PREFACE

2004 Lake Water Quality Report

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Limnology, the science of freshwater ecosystems, has been studied for many years. Much of the data has been collected on northern U.S. lakes and European lakes. Many of the Central Florida lakes cannot be characterized using the information derived from those lakes. Water quality in Central Florida lakes is influenced by a variety of natural and cultural factors. There are physical, biological, and chemical influences, and they do not work independently. Some physical factors include flushing and the topography of the lake. An example of a biological factor is the plant characteristics in a lake. Chemical factors include nutrient input to lakes, such as from stormwater runoff.

The shape and depth of a lake naturally affects the water quality. Central Florida lakes are generally characterized as shallow, bowl-shaped lakes often formed from sinkholes. Wind and sun help to keep the lakes mixed and heated more consistently than the temperate lakes to the north, although most City lakes stratify into distinct layers from time to time. Lakes undergo a flushing process. Rain, groundwater, and connections from other lakes bring water into a lake. Evaporation, drainage wells, and connections to other lakes allow water to leave a lake. The amount of time that the same water remains in a lake varies from lake to lake and can affect water quality.

Shoreline and bottom vegetation also affects the water quality in our lakes. Nutrients that find their way into lakes will promote vegetative growth along the shoreline and down to about 4 meters deep, depending on the water clarity. If the vegetation is removed (with herbicide, by hand, or by grass carp), algae will grow quickly with the availability of the nutrients. In an ideal situation, there is a balance between vegetation and nutrient input to the lake. There are desirable types of vegetation, which are native to Central Florida lakes as well as nuisance and exotic plants. Removal of exotic and nuisance plants is a common practice in lake management. One factor which helps prevent a lake from becoming algae dominated, is desirable vegetation.

Stormwater runoff is the water that flows over the land following a rain event. Historically, the volume of stormwater runoff was lower than it is now because much of the rainwater was soaked into pervious surfaces covered by vegetation. Urbanization brought roads, rooftops, parking lots, and other impervious surfaces. Stormwater runoff has increased in amount and velocity of flow with these impervious surfaces. Stormwater runoff affects the water quality of lakes and groundwater in Orlando because it collects many different substances in its path such as automotive fluids, dirt, nutrients (nitrogen and phosphorus), bacteria, leaves, and litter, carrying them to our water bodies. These pollutants are harmful to fish and other aquatic wildlife. The Orlando area also has drainage wells, direct conduits to the upper aquifer, taking stormwater runoff and lake overflow and mixing it with the groundwater.

Many of the substances found in stormwater are unintentional or circumstantial. For example, automobiles deposit petroleum products and heavy metals on the road with normal usage. Atmospheric deposition of nitrogen occurs naturally, as well. Leaves fall from trees into roads and parking lots, eventually washing into a lake or drainage well. However, some of the undesirable substances found in stormwater runoff are placed there intentionally or through neglect by improper disposal of waste liquids and solids. Any wastewater or other material allowed to drain into a street, alley, parking lot, driveway, or storm system potentially impacts the water quality of an area lake or the groundwater.

Does that mean the water quality of our lakes and groundwater must get worse? Not necessarily. Efforts by the public and private sectors of the community can and do stop the decline of water quality of our lakes. In fact in some cases, the water quality can be and is enhanced by specific behaviors and/or structural devices. Pollution prevention is the most cost-effective and easiest method of enhancing water quality in lakes.

Strict local and state regulations require new development and redevelopment to address water quality issues, especially concerning stormwater. Stormwater ponds collect and treat stormwater, as well as provide flood control. Innovative retro-fit stormwater treatment projects provide stormwater treatment and flood control in built out and poorly drained areas. The Greenwood Urban Wetlands near the intersection of Mills Avenue and Anderson Street, is a good example of this.

The private sector can help prevent lake water quality degradation, as well. Individuals who do not deposit the leaves and grass clippings from their yards into the street and who follow the label directions when fertilizing their lawns are not contributing to lake pollution. Businesses who dispose of their liquid waste through the sanitary sewer system where it can be treated (instead of the storm system) are preventing lake pollution. Construction sites where dirt is kept on site, prevent siltation of waterbodies and keep the pollutants bound to the sediments and out of waterbodies.

These are just a few examples of ways to prevent lake pollution. For more information about our lake water quality, contact the City of Orlando Streets and Stormwater Division, Stormwater Compliance Section at 407-246-2370.

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