Loxahatchee

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PROJECTS North Palm Beach County Arthur R. Marshall Loxahatchee Internal Canal Structures

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Overview

Projects to improve water deliveries to the Loxahatchee River and Slough and the ARM Loxahatchee National Wildlife Refuge (which includes WCA-1) have the potential to improve habitat values in these areas. DOI has a great interest in ensuring that the quality, timing, and distribution of the additional water dedicated to these natural systems is suitable for natural system restoration. New local basin hydrologic and ecological models, to be integrated with the CERP models, will aid in understanding the effects of hydrologic change on habitats and species in this area. The use of water from stormwater treatment areas to augment flows to the wildlife refuge raises concerns about phosphorus and other contaminants The ecological responses to hydrologic change will be monitored to help ensure the desired responses and to avoid inadvertent impacts to fish and wildlife. Species of special concern include the eastern indigo snake and Everglade snail kite.

DOI managers can most effectively participate in CERP projects during three project stages: (1) NEPA scoping in the early stages of project design, to help ensure that hydrologic targets accurately reflect the natural predrainage conditions, (2) review of project alternatives, to ensure that fish and wildlife and parks are adequately considered in compliance with DOI mandates, and (3) monitoring and assessment of project results, to support project modification if needed to ensure that the intended conditions are achieved. The major questions that DOI managers need to answer at each stage to effectively fulfill their responsibilities as partner and steward are summarized below, along with the highest priority science needs for answering those questions. This information is discussed in greater detail for each individual project following this summary.

SUMMARY OF DOI RESPONSIBILITIES AND SCIENCE NEEDS RELATED TO WATER PROJECTS IN THE LOXAHATCHEE AREA

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North Palm Beach County Part 1

Project Purpose and Major DOI Interest. The North Palm Beach County Part 1 Project is a complex set of interrelated but separable components of the CERP² covering about 40,000 acres in northern Palm Beach and southern Martin Counties. The purposes of the project are to increase water supplies to the municipalities of northern Palm Beach County, provide increased flows to enhance hydroperiods in the Loxahatchee Slough, increase base flows to the Northwest Fork of the Loxahatchee River, and reduce high freshwater discharges to the Lake Worth Lagoon. When completed in 2014, this 12-year project will provide environmental, urban, and agricultural water supplies, flood attenuation, and water quality improvement for north Palm Beach County.

The water dedicated to the natural system will help restore wetlands in Loxahatchee Slough and restore more natural flows to the Northwest Fork of the Loxahatchee River, which is Florida's only designated wild and scenic river. An almost contiguous greenbelt extends from the state-owned DuPuis Reserve in the west, to the Jonathan Dickenson State Park in the northeast, and southward to the Grassy Waters Preserve. Eighteen federally listed plant and wildlife species occur within the project area, two of which, the Everglade snail kite and the eastern indigo snake, are species of special concern because little is known about their life histories within this project region. Proposed alterations to water flow, water depth, inundation period, flood frequency, and water quality will affect the snail kite's primary prey, the apple snail, resulting in impacts to the bird's foraging strategy and ultimately to its nesting success.

What Is Known
Several local-basin water-transport models are under development and will be used to inform the project design. The two primary water-transport models under consideration for this project are the RSM and the Lower East Coast Regional (LECR) Model. The Corps and SFWMD are currently combining these two models with watershed-specific models developed for this region to accurately predict the hydrologic effects on the natural system from alterations to the existing water delivery system.

Numerous ecological databases are available for the north Palm Beach County area, although incorporating this data and new information into a more comprehensive habitat map is part of what is needed in order to plan effectively for protection of species in this area. Snail Kite and Indigo snakes either occur or are likely to occur in this area given the knowledge base on these species habitat needs and preferences. Long- term snail kite monitoring occurs in the Grassy Waters Preserve, where nest success within the preserve is being documented.

What Is Needed
Regional integration of water transport and ecological models. DOI scientists will use the best available information to predict the ecological responses to the project performance targets during project design. Regional integration of the local hydrologic models and creation of ecological models that describe the effects of water allocations on fish and wildlife are longer term science needs. Although ecological models will not be available during the project design phase, through modification from incorporation of new information currently being collected they will eventually provide improved information to be used by the project managers to better predict the ecological benefits or adverse affects of adaptive management strategies. The integration of hydrologic and ecological models on a regional level will provide a critical tool necessary to ensure consistent decision making by the many federal management agencies in the region working to restore ecological sustainability.

Population and habitat utilization data about threatened eastern indigo snake and endangered Everglade snail kite. Studies to document the presence, abundance, population size, breeding potential and other life history characteristics of these species throughout the project area will fill these gaps in existing databases and provide improved baselines for considering impacts on these species.

Inventory and monitoring of all federally listed species. A complete inventory of all federally listed species in the project area will allow managers to adequately consider the multi-species effects of this restoration project. GIS map layers and databases for each species' occurrence, range, and abundance will be compiled in a centralized location for multiagency use.

DOI will track the effects of changes in hydrology, specifically hydration of upland or transitional communities, on the federally listed species in the project area. DOI will provide this information to the RECOVER team during the evaluation and adaptive management phase of this project.

Flows into the Arthur R. Marshall Loxahatchee NWR Including Internal Canal Structures and STAs

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The refuge, located in Palm Beach County, represents one of the last vestiges of the historic soft-water Everglades. Much of the Everglades developed as a rainfall-driven system with surface waters low in nutrients (such as phosphorus and nitrogen) and ions (such as sodium and calcium). This low-conductivity, or soft-water, condition was a major determinant of the historic ecosystem structure and function. The base of much of the refuge food chain is a unique, diverse periphyton assemblage that has developed under these soft-water conditions. The low conductivity waters are also associated with lower rates of key ecosystem processes, such as decomposition, than what occur in areas of the Everglades with higher conductivity waters (e.g., areas impacted by canal discharges).

The STAs will discharge water in new locations in the refuge and the DOI is concerned about the quality of the water from the STAs that will occur at these new locations. Because the Internal Canal Structures also will change how water moves from the canals into the interior of the refuge, that restoration project have the potential to change refuge water quality and subsequently refuge flora and fauna. Although the ecological impacts associated with increased surface water phosphorus concentrations in the Everglades are well recognized, the ecological impacts associated with an increased conductivity are not understood. However, information from other wetlands indicates that increases in conductivity may elicit undesirable ecological changes. Potential impacts in the refuge include changes to the periphyton community, which in turn may result in changes in populations and communities of primary consumers, such as apple snails, and subsequently of species such as the Everglade snail kite, which feeds on the snails.

A secondary related concern is how the water will be distributed in terms of depths and duration of depths, since changes in the depth of water and the amount of time an area is flooded can affect plant communities and critical habitats such as tree islands, wet prairies, and sloughs. The current water regulation schedule has been in place since 1995. Current operational issues, development of STAs, and water quality constraints were not foreseen when the schedule was developed. The current schedule needs to be reviewed in the context of current and projected future constraints and operational issues in order to insure that the appropriate quantity, timing, and distribution of clean water are provided to the refuge.

Refuge managers need to understand how water quality and quantity affect refuge resources in order to provide appropriate operational targets to the USACE prior to project design and suggested modifications to the refuge regulation schedule if appropriate. The appropriate targets need to address the management goal of restoring and conserving the natural diversity, abundance, and ecological function of refuge flora and fauna, as outlined in the refuge's 2000 Comprehensive Conservation Plan and agreed to in the terms of the current license agreement with the SFWMD. An important DOI role in this project is to provide technical input during project planning and design to ensure that the project is designed and implemented in a way that will not harm existing resources while accomplishing the objectives of improving water delivery in other parts of the refuge.

What Is Known
Information about the current hydrologic conditions in the refuge is well documented and provides a good baseline for analysis of any changes related to implementation of this project.

It has long been known that the fringes of the refuge are affected by high conductivity canal water. More recent evidence indicates a trend towards increased intrusion of this water into the refuge interior with noticeable impacts on water chemistry and sensitive biota. DOI managers and scientists have expressed concern over the spread of such impacts and their relationship to water management activities including operation of the STAs and meeting the requirements in the current water regulation schedule.

What Is Needed
Synthesis and integration of data about historic hydrologic and ecological conditions on the refuge. Data about historic hydrologic, water quality, and ecological conditions will be needed to develop the specific hydrologic targets for the project.

Research to understand the ecological effects of hydrology and water quality on refuge resources. CERP project managers and refuge managers will need information that relates conductivity and the pattern and duration of water depths within the refuge to changes that will occur with the project and other changes in water management as a basis for project design and adaptive management. Both a synthesis of past data and collection of current data are needed.

Gradient studies that focus on community change (invertebrate and plant communities especially) are needed for identifying reliable indicators of water quality in this soft water system and monitoring to detect undesirable changes in the NWR marsh system.

Development of an integrated hydrodynamic and water quality model. The most appropriate tool for making evaluations that have both water quality and water quantity components is an integrated hydrodynamic and water quality model. The development and refinement of this model will require additional information about the spatial patterns of conductivity within the refuge and the relationship of those conductivity patterns to periphyton, aquatic communities, and endangered species.

Monitoring and assessment of responses. Establishment of pre- and post-project monitoring protocols for hydrology, water quality including phosphorus and conductivity, periphyton, aquatic communities, and habitats will provide data that can be used to assess whether the project is having the desired effect. Coupled with mesocosm experiments, these data can be used to understand how changes in water quality and quantity, due to water management actions, affect refuge resources.

² The North Palm Beach County project is composed of six separable elements including Pal-Mar and J.W. Corbett Wildlife Management Area Hydropattern Restoration (including Loxahatchee River Restoration), L-8 Basin Modifications, C-51 and L-8 Reservoir, Lake Worth Lagoon Restoration, C-17 Back-pumping and Treatment, and C-51 Back-pumping and Treatment.