The new Lake Okeechobee System Operating Manual (LOSOM) is on track to go into effect in June, according to Col. James Booth of the U.S. Army Corps of Engineers.
In a Dec. 16 media briefing, Booth said the lake operation is currently managed under the Lake Okeechobee Regulation Schedule (LORS).
Under LORS, the current lake level and conditions would call for releases of up to 4,000 cubic feet per second (cfs) to the Caloosahatchee River and up to 1,800 cfs to the St, Lucie. However, USACE has set the target for the Caloosahatchee at 2,000 cfs and has no plans to release lake water to the St. Lucie.
He said they hope to make releases to the Caloosahatchee in the beneficial range of 2,000 cfs or less throughout the dry season in order to lower the lake before the start of the next wet season.
During the dry season, the Caloosahatchee River needs some freshwater flow from the lake to prevent the estuary from becoming too saline. However, too much freshwater makes the estuary too fresh.
One inch on lake Okeechobee is 12 billion gallons of water. Releases of 2,000 cfs equal about 9 billion gallons per weeks or about 217 billion gallons by June 1. That’s about 18 inches on Lake Okeechobee – less if some of the 2,000 cfs target flow at the Franklin Lock is taken up by local basin runoff. The Franklin Lock is more than 40 miles from the Julian Keen Jr, Lock at Moore Haven, where Lake Okeechobee meets the Caloosahatchee River.
As of Dec. 16, Lake Okeechobee was at 16.37 feet above sea level. The ecological envelope – the lake level most beneficial to the lake’s ecology – ranges from 12 to 12.5 feet at the beginning of the wet season (around June 1) to 15.5 feet at the end of the wet season.
If dry season releases to the Caloosahatchee River account for 18 inches on Lake O, is it possible to get the lake down to 12.5 feet by June 1? Much depends on Mother Nature. Most of the water that leaves Lake Okeechobee does so through evapotranspiration – a combination of evaporation and plant transporation.
Lake water also flows south. However, due to federal rules about the maximum amount of phosphorus in water entering Everglades National Park (ENP), the water must be cleaned before it can be released south. Water coming into the lake from the north is much higher in phosphorus than the levels allowed to flow into ENP. In addition, Hurricane Ian and Hurricane Nicole stirred up the big lake and water managers believe the nutrient levels in the lake were likely increased by stirring up the muck on the lake bottom.
Booth said most of the lake water that flows south is for water supply. Lake Okeechobee provides water supply for the farms in the Everglades Agricultural Area and to coastal urban areas. The Big O supplies about half of the dry season drinking water supply for West Palm Beach.
The lake was low for much of the 2022 dry season, but Hurricane Ian dumped around 1 million acre feet of rainfall north of the lake. To relieve flooding in the Orlando/Kissimmee area, water managers moved that water as quickly as possible down the Kissimmee River and into Lake O. Just before Hurricane Ian hit in September, the lake was around 13 feet. It peaked at 16,51 and is now slowly receding.
Booth said forecasters predict below normal rainfall in the dry season, which could help lower the lake before the start of the 2023 wet season,
He said they are also concerned the 2022 hurricanes left the lake at higher risk for harmful algal blooms next summer, due to the increase in nutrient load. The storms and high lake levels also damaged the marshes and submerged aquatic vegetation which helps clean the water.