2018 washed high nutrient load into the lake

OKEECHOBEE — Water Year 2018 (May 1, 2017 through April 30, 2018) brought ten times the target phosphorus loads into Lake Okeechobee, with about 90 percent of that load coming from the watersheds north of the lake, Stuart Van Horn, SFWMD Water Quality Bureau Chief, reported to the Water Resources Analysis Coalition meeting in West Palm Beach on Oct. 4.

Lake Okeechobee Inflow Water Year 2018, 5-year average

The annual maximum phosphorus target load into the lake, set by the Florida Department of Environmental Protection (FDEP) is 105 metric tons. The load to the lake in WY 2018 was about 1,000 metric tons, he said.

Phosphorus loads in the basins that flow into Caloosahatchee River and St. Lucie Canal were also high, he said. Most of the water and most of the phosphorus to those estuaries came from the local basin runoff, the data shows.

For the St. Lucie, local basin runoff contributed 63 percent of total inflow during WY 2018, with 75 percent of all inflow occurring during the wet season.

In WY 2018, Lake Okeechobee releases accounted for 37 percent of the total flow and 29 percent of the phosphorus load to the St. Lucie.

Most of lake flow was after Hurricane Irma, he said.

He added that runoff from the C-44 basin into the C-44 canal was probably under-reported due to a problem with the equipment that measures the flow there.

Lake Okeechobee releases were 39 percent of the flow and 30 percent of the phosphorus to the Caloosahatchee River in WY 2018, Mr. Van Horn explained.

Most of all inflow – 70 percent – was during the wet season, but the Caloosahatchee River receives regular releases from lake Okeechobee throughout the dry season to prevent saltwater intrusion in the river. During WY 2018, the minimum releases were 300 cubic feet per second. The schedule was recently changed to guarantee 400 cfs. Lee County officials have asked for the minimum to be set at 700 cfs. and have indicated the optimal dry season flow would be 1,000 cfs.

For the five-year average WY 2014-WY2018, Mr. Van Horn said, the northern watershed accounted for 95 percent of the water flow and 92 percent of the phosphorus load into Lake Okeechobee.

For the five-year average, Lake Okeechobee contributed 31 percent of the water and 23 percent of the phosphorus to the St. Lucie estuary.

The five-year average for lake water to the Caloosahatchee River was 38 percent of the water and 30 percent of the phosphorus.

Publisher/Editor Katrina Elsken can be reached at kelsken@newszap.com

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