Allens Creek Reservoir is a proposed pumped-storage water supply reservoir planned for construction near the City of Wallis in Austin County near the confluence of Allens Creek with the Brazos River. The reservoir will be filled by water pumped from the Brazos River for storage when river flows are adequate and will be available to supply downstream customers when supplies are needed.
A permit to build the reservoir was originally issued to Houston Lighting & Power Company (HL&P – a predecessor of NRG) in 1974 to provide cooling water for a proposed nuclear power plant. The power plant was not built, and eventually, HL&P allowed the water rights permit for the reservoir to expire. Later, the Texas Legislature passed Senate Bill 1593, allowing the Texas Commission on Environmental Quality (TCEQ) to grant a water right for Allens Creek Reservoir to the Texas Water Development Board (TWDB).
The Brazos River Authority and the City of Houston purchased the 9,600-acre Allens Creek Reservoir site from Reliant Energy in 2000. The resulting joint project between the City of Houston, the BRA and the TWDB planned to allow the sharing of costs to build the reservoir and the water supply yield on a 70 percent (Houston) and 30 percent (BRA) basis. The purchase was made possible through financing provided by the TWDBs State Participation Program. Under this agreement, the BRA would build and operate the reservoir.
For several years, the reservoir project was on hold. However, due to the increasing need for water supply in the Brazos River basin, the Brazos River Authority purchased full rights to the reservoir from the City of Houston and the Texas Water Development Board in May 2022 and is now the sole developer/owner of the reservoir project.
The Allens Creek Reservoir project will be undertaken in multiple phases, including permitting, design, and construction. Reservoir projects have unique considerations and characteristics that require years of work to support the permitting and design efforts prior to construction. It is estimated that the total time for all phases of the project could be more than 10+ years, with a majority of that time dedicated to the permitting and design process. We are still many years out from construction and can only start construction activities after all applicable permits are issued.
The permitting and design process will involve evaluation of all aspects of the project and any potential impacts that it will have on flooding, the environment, cultural and historical resources. Negative impacts that are identified through this process will be mitigated, or the project configuration will be adapted to avoid or minimize the impacts. Public involvement will be a part of the process.
Water stored in Allens Creek Reservoir will be used to meet the anticipated growth in demand for surface water in the Lower Brazos basin due to projected population increases. The reservoir will also help satisfy regulatory requirements to reduce groundwater pumping, which contributes to land subsidence in the lower Brazos River basin.
Allens Creek Reservoir is expected to provide about 100,000 acre-feet of water per year of firm water supply -- the annual water use of about 260,000 families. The cost to build the reservoir is estimated at $700 million.
Swimming, boating, and fishing facilities may be available to the general public. However, because the reservoir's primary purpose will be for water supply, there will be years that the water levels will fluctuate significantly. Water levels in Allens Creek Reservoir will not be constant and will vary greatly, particularly during times of drought. The reservoir's primary benefit to the citizens of Texas is to provide water for municipalities, industry, agricultural producers, and electric energy generators.