Less rainfall, lake releases contribute to low lake level

WEST PALM BEACH — A number of factors contributed to the current low level in Lake Okeechobee this year. During the 2018-2019 dry season, the U.S. Corps of Engineers intentionally released water east and west with the intent of lowering the lake to help the lake’s vegetation recover from the effects of Hurricane Irma. They expected the 2019 wet season to refill the Big O. But Mother Nature did not comply, and the lake started the dry season at just 13.38 feet above sea level. The optimum level for the start of the dry season is 15 feet according to the RECOVER report for Lake Okeechobee. (RECOVER — which stands for REstoration COordination and VERification — is a multi-agency team of scientists, modelers, planners and resource specialists who organize and apply scientific and technical information in ways that are essential in supporting the objectives of the Comprehensive Everglades Restoration Plan.)

During Water Year (WY) 2020 (May 1, 2019 to April 30, 2020) the lake received about 400,000 acre-feet less than in WY 2019, according to the report presented at the May 14 meeting of the South Florida Water Management District (SFWMD). That’s about 112 billion gallons; one foot of water on Lake O is about 144 billion gallons.

SFWMD Chief Engineer John Mitnik said the marshes are very dry, which can impact the fish and wildlife populations. “When we get to 12 feet, the marsh is very dry,” he explained. “If we don’t refill the marsh annually, we will have a change in composition of vegetation.” This will deplete the opportunity for the prey bait to build back up, leaving less food for wading birds. When the lake is this low, it also becomes more difficult to send needed water the Caloosahatchee River, he explained. Sometimes wind conditions make it impossible to release more water from the lake to Caloosahatchee estuaries.

On May 25, Lake Okeechobee was at 11.14 feet. For the seven-day period ending May 25, flow at the Franklin Lock River averaged 829 cubic feet per second, with most of that water coming from local basin runoff. Flow into the river from the lake at Moore Haven averaged 163 cfs. Meanwhile, water from the C-44 basin was backflowing into the lake at Port Mayaca at 156 cfs on May 25, and averaging 72 cfs for the week. When the lake is low, if the water control structure at Port Mayaca is open, water from the C-44 basin backflows into Lake Okeechobee.

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