CLARIFICATION: A previous version of this story included incomplete numbers attributed to Kelly Payne. The LCRA recorded a flow of 375,000 cubic-feet per second coming into the Highland Lakes, and 25,000 cfs leaving the lakes, not 375 and 25 as written.
STAFF WRITER JARED FIELDS
A report on the Lower Colorado River Authority’s flood response given during its committee meeting Nov. 14 outlined dam operation decisions.
Kelly Payne, LCRA’s vice president of water operations, addressed questions floated since the historic Oct. 16 flood on why lakes weren’t lowered, or even emptied, as heavy inflows approached the Highland Lakes from upstream.
First, Payne addressed how floodgates drain water from the lakes.
“As the water in the lakes drops, the capacity goes down. There’s not as much driving it,” he said.
As capacity decreases, the discharge rate also goes down, and it takes longer to empty the lake.
With about a day’s notice, Payne said, the operations center decided to notify residents along lakes LBJ and Marble Falls that floodwaters were coming.
“If we started to dump (Lake) LBJ, we were not giving Marble Falls any lead time,” Payne said. “We need to be cognizant of that.”
Second, from an operational standpoint, Payne said lowering Lake LBJ too much would affect the Ferguson Power Plant. Water is needed in the lake for the plant to continue operating.
At the peak water flow rate during the flood of nearly 350,000 cubic-feet per second (cfs), Payne said the lake would have filled within hours.
“Even if we dumped the lake, in four to five hours we’d be right back where we started,” Payne said. “We would save a little bit of peak flow, but the harm that would have caused by discharging all that water was not really worth the effort to do that.”
Payne did say that lowering the lakes was “not something we ignored” but ultimately was not an option in this instance.
Board member Franklin Scott Spears Jr., who represents Travis County, commended the efforts of the operations staff.
“These guys are magicians,” Spears said.
The Oct. 16 flood began because of rains about a week prior. Rainfall on Oct. 8-10 in the Llano River basin added about 114,622 acre-feet of storage to Lake Travis. That rain also saturated the ground throughout the region, meaning that any subsequent rains would create runoff into rivers and streams.
From January through August, just over 100,000 acre-feet of water flowed into the Highland Lakes, the third-lowest total for that time period since 1942.
September’s rain created just over 110,00 acre-feet of flow into the lakes.
October’s rains dropped 1.3 million acre-feet of water into the lakes, the fourth-highest monthly total on record. Lake Travis, for example, is considered full at about 1.1 million acre-feet.
During the flood, Payne said the amount of water that entered the lakes was as much as the city of Austin uses in eight years.
Payne, in outlining the operations from dam to dam during the flood, summarized the LCRA’s response to the flood by highlighting downstream readings.
“In total, we dropped 370,000 cfs down to (24,000) to (28,000) cfs.” Payne said. “We shaved the peak. We had (375,000 cfs) coming in, (25,000 cfs) going out.”
Video of the meeting can be found on the LCRA website when it is posted.