STUART – The U.S. Army Corps of Engineers (USACE) will release water east to the St. Lucie River and Lake Worth Lagoon and slightly increase releases west to the Caloosahatchee River, starting Dec. 7, according to information shared at a Nov. 21 Rivers Coalition meeting in Stuart.

Lake Okeechobee was at 16 feet above sea level on Nov. 22. The lake’s optimal ecological envelope ranges from 11 or 12 feet at the start of the wet season to 15.5 feet at the start of the dry season.

While the Lake Okeechobee System Operating Manual (LOSOM) minimizes and attempts to eliminate releases to the St. Lucie River and the Lake Worth Lagoon, LOSOM allows freshwater releases east during a “recovery year.”

The recovery period is designed to bring the lake level down to 12 feet or lower for 90 days or 11 feet or lower for 60 days to allow sunlight to reach the lake bed and submerged aquatic vegetation (SAV) to sprout.

The target minimum SAV for the Big O is 35,000 acres. According to the South Florida Water Management District, the lake currently has about 3,500 acres of SAV.

 In a normal year, releases south for water supply and east to maintain optimal salinity levels in the Caloosahatchee Estuary, combined with evapotranspiration or ET (a combination of evaporation and plant transpiration) take about 3 feet of water off Lake O. Since the lake is at 16 feet, to get the lake down to 12 feet, means an extra foot – about 144 billion gallons of water – has to go somewhere else by June.

In a recovery year, USACE can release up to 2,100 cubic feet per second (cfs) from Lake Okeechobee to the Caloosahatchee River. However, this may not all be lake water. The flow is measured at the W. P. Franklin Lock, which is more than 43 miles from the Julian Keen Lock at Moore Haven, where lake water enters the river. The target includes local basin runoff.  The target is currently 2,000 cfs, so recovery level is just a slight increase.

Recovery also allows USACE to release up to 1,400 cfs to the St. Lucie River. Again, this may not all be from Lake Okeechobee. If there is local basin runoff, less water can be released from the big lake.

In addition, the RO allows releases of up to 350 cfs to the Lake Worth Lagoon. 

Those releases – if there is no local rainfall in the mix, account for the equivalent of about 3 inches off Lake Okeechobee per month. If the predicted weather forecasts are accurate, that 12 inches of lake water, combined with normal releases south for water supply and ET (which take about 3 feet off Lake O every dry season) could bring the lake level down to 12 feet by the start of the wet season.