Transcript Altered Hydroperiod and Saltwater Intrusion in the Bald Cypress Swamps of the Loxahatchee River “Not So Deep” 20th Saltwater Intrusion Meeting – Naples,

Altered Hydroperiod and Saltwater Intrusion in the
Bald Cypress Swamps of the Loxahatchee River
“Not So Deep”
20th Saltwater Intrusion Meeting – Naples, FL – June 23-27, 2008
David A. Kaplan1, Rafael Muñoz-Carpena1, Yuncong Li2, Yongshan Wan3, Marion
Hedgepeth3, and Dick Roberts4
1Agricultural
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
2Soil
Photo by Paul Lane
Introduction - Loxahatchee River
Source: SFWMD 2005
Atlantic
Ocean
• 240 square mile (~620 km2)
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
C14
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 40E-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 e0
K = er - i ei
– εr  q (m3 m-3 )
(1)
(2)
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 T1-60
cabbage palm,
slash pine, bald
cypress
transition
Station T1-50
Station T1-30
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/cm3)†
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 T1-1
Soil Moisture – Transect 1
T1-60
T1-50
T1-30
T1-1
Soil Moisture – Transect 1
T1-60
T1-50
T1-30
T1-1
Soil Moisture – Transect 1
T1-60
T1-50
T1-30
T1-1
Soil Moisture – Transect 1
T1-60
T1-50
T1-30
T1-1
River Stage - qe Relationship
• Conceptual Model – Sigmoidal Curve
q  qr
qe 
qs  qr
qe 
A
 x  b
1  exp  


c 
River Stage (m, NGVD29)
Source: www.hydram.epfl.ch
River Stage - qe Relationship (T-1)
T1-60
River Stage (m, NGVD29)
T1-50
T1-30
T1-1
River Stage - qe Relationship (T-1)
T1-60
River Stage (m, NGVD29)
T1-50
T1-30
T1-1
θe (-)
River Stage - qe Relationship (T-1)
T1-60
River Stage (m, NGVD29)
T1-50
T1-30
T1-1
River Stage - qe Relationship (T-1)
Probe Depth
- surface
- middle
qe (m3/m3)
qe (-)
- deep
T1-60
T1-50
T1-30
T1-1
River Stage (m, NGVD29)
River Stage - qe Relationship (T-1)
T1-60
qe 
T1-50
T1-30
T1-1
elevation, distance
River Stage (m, NGVD29)
A
 x  b
1  exp  


c 
Sensor
A
b
c
NS
T1-60 (25 cm)
1
3.913
0.243
0.72
T1-60 (35 cm)
1
3.629
0.153
0.78
T1-60 (55 cm)
1
3.326
0.055
0.66
T1-50 (30 cm)
1
3.633
0.161
0.84
T1-50 (60 cm)
1
3.414
0.067
0.89
T1-50 (95 cm)
1
3.261
0.063
0.63
T1-30 (25 cm)
1
3.014
0.116
0.42
T1-30 (50 cm)
1
2.749
0.121
0.32
T1-30 (80 cm)
1
--
0.000
1.00
T1-1 (25 cm)
1
3.125
0.086
0.60
T1-1 (50 cm)
1
2.759
0.120
0.42
T1-1 (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
15
Terra Ceia
Variant Muck
65
Terra Ceia
Variant Muck
Soil
description by
depth (cm)
Vegetation
0-40: muck
young bald
cypress, poison
ivy
0-180: muck
180: sand layer
0-130: muck
145
Terra Ceia
Variant Muck
130: sand layer
Station T7-145
Station T7-90
pond apple,
pop ash, bald
cypress
red mangrove,
cabbage palm,
swamp fern,
pond apple
Soil Horizon
(Transect)
Field - ρb
(g/cm3)†
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 T7-25
Station T7-2
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
T7-145
T7-90
T7-25
T7-2
Porewater Salinity – Transect 7
T7-145
T7-90
T7-25
T7-2
Porewater Salinity – Transect 7
T7-145
T7-90
T7-25
T7-2
Porewater Salinity – Transect 7
T7-145
T7-90
T7-25
T7-2
River and Porewater EC Relationship (T-7)
Percentage of Peak River EC Value
Reached in Porewater
Sensor
2005
2006
2007
T7-145 (20 cm)
4%
7%
12%
T7-145 (40 cm)
1%
5%
10%
T7-145 (67 cm)
0%
0%
3%
T7-90 (23 cm)
7%
11%
10%
T7-90 (40 cm)
7%
7%
13%
T7-90 (60 cm)
6%
6%
12%
T7-25 (23 cm)
6%
12%
23%
T7-25 (46 cm)
6%
10%
20%
T7-25 (66 cm)
6%
11%
18%
T7-2 (16 cm)
6%
9%
18%
T7-2 (32 cm)
5%
9%
15%
T7-2 (48 cm)
7%
4%
12%
Average
5%
8%
14%
T7-145
T7-90
T7-25
T7-2
River and Porewater Salinity Lag (T-7)
Time Lag (days):
Sensor
2005
2006
2007
T7-145
(20 cm)
22
50
51
T7-145
(40 cm)
41
64
52
T7-145
(67 cm)
---
---
50
T7-145
(23 cm)
---
22
31
T7-145
(46 cm)
---
27
49
T7-145
(66 cm)
---
60
49
T7-145
T7-90
T7-25
T7-2
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 VanDerlinden, Axel Ritter, Johanna Freeman, Roger Freeman.
•
Special thanks to the SWIM Organizing Committee for providing travel funds!!!
Questions?
Photo by Paul Lane