The Lower Colorado River Authority said it will open at least two floodgates at Mansfield Dam on Saturday after torrential rains in the Hill Country filled Lake Travis to the top of its conservation pool. It’s the first time the LCRA has opened floodgates at Mansfield Dam to manage water levels since 2019.
The Mansfield Dam is one of a series of dams built across the Colorado River that form the Highland Lakes.
Lake Travis is a water reservoir formed by the Mansfield Dam. The reservoir stores the water supply for Austin and other communities. But it also acts as a flood control reservoir, impounding stormwater until it can be released more carefully downstream via floodgates.
At current lake levels, the LCRA can only open floodgates on the Mansfield Dam as long as those releases will not raise water levels on the Colorado River too much at certain points downstream.
If water levels continue to rise in Lake Travis, the LCRA is allowed to release greater amounts of water from the reservoir with fewer considerations to conditions downstream.
The first floodgate is expected to open around 6 a.m. on Saturday, and the second will open around 1 p.m., the LCRA said.
The LCRA said it also plans to open a floodgate at Tom Miller Dam, downstream of Mansfield, on Friday. That will clear the path for more water from the Mansfield Dam releases on Saturday.
Michael Minasi
/
KUT News
Water pours out of a floodgate at Tom Miller Dam.
Multiple floodgates at the Wirtz Dam and Starcke Dam, both further upstream on the Colorado River, opened yesterday and will remain open.
Opening flood gates at the Mansfield Dam is a relatively rare occurrence. But it does not signal that Lake Travis is in immediate risk of running out of space to hold flood waters.
The reservoir was built with an added amount of capacity known as a “flood pool.” That is space beyond the area reserved to hold regional water supply, which is known as the “conservation pool.”
The Lake Travis flood pool can store an additional 776,062 acre-feet of floodwaters, more water than one hundred Lady Bird Lakes.
“The flood storage is almost as much as the water supply storage at Lake Travis,” John Hofmann, executive vice president for water at the Lower Colorado River Authority, told KUT after similar flooding last year.
Still, increased flow downriver can cause problems.
The LCRA is warning that currents will be fast and water levels higher downstream of the dams.
This is a developing story.
