USACE holds the line on releases as the lake level continues to rise
Lake Okeechobee was at 16 feet above sea level on Oct. 6.
According to the South Florida SFWMD data for the seven-day period of Sept. 25 through Oct. 1, Lake Okeechobee received 117,120 acre feet of direct rainfall into the lake. For that same time period, surface water inflows from the north totaled 92,140 acre feet, while evapotranspiration was only 28,160 acre feet, and total outflows only 560 acre feet.
That means the difference between the amount of water entering the lake and the amount of water leaving the lake was 58 billion gallons of water or about 4.8 inches on Lake Okeechobee.
With the lake already so high, and receiving so much direct rainfall, why isn’t more water held north of the lake in the Kissimmee River, Lake Istokpoga and the Kissimmee Chain of Lakes?
South Florida received very heavy rainfall in some areas the weekend of Sept. 29 to Oct. 1, explained Savannah Lacy of the U.S. Army Corps of Engineers in an Oct. 6 media call.
She said before the recent rains, the Kissimmee Chain of Lakes were all below regulation schedule.
“Most of the lakes but are now above schedule,” she said.
“We also received lot of rain over the river itself which had to flow into Lake Okeechobee,” she continued.
A good bit of rain fell in the restored section of the river, which had been dry for most of the “wet” season, she explained. Earlier in the season, while the area south of the restored section had heavy rainfall, the Kissimmee Chain of Lakes and the upper section of the river were below normal rainfall.
The Kissimmee River Restoration project restored the “bends” to the middle third of the river, which will allow the water to spread out onto the historic flood plain in that section. The next step is to change the regulation schedule for the Kissimmee Chain of Lakes, to hold more water north of the river in the wet season in order to keep the water supply steady to the restored wetlands in the dry season.
“We are on track for the increment 1 deviation for Kissimmee Chain of Lakes by the end of this year,” said Lacy. This will raise the water level schedules for Lake Kissimmee, Lake Cypress and Lake Hatchineha. Holding more water in those lakes will help slow the flow into Lake Okeechobee from the north – but only when the rainfall is in that area. When the heavy rain falls south of the restored portion of the river – as it has this wet season – it can only flow south into the lake.
In related news, Lacy said the corps continues to work on the next steps for the new Lake Okeechobee System Operating Manual (LOSOM). She said USACE has received a final biological opinion from the National Marine Fisheries Service. The biological opinion does not require changes to the final water control program presented to the public last summer, she said.
On Oct. 6, Lacy said total inflows to the lake are averaging about 9,600 cubic feet per second (cfs), with little water leaving the Big O, aside from the water lost through evapotranspiration.
For the seven-day period ending Oct. 6, flow at the Franklin Lock on the Caloosahatchee River was 6,900 cfs, mostly from local basin runoff, she explained.
“Last week, we had very heavy local rainfall over the C-43 (Caloosahatchee) basin,” she said. There was no capacity to release lake water to the Caloosahatchee River through the Julian Keen Jr. Lock at Moore Haven, which is more than 43 miles from the Franklin Lock.
Lacy said there is a large mat of floating vegetation near the entrance to the Julian Keen Jr. Lock. USACE may have to temporarily close the lock in order to clear the vegetation.
The current flow target for the Caloosahatchee River is 2,000 cfs, measured at the Franklin Lock. When local basin runoff meets or exceeds that target no water is released from Lake Okeechobee. As a result of local rainfall, very little lake water has been released west this wet season.
To the east, the target flow at the St. Lucie Lock continues to be 0 cfs. Last week, due to heavy rainfall in the C-44 (St. Lucie) basin, USACE pumped water into the C-44 reservoir, raising the water level by about 2 feet to 6 feet. This 3,400-acre above ground reservoir has been tested to hold water up to 10 feet.
South of the lake, the Water Conservation Areas are all above schedule and USACE is maximizing flow under the Tamiami Trail into Everglades National Park for an average flow of 3,300 cfs.
Because the Everglades Agricultural Area (EAA), EAA Stormwater Treatment Areas (STAs) and WCAs also received heavy direct rainfall last week, no lake water is moving south.
Lacy said so far this year, they have sent almost 966,000-acre feet of water to Everglades National Park. She said due to the high water levels in the WCAs, the S-12 A and S-12 B structures are open and will remain open until Nov. 1. Usually, those structures close in October and stay closed nine months of the year in order to protect the nesting grounds of a subpopulation of the Cape Sable Seaside Sparrow.
On Nov. 1, S-12A will close, but if high water levels continue in the WCAs, the S-12 B water control structure will remain open until Dec. 1.
While USACE continues to operate the system under the Lake Okeechobee Regulation Schedule of 2008 (LORS-08), they have been using “operational flexibility” to hold more water in the lake and protect the coastal estuaries. If LOSOM were already in place right now, the releases would be about the same as they have been over the past two years.
Under current conditions for this time of year, LORS-08 calls for releases of up to 4,000 cfs at the Julian Keen Jr. Lock and 1,800 cfs at the St. Lucie Lock. No lake water is being released through either of those structures.