Corps hopes to lower lake level before Hurricane Irma hits; Water still backflowing into the lake at Port Mayaca

As Hurricane Irma makes its way across the Atlantic, the U.S. Army Corps of Engineers Jacksonville District has begun a pre-storm drawdown that includes water releases from Lake Okeechobee.

Reaching the target flows for lake releases may depend on the level of water in the canals. Some releases depend on gravity flow.

On Tuesday, the Corps set the target flow for the Caloosahatchee Estuary at 4,000 cubic feet per second (cfs) as measured at Moore Haven Lock (S-77) located in the southwest part of the lake. On Wednesday as of 11:30 a.m., the flow was at 932 cfs. Prior to Sept. 5, no lake water had flowed through that lock since the start of the wet season.

During the dry season, some flow from the lake was sent to the Caloosahatchee in order to prevent saltwater intrusion.

The target flow for the St. Lucie Estuary was set at 1,800 cfs on Tuesday as measured at St. Lucie Lock (S-80) near Stuart. Additional runoff from rain in the St. Lucie basin could occasionally result in flows that exceed targets.

No water from the lake has flowed into the St. Lucie this year. Water from the C-44 canal has been backflowing into the lake since the start of the rainy season. More than 24 billion gallons of water from the St. Lucie basin has backflowed into the lake since June 1.

The Sept. 6, 11:30 a.m. update of Corps website showed water was still backflowing into the lake at Port Mayaca at 224 cfs. Flow into the estuaries at the St. Lucie lock was 468 cfs – all of that water was basin runoff.

“We want to be ready for the heavy precipitation from Irma,” said Col. Jason Kirk, Jacksonville District Commander. “We anticipate direct rain over the lake could add a foot to the water level. We’ve seen basin runoff from past events cause the lake to rise three feet over the span of a month. We want to do all we can to ensure we have as much storage as possible for Irma.

On Tuesday, the lake stage was 13.67 feet.  On Wednesday at 11:30 a.m. the lake was slightly higher at 13.68 ft.

The Corps anticipates the releases will last a short time, with future water management decisions dependent on the water level in the lake after the storm passes.

“We will only be able to release water for about three days at these rates,” said Col. Kirk on Tuesday. “As the storm gets closer, we’ll have to close all the gates around the lake to reduce the risk from potential storm surge that may develop from high winds on the lake.”

The Corps continues to closely coordinate its water management activities with the South Florida Water Management District. For more information on water level and flows data for Lake Okeechobee, visit the

Corps’ water management website at http://www.saj.usace.army.mil/Missions/CivilWorks/WaterManagement.aspx.

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