1. Establishing Baseline Freshwater Flow to Florida Bay for Water Management Operations
Joel VanArman
Water Supply Planning and Development Division
South Florida Water Management District
Robin Bennett, Chelsea Donovan and David Rudnick
Florida Bay and Lower West Coast Division
South Florida Water Management District
Biological Suitability
Widgeon grass (Ruppia maritima) poor suitability defined as percent days for the period of record ( ), drought water year (1990), and the wet water year (1995) between 0-12. Histograms were developed for northeastern Florida Bay (Joe Bay and Taylor River), north central Florida Bay (Little Madeira and Terrapin Bay), and Whitewater Bay (Clearwater Pass) from SFWMM-derived data.
P35
P33
S18C
TSB
S175
S332 WE CW SR NR
EPS TR CP
P37 WB MK TB GB JB LM
S197 LS
Legend
Structures
Stage Stations
MMN Stations
Shark River Slough
Taylor Slough
C-111
12A
12B
12C
12D
S333
Salinity in Florida Bay and Whitewater Bay generally showed stronger correlation with upstream wetland stage (calculated as a 30d moving average value) than with flows from canals.
EPS and P37 were used to predict salinity in eastern and central Florida Bay sites. P33 was used to predict salinity in Whitewater Bay. These stations were chosen after evaluating correlations against salinity data and the goodness of fit of SFWMM-derived stage.
Results
American crocodiles (Crocodylus actus) poor habitat suitability defined as percent days per critical hatchling/juvenile period (Aug-Dec) where salinity is greater than 20 during the 31-year period ( ). Histograms were developed for Terrapin Bay and Little Madeira Bay (as well as Garfield Bight, Taylor River and Joe Bay, not shown) from SFWMM-derived data. 90 70 60 50 40 30 20 10 80
BACKGROUND
Determine relationships among upstream flow, stage, and Florida Bay and Whitewater Bay salinity regimes with regression models.
Identify key biological components that have demonstrated salinity tolerances or optima.
Describe the habitat suitability for biological components in Florida Bay and Whitewater Bay as a function of salinity regime (modeled using SFWMM-derived stage data).
Two assessments of the relationship between freshwater flow through the Everglades and the ecological status of Florida Bay and Whitewater Bay are underway at the South Florida Water Management District (SFWMD). Though the objective of both efforts is resource identification and protection, they are derived from different mandates and management objectives.
The first exercise, defining “Existing Legal Sources” of water is required by the Water Resources Development Act of 2000 to protect baseline (pre-restoration) flows into receiving waters during the implementation of CERP. The second effort, defining “minimum flows and levels” (MFLs) for “priority” water bodies, is mandated by Florida Statute (section ) to protect water resource functions from incurring “significant harm.”
Methods
Legal Sources- The definition of existing Legal Sources is an assessment establishing the baseline (pre-restoration, up to December 2000) input (timing and distribution) of water to Florida Bay, and the extent to which the baseline delivery is beneficial to the ecosystem.
Parameters
Daily salinity data from 12 ENP Marine Monitoring Network near- shore stations
Wetland stage data from 5 stations
Structure flow data from Shark River Slough, Taylor Slough, and C-111.
Objective:
Identify the amount of water delivered to Florida Bay that is beneficial.
Determine the relationship between upstream flow, stage, Florida Bay and Whitewater Bay salinity by linear regressions.
Identify the biological responses to salinity regime using best available information.
SFWMM (2X2) stage data
Evaluate modeled vs. real stage ( for most stations)
Use best modeled stage station to hindcast salinity for period
Biological components
Use salinity and stage frequency distributions (by water year) to evaluate “habitat suitability” for biological resources for 31yr. period.
Compare modeled ecological “suitability” with real salinity data for drought (WY90) & wet (WY95) periods.
Fish
Spotted seatrout
Forage spp. (2-3)
Roseate Spoonbills
Water level for foraging efficiency
Salinity for foraging fish productivity
SAV:
Ruppia
Halodule
Thalassia
Crocodiles (juveniles)
Pink Shrimp
SRS vs. P35 & P33 vs. Clearwater, Shark River,
North River, Whitewater Bay
C-111 & TS vs. EPS & P37 vs Long Sound, Joe Bay, Taylor River, Little Madeira Bay
SRS vs. CP & P35 & P33 vs. Murray Key
TS vs. CP & P37 vs. Terrapin Bay, Whipray Basin, Garfield Bight
Whitewater Bay
Western Florida Bay
Central Florida Bay
Northeastern Florida Bay
Low salinities that occurred during the high water period of provided a more beneficial habitat for juvenile crocodiles, spotted seatrout, widgeon grass, and foraging fish species. Deleterious effects from high water events to roseate spoonbill populations could be ameliorated by improving the spatial and temporal distribution of these flows to approach historic conditions.
For the Legal Sources assessment, pre-CERP baseline flows of freshwater to Florida Bay were beneficial to the ecosystem (in terms of water quantity), especially if improvements can be made to the spatial distribution of these existing flows.
Discussion
Minimum Flows & Levels- The Minimum Flow or Level is defined as the “...limit at which further withdrawals would be significantly harmful to the water resources or ecology of the area". Florida Bay is designated as a MFL Priority Water Body, set for MFL rule adoption by 2005.
Map of southern Florida depicting upstream SFWMD flow structures, Everglades National Park (ENP) stage stations, and the ENP Marine Monitoring Network stations used for the Legal Sources assessment.
*Harm criteria are applied using climate conditions that represent an assumed 1 in 10 year level of certainty.
Water Distribution (Human and Environmental Uses)
Minimum Flows & Levels
Water Reservations for the Environment ( , F.S.)
Water Restrictions Phase I ( , F.S.)
Water Restrictions Phase II ( , F.S.)
Water Restrictions Phase III ( , F.S.)
Water Restrictions Phase IV ( , F.S.)
Water Level and Flow Decreasing
Drought Severity Increasing
Water Availability
Water Management Statutes
No Harm Environmental Restoration
Harm Recovery will occur within 1 or 2 seasons.
Significant Harm Requires more than two years for the water resources to recover.
Serious Harm Permanent or irreversible damage to the water resource.
Environmental Response
Conceptual Relationships Among Terms Related to Resource Impacts
For the development of MFL criteria, a “significant harm” standard will be used to assess salinity response by a variety of biological components. This resource-based approach has been employed to establish MFLs for other ecosystems of the Greater Everglades, including the St. Lucie River & Estuary, the Caloosahatchee River & Estuary, the Loxahatchee River, Lake Okeechobee, and the wetlands of Everglades National Park and the Water Conservation Areas.
Development of MFL criteria for Florida Bay will be assisted by other ongoing efforts, including the assessment of Legal Sources, development of better salinity prediction models for the Florida Bay and Florida Keys Feasibility Study (FBFKFS), and the definition of restoration targets from the FBFKFS and other CERP projects.
SUMMARY
The definition of existing Legal Sources and the development of MFL criteria should not be viewed as end points in identifying restoration flows for Florida Bay and Whitewater Bay. They represent different methods of describing baseline conditions in order to protect these water resources: MFLs define a baseline amount of water to avoid significant harm to the resources, while Legal Sources identify baseline (pre-restoration) water conditions that must be protected during CERP implementation. As such, they are important processes towards a goal of restoration.