Reservoir water levels stabilize


FILE PHOTO: Elm Creek overflowing the low-water crossing at FM 356. Elm Creek joins the Colorado on its way to O.H. Ivie. – photo by Ken Grimm

daily volume change Twin Buttes june 2019
Daily volume change graph for Twin Buttes Reservoir, June 2019 – by Ken Grimm

June 2019 saw a record rainfall to start the month, and as illustrated in the chart of daily volume change, has been the last major inflow of water to Twin Buttes. June 3 saw 788 acre feet (256.7 million gallons) flow in, and June 4 brought 432 acre feet (140.7 million gallons).

All of the Concho Valley reservoirs have stabilized their impoundment levels from the rains that started in September of 2018. The ground saturation that has filled streams and creeks for months has tapered off.

The six Concho Valley Reservoirs are currently holding over 55% of their total combined capacity. Without significant rainfall the current reservoir levels will succumb to normal usage and the biggest drainer of reservoir resources, evaporation.

Current Concho Valley Reservoir Status

(Note: The Twin Buttes north pool is currently above the 1926.5' elevation, at which point the north and south pools are considered equalized as a single body of water. The conservation acre-feet storage capacity, used in determining the full capacity of the reservoir, is taken from the revised March 2018 tables developed by the United States Department of the Interior, Bureau of Reclamation, Great Plains Region (using 1964 tables plus 1970 USGS Survey data) for the Middle Pool, with an additional 4,602 acre-feet added to account for the additional water in the south pool.)

Reservoir Date Time Elevation
Acre-Feet Gallons Percent
Nasworthy7/4/20196:00 a.m. 1,871.29 8,306 2,706,518,406 86.39%
O.C. Fisher7/4/20196:00 a.m. 1,873.74 14,240 4,640,118,240 11.92%
Oak Creek7/4/20196:00 a.m. 2,000.04 39,460 12,858,080,460 100.64%
Twin Buttes7/4/20196:00 a.m. 1,934.62 141,070 45,967,800,570 75.65%
E.V. Spence7/4/20196:00 a.m. 1,864.92 162,400 52,918,202,400 31.40%
O.H. Ivie7/4/20196:00 a.m. 1,544.34 427,900 139,431,642,900 77.19%
Total 793,376 258,522,362,976 55.80%

San Angelo uses an average of 13,441 of acre feet of water per year, O.H. Ivie currently has 427,900 acre feet of water impounded. Over 70 months, almost 6 years, of water is available for the Concho Valley. (This estimate is a worst-case scenario assuming no other rainfall or water inputs in that time).

Monthly rainfall totals for June 2019. Illustration by Taban Sharifi

Some trivia for you: A single one-hundredth of an inch in elevation change at Twin Buttes equals 72 acre-feet (23.4 million gallons) at its current state.

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