USGS Water-Year Summary for Site 08131200

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	62614 Elevation, lake/res, NGVD29(Max.,Min.,Mean)

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Water year 2023: 2022-10-01 to 2023-09-30

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USGS Water-Year Summary 2023

08131200 Twin Buttes Reservoir near San Angelo, TX

LOCATION - Lat 31°22'55", long 100°32'17" referenced to North American Datum of 1927, Tom Green County, TX, Hydrologic Unit 12090102, in outlet control tower near left end of Twin Buttes Dam on Middle Concho River, Spring Creek, and South Concho River, 3.8 mi upstream from Lake Nasworthy Dam, 8.1 mi southwest of San Angelo, and 75.0 mi upstream from mouth.

DRAINAGE AREA - 3,868 mi² of which 1,055 mi² probably is noncontributing.

REVISIONS HISTORY - WDR TX-81-3: Drainage area.

SURFACE-WATER RECORDS

PERIOD OF RECORD - Oct. 1962 to Sept. 2003 (contents), Oct. 2003 to current year. PERIOD OF RECORD, Water-Quality.-- CHEMICAL DATA: May 1965 to Nov. 1966 and July 1970 to Apr. 1984. BIOCHEMICAL DATA: May 1965 to Nov. 1966 and July 1970 to Oct. 1973.

GAGE - Water-stage recorder and nonrecording gage on Middle Concho-Spring Creek pool and nonrecording gage on South Concho pool. Datum of gage is NGVD of 1929. To obtain elevations in NAVD88 add 0.48 ft. to NGVD29 values. Satellite telemeter at station.

COOPERATION - Texas Water Development Board (TWDB).

REMARKS - The reservoir is formed by a rolled earthfill dam 8.1 mi long, including a 200-foot-wide uncontrolled off-channel concrete gravity spillway with ogee weir section. Outlet works consist of three 15.5-foot concrete conduits, each controlled by a 12.0- by 15.0-foot fixed-wheel gate and a 12.0- by 15.0-foot radial gate, located in the Middle Concho-Spring Creek pool. Low-flow releases are made through 2.0- by 2.0-foot gates located in the center of three fixed-wheel gates. Records of diversion can be obtained from the City of San Angelo, Texas. The South Concho and Middle Concho-Spring Creek pools are connected by a 3.22-mile equalizing channel. At a South Concho pool elevation of 1,926.5 ft., the two pools join to form one lake. Lake level elevations below 1,926.5 ft. represent Middle Concho-Spring Creek pool only. Deliberate impoundment of water began on Dec 1, 1962; dam was completed Feb 13, 1963. In June 1999, construction of a cutoff wall to stop seepage was completed. Capacity curve is based on a survey made in 1958. Reservoir is owned by the city of San Angelo and was built for flood control, irrigation, and municipal uses. Data regarding dam features were provided by the U.S. Bureau of Reclamation, have not been validated by USGS personnel, and are given in the following table in NGVD29 elevations:

                                                                              Elevation (feet)
Top of dam...........................................................         1,991.0
Crest of spillway....................................................         1,969.1
Top of conservation storage..........................................         1,940.2
Bottom of equalizing channel (Middle Concho-Spring Creek pool).......         1,926.5
Dead storage in South Concho pool....................................         1,926.5
Lowest gated outlet (invert at Middle Concho-Spring Creek pool)......         1,885.0

EXTREMES FOR PERIOD OF RECORD - Maximum contents, 205,200 acre-ft, May 12, 1975, elevation, 1,942.20 ft; minimum since first appreciable storage (period of daily mean contents), 2,120 acre-ft, Apr. 15, 1971. Minimum elevation, 1881.03 ft., Nov. 09, 2013.