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 Reliant Energy) 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 right 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. The resulting joint project between the City of Houston, the BRA and the TWDB allows the sharing of cost 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. The BRA will build and operate the reservoir.
Once completed, water will be pumped into Allens Creek Reservoir from the Brazos River during periods of high streamflow. The water supply may 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 subsidence in the Houston area.
The reservoir will provide 95,000 - 100,000 acre-feet of water per year of firm water supply -- the annual water use of over 150,000 families. The cost to build the reservoir is estimated at $300 million in 2016 dollars.
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.