Prepared in cooperation with the U.S. Army Corps of Engineers, South Florida Water Management District, and Florida Department of Agriculture and Consumer Services Concentrations and Loads of Nutrients in the Tributaries of the Lake Okeechobee Watershed, South-Central Florida, Water Years 2004–2008 Kissimmee River Lake Okeechobee Watershed Project area ATLANTIC OCEAN Lake Okeechobee GULF OF MEXICO Data Series 613 U.S. Department of the Interior U.S. Geological Survey Concentrations and Loads of Nutrients in the Tributaries of the Lake Okeechobee Watershed, S outh-Central Florida, Water Years 2004–2008 By Michael J. Byrne, Sr., and Molly S. Wood Prepared in cooperation with the U.S. Army Corps of Engineers, South Florida Water Management District, and Florida Department of Agriculture and Consumer Services Data Series 613 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Byrne, M.J., Sr., and Wood, M.S., 2012, Concentrations and Loads of Nutrients in the Tributaries of the Lake Okeechobee Watershed, South-Central Florida, Water Years 2004–2008: U.S. Geological Survey Data Series 613, 22 p. (available online at http://pubs.usgs.gov/ds/613). iii Contents Abstract ......................................................................................................................................................... 1 Introduction ................................................................................................................................................... 1 Purpose and Scope ............................................................................................................................ 3 Description of Study Area ................................................................................................................. 3 Previous Studies ................................................................................................................................. 3 Methods ......................................................................................................................................................... 6 Discharge ............................................................................................................................................. 6 Water-Quality Protocols .................................................................................................................... 6 Analytical Methods ............................................................................................................................. 7 Quality-Control Sampling and Requirements ................................................................................. 7 Load Calculation Procedures ........................................................................................................... 8 Nutrient Loads .............................................................................................................................................. 8 Discharge ............................................................................................................................................. 8 Nutrient Concentrations .................................................................................................................... 9 Computation of Loads ...................................................................................................................... 16 Acknowledgments ..................................................................................................................................... 22 References Cited ........................................................................................................................................ 22 Figures 1. Map showing location of the Lake Okeechobee Watershed Project area in Florida ..... 2 2. Map showing location of regional subwatershed, basins, and monitoring sites in the Lake Okeechobee Watershed Project area ................................................................ 4 3. Graph showing monthly rainfall measured at Peace River at Fort Meade and at Taylor Creek near Cypress Quarters ................................................................................... 8 4. Graphs showing monthly discharge at sites east of the Kissimmee River, 2004–2008 ................................................................................................................................... 10 5. Graphs showing monthly discharge at sites west of the Kissimmee River, 2004–2008 .................................................................................................... 14 6. Box plot of total phosphorus concentrations by site, 2004–2008 ..................................... 17 7. Box plot of total organic nitrogen plus ammonia concentration by site, 2004–2008 ................................................................................................................................... 17 8. Box plot of total nitrite plus nitrate concentrations by site, 2004–2008 ........................... 19 iv Tables 1. Description of monitoring sites in the Lake Okeechobee Watershed Project area ........ 5 2. Calibration acceptance criteria for field measurements ..................................................... 7 3. Analytical methods prescribed for water-quality constituents .......................................... 7 4. Quality control samples and requirements ............................................................................ 9 5. Summary of annual discharge in the Lake Okeechobee watershed, 2004–2008 ........... 16 6. Statistical analysis of nutrient concentrations in the Lake Okeechobee watershed, 2004–2008 .............................................................................................................. 18 7. Summary of annual nutrient loads in the Lake Okeechobee watershed, 2004–2008 ................................................................................................................................... 20 Conversion Factors, Abbreviations, and Datums Inch/Pound to SI Units Multiply By To obtain inch (in.) 2.54 centimeter inch per year (in/yr) 2.54 centimeter per year foot (ft) 0.3048 meter mile (mi) 1.609 kilometer square mile (mi2) 2.590 square kilometer (km2) acre 4,047 square meter acre-foot (acre-ft) 1,233 cubic meter cubic foot per second (ft3/s) 0.02832 cubic meter per second Vertical coordination information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29) and the North American Vertical Datum of 1988 (NAVD 88). Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27). Elevation, as used in this report, refers to distance above the vertical datum. v Acronyms ACS American Chemical Society ADCP acoustic Doppler current profiler ADVM acoustic Doppler velocity meter CERP Comprehensive Everglades Restoration Plan L liter LOWP Lake Okeechobee Watershed Project MT metric ton µg/L microgram per liter mg/L milligram per liter mL milliliter NO2 + NO3 Total nitrite plus nitrate SFWMD South Florida Water Management District TKN Total organic nitrogen plus ammonia TP Total phosphorus USACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency USGS U.S. Geological Survey WY water year Concentrations and Loads of Nutrients in the Tributaries of the Lake Okeechobee Watershed, South-Central Florida, Water Years 2004–2008 By Michael J. Byrne, Sr., and Molly S. Wood concentrations of nitrite plus nitrate ranged from 0.01 to 0.55 Abstract mg/L at the 16 tributaries during 2004–2008. Mean concentra- tions measured in priority basins were signifi cantly higher than Lake Okeechobee in south-central Florida is the second those measured in non-priority basins. largest freshwater lake in the contiguous United States. Nutrient concentrations were substantially lower in Excessive phosphorus loading, harmful high and low water the non-priority basins; however, total loads were substan- levels, and rapid expansion of non-native vegetation have tially higher due to discharge that was 5 to 6 times greater threatened the health of the lake in recent decades. A study than from the priority basins. Total phosphorus, organic was conducted to monitor discharge and nutrient concentra- nitrogen plus ammonia, and nitrite plus nitrate loads from tions from selected tributaries into Lake Okeechobee and to the non-priority basins were 1.5, 4.5, and 3.5 times greater, evaluate nutrient loads. The data analysis was performed at respectively, than were loads from the priority basins. 16 monitoring stations from December 2003 to September In the non-priority basins, total phosphorus loads ranged 2008. from 35 metric tons