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Progress Toward Restoring the Everglades: The Third Biennial Review - 2010 (2010)

Chapter: 4 Challenges in Restoring Water Timing, Flow, and Distribution

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Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

4
Challenges in Restoring Water Timing, Flow, and Distribution

As discussed in Chapter 2, Everglades restoration is premised on “getting the water right” by striving to reestablish the quality, flow, timing, and distribution of freshwater that characterized pre-drainage South Florida ecosystems. Addressing the disparate hydrological requirements of the diverse wetland communities that comprise the greater Everglades ecosystem demands highly integrated water resource planning and adaptive re-engineering and re-operating of the Central and South Florida (C&SF) Project.

Restoration at this scale involves many uncertainties, constraints, and tradeoffs. In the next two chapters, short-term priorities and longer-term plans for restoring surface flows and water quality are examined. The discussion of surface hydrology in this chapter focuses on the kinds of tradeoffs that are, of necessity, being made in re-distributing water to different parts of the Everglades, and considers the risks associated with incomplete restoration or long delays in providing storage capacity and additional water. The committee focused special attention on Water Conservation Area (WCA) 3 as an example of these challenges because it serves as the main flow-way of water through the remnant Everglades. WCA-3 provides habitat for important Everglades species and system features, and it is a nexus for many contentious Everglades water flow issues. Also, flows in Everglades National Park and WCA-3 are interdependent because of their adjacent geographic locations. Current water quality concerns and regulations, the cost and performance of source control and treatment alternatives, and the considerable technical and economic challenges of bringing existing and planned Comprehensive Everglades Restoration Plan (CERP) flows into compliance are summarized in Chapter 5.

PAST AND FUTURE CHANGES TO SOUTH FLORIDA’S WATER BUDGETS AND FLOW REGIMES

The hydrologic result of the Central & South Florida Project in the Everglades portion of the drainage basin south of Lake Okeechobee was a near-total

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

transformation of the flow system (USACE and SFWMD, 1999). The impacts of these changes to the landscape and the ecosystem are described in detail in Chapter 2, but the quantitative changes in hydrology are discussed further in this section to provide a basis for additional discussion of improving water flow and distribution.

A comparison between pre- and post-drainage water budgets of the Kissimmee-Okeechobee-Everglades watershed (Figures 4-1 and 4-2) shows how the distributions of water storage and transfers are believed to have changed. Some of the key features of these modeled water budgets are summarized in Table 4-1 according to Natural Systems Model (NSM) version 4.6.2 and the South Florida Water Management Model (SFWMM) version 5.4 (see Box 4-1). Comparable water budgets based on the newer South Florida Regional Simulation Model (RSM) are not yet possible because of model development issues discussed in Chapter 6. The water budget models have considerable uncertainty associated with estimating evapotranspiration and specific values of water flows from one compartment to another, and the models are used here as generalizations rather than as exact accountings.

According to the SFWMM, on average Lake Okeechobee discharges approximately 11 percent less water south under current conditions (554,000 acre-feet/year) compared to pre-drainage flows (622,000 acre-feet/year; see Figures 4-1 and 4-2). Total inflow to the WCAs ranges widely with the models used. The SFWMM v. 5.4 calculates that current water inflows from the north to the WCAs (1.3 million acre-feet [MAF]/year) exceed that which would have occurred via sheet flow in the pre-drainage system (1.06 MAF per year; NSM v. 4.6.2). However, the new Natural System Regional Simulation Model (NSRSM) depicts a wetter pre-drainage Everglades in which 1.5 MAF flowed from Lake Okeechobee into what is now the Everglades Agricultural Area (EAA) and at least 1.7 MAF flowed from the north into the current WCAs, across their northern boundaries (J. Obeysekera, SFWMD, personal communication, 2009).

Roughly 1.9 MAF per year still enters the WCAs across the western, northern, and eastern boundaries under current conditions (see Figure 4-2), but inflow now occurs primarily through canal or stormwater treatment area (STA) discharges, unlike in pre-drainage conditions when direct precipitation and occasional overflows from Lake Okeechobee dominated freshwater inputs (Harvey and McCormick, 2009). Surface-groundwater exchanges were minimal in the relatively flat, peat-covered, pre-drainage landscape. In contrast, peat subsidence, canals, and levees have created local hydraulic gradients that increase seepage and surface-groundwater interactions. As a result, after losses by evaporation, the WCAs now lose nearly half their remaining water through seepage to coastal areas. In addition, the loss of peat through oxidation has accentuated groundwater losses by permitting movement of surface water downward. The thick

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-1 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin, 1965–2000, under pre-drainage and pre-development conditions, calculated using the Natural System Model (NSM) version 4.6.2, which simulates regional hydrology in the absence of existing control structures. The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year, based on model simulations using a 36-year precipitation data set. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

FIGURE 4-1 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin, 1965–2000, under pre-drainage and pre-development conditions, calculated using the Natural System Model (NSM) version 4.6.2, which simulates regional hydrology in the absence of existing control structures. The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year, based on model simulations using a 36-year precipitation data set. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

SOURCE: J. Obeysekera, SFWMD, personal communication, 2009.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-2 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin under post-drainage and post-development conditions, calculated using a 36-year simulation using the SFWMM with structures in place as of 2000 (usually considered the typical “current” situation). The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year, based on model simulations using a 36-year precipitation data set. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

FIGURE 4-2 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin under post-drainage and post-development conditions, calculated using a 36-year simulation using the SFWMM with structures in place as of 2000 (usually considered the typical “current” situation). The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year, based on model simulations using a 36-year precipitation data set. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

SOURCE: J. Obeysekera, SFWMD, personal communication, 2009.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

TABLE 4-1 Total Flow Volume of Freshwater Inputs and Outflows from Four of the Regions Shown in Figures 4-1, 4-2, and 4-5

 

Pre-drainage (KAF)

Precip./ET

Surface water

Groundwater

Total

Lake Okeechobee

Inputs

1,671

1,641

0

3,312

Outflows

2,338

980

0

3,318

Everglades Agricultural Area

Inputs

2,635

942

0

3,577

Outflows

2,450

1,122

7

3,579

Water Conservation Areas

Inputs

3,475

1,467

6

4,948

Outflows

3,007

1,916

23

4,946

Everglades National Park

Inputs

2,776

1,752

8

4,536

Outflows

2,629

1,856

50

4,535

NOTE: The numbers represent total inflows and outflows calculated using the data provided in the figures, which were generated by the NSM v. 4.6.2 and the SFWMM v. 5.4. ET = evapotranspiration; KAF = thousand acre feet.

peats of the pre-drainage system isolated the surface water from the groundwater. These changes also have important implications for water chemistry, as will be discussed in Chapter 5. Everglades National Park has also experienced substantial changes in flows as a result of the engineered systems upstream. Under the pre-drainage conditions, the area that is now Everglades National Park received roughly 1.3 MAF of water per year (according to both the NSM and the NSRSM) as overland sheet flows from the land that is now WCA 3, with total inflow of 1.7-1.8 MAF from all sources (Figure 4-1). Under present conditions the same park area receives about 0.8 MAF in surface flows from WCA-3 through culverts beneath Tamiami Trail (Figure 4-2). On average 1.1 MAF flows into the park from all sources (or 61-64 percent of pre-drainage flows), and seepage to the east removes an additional 0.2 MAF of this total. As a result of these adjustments, the park area that once discharged approximately 1.9 MAF per year through coastal ecosystems to the Gulf of Mexico (NSM 4.6.2; or 2.1 MAF per year according to the NSRSM) now only discharges about 1.1 MAF per year (see Figures 4-1 and 4-2).

In addition to changes in the overall volume and distribution of water discussed above, the Everglades landscape has also experienced substantial changes in the timing, duration, velocities, and directions of flow. Although no stage data for South Florida exist prior to the construction of the Tamiami Trail and associated levees, hydroperiods historically were thought to be tied to seasonal variation in regional rainfall and secondarily to the slow drainage into and from the region (Duever et al., 1994). Florida has a five-month “rainy season” (mid-May to mid-

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

Current (KAF)

CERP flows (KAF)

Precip./ET

Surface water

Groundwater

Total

Precip./ET

Surface water

Groundwater

Total

1,667

1,660

0

3,327

1,667

1,820

0

3,487

2,140

1,211

0

3,351

2,130

1,374

0

3,504

2,635

497

34

3,166

2,635

614

26

3,275

1,917

1,243

3

3,163

2,025

1,244

3

3,272

3,475

1,915

0

5,390

3,475

1,899

0

5,374

3,333

1,163

891

5,387

3,301

1,485

592

5,378

2,776

1,087

87

3,950

2,776

1,898

5

4,679

2,469

1,124

355

3,948

2,572

1,597

503

4,672

October) that is typically accompanied by increasing water levels, and a less rainy or “dry season” (November to April) that is typically associated with stable or falling levels (Obeysekera et al., 1999). The reproductive success and survival of Everglades flora and fauna are linked to these seasonal cycles. For example, many wetland species such as apple snails, alligators, wading birds, snail kites, and Cape Sable seaside sparrows time breeding to coincide with the dry season, expecting water levels to recede slowly. Yet the area still receives significant rainfall in the dry season associated mainly with frontal passages, and that rain can lead to rising rather than falling water levels (i.e., “reversals”), which can result in reduced reproductive success for many wetland birds (discussed in more detail later in the chapter). Reversals during spring likely occurred in the pre-drainage Everglades, but two factors probably have increased their frequency and magnitude recently. The first is the reduced water-storage and hydrologic buffering capacity associated with the reduced spatial extent of the Everglades. The second is current water management, which can contribute to increased annual changes in water levels, as has occurred on Lake Okeechobee (Beissinger, 1986; NRC, 2007). While the Everglades has been described by some as a “hyperseasonal savanna” (Kushlan, 1987; Duever et al., 1994), its inter-annual (between-year) rainfall variation actually is much smaller than that of other lowland neotropical wetlands with similar flora and flora (Beissinger and Gibbs, 1993), such as the Llanos in Venezuela and the Pantanal in Brazil (Kushlan et al., 1985). Thus management activities that increase intra-annual (within-year) variation in water levels will likely adversely affect the Everglades.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

BOX 4-1

Modeling the Hydrology of the Historic South Florida Ecosystem

An understanding of the water flows of the pre-drainage system is essential for restoration project planning. Comprehensive Everglades Restoration Plan (CERP) agencies presently use two models to estimate pre-drainage water flows: the Natural System Model (NSM) and the Natural System Regional Simulation Model (NSRSM). These models use similar platforms as hydrologic models of current conditions but without the water control infrastructure and with different land cover and land use. The NSM uses the same climatic input, model parameters, grid spacing (2 mile by 2 mile) and computational methods as the South Florida Water Management Model (SFWMM), but physical features, such as topography, vegetation type, and river locations are adjusted to represent the pre-drainage condition. As more paleoecology data became available that provided important insights into historic hydrologic conditions (e.g., Willard et al., 2001; Winkler et al., 2001; Saunders et al., 2006; Bernhardt and Willard, 2009), the NSM progressed through a series of revisions. Version 4.6.2 is the latest version of the model in use, although Everglades National Park has worked on its own revisions to the model code (called ENP Mod 1) based on paleoecology data that were not well simulated in prior versions of the NSM. ENP Mod1 simulates a much wetter system that that of NSM 4.6.2.

The NSRSM is an entirely new fully coupled surface-groundwater model with a system of triangular cells ranging in size from 0.1 to 2 miles on a side. Compared with earlier modeling efforts for the pre-drainage system, the NSRSM covers a larger proportion of the entire watershed (and some areas outside the watershed), and it uses improved data sets, particularly for land cover and land use and topography. The South Florida Water Management District (SFWMD) is currently developing the South Florida Regional Simulation Model (RSM) designed to extend the NSRSM to describe present conditions. Generally, NSRSM model runs describe a natural system that is wetter than the system described by NSM 4.6.2 model runs.

These three model-generated descriptions of the pre-drainage system are each different, and there is uncertainty inherent in such hind-casts of hydrologic conditions of a century ago. Despite these reservations, the committee sees some convergence among the recent pre-drainage model output (NSRSM, ENP mod1) suggesting a wetter pre-drainage system than prior NSM output, with total inputs from the north to the current Everglades Protection Area averaging 1.9-2.1 million acre-feet (MAF)/year. This amount can be contrasted against current flows of approximately 1.4 MAF/year across the same boundaries (Wilcox and McVoy, 2009).

The inter-annual variation of flood and drought events is another important feature of the pre-drainage Everglades. Floods and droughts are recurring pulse events in many wetlands (Odum et al., 1995; Dong, 2006) including the Everglades (Thomas, 1974). The life histories of many plants and animals have evolved and been shaped in the Everglades by these hydrologic events (Davis and Ogden, 1994), which may have occurred on long-term rainfall cycles of 4-7 years in south Florida (Thomas, 1974; Beissinger, 1986; Duever et al., 1994),

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

as well as associated cycles in the timing and extent of wildfires (Beckage and Platt, 2003; Lockwood et al., 2003). Over the past century, the transformation of the Everglades landscape through compartmentalization and canals has partly decoupled the occurrence of droughts and floods from rainfall variability, sometimes shortening or lengthening the intervals between drought and flood events or changing their duration. Restoration of natural hydrologic variation is needed to maintain ecological communities in the Everglades. For example, the reduction of droughts that cause dry-down events can cause a loss of tree islands (Willard et al., 2006), while too-frequent droughts can cause snail kite populations to decline (Beissinger, 1995; Martin et al., 2008) or reduce fish populations so that they can no longer adequately support large predators such as alligators (Mazotti et al., 2009).

Finally, the magnitude and directions of flow have significantly changed as a result of engineering works as shown in Figure 4-3. Among the most important engineering changes was the creation of the WCAs, which interrupted and redirected the sheet flow that formed and maintained the distinctive features and ecological functions of the Everglades.

The effects of the water management structures on water depths are illustrated in Figure 4-4, in which water depths during the midst of the rainy season are compared to those near the end of the dry season. Figure 4-4 captures a wet year (2006) and shows the extensive ponding that occurs in WCA-3A behind the L-67 levees, which prevent flow from moving southeast into WCA-3B, and above the Tamiami Trail (and its associated levee), which limits the flow of water into Everglades National Park. Similar effects can be seen in the southern ends of WCA-1, WCA-2A, and WCA-2B. Figure 4-4b shows the extent of extreme dry conditions that now occur during drought years, particularly in northwestern portions of the WCAs and Shark River Slough in Everglades National Park, and the persistent ponding in the extreme southern portions of the WCAs and behind the L-67 levees in WCA-3A.

PARTIAL HYDROLOGIC RESTORATION AND SPATIAL TRADEOFFS

Reduced spatial extent, extensive peat loss, and large urban and agricultural demands for water and flood control make it infeasible to fully restore the hydrology of the remnant Everglades ecosystem. Thus constrained, CERP and related projects have aimed at partial restoration toward pre-drainage depths, hydro-periods, and flow regimes. Some of the major features of hydrologic restoration under the CERP are summarized in Figure 4-5. By comparing Figure 4-5 to Figure 4-2, one can see that a fully implemented CERP is expected to lead to large reductions in flood discharges to the northern estuaries, moderate reductions in flood discharges to the WCAs, and significant increases in freshwater inputs to

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-3 Simulated mean annual overland flow based on climate data for the period 1965-2000, comparing the system under pre-drainage conditions as modeled by the NSRSM v. 3.3 (left; Said and Brown, 2010) and the present managed system using the Glades-Lower East Coast Service Area (LECSA) model (right; Senarath et al., 2008, 2010; see also Lal et al., 2005; SFWMD, 2006b).The color of the arrows is scaled to reflect the magnitude of flow.

FIGURE 4-3 Simulated mean annual overland flow based on climate data for the period 1965-2000, comparing the system under pre-drainage conditions as modeled by the NSRSM v. 3.3 (left; Said and Brown, 2010) and the present managed system using the Glades-Lower East Coast Service Area (LECSA) model (right; Senarath et al., 2008, 2010; see also Lal et al., 2005; SFWMD, 2006b).The color of the arrows is scaled to reflect the magnitude of flow.

SOURCE: L. Gerry, SFWMD, personal communication, 2010.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-4 Example of hydrologic extremes now characteristic of WCA-3 and Shark River Slough: (a) wet conditions observed on September 30, 2006 and (b) extreme dry conditions observed on April 20, 2008.

FIGURE 4-4 Example of hydrologic extremes now characteristic of WCA-3 and Shark River Slough: (a) wet conditions observed on September 30, 2006 and (b) extreme dry conditions observed on April 20, 2008.

SOURCE: Johnson (2009) generated using the USGS Everglades Depth Estimation Network (EDEN).

Everglades National Park (see Table 4-1). These and other changes depend on new surface storage, aquifer storage and recovery, wastewater reuse, and other CERP elements described in Chapter 2.

One of the consequences of reduced spatial extent and reduced storage in the modern system is that it may be impossible to get the water “right” or even “better” everywhere at all times. CERP planners have always recognized that restoration benefits would be unequally distributed across the Everglades landscape and that hydrologic conditions might even worsen in some areas in order to achieve desired outcomes in others (USACE and SFWMD, 1999). It is important to understand these tradeoffs and interdependencies when evaluating the design and staging of CERP projects, especially given the kinds of lengthy delays and design changes that have characterized restoration efforts to date. The extent to which one area is impacted to achieve benefits elsewhere depends on the amount of new storage and changing constraints on water distribution such as flood control, seepage management, and water quality.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-5 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin under full CERP implementation, calculated using a 36-year simulation using the SFWMM v. 5.4.3. Model run CERP A shown simulates the CERP preferred alternative (D13R). The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

FIGURE 4-5 Estimated annual water budget for the Kissimmee-Okeechobee-Everglades drainage basin under full CERP implementation, calculated using a 36-year simulation using the SFWMM v. 5.4.3. Model run CERP A shown simulates the CERP preferred alternative (D13R). The numbers in rectangles represent mean annual flow volumes in 1,000 acre-feet/year. Change in storage, shown in circles, represents the net inflows minus outflows over the period of record.

SOURCE: J. Obeysekera, SFWMD, personal communication, 2009.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

Expected Subregional Differences in CERP Ecological Performance

In this section the committee summarizes how restoration benefits—assessed using hydrologic performance measures—are expected to vary across the Everglades system from Lake Okeechobee southward under full CERP implementation and in the near term with the completion of the initial (Band 11) projects. It draws heavily from systemwide hydrologic analyses conducted by RECOVER scientists for the Initial CERP Update (RECOVER, 2005c) and Technical Report on Systemwide Performance of CERP 2015 Band 1 Projects (RECOVER, 2010c).

CERP scientists have produced an extensive set of performance measures to set restoration targets and to evaluate alternative plans and implementation progress (RECOVER, 2007b). Specific measures and targets have been identified for more than 40 indicator regions corresponding to small clusters of 2-mile by 2-mile grid cells in the SFWMM and NSM. The performance measures capture aspects of the hydrologic regime such as frequency and magnitude of high and low water stages or frequency and duration of inundation. The restoration target for a performance measure in any particular indicator region is typically based on the value obtained using the NSM, but in some cases additional research findings are used to develop relationships between hydrologic observations and ecological factors.

To examine some of the inherent challenges of getting the water right in all places at all times, the committee assembled values for selected performance measures and indicator regions under pre-drainage, current, and 2050 conditions, with and without the CERP (see Table 4-2; RECOVER, 2005c). The table also summarizes model-estimated discharges between selected regions. Performance measures are arranged in rows from north to south starting with Lake Okeechobee and the northern estuaries and ending with Florida Bay. The table also includes modeled ecological performance in 2015 assuming construction of the 1-mile bridge on the Tamiami Trail, new L-29 Canal stage constraints (8.5 feet above sea level), and completion of the following CERP Band-1 projects (see Chapter 3 for the current status of these projects) including:

  • Indian River Lagoon C-44 Reservoir

  • Broward County Water Preserve Areas (C9 and C11 impoundments)

  • WCA-3A and 3B seepage management

  • Acme Basin B Discharge

  • Site 1 impoundment

1

According to the Master Implementation Sequencing Plan (USACE and SFWMD, 2005a), Band 1 projects represent those that would be completed between 2005 and 2010. However, given the delays in project implementation, the RECOVER (2010b) analysis assumed that these projects could be completed by 2015.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
  • C-111 Spreader Canal Phase 1 (Frog Pond/Leaky Reservoir)

  • North Palm Beach County

  • C-51 and L-8 Basin Reservoir Phase 1

  • Everglades Agricultural Area (EAA) Storage Reservoir Phase 1

  • Lake Okeechobee Watershed Plan

  • Rain-driven operations in Rotenberger Wildlife Management Area

  • C-43 Basin Storage Reservoir Phase I

TABLE 4-2 Selected Features of the Everglades Water Budget and Regional Performance Indicators

NOTE: The data in this table are based on the NSM v.4.6.2 of pre-drainage hydrology and the SFWMM v. 5.4.3 for existing conditions, 2015 without Band 1 CERP projects, 2015 with Band 1 CERP projects, 2050 without CERP but with Rain Driven Operations, and 2050 with CERP. The model results are based on climate and rainfall data for the period 1965-2000.The performance measure scores are derived from the Interim CERP Update (RECOVER, 2005c) and Technical Report on Systemwide Performance of CERP 2015 Band 1 Projects (RECOVER, 2010c). Green cell shading indicates conditions at or near restoration targets (left-most column), yellow indicates conditions approaching the targets but still potentially damaging, and red indicates conditions departing from targets and ecologically undesirable according to RECOVER scientists. Cell colors were chosen by the committee based on interpretations of the performance by RECOVER scientists (RECOVER,2005c, 2010c).

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
Northern Estuaries and Lake Okeechobee

Some of the disparities in expected CERP restoration outcomes for different subregions are illustrated in Table 4-2. Under the CERP, new storage would greatly reduce the frequency of unwanted very low or high discharges to the northern estuaries (see #1 and 9-14 in Table 4-2). Many of these benefits could be realized in the near term with completion of Band-1 storage projects such as the C-43, C-44, and EAA reservoirs (Table 4-2). On the other hand, little change is anticipated for Lake Okeechobee, with a small reduction in the frequency of extreme high or low water stages (#7-8, Table 4-2) (RECOVER, 2005c). In the Band 1 scenario, which was based on a different lake regulation schedule than is currently in use, unwanted high lake stages could increase in order to achieve other systemwide benefits such as reduced flood discharges to the estuaries and increased dry-season releases to Everglades National Park while avoiding additional cutbacks in water supply to the Lake Okeechobee service area (RECOVER, 2010c). These high lake stages are less likely under the current regulation schedule for the lake (J. Vearil, USACE, personal communication, 2010).

Arthur R. Marshall Loxahatchee National Wildlife Refuge (LNWR) and WCA-2

Under the CERP, total inflow from the north into the WCAs should increase slightly (#3, Table 4-2), seasonal timing should come closer to pre-drainage conditions, and spatial distribution of inflows should improve compared to current canal deliveries. Hydrologic conditions improve slightly in the LNWR, but the frequency of damaging extreme high and low water events would increase in WCA-2A (#15-17, Table 4-2). At the same time, high water events should be less frequent and low water events more frequent in WCA-2B (#18-19, Table 4-2). In the near term, Band 1 projects are expected to slightly increase hydroperiods in WCA-2A, where they are already deemed excessive (#16, Table 4-2). Band 1 projects would reduce the risk of high water conditions in WCA-2B but create generally drier conditions that are not consistent with ridge and slough restoration (#19, Table 4-2; RECOVER, 2010c).

WCA-3

Modeled restoration outcomes in WCA-3A vary widely among subregions. In northeastern WCA-3A, the CERP should slightly reduce the frequency of high water extremes but increase the frequency of low water extremes relative to the future without the CERP (#20-21, Table 4-2). Band 1 projects have complex effects related to management of stormwater treatment area discharges (STA 3/4), but they will likely increase drought impacts in northern WCA-3A as rain-driven

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

operations increase flows to Everglades National Park and southern coastal systems (RECOVER, 2010c). In central WCA-3A, the CERP increases the duration of flooding compared to the future without the CERP, creating hydropatterns that would likely adversely affect the best remaining ridge and slough landscape (#22, Table 4-2; RECOVER, 2005c). On the other hand, the CERP significantly reduces the duration of flooding and extreme high water conditions in southern WCA-3A (#23-24, Table 4-2), improving conditions for tree islands there. Band 1 projects alone should appreciably mitigate flooding problems in southernmost WCA-3A.

Restoration outcomes in WCA-3B are especially uncertain. Without the CERP, the area is likely to continue moving farther from pre-drainage ecological conditions. Re-inundating the area could create excessive high water conditions (#25-26, Table 4-2). Peat elevations have subsided by 1–3 feet since compartmentalization, and re-flooding of WCA-3B would not only require extensive seepage management but also would likely lead to the loss of peat-based tree islands that have subsided 2–3 feet since the area was compartmentalized (RECOVER, 2010c). Band 1 projects, which begin to reconnect WCA-3A, WCA-3B, and Everglades National Park, introduce increased risk of extreme high water events in WCA-3B, leading RECOVER scientists to recommend careful adaptive management of the transition to a wetter hydrologic regime in that area (RECOVER, 2010c).

Everglades National Park

The CERP provides a roughly 75 percent increase in surface flow into Everglades National Park, with much of this additional water to arrive via an eastern flow-way supplied by new belowground reservoirs called the Lake Belt (Figure 4-5; Table 4-1). Increased freshwater discharges produce large improvements in key performance indicators south of the Tamiami Trail. For example, the inundation periods for northeast and south-central Shark River Slough and the frequency of dry-down events are expected to approach NSM-based targets (#27-30, Table 4-2). Only modest benefits are obtained from Band 1 projects because more substantial ecological benefits depend on water provided by future CERP projects (RECOVER, 2010c).

Southern Estuaries

Freshwater inflows to Florida Bay would increase under the CERP and would lower the currently high salinities in coastal embayments. Based on historical empirical relationships CERP flows are not sufficient to achieve restoration targets in western embayments (e.g., Garfield Bight), but they bring salinity

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

levels down appreciably in eastern Florida Bay (#31, 32 in Table 4-2). Modeled restoration benefits for Biscayne Bay (not shown here) are slight: In fact, future-without-project hydrologic outcomes are closer to targets than CERP outcomes for northern and central Biscayne Bay (RECOVER, 2005c).

Summary

To summarize, model results for full CERP implementation (based on the 1965-2000 period of record) indicate that the benefits of hydrologic restoration of the South Florida ecosystem will accrue mostly to the northern estuaries, southern WCA-3A, Everglades National Park, and eastern Florida Bay, areas where hydroecological conditions are currently far from desired conditions (Table 4-2). However, the CERP could exacerbate excessive wet or dry conditions in some regions of the WCAs, including areas such as central WCA-3A, which is considered a relatively intact remnant of the ridge and slough landscape. New modeling using the NSRSM shows a wetter pre-drainage system compared to the NSM, perhaps reducing concern about areas made wetter by restoration but moving relatively dry areas even further from desired conditions. Ecological outcomes in WCA-3B are especially uncertain because of peat subsidence and the risk of drowning much-lowered tree islands, which argues for deliberate, incremental, adaptive restoration of this area in particular.

Balancing Competing Objectives and Tradeoffs in Everglades Restoration

Despite the many sources of uncertainty in estimates of the CERP’s systemwide hydrologic budgets,2 systemwide modeling contributes importantly to understanding dynamic relationships between subareas, how those relationships have changed over time, and how they could be affected by different restoration project designs. Systemwide hydrologic modeling helps to identify the tradeoffs that have been made and, by necessity, continue to be made in Everglades restoration. It is important that the tradeoffs resulting from CERP restoration be clearly recognized and analyzed as rigorously as possible from a whole-system perspective during project planning. Because stakeholder concerns often focus on specific subregions, it is also important that the analyses of tradeoffs are transparent and that the results and uncertainties are communicated clearly to the public, even at the risk of fueling political conflicts between different interest groups.

2

Sources of model uncertainty include coarse model resolution, inaccurate topography, uncertain parameters for estimating overland flow, infiltration and evapotranspiration, poorly understood surface-groundwater exchanges, and speculative water supply demand forecasts.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

Disparities occur among models, for example, the NSM versus the NSRSM, or among different versions of the SFWMM and the RSM under development. These disparities highlight the clear need to continue refining and updating regional hydrologic models as the CERP moves forward so that the tradeoffs can be more confidently evaluated and addressed through project design and system operation.

CERP planning has made appropriate use of performance measures that link hydrologic conditions to ecological restoration goals for specific areas; however, there is still no formal analytical approach to measuring the relative systemwide benefits of alternative restoration plans or components that integrates across the kinds of tradeoffs described in this section. There is no explicit basis for gauging the degree to which a plan alternative or a set of projects satisfies multiple ecological restoration goals as well as flood control and water supply objectives. The need for such a planning framework was identified several years ago by a previous National Research Council (NRC) committee (NRC, 2005) and has also been recognized by RECOVER scientists (RECOVER, 2010c). A review of the many approaches for multi-objective water management planning is beyond the scope of this chapter. Loucks (2006) offers one pragmatic approach to evaluating systemwide performance in the Everglades that takes advantage of existing performance measures.

Short-Term Benefits and Risks of Partial Restoration

The RECOVER (2010c) analysis of systemwide performance of Band 1 projects offers a likely scenario of Everglades restoration outcomes over the next decade (assuming that the EAA Reservoir is brought online during that time). The distribution of restoration benefits is similar to that under full CERP implementation: the greatest measurable benefits are to the northern estuaries, southern WCA-3A, and Everglades National Park, and increased risks are placed on Lake Okeechobee and portions of the WCAs, notably southern WCA-2, northern WCA-3A, and WCA-3B.

Improved conveyance and better distribution of water in southern WCA-3A and Everglades National Park will be at the expense of shorter hydroperiods and increased risk of severe dry-down events and wildfires in northern WCA-2A and northern WCA-3A until storage is increased and water quality concerns are mitigated so that more water can be moved south from Lake Okeechobee and the EAA. It is important to recognize that it will be many years before the storage (and, by necessity, the associated water quality treatment and/or source control; see Chapter 5) needed to address these issues in WCA-2A and northern WCA-3A is functional. Band 1 projects contribute only 9 percent of the 5.2 million acre-feet/year of storage originally envisioned for the CERP and largely affect the

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

northern estuaries, not the Everglades Protection Area (RECOVER, 2010c). Furthermore, the currently stalled EAA Reservoir (170,000 acre-feet/year) is the only reservoir among the Band 1 projects that could impact the remnant Everglades ecosystem, and the benefits of this project to the area south of Lake Okeechobee were not clear as of the latest draft project implementation report (USACE and SFWMD, 2006; NRC, 2007). Even with the EAA Reservoir, downsized Band 1 storage projects will now provide only 73 percent of the capacity expected from those projects in the original CERP plan (RECOVER, 2010c). Because the planning and decision making for the River of Grass initiative has been suspended to address pressing water quality issues and because state funding to support major additional land acquisitions is uncertain, it remains unclear what new storage and treatment could be available through that effort (see also Chapter 3). Thus for at least the next decade, it appears that managing ecological risks across the system comes down to adaptive management of existing water.

Any consideration of ecological risks from water management should also consider the timescale over which adverse ecological outcomes might be reversible, if they are at all. For instance, peat accumulates at a rate of only 2–3 mm/year (<1 foot per century) in unenriched Everglades wetlands (Craft and Richardson, 1993), so deep peat loss is effectively irreversible. Changes in hydrology or fire regime can cause rapid changes in plant communities but some communities such as tree islands may require relatively long time periods for recovery (White, 1994). Because some areas might, by necessity, need to be exposed to adverse hydrologic conditions during the transition to the full CERP implementation, the ability to restore these areas once additional projects come online would need to be considered in any assessment of tradeoffs.

CASE STUDY: RESTORING WATER FLOWS IN WCA-3

The challenges of balancing competing objectives and the tradeoffs inherent in restoration are well exemplified in WCA-3. WCA-3 is central to the Everglades restoration, because it contains extensive and relatively intact Everglades landscapes, such as tree islands and ridge and slough, and it provides critical habitat for endangered species such as the snail kite and wood stork as well as nonthreatened wading birds. The area is also valued for its recreational fishing and hunting. The Miccosukee Tribe has a perpetual lease to more than 189,000 acres of the western portion of WCA-3A and relies upon Everglades lands to support its culture, religion, and economic survival. Moreover, the management of water through WCA-3 plays a key role in restoring the condition of Everglades National Park immediately downstream. Inherent constraints (e.g., peat subsidence, availability of high quality water [see also Chapter 5], barriers to flow such as the Tamiami Trail) create challenges for simultaneously improving all aspects

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

through restoration. In this section, the committee discusses these challenges in more detail through an examination of issues related to the management of water in WCA-3 and identifies specific science and management needs to guide restoration decision making as the CERP moves forward.

Brief History of the Challenge of Managing Water for Multiple Uses in WCA-3

The WCAs were authorized based on three sometimes conflicting water management goals (USACE, 1996; Light, 2006). First, the WCAs were intended to address flood control issues by capturing excess agricultural runoff and providing barriers between the Everglades and developed areas to the east. Second, they were to provide urban and agricultural water supply needs through aboveground storage and groundwater recharge. Finally, the WCAs were to provide benefits for the environment, both within the conservation areas themselves and by discharging excess water to Everglades National Park. WCA-3 is by far the largest of the conservation areas (915 square miles or 68 percent of the total area) and includes the main historical pathway for surface-water flow from Lake Okeechobee through South Florida. In 1962, WCA-3 was subdivided by the L-67 levees into WCA-3A (491,049 acres) and WCA-3B (94,511 acres) to reduce seepage (see Figure 1-3). WCA-3A is the largest area of contemporary sheet flow. Additional information on WCA-3 and its management is provided in Box 4-2.

Challenges in managing water for multiple uses in WCA-3 became apparent soon after it was created (Blake, 1980). Between 1966 and 1970, large numbers of white-tailed deer (Odocoileus virginianus), which had moved into portions of the WCA-3 that were abnormally dry due to drought and previous water management policies, died when water levels rapidly increased after heavy rains. Similar deer mortality events have recurred periodically thereafter (e.g., 1982-1983, 1994-1995) under similar conditions (see MacDonald-Beyers and Labisky, 2005). In the mid-1960s, drought and fires ravaged Everglades National Park in part because water was being held in WCA-3 for water supply, and this eventually resulted in a Minimum Delivery Schedule volume of 315,000 acrefeet/year to be allocated to the park according to a monthly schedule (Carter, 1975; Blake, 1980).

From the mid-1980s to present, conflicts have centered on the benefits that can be achieved by changing flows to Everglades National Park for restoration of ecosystems and endangered species versus the negative impacts upstream in WCA-3 to ecosystem processes, endangered species, recreational interests, and tribal concerns. Conflicts in the early to mid-1980s centered around the benefits of increasing flows to Shark River Slough and Florida Bay to restore ecosystem processes and recover wading bird populations (including the endangered wood stork), and the resulting negative effects of lower water levels in WCA-3A on the

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

endangered snail kites and higher water levels in WCA-3B on white-tailed deer. The Experimental Water Deliveries Program (see summary in Chapter 2 of NRC, 2007), the Modified Water Deliveries to Everglades National Park (Mod Waters) project, and the CERP emerged from this conflict. In the late 1990s, concerns that too much water from WCA-3A was flowing into the western portion of Everglades National Park during the nesting season of the endangered Cape Sable seaside sparrow (January-April) and flooding nests resulted in the Interim Structural and Operational Plan (ISOP) in 2000, followed by the 2002 Interim Operation Plan (IOP) that is currently in use (see Box 4-2 and the next section).

Recent Water Management in WCA-3

Inflow and outflow of water in WCA-3 are regulated under the IOP by the water level targets and conditions in both WCA-3 and Everglades National Park (see also Box 4-2). The regulation schedule (Appendix D) is designed to mimic the historical changes in water levels thought to accompany seasonal changes in precipitation, as discussed previously in this chapter. Levels rise during the rainy summer months to peaks between September and November, and levels fall during the drier months beginning in January or February, reaching a low from May through July. A major change in management under the current operations (IOP) has been to close or greatly reduce the flow of water out of the western S-12 gates at the southern end of WCA-3A into Everglades National Park for most of the winter and spring to accommodate the nesting season of the Cape Sable seaside sparrow. Gate S-12A is closed on November 1, S-12B is closed on January 1, and S-12C is closed on February 1. These S-12 closures were accompanied by a change in the IOP regulatory zones (addition of Zone E1, see regulation schedule in Appendix D) that allows for maximum WCA-3A outflows at lower stages, and through increased WCA-3A outflows to the South Dade Conveyance System. In spite of these changes designed to move more water out of WCA-3A, the reduced flow out of the S-12 gates has been accompanied by higher water levels, longer hydroperiods, and greater fluctuations in water levels in WCA-3A.

These effects of water management can be seen in the hydrographs of long-term water stages in WCA-3A (Figure 4-7). Since completion of the C&SF project, WCA-3 has experienced four water management regimes: early operations (~1950–1969), minimum water delivery (1969-1984), Experimental Water Deliveries (1984-1999), and ISOP/IOP (1999-present). Water levels in WCA-3A began increasing in the mid-1990s with rainier conditions and have remained notably higher during the past decade under IOP, despite several regional droughts that have occurred. During IOP, the average daily water level has been significantly higher in all three regions of WCA-3 than in any other water management regime (Figure 4-8). In addition, the annual maximum and mini-

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

BOX 4-2

Water Management in WCA-3

Management of water levels within Water Conservation Area (WCA)-3A and WCA-3B is the responsibility of the South Florida Water Management District (SFWMD) in accordance with regulation schedules set by the U.S. Army Corps of Engineers (USACE). Wildlife management is delegated to the Florida Fish and Wildlife Conservation Commission under lease from the SFWMD. The Jacksonville District of the USACE operates and maintains the main outlets of the WCAs.

Currently more than half of the 1.8 million acre-feet (MAF) annually discharged into WCA-3A comes from WCA-2 via the S-11 structures (Figure 4-6). Water is discharged into northern WCA-3A mainly from stormwater treatment areas (STAs)-3 and -4 through S-8 and S-150 control structures and from the east via S-9 and S-9A. The timing and rate of inflows to WCA-3A are governed by flood control releases when stages in Lake Okeechobee or WCA-2 exceed seasonally varying thresholds. Inflows are also limited by the capacities of STAs receiving water from Lake Okeechobee.

WCA-3 is bordered to the south by the Tamiami Trail. The inability of the Tamiami Trail to pass large volumes of water without compromising the integrity of the road base led to a long history of water management problems both north and south of the trail (see also NRC, 2008). About half of the outflow from WCA-3A currently discharges into Everglades National Park (ENP) via the S-12 structures through culverts under western portions of Tamiami Trail. Much of the remaining outflow is conveyed south via the L-67 extension and L-31 canals or west into Big Cypress National Preserve through the S-343 structures. Scheduling of the amount and timing of water deliveries to ENP has been especially contentious as water managers have sought to reduce ecological impacts while meeting demands for flood control and water supply.

The current regulation schedule for WCA-3A along with actual water levels at selected stations in 2008 and 2009 are shown in Appendix D. Discharges from WCA-3A to ENP are governed in part by the Interim Operation Plan (IOP) that requires seasonal closings of the release gates on structures S-12A (November 1-July 15), S-12B (January 1–July 15) and S-12C (February 1-July 15) to prevent excessive flooding of nesting habitats for Cape Sable seaside sparrows. At lower water levels releases are determined by the amount of rainfall in WCA-3A using a simple linear regression model relating flow outflow to rainfall and evaporation. Ultimately, the IOP will be superseded by the Combined Structural and Operational Plan (CSOP), which would govern the operations of WCA-3 with all Mod Waters and C-111 South Dade project features in place.

mum water levels have tended to increase in the central and southern regions of WCA-3A, although the mean was not significantly different from the decade of Experimental Water Deliveries.

Hydrographs from the northern (GA-63), middle (GA-64), and southern (GA-65) regions of WCA-3A also illustrate the influence of water management regimes on stages by region (Figure 4-7). Although the northern end of WCA-3A

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-6 Water management structures in WCA-3. Gage locations also shown for data presented in Figure 4-7. © International Mapping Associates.

FIGURE 4-6 Water management structures in WCA-3. Gage locations also shown for data presented in Figure 4-7. © International Mapping Associates.

dries out every year, water levels in the southern end have not reached average ground level since the mid-1990s. Over the past 50 years, average daily water levels (Figure 4-8) have increased the most in the southern region (GA-65), followed by the central region (GA-64). Likewise, the southern end of WCA-3A experienced the largest increases in annual minimum and maximum water

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-7 Water levels at three gauges in WCA-3A: GA-63 at the northern end, GA-64Rainfall (inches)Year in the central region, and GA-65 at the southern end. Gage locations shown in Figure 4-6. Major water management regimes are indicated at the top of each hydrograph and average ground elevation by the dark horizontal line. The bottom graph shows annual average rainfall totals across a network of over 50 gages in the NOAA Everglades and southwest coast region, covering the area from Lake Okeechobee southward. Data from the SFWMD and NOAA.

FIGURE 4-7 Water levels at three gauges in WCA-3A: GA-63 at the northern end, GA-64Rainfall (inches)Year in the central region, and GA-65 at the southern end. Gage locations shown in Figure 4-6. Major water management regimes are indicated at the top of each hydrograph and average ground elevation by the dark horizontal line. The bottom graph shows annual average rainfall totals across a network of over 50 gages in the NOAA Everglades and southwest coast region, covering the area from Lake Okeechobee southward. Data from the SFWMD and NOAA.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-8 Daily annual average and average annual minimum and maximum water levels for gauges GA-63 (northern), GA-64 (central), and GA-65 (southern) in WCA-3A (shown in Figure 4-7) for major water management regimes.

FIGURE 4-8 Daily annual average and average annual minimum and maximum water levels for gauges GA-63 (northern), GA-64 (central), and GA-65 (southern) in WCA-3A (shown in Figure 4-7) for major water management regimes.

NOTE: Average-ground elevation is indicated by the dark horizontal line. In the box plots for daily average stage, the central vertical line indicates the median, the length of the box indicates the range for 50 percent of the observations, the whiskers account for the 95 percent confidence intervals, and * are outlying values. Within each plot, boxes with different letters are significantly different (P < 0.05) based on a one-way ANOVA and Tukey’s means separation test.

SOURCE: Data from the SFWMD.

levels, while the central region had moderate increases and the northern end experienced the least change.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

Recent and Long-Term Ecological Decline in WCA-3A

WCA-3A encompasses the most extensive, relatively intact ridge and slough landscapes remaining in the Everglades ecosystem, including tree islands, and provides critical habitat for endangered species such as the snail kite and wood stork. Profound ecological changes in WCA-3A have accompanied the compartmentalization and water management policies summarized above, especially in northwestern and southeastern subregions (Box 4-2, Figures 4-7 and 4-8). Some ecological consequences occurred rapidly, such as declines in snail kite numbers and nesting success, whereas others have taken place more or less sporadically over multiple decades, such as the declines in tree island size and number, the condition of ridge and slough topography and associated flow paths, and peat loss. As a result, WCA-3A has become a focus of growing public controversy and management concern.

Rapid Decline of the Endangered Snail Kite During the Past Decade

The snail kite is currently the most endangered vertebrate in Florida after the panther (Puma concolor). As described in Chapter 2, the population of snail kites has plummeted from more than 3,500 birds to fewer than 650 over the past decade, and water levels in WCA-3A have been an important contributor to the kite’s decline in addition to regional droughts (see Figure 4-9; Cattau et al., 2008, 2009). WCA-3A has been the stronghold for kites in Florida since completion of its surrounding levees in the mid-1960s, which probably saved the kite from extinction in Florida. Large numbers of kites have nested in the southern half of WCA-3A since the mid-1970s, and nesting success has typically been higher in this wetland than in others throughout the state (Snyder et al., 1989; Cattau et al., 2008). In recent years, however, conditions in WCA-3A have resulted in poor reproduction, reduced juvenile survival, and largely reduced numbers of kites nesting there (see also Chapter 2; Cattau et al., 2009).

The current regulation schedule in WCA-3A has contributed to the snail kite’s precipitous decline in several ways. First, temporarily holding water behind the S-12 structures from November to April to accommodate the breeding season of the Cape Sable seaside sparrow in Everglades National Park has prolonged high water events in WCA-3A in some years, which can reduce the number of kites using this wetland and their nesting and foraging success (Darby et al., 2008; Martin et al., 2008; Zweig and Kitchens, 2008). Second, the high water levels in January to April that encourage kites to nest on the western side of WCA-3A, which is shallower and contains more woody vegetation, have often been coupled with abnormally fast recession rates when the S-12 structures are opened. This results in sudden dry conditions that decrease nesting success

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

(Figure 4-9b) by making nests more vulnerable to terrestrial predators; the dry conditions also decrease the survival of juveniles after fledging by reducing the availability of the snails that are their primary food source (Beissinger, 1986; Cattau et al., 2008). Third, the current regulation schedule has increased the

FIGURE 4-9 Relationship between water levels, nesting success, and juvenile survival of snail kites nesting in WCA-3A: (A) annual minimum water levels versus proportion of nests that successfully fledged at least one young (nesting success); (B) rate of water level recession (January 1 to annual minimum) versus nesting success; and (C) annual minimum water level versus survival rate of juveniles. The regression line is in black, the 95 percent confidence intervals are in red, and all values are represented by NGVD (National Geodetic Vertical Datum) values.

FIGURE 4-9 Relationship between water levels, nesting success, and juvenile survival of snail kites nesting in WCA-3A: (A) annual minimum water levels versus proportion of nests that successfully fledged at least one young (nesting success); (B) rate of water level recession (January 1 to annual minimum) versus nesting success; and (C) annual minimum water level versus survival rate of juveniles. The regression line is in black, the 95 percent confidence intervals are in red, and all values are represented by NGVD (National Geodetic Vertical Datum) values.

SOURCE: Cattau et al. (2008).

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

likelihood of localized drought in WCA 3A during dry years (Cattau et al., 2008), which has adversely affected kite populations because juvenile survival and nesting success are related to minimum annual water level (Figure 4-9b). Finally, the current water regulation schedule has the potential to shorten the number of months during which kites can breed (Mooij et al., 2002). Kite population growth is strongly positively related to the duration of the breeding season because long breeding seasons allow multiple nesting attempts that offset typically low probability that any one nesting attempt will be successful (Beissinger, 1986, 1995). In conclusion, snail kite reproduction in WCA-3A now suffers from a water regulation schedule that appears to exaggerate the seasonal changes in water levels and does not mimic the seasonal patterns expected in a wetland driven by a natural hydrologic cycle and seasonal flows.

Loss of Tree Islands

Altered hydrology has produced myriad vegetation changes in the South Florida ecosystem. Drought-prone areas of northern WCA-3 have experienced peat loss, increased wildfire frequency, loss of tree islands, shrub invasion into emergent wetlands, loss of aquatic plants, sawgrass expansion into former slough wetlands, altered periphyton communities, and increased establishment of invasive exotic species (NRC, 2008; RECOVER, 2008). Tree islands may be consumed by fire, but trees may also die from excessive drought when water levels are more than 1 foot below ground for more than 30 days (Sklar et al., 2009b). At the other extreme, in areas such as southern WCA-3A where there is extended ponding of deep water, tree islands area has been accompanied in recent years by a lack of seedling establishment caused by stress from prolonged inundation (McKelvin et al., 1998; see Figure 2-13). Growth and survival of even the most water-tolerant species are inhibited or reduced when water depths on islands exceed 1 foot for more than 120 days (Wu et al., 2002).

Tree islands cover less than 5 percent of the Everglades, but they number in the thousands, ranging in area from less than 10 m2 to more than 70 hectares (ha; 173 acres) (Sklar and van der Valk, 2002). The systematic loss of tree islands from the central Everglades is of special concern because of their long time to establish, their high species diversity, and the disproportionate role they play in nutrient cycling and in supporting wildlife populations (Sklar and van der Valk, 2002).

Within WCA-3, there was a 67 percent decrease in total tree island area and a 45 percent decrease in the number of islands between 1940 and 1995 (Patterson and Finck, 1999; Sklar et al., 2005). Some tree islands have become “ghost islands” of standing dead trees or have disappeared altogether. The largest

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

period of tree island loss occurred between 1950 and 1970, with slower rates of loss before and after. The most recent analysis shows that between 1995 and 2004 tree island area declined an additional 520 acres (6 percent), and the number of tree islands declined by 11 percent (Figure 4-10).

Ridge and Slough

Ridge and slough landscapes are characteristic of the Everglades. They are defined by long, regularly spaced ridges of sawgrass that extend across a marsh in a linear fashion and are separated by interconnected wet sloughs and scattered tree islands (SCT, 2003). Major changes in the conditions of ridge and slough patterns can occur surprisingly quickly—within a decade—in response to changes in water depths and flow if the surface retains its underlying microtopography (Armentano et al., 2006; Sklar et al., 2009b). For example, Armentano et al. (2006) showed that within Taylor Slough, vegetation transitions between ridge

FIGURE 4-10 Tree island trends between 1940 and 2004.

FIGURE 4-10 Tree island trends between 1940 and 2004.

SOURCE: F. Sklar, SFWMD, personal communication, 2010.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

and slough communities occurred within a few years of building and operating the S-332 pump. The causes of pattern changes (Figure 2-13) are uncertain, but analyses suggest that local factors rather than regional factors are responsible, particularly water depth, flow, elevation and vegetation patterns, and the transport of sediment (Chapter 6). It can, however, take decades to centuries for flows across peatlands to rebuild the ridge and slough configuration of the topography (Willard et al., 2001).

Long-Term Peat Loss

Between 1950 and 2000 the Everglades Protection Area lost roughly 28 percent of its peat soils by volume due to drying, oxidation, and burning (Figure 4-11). That loss has been especially pronounced in northern WCA-3A, WCA-3B, and northeast Shark River Slough. As a result, soils in northern WCA-3A are now shallower (average depth <2 feet), denser, and have lower organic matter content than any other region of the WCAs (EPA, 2007). Even if the water flows were restored to these areas, rebuilding this lost peat and associated soil biogeochemical and ecosystem properties would take centuries. These losses have important implications for the maintenance of landscape features and characteristic vegetation in these areas. The loss of peat thickness has several important effects on Everglades landscapes, including increased exchange of surface water and groundwater with chemical and hydrologic consequences; and, as mentioned above, the loss of peat represents the loss of the substrate required to build and maintain the ridge and slough landscape. It also results in loss of elevation and therefore increases flooding depths and durations.

Balancing Multiple Restoration Objectives for WCA-3

As is discussed previously in this chapter, managing water upstream of the Tamiami Trail in WCA-3 and downstream in Everglades National Park to promote the restoration of multiple species and multiple ecosystem restoration objectives in both areas has proven to be problematic over the past five decades. Excessive drying or flooding has resulted in peat loss from subsidence and wildfires, loss of tree islands and encroachment by shrubs into emergent wetland habitats, loss of characteristic ridge and slough topography, and declines in snail kites in WCA-3. Similar problems have occurred for these same ecological features and the Cape Sable seaside sparrow (see Chapter 2) in Everglades National Park. Restoration success for both units is inextricably bound because flows in Everglades National Park and WCA-3 are interdependent because of their adjacent geographic locations. In this section, the committee discusses ways to balance the multiple restoration objectives for both WCA-3 and Everglades National

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
FIGURE 4-11 Soil thickness at 867 locations measured between 1995 and 2005, contrasted against thickness from 1946 as shown in inset map.

FIGURE 4-11 Soil thickness at 867 locations measured between 1995 and 2005, contrasted against thickness from 1946 as shown in inset map.

SOURCE: Scheidt and Kalla (2007).

Park by examining long-term and near-term implementation issues in relation to CERP and non-CERP projects and by articulating conflicts among the hydrologic needs of species that could be evaluated and tradeoffs that could be analyzed (see also NRC [2005] for discussion of tradeoff analysis). The committee also considers the prospects for making management operations more responsive to real-time ecological conditions.

Several CERP and non-CERP projects aim to improve the hydrologic conditions in WCA-3, although benefits from the largest projects (i.e., Decomp, L-31N Seepage Management) are roughly a decade away. In Box 4-3 near-term

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

non-CERP and CERP projects affecting WCA-3 and Shark River Slough are summarized. As described in Chapter 3 and above, these near-term projects will shift more water flow to the east, allow increased conveyance from WCA-3A into northeast Shark River Slough (NE-SRS), and increase the capacity for fresh-water inflows to NE-SRS via the Tamiami Trail road raising and 1-mile bridge construction. These projects will thereby improve hydrologic conditions in NE-SRS and will partially mitigate flooding problems in southern WCA-3A and western Shark River Slough. In addition, Taylor Slough wetlands should experience improved hydrologic regimes, and damaging flood releases to Florida Bay should be reduced.

Discharging more water south of Tamiami Trail into NE-SRS could increase the frequency and intensity of drought, peat loss, and vegetation change in northern WCA-3A, if these near-term projects are not accompanied by increased inflows into WCA-3. Even assuming that the current Integrated Delivery Schedule can be maintained and that water quality issues can be addressed (see Chapter 5), it will be at least 10 and possibly 25 years before significant new water can be provided through WCA-3 or via an eastern flow-way. In the meantime, the Florida snail kite population appears to be at high risk of extinction (Martin et al., 2007), precipitating a management crisis before CERP restoration measures are in place. In the interim, it is important to find near-term ways to improve water

BOX 4-3

Near-Term CERP and Non-CERP Projects Affecting WCA-3 and Shark River Slough

Projects currently scheduled for completion by 2013 will

  • restore flow connections between Water Conservation Area (WCA)-3A and northeast Shark River Slough (NE-SRS) by bridging and raising the Tamiami Trail (Mod Waters 1-mile bridge, under construction);

  • degrade L-67 and L-67ext levees in WCA-3 and NE-SRS (Mod Waters, partially completed) to re-connect WCA-3A and -3B and improve surface-water distribution in NE-SRS;

  • install new conveyance and seepage control structures in L-29 and L-67 levees to manage flow connections between WCA-3A, WCA-3B, and NE-SRS (Mod Waters, partially completed);

  • provide flood control in the 8.5-square-mile area (Mod Waters, completed);

  • manage eastward seepage with the S-356 and S-357 pump stations (Mod Waters, completed but not operating); and

  • develop and implement an operating plan for moving water from WCA-3A to NE-SRS (Combined Structural Operational Plan).

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

management practices, where practicable, to maximize restoration benefits and minimize further long-lasting impacts to these areas. These near-term efforts should make use of quantitative tools to estimate the likely reproductive success, survival, population size, condition, or extent for critical ecosystem components (e.g., snail kites, cape sable seaside sparrows, tree islands, ridge and slough patterns) under current and near-term projections of hydrologic conditions and should use the results of such analyses to inform management decisions.

Near-Term Operational Improvements

Examples of management refinements that could benefit WCA-3 are the implementation of a new rainfall-driven flow formula for Zone E releases (see Appendix D) to Everglades National Park and more flexible scheduling of S-12 gate closures under the IOP. These alternatives, described in more detail below, are being considered as part of the Everglades Restoration Transition Plan (ERTP), a multi-agency effort3 to improve water management operations concurrent with the November 2010 expiration of the biological opinion that imposes the current IOP regulation schedule (see also Chapter 3).

Since 1985, Zone E water deliveries from WCA-3A to Shark River Slough have been managed to mimic pre-drainage flow timing and volume expected from rainfall based on a simple linear regression model. This “rainfall formula” operates once water levels in WCA-3A fall below flood control levels. The allocations are based on observed flow responses to rainfall and evaporation in WCA-3A during a 1941-1952 reference period. The formula is calculated weekly, and water is released through the S-12 structures to northwest Shark River Slough (NW-SRS) or via the S-333 gated spillway to the L-29 Canal and southward via culverts under the Tamiami Trail. Recently, hydrologists at the SFWMD have developed a non-linear neural network model that outperforms the existing regression model in forecasting stage response to rainfall in WCA-3A and allows managed flows that are much closer to pre-drainage hydrology (Neidrauer et al., 2007; Ali, 2009). Even using existing control structures and operating constraints, the new rainfall formula provides improved stage forecasts that allow more rain-driven flow to Everglades National Park, resulting in a 10 percent increase in total flow to Shark River Slough and a 34 percent increase to Northeast Shark River Slough compared to the existing formula, mostly in the dry season from November to January (Neidraurer, 2009).

These changes come with a slight increase in duration of low stages in

3

The main participants have been the SFWMD, U.S. Fish and Wildlife Service, the USACE, Everglades National Park, the Florida Fish and Wildlife Conservation Commission, and the Miccosukee Tribe.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

WCA-3A and an increase in loading of total phosphorus to Everglades National Park, once again pointing to the multiple tradeoffs associated with changes in water management. Analyses are not available to date, however, to determine whether the new rainfall formula will promote recovery of the most endangered species in WCA-3 and Everglades National Park (kites and sparrows) or how well it supports other Everglades wildlife and ecological functioning. Moreover, in the absence of historical stage or flow data for comparison, evaluation of the efficacy of the new rainfall formula is based on comparison with recent version of the Natural System Model, which has considerable uncertainty in performance as discussed earlier in this chapter. Nevertheless, the new approach to managing rain-driven flow may be a promising way to improve water management and to deliver restoration benefits quickly prior to full project construction. The new formula could yield even greater benefits with the completion of Band 1 projects (Neidrauer et al., 2007). Given the constraints, the proposed operational changes at minimum are not expected to perform any worse than the existing operations plan (IOP) (T. Hopkins, FWS, personal communication, 2010).

Within the ERTP effort, water managers and biologists are also reconsidering the management of the S-12 structures that discharge water from southern WCA-3A into NW-SRS. As discussed above, the opening and closing of those structures has been on a rigid calendar schedule to avoid flooding Cape Sable seaside sparrows during the nesting season, but this schedule has seriously impacted southern WCA-3A through excessive high water and rapid draw-down. The ERTP team is considering a more flexible approach to S-12 operations that responds to the actual nesting behavior of Cape Sable seaside sparrows in Everglades National Park in a given year while also addressing resource concerns in WCA-3, such as those related to snail kites and tree islands. This more nuanced water management, combined with the new rainfall formula, could provide better water distribution and depths, balancing the needs of multiple species and ecological objectives.

System operations is also being improved through continuation of biweekly phone consultations among scientists and managers. These operations consultations consider recent precipitation and water levels across the South Florida ecosystem as they relate to target species and ecosystems and provide for realtime adjustments to operations as needed to address flood control and water supply demands, while striving to maintain optimal water management for multiple species. The calls have become more formalized over time, and each participating agency4 now provides written recommendations for operations in advance of the call based on the specific needs of the target species or landscape

4

Typically including, but not limited to, the U.S. Fish and Wildlife Service, Everglades National Park, the USACE, the SFWMD, and the Florida Fish and Wildlife Conservation Commission.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

components. This information is then used by USACE and SFWMD operations managers in their water management decisions. The ERTP team has encouraged the USACE and SFWMD to document the water management decisions made, so that the results are available for analysis to learn about and improve upon system operations.

These regular multi-agency consultations are a first step toward multi-species adaptive management, which is essential to restoration progress. They represent a change in the way the agencies have interacted in the past and especially in the consultation process for the U.S. Fish and Wildlife Service (FWS). Under the ERTP, consultation has moved from a retroactive process that often evaluates the ecological effects of proposed water management on listed species to determine if a jeopardy decision would occur, to a more proactive process that attempts to recover species before further population declines accrue. The committee commends this incremental multi-agency approach to improve water management and ecological conditions in WCA-3 during the transition period before significant new storage and conveyance features are built. This represents a form of incremental adaptive restoration, as proposed by NRC (2007). However, it is important that the CERP agencies seize the associated opportunities for learning from these flow modifications, so that the information can be incorporated into future system improvements.

Tools to Support Multi-Objective Management and Tradeoff Analysis

The efforts described in the previous section would benefit from a more rigorous basis for analyzing the species and ecosystem tradeoffs, which is discussed in this section. The need to develop and use tools and analyses, including examples, was discussed in NRC (2005). However, currently there are no formal decision-making tools for managing multiple species in South Florida (NRC, 2008). Multi-species and multi-objective management appears to be limited to the aforementioned interagency phone consultations to discuss possible current and future improvements to water management operations. Missing from this process are decision support tools that integrate the effects of water management decisions on multiple species and ecosystem components such as tree islands. These tools will have an especially important role to play in planning water management over the next several decades, as we await the decompartmentalization of WCA-3A and the new water sources and storage options to provide the flows needed for restoration.

The process of consultation and decision making would also benefit greatly from a clear articulation of where the hydrologic needs of Everglades target species and ecological features conflict. Because these species have life histories that have been shaped by the seasonal rhythms of water level rise and fall in

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

the Everglades, it has been suggested that the water management needs of key endangered species are compatible to the point that a single water management schedule would suffice for all (SEI, 2007). This might have been true before the Everglades was reduced in area and the flows were modified, but the population crash of snail kites, the fluctuations and recent expansion of wading birds, and the stability of Cape Sable seaside sparrows over the past decade suggest otherwise. Moreover, there is evidence that hydrologic needs of key Everglades species sometimes conflict. For example, nesting success of snail kites is negatively related to the rate of water recession during the breeding season, but water recession rates are positively related to the nesting success for wading birds (Frederick and Collopy, 1989). Initiating water recession in WCA-3 in October, which has been suggested to ensure the high concentrations of aquatic prey that are required by wood storks, would be unlikely to maintain the areas of flooded emergent vegetation that are required by snail kites for nesting from February through May (SEI, 2007).

Conflicts between species’ hydrologic needs may also have a spatial dimension that has been created by the damming effect of the Tamiami Trail. For example, opening the S-12 gates on the western side of WCA-3 earlier in the late fall or winter to release more water into western Shark River Slough would likely have adverse impacts on Cape Sable seaside sparrow subpopulation A, but it would likely reduce the degradation of tree islands and ridge and slough landscapes within southern WCA-3A that are used for nesting and foraging by wading birds and kites (SEI, 2007).

Decision tools that create a common and comparable framework across species and Everglades ecosystem features are available in various forms, and they should be adapted as necessary and applied to more fully assess potential tradeoffs and to identify risks (NRC, 2005; SEI, 2007). These tools should support simultaneous evaluation of the effects of water management decisions on snail kites, Cape Sable seaside sparrows, tree islands, and other species or ecological processes of concern. To do so, these tools would need to directly or indirectly connect hydrology (e.g., water depths or stages, recession rates) to

  1. habitat conditions (e.g., in the form of Habitat Suitability Index Models (HSIs). HSIs can be graphical, logical, or mathematical models based on species-habitat relationships that can be tested and continually improved;

  2. specific demographic rates in the form of statistical models. For example, several snail kite demographic traits related to hydrology in WCA-3 that could form the basis of a demographic model are demonstrated in Figure 4-9; and

  3. rates of population change in the form of population models that integrate the effects of hydrology on changes in population size or on multiple

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

demographic traits that are used to calculate population change with matrix population models.

Tools would provide ways to weight the relative values of performance metrics, species, or features to quantify tradeoffs. While different kinds of decision support tools could be used for different species or processes, their results would be integrated. Using multiple models of differing complexity for the same species or features allows the triangulation of inference about management options and is increasingly seen as a useful approach to support decisions. Science managers and restoration decision makers should also take advantage of tools that already are in use, evaluate their relevance to this situation, and adapt them as needed.

CONCLUSIONS AND RECOMMENDATIONS

The reduced extent, altered topography, and reduced storage of the modern Everglades make it infeasible to achieve the same degree of restoration throughout the remnant system. Hydrologic conditions may even worsen in some areas in order to achieve desired outcomes in others. In particular, northern WCA-3A and -3B have experienced substantial drying, peat loss, and subsidence, which makes it challenging to maintain suitable water flow, levels, and hydroperiods there.

Hydrologic interdependencies of regions within the Everglades and the associated ecological tradeoffs that result from restoration and water management decisions need to be rigorously analyzed from a whole-system perspective and clearly communicated to decision makers and stakeholders. The CERP lacks a formal approach for evaluating in a transparent way the systemwide benefits of alternative restoration plans or policies, although RECOVER scientists have made good use of hydrologic models and performance measures to evaluate the design and staging of the CERP. RECOVER, in collaboration with water managers and decision makers, should develop evaluation methods to quantify and integrate across the tradeoffs required to sustain Everglades’ species and features to assess the systemwide restoration benefits. Any consideration of the ecological risks associated with water management should consider the timescales over which adverse ecological outcomes might be reversible, if they are at all.

Increasing water storage (and associated water quality treatment) is a major near-term priority. Over the next 5–10 years, CERP and pre-CERP projects will improve the conveyance and distribution of water in southern WCA-3A and Everglades National Park. But until additional water of sufficient quality becomes available, the restoration benefits will be modest and could result in shorter hydroperiods and more severe dry-down events in northern WCA-2A and northern WCA-3A. The IDS does not currently have a plan for water storage

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×

to support planned projects in the remnant Everglades ecosystem, aside from the stalled EAA A-1 Reservoir, and the benefits of the EAA A-1 Reservoir to the remnant Everglades remain unclear.

WCA-3 is a growing focus of public controversy and management concern because of its location and the way the entire system is operated to manage water distribution and quality. WCA-3A supports extensive and relatively intact landscapes including ridge and slough patterns and tree islands and provides critical habitat for endangered species, such as the snail kite and wood stork. It is the homeland of the Miccosukee Tribe of Indians and supports the tribe members’ traditional and contemporary lifestyles. Over the past decade, however, there have been drastic declines in snail kite numbers and nesting success in WCA-3A, as well as continued slow declines in tree island size and number. The imminent loss of the snail kite from WCA-3A may precipitate a crisis in water management. To some degree, this situation has been exacerbated by the current operation of the compartmentalized Everglades that alters flows across the Tamiami Trail to restore Cape Sable seaside sparrows and ecosystem functioning in Everglades National Park.

In light of the rapidly deteriorating conditions in WCA-3A, improvements in operations could lead to important near-term restoration progress. The committee commends the cooperative, multi-objective approach to improve near-term operations that is reflected in the ERTP and encourages continuation of this approach, supported by rigorous scientific analysis and decision tools, beyond the November 2010 end point. This process has the potential to align water management in the water conservation areas with a schedule that responds more flexibly to real-time conditions.

Improved species models and multi-objective decision analysis tools are urgently needed to provide more rigorous scientific support for water management decisions. Multi-objective decision tools can be used to help evaluate hydrologic effects and water-level management options on threatened species, ecosystem features such as tree islands, and critical ecosystem processes.

Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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×
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Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
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Suggested Citation:"4 Challenges in Restoring Water Timing, Flow, and Distribution." National Research Council. 2010. Progress Toward Restoring the Everglades: The Third Biennial Review - 2010. Washington, DC: The National Academies Press. doi: 10.17226/12988.
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Although the progress of environmental restoration projects in the Florida Everglades remains slow overall, there have been improvements in the pace of restoration and in the relationship between the federal and state partners during the last two years. However, the importance of several challenges related to water quantity and quality have become clear, highlighting the difficulty in achieving restoration goals for all ecosystem components in all portions of the Everglades.

Progress Toward Restoring the Everglades explores these challenges. The book stresses that rigorous scientific analyses of the tradeoffs between water quality and quantity and between the hydrologic requirements of Everglades features and species are needed to inform future prioritization and funding decisions.

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