Flooding puts pressure on Texas dams

Dams in the Austin, Texas area are under pressure due to days of heavy rain. Floodgates are open at some dams in the Austin area to keep lakes from overflowing.

The Lower Colorado River Authority has already opened four floodgates at Mansfield Dam, but current overflow dictates the need to open four more floodgates by mid-Thursday, officials said on Wednesday. This means that come Thursday, a total of eight gates will be open at the dam — a record number for the structure, and the greatest number of floodgates opened simultaneously since six in 1957.

This comes after heavy rains descending on Central Texas since the beginning of the week unleashed historic flooding levels causing widespread property destruction and a handful of deaths.

As of 8 p.m. on Wednesday, Lake Travis was at 698.91 feet — well above 100 percent filled, according to the LCRA. For some context, consider this: In the 24-hour period from noon Tuesday to noon Wednesday, Lake Travis climbed 21 feet. Stated another way, more water has been captured at Lake Travis in the last week than the city of Austin typically uses in four years, officials have noted.

That calculus amounts to the need for releasing water from the man-made reservoir, and quickly. Should water exceed 700 feet — something that's never happened but now precariously close to that level — the runoff will spill over its banks, and not in the controlled manner the LCRA would undertake.

Controlled or not, lakefront residents should take precautions ahead of the water release, officials stressed.

"Releases from Lake Travis will cause higher levels in Lake Austin, Lady Bird Lake and the Colorado River downstream of Austin," LRCA officials said. "Water released from Mansfield Dam will travel down the Colorado River to Matagorda Bay."

Heightening the urgency of those warnings is the faster velocity at which that runoff will travel given its rain-bolstered mass: "Under typical conditions, water released from Mansfield Dam would take about one day to get to Bastrop, two days to Columbus, four days to get to Wharton and five-plus days to reach Matagorda," LCRA officials explained. "Travel times will be faster because we're in a flood."

LCRA opened four additional floodgates at Buchanan Dam on Wednesday morning, officials noted. This brings the total number of floodgates open at Buchanan Dam to eight, the LCRA added. And they're not done yet: "Flood operations continue at Buchanan, Inks, Wirtz, Starcke, Mansfield and Tom Miller dams," LCRA officials said. "Flows throughout the Highland Lakes are swift and high."

In preparation for the water release, LCRA has closed lakes Buchanan, Inks, LBJ, Marble Falls and Travis until further notice.

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