Lake Apopka

Lake Apopka is the fourth largest lake in the state of Florida. It is located 15 miles (24 km) northwest of Orlando, mostly within the bounds of Orange County, although the western part is in Lake County. Fed by a natural spring, rainfall and stormwater runoff, water from Lake Apopka flows through the Apopka-Beauclair Canal and into Lakes Beauclair and Dora. From Lake Dora, water flows into Lake Eustis, then into Lake Griffin and then northward into the Ocklawaha River, which flows into the St. Johns River.

Lake Apopka has a history of more than 100 years of human alteration, beginning with construction of the Apopka-Beauclair Canal in 1888. In 1941, a levee was built along the north shore to drain 20,000 acres (80 km²) of shallow marsh for farming. The discharge of water, rich in nutrients from agricultural and other sources, produced conditions that created a chronic algal bloom and resulted in loss of the lake's recreational value and game fish populations.

In July 1980, Tower Chemical Company (TCC), a local pesticide manufacturer, improperly disposed of significant amounts of DDE, a known endocrine disruptor, along with other toxic chemicals. As a result, these chemicals spilled into Lake Apopka, and the US Environmental Protection Agency was alerted.^[3] TCC shut down their operations in December 1980. In 1981, an EPA investigation began and the site was decommissioned and designated as a Superfund clean-up site. Despite their efforts, some of the chemicals seeped into the Florida aquifer and have proliferated into some of Central Florida's interconnected lakes and waterways. This chemical has caused health problems in much of the lake's wildlife population, and has caused infertility and other sexual disorders in several species, including alligators.

In 1991, a coalition of real estate interests from the West Orange Community organized the Friends of Lake Apopka (FOLA) with the goal of reclaiming the lake from the agricultural interests who were discharging phosphorus laden water into the lake basin. Water from the lake was used to flood the farm fields during the hot summer months to restrict erosion and then discharged back to the lake before the growing season. A series of canals and high capacity pumps allowed the water to be introduced for irrigation and flooding or to discharge it when necessary. The phosphate laden water created a hypereutrophic condition resulting in algal blooms, robbing the lake water of oxygen and sunlight necessary to sustain plant life on the lake bottom. Over the decades, this condition caused the sandy bottom lake to be covered by a deep layer of muck.

In 1996, Governor Lawton Chiles signed the Lake Apopka Restoration Act that provided funding to purchase the farmland responsible for the discharges. The shuttering of the farms allowed for the St. Johns River Water Management District (SJRWMD) to begin plans to convert the fields back to the marsh area it had once been. A survey was taken of the site that identified the hot spots that contained chemical contamination, and cleanup was initiated.

The District has 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 the reductions in external phosphorus loading from the watershed to the lake with improved lake water quality. Total phosphorus, chlorophyll and Secchi transparency showed improving trends between 1987 and 2010. 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. The lake lost nearly 80 percent of its volume and total phosphorus concentrations increased. However, the improving trend continued the following year. Total phosphorus concentrations between 2004 and 2006 were under 100 ppb and approached the 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 and water quality continues to improve in 2010. The most recent data (September 2011) indicate that total phosphorus concentrations were 80 ppb (a decrease of 62 percent compared to the baseline period), chlorophyll a was 52 ppb (decrease of 36 percent), and water transparency (Secchi depth) was 37 cm, (increase of 53 percent).