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SFWMD: Weekly Environmental Conditions Report


South Florida - Thursday March 21, 2024: The Weekly Environmental Conditions Report released by the South Florida Water Management District (SFWMD), focuses on the ongoing efforts by the U.S. Army Corps of Engineers and SFWMD to lower the level of Lake Okeechobee and other key south Florida water bodies ahead of the start of the raining season and the onset of the Hurricane Season. Below is a summary of last week's findings.

Among the most noteworthy findings in the report was "a moderate bloom risk along most of the north, west and south shorelines of the Lake," based on a March 14 NOAA satellite observations. In addition the report found that "mean salinities" have increased in the St. Lucie Estuary, however they have remained much the same in the Caloosahatchee Estuary where they have ranged from "optimal" to "damaging" in recent weeks.


Lake Okeechobee
Lake Okeechobee stage was 15.75 feet NGVD on March 17, 2024, which was 0.19 feet lower than the previous week and 0.58 feet lower than a month ago. Average daily inflows (excluding rainfall) decreased from the previous week, going from 2,530 cfs to 1,570 cfs.

Average daily outflows (excluding evapotranspiration) also decreased from the previous week, going from 8,410 cfs to 4,210 cfs. The seventh wading bird foraging survey of the 2024 breeding season (conducted March 14, 2024) reported approximately 4,300 wading birds actively foraging on the Lake. The March 14, 2024, satellite image from NOAA’s Harmful Algal Bloom Monitoring System suggested a moderate bloom risk along most of the north, west and south shorelines of the Lake.

Total inflow to the St. Lucie Estuary averaged 470 cfs over the past week with most of the flow coming from Lake Okeechobee. Mean salinities increased at all three sites within the estuary over the past week. Salinity in the middle estuary was in the lower stressed range (5-10) for adult eastern oysters.

Total inflow to the Caloosahatchee Estuary averaged 2,640 cfs over the past week with 1,950 cfs coming from Lake Okeechobee. Mean surface salinities remained the same at
S-79, Val I-75, and Ft. Myers, increased at Cape Coral and Shell Point, and increased at Sanibel over the past week. Salinities were in the optimal range (0-10) for tape grass in
the upper estuary. Salinities were in the damaging range (0-5) for adult eastern oysters at Cape Coral, in the optimal range (10-25) at Shell Point, and in the upper stressed range (> 25) at Sanibel.

Releases were made from East Lake Toho and Lake Toho to continue spring lake stage recessions to low pool. Weekly average discharge on March 17, 2024, was 1,000 cfs and 970 cfs at S-65 and S-65A, respectively. Mean weekly water depth on the Kissimmee River floodplain decreased by 0.11 feet to 0.37 feet over the week ending March 17, 2024.

The weekly average concentration of dissolved oxygen in the Kissimmee River increased from 6.5 mg/L last week to 7.0 mg/L for the week ending March 17, 2024, which is well
above the potentially lethal and stressful levels for largemouth bass and other sensitive species.

Stormwater Treatment Areas
For the week ending Sunday, March 17, 2024, 5,700 ac-ft of Lake Okeechobee water was delivered to the FEBs/STAs. The total amount of Lake releases sent to the FEBs/STAs in WY2024 (since May 1, 2023) is approximately 43,600 ac-feet. The total amount of inflows to the STAs in WY2024 is approximately 1,390,000 ac-feet.

Most STA cells are near or above target stage. STA-1E Eastern Flow-way is offline for erosion repair in Cell 2. Operational restrictions are in effect in STA-1E Western Flow-way, STA-1W Northern Flow-way, STA-2 Flow-ways 2 and 4, STA-3/4 Eastern Flow-way, and STA-5/6 Flow-way 4 for vegetation management activities. This week, if 2008 LORS recommends Lake releases to the WCAs and conditions allow, releases will be sent to the A-1 FEB, STA-3/4, or STA-5/6.

Last week’s rates of stage change (Sunday to Sunday) were generally favorable for wading bird foraging and dry season Everglades ecology. Numbers of foraging wading birds continued to decline, and nesting is limited due to repeated reversals. The decrease in stage change in Taylor Slough was minimal again last week, but depths remain well above the recent average. Salinity change increased slightly in Florida Bay again last week, however conditions remain below or near the historical estimates for this time of
year and below the IQR. The 365 day moving average for the 5 creek flow is more than 4X the minimum flow and level volume.

Biscayne Bay
Total inflow to Biscayne Bay averaged 500 cfs and the previous 30-day mean inflow averaged 640 cfs. The seven-day mean salinity was 22.3 at BBCW8 and 22.4 at BBCW10, both within the ideal salinity range for estuarine organisms in this region (salinity less than 35). Data provided by Biscayne National Park.