Basins: Lake Apopka

St. Johns River Water Management District

St. Johns River Water Management District - floridaswater.com

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Background and history

Lake Apopka

Lake Griffin

Map of the regions (flood control areas) where water control structures operated by the District are designed to reduce flood impacts
- Closer view

Lake Apopka shad harvesting
(video)

Setting Water Quality Goals for Restoration of Lake Apopka: Inferring Past Conditions (technical report)
Total Maximum Daily Load for Total Phosphorus for Lake Apopka, Lake and Orange Counties, Florida (technical report)
Florida Fish and Wildlife Conservation Commission aquatic plant management strategy for Lake Apopka

Lake Apopka Basin

The story of Lake Apopka is familiar to many Floridians — the state’s fourth-largest lake was once a world-class bass fishery but impacts to the lake over many decades led the lake to be named Florida’s most polluted large lake.

In recent years, the St. Johns River Water Management District and its partners have been writing a new chapter to the story — a story about wetlands restoration, the reduction of total phosphorus and other solids in the water, improvements in water quality and the restoration of wildlife habitat.

Solutions

Support for the lake’s restoration was evident at a December 2011 Lake Apopka Summit. Spearheaded by Florida Sen. Alan Hays, the summit brought together state, county and city elected officials throughout the region, along with officials from the Florida Department of Environmental Protection, the District, the University of Florida, Florida Fish and Wildlife Conservation Commission (FWC), Lake County Water Authority, Friends of Lake Apopka, and the Harris Chain of Lakes Restoration Council.

Ongoing projects to restore the lake include:

Shad harvesting — Harvesting gizzard shad from Lake Apopka removes the nutrients (phosphorus and nitrogen) contained in the fish bodies and reduces the internal recycling of these nutrients within the lake. This improves water clarity by reducing the severity of algal blooms, which depend on phosphorus for growth. Through 2011, 19.4 million pounds of shad had been removed from the lake, thus removing the total phosphorus contained in the shad’s bodies, as well as reducing the internal recycling of total phosphorus within the lake. Algae depend on total phosphorus for growth.
Marsh Flow-Way — The Lake Apopka Marsh Flow-Way is a 760-acre constructed wetland along the northwest shore of Lake Apopka. The wetland system removes phosphorus and suspended material already in Lake Apopka water, moving water through four individual wetland cells, in addition to levees, canals and ditches. As of 2011, the marsh flow-way had removed about 20.8 metric tons of total phosphorus and it eliminates approximately 4,360 metric tons of total suspended solids per year from incoming Lake Apopka water.
Aquatic vegetation planting — The FWC is planting native aquatic vegetation to provide fish habitat and to provide wave protection for the shoreline.
Fish attractors — FWC is building six, 2-acre underwater structures that resemble small tree limbs and other brush, anchored with concrete blocks to provide game fish habitat. They also are conducting studies to determine the best ways to reintroduce game fish to the lake.
Innovative technologies — The Florida Department of Environmental Protection is investigating new techniques and technologies for removing phosphorus from the lake and will be implementing test projects.

Eelgrass beds are starting to naturally revive with improvements in Lake Apopka’s water.

Eelgrass beds are reocurring in Lake Apopka as water conditions improve.

In the early years of restoration, the District planted wetland plant species behind protective barriers in Lake Apopka to provide habitat for fish and wildlife. These planting efforts are becoming less necessary as the lake’s water quality and clarity improve and native aquatic plants re-establish themselves. An ongoing effort is under way to map the locations and extent of more than 350 native submersed plant beds. This total number varies from year to year.

Improved water clarity has also made it possible for the nonnative invasive plant hydrilla to grow in the lake. Hydrilla can quickly outcompete native plants, so staff efforts are also focused on locating and treating these undesirable plants with herbicides.

Lake Apopka has responded to restoration efforts and its water quality has improved. Total phosphorus, chlorophyll and Secchi transparency showed improving trends between 1987 and 2011. However, during this 23-year period, three events contributed to a worsening of water quality within a given year. The first coincided with a storm in March 1993. However, the improving trend in water quality resumed the following year. The second occurred in 2001 and 2002 at the end of a severe drought when the lake lost nearly 80 percent of its volume and total phosphorus concentrations increased. Despite this short-term perturbation, water quality continued to improve during the following year. Total phosphorus concentrations between 2004 and 2006 were under 100 parts per billion (ppb) and approached the total maximum daily load (TMDL) target of 55 ppb. These long-term improvements persisted despite the hurricanes in 2004 and 2005. The most recent event was a severe drought in 2007 and 2008, in which the lake lost up to 52 percent of its volume. Total phosphorus concentrations increased sharply at low lake stages, but total phosphorus concentrations declined again in 2009 and continued to decline with water quality continuing to improve through 2011. The most recent data during the last five years (2007–2011) indicate that total phosphorus concentrations improved by 41 percent when compared to the baseline period (1987–1992). Chlorophyll a and water transparency showed similar improvements.

Improvements already evident at the lake make it attractive to the public. A partnership between the District and Orange and Lake counties has led to the Apopka Loop Trail, which opened the first of three phases in June 2012. Phase I features a 3.4-mile trail that allows access onto the North Shore Restoration Area from Orange County’s Magnolia Park Connector Trail. In 2013, Orange County plans to add a picnic area overlooking the lake and a foot-bridge at an old pump house. Phase II, scheduled to open in fall 2013, includes approximately five miles of trail connecting the North Shore Connector and existing trail at Clay Island. Phase III, which will complete the section of trail on District property, in scheduled for completion in 2014 when Lake County finishes the southwestern trailhead.

The restoration at Lake Apopka is a work in progress that features adaptive approaches that have helped restore the lake in recent years, as well as new technologies that should lead to continued improvements.