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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

2
Major Storage Components

Storage is at the heart of any attempt to restore the Everglades. A brief examination of the Restoration Plan components (Figure 2-1) shows that many of them either directly or indirectly involve storage. This chapter contains a summary and comparison of the major existing storage components (Lake Okeechobee and the Water Conservation Areas), conventional above-ground surface reservoirs (Kissimmee Basin, Everglades Agricultural Area and vicinity, and the Upper East Coast region), below-ground storage using aquifer storage and recovery (ASR; multiple projects), and in-ground storage in the Lake Belt region. Water-quality considerations are also discussed for each component in this chapter.

While seepage management and water reuse and conservation, strictly speaking, are not storage projects, they also are discussed because they affect the overall water budget and ultimately the amount of storage required in the system. Water-quality considerations are also discussed for each component. Conversely, while stormwater treatment areas provide some storage, they are addressed only with respect to their primary function of improving water quality and where they are closely associated with major storage components. Other Restoration Plan features that are not discussed in detail in this chapter include features that are small or were designed primarily as “flow-through” structures in conjunction with ASR projects.

To understand the storage components and the fluxes between them, it is helpful to be familiar with how the Everglades planners have conceptualized and modeled the hydrologic system. The primary tool used to physically model the system in the past, present, and future is the South Florida Water Management Model (SFWMM). The SFWMM simulates the hydrologic regime and the management of the system from Lake Okeechobee to Florida Bay using both lumped and distributed modeling techniques. Most of the domain is covered with a finite-difference mesh of 2 mile × 2 mile cells. However, Lake Okeechobee is modeled (or “lumped”) as a single point in space, and a simple flow balance procedure is used for other areas. The model simulates rainfall, evapotranspiration, infiltration, overland and groundwater flow, canal flow, canal-groundwater seepage, levee seepage and groundwater pumping. It incorporates current or proposed water management control structures and current or proposed operational rules (SFWMD, 1997a).

The model has been used to simulate numerous scenarios, of which three are applicable to this chapter. The first (Figure 2-2) is of the system infrastructure and operations as they were around 1995 (the “1995 Base,” often referred to as the “current condition” or “existing condition”). The input data include a 31-year climatic record (1965-1991), recently extended in the Initial Comprehensive Everglades Restoration Plan (CERP) Update to 36 years. Both very wet and very dry years are included. The update, which is ongoing, will soon be reflected in new

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-1. Restoration Plan components.

SOURCE: Available online at http://www.evergladesplan.org/images/cerpmap_200.jpg.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-2. Primary water budget components for a 31-year simulation of the SFWMD model using the structures in place in 1995 (the “1995 Base” case of the Restoration Plan). It is considered by restoration managers to reflect the typical “current condition” of the system.

SOURCE: Available online at http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/95BSR/WBUD/95BSR.pdf.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

base scenarios and model runs, but until then, the 1999 CERP still is the reference. Information on the update is at http://www.evergladesplan.org/pm/recover/icu.cfm.

The second scenario uses the same climatic record as the 1995 Base, but reflects the likely system infrastructure and operations as they would be around 2050 without any of the Restoration Plan projects in place (the “2050 Base,” also referred to as the “future without project” condition or the “no-action alternative”). Despite increased water-use demands and other differences, this has many similarities with the 1995 Base and is not shown here. The third (Figure 2-3) is a simulation using the same projected land use and water demands as in the 2050 Base, but also assuming completed Restoration Plan (and other) projects. It is known as alternative D13R after its SFWMM run number. Note the additional components in Figure 2-3 relative to Figure 2-2, including aquifer storage and recovery, surface storage, and wastewater reuse. Comparing the storage and flows estimated by alternative D13R and similar runs with those of the 1995 Base and 2050 Base is a major approach used to evaluate potential achievement of hydrologic goals for the restoration effort. We use the simulation results for the 1995 Base and the alternative D13R to provide estimates of storage capacity for various current and planned storage components. This committee has not conducted a critique of the SFWMM, and recognizes—as do the USACE and the SFWMD—that it probably is not a perfect representation of current or future conditions. Nonetheless, the simulation results are useful for comparing the relative magnitudes of storage capacity associated with current and planned elements of the Restoration Plan. Figure 2-4 illustrates, qualitatively, an estimate of flow patterns before any of the human modifications to the system that began in the 1880s.

CURRENT STORAGE COMPONENTS

In the current system, the major available storage components are Lake Okeechobee and the Water Conservation Areas (Table 2-1; Figures 2-1 and 2-2). When fully implemented, the Restoration Plan anticipates capturing a large amount of the water currently discharged to the sea and storing it using a variety of structures and operational strategies that are major components of the plan. The major storage components of the plan discussed in this chapter are described in subsequent sections in terms of land requirements; costs for construction, operation and maintenance; constraints on sequencing of construction or implementation; design and operational complexity and flexibility; potential environmental risks and benefits; water quality issues; and advantages and disadvantages relative to other storage options. A map of existing facilities and structures managed by the South Florida Water Management District can be found at http://www.sfwmd.gov/images/pdfs/facility_map_overview.pdf.

Lake Okeechobee

Historically, the lake (Figures 1-1 and 2-5) served as the key hydrologic link between the mostly upland ecosystems in its large drainage basin to the north—the Kissimmee River Basin—and the sawgrass marshes and prairies of the Everglades proper to the south. Water storage provided by the large lake moderated the effects of low rainfall periods on the Everglades. Over the past century, the lake and its drainage basin have been greatly modified for flood control and other water management purposes, and it has become a highly engineered reservoir with numerous options for managing inflows, outflows, and water levels.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-3. Primary water budget components for the June 1998 model run D13R of the Restoration Plan. This is a simulation using the same 31-year climatic record (1965–1991) as the 1995 (and 2050) Base simulations, but using projected 2050 land use and water demands and assuming the Restoration Plan and other related projects have been implemented. There are very slight differences in the flows in this figure and the flows in Table 2-1, which is based on a slightly updated (November 1998) version of D13R.

SOURCE: http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/ALTD13R/WBUD/D13R.pdf.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-4. A qualitative depiction of the original flow patterns in the Everglades.

SOURCE: Available online at http://www.evergladesplan.org/maps/historic_flow.jpeg.

On an annual basis under current operating conditions, Lake Okeechobee receives approximately 1.6 million acre-feet of inflow from the Kissimmee River and discharges approximately 416,000 acre-feet of coastal waters through the Caloosahatchee River and St. Lucie Canal. An additional 227,000 acre-feet of water are discharged to the Water Conservation Areas from Lake Okeechobee in a combination of regulatory releases to control stage in Lake Okeechobee and environmental releases to replace reductions of flow due to implementation of best management practices (BMPs). A total of 471,000 acre-feet from Lake Okeechobee is sent to agricultural areas in the Caloosahatchee and St. Lucie Basins to the west and east, and to the Everglades Agricultural Area to the south. The Water Conservation Areas (WCAs) receive additional inflow from drainage canals in the Everglades Agricultural Area (EAA; 917,000 acre-feet) and other adjacent areas (Figure 2-2).

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

TABLE 2-1 Storage Components of the Restoration Plan

STORAGE COMPONENT

Avg Annual Acre-feet in

Avg Annual Acre-feet out

MaxAnnual Acre-feet In

MaxAnnual Acre-feet out

Max annual inflow-outflow

Total Capacity Acre-feet

ASR capacity for 30% inj loss

Construction Costs

O&M Costs (per yr)

Land Acres

Land Costs

Lake Okeechobee

2,537,300

1,803,400

4,263,200

4,022,700

2,231,900

2,250,000

 

Water Conservation Areas

1,633,200

316,100

3,138,600

567,200

2,879,200

1,882,000

Conventional Surface Reservoirs

 

North Storage Reservoir (Kissimmee)

127,000

51,700

450,200

311,700

267,000

200,000

 

95,134,000

1,515,245

20,000

189,720,000

EAA Reservoirs

440,900

418,100

1,036,900

959,400

260,700

360,000

350,112,000

14,458,409

17,500

86,536,000

C44 Reservoir

19,530

9,550

57,960

58,870

43,820

33,150

118,859,000

?

3,315

125,879,375

Other Upper East Coast Reservoirs

 

97,000

174,199,000

?

9,458

130,055,433

Taylor Creek/Nubbin Slough

 

93,700

 

168,800

 

50,000

79,326,000

2,164,114

10,000

189,720

Caloosahatchee (C-43) Basin

395,140

337,650

725,570

661,810

167,590

160,000

inc. in C-43 ASR

inc. in C-43 ASR

20,000

132,621,000

Central Palm Beach Reservoir

77,200

73,200

106,400

96,100

20,000

19,920

inc in CPB ASR

Inc. in CPB ASR

1,660

57,657,000

Site 1 Reservoir

81,200

82,200

116,000

116,500

5,700

14,760

inc in Site 1 ASR

inc in Site 1 ASR

2,458

23,587,000

Bird Drive Reservoir

138,300

18,800

150,900

38,000

147,800

11,600

52,459,000

1,470,869

2,877

71,625,000

Acme Basin

 

4,950

 

Seminole Tribe Big Cypress

 

7,440

 

Total conventional reservoirs

1,279,270

1,084,900

2,643,930

2,411,180

912,610

958,820

870,089,000

19,608,637

87,268

817,870,528

ASRs

 

Lake Okeechobee ASR

259,100

134,600

1,120,100

521,700

1,120,100

3,859,500

1,449,870

1,108,797,000

25,000,000

300

7,515,000

Caloosahatchee (C-43) Basin ASR

97,910

47,630

170,500

139,200

170,500

1,558,680

648,117

313,574,000

6,707,889

inc. in C43 res

 

C-51 (North Palm Beach II) ASR

80,500

24,200

135,700

73,000

132,000

1,745,300

996,650

122,391,000

1,496,000

34

9,945,000

West Palm Beach ASR (L-8 ASR)

37,800

11,700

54,600

32,800

54,600

809,100

457,560

53,428,000

?

?

?

Central Palm Beach Reservoir ASR

42,300

28,500

74,700

48,700

59,500

427,800

34,410

66,442,000

1,019,500

inc in CPB res

 

Site 1 Impoundment (Hillsboro) ASR

55,700

23,000

106,800

56,200

100,300

1,013,700

495,690

116,792,000

2,052,608

inc in site 1 res

 

Total ASRs

573,310

269,630

1,662,400

871,600

1,637,000

9,414,080

4,082,297

1,781,424,000

36,275,997

334

17,460,000

In Ground Reservoirs

 

North Lake Belt

146,600

142,600

180,400

189,600

34,300

90,000

 

381,193,000

1,241,234

5,861

154,868,000

Central Lake Belt

100,500

95,000

237,100

238,700

196,000

190,000

 

402,502,000

1,964,519

5,770

100,359,000

L-8 Basin

76,000

76,700

101,900

118,600

55,300

48,000

 

?

?

1,200

?

Total in-ground reservoirs

323,100

314,300

519,400

546,900

285,600

328,000

0

783,695,000

3,205,753

12,831

255,227,000

Seepage Management

 

WCA3A/3B Levee Seepage Mgmt

 

128,600

 

57,526,000

783,432

5,887

167,646,000

C-11 Reservoir (part of 3A/3B seepage)

68,300

80,700

121,300

144,000

0 (gw inflow makes updeficit)

 

L-31N Seepage Mgmt

 

161,900

 

89,514,000

4,647,234

3,947

94,704,000

Total seepage management

 

371,200

 

147,040,000

5,430,666

 

262,350,000

Water Reuse

 

West Miami-Dade Water Reuse

 

111,000

to Bird Dr. Rech

112400(to Bird Dr. Rech)

435,998,000

36,500,000

100

3,540,000

South Miami-Dade Water Reuse

 

73,730

(south to C-102)

 

359,700,000

47,815,000

200

3,324,000

 

 

73,000

(north to C-100)

 

Total water reuse

 

257,730

 

795,698,000

84,315,000

 

6,864,000

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

Data sources and other notes for Table 2-1

Many values in the table are based on simulation output, which are reported to more significant figures than can be verified. These values provide only general comparisons of the magnitudes of flows and storage capacity, as no quantitative estimates of uncertainty are available. While every attempt has been made to verify the information in this table, the Restoration Plan is continually being modified, so storage, flux, acreage, and cost information are evolving with it. Likewise, quantitative information for closely related projects, such as reservoirs and stormwater treatment facilities, is sometimes lumped. Up-to-date information on these projects can be obtained at any time from the USACE and SFWMD. There are very slight differences in the flows given in this table and those shown in Figure 2-3. Both are based primarily on output from alternative D13R of the South Florida Water Management Model; however, this table is based on a slightly updated (November 1998) version of D13R relative to Figure 2-3, which is based on a June 1998 version of D13R.

Fluxes

Most fluxes are from water budget for D13R (11/98 version)

(http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/D13R1198/WBUD/annbud).

South and West Miami-Dade water reuse fluxes from Appendix B, section B.3.5.8.1, p. B-192 of USACE and SFWMD (1999), except for Average Annual West Miami-Dade Reuse, which is from M. Irizarry,

SFWMD, personal communication, November 2004.

See Fig. B.3-88 for bar graph of volumetric savings from water use reductions.

Inputs to reservoirs do not include local precipitation or seepage.

Outputs from reservoirs do not include evapotranspiration or ASR injection losses.

Water fluxes to and from Water Conservation Areas (WCAs) include overland flow and groundwater seepage.

Seepage management “annual acre-ft out” for WCA3A/3B and L31-N from J. Obeysekera, SFWMD, written commun., May 2004, and computed as “seepage prevented” between D13R and 2050base.

Capacities

Most capacities are from individual project descriptions at http://www.evergladesplan.org/pm/projects/project_list.cfm.

Reservoir capacities for C-44 and Upper East Coast Reservoirs taken from the Indian River Lagoon Project Implementation Report

Lake Okeechobee capacity approximated from data summarized in table 3-2 of this report, and is the volume at max allowable stage (18.5 NGVD) minus the volume at min allowable stage (13.5 NGVD).

WCA capacity from Light and Dineen (1994); also based on current regulation schedule.

ASR “capacities” refer to injected water remaining in the aquifer after the 31 year simulation and are calculated as (avg. annual acre-feet in - avg. annual acre-feet out) × 31 years

ASR “capacities” for 30% injection loss refer to usable (non-saline) water remaining in the aquifer after the 31 year simulation and are calculated as (0.7 × avg. annual acre-feet in - 1 × avg. annual acre-feet out) × 31 years.

Construction, O&M, and Land Costs; Acreage

Acreages from Table 9-1 of USACE and SFWMD (1999).

Construction and Real Estate Costs in 1999 dollars from Table 9-2 of USACE and SFWMD (1999).

O&M Costs in 1999 dollars from Table 9-3 of USACE and SFWMD (1999). Construction and land costs for C-44 and Upper East Coast Reservoirs taken from the Indian River Lagoon Project Implementation Report. These costs are in 2003 dollars.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-5. Drainage basin of Lake Okeechobee.

SOURCE: SFWMD et al. (2004).

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

Although Lake Okeechobee no longer provides the hydrologic services to the Everglades that it provided in its natural state, it still provides substantial water storage under current operating conditions. The lake’s surface elevation and associated area and volume vary considerably both intra-annually and inter-annually in response to wet and dry climatic conditions, but at a normal high-water stage of 15 feet (4.6 m) above mean sea level, the lake has a surface area of 700 mi2 (1814 km2), an average depth of 9 ft (~2.7 m), a maximum depth of 15.5 ft (4.6 m), and a volume of 4.0 × 106 ac-ft (4.9 × 109 m3). The lake has a maximum north-south (open-water) length of 35 miles (56.5 km) and maximum east-west length of 29.6 miles (48 km).

The natural drainage basin for Lake Okeechobee is primarily north of the lake (Figure 2-5), and the Kissimmee River is by far the largest tributary. The Kissimmee River Basin extends north almost 100 miles to near Orlando, Florida and accounts for about 60 percent of the lake’s 5,022 mi2 (13,000 km2) drainage basin (including the area of the lake itself) (http://www.esg.montana.edu/gl/huc/03090101.html). As noted above, annual water inputs to the lake vary substantially, but typical values are in the range 1,500,000 to 3,300,000 ac-ft (2.0-4.7 × 109 m3), resulting in a range of water residence times in the lake of about 1-3 years.

A lake-stage regulation schedule has been used to manage lake levels for several decades. The schedule is modified periodically to reflect changes in management goals. The most recent of these is the “Water Supply/Environmental” (WSE) regulation schedule that was approved in July 2000 (http://www.sfwmd.gov/org/pld/hsm/reg_app/lok_reg/). In general, the schedule provides for maximum lake stage in winter and spring and lower stage during summer and fall to provide storage capacity for inflows associated with the summer rainy period and hurricane season. The storage volume available in Lake Okeechobee is a function of the regulation schedule (Figure 2-6). The maximum available storage under current operating conditions may be considered simply as the difference between the maximum allowed stage, 18.5 ft NVGD (National Vertical Geodetic Datum, essentially equivalent to mean sea level) and the minimum stage under which regulatory discharge is allowed (13.5 ft NVGD), if we assume that over a wet-dry climatic cycle there is no net loss of this storage to the sea. This volume (interpolated from Table 2-2) is 2,250,000 acre-feet (3.2 × 109 m3). This maximum storage volume is insufficient to accommodate the average annual inflows of approximately 2.5 million acre-feet from sources excluding local precipitation during the 31-year record used to evaluate the Restoration Plan and is much smaller than the maximum annual inflow of over 4 million acre-feet in that record. The Restoration Plan will modify the current operating rules, but the objective of these modifications is not to provide additional water storage. Based on the maximum change in lake storage simulated in the D13R run, 2,231,800 acre-feet (Table 3-1), the potential storage capacity of the lake will be virtually unchanged by implementation of the Restoration Plan.

Use of Lake Okeechobee as a storage option was explored in a screening phase of the Restudy (i.e., the formal evaluation process that culminated in the Restoration Plan) but was not included in any of the project alternatives. The goals used in the screening evaluation of Lake Okeechobee were to prevent discharge to the Caloosahatchee and St. Lucie estuaries, provide water supply, and maintain water levels in the lake that were consistent with levee stability and healthy lake conditions. In the initial modeling runs the latter objectives were ignored, in that no restrictions were placed on water levels. These runs demonstrated that maximal use of storage in Lake Okeechobee would be “cost effective and hydrologically efficient” (USACE and SFWMD, 1999). They also demonstrated that such use would cause extreme fluctuations in lake levels, fluctuations that would be expected to adversely affect the littoral zone of the lake. The planned

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-6. “Water Supply/Environmental” (WSE) regulation schedule for Lake Okeechobee.

SOURCE: Redrafted from http://sfwmd.gov/org/pld/hsm/reg_app/lok_reg/wse_support/wse_sched.pdf.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

TABLE 2-2 Stage-Volume and Stage-Area Relations for Lake Okeechobee

Stage (ft.)

Volume (acre-feet)

Surface area (acres)

0

0

 

8

1,442,000

284,000

9

1,729,000

299,000

10

2,039,000

316,000

11

2,366,000

339,000

12

2,722,000

371,000

13

3,108,000

395,000

14

3,527,000

436,000

15

3,980,000

448,200

16

4,425,000

452,200

17

4,875,000

466,000

18

5,335,000

459,000

19

5,790,000

462,400

20

6,260,000

466,000

21

6,730,000

470,200

22

7,195,000

475,000

SOURCE: Available online at http://www.sfwmd.gov/org/pld/hsm/reg_app/opln/orm/input_new.orm.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

modifications that were ultimately incorporated in the Restoration Plan are intended to further reduce stage fluctuations that may have detrimental effects on the littoral zone habitat, water supply for surrounding communities and agriculture, and levee integrity. Thus, these modified rules will likely reduce the available storage in the lake in any year compared to the current operating rules.

Water-Quality Considerations

Much of the water that eventually makes its way to the southern Everglades, both under current conditions and those anticipated in the plan, passes through Lake Okeechobee. Thus, water quality in the lake can affect water quality elsewhere in the system, with effects greater in the northern parts of the system (Weaver and Payne, 2004). It also can affect the lake’s ecological status.

In terms of basic water chemistry and limnology, Lake Okeechobee is a hard-water, alkaline lake with moderately high dissolved solids, high pH, elevated concentrations of nutrients and dissolved organic matter, and (usually) low water clarity (Table 2-3). The lake is considered eutrophic; it has high nutrient and chlorophyll concentrations. Water quality conditions are not constant across the lake but vary in response to local inputs and conditions. For example, humic color tends to be highest in western and northwestern areas of the lake because of high loadings from tributaries (e.g., Fisheating Creek) draining extensive wetland areas. Water clarity varies considerably over time as well as in a spatial context. Low water clarity conditions generally reflect high concentrations of suspended solids from resuspension of fine-grained, organic-rich bottom sediments and/or from algal blooms, but low clarity (in terms of light penetration) also occurs in areas with high levels of humic color.

The main issues of concern regarding water quality in the lake and its effects on use of the lake as a water source for the Everglades all are related to nutrient overenrichment, which has been the primary concern of lake managers and limnologists throughout the period of modern studies on the lake. These studies began around 1970 and are described in more detail and in a historical context in chapter 4. Phosphorus is the primary nutrient of concern, although high external loadings of nitrogen contribute to the problem, and very high concentrations of nitrogen in surface runoff from the EAA led to the limitations on backpumping EAA water into the lake in the 1980s.

The effects of high nutrient loadings on the lake are essentially the standard ones leading to lake eutrophication: high concentrations of algae and increased frequency of algal “blooms” (visible growths of algae); increased dominance of blue green algae (cyanobacteria), which are a nuisance form of algae; and increased suspended solids concentration in the water column, with attendant loss of water clarity. Eutrophication typically results in changes in the higher trophic levels of a lake’s food web, and these likely have occurred in Lake Okeechobee in the form of changes in the zooplankton and fish communities. Despite those changes (e.g., an increased population of planktivorous threadfin shad, Dorosoma petenense), it remains a prized resource for largemouth bass (Micropterus salmoides). Changes in the littoral-zone macrophyte community also have occurred over the past 30-40 years, including increased occurrence of nonnative invasive species, but other factors (including changes in lake levels) also affect the distribution and abundance of macrophyte species, and it is difficult to attribute these directly to the lake’s high nutrient loadings.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

TABLE 2-3 Summary of Lake Okeechobee Water Quality Characteristics, 1994-2003*

Characteristic

Units

n

Mean

Median

Range

Std. Deviation

Specific conductivity

µS cm-1 1305

469

460

132-863

89

 

Color

PCU

1309

42

33

2-600

35

Dissolved oxygen

mg L-1

1287

8.2

8.1

4.4-13.5

1.1

pH

 

1297

8.2

8.2

4.5-9.2

0.4

Total alkalinity

meq L-1

1250

2.04

2.04

0.52-4.02

0.36

Chloride

mg L-1

1232

59

57

0.5-95

15

Total suspended solids

mg L-1

3610

19

13

1-234

19

Turbidity

NTU

1335

28

20

2-173

23

Secchi depth

cm

3349

50

49

5-220

27

Soluble reactive phosphorus

mg m-3

3516

25

16

4-1123

29

Total phosphorus

mg m-3

3572

94

83

4-1060

53

Ammonium-N

mg m-3

3533

13

10

9-445

13

Nitrate-N + Nitrite-N

mg m-3

3468

118

25

4-1022

155

Total organic N

mg m-3

3521

1370

1320

440-4080

330

Total chlorophyll a

mg m-3

3429

27

23

1-146

17

Corrected chlorophyll a±

mg m-3

3420

23

18

0-122

15

Notes:

*Values for South Florida Water Management District sampling stations L001-L008; From T. James, SFWMD, written communication, July 2004. Some units were changed and the numbers converted from the SFWMD data.

Explanation of units: µS cm-1 = microSiemens per centimeter; PCU = platinum-cobalt units; mg L-1 = milligrams per liter; meq L-1 = milliequivalents per liter; NTU = nephelometric turbidity units; cm = centimeters; mg m-3 = milligrams per cubic meter.

n = number of measurements over all stations and years.

Calculated from measured total Kjeldahl N minus ammonium-N.

±Total chlorophyll a minus phaeophytin a; an estimate of chlorophyll a in living cells.

The high levels of suspended solids and algae in the lake water also lead to secondary impacts on treatability of the water for drinking purposes (e.g., taste and odor problems, increased chlorine demand, difficulties in clarifying the water, and increased formation of toxic disinfection by-products such as trihalomethanes).

Efforts to manage nutrient loadings (especially phosphorus) to the lake have been underway since the mid-1970s (see Chapter 4 for details), but these have been only partially successful and have not resulted in reducing phosphorus concentrations in the lake itself. In fact, phosphorus concentrations are substantially higher in the lake today than they were when these efforts began. These trends may be explained at least in part by an increasing role of internal phosphorus loading (from the bottom sediments) in maintaining high phosphorus concentrations in the water. Over a period of decades, excessive external loadings of phosphorus to the lake resulted in a build-up of phosphorus concentrations in the near-surface sediments and also probably led to the build-up of more flocculent and less cohesive organic sediments at the sediment surface. Such flocculent sediments are more easily resuspended by wind-induced turbulence than more cohesive mineral sediments would be. The net effect is that Lake Okeechobee may have been transformed effectively into a self-sustaining eutrophic system by the decades of high external nutrient loading such that it no longer relies primarily on external nutrient sources to support its high algal productivity. If this is the case, further management of external phosphorus loads to the level in a proposed TMDL (Havens and Walker, 2002) will not quickly produce predicted benefits in water quality. However, on a longer time-scale (probably measured in decades), the lake should become a net exporter of phosphorus as it readjusts to the new (smaller) external

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

loads—that is, some of the phosphorus recycled from the sediments will be lost from the lake in surface outflows each year, and over time the sediments will become a less important contributor to maintenance of high algal abundance in the lake.

Implications of the above discussion on use of Lake Okeechobee for additional water storage are fairly clear, at least in the short term. Nutrient concentrations in the lake are high relative to the very low concentrations in the Everglades, and some treatment of the water by passage through wetland marshes in the northern part of the Everglades (EAA, northern Water Conservation Areas) should be done (Odum and Odum, 2003) before the lake water reaches those oligotrophic areas. However, phosphorus concentrations in the lake still are low compared with those currently in EAA water and other contaminated stormwater in the system. Over time (decades), as management of external loads to the lake is achieved and the lake is allowed to purge itself of its contaminated sediments, phosphorus concentrations will decline in the lake. It is unlikely that they ever will be as low as those in the southern Everglades, but this also was probably true even in the pristine system. Current water discharges from the lake to the Everglades already receive treatment by STAs, although STAs might not remove enough phosphorus to help achieve the phosphorus criterion for the Everglades Protection Area, discussed in more detail in the Kissimmee Basin Section.

Water Conservation Areas

The central Everglades were converted into surface-water reservoirs called the Water Conservation Areas (WCAs) (Figure 2-7) when levees were completed in 1961-63. This state-owned region contains the southern portion of the sawgrass plain and the northern portion of the ridge-and-slough landscape. Currently the WCAs are managed to detain excess surface water from the EAA and parts of the east coast region. Water in the WCAs serves many competing uses: providing flood control, augmenting water supply along the east coast and in Everglades National Park, recharging groundwater in the Biscayne Aquifer, reducing seepage, and providing habitat for Everglades wildlife (USACE and SFWMD, 1999).

The WCAs have a combined storage capacity of 1,882,000 acre-ft (Light and Dineen, 1994). Under the current water-regulation schedule, the WCAs receive average inflows of almost 1,800,000 acre-ft per year through a combination of flood control and environmental discharges from Lake Okeechobee and the EAA, plus drainage from surrounding areas. The WCAs discharge 862,000 acre-ft per year to Everglades National Park through a combination of groundwater seepage and releases for flood control and environmental water supply. Water supply deliveries plus groundwater flow and seepage discharge an additional 849,000 acre-ft per year to the Lower East Coast (Figure 2-2). The WCA water regulation schedules are driven by two objectives inconsistent with natural system requirements: minimizing flood risk during hurricane season and maximizing storage during the dry season. The ecological values of the WCAs thus are compromised by pulsed rather than attenuated water flow, altered hydroperiods, localized pooling and over-drainage associated with canals and levees, and reduced flow of water southward (Light and Dineen, 1994).

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-7. Location of water conservation areas. SOURCE: Information on locations of existing and proposed storage components from USACE and SFWMD.

Because the WCAs still contain significant remnants of the original sawgrass plain, ridge-and-slough wet prairies, and tree islands, they offer a major opportunity for Everglades restoration. Current additions and removals of water from the WCAs reflect their use as reservoirs of the water variously desired or unneeded by surrounding managed areas. The levees that form the WCA impoundments also create pooled waters that are too shallow at the upstream end and too deep downstream. Ecologically appropriate water depths occur only in some portions of the WCAs. If a more natural sheetflow and hydroperiod can be established, a single, physically free-flowing freshwater landscape will exist in the combined state and federal properties, improving prospects for recovery of the ecological systems and dynamics in about half of the original Everglades. The central location and function of the WCAs causes them to affect or be affected by other restoration projects.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

To restore more natural water levels and flows within the WCAs, a set of Restoration Plan projects is planned to decompartmentalize the WCAs by removing a number of barriers to sheetflow such as portions of the Miami Canal, which would be backfilled for several miles, and the Tamiami Trail, which will be elevated by installing a set of bridges; and removal of the levee L-29. These activities are described in the Project Management Plan for the WCA-3 Decompartmentalization and Sheetflow Enhancement Project Part 1 (http://www.evergladesplan.org/pm/program/program_docs/pmp_12_wca/decomp_main_apr_2002.pdf).

Currently, paths of uninterrupted water flow through the ridge-and-slough landscape are only 30 miles long, less than one-third of their original length. If decompartmentalization is completely successful, 70 miles of continuous flow paths will be restored, from the terminus of the Everglades Agricultural Area to Whitewater Bay. Water depths in the restored area are projected to slope continuously, without discontinuities, from the southern border of the Everglades Agricultural Area to Whitewater Bay. Water levels will rise and fall seasonally under the combined influence of rainfall and rainfall-driven additions of water along the upstream boundary of the restored area. Flows will approximate pre-drainage flows through the landscape, and they will protect tree islands from excessive water depths at the end of the wet season and damaging soil oxidation during the dry season. Water will not flow exactly as it did before drainage, however, because of the canals and levees to the east and north of the present-day Everglades.

These “decompartmentalization” components will alter the water sources to the WCAs, with a larger portion of the annual inflow coming in the form of overland flow. However, the total average inflow will increase only slightly, from approximately 1,800,000 to nearly 1,900,000 ac-ft/yr. Outflows to Everglades National Park will increase. (A careful examination of the simulation results summarized in Table 2-1 shows that the maximum difference between inflows and outflows over a year of the D13R simulation, 2,879,000 ac-ft, significantly exceeds the storage capacity for current operations. That might suggest that the Restoration Plan will lead to large increases in water storage in the WCAs. But the large volume of water lost to evapotranspiration from the WCAs will result in an average annual change in WCA storage of only 19,900 ac-ft as simulated by D13R. The maximum change in storage in any year is 1,523,100 ac-ft, somewhat lower than the storage capacity for current conditions.)

However, as impressive as the engineering will be, this is not the end in itself: the end is maintenance and restoration of the original landscape pattern. Simultaneous restoration of unimpeded flows and correct water depth variations is, along with restoration of water quality, the critical driving force that will maintain and restore the pattern of peat landscape originally present in this portion of the Everglades. The patterning of ridges, sloughs, and tree islands, each originally of different elevation, is a key to supporting the wildlife of the pre-drainage Everglades. The multitudes of otters and alligators once present and the populations of multi-year, larger fish all depended on persistence of the ridge and slough pattern to provide year-round aquatic habitat. Persistence of peat-based tree islands themselves may have been closely tied to the pattern of flows and water depths (NRC, 2003c).

Water-Quality Considerations

Given the physical location of the WCAs between the EAA and Lake Okeechobee to the north and west and Everglades National Park to the south, it is no surprise that water quality issues related to restoration of the WCAs are closely related to those in these adjoining areas. The primary concern is the potential for detrimental effects of excessive inputs of nutrients, espe-

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

cially phosphorus, from the EAA (and to a smaller extent from eutrophic Lake Okeechobee), on plant communities (both emergent macrophytes and periphyton) in the WCAs. As mentioned in the EAA discussion, phosphorus concentrations are highest in the north and lowest in the south (Payne and Weaver, 2004). Insofar as decompartmentalization of the WCAs should allow water to move more rapidly through the Everglades area now occupied by the WCAs, this restoration component might enhance the movement of relatively high nutrient water from the northern portions of the WCAs to more southerly areas. Stormwater Treatment Areas (STAs), which are engineered wetlands designed to remove nutrients from water by growing plants such as cattail, are supposed to mitigate the detrimental effects of excessive nutrients on plant communities in the Everglades, and are indeed reducing phosphorus concentrations. However, as noted elsewhere in this report, no STA yet constructed has produced effluent water with a phosphorus concentration as low as 10 micrograms per liter (µg L-1). (See “Water Quality Considerations” sub-section of “Kissimmee Basin” section later in this chapter for additional discussion of issues associated with STAs and phosphorus concentrations.)

High sulfate loadings from the EAA (see discussion below) also are a concern as a possible cause for sawgrass replacement by cattails. High sulfate levels in water lead to high sulfide levels in anoxic, organic-rich sediments, and sulfide toxicity may contribute to the loss of native plant communities in parts of the WCAs that receive high-sulfate and nutrient-rich water from the EAA. In addition, high sulfate levels may exacerbate the mercury pollution problem by stimulating the growth of sulfate-reducing bacteria (SRBs) in sediments and periphyton; SRBs are thought to be the principal agents of mercury methylation in the environment. Mercury issues are described further in the section “Mercury Deposition, Mobilization, and Bioaccumulation” (Chapter 3) and in the section “EAA and Vicinity,” subsection “Water Quality Considerations” later in this chapter. Of particular relevance for restoration of the WCAs is the likelihood that decompartmentalization will lead to more frequent and larger changes in water levels and more wet-dry cycles in the sediments, which are thought to stimulate pulses of mercury methylation (Krabbenhoft et al., 2000).

Conventional Surface Reservoirs

Surface-water reservoirs are a well established technology for water management. The Restoration Plan includes construction of a number of large conventional reservoirs in three main regions: the Kissimmee Basin (north of Lake Okeechobee), the Everglades Agricultural Area, and the Upper East Coast (Figure 2-8). Together, these reservoirs will provide new storage capacity of about 690,000 acre-feet. The following discussion focuses on these major reservoirs. The Restoration Plan also calls for construction of a number of other reservoirs for use in conjunction with planned ASR systems and for more local management of stormwater. Storage capacities and flux estimates (if available from the D13R water budget output) for these reservoirs are also listed in Table 2-1. These other reservoirs will provide an additional storage capacity of about 270,000 acre-feet. Additional new storage of approximately 160,000 acre-feet will be provided by numerous stormwater treatment areas (not listed in Table 2-1), designed primarily for water-quality improvement rather than storage per se.

Advantages of conventional reservoirs are the solid base of engineering design and operational principles for these structures. Disadvantages include the need for relatively large amounts of land and losses of water to evaporation during long periods of storage. Construction schedules for these features are constrained by land-acquisition schedules as well as by the availability

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-8. Location of conventional storage reservoirs. SOURCE: Information on locations of existing and proposed storage components from USACE and SFWMD.

of funds. Overall, however, these storage features are among the earliest for which construction will be completed, with planned completion dates according to the original implementation schedule ranging from 2010 for the Upper East Coast Reservoirs to 2014 for the second phase of the Everglades Agricultural Area reservoirs. The following sections provide additional information on each of the major conventional reservoir components.

Kissimmee Basin

The Restoration Plan includes a construction feature called the North of Lake Okeechobee Storage Reservoir, to be located in the Kissimmee River Region. This component includes

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

an above-ground reservoir and a 2,500-acre stormwater treatment area (STA) for a total storage capacity of approximately 200,000 acre-feet. The specific location of this facility has not been identified; however, it is anticipated that the facility will be located in Glades, Highlands, or Okeechobee Counties. The initial design of this component assumed a 20,000-acre facility (17,500-acre reservoir and 2,500-acre treatment area) with water levels in the reservoir fluctuating up to 11.5 feet above grade. The final size, depth, and configuration of this facility will be determined through more detailed planning, land suitability analyses, and design. Future detailed planning and design activities also will include an evaluation of degraded water bodies within the watersheds of the storage/treatment facility to determine appropriate pollution load reduction targets, and other water quality restoration targets for the watershed.

The Restoration Plan estimated real estate costs of almost $190 million. Construction is planned to be completed by 2013 according to the most recent version (December 2003) of the project management plan for the Lake Okeechobee Watershed component. This deadline could be optimistic if difficulties are encountered during land acquisition, which cannot begin until a final site for the reservoir is selected.

Water-Quality Considerations

The primary water-quality issue related to this storage element is likely to be elevated nutrient concentrations, particularly phosphorus, in runoff water that will feed the reservoir. The inclusion of an STA in the plan recognizes this fact. Results from existing STAs indicate that these engineered wetlands can provide substantial removal of nutrients (especially phosphorus). However, thus far no STA has produced effluent water with as little as 10 µg L-1. That concentration of total phosphorus was established as an overall criterion for the Everglades Protection Area (the Water Conservation Areas and Everglades National Park) by the Environmental Regulation Commission (ERC) in 2003 (Piccone et al., 2004). Details of the rule and methods for achieving it are contained in Florida Administrative Code 62-302.540. However, from an ecological perspective, it may not be critical that outflows from a reservoir this far north in the system precisely meet the criterion. The Everglades plant communities that require such low phosphorus levels occur further south. If the outflow from the Kissimmee reservoir were to be used, for example, to recharge Lake Okeechobee, outflow phosphorus concentrations somewhat higher than 10 µg L-1 might be reasonable.

The long-term effectiveness of STAs (over many decades) in providing a high degree of phosphorus removal remains to be tested. Clearly, the longevity of a treatment facility depends on its size relative to the loadings it must assimilate. In theory, STAs can be constructed to provide adequate capacity for many decades of inputs if sufficient acreage is provided. At some point, however, water quality and the composition of the plant communities (which is related to chemical water quality) within STAs themselves will become issues of concern. If STAs are relatively small in size, the public likely will view them as a “necessary evil,” but as they grow in number and size and occupy a larger fraction of the landscape in south Florida, the public might begin to view them as semi-natural systems that also should provide ecological amenities (beyond serving as nutrient removal basins). This is more likely to become an issue in the Conservation Areas south and east of Lake Okeechobee than in upland areas north of the lake because the former in fact represent lands that were part of the original Everglades.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

EAA and Vicinity

An above-ground reservoir system is planned for construction in the Talisman Land acquisition of the Everglades Agricultural Area (EAA), on land that is currently under sugar cane cultivation. The total storage capacity of the system will be approximately 360,000 acre-feet, divided into three equal-sized compartments that each can accommodate water-level fluctuations of up to 6 feet above grade. Compartment 1 will store excess runoff from the EAA to meet future irrigation demands. The other two compartments will be operated as dry storage reservoirs with discharges down to 18 inches below ground level to accommodate Lake Okeechobee regulatory releases and overflow from Compartment 1. Discharges from these compartments will be managed to improve timing of environmental releases to the Water Conservation Areas.

Land acquisition costs for these reservoirs are expected to be relatively low compared to those for the other two major reservoir systems because of the leverage provided by the Farm Bill. The total real estate costs estimated in the Restoration Plan are approximately $87 million. The first phase of the reservoir construction is scheduled to be completed in 2009, and the final phase in 2014.

Water-Quality Considerations

Use of land within the EAA and vicinity for surface water storage would entail at least two potentially important water-quality issues: (a) high nutrient levels in the soils, a legacy of many decades of intensive agriculture, and (b) exacerbation of the mercury pollution problem in the Everglades. EAA nutrient issues may involve both nitrogen and phosphorus. Within the Everglades Protection Area, both total phosphorus and total nitrogen concentrations are highest in the north; this primarily reflects agricultural runoff from the EAA (Payne and Weaver, 2004). Because the Everglades ecosystem is strongly limited by phosphorus and because plant communities in the Everglades are adapted to these low levels, phosphorus is the primary nutrient of concern in the Everglades itself. Nonetheless, elevated nitrogen concentrations would be a concern if water from EAA storage facilities reached nitrogen-limited parts of Florida Bay (NRC, 2002b). The Restoration Plan assumes that STAs would be required to treat water from EAA storage reservoirs before it was released to the Everglades, and the considerations discussed previously with regard to the effectiveness and sustainability of STAs apply here. STAs rely primarily on plant assimilation for nutrient removal. Thus, they should be reasonably effective for nitrogen as well as phosphorus—provided that the incoming waters have reasonably well-balanced ratios of nitrogen to phosphorus relative to plant growth requirements. Because of the proximity of EAA lands to Everglades lands that are adapted to low levels of phosphorus, attainment of the 10 µg L-1 effluent criterion is likely to be critical to avoid alteration of the oligotrophic plant and periphyton communities associated with the Everglades.

EAA storage reservoirs pose a risk of mercury pollution to the Everglades by at least two mechanisms. First, recent work (Krabbenhoft et al., 2000) has demonstrated that conversion of mercury to the toxic methylmercury form, which bioaccumulates in food webs, is enhanced under conditions where soils and sediments undergo cycles of wetting and drying. Exposure of wet soils to air under drying conditions promotes oxidation of reduced sulfur species in soil to form sulfate, the electron acceptor required by sulfate-reducing bacteria to grow when the soils again are inundated and anoxic conditions develop. Sulfate-reducing bacteria are thought to be the primary agents of mercury methylation in soil and sediment environments. Krabbenhoft et al.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

(2000) showed that enhanced mercury methylation occurs in mesocosms containing Everglades soils subjected to repeated wet-dry cycles. EAA surface reservoirs for Everglades restoration will involve cycles of storage and draw-down that will expose the soils to repeated wet-dry cycles, and thus they may promote the formation of methylmercury that can be transported into the Everglades when water is released from the storage reservoirs.

Second, EAA soils have elevated levels of sulfur from past agricultural management practices; elemental sulfur is added to sugarcane grown on organic soils (300-500 lb S/acre) as an acidifying agent to mobilize micronutrients. (Oxidation of elemental sulfur to sulfate produces hydrogen ions and lowers the soil pH, thus enhancing trace metal availability for plant growth.) This practice explains the relatively high sulfate levels of EAA runoff that flows into WCA-1 and WCA-2 (59 ± 19 mg L-1 and 52 ± 19 mg L-1, respectively in 2003; Weaver and Payne, 2004). In contrast, sulfate levels in surface waters of the southern parts of the Everglades tend to be very low (~1-3 mg L-1 for waters within Everglades National Park; Table 2A-7, SFWMD and Florida DEP, 2004), reflecting atmospheric deposition as the primary source, and possibly representing sub-optimal conditions for mercury methylation by sulfate-reducing bacteria.

Upper East Coast

Four reservoirs are to be constructed in the Upper East Coast as part of the Indian River Lagoon–South component of the Restoration Plan. Together, the new C-44 Reservoir (replacing an older reservoir in the basin), the C-23/24 North and South Reservoirs, and the C-25 Reservoir and associated stormwater treatment areas will provide a total of 135,000 acre-feet of storage capacity. Additional storage of approximately 30,000 acre-feet will be provided by restoration of approximately 90,000 acres of uplands and wetlands in Martin, St. Lucie, and Okeechobee Counties.

Real-estate costs for these reservoirs are anticipated to be the highest among the three reservoir systems, at over $500 million, presumably because these reservoirs will displace or preclude commercial and residential uses in an urbanized area. Construction of these reservoirs is scheduled for completion by 2010.

The Indian River Lagoon–South projects are fairly independent from most of the other Restoration Plan projects. Indeed, it is estimated that 100 percent of the watershed benefits and 88 percent of the total estuary benefits of the project will be achieved even if other Restoration Plan projects are never constructed (USACE and SFWMD, 2004).

Water-Quality Considerations

According to the Final Project Implementation Report, or PIR (USACE and SFWMD, 2004), the combination of reservoirs, constructed stormwater treatment areas, and restored wetlands are expected to reduce nutrient and sediment loading to the estuary. The report also notes that surface water stored in reservoirs will be lower in alkalinity and chloride than water pumped from the Floridan Aquifer, which will make it a preferred source of irrigation water in this region.

An independent scientific review panel (Bartell et al., 2004) was generally supportive of the project, saying that the plans as presented in the report “have a high likelihood of meeting the

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

restoration objectives.” The panel did express concerns that the PIR did not present evidence as to what “thresholds of restoration measures” will support a more natural regime of algal blooms. That is, what specific changes in freshwater residence time, and what levels of reduction of nutrient loading, will significantly influence patterns of phytoplankton production in the estuary? While adaptive management can resolve this issue to some extent, given the importance of these factors to the estuary, a better understanding is needed of the relationships of the freshwater timing and quality to improvements in the algal bloom regime. That panel was also concerned that the PIR does not include as a performance measure dissolved oxygen, and does not discuss how system responses may change dissolved oxygen concentrations in time and space.

OTHER TECHNOLOGIES AND STRATEGIES

In addition to existing storage areas (such as Lake Okeechobee and the Water Conservation Areas), and conventional surface reservoirs, the Restoration Plan envisions the use of other technologies. These include storing water underground, known as “aquifer storage and recovery,” use of completed quarries for storage (such as the so-called “Lake Belt reservoirs”), seepage management, and water reuse. While worth exploring as alternative methods of storing and conserving water, each of these technologies brings concomitant risks and uncertainties with them.

Aquifer Storage and Recovery

Aquifer Storage and Recovery (ASR) (Figure 2-9a) involves pumping water into the subsurface through deep wells for storage and then recovering the water when it is needed by extracting water from the same wells. Plans include a large-scale ASR system in the Lake Okeechobee region (Figure 2-10) and smaller systems in several other locations in south Florida that will involve over 330 wells, assuming a capacity of 5 million gallons per day (MGD) per well, corresponding to a maximum annual capacity of 1.85 million acre-feet for all wells pumping simultaneously and continuously. On an annual basis, these wells are anticipated to accommodate an average of over 500,000 acre-feet of injected water, well below the maximum annual capacity. However, the maximum estimated annual injection rates (totaling 1.66 million acre-feet according to the SFWMD model simulation results; see Table 2-1) indicate that during very wet years the ASR systems will operate near 90 percent of the total annual capacity.

Determining a total storage capacity of an ASR system for comparison with capacities of other storage components is complicated because, at least in theory, the total capacity is limited only by the available pore volume of the aquifer. However, estimates of potential capacity can be obtained by examining the water budget outputs of the 31 year simulations used to evaluate the Restoration Plan. Based on these model simulations, almost 4,000,000 acre-feet of injected water would remain in storage within the Lake Okeechobee ASR system at the end of 31 years. Of this injected water, approximately 1,500,000 acre-feet would be recoverable assuming the 30 percent injection losses that were used for the water management model computations. The simulations include a three-year period during which 1,233,600 acre-feet are recovered from the Lake Okeechobee ASR system while no water is added to ASR storage. Even assuming 30 percent injection losses, the ASR systems together make up about three-quarters of the new stor-

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-9. (a) Idealized aquifer storage and recovery system, and potential effects of (b) aquifer heterogeneity, (c) ambient flow and transport, and (d) mixing and water rock interactions. The first two panels (a and b) illustrate effects on recovery; the second two (c and d) illustrate effects during storage.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-10. Approximate location of ASR wells. SOURCE: Information on locations of existing and proposed storage components from USACE and SFWMD.

age capacity of the Restoration Plan. A more extensive discussion of this technology is included in previous committee reports (NRC 2001a, 2002a).

ASR was initially explored as a storage option because it appeared to offer several advantages relative to surface storage and because initial cost estimates indicated that it would be less expensive than constructing additional surface reservoirs (Appendix A of USACE and SFWMD, 1999). Because ASR does not require large amounts of land, it would not displace other activities, such as agriculture, nor would it occupy large areas of land that could become part of the restored footprint. Because the water is stored underground, losses to evaporation will not decrease the volume of stored water, as would be the case for surface reservoirs. In principle, because of the lack of evaporation and because the available subsurface storage zone is effectively unlimited in size, ASR can allow for continuous storage with opportunities to add more water over a number of years.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

A disadvantage of ASR, relative to surface storage, is that it is a highly engineered storage technology, with significant long-term energy requirements for injecting and recovering water from the subsurface. In addition, well and pump maintenance for a distributed system of hundreds of wells is necessary. The water may require pre-injection or post-recovery treatment to meet regulatory standards or environmental requirements. Perhaps the greatest potential disadvantage stems from uncertainties associated with feasibility of the technology. In the current plan, the regional ASR systems have been planned using an anticipated injection rate of 5 MGD per well; whether this injection rate can be achieved consistently remains to be tested during pilot studies. During the initial phases of the Restudy, when cost comparisons to surface storage were used to select ASR, the wells were assumed to have a 10 MGD injection capacity. If, in the end, the average capacity of ASR wells is 5 MGD (or less), cost comparisons to surface storage would likely be less favorable.

Although ASR will not be subject to evaporative losses, it probably will not be possible to recover a volume equal to that injected. Mixing of injected water with more saline ambient aquifer water during storage (Figure 2-9b, d) or replacement of injected water by advective transport of aquifer water (Figure 2-9c) could render some of the injected water inaccessible to recovery. Even in the absence of significant aquifer flow, water-quality changes, induced by mixing with ambient brackish water or as a result of subsurface geochemical and biogeochemical reactions (Figure 2-9d), could limit the amount of stored water that is suitable for recovery and release to the ecosystem. The Restoration Plan design assumes a recovery efficiency of 70 percent (30 percent loss during injection), which may be an overestimate or underestimate.

Land-acquisition costs for the ASR systems, estimated in the Restoration Plan at approximately $231 million, are considerably lower than the $800 million estimated for the surface reservoirs described previously. In contrast, estimated annual operation and maintenance costs for the ASR systems exceed $36 million, while those for surface reservoirs total approximately $25 million. Furthermore, ASR operation and maintenance costs are highly uncertain due to uncertainties in future energy prices.

Several pilot studies are under way (ASR Regional Study, Hillsboro and Lake Okeechobee ASR Pilot projects) to address the uncertainties associated with ASR feasibility, recovery efficiency, and water quality changes. The time required to conduct these pilot studies (5-10 years) is a major constraint on sequencing of ASR within the Restoration Plan construction schedule. In the original implementation schedule, completion of the Lake Okeechobee Regional ASR system is not expected before 2026. The other, smaller ASR systems have scheduled completion dates ranging from 2017 to 2020.

The pilot studies might confirm that ASR has the potential to provide (or exceed) the storage capacity assumed for this technology in the design of the Restoration Plan. However, if the pilot studies indicate that ASR cannot provide the anticipated storage capacity, other sources of storage will likely need to be identified. Given the uncertainties associated with this technology, contingency planning prior to completion of the pilot studies is essential to limit further delays should the pilot studies yield unfavorable results. Recognizing this need, the USACE and SFWMD are working on an ASR contingency study.

Water-Quality Considerations

As is the case for all storage components, capture of water that currently flows to the sea and storing it in an ASR system would reduce damaging pulses of freshwater entering estuaries.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

If the water can be recovered efficiently and if it is of suitable quality, the release of the stored water to the ecosystem during dry years would help to maintain critical water levels and flows in the southern Everglades. Use of ASR as an alternative to storage in Lake Okeechobee or the Water Conservation Areas would reduce environmental damages associated with extreme water level fluctuations in the existing storage features.

As for negative effects of ASR, a primary concern is potential damage to the ecosystem associated with the quality of the water recovered from ASR wells. As noted above, the injected water may experience changes in chemical composition as a result of mixing or subsurface geochemical and biogeochemical reactions. Although moderate changes in such characteristics as pH, hardness, or salinity might have no consequence for the suitability of the recovered water for human water supply, ecosystems might be quite sensitive to these changes. For example, an expanding coverage of calcareous periphyton in the Everglades has been attributed to introduction of CaCO3-rich water via canals that are in contact with mineralized groundwater (Browder et al., 1994). In addition, changes in concentrations of dissolved constituents such as sulfate may influence the speciation and bioavailability of contaminants such as mercury.

Another water-quality concern is the chemical and microbial contamination of the aquifer by low-quality surface water. This issue could be resolved by requiring pre-treatment of surface water, including disinfection, before it is pumped into the aquifer, and legal requirements regarding the microbiological quality of water recharged to ground-water aquifers may necessitate this strategy. However, pre-treatment likely would increase the costs of ASR dramatically, and it also could cause other problems, including the formation of potentially toxic disinfection by-products from reaction of chlorine (a likely disinfectant) with natural organic matter occurring in the recharge water (Krasner et al., 1989). Surface waters in the areas where ASR is proposed tend to be high in natural organic matter, promoting the formation of disinfection by-products and also tending to make pre-treatment a more costly and difficult proposition.

Degradation of water quality during storage in the aquifer as a result of reactions between the water and mineral solid-phases could lead to elevated concentrations of radionuclides, which are naturally abundant in the aquifer minerals, and possible increases in certain trace heavy metals. Other water-quality issues associated with ASR were discussed in greater detail in a previous report by this committee (NRC, 2001a).

An additional concern is the potential that the increased pressure in the storage zone of the Floridan Aquifer resulting from injection could induce fracturing of the overlying Hawthorn confining unit, providing a pathway for brackish ambient water or the stored water to migrate upwards into the overlying freshwater aquifer. Finally, the cumulative effect of a large-scale injection and recovery operations could alter ambient flow in the Floridan Aquifer over a larger region than that covered by the ASR wells. Changes to regional flow patterns could have consequences in locations where the Floridan Aquifer contains fresh water and is used for water supply.

The ASR Regional Study is intended to address questions related to each of these potential impacts of ASR implementation. Depending on the outcomes of this pilot study, as well as on issues related to regulatory compliance, pre-injection or post-injection treatment of the water may be required.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

In-Ground Reservoirs

Two in-ground reservoirs constructed in former quarries are planned for the Lake Belt area of Miami-Dade County. A third smaller, shallower in-ground reservoir also is planned for western Palm Beach County near the L-8 canal. The following discussion focuses on the proposed reservoirs in the Lake Belt, but similar construction concerns may apply to the L-8 reservoir as well.

After mining companies have quarried 1.7 billion tons of limerock over a 30+ year period, surface reservoirs extending to depths of approximately 80 feet are planned in the Lake Belt rock mining area of Miami-Dade County, west of the City of Miami (Figures 2-1, 2-11, 2-12). Two quarries with a total surface area of 9,700 acres and a total storage capacity of 280,000 acre-feet are anticipated to accommodate inflows averaging approximately 250,000 acre-feet annually.

The reservoirs will occupy 9,700 acres of land in a region that is currently undeveloped and could, in theory, be part of the land acquired for restoration. However, these areas are within a footprint for which mining companies already have requested permits to excavate, and they are likely to be mined whether or not the quarries are eventually converted into storage reservoirs. To convert the quarries at the end of active mining into reservoirs that can store water for use as a supply to the Everglades during dry weather periods, seepage barriers must be created to limit the infiltration of groundwater from the surrounding aquifer and to hold the stored water within the reservoirs. (Indeed, the quarries are currently filled with water from groundwater infiltration during the mining period.) The technology required to create these seepage barriers at the required scale in permeable limestone has not yet been developed or tested, and hence both costs and feasibility associated with this storage component are uncertain. As in the case of any surface reservoir, water will be lost to evaporation from the free surface. However, the net evaporative losses will not exceed evaporative losses that would occur from standing water in a quarry lake of equivalent size that was filled with water that had infiltrated from the surrounding aquifer. In other words, replacing a quarry lake with a quarry reservoir will have no net effect on evaporative losses from the system as a whole.

Timing of construction of the Lake Belt reservoirs is constrained by a number of factors. First, the pilot studies to assess costs and feasibility of technologies for creating seepage barriers must be completed, and in turn, these require completion of excavation at the quarries to be used in the pilot studies. The pilot-project management plan indicates that the pilot project will not be completed until after 2010 (USACE and SFWMD, 2002b). Following selection of final sites and sizes of the reservoirs, mining activities may take a decade or more before the quarries will be available for water storage, resulting in an estimated date of 2036 for completion of the final phases of construction. There also are questions about whether the selected seepage technology will be able to withstand blasting occurring in nearby, active quarries (USACE and SFWMD, 2002b). If the technology is sensitive to blasting effects, construction could be further delayed until mining is completed at other quarries in the vicinity.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-11. Approximate location of Lake Belt storage. SOURCE: Information on locations of existing and proposed storage components from USACE and SFWMD.

Although development of the Lake Belt reservoirs involves loss of wetland or other habitat in an area adjacent to the restoration footprint, this land likely would be lost to the restoration in any case (based on current land-use plans for the Lake Belt region). While the reservoirs will not displace agricultural activities or urban development, the estimated land costs totaling over $255 million provided in the plan suggest that land costs per acre for these reservoirs will exceed those for the conventional reservoirs in the Kissimmee Basin and the EAA. In addition, construction costs associated with creating the seepage barriers will be high. The estimated construction costs of $783 million far exceed the total construction costs for the conventional surface-water reservoirs. Depending on the long-term integrity of the seepage barriers, there may be additional

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

maintenance and repair costs to consider as well. Operational costs in terms of pumping and distribution should be similar to those of other surface reservoirs.

Water-Quality Considerations

Water quality of the stormwater runoff used to supply Lake Belt reservoirs will depend on land uses in the drainage areas from which the runoff is derived. The Northern Lake Belt reservoir will receive local basin runoff and, ultimately, some water recovered from WCA 3A/3B seepage-management efforts. The Central Lake Belt reservoirs are intended to store excess water from WCAs 2 and 3, routed to the reservoirs via improved L-37 and L-33 borrow canals. Most local basins likely will be in urban/suburban land use, but some lands used for intensive agriculture also may contribute runoff. Consequently, some water supplying these reservoirs is likely to be contaminated with constituents usually associated with these land uses: elevated nutrients (nitrogen and phosphorus) and oxygen-demanding biodegradable natural organic matter; suspended solids; potentially pathogenic microorganisms of animal and possibly human origin; a variety of heavy metals, including zinc, cadmium, and lead; and low levels of a wide variety of synthetic organic contaminants (e.g., herbicides, pesticides, and polycyclic aromatic hydrocarbons) used on urban landscapes or formed in urban environments.

Certain characteristics of the reservoirs may lead to improvements in the quality of the water stored there for extended periods. The morphometry of the reservoirs—steeply sloping sides, small littoral zones, and large mean and maximum depths—should promote settling of suspended material and minimize resuspension of bottom sediments by wind-induced mixing. If annual nutrient loading rates are not too high and water residence times are fairly long, nutrients will be assimilated by algae and conveyed to the bottom by natural settling processes, such that the reservoirs may have moderately high water clarity and relatively low chlorophyll levels, making them suitable for certain kinds of aquatic-based recreational activities.

On the other hand, reservoir morphometry also is likely to promote strong thermal stratification in the water column that may persist for long periods (possibly several years). This will lead to highly anoxic conditions in the stagnant hypolimnion (cooler bottom layer of water), which is likely to comprise a large fraction of the total volume of Lake Belt reservoirs, and to the build-up of undesirable constituents, including sulfide, ammonia, methane, dissolved iron, and manganese. This will cause a large fraction of the stored water to be unsuitable for municipal water supply—or at least render it much more difficult and expensive to treat. In addition, such water would violate state water-quality standards for direct release into surface drainage canals in the Everglades drainage network, although it could be made to meet state standards by treatment involving aeration before release. Alternatively, it may be desirable to maintain oxygenated conditions throughout the water column of Lake Belt reservoirs by installing aeration devices in the reservoirs. Although such devices are technically feasible, they would be costly to operate and maintain, given the size and depths of the reservoirs (and the volumes of water that would need to be aerated).

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-12. Map showing the location of the proposed Central and North Lake Belt Storage Areas, L-31N Seepage Management, and the West Miami-Dade Wastewater Reuse Facility. Water Conservation Areas 3A and 3B Levee Seepage Management would be located just north of this map and the proposed reuse facility associated with the Miami-Dade South Wastewater Treatment Plant about 15 miles to the south.

SOURCE: Available online at http://sflwww.er.usgs.gov/publications/ofr/02-325/introduction.html.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

The major ion composition of the lakes also could be an issue. Constructed in a limestone stratum, the lakes will have hard water (high in calcium, magnesium and bicarbonate alkalinity). Although these constituents are desirable from many perspectives, they have the potential to substantially increase the hardness and ionic strength of water flowing through the southern Everglades, a system driven primarily by rainfall chemistry and thus historically a soft-water environment. The flora and possibly associated fauna of this part of the Everglades are adapted to soft water, and major shifts in plant community composition could result from use of the Lake Belt to supplement water flows to the Everglades during periods of low rainfall.

Finally, water-quality concerns regarding the Lake Belt reservoirs include the potential for contamination of the shallow Biscayne Aquifer, which is used for drinking-water supply. This potential depends on the source and level of pre-storage treatment applied to water that will be added to the reservoirs, as well as on the hydraulic connection that remains between the reservoirs and the aquifer once seepage barriers have been constructed. The Lake Belt Pilot Project includes a water-quality evaluation to address these concerns.

Changes in the groundwater flow field associated with reservoir construction and operation could also affect operations at municipal well-fields near the Lake Belt. The pilot project includes a regional hydrologic evaluation to evaluate these potential impacts.

Seepage Management

Differences in hydraulic head across levees that bound the Water Conservation Areas and Everglades National Park result in significant seepage losses to the east, toward the coast through adjacent canals. For the overall Everglades system, the Governor’s Commission for a Sustainable South Florida (1997) estimated seepage losses at over one million acre-feet per year, a significant amount in relation to other components of the Restoration Plan. Seepage management reduces the losses or recovers this water and returns it to the Everglades as a water conservation measure. Two locations are planned for this Restoration Plan component:

  • Everglades National Park Seepage Management. The purpose of this project (Figure 2-12) is to improve water deliveries to Northeast Shark River Slough and restore wetland hydropatterns in Everglades National Park by reducing levee and groundwater seepage and increasing sheet flow. This will be accomplished by a levee cutoff wall along levee L-31N, south of the Tamiami Trail, which reduces groundwater flows during the wet season and by capturing the groundwater with a series of wells adjacent to L-31N, then back-pumping those flows to Everglades National Park. This project is expected to conserve about 162,000 acre feet annually (J. Obeysekera, SFWMD, written communication, May 2004). This conserved volume, and the value for WCA 3A/3B below, is estimated from modeling the difference between seepage at these sites without the Restoration Plan (2050 Base) and with it (D13R).

  • Water Conservation Areas 3A and 3B Levee Seepage Management. The goal of this project is to reduce seepage loss from these WCAs in order to improve hydroperiods within the Conservation Areas by allowing higher water levels in the borrow canals and longer inundation within the marsh areas that are located east of the WCAs and west of US Highway 27. New levees will be constructed west of US Highway 27 from the North New River Canal to the Miami (C-6) Canal to separate seepage water from the urban

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

runoff in the C-11 diversion canal. Higher-quality seepage from the WCAs and marshes will be collected and returned to the Water Conservation Areas via features associated with the C-11 Impoundment project or stored in either the C-9 or C-11 Impoundment. Collected seepage water will further be transported by canal to the Central Lake Belt, for distribution to Everglades National Park (S. Applebaum, personal communication, January 2005). The Western C-11 Diversion Impoundment and Canal will capture lower-quality water from urban runoff and agricultural areas that is presently back-pumped into WCA 3A through the S-9 pump station and discharge it either into the North Lake Belt Storage Area (once it is on line), C-9 Impoundment, or WCA 3A after treatment (USACE and SFWMD, 1999, p. 9-19). This project is expected to conserve about 129,000 ac-ft annually (J. Obeysekera, SFWMD, written communication, May 2004). The S-9 pump station will also be used to divert excess water above WCA 3A/3B target depths to the Central Lake Belt Storage Area or Shark River Slough via the improved L-37 or L-33 borrow canals, respectively.

At the L-31N site, a pilot project will evaluate technologies to reduce levee seepage flow across L-31N adjacent to ENP via a levee cutoff wall (vertical subsurface barrier with a confining layer at its base) and to reduce groundwater flows during the wet season by capturing the groundwater with a series of wells adjacent to L-31N, then back-pumping those flows to ENP through the S-356 pump station (to be replaced by two new stations: S-356A and S-356B). Other technologies may also be explored, such as those reviewed and described in the Technical Advisory Report on Seepage Management (Governor’s Commission for a Sustainable South Florida, 1997).

Uncertainties about these techniques are similar to those for creation of barriers to flow for the Lake Belt quarries. The L-31N pilot project is expected to contribute to a refined design and better understanding of construction technologies upon its completion. This activity is especially important given the 100 percent effectiveness (recovery of seepage) assumed for this Restoration Plan component (USACE and SFWMD, 1999). The final seepage-management strategies developed must not only reduce the loss of water from the Everglades but also prevent significant downstream impacts to water supplies, flood control, and wetland and estuarine systems.

There is some urgency to initiate these projects because both are on the boundaries of the natural system, and adjacent land is threatened by urbanization. Using the November 2004 Draft Master Implementation Sequencing Plan (MISP, http://www.evergladesplan.org/pm/misp.cfm#docs) for estimates of “streamlined” completion dates and Figure M-1 from SFWMD and USACE (1999) for estimates of construction duration, the WCA 3A/3B project is scheduled to be completed in 2008 after about four years of construction, the Everglades National Park seepage-management project is scheduled to be completed in 2009 after about four years of construction, and the L-31N pilot project is scheduled to be completed in 2008 after about one year of construction (to which will be added an additional year of monitoring). Setbacks could occur if the cutoff wall technologies are unable to stem the loss of water through the levees.

The anticipated cost for the L-31N pilot project is about $10 million (USACE and SFWMD, 2002a). The overall Everglades National Park seepage-management project will be constructed in conjunction with modifications to structure S-356, for an overall construction cost of about $90 million. Similarly, the WCA 3A/3B seepage-management project will be constructed in conjunction with the canal C-11 diversion impoundment, for an overall projected con-

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

struction cost of about $58 million. Even though the SFWMD owns the levees themselves, total land requirements for the Everglades National Park and WCA 3A/3B projects are 3,900 acres and 5,887 acres, respectively, corresponding to estimated real-estate costs of $95 million and $168 million (Tables 9-1 and 9-2, USACE and SFWMD, 1999). (The current web site, 8/27/04, for the WCA 3A/3B project lowers the land requirement to 4,323 acres, with 2,970 acres currently acquired.) The L-31N Pilot Project will be constructed entirely on public land and not require any land acquisition.

The Everglades National Park seepage-management project involves back-pumping of recovered water into the park itself. Hence, there will be continuing operation and maintenance costs associated with this option compared to installation of the seepage barrier itself, which will be a one-time capital cost. The selection of seepage-management technology will include an evaluation of the trade-offs between higher capital costs (e.g., slurry walls, grout curtains) and higher operation and maintenance costs (e.g., back-pumping). Annual operation and maintenance costs estimated in the plan for this component approach $5 million.

Environmental Considerations

The proposed technologies to control seepage may have unintended consequences that must be investigated before full-scale implementation of the proposed project features; hence, the Everglades National Park project includes the L-31N pilot project intended to investigate seepage-management technologies. Possible unintended consequences to be investigated as part of this pilot project include negative impacts on the Miami-Dade West Well Field located just east of the project site; reduction of freshwater flows toward Biscayne Bay; and the potential to attract contaminated agricultural runoff due to the pumping component.

Furthermore, this project includes relocation of the Modified Water Deliveries structure S-357 to provide more effective water deliveries to Everglades National Park. New discharges to Everglades National Park must be designed to meet applicable water-quality criteria. The Everglades National Park project is also dependent upon modification to S-356 structures to provide more effective water deliveries to the Park.

Water Reuse and Conservation

Treated wastewater from the Miami-Dade South Wastewater Treatment Plant currently is pumped over 2,000 ft deep into the “boulder zone” of the Floridan Aquifer. The Wastewater Reuse Technology Pilot Project for West and South Miami-Dade envisions two wastewater reuse facilities to increase the quantity of water available for ecological restoration. One facility would be associated with the existing Miami-Dade South treatment facility at the southern end of Biscayne Bay, and the other would be associated with a proposed wastewater treatment plant in the west Miami-Dade area near Bird Drive (Figure 2-12). Ultimately, reclaimed wastewater from the two plants is anticipated to provide an average of 230 MGD (258,000 ac-ft/yr) and maximum of 231 MGD (259,000 ac-ft/yr) (USACE and SFWMD, 1999, pp. 9-23 and 9-24; M. Irizarry, SFWMD, personal communication, November 2004) for restoration. The 131 MGD (147,000 ac-ft/yr) South Miami-Dade reclaimed wastewaters will be used primarily to augment freshwater flows to south Biscayne Bay that might otherwise be lost through restoration efforts closer to and within the Everglades. South Miami-Dade reclaimed flows are estimated to be 74,000 ac-ft/yr

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

directed south toward C-102 and 73,000 ac-ft/yr directed north to C-100 (USACE and SFWMD, 1999, p. A4-43). The 100 MGD (112,000 ac-ft/yr) West Miami-Dade reclaimed wastewaters will be used to elevate water levels in the Bird Drive Basin and thus reduce seepage losses from Everglades National Park buffer areas and enhance water supply for groundwater recharge, South Dade conveyance system demands, and northeast Shark River Slough demands.

Other conservation efforts applied to water use (e.g., reduction of per capita potable water requirements) have not been factored into the plan explicitly. Rather, different future potable water-use requirements in 2050 range from 1,200 to 1,450 MGD (1.344 million to 1.769 million ac-ft/yr) reflecting greater or lesser conservation practices. These estimates are reflected in the background planning for the Restoration Plan (USACE and SFWMD, 1999). Overall, water conservation is expected to yield about 63 MGD or about 71,000 ac-ft/yr (J. Obeysekera, SFWMD, personal communication, May 2004).

Although the Restoration Plan anticipated that the reused water would be treated to a level needed to sustain estuarine and wetland biological communities in the Bay area, the technology that will be required to effect this treatment and the associated costs are not well established. The Technology Pilot Project at the existing South Miami-Dade treatment plant is designed to address these issues. The plan anticipates adding a pretreatment and membrane treatment system to the existing secondary treatment facility (CDM, 2004). The plant will have a capacity of 131 MGD. It is anticipated that phosphorus will be the primary constituent of concern in the reclaimed water. Therefore, the treatment will be designed to remove total phosphorus to acceptable levels. Evaluating whether this system will perform as anticipated is another reason for the Pilot Project. The dual-membrane technology to be used is relatively new (NRC, 1998), and although it has been applied at several locations (del Pino and Durham, 1999), performance and costs are uncertain.

The West Miami-Dade Wastewater Treatment Plant has not yet been constructed. Discharge of reclaimed water from this plant is planned for the Bird Drive Basin in western Miami-Dade County, east of Krome Avenue. In addition to the Miami-Dade facilities, the City of West Palm Beach is constructing a pilot facility to treat wastewater from the East Central Regional Wastewater Treatment Facility using advanced wastewater-treatment processes to remove nitrogen and phosphorus. After treatment, the wastewater will be used to restore 1500 acres of wetlands and to recharge wetlands surrounding West Palm Beach’s well field, as well as to recharge a nearby residential lake system. Results of this study will be used to evaluate the similar plan for distribution of reclaimed waters from the planned West Miami-Dade Plant. The assumption is that conditions will be similar at the two locations.

Advanced waste treatment is expensive both in capital costs and in operation and maintenance costs. Depending on the treatment technology used, anticipated capital and annual operation and maintenance costs are about $800 million and $84 million/year, respectively (Table 2-1; USACE and SFWMD [1999] Tables 9-2 and 9-3), making this one of the costlier components of the Restoration Plan. Indeed, costs for the 1 MGD South Miami-Dade pilot plant are estimated at about $8.9 million capital costs and $645,000/year O&M costs for the membrane technology that meets the low required effluent levels (described below) (CDM, 2004). Costs could increase or decrease by the 2013 target for completion of the pilot project, including four years of assessment (USACE and SFWMD, 2003). Decreasing costs are possible as a result of improvements in membrane and related technologies that may occur in the intervening decades before implementation of this Restoration Plan component (NRC, 2004c). However, large cost reductions

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

(i.e., >50 percent by 2020) will not likely be achieved through incremental improvements in existing technologies, but will require novel technologies.

The South Miami-Dade reclamation plan must wait on the outcome of its pilot project in 2013, and the West Miami-Dade plan must wait on the outcome of the West Palm Beach Pilot Project. In essence, the wastewater reclamation scheme already is a contingency plan, inasmuch as it will be implemented only in the likely event that more economical sources of water are not discovered during the courses of the pilot projects.

Water-Quality Considerations

Biscayne Bay was designated a priority water body by the Florida Legislature pursuant to the Surface Water Management and Improvement Act of 1987. The area south of Biscayne National Park is included in the Florida Keys National Marine Sanctuary. Waters of Biscayne Bay Aquatic Preserve and Biscayne National Park are classified as Outstanding Florida Waters (OFWs), and as such are subject to the most stringent regulations, including Florida antidegradation standards, which prohibit permitted discharges that will degrade ambient water quality. Because reclaimed water from the South Miami-Dade Waste Water Treatment Plant is considered “new” water (as opposed to surface runoff that might be diverted toward the bay), the plant discharge must meet the most stringent OFW criteria for the bay, even though plant discharge will reach the bay via discharge to the adjacent brackish wetlands, which are classified as State of Florida Class III waters. Because of these stringent regulations, the quality of reclaimed wastewater from the South Miami-Dade Plant is likely to substantially exceed the quality of ambient waters in the coastal marshes. The standards are compared in Table 2-4 (CDM, 2004) from which it is clear that the total nitrogen and total phosphorus standards for the Biscayne Bay OFW necessitate a very high level of treatment for the South Miami-Dade Waste Water Treatment Plant.

This highly conservative approach regarding effluent quality will result in correspondingly high treatment costs. In the recent study by Camp Dresser & McKee (2004), reverseosmosis membrane technology was the only one sufficient to meet the rigorous total nitrogen and total phosphorus OFW criteria. Capital costs for this scheme—for the 1 MGD pilot plant project—are estimated by CDM at $8.9/gallon; in contrast, 1993 capital costs for most wastewater reclamation were much less, in the range of $200-1,500 per acre-foot or about $0.00061-0.0046/gal (NRC, 1993), because of the much-less stringent water-quality requirements. High costs are recognized in the Restoration Plan, with the caveat that costly reclamation will be used only if “…other, more appropriate sources are not available…” (USACE and SFWMD, 1999). “Other sources” might consist of surface drainage that could be diverted toward Biscayne Bay that would not have to meet the OFW criteria, only the Class III criteria for the coastal wetlands. But if the reclaimed wastewater from the South Miami-Dade Waste Water Treatment Plant is not used to supply fresh water to Biscayne Bay, the (lower) cost of reclamation will not be funded by the Restoration Plan, creating other financial issues.

It is difficult to foresee a south Florida future in which the non-saline wastewater from a population of millions will not be required for at least a part of the water-supply needs of the region. Consideration should be given to revisiting or possibly appealing the decision to require the stringent total nitrogen and total phosphorus effluent standards for reclaimed wastewater that will first pass through brackish coastal wetlands before entering Biscayne Bay, in order to ensure the most responsible expenditure of Restoration Plan funds for wastewater reuse.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

TABLE 2-4 Comparison of Water Quality Criteria for South Miami-Dade WWTP

Variable

Raw Wastewater

1999-2004 SMDWWTPa Effluent

Reuseb

Class IIIc

Biscayne Bay OFW

Total Suspended Solids, mg/L

110

9.06

 

5

3.5

Biological Oxygen Demand 5, mg/L

110

 

5

5

12

Total Nitrogen, mg/L

40

18.4

 

3

0.27

Total Phosphorus, mg/L

 

1.09

 

1

0.005

Fecal Coliform, no./100 mL

 

55,385

2.2

2.2

2.2

a South Miami-Dade Waste Water Treatment Plant

b State of Florida standards for reuse of reclaimed water and land application (Chapter 62-610, FAC): meet at a minimum secondary treatment and the requirements for public access irrigation with a TSS concentration of 5.0 mg/L or less, and high level of disinfection.

c Chapter 62-611 FAC.

All values taken from CDM (2004).

SUMMARY AND COMPARISON

The conventional reservoirs, ASR systems, in-ground reservoirs, and stormwater treatment areas included in the Restoration Plan will provide a total of approximately 5.5 billion acre-feet of new storage, of which approximately 4 billion acre-feet can be attributed to ASR systems (assuming 30% injection loss). Values listed in Table 2-1 can be used to compare major storage features in terms of storage capacity, costs, and land requirements. The main storage components can also be compared on the basis of sequencing, potential water quality impacts, and the degree to which the technology is proven and requires active operation (Table 2-5). Of the new storage that will be created by the Restoration Plan, conventional storage reservoirs have clear advantages of using proven technology and of requiring less active operation than water reuse or ASR.

Overall, the sequencing of storage components makes sense considering questions related to engineering feasibility. The storage components that rely on proven technology, namely the surface reservoirs, are slated to be completed considerably earlier than those that require pilot projects, i.e., the ASR systems, the in-ground reservoirs, and seepage management using subsurface permeability barriers. In addition, most of the novel technologies are associated with potential water-quality impacts, which must be carefully evaluated prior to construction. However, because these latter components make up approximately 80 percent of the new storage provided by the Restoration Plan, the long lead time required for their evaluation and construction is a major constraint on the availability of water that could provide earlier environmental benefits.

Although Table 2-1 provides information on costs for each component, more informative cost comparisons might be those that include consideration of the water-storage benefits provided by the components. Several such comparisons are shown in Figure 2-13, 2-14, and 2-15. These figures are only illustrative of the kinds of comparisons that can be made; not all projects in each storage category were used due to incomplete information on costs, and results would vary somewhat with a more complete data set. In Figure 2-13, construction and land acquisition costs are normalized by average annual outflows during the 31-year simulation period for each type of component. This comparison indicates that ASR systems are the most costly to site and

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

TABLE 2-5 Comparison of Selected Storage Components in Terms of Sequencing, Water Quality and Technology Characteristics

STORAGE COMPONENT

Construction Complete

Water Quality Impacts

Proven Technology?

Passive/Active Operation

Lake Okeechobee

 

 

YES

Intermediate

Water Conservation Areas

 

 

YES

Relatively passive

Conventional Surface Reservoirs

 

 

YES

Intermediate

North Storage Reservoir (Kissimmee)

2013

+

 

EAA Reservoirs

2014

-

Upper East Coast Reservoirs+STAs+natural storage

2010

+

ASRs

 

-

NO

Very Active

Lake Okeechobee ASR

2026

 

C43 Basin

2018

C51 ASR (North Palm Beach II)

2020

West Palm Beach ASR (N Palm Beach II, L-8 ASR)

2020

Central Palm Beach Reservoir ASR

2019

Site 1 Impoundment ASR (Hillsboro)

2017

Lake Belt Reservoirs

 

0

NO

Intermediate

North Lake Belt

2036

 

 

 

Central Lake Belt

2036

 

 

 

Seepage Management

 

 

NO

 

WCA3A/3B Levee Seepage Mgmt

2008

+

 

Intermediate (some back-pumping)

C11 Reservoir (part of 3A/3B seepage)

 

L31-N Seepage Mgmt

2013

0

 

Passive

Water Reuse

 

+

YES

Very Active

West Miami-Dade Water Reuse

 

South Miami-Dade Water Reuse

 

Note: Water quality impact key: + likely no negative impact, 0 unknown, - unresolved concern.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

construct. A similar normalization of operation and maintenance costs, illustrated in Figure 2-14, indicates that waste-water reuse incurs the highest annual costs, followed by ASRs.

While ASR systems are the most expensive to site and build when compared on the basis of average annual outflow, they are probably the least expensive when compared on the basis of the maximum storage they can provide in a year, based on dividing the land and construction costs by the maximum difference between inflows and outflows in any year of the D13R simulations. This comparison is illustrated in Figure 2-15.

The issue of providing ecological benefits as soon as possible has not been considered in the committee’s analyses in this chapter. Some approaches to considering that important matter are discussed in the following chapters.

FIGURE 2-13. Construction plus land costs in 1999 dollars normalized by average annual acre-foot of outflow. Data taken from Table 2-1. The analyses represented in Figures 2-13, 2-14, and 2-15 are illustrative only. A fuller economic analysis might discount expenditures based on timing of costs and benefits, convert all costs (i.e., capital and O&M) to present value, and account for uncertainty. Conventional surface reservoirs are North Storage (Kissimmee) and EAA reservoirs only. ASRs represent C-51 (North Palm Beach II) and Lake Okeechobee ASR only. The graphs shown in Figures 2-13, 2-14, and 2-15 would change somewhat with more complete cost information.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×

FIGURE 2-14. Operation and maintenance costs in 1999 dollars normalized by average annual acre-foot of outflow. Data taken from Table 2-1.

FIGURE 2-15. Construction plus land costs in 1999 dollars normalized by maximum annual change in storage. Data taken from Table 2-1.

Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 22
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 23
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 24
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 25
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 26
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 36
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 38
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 40
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 41
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 43
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 44
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 45
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
Page 48
Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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Suggested Citation:"2 Major Storage Components." National Research Council. 2005. Re-Engineering Water Storage in the Everglades: Risks and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/11215.
×
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×
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×
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The Water Science and Technology Board and the Board on Environmental Studies and Toxicology have released the seventh and final report of the Committee on Restoration of the Greater Everglades Ecosystem, which provides consensus advice to the South Florida Ecosystem Restoration Task Force on various scientific and technical topics. Human settlements and flood-control structures have significantly reduced the Everglades, which once encompassed over three million acres of slow-moving water enriched by a diverse biota. To remedy the degradation of the Everglades, a comprehensive Everglades Restoration Plan was formulated in 1999 with the goal of restoring the original hydrologic conditions of its remaining natural ecosystem. A major feature of this plan is providing enough storage capacity to meet human needs while also providing the needs of the greater Everglades ecosystem. This report reviews and evaluates not only storage options included in the Restoration Plan but also other options not considered in the Plan. Along with providing hydrologic and ecological analyses of the size, location and functioning of water storage components, the report also discusses and makes recommendations on related critical factors, such as timing of land acquisition, intermediate states of restoration, and tradeoffs among competing goals and ecosystem objectives.

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