Stormwater treatment areas (STAs) are

constructed wetlands A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. ...

divided into flow-through treatment cells that remove nutrients from agricultural and urban runoff water. The nutrients are consumed through plant growth, and captured by accumulation of dead plant material in a layer of sediment. STAs were introduced around the

Everglades National Park Everglades National Park is an American national park that protects the southern twenty percent of the original Everglades in Florida. The park is the largest tropical wilderness in the United States and the largest wilderness of any kind east ...

in an effort to reduce nutrient levels in water flowing towards the park. STAs have been estimated to reduce phosphorus levels by about 80%.

Description

Agricultural and urban runoff water containing excess

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

is channeled through pump stations into shallow marshes that have been planted with a selection of plants with useful characteristics for water purification, like

cattails ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrush or reedmace, in American English as reed, cattail, or punks, in A ...

, submerged aquatic plants and algae. These plants species absorb phosphorus, storing it in their roots, stems and leaves. When they die, they decompose creating a sediment layer that continues to absorb and hold decades worth of phosphorus. Water that flows out of the STAs into

has significantly lower levels of phosphorus than it did when it first entered.

History of phosphorus in Everglades National Park

The

Everglades The Everglades is a natural region of tropical climate, tropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large drainage basin within the Neotropical realm. The system begins near Orland ...

is a delicate ecological system with a naturally low level of existing phosphorus, resulting in a landscape of sawgrass, wet prairies and tree islands that were well adapted to the low nutrient environment. Increasing levels of nutrients such as phosphorus can encourage the growth of invasive species, smothering and crowding out the natives. STAs have been implemented in key positions at the northern edge of the

to help keep phosphorus laden water from reaching the park, but concerns remain that the already elevated phosphorus levels in both

Lake Okeechobee Lake Okeechobee (), also known as Florida's Inland Sea, is the largest freshwater lake in the U.S. state of Florida. It is the tenth largest natural freshwater lake among the 50 states of the United States and the second-largest natural freshwat ...

and the

Everglades Agricultural Area The Everglades Agricultural Area Environmental Protection District (EAA EPD), better known as simply the Everglades Agricultural Area (EAA), is an area extending south from Lake Okeechobee to the northern levee of Water Conservation Area 3A, from ...

(both heavy contributors to nutrient laden runoff) are so high that phosphorus loads into the park could continue for many decades.

References

{{Reflist Water resources management