SFWMD reports declining phosphorus concentrations across Everglades treatment areas amid extreme dry season

SFWMD reports declining phosphorus concentrations across Everglades treatment areas amid extreme dry seasonDespite record-low inflows and drought conditions, the South Florida Water Management District's massive network of treatment wetlands is showing improved water quality metrics, bolstered by aggressive vegetation management and strong agricultural source controls.

The Everglades Agricultural Area (EAA) basin achieved a 62% total phosphorus load reduction in Water Year 2025, significantly exceeding its 25% statutory mandate.

Water Year 2026 is currently experiencing the lowest STA inflows on record due to a dry season that has seen only 37% of normal rainfall.

STA-1 East, STA-1 West, STA-2, and STA-3-4 are all showing downward trends in inflow and outflow total phosphorus concentrations compared to the previous two years.

District staff are executing whole-cell regrading, mechanical vegetation shredding, and targeted drawdowns to correct short circuits and optimize submerged aquatic vegetation.

Environmental advocates warned that despite recent progress, the district must consistently meet the strict Water Quality Based Effluent Limit of 13 to 19 parts per billion.

The South Florida Water Management District (SFWMD) reported significant progress in its efforts to reduce total phosphorus (TP) discharges into the Everglades Protection Area, driven by steep upstream load reductions and aggressive physical refurbishment of its Stormwater Treatment Areas (STAs). During the 23rd Annual Public Meeting on the Long-Term Plan for Achieving Water Quality Goals on February 23, 2026, district staff outlined the operational and infrastructural interventions keeping the 640,000-acre treatment network on track, despite extreme weather volatility. Robert Shuford of the Everglades and Estuaries Protection Bureau noted that the district is currently managing the "lowest inflows that we have on record" for Water Year 2026. While the wet season saw normal rainfall, the dry season has plummeted to just 37% of normal levels, creating a nearly five-inch rainfall deficit. Despite these dry conditions, the treatment wetlands are largely performing well. Jessica Jenison of the Applied Sciences Bureau reported a downward trend in both inflow and outflow TP concentrations for STA-1 East, STA-1 West, STA-2, and STA-3-4 compared to the previous two water years. The only outlier was the western flow path's STA-5/6, which experienced elevated outflow concentrations due to a TP spike following a post-dryout rehydration event last summer. Jenison noted that the recently operational C-139 Flow Equalization Basin (FEB) is expected to help mitigate the frequency and duration of future dryouts in STA-5/6. Upstream source control programs are also heavily contributing to the system's performance. Stephanie Nevadunsky reported that the Everglades Agricultural Area (EAA) basin achieved a 62% TP load reduction in Water Year 2025, far exceeding the statutory requirement of a 25% reduction. The program maintains a 30-year average load reduction of 57%. The neighboring C-139 basin also remained in compliance, discharging 54 tons of phosphorus against its target. To sustain biological nutrient uptake in the aging STAs, the district is executing large-scale civil and vegetation engineering projects. While constructed surface flow wetlands generally offer lower lifetime costs than conventional treatment facilities and tolerate flow fluctuations well, uniquely massive regional stormwater systems like the STAs demand significant land footprints and rigorous ongoing maintenance. Wetland scientist Jake Thayer detailed extensive mechanical shredding operations in STA-1 West to remove delaminated, floating vegetation mats that cause hydraulic short-circuiting. In STA-1 East, an unmanageable short circuit forced the district to completely dewater Cells 3 and 4 North to conduct a whole-cell regrading operation using heavy equipment and laser leveling. The district is also testing adaptive management strategies to optimize submerged aquatic vegetation (SAV), which is critical for polishing water at the backend of the treatment cells. Staff detailed a targeted drawdown in STA-2 Cell 3 that successfully consolidated soils and restricted the foraging access of large invasive fish, such as tilapia. This intervention resulted in significantly higher SAV coverage upon rehydration. While the district's WY 2026 metrics are trending positively, stakeholders continue to press for strict adherence to the Water Quality Based Effluent Limit (WQBEL). During public comment, Gil Smart, Policy Director for Friends of the Everglades, noted that the standard requires outflows to remain below 13 parts per billion in three out of five years, and never exceed 19 parts per billion in a single year. "The trend line in the 2026 water year is encouraging. The trend line of 2025 water year was not encouraging," Smart said, adding that his organization believes more land south of Lake Okeechobee will ultimately be needed for additional STAs and water storage.