About Choke Canyon Reservoir
Choke Canyon Reservoir is the upper and larger half of the Corpus Christi supply system. It sits on the Frio River in Live Oak and McMullen counties, a few miles west of Three Rivers, behind a dam completed in the early 1980s. Its conservation pool holds 662,820 acre-feet when full, which is the larger share of the 918,882 acre-feet the two lakes hold together. Because it is deeper than Lake Corpus Christi and sits further from the city's intake, it functions as the storage bank of the system rather than the day to day working supply.
Two gauges upstream tell you what the Frio is bringing in. Frio near Derby sits well above the reservoir and is the earliest warning that a rise is on the way. Frio at Tilden is the closer of the two, roughly 23 river miles above the lake, and what passes Tilden is close to what the reservoir will actually receive. Choke Canyon captures its inflow directly, with no other reservoir between it and its watershed, so a storm over the Frio basin shows up here faster and more completely than the same storm shows up downstream.
The third gauge, Choke Canyon release, sits below the dam and measures the other direction: water leaving the reservoir into the lower Frio. That release is the only way Choke Canyon water reaches Lake Corpus Christi, about 11 river miles down to the Nueces confluence and another 50 to the lower lake. Releases are made for specific operational reasons rather than to keep the two lakes at matching levels, so a low or zero reading at the release gauge is a normal condition and not a sign of a problem. When people ask what the lake level is, they usually mean the surface elevation, the height of the water in feet above sea level, which is the elevation figure on the card above. Elevation figures on this page come from Texas Water Development Board daily estimates and update once a day; storage and flow come from the USGS and update through the day.