One dam on the Brazos River was designed to hold back massive amounts of floodwater collected in the northern half of the watershed before being safely released to travel south toward the Gulf of Mexico.
Lake Whitney, a reservoir created over half a century ago, continues to help save the lives and property of those downstream as a flood-control reservoir while also storing water to meet area supply needs. The ability to store water supply is particularly good during drought conditions, such as those the basin has faced for several weeks.
Many Texans are provided with water by a network of reservoirs spread over the Brazos River watershed.
The creation
Located about 30 miles northwest of Waco and 65 miles southwest of Fort Worth, Lake Whitney is one of eight reservoirs owned and operated by the U.S. Army Corps of Engineers. The lake is also one of 11 reservoirs that make up the Brazos River water delivery system. The other three lakes are owned and operated by the Brazos River Authority: Lake Granbury, Lake Limestone, and Possum Kingdom Lake.
On the Brazos and Nolan rivers off Texas Highway 22, Lake Whitney has a 23,500-acre surface area and a maximum depth of 108 feet. The U.S. Army Corps of Engineers created the reservoir by damming the Brazos River in 1951, producing more than 225 miles of shoreline.
The lake, adjacent to Lake Whitney State Park, was originally authorized by Congress in 1941. However, when the U.S. entered World War II, funding was reallocated toward war efforts, according to the Corps of Engineers website. The Flood Control Act of 1944 again authorized construction. A powerhouse was added in 1953 to produce hydroelectric power. So, while the original mission of Lake Whitney was and still is for flood control, it houses water supply, produces hydroelectric power, and is a popular recreation destination.
The BRA leases water supply storage space from the federal government in Lake Whitney, as well as lakes Proctor, Aquilla, Belton, Stillhouse Hollow, Georgetown, Granger, and Somerville. Each of these flood-control reservoirs has a “conservation pool” where water supply is stored.
Providing water
The water in Lake Whitney is divided into different layers. The bottom half of the reservoir is water dedicated to the powerhead pool. The middle 230,000 acre-feet of water is considered the conservation pool. The BRA holds a permit for 22% of the storage from the conservation pool or about 50,000 acre-feet of water, a relatively small part of this large reservoir. (For reference, one acre-foot is 325,851 gallons of water.) BRA’s permitted water storage in Lake Whitney is less than 10 percent of the reservoir’s capacity at its normal operating level. The remaining water supply within the conservation storage is used for hydroelectric power generation. The Southwestern Power Administration contracts with Brazos Electric Power Cooperative to dispatch hydropower at the dam.
As a result of the hydropower operations, there is typically more coordination between agencies when water is released from the federally-owned reservoir in Central Texas than needed at other projects in the basin, said BRA Senior Hydrologist Chris Higgins. If water is being released, for example, to meet hydropower needs, that puts water in the lower Brazos River that might have been needed through a water supply release from the BRA, and vice versa, he said.
The BRA is charged with managing much of the Brazos River basins’ water supplies, ensuring water is available to those in need. The watershed from Lake Whitney to the Gulf of Mexico is considered the lower basin. Within this area, many cities and industries depend on that water, including the Gulf Coast Water Authority, which serves three lower basin counties, and industries such as NRG Texas and Dow Chemical, which rely upon water from the main stem of the Brazos River.
The BRA regularly coordinates with those customers in the lower basin, the Corps of Engineers, and the Texas Commission on Environmental Quality Brazos Watermaster’s Office to determine if water needs to be released to meet the demand, Higgins said. When water must be released from reservoir storage, experts must determine which reservoirs to release water from, how much to release and when the releases need to be made. Part of this involves analyzing the supply, demand, streamflow, weather forecasts, evaporation rates, channel losses, and so much more.
“100% of that water isn’t going to make it,” Higgins said. So we actually need to release more than the requested amount to account for the channel losses. On any given day, any given second, the channel losses could be much more or much less than the numbers we’re using. These are averages we’ve developed over time. Trying to guess how much water is really being lost is impossible. It’s an unsolvable problem. So, we use the best we have and adjust releases as needed as we progress through the drought to ensure the customer’s demands are being met.”
“This coordination is vital to ensure that the water supplies of the Brazos River basin are managed in the most efficient manner possible,” Higgins said.
Floods and droughts
Water released from Lake Whitney can take about eight days to travel the Brazos River and reach the Richmond area and a total of around 11 to 12 days to reach the Gulf, Higgins said.
Of course, there are years that no water needs to be released from Lake Whitney to meet the demand of those in the lower basin, Higgins said. Between rainfall amounts, conservation efforts, and use, sometimes the rain that falls in the area is enough to meet those needs.
“As a water supply operator, we desire for our reservoirs to be as full as they can be,” Higgins said. “That way, when we do hit a drought situation, we have the optimal amount of water available to use. You never know how long a drought is going to last once you enter it. The next drought could be the drought of record. You never know.”
Since BRA-owned reservoirs cannot store floodwaters, once Possum Kingdom Lake or Lake Granbury become full and continue to see inflows, water can be released downstream to be captured by Lake Whitney. The reservoir can then hold the floodwater until it is safe to release the inflows downstream.
Higgins said he’s never experienced a time when Lake Whitney’s flood pool maxed out. Lake Whitney’s flood pool is large enough to hold the water from Lake Granbury being filled and emptied 11 times, he said.
Lake Whitney is typically considered ahead of most other reservoirs with the BRA water supply system when there is a need for water supply.
“It has a very small amount of local demand,” Higgins said. “Unlike Lake Granbury, for instance, has a significant amount of demand that relies on the storage from the perimeter of the lake itself. If we use the water at Lake Whitney, we’re not depleting someone local.”
Lake Whitney plays an intricate role in the Brazos River basin with the help of the strong partnership maintained between the BRA and the Corps managing the floodwaters and water supply throughout the basin.