Proposed reservoir will benefit everyone in the Brazos basin

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The proposed Allens Creek Reservoir has been included in Texas' State Water Plan for decades. With population growth across the state expected to increase by 73 percent between 2020 and 2070, the water that this proposed off-channel reservoir will supply is needed to allow portions of the state to continue to help meet the needs of the growing population.

But it will also help to alleviate stress on other basin water supply reservoirs.

Planned for the lower Brazos basin in Austin County between the towns of Sealy and Wallis, Allen's Creek Reservoir was initially permitted by the state to serve as a cooling lake for a nuclear power plant. That plan was abandoned in the 1970s and in the late 1990s, the property was purchased by the Brazos River Authority and then-partners, the Texas Water Development Board and the City of Houston. The Texas Legislature then directed the state to reissue the water right to the BRA, the city of Houston and the Texas Water Development Board as a water supply reservoir.

Over the 20 years following the purchase, population studies included in the state plan have shown that growth rates will vary considerably throughout the state. Still, about half of the statewide expansion will occur in and around the Dallas-Fort Worth and Houston areas. The suburban sprawl from both cities will spill into areas served by the Brazos River Authority supply system.

The proposed reservoir has been on hold for the past decade.

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As the city of Houston pursued other water supply projects to meet its needs, growth continued in the Brazos River basin. The BRA proposed negotiations with the city to move the project forward, later passing legislation and litigating the issue.

On May 2, the process was completed with the BRA purchasing the Allens Creek property and reimbursing the city for loan payments. Houston will also have the right to contract for water supply once the reservoir is complete.

The BRA is moving forward with the extensive process of building the reservoir. The 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 process and preliminary engineering. It is estimated that the permitting process could take between 5-10 years. Final engineering design and the actual construction phase of the reservoir will begin after all applicable permits are obtained and could take an additional 4-7 years. Construction is not expected to begin until 2030 at the earliest.

Unlike the Bois d'Arc Reservoir and the Ralph Hall Reservoir, the two newest large lakes to be developed in Texas over the past 30 years, obtaining property rights for the reservoir is not necessary.

"The 9,500 acres set aside for the reservoir were purchased from the former Houston Lighting and Power (now NRG)," said Brad Brunett, BRA lower and central regional manager. "For the past 20 years, the property has been leased to local farmers for crop production and ranching purposes. That will continue until we get closer to construction."

Unlike other reservoirs within the Brazos River Authority system, Allens Creek Reservoir will be constructed as an "off-channel" lake. Technically speaking, it will be constructed on Allens Creek, a very small tributary of the Brazos River, but the primary source of water will be pumped into the lake 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.

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Allens Creek Reservoir is expected to provide about 100,000 acre-feet of firm water supply per year -- the annual water use of about 260,000 families. The added supply will help meet the anticipated growth of the lower Brazos basin, relieving supply needs from upper basin reservoirs.

"The Brazos River Authority's water supply is held in reservoirs that function as a system rather than 11 stand-alone storage facilities," said Brad Brunett, BRA lower and central basin regional manager. "Now, when supply is needed in the lower portion of the Brazos basin, the BRA releases water from a reservoir further upstream to meet those needs. Adding Allens Creek Reservoir to the system will provide water stored closer to where it's needed in the lower Brazos basin. This allows the water to reach its destination sooner and allows water to remain stored for use in the central and upper reaches of the basin."

It is expected that public use opportunities will be available to the general public. However, because the reservoir's primary purpose will be for water supply, there will be periods when water levels will fluctuate significantly, particularly during times of drought.

The cost to build the reservoir is estimated at about $500 million.