Allens Creek Reservoir is a proposed water supply storage reservoir planned for construction near the City of Wallis in Austin County. The reservoir is planned to be "off-channel," meaning it will be built near the Brazos River on Allens Creek, a tributary of the Brazos.
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 9,500-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 the past several years, the reservoir project has been 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. The sale is expected to be completed in early May 2022. The BRA will be the sole developer/owner of the reservoir moving forward.
The reservoir project will be undertaken in multiple phases, including permitting, design, and construction. The first phase will include activities to complete the required federal Clean Water Act 404 permitting prior to construction as well as preliminary engineering. It is estimated that the permitting process could take between 5-10 years. The actual construction phase of the reservoir will commence after all applicable permits are issued. Construction activities could take an additional 4-7 years after permits are issued. Construction is not expected to begin until 2030 at the earliest.
The permitting and design process will begin later this year in 2022. This 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.
Once this off-channel reservoir is completed, water will be pumped into Allens Creek Reservoir from the Brazos River during periods of high streamflow. The water supply will then be available for release back into the Brazos River to meet downstream needs during periods of low flow.
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 $500 million.
It is expected that swimming, boating, and fishing facilities will 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.