Water Quality in Big Cypress National Preserve and Everglades National Park—Trends and Spatial Characteristics of Selected Constituents By Ronald L. Miller, U.S. Geological Survey, St. Petersburg, Florida; Benjamin F. McPherson, U.S. Geological Survey, Tampa, Florida; and Robert Sobczak, and Christine Clark, Big Cypress National Preserve, Ochopee, Florida Water Resources Investigations Report 03-4249 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey, Reston, Virgina: 2004 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication 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 repro- duce any copyrighted materials contained within this report. iii Contents Abstract. 1 Introduction . 2 Data Sources . 4 Objective and Scope . 4 Data Analysis . 4 Problems in Long-Term Trend Analyses. 5 Statistics . 5 Trends in Rainfall, Water Levels, and Flows . 6 Water Quality in South Florida . 8 Water Quality Changes Over Time. 9 Eastern Everglades . 9 Taylor Slough Bridge. 9 Shark River Slough. 11 Western Everglades and Big Cypress Swamp . 11 Site P-34 . 15 Bridge 105 Site. 15 Spatial Patterns in Water Quality . 18 Park Boundary Water-Quality Conditions . 18 L-28 Interceptor (L-28I) Drainage System . 18 Barron River Canal. 18 S-12s Gated Structures. 19 L-31 Canal and C-111 Canals . 19 Median Concentrations of Selected Constituents . 19 Trace Elements in Water. 25 Pesticides and Other Organic Compounds in Water. 28 Pesticides and Other Organic Compounds in Bed Sediment. 28 Water-Quality Monitoring Network Design for Future Studies. 31 Summary. 31 References. 32 Figures 1. Map showing Big Cypress National Preserve and Everglades National Park with major features and sampling sites . .2 2. Timeline showing major human and climatic events that might affect water quality . .3 3-13. Graphs showing: 3. Average annual rainfall at 20 sites in south Florida . .7 4. Average monthly water elevation in feet above NGVD29 at wells S-196 and S-196A near Homestead, Florida . .7 5. Average annual discharge under the Tamiami Trail. .8 6. Average annual discharge at S-332. .9 iv 7. Stage (water level) and water-quality data with loess smooth lines for period of record at Taylor Slough Bridge . .10 8. Variation in stage and concentration of total phosphorus with time, and variation of concentration of total phosphorus with discharge at Taylor Slough Bridge. 12 9. Stage (water level) and water-quality data with loess smooth lines for the period of record at P-33. 13 10. Concentration of sulfate at P-33 and discharge under Tamiami Trail; sulfate at P-33 and stage; total phosphorus at P-33 and stage; and chloride concentration at P-34 and stage. 14 11. Stage (water level) and water-quality data with loess smooth lines for period of record at P-34. 16 12. Stage (water level) and water-quality data with loess smooth lines for period of record at Bridge 105 and 40-Mile Bend section. 17 13. Stage (water level) and concentration and water level at Bridge 105 and concentrations of sulfate (times 100) and total phosphorus (times 1,000) at Bridge 105 from January 1996 to January 1999. 18 14-20. Maps showing: 14. Median specific conductance at Big Cypress National Preserve and Everglades National Park sites and nearby canal sites, 1991-2000. 20 15. Median chloride concentrations at Big Cypress National Preserve and Everglades National Park sites and nearby canal sites, 1991-2000. 21 16. Median sulfate concentrations at Big Cypress National Preserve and Everglades National Park sites and nearby canal sites, 1991-2000 . 22 17. Median total phosphorus concentrations at Big Cypress National Preserve and Everglades National Park sites and nearby canal sites, 1991-2000. 23 18. Median total nitrogen concentrations at Big Cypress National Preserve and Everglades National Park sites and nearby canal sites, 1991-2000. ..