Taylor Creek/Nubbin Slough and Indian Prairie targeted for phosphorus reduction efforts

WEST PALM BEACH — How will the South Florida Water Management District and partner agencies reduce the nutrient load in flow entering Lake Okeechobee? The same way you eat an elephant — one bite at a time. Those bites will start with the areas highest in phosphorus.

Taylor Creek/Nubbin Slough and Indian Prairie have been identified as areas for more detailed study in reducing phosphorus entering Lake Okeechobee. Those two watersheds contribute about one-third of the total phosphorous that goes into Lake Okeechobee each year.

At the July 21 online Lake Okeechobee Watershed Protection Plan Workshop, South Florida Water Management District (SFWMD) Science Supervisor Steffany Olson explained, “as the Lake Okeechobee Watershed area is quite large and resources are limited,” SFWMD will focus restoration efforts in areas where they will provide the most benefit In improving water quality.

The Lake Okeechobee Watershed is about 3.5 million acres and includes nine sub-watersheds. Within the sub-watersheds, each contains numerous basins, she explained.

The Florida Department of Environmental Protection has determined the lake should not receive more than 140 metric tons of phosphorus each year to be healthy, including the 35 metric tons deposited directly into the lake from the atmosphere (there is some phosphorus in direct rainfall).

On average, for Water Years 2015-2019, the lake has received an average 564.9 metric tons of phosphorus per year. (A water year is from May 1 to April 30.)

It’s a big watershed with a lot of excess phosphorus, she said. “You eat an elephant one bite at a time,” said Olson.

She said when choosing the sub-watersheds to target first, the research teams looked at nutrient load, discharged volume and proximity to the lake.

For the study years, on average, the six northern sub-watersheds contributed 95% of the flow and 92% of the phosphorus load, she explained.

Taylor Creek/Nubbin Slough, Indian Prairie and Lower Kissimmee have the highest area unit loads, she explained. Taylor Creek/Nubbin Slough has had the highest area unit load every year — more the one pound per acre. Considering the limited resources available, the district decided to focus on Taylor Creek/Nubbin Slough and Indian Prairie first, Olson explained.

Flow from Taylor Creek/Nubbin Slough contributes an average of 104.7 metric tons of phosphorus a year to Lake Okeechobee. Flow from Indian Prairie contributes 87.3 metric tons of phosphorous.

Taylor Creek/Nubbin Slough is about 197,795 acres and includes five basins. The team identified three of the basins for more study. Two basins, S-191 and S-154, had the highest contribution of total phosphorus loads. The S-154 C basin does not contribute much to the overall load but it has a high area unit load, she added.

Existing and proposed projects do not do enough to address the nutrient load from Taylor Creek/Nubbin Slough, she continued.

The Indian Prairie Subwatershed is 276,577 acres and has a complicated hydrology. The sub-watershed receives water from Istokpoga watershed, and there are multiple inflows into the lake, Olson explained.

In the public comment period, the question was raised about the need to reduce nutrient load in water coming from the upper Kissimmee basin.

“The upper Kissimmee does contribute larger loading to the lake and eventually we will move to other areas,” said Olson. “If we start at upper Kissimmee, because it is so far from the lake, it could be influenced by other areas.”

The team decided it would be best to start with areas closer to the lake, she said.

“We don’t have any intention of stopping any projects that are ongoing in these watersheds,” added SFWMD Director of Ecosystem Restoration and Capital Projects Jennifer Reynolds. She said they will look at how they maximize the use of available projects and look at the most effective locations for additional projects.

Another public comment involved the phosphorus coming from flood control canals.

“When we do our detailed assessment we will be looking at all things within those areas. We will look at water management practices as well as policies and programs,” said Olson.

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