Corps increases flow from lake to Caloosahatchee

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JACKSONVILLE – Releases from Lake Okeechobee to the Caloosahatchee River will increase from 1,500 cubic feet per second (cfs) to 2,000 cfs on Feb. 13. In a Feb. 12 meeting briefing by Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District, said the lake is about 2.5 feet higher than last year.

“We have seen some recession in the lake, but our analysis indicates we are potentially looking at starting the Hurricane Season this year with a lake around 14 feet, which increases that chance that we will  need to make releases next summer when algal blooms are more likely to be present on the lake,” said  Kelly. “Conditions in the Caloosahatchee have recovered over the past few weeks, and we believe after discussing with partners and stakeholders that this is a good time to bring flows up as long as we remain within the optimum range of flows for the Caloosahatchee.”

No lake water will be released east to the St. Lucie canal. Kelly explained releases are targeted west because the Caloosahatchee River is significantly larger than the St. Lucie River, has more capacity and needs more fresh water during the dry season.

“We are finally at the point where we can start releasing water to the south,” he continued. Currently flow south from the lake is about 200 cfs. “We anticipate as the dry season continues, that will gradually increase over time. We should be able to get more water to the south in the future.”

Areas south of the lake are still very wet, with the water conservation areas (WCAs) above schedule. On Feb. 12, WCA-2A was about a 1.5 feet above schedule and WCA-3A was 0.23 feet above schedule. Kelly said they are moving about 3,200 cfs under the Tamiami Trail. (The WCAs are north of the trail.) Kelly said water control structures S-12A and S-12B under the Tamiami Trail are closed to protect the nesting grounds of a subpopulation of the Cape Sable Seaside Sparrow. Those gates are usually closed nine months of the year. This year, due to the high water levels in the WCAs, the corps obtained a deviation that allowed them to keep the gates open. That deviation ended at the end of January.

Caloosahatchee needs freshwater flow
Kelly said the Caloosahatchee River needs freshwater flow from the lake in the dry season to prevent salinity levels from rising to harmful levels. He said 2,000 cfs, measured at the Franklin Lock, is in the beneficial flow range or “sweet spot” for salinity in the Caloosahatchee estuaries.

“We have seen some good signs ecologically in the Caloosahatchee and along the coast this week,” he said.

Flows below 450 cfs are deemed harmful because the salinity levels rise too high. Flows above 2,800 cfs are considered harmful because the salinity levels drop too low. The ideal salinity level varies for different parts of the estuaries.

Rainfall in the Caloosahatchee basin could result in higher releases than the 2,000 cfs target to the Caloosahatchee River, due to local basin runoff. The Franklin Lock is 43.4 miles from the Moore Haven Lock, where water from the lake enters the river. If there is enough basin runoff for flow to meet the target flow at the Franklin Lock, no lake water is released at Moore Haven. For the seven day average ending Feb. 12, about half of the water passing through the Franklin Lock was local basin runoff. The average flow at Moore Haven for that week was 724 cfs, and average flow at the Franklin Lock was 1,418.

More releases could be needed
Kelly said the lake’s recession rate is pretty good and they will monitor that from week to week. The preferred range for the lake level at the start of the wet season is 12 to 12.5 feet, he explained. He said based on the current trends it looks like the lake may be around 14 feet at the start of the wet season. If that happens, they may have to release water to the St. Lucie canal at Port Mayaca.

What a difference a year makes
A year ago, conditions were different, Kelly explained. Last year, they were operating in “water conservation” mode because the lake level was about 2 feet lower than it is now. Then the 2020 wet season hit.
“We were on a rapid rise the entire wet season,” he explained. Then in October the region received rainfall 178 percent above average. And in November, Tropic Storm Eta dropped close to 500% of average rainfall for that month. “It was a huge volume of rain at the end of what was already a wet, wet season,” he said.

“Going forward puts us in a position to be higher than we want to be at the start of the 2021 wet season.”
Kelly said they are monitoring the rainfall and lake level conditions and watching the trends.

He said he does not talk about lake level targets because much of the time “Mother Nature is in charge.
“At this point what we do is we watch the trend,” he explained.

“The ecological zone for Lake Okeechobee, should be 12 to 12.5 feet at the beginning of the wet season. That is one of the sweet spots that everybody is comfortable. We watch how quickly the lake is receding. We try to find the right recession rate, not only for the lake but for the basins south of the lake.

“If as we go forward in the next couple of weeks, as we’re able to potentially increase water releases to the south, and we keep on the upper level of what is good for the Caloosahatchee River, we don’t need to push water to the St. Lucie,” he continued.

“If we get more rain than we expect or if the recession rate isn’t good, we would have to start releasing water to the St. Lucie as well, to increase the volume leaving the lake.”

Water supply good
While last year, water supply was a concern, this year “there’s water, water everywhere and we’re not anywhere near having any concerns about water supply,” said Kelly.

“Last year we were very concerned about water supply and we spent most of the year conserving water on the lake for water supply,” he explained. “This year, there’s simply a ton of water and we’re not anywhere near being concerned.

“There’s plenty of water to go around for everybody this year and little bit too much.”

The water shortage management line this time of year is about 13 feet. “At this time of year, if we were close to 13 foot line, all I would be talking about right now is water supply,” Kelly added.

EAA reservoir work on track
South of the lake, work on the Everglades Agricultural Area (EAA) reservoir is on track, Kelly said. "We’re very excited about how the EAA reservoir is going,” he added. “We anticipate being able to start letting corps contracts to begin some canals and seepage canals in preparation for the reservoir.

“We are all systems go with the EAA reservoir moving forward,” he said.

Kelly explained the project is not fully funded at this point, but that is not unusual. He said like all Comprehensive Everglades Restoration Plan (CERP) projects, the EAA reservoir is a 50/50 partnership with state and federal funding.

“Projects of this magnitude typically are funded on an annual basis,” he explained.

The EAA reservoir will hold 240,000 acre-feet of water. The project was conditionally authorized in the federal Water Resources Development Act of 2000 as a component of CERP. To accelerate progress on the project, the Florida Legislature passed Senate Bill 10 in 2017. Congress provided additional authorization and approval in 2018 and 2020 to support the project’s plan developed by the South Florida Water Management District (SFWMD).

The project, which will cost an estimated $1.6 billion, includes a combination of canals, 6,500 acres of stormwater treatment areas (STAs), and a 10,500-acre reservoir. SFWMD is moving ahead with what they are doing with this project, Kelly said. “They have already started work on the STA.”

Construction of the reservoir is expected to take about 5 years.

How much water is moving?

If there is no rain in the Caloosahatchee basin and the flow west through the Franklin Lock of 2,000 cfs  is all from the lake, that equals about 9 billion gallons of water a week. One inch on Lake Okeechobee equals 12 billion gallons of water.  So the Caloosahatchee flow would equal about 3 inches a month. If there is rain in the basin, less water would come from the lake.

The effect on the lake level also depends on how much water is flowing into the lake. About 90% of the flow into the lake comes from the north. The watershed starts just south of Orlando.

For the seven-day period ending Feb. 12, the lake dropped from 15.39 feet to 15.37 feet, a little less than one-quarter of an inch.

Evapotranspiration from the lake is also a factor. On average, during the dry season, the lake loses about 1 foot of water to evapotranspiration, according to the corps.

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