This in Canyon Lake in the Texas Hill Country, halfway between Austin and San Antonio. I watched it being built in the early 1960's. Its 8,230 acres big and at normal water levels it is 134 feet deep. The water is so cold coming out the discharges at the bottom of the lake, down the Guadalupe River, rainbow and brown trout can survive in it.
In 2002 the area received over 30 inches of rain in <30 hours and the earthen spillway around the dam at Canyon Lake cut out, exposing Cretaceous age Glen Rose Reefs and the Upper Trinity limestone. When flood waters receded the ensuing spillway gorge laid forth beautiful secrets that can still be seen today by visiting the new gorge park.
I've sat a few Permian Basin frac's before, know frac engineers, have buddies working in that stuff and have a good handle on how much fresh to semi-fresh (potable) water is used in the Permian Basin each year to frac over 5,000 wells. It's pretty much all groundwater. From an arid, hot part of Texas that averages 15 inches of rain a year.
Completing over 5,000 HZ wells in the Permian Basin uses close to 126,000,000,000 (billion) gallons of water every year. It's hard to get your head wrapped around that big a number, so try this...
The volume of water used for frac'ing that number of Permian wells, in acre feet (386,000), would drain Canyon Lake (382,000) dry...every year.