April rains nearly fill lakes Buchanan and Travis
Thanks largely to significant rainfall near Pecan Bayou in the upper basin, inflows into the Highland Lakes in April were almost double the monthly average and totaled 200,741 acre-feet. Inflows are the amount of water flowing into the lakes estimated from measurements at four gauges upstream.
Water flowed into lakes that were already full or nearly full, prompting LCRA to release floodwaters through the chain of dams that form the Highland Lakes. In April, LCRA opened floodgates at Buchanan, Wirtz, Starcke, Mansfield and Tom Miller dams to manage floodwaters. The last time flood operations occurred at Buchanan and Mansfield dams was 2007.
Lakes Buchanan and Travis – the region’s water supply reservoirs – together rose slightly from 96 percent of capacity for water supply purposes on April 1 to 97 percent of capacity on May 1.
Lake Buchanan reached 1,017.7 feet above mean sea level (feet msl), or 94 percent full, the highest elevation for the lake since May 2008. (LCRA currently is maintaining Lake Buchanan at or below 1,018 feet msl. Learn more.)
Lake Travis hit 682.7 feet msl on May 1. The lake was 100 percent full for water supply purposes, and additionally, held about 32,000 acre-feet of water in its flood pool.
Of the six Highland Lakes, only Lake Travis – formed by Mansfield Dam – is designed to hold floodwaters. Lake Travis can capture and hold an additional 787,000 acre-feet of floodwaters in its flood pool after the lake is considered full for water supply purposes.
“The Highland Lakes are working exactly as they were designed to work,’’ said John Hofmann, LCRA executive vice president of Water. “During the recent flooding rains, Lake Travis temporarily held floodwaters in its flood pool to allow downstream flooding to recede before moving the floodwater downstream.”
During floods, LCRA operates the Highland Lakes dams to protect Austin and reduce flooding impacts from the Colorado River on Austin and other downstream communities.
In addition to managing floods, the Highland Lakes also were created to capture water when it rains to ensure the region has a reliable water supply during dry times. Lakes Travis and Buchanan provide the water supply for more than a million people, as well as industries, businesses, the environment and agriculture in the lower Colorado River basin.
LCRA is managing lakes Travis and Buchanan under a state-approved Water Management Plan, approved by the Texas Commission on Environmental Quality in November 2015. The plan better protects the water supply for firm customers – mainly cities and industrial users – and enables LCRA to more quickly adapt its operations in response to drought conditions.
Under the Water Management Plan, Highland Lakes water will be available for all interruptible water users this year for the first time since 2011. If needed, water from the Highland Lakes would be released gradually and only to the extent the needs for irrigation cannot be met with the natural flow of the Colorado River. Read a fact sheet and frequently asked questions on Highland Lakes water releases for agricultural irrigation in 2016.
As of early May, no water from the Highland Lakes has been released for downstream agriculture this year.
“With a wet spring, our downstream customers’ needs have been met with rainfall and the natural flow of the river,” Hofmann said. “Some water from the Highland Lakes could be released later this summer for a second crop, depending on conditions this summer.”