Direct rainfall into Lake Okeechobee slowed the big lake’s recession the week of Feb. 24 to March 2.  On Feb. 24, some areas in Okeechobee County received more than 3.5 inches of rain in less than 24 hours. Direct rainfall into Lake O totaled 51,640 acre feet of water. Surface inflows from the north added 10,900 acre feet.

Evapotranspiration removed 35,150 acre feet of water from the lake. A total of 18,800 acre feet flowed west to the Caloosahatchee River. A total of 8,970 acre feet of water flowed east to the St. Lucie Canal (C-44 canal) and the Lake Worth Lagoon. Flows south into the Everglades Agricultural Area (EAA) and the stormwater treatment areas (STAs)  totaled 10,540 acre feet. Flow south was limited by direct rainfall south of the Big O which took up some of the capacity there.

According to the weekly Environmental Conditions Report by John Mitnik, Assistant Executive Director of the South Florida Water Management District, Lake O was 13.73 feet on Feb. 23, which was 0.31 feet lower than the previous week and 0.84 lower than one month ago.

Mitnik reported Lake O water accounted for less than half of the flow to the St. Lucie Estuary, which averaged a flow of 1,343 cubic feet per second (cfs) with 616 cfs coming from Lake O. Salinity in the middle estuary was in the optimal range for adult oysters (10-25).

Inflow to the Caloosahatchee from Lake O averaged 1,537 cfs. Salinity levels were in the optimal range (0-10) for tape grass in the upper estuary. Salinities were also in the optimal range for adult oysters at Cape Coral and Shell Point (10-25) and the upper stressed range (>25) at Sanibel.

Salinity levels are given in grams of salt per liter or kilogram of later. Seawater typically averages 35 g/kg. Plants and animals that make up the ecosystem of an estuary require varying levels of salinity.

Both the Caloosahatchee and St. Lucie Estuaries are the result of man-made changes to the natural system.

Historically, the St. Lucie River was a freshwater river and had no connection to the ocean. In 1892, an inlet was dug by local residents to provide direct access to the ocean. During the 1900s, the watershed underwent a series of changes for navigation, flood control and water supply that changed the St. Lucie into an estuary.

Before man-made changes, the Caloosahatchee River was only connected to Lake Okeechobee during the wet season. During the wet season, heavy rainfall would cause water from Lake O to flow through a series of marshes and smaller lakes into the Caloosahatchee River. During the dry season, the marshes would dry up and the river’s water level would fall dramatically. In the 1880s, Hamilton Disston dredged portions of the river to make a liquid highway from Fort Myers to Lake Okeechobee for boat traffic. In the 1930s, 1940s and 1960s, more changes were made to the river for flood control. These changes, which allowed development, meant the basin drains more quickly than nature designed. As a result, the Caloosahatchee River depends on dry season flow from Lake Okeechobee to prevent salt water intrusion.

Several years of high lake levels have damaged the lake’s submerged aquatic vegetation (SAV). SAV is the filter system that cleans the lake water. SAV also provides critical habitat for fish.

On. Dec. 7, 2024 the U.S. Army Corps of Engineers (USACE) began recovery mode releases from Lake Okeechobee to the St. Lucie and Caloosahatchee Estuaries with the goal of lowering Lake Okeechobee sufficiently to allow submerged aquatic vegetation (SAV) to recover.

The target to the  St. Lucie Canal (C-44) was set at 1,400 cfs, including lake water and local basin runoff. The St. Lucie Lock is more than 20 miles from Port Mayaca, where lake water enters the canal.

The target for the Caloosahatchee River was set at 2,100 cfs, measured at the W. P. Franklin Lock. This also includes local basin runoff as well as lake releases. The Franklin Lock is more than 43 miles from Moore Haven, where the lake water enters the Caloosahatchee River.

Recovery mode also calls for maximum practicable releases south.

On March 5, Lake Okeechobee was at 13.63 feet above sea level.

For the SAV to recover, the big lake needs water levels below 12 feet for 90 days or below 11.5 feet for 60 days.