Altered Hydroperiod and Saltwater Intrusion in the Bald
Altered Hydroperiod and Saltwater Intrusion in the Bald Cypress Swamps of the Loxahatchee River “Not So Deep” 20 th Saltwater Intrusion Meeting – Naples, FL – June 23 -27, 2008 David A. Kaplan 1, Rafael Muñoz-Carpena 1, Yuncong Li 2, Yongshan Wan 3, Marion Hedgepeth 3, and Dick Roberts 4 1 Agricultural and Biological Engineering, University of Florida and Water Science, University of Florida, Tropical Research and Education Center 3 South Florida Water Management District, Coastal Ecosystems Division 4 Florida Department of Environmental Protection, Division of Recreation and Parks 2 Soil Photo by Paul Lane
Introduction - Loxahatchee River Source: SFWMD 2005 Atlantic Ocean • 240 square mile (~620 km 2) watershed • Public lands = conserved ecosystems Ecologically diverse • National “Wild and Scenic River” (NPS) • Minimum Flows and Levels “…the last free-flowing river in southeast Florida…”
Introduction - Hydrology • Construction of the C-18 canal (1958) and minor canals that direct water away from the historic watershed – Reduces freshwater flow in the NW Fork severely • Permanent opening of the Jupiter Inlet (1947) • Lowering of the regional groundwater table C 14 Source: Loxahatchee River District
Introduction - Floodplain Vegetation
Introduction - Floodplain Vegetation
Introduction - Minimum Flows and Levels • Florida requires Water Management Districts to minimum flows and levels (MFLs) (Chapter 40 E-8 of the FAC) – protects water resource functions: flood control, water quality, water supply and storage, fish and wildlife protection, navigation, and recreation • MFLs linked to valued ecosystem components (VEC) – Intended to prevent “significant harm” – Lox VEC’s: FW floodplain swamp, downstream estuarine resources • Loxahatchee River MFL adopted in April 2003 – Intensive modeling effort, but only in river channel – Flow in NW Fork may not fall below 35 cfs for > 20 consecutive days within any calendar year – Required the development and implementation of a Recovery Plan
Introduction - Bald Cypress • Bald cypress (Taxodium distichum) life cycle requirements: Seeds Source: hiltonpond. org • Require moist soil, but will NOT germinate under water • Low germination rates, short viability • Germination reduced by increasing salinity • Seeds from brackish sources more tolerant Seedlings Source: Dr. Yuncong Li, UF, TREC • Growth and survival dependent on hydroperiod and salinity • Tolerates shallow flooding, but causes stress • Moderately salt tolerant (2 ppt) (Li et al. 2006) • Impacts of combined flooding and high salinity greater than either alone Mature Trees Copyright Raymond Gehman, 2005 • Highly flood tolerant • Salinity tolerance less well-established
Objectives • Characterize soil moisture and soil porewater salinity dynamics in the floodplain of the Loxahatchee River over several wet and dry seasons • Establish functional relationships between river stage and soil moisture and porewater salinity to better predict the effects of proposed restoration scenarios on the root zone of bald cypress Copyright Clyde Butcher, 1989
Materials and Methods • Two established vegetation transects chosen for monitoring soil moisture and salinity – Transect 1: “Unimpacted” riverine swamp dominated by mature bald cypress – Transect 7: Transitional riverine/ upper tidal swamp with mix of freshwater swamp species (bald cypress, red maple, cabbage palm) transitioning to red mangrove ~30 m from river
Materials and Methods • 24 combined dielectric probes (Stevens Hydra Probe) installed – Determines soil moisture and conductivity by measuring soil dielectric properties e = K e 0 K = er - i ei (1) (2) – εr q (m 3 m-3 ) εi sa (S/m) – Soil-specific calibrations by Mortl (2006) for sa sw (S/m) based on q – Soil moisture, porewater electrical conductivity, and temperature measured every 30 minutes
Results – Transect 1
Results – Transect 1 Distance along Transect 1 (m) Soil Map Unit Soil description by depth (cm) 0 -90: fine sand 25 Winder fine sand 90 -120: sandy clay loam Vegetation Station T 1 -60 cabbage palm, slash pine, bald cypress transition Station T 1 -50 Station T 1 -30 0 -30: clay 30 -50: sandy clay 65 Fluvent 50 -80: fine sand bald cypress, cabbage palm, red maple, water hickory 80 -120: loamy sand Soil Horizon (Transect) Field - ρb (g/cm 3)† Ks (cm/hr) † θr θs %C Fine sand (Tr. 1) 1. 36 ± 0. 18 (1. 06 - 1. 55) 37. 04 ± 7. 70 (29. 26 - 48. 42) 0. 04 0. 40 0. 45 (0. 1 -0. 48) Fluvent (Tr. 1) 0. 69 ± 0. 38 (0. 30 - 1. 22) 84. 33 ± 83. 52 (0. 81 - 166. 17) 0. 20 0. 90 11. 0 (1. 0 -15. 0) Source: Mortl (2006) Station T 1 -1
Soil Moisture – Transect 1 T 1 -60 T 1 -50 T 1 -30 T 1 -1
Soil Moisture – Transect 1 T 1 -60 T 1 -50 T 1 -30 T 1 -1
Soil Moisture – Transect 1 T 1 -60 T 1 -50 T 1 -30 T 1 -1
Soil Moisture – Transect 1 T 1 -60 T 1 -50 T 1 -30 T 1 -1
River Stage - qe Relationship • Conceptual Model – Sigmoidal Curve River Stage (m, NGVD 29) Source: www. hydram. epfl. ch
River Stage - qe Relationship (T-1) T 1 -60 River Stage (m, NGVD 29) T 1 -50 T 1 -30 T 1 -1
River Stage - qe Relationship (T-1) T 1 -60 River Stage (m, NGVD 29) T 1 -50 T 1 -30 T 1 -1
θe (-) River Stage - qe Relationship (T-1) T 1 -60 River Stage (m, NGVD 29) T 1 -50 T 1 -30 T 1 -1
River Stage - qe Relationship (T-1) Probe Depth - surface - middle qe (m 3/m 3) qe (-) - deep T 1 -60 T 1 -50 T 1 -30 T 1 -1 River Stage (m, NGVD 29)
River Stage - qe Relationship (T-1) T 1 -60 T 1 -50 T 1 -30 T 1 -1 elevation, distance River Stage (m, NGVD 29) Sensor A b c NS T 1 -60 (25 cm) 1 3. 913 0. 243 0. 72 T 1 -60 (35 cm) 1 3. 629 0. 153 0. 78 T 1 -60 (55 cm) 1 3. 326 0. 055 0. 66 T 1 -50 (30 cm) 1 3. 633 0. 161 0. 84 T 1 -50 (60 cm) 1 3. 414 0. 067 0. 89 T 1 -50 (95 cm) 1 3. 261 0. 063 0. 63 T 1 -30 (25 cm) 1 3. 014 0. 116 0. 42 T 1 -30 (50 cm) 1 2. 749 0. 121 0. 32 T 1 -30 (80 cm) 1 -- 0. 000 1. 00 T 1 -1 (25 cm) 1 3. 125 0. 086 0. 60 T 1 -1 (50 cm) 1 2. 759 0. 120 0. 42 T 1 -1 (72 cm) 1 -- 0. 000 1. 00 NS = Nash Sutcliffe Coefficient of Efficiency(1970)
Soil Porewater EC – Transect 1 D F C E • Salinity dynamics likely not tied to river salinity • Rainfall/ET driven • Concentration of salts in the floodplain
Results – Transect 7
Results – Transect 7 Distance along Transect 7 (m) Soil map unit Soil description by depth (cm) Vegetation 15 Terra Ceia Variant Muck 0 -40: muck young bald cypress, poison ivy 65 Terra Ceia Variant Muck 0 -180: muck 180: sand layer 0 -130: muck 145 Terra Ceia Variant Muck 130: sand layer Station T 7 -145 Station T 7 -90 pond apple, pop ash, bald cypress red mangrove, cabbage palm, swamp fern, pond apple Soil Horizon (Transect) Field - ρb (g/cm 3)† Ks (cm/hr) † θr θs %C Muck (Tr. 7) 0. 25± 0. 15 (0. 14 - 0. 54) 3. 05 ± 2. 29 (0. 23 - 7. 18) 0. 20 0. 90 20. 0 (5 -25) Source: Mortl (2006) Station T 7 -25 Station T 7 -2
Soil Moisture – Transect 7 • High tide elevation greater than all probe elevations all but one day (6/10/06) All probes flooded twice daily 15 -minute tide data from USGS station 265906080093500
River Stage - qe Relationship (T-7)
River Salinity at River Mile 9. 1 (T-7) 11. 8 ppt 2. 0 ppt Data from USGS Station 265906080093500 16. 1 ppt
River Salinity (T-7) — Stage (T-1) Relationship Lainhart Dam stage data from SFWMD’s DBHYDRO browser
Porewater Salinity – Transect 7 T 7 -145 T 7 -90 T 7 -25 T 7 -2
Porewater Salinity – Transect 7 T 7 -145 T 7 -90 T 7 -25 T 7 -2
Porewater Salinity – Transect 7 T 7 -145 T 7 -90 T 7 -25 T 7 -2
Porewater Salinity – Transect 7 T 7 -145 T 7 -90 T 7 -25 T 7 -2
River and Porewater EC Relationship (T-7) Percentage of Peak River EC Value Reached in Porewater Sensor 2005 2006 2007 T 7 -145 (20 cm) 4% 7% 12% T 7 -145 (40 cm) 1% 5% 10% T 7 -145 (67 cm) 0% 0% 3% T 7 -90 (23 cm) 7% 11% 10% T 7 -90 (40 cm) 7% 7% 13% T 7 -90 (60 cm) 6% 6% 12% T 7 -25 (23 cm) 6% 12% 23% T 7 -25 (46 cm) 6% 10% 20% T 7 -25 (66 cm) 6% 11% 18% T 7 -2 (16 cm) 6% 9% 18% T 7 -2 (32 cm) 5% 9% 15% T 7 -2 (48 cm) 7% 4% 12% Average 5% 8% 14% T 7 -145 T 7 -90 T 7 -25 T 7 -2
River and Porewater Salinity Lag (T-7) Time Lag (days): Sensor 2005 2006 2007 T 7 -145 (20 cm) 22 50 51 T 7 -145 (40 cm) 41 64 52 T 7 -145 (67 cm) --- 50 T 7 -145 (23 cm) --- 22 31 T 7 -145 (46 cm) --- 27 49 T 7 -145 (66 cm) --- 60 49 T 7 -145 T 7 -90 T 7 -25 T 7 -2
Conclusions – Soil Moisture • Variation in soil moisture is dominated by distance from river and topographical elevation of the floodplain and can be functionally tied to river stage at Transect 1. management tool • The floodplain at Transect 7 is inundated twice daily, though the effects of the daily tidal inundation on soil moisture can be seen over tidal cycle. seed germination; microtopography
Conclusions – Porewater EC • Increases in porewater salinity in the floodplain are related to the magnitude and duration of river salinity. • There is a time lag between river and porewater salinity peaks, which increases with elevation and distance from river. • Groundwater flow towards the river is likely very important to maintaining low EC levels in the floodplain porewater Next steps! GW data analysis, dynamic factor analysis, hydro-ecological modeling?
Acknowledgements • • Funding for this project provided by the South Florida Water Management District Ph. D. Committee: Rafael Muñoz-Carpena, Gregory Kiker, Thomas Crisman, Yuncong Li, Yongshan Wan Previous work by Amanda Mortl (UF Masters Thesis) Thanks to the rest of the research team that collaborated in the field and laboratory efforts: – Paul Lane and Lindsey Nolan (UF/ABE) – Guodong Liu, Qingren Wang, Newton Campbell, Tina Dispenza, and Harry Trafford (UF TREC) – Marion Hedgepath, Yongshan Wan, Fawen Zheng (SFWMD), Dick Roberts and Jeff Fisher (JDSP, FDEP), and Kevin Sullivan (NRCS) – Additional field assistance by Zuzanna Zajac, Stuart Muller, Jonathan Schroeder, Daniel Preston, Karl Van. Derlinden, Axel Ritter, Johanna Freeman, Roger Freeman. • Special thanks to the SWIM Organizing Committee for providing travel funds!!!
Questions? Photo by Paul Lane
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