Effects of Groundwater on Salinity in Biscayne Bay

Transcription

1 Effects of Groundwater on Salinity in Biscayne Bay Sarah Bellmund1, Greg Graves2, Steve Krupa2, Herve Jobert3, Greg Garis1, and Steve Blair4 1Biscayne National Park Salinity Monitoring Program, Biscayne National Park, 97 SW 328th St, Homestead, FL., USA. 2South Florida Water Management District, 331 Gun Club Rd. West Palm Beach, FL USA 3Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 48 Rickenbacker Causeway, Miami, FL USA 4Miami-Dade County Department of Resources Management, 71 NW 1st Ct., Miami, FL USA

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3 Historical Sources of Freshwater to Central and Southern Biscayne Bay Rainfall Springs and direct groundwater discharge Transverse Glade Creek discharge Sheet flow surface runoff

4 Karst Features Historic Aerial Photography of a Spring and Seepage 1938 Freshwater Springs in Biscayne Bay, circa 191 "Springs of good water are common and wells are to be had by a comparatively small amount of digging. Many springs burst up through the bottom of the bay, and we see fresh water boiling up through the salt." J. Buck, 1877 (Buck, reprinted 1979)

5 Changes in Biscayne Bay Central Bay: From River, creek overland sheet flow and ground water springs to an area dominated by seasonal pulses of discharge from canals with permanently maintained openings to the ocean. South Bay: From short coastal stream, surface sheet flow and groundwater flows to pulsed canal discharge Extreme South Bay: Loss of overland flow due to construction of the railroad and then US Highway 1

6 Coastal Ridge and Transverse Glades Courtesy Dr. John Meeder and Peter Harlem and the South Florida Natural Resources Center

7 Changes Affecting the Ecosystems of Biscayne Bay No. Humans (millions) Year 19-2: Miami-Dade population increased over 3 orders of magnitude.?

8 Black Point Biscayne Bay Continuous Salinity Monitoring Network with seagrass coverage C-13 Convoy Point

9 High Salinity Areas Average Days Greater than 4 psu days days days days days days days Lighter colors are longer and higher hypersaline conditions

10 Grouped Salinity Convoy Point and Fender Point Convoy Point Mangroves Site 14: Dry Season Salinity in 2 ppt bins Convoy Point Mangroves Site 14: Wet Season Salinity in 2 ppt bins # of readings Site14DS4 Site14DS5 # of readings Site14WS4 Site14WS5 Site14WS Salinity (ppt) Salinity (ppt) Fender Point Mangroves Site 4: Dry Season Salinity in 2 ppt bins Fender Point Mangroves Site 4: Wet Season Salinity in 2 ppt bins # of readings Site4DS4 Site4DS Salinity (ppt) # of readings Site4WS4 Site4WS5 Site4WS Salinity (ppt)

11 Salinity Early Wet Season Compared to Peak Wet Season and October Drawdown June 24 June 25 June 27 June 26 June 27 October 24 October 25 October 26 October 27

12 /1/24 7/1/24 9/1/24 11/1/24 1/1/25 3/1/25 5/1/25 7/1/25 9/1/25 11/1/25 1/1/26 3/1/26 5/1/26 7/1/26 9/1/26 11/1/26 1/1/27 3/1/27 5/1/27 7/1/27 Date Discharge S-2F S-2G S-21A S21 How the managed coastal southern Biscayne Bay system operates Jul-4 Sep-4 Nov-4 Jan-5 Mar-5 May-5 Jul-5 Sep-5 Nov-5 Jan-6 Mar-6 May-6 Jul-6 Sep-6 Nov-6 Jan-7 Mar-7 May-7 Jul-7 Date Rain(inches S2F_rain S2G_rain S21A_rain Biscayne Bay Mangrove Salinity May- 24 Jul- 24 Sep- 24 Nov- 24 Jan- 25 Mar- 25 May- 25 Jul- 25 Sep- 25 Nov- 25 Jan- 26 Mar- 26 May- 26 Jul- 26 Sep- 26 Nov- 26 Jan- 27 Mar- 27 May- 27 Jul- 27 Date Salinity (psu Site 14 Site 22 Site 28 Site /1/24 7/1/24 9/1/24 11/1/24 1/1/25 3/1/25 5/1/25 7/1/25 9/1/25 11/1/25 1/1/26 3/1/26 5/1/26 7/1/26 9/1/26 11/1/26 1/1/27 3/1/27 5/1/27 7/1/27 Date Discharge S-2F S-2G S-21A S21 rainfall discharge salinity

13 Black Point Biscayne Bay Continuous Salinity Monitoring Network with seagrass coverage Site 34/35 C-13 Convoy Point

14 Aug 26 Phenomenon of fresher on bottom

15 Zoomed in Aug 1 thru Sept 5, 26 Avg top = 31.3 Difference (top bottom) Salinity Avg bottom = 3.3 Daily Canal Discharge Volume

16 Black Point Biscayne Bay Continuous Salinity Monitoring Network with seagrass coverage Site 18/19 C-13 Convoy Point

17 1 Aug 26 Phenomenon of fresher on bottom occurs elsewhere in Bay

18 Black Point Biscayne Bay Continuous Salinity Monitoring Network with seagrass coverage Site 54/55 C-13 Convoy Point

19 Aug 26 Phenomenon of fresher on bottom occurs elsewhere in Bay

20 Fresh groundwater moving up through the bottom of Biscayne Bay

21 Karst Cave in Watershed of the Deering Estate

22 Multiple investigators have measured similar flux rates for groundwater flow including: Krupa et al. Stalker et al. Bynne et al.

23 Seepage Rates and Salinity in Biscayne Bay from August 25 through February 26

24 AOML-Proni et al sites BISC - Bellmund Sites SFWMD- Krupa sites

25 SFWMD S-2F Structure Old Burger King Building Mowry Canal Site Burger King Seepage Site SFWMD Southern Site SFWMD Northern Site

26 Platform at Burger King Site Sea grasses and Seepage Meter at Burger King Site

27 Water Level in feet (1929 NGVD) Mowry Canal Combined Onshore and Offshore Ground Water Levels /1/5 Aug th Full Katrina 8/26/5 Sept 25 4th New 19 th Full 9/1/5 Rita 9/21/5 1/1/5 Oct 25 2nd New 2th Full Wilma 1/24/5 11/1/5 Nov 25 1 st New 17 th Full W9 GW-1 W9 GW-2 W1 GW-1 W1 GW-2 Dec 25 1st New 12/1/5 1/1/6

28 Mowry Canal Onshore and Offshore Groundwater Well Specific Conductivity S-2F Rainfall W1 GW-1 W1 GW Rainfall (inches/15 min) S-2F Rainfall W9 GW-1 W9 GW Specific Conductivity (µs/cm) /1/6 12/1/5 11/1/5 1/1/5 9/1/5 8/1/5

29 Mowry Canal Offshore Salinity 3 Salinity (ppt) 2 1 Inside KS A Inside KS B Outside KS A Outside KS B Platform Surface Platform Bottom 8/1/5 9/1/5 1/1/5 11/1/5 12/1/5

30 Mowry Canal Seepage Meter Fluxes. Offshore Groundwater Levels And Wind Direction /1/5 9/1/5 1/1/5 11/1/5 12/1/5 1/1/6 Water Level in feet (1929 NGVD) Flux (cm/day) W1 GW-1 Flux A (cm/day) Flux B (cm/day) -1-2 Wind Direction

31 Burger King Combined Onshore and Offshore Ground Water Levels W7 GW-1 W7 GW-2 W8 GW-1 W8 GW-2 1/1/6 2/1/6 3/1/6 4/1/6 5/1/6 Water Level in feet (1929 NGVD)

32 Burger King Onshore and Offshore Groundwater Well Specific Conductivity 51 Specific Conductivity (µs/cm) W8 GW-1 W8 GW-2 W7 GW-1 W7 GW-2 3 1/1/6 2/1/6 3/1/6 4/1/6

33 Biscayne Bay Mangrove Salinity Biscayne Bay Salinity Site 14 Site 22 Site 28 Site 4 Site 5 Site 56 Site Salinity (psu May- 24 Jul- 24 Sep- 24 Nov- 24 Jan- 25 Mar- 25 May- 25 Jul- 25 Sep- 25 Nov- 25 Jan- 26 Mar- 26 May- 26 Jul- 26 Sep- 26 Nov- 26 Jan- 27 Mar- 27 May- 27 Jul- 27 Date

34 2/6/26 1/3/26 1/23/26 1/16/26 1/9/ Inside KS A Outside KS A Inside KS B Outside KS B Platform Surface Burger King Offshore Salinity 12/1/5 11/1/5 1/1/5 9/1/5 8/1/ Inside KS A Inside KS B Outside KS A Outside KS B Platform Surface Platform Bottom Mowry Canal Offshore Salinity Salinity (ppt) Salinity (ppt)

35 Relationship Between Flow and Salinity from at Selected Sites BISC14 LogTotFlow = Mean1 BISC34 LogTotFlow = bisc S.4811 R-Sq 34.9% R-Sq(adj) 34.8% 4 3 S R-Sq 21.4% R-Sq(adj) 21.3% LogTotFlow 2 1 LogTotFlow Mean m from shore bisc m from shore BISC42 LogTotFlow = BISC42 BISC36 LogTotFlow = BISC S R-Sq 36.4% R-Sq(adj) 36.3% 4 3 S R-Sq 17.9% R-Sq(adj) 17.7% LogTotFlow 2 1 LogTotFlow BISC m from shore BISC m from shore 24-26

36 SFWMD and Biscayne National Park GW and Salinity Plotted Together

37 Conclusions Biscayne Bay was much fresher historically. Freshwater was and is distributed through the bay bottom as groundwater and is a source of freshwater most available to benthic communities. Total flux rates at the BK site are generally higher (2-3 times) than the MC site. Wind speed and direction plays a role in flux magnitude, direction, source of water (re-circulated SW or freshwater), and in turn the GW WQ contributions into the Bay. Despite large openings to the ocean the coastal environments of the bay are much fresher than expected. Empirical data are showing that things are very different than presupposed or modeled. Multiple empirical investigators show the same or very similar results, which are different than the operating hypotheses that have been applied to the Bay.

38 Final Conclusion: It is important to convene a meeting of all of the groundwater and Biscayne Bay salinity investigators to compare information and compile data in the same units and format.

39 The greatest obstacle to discovery is not ignorance It is the illusion of knowledge. Daniel Boorstin "You cannot solve problems with the same type of thinking used to create them." - Albert Einstein

40 Acknowledgements Amy Renshaw Ed Kearns Helen Mayoral Adam Wood Joe Serafy Elmar Kurzbach Rick Alleman Cynthia Gefvert National Park Service-South Florida Natural Resources Center U. S. Army Corps of Engineers Miami-Dade County DERM South Florida Water Management District National Park Service