fluctuated in the mid-30- to 40-foot-below-surface range for most of the past 14 years, only dipping below 50 feet occasionally. While this shows an overall historical low, it does not show how deep the aquifer actually goes, so the total water available is still unknown. That makes it difficult to determine how severe the groundwater fluctuations are, Davis said.

The district is taking steps to collect more data, funding a joint project that would help map a portion of the Trinity Aquifer beneath Burnet County. The information could give valuable insight into the total water available and the impacts of groundwater use and climate change. A group of county stakeholders appointed by the district’s board told directors they would like to see more data collection on groundwater supplies. Directors recently approved a slight increase to the district’s 2023-24 fiscal year tax rate to fund the requested studies.