CALOOSAHATCHEE RIVER/ESTUARY NUTRIENT ISSUE WHITE PAPER White Paper Caloosahatchee River/Estuary Nutrient Issues Prepared for the South Florida Water Management District 3301 Gun Club Road West Palm Beach, Florida 33406 October 10, 2005 South Florida Water Management District 1 White Paper Caloosahatchee River/Estuary Nutrient Issues Prepared for the South Florida Water Management District 3301 Gun Club Road West Palm Beach, Florida 33406 October 10, 2005 South Florida Water Management District 2 CALOOSAHATCHEE RIVER/ESTUARY NUTRIENT ISSUE WHITE PAPER Executive Summary The Caloosahatchee River/Estuary drains a watershed in southwest Florida extending from Lake Okeechobee on the east to the Gulf of Mexico on the west. The river/estuary system has been altered by agricultural and urban development during the past 120 years and is challenged by a variety of water quality problems, including altered salinity, elevated nutrients, and seasonal flow shifts. These altered conditions result in an increasingly visible impact on the natural flora and fauna of the aquatic ecosystems and have affected traditional human uses of the river and estuary. This white paper briefly summarizes the large body of existing information about the Caloosahatchee River/Estuary with a particular focus on nutrient issues. The purpose of this summarization is to provide a convenient reference document for decision-makers who will be convening over the next year to help resolve some of the most pressing environmental problems in the basin. Water quality and quantity have been altered in the Caloosahatchee Basin since historic times. Canalization of the Caloosahatchee River (C-43 Canal) has increased flood events and reduced dry season flows. Regulatory releases from Lake Okeechobee upstream periodically dump large freshwater volumes and associated nutrients into the Caloosahatchee River and Estuary. As human land uses in the watershed become more intense, both in agricultural production and for urban development, there are concerns that ambient concentrations and mass loads of both nitrogen and phosphorus have been increasing. Algal blooms in the estuary, massive accumulations of drift algae, and the geographic extent of red tides off shore have all apparently increased in recent years. Salinity changes have displaced key submerged aquatic plant species and the fauna those plants typically support. Decreased flows during the wet season and increased freshwater flows during the dry season are the target of the proposed C-43 Basin Storage Reservoir project as part of the Comprehensive Everglades Restoration Plan (CERP). Nutrient load reductions resulting from the project will be accomplished through flow reductions. Historically, nutrient load reductions have been accomplished through control of point sources with relatively high concentrations and low discharge volume. Here the reduction is accomplished primarily by decreasing loads that are primarily a function of high discharge with a low concentration. However, existing research has indicated that additional nutrient controls are needed in addition to control of timing of fresh water flows to help fully restore the Caloosahatchee aquatic ecosystem. A variety of agricultural and urban best management practices (BMPs) are potentially available to help reverse the apparent increasing nutrient loading rate trends. In addition point sources (stormwater and municipal wastewater) can be further polished to reduce their contributions to anthropogenic nutrient loads to the estuary. It will take a variety of technical solutions as well as serious political and economic will power to reverse the increasingly-evident nutrient associated impacts to the Caloosahatchee ecosystem. I CALOOSAHATCHEE RIVER/ESTUARY NUTRIENT ISSUE WHITE PAPER Contents Executive Summary...................................................................................................................... i Contents.........................................................................................................................................ii List of Tables ................................................................................................................... iii List of Figures.................................................................................................................. iii Acknowledgements..................................................................................................................... v Introduction...................................................................................................................................1 Nutrient Issues..............................................................................................................................4 Nitrogen Cycle ..................................................................................................................4 Phosphorus Cycle.............................................................................................................5 Light and Nutrient Limitation of Primary Productivity.............................................7 Environmental Setting.................................................................................................................8 Watershed Basins .............................................................................................................8 Existing and Historic Land Use......................................................................................8 Hydrology .......................................................................................................................15 Water Quality..................................................................................................................18 Nutrients..........................................................................................................................21 Nutrient Loads................................................................................................................21 Impaired (303d) Waters List .........................................................................................28 Biology .............................................................................................................................34 Summary of Critical Issues.......................................................................................................36 Freshwater Loads and Salinity .....................................................................................36 Nutrients and Eutrophication.......................................................................................37 Effects on Primary Productivity ...................................................................................38 Red Tides .........................................................................................................................40 Stormwater Management..............................................................................................41 Wastewater Discharges .................................................................................................41 Potential Nutrient Load Reduction Opportunities..............................................................42 Stormwater Best Management Practices.....................................................................42 Fertilizer Minimization.....................................................................................42 Livestock Fencing..............................................................................................43 Manure Management........................................................................................43 Erosion Control..................................................................................................43 Buffer Strips........................................................................................................43 Wet Detention Ponds ........................................................................................44 Retention Basins ................................................................................................45 Grassed Swales ..................................................................................................46 Florida Lawns ....................................................................................................46 Exfiltration Trenches.........................................................................................46 Temporary Sedimentation Basins/Traps.......................................................47 Treatment Wetlands..........................................................................................47 II CALOOSAHATCHEE RIVER/ESTUARY NUTRIENT ISSUE WHITE PAPER Enhanced Municipal Wastewater Treatment for Onsite and Point Source Discharges 48 Replacement of Septic Systems .......................................................................48 Tertiary Treatment ............................................................................................48 Treatment Wetlands..........................................................................................49 Comprehensive Everglades Restoration Plan (CERP) ..............................................49 Summary..........................................................................................................................50 References....................................................................................................................................51 Appendix