As the clouds begin to darken and the thunder starts to rumble in the distance, the bison and longhorn herds at San Angelo State Park become restless. The first drops of rain begin to hit the parched landscape surrounding the U.S. Army Corps of Engineers, Fort Worth District’s O.C. Fisher Dam and Lake as the storm rolls in.
Construction of the rolled-earth-filled dam began in May 1947 with deliberate impoundment to create the lake beginning in February 1952. Five years later, on Oct. 14, 1957, the lake set its record level of 1,916.47 feet above mean sea level. Since then, lake levels have consistently dropped, but four exceptions across the intervening years have proven the continued value of the lake to San Angelo and other communities along the Concho River basin.
“After multiple large flood events in the 1920 and 30s in the Colorado River basin, a public meeting was held in 1936 to assess the need and community desire for a dam to protect San Angelo,” said Simeon Benson, a hydraulic engineer with the Fort Worth District’s reservoir control division. “When the dam was authorized by the Flood Control Act, it was designed for the maximum possible rainfall in two and a half days. This was a conservative estimate, but one based on the regional storms observed in the past decades.”
Although there hasn’t been a major storm in the area in more than a decade, the threat of storms is ever-present, and hurricanes continue to form that could send a deluge of rain to the area any given summer.
“The last major storm and high-water mark came in May 2015,” said Brian Phelps, the deputy chief of operations for the Fort Worth District. “O.C. Fisher Dam prevented an estimated $5 million in damages to the local area during this storm alone.”
From the first shovel of earth turned during the groundbreaking until today, the primary mission of the dam has been to provide flood risk management to the North Concho River and other areas of the Concho River watershed and Colorado River basin. It has served that purpose for more than 70 years and five major rain events.
“As of fiscal year 2023, the cumulative estimated amount of damages prevented by the dam during rain events is $21.3 million,” Phelps said.
Although the dam and lake may never again be at the top of conservation pool, it will remain as a guarding wall for the people of San Angelo and those downstream.
“Most of the time, San Angelo is dry,” said James Thompson, lake manager for O.C. Fisher and Hords Creek lakes. “But in 2015, the lake went up 22 feet overnight. The North Concho River coming into the lake overflowed its banks and there was debris in the north unit of Bald Eagle Park. That’s the type of situation that the dam is built to handle.”