LCRA operates six hydroelectric dams on the Highland Lakes of central Texas. Wirtz Dam, at what used to be called Granite Shoals, backs uip water to create Lake LBJ. Five of the 6 LCRA dams were built for the primary purpose of making hydroelectric power. Although all LCRA dams can manage floodwaters, only Mansfield Dam, downstream at Lake Travis, was to hold back floodwaters.
From the LCRA website: (
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"LCRA dams form the Highland Lakes
Structures designed for flood management, water supply, hydroelectricity
LCRA operates six dams on the lower Colorado River in Central Texas: Buchanan, Inks, Wirtz, Starcke, Mansfield and Tom Miller. These dams form the six Highland Lakes: Buchanan, Inks, LBJ, Marble Falls, Travis and Austin.
Flood management
Each of the dams was built to manage floods, but Mansfield Dam, which forms Lake Travis, is the only one designed to hold back floodwaters.
. . .
Electricity
The dams in the Highland Lakes chain have hydroelectric generation stations that contribute to the Central Texas energy supply. Together, the hydroelectric plants at the dams can provide more than 295 megawatts of electricity per year.
Hydroelectricity was once the major source of power for LCRA's electric service area, but hydroelectric generation now is primarily a byproduct of other river operations. Water is moved through hydroelectric generation solely to create power at the request of the Electric Reliability Council of Texas during a power emergency.
From the Wirtz Dam page: (
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Wirtz Dam and Lake LBJ
Lake provides cooling water for nearby power plant
Once named Granite Shoals
Wirtz Dam was built from 1949 to 1951 primarily to provide additional hydroelectric power. It was built in tandem with Starcke Dam downstream. Lake LBJ provides cooling water for LCRA's Thomas C. Ferguson Power Plant along Horseshoe Bay.
The dam and lake originally were called Granite Shoals. The dam was renamed in 1952 for Alvin J. Wirtz who was instrumental in LCRA's creation and served as its first general counsel. The lake was renamed in 1965 for another advocate of LCRA, President Lyndon B. Johnson.
FYI: Wirtz Dam
Location: Llano and Burnet counties, 387 river miles from the Gulf of Mexico
When built: 1949 to 1951
Dam dimensions: 118.3 feet high, 5,491.4 feet long
Primary purpose: Hydroelectric power, cooling water for Thomas C. Ferguson Power Plant
Generating capacity: 60 megawatts
Top of dam: 838 feet above msl
Floodgates: 10
Discharge capacity: 317,400 cubic feet per second (cfs):
10 floodgates @ 30,800 cfs each
2 turbines @ 4,700 cfs each
Original name: Granite Shoals Dam
Details on Lake LBJ
Lake area: 6,275 acres
Lake elevation when full: 825 feet above mean sea level (msl)
Volume when full: 133,216 acre-feet
Historic high: 836.2 feet above msl on Sept. 11, 1952
Historic low: 793.8 feet above msl on Nov. 16, 1970
Target operating range: 824.4 feet to 825 feet above msl
100-year flood level at dam: 828.1 feet above msl
Dimensions: 21.15 miles long and 10,800 feet at widest point
Original name: Lake Granite Shoals"