Lake Okeechobee has dropped about 1 inch a week since the start of the year, according to data released Feb. 1 by the South Florida Water Management District.
According to SFWMD, the level of Lake Okeechobee was 16.36 feet above sea level on Dec. 29, 2022 and 16.02 feet on Jan. 29, 2023.
Lake Okeechobee is more than half a foot above the upper limit of the lake’s ecological envelope, which ranges from a low of 12 feet to 12.5 feet and a high of 15.5 feet. Water levels above 15.5 feet are damaging to the lake’s ecology because the water stacks up on the Herbert Hoover Dike, and prolonged high water levels damage the marshes. This is the third year in a row lake stages have exceeded 16.0 feet in the fall or winter season.
According to the SFWMD report, the fourth wading bird survey of the season was conducted on Jan. 26, 2023. Six flocks, with an estimated total of 2,790 birds were seen actively foraging on the lake, which is less than a third of the five-year average. Water levels remain too high to provide suitable foraging habitat across much of the lake.
For the week of Jan. 21-Jan. 29:
• Inflows to Lake O totaled 36,570 acre feet, including: 23,820 acre feet in surface water flows from the north, and 12,750 acre feet in direct rainfall into the lake.
• Outflows from the lake totaled 63,200 acre feet, including: 11,510 acre feet south; 18,080 acre feet west to the Caloosahatchee River; 11,960 acre feet east to the St. Lucie River; and, 21,650 acre feet to evapotranspiration (a combination of evaporation and plant transpiration).
The difference between the inflows and outflows was 26,630 acre feet, or about 8.67 billion gallons of water. That’s less than 1 inch on Lake Okeechobee. One inch of the big lake equals about 12 billion gallons of water.
Most of the surface inflow into the lake is coming from the Kissimmee River.
South of the lake, for the same week, the water conservation areas (WCAs) received 2,270 acre feet in flow from the stormwater treatment areas (STAs) and 6,300 acre feet in direct rainfall for a total of 8,570 acre feet of water. For that same period, outflow from the WCAs included 18,450 acre feet sent south to Everglades National Park, 2,290 in coastal outflows and 36,010 acre feet in evapotranspiration for total outflows of 56,750 acre feet. The WCAs and stormwater treatment areas (STAs) are still recovering from the heavy rainfall from Hurricane Ian and Hurricane Nicole. Water levels in WCA-1 and WCA-2A are above schedule for this time of year.
While the lake releases have caused salinity levels in the St. Lucie estuary to drop, salinity in the middle estuary was in the optimal range for oysters, according to SFWMD.
Total inflow to the Caloosahatchee estuary averaged about 2,175 cubic feet per second (cfs) with 1,290 cfs coming from Lake Okeechobee and the rest from local basin runoff. Caloosahatchee flow is measured at the Franklin Lock, which is more than 40 miles from Lake Okeechobee. Salinities were in the optimal range for tape grass in the upper estuary. Salinities were in the optimal range for oysters at Cape Coral and Shell Point.
The Caloosahatchee River needs some freshwater flow from the lake during the dry season if local basin runoff is not sufficient to maintain the desired salinity levels. Flow (measured at the Franklin Lock) below 457 cfs is considered damaging to the estuaries because the salinity levels are too high. Flow greater than 2,600 cfs is considered damaging because the salinity levels drop too low.