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Continued drought prompts changes in water supply releases

Continued drought prompts changes in water supply releases

Lake Limestone's water level will continue to decline as the reservoir fulfills its purpose and begins releasing to meet the water supply needs of those downstream. 

Releases will begin Sept. 1 and are expected to continue through the end of September, depending on streamflow conditions, water supply needs and the weather. The Lake Limestone Sterling C. Robertson Dam will go from releasing 6 cubic feet per second (cfs) to 185 cfs. Lake Limestone is located on the upper Navasota River in Limestone, Robertson and Leon counties.  As of August 31st, Lake Limestone’s lake level sits at around 2.5 feet below the top of conservation pool elevation of 363 feet above mean sea level or about 85 percent full.  With continued lack of rain, high temperatures, and water use, the lake level has declined from its full level down to its current lake level over the last 3 months.

The lake level is expected to drop about 2.5 feet by the end of September, of which, 1.1 feet will be a direct result of the water supply release. Worst case scenario, if there is high evaporation, low inflows, and lakeside demands, in addition to the downstream release, the lake could drop to around 5 feet below the top of conservation by the end of September. Like the other 10 reservoirs with the BRA system, Lake Limestone is a water supply reservoir and will fluctuate with supply use and weather conditions.

“In order to see substantial benefits in reservoir storage and changes in the drought status, we will need to see large-scale changes in the weather pattern in Texas that will bring much above normal rainfall for multiple weeks to months,” said Aaron Abel, Brazos River Authority water services manager. 

While Lake Limestone is not currently at or below its Stage 1 Drought Watch trigger, the entire Brazos River Authority Water Supply System is under a Stage 1 Drought Watch. The BRA's Drought Contingency Plan has four conditions, or stages, ranging from 1-4 in severity. Each stage is tied to a corresponding reservoir level, storage, or when appropriate, the Palmer Hydrologic Drought Index (PHDI) level.

Lake Limestone is part of a system of reservoirs designed to meet the water supply needs of the Brazos River basin. As of late, downstream water supply needs have been met via releases from Lakes Somerville and Whitney. 

Lake Somerville could drop an additional 1.8 feet by the end of September.  Under worst-case conditions, Lake Somerville’s elevation could be around 6 feet below the top of conservation at the end of September. Lake Somerville is currently under a Stage 1 Drought Watch condition.

Should continued water supply releases be needed by the end of September, other BRA System reservoirs may be needed to release water. Those reservoirs include lakes Possum Kingdom and Granbury. 

The BRA reminds everyone that the decline in the lake level is not related to the project to replace the Sterling C. Robertson Dam's gates. While under construction, crews will use a "stoplog," a hydraulic engineering control much like a temporary wall, to keep the water from flowing downstream once the old gate is removed. The level of the lake will not be lowered for construction. The project will be completed at whatever the lake elevation is over the next couple of years, given flood or drought conditions. Replacement of the gates and other rehabilitation work will help ensure the structure's longevity. Read more about that project here.

The BRA continually monitors weather forecasts, streamflow, and lake levels throughout the Brazos River basin. All Brazos River Authority system reservoirs are under some level of drought declaration as defined in the Drought Contingency Plan. Those lakes include Proctor, Belton, Stillhouse Hollow, Possum Kingdom, Granbury, Limestone, Georgetown, Whitney, Aquila, Granger, and Somerville.  

As of Aug. 30, 2023, the entire BRA water supply system of 11 reservoirs were under Stage 1 Drought Watch.  Additionally, three reservoirs have reached their individual trigger elevation for Stage 1 Drought Watch: Lakes Aquilla, Granger, and Somerville.  Meanwhile, three reservoirs are under a Stage 2 Drought Warning: Lakes Belton, Stillhouse Hollow and Georgetown. Lake Proctor is under a Stage 4 Pro-rata Curtailment. 

It will take a string of rainfall events to saturate the soils and finally initiate runoff so that we may begin to see meaningful inflows into the reservoirs and lake level rises within the BRA water supply system.
A copy of the Brazos River Authority's Drought Contingency Plan can be found here or by contacting the BRA at (254) 761-3100.

For biweekly video drought updates on the basin, go here.

For more information on how you can conserve water go here


 

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