Col. Jason Kirk of the U.S. Army Corps of Engineers says the pulsing water flows will simulate rainfall. By varying the flows, they hope to reduce environmental problems.
Kirk says they need to flush the lake to reduce flood risks as water levels rise. Its aging dike was built after flooding unleashed by two catastrophic hurricanes killed thousands of people in the 1920s.
Coastal communities say previous discharges spread toxic algae, threatening tourism and health. Both Republican and Democratic political candidates are making the discharges a campaign issue.
The Trump administration has approved a new reservoir to store more water south of the lake, but it awaits passage in Congress.
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