The year was 1938 and construction was set to begin on the first dam ever to exist on the Brazos River.
Unemployment was high nationwide, a lingering effect of the Great Depression. Franklin D. Roosevelt was president, “Gone with the Wind” was released, and radio was the primary source of news, entertainment, and music. At the time, computers were still in their early stages of development; room-sized machines not yet accessible to the general public.
And the state of Texas authorized a permit to the Brazos River Conservation and Reclamation District, later renamed the Brazos River Authority, to build a dam in Palo Pinto County, Texas. Built in response to disastrous Brazos River flooding, the dam and resulting reservoir were early attempts at water conservation and flood control in Texas.
With the aid of the Works Progress Program, by 1941 the project was complete. Possum Kingdom Lake became the first reservoir built by the Brazos River Conservation and Reclamation District, now the BRA. The work was an accumulation of more than a decade of planning efforts to tame a river that historically claimed hundreds of lives with flash flooding and made water supply efforts difficult at best due to periodic extreme drought conditions.
The gates at Morris Sheppard Dam are a testament to the ingenuity of past engineers.
Morris Sheppard Dam is operated manually. While modern technology has advanced significantly, the manual operation of these gates is like stepping back in time, offering a tangible connection to the history of dam engineering. It’s something that now sets apart the dam from the BRA’s other two structures: Lake Granbury’s DeCordova Bend Dam and Lake Limestone’s Sterling C. Robertson Dam.
The Possum Kingdom Lake dam is 190 feet high and 2,700 feet long, which is the length of about 180 cars. The dam has nine steel roof weir-type gates, also known as bear-trap gates due to their design. Each gate is about 74 feet long and 13 feet high.
Unlike the newer dams, which can use a remotely operated computer to move the gates, these gates are operated manually using pressure from lake water to help them open and close, just as they were when the dam was originally built.
The gates are designed to "trap" water, hence the name "bear-trap." As the gate is raised, it creates a unique water flow pattern, resembling the jaws of a bear trap.
When a gate release is expected, BRA staff begins the process. The gate chamber fills with water and the uplift pressure from the water causes the upstream and downstream leaves to float.
Once the floating status is secured, this process requires a BRA employee, attached by a tether above a 130-foot drop, to physically climb on top of the gate to unlatch a series of locking bars that secure the gate in the closed position when not in use. The gates are accessed via a catwalk that runs the length of the gates.
At this stage, the gate is “floated” and in an unlocked status.
When it’s time to open a gate, water is drained out of the gate chamber, and then the gate will collapse on top of itself, allowing water from the lake to flow out over the spillway gate, through the flip bucket, and down the river.
Because of this design, each gate can only be operated fully open or fully closed. When each gate is open, the release can be between 9,000 and 10,000 cubic feet per second per gate when the lake is full. These types of gates are rarely used in new dams because of the manual system.
On average, it takes about two hours to open a gate and about 30 to 45 minutes to close it.
Opening one of the dam’s nine spillway gates is one of three ways to release water.
The dam, which always releases some amount of water, also has three low-flow gates and two ring jet valves that have the ability to release water when smaller amounts are required.
Possum Kingdom Lake remains a vital part of life in Texas, providing water for communities, farms, and countless hours of recreation. While many dams now rely on computers and automation, the manual operation of the "bear trap" gates at Morris Sheppard Dam feels like a step back in time.