Low flow gates are tested

August 21, 2013

The Brazos River Authority (BRA) began testing the newly installed low-flow gates Monday at the deCordova Bend dam at Lake Granbury. The gates have been undergoing refurbishment for the past 20 months.

Daily release rates and volumes will vary during the testing; however, over the 30 day test period, the same volume of water will be released as would have been released for regular environmental flow needs. “The lake level will not be adversely impacted,” BRA spokeswoman Judi Pierce stated.

The Brazos River Authority has maintained a low flow release from Lake Granbury for instream flow needs downstream of the dam since the mid-1980s.

Historically, a continuous release of about 28 cubic feet per second (cfs) was maintained at the dam, which equaled about 56 acre-feet of water per day.

“During construction on the new low flow gates, the BRA has made regular daily releases of approximately 50 – 60 acre-feet by opening one flood gate for about 90 minutes,” Pierce explained.

With replacement of the low flow gates, it will no longer be necessary to release the daily environmental flow through the flood gates, and a constant low flow is expected to resume.

Over the 30 day test period beginning on Aug. 19, daily release volumes will range from about 3 to 147 acre-feet per day. The test schedule has been designed so that over the 30-day test period, the BRA will release about the same volume of water currently being released for environmental purposes.

Pierce said the testing will not affect Lake Granbury’s elevation from what it would have been in the absence of the testing.

The BRA maintains environmental flow releases from both Possum Kingdom Lake and Lake Granbury.

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