Florida Water Storage South of Lake Okeechobee Plan Drawing
Managing High Water Levels in Florida'southward Largest Lake: Lake Okeechobee1
Summary
Lake Okeechobee is a big natural lake that is a primal feature in the south Florida regional ecosystem. Information technology now is encircled by a dike, and it has become the main surface h2o storage feature for water supply in south Florida and for the Comprehensive Everglades Restoration Program, or CERP. The CERP is a multi-billion dollar federal-state project to restore the Everglades and ensure the h2o supply for the growing man population of southeast Florida. The CERP too is intended to reduce harmful releases of fresh water from Lake Okeechobee to estuaries on the eastward and west coasts of Florida. The extent to which the CERP is successful in achieving its restoration goals depends in part on how much h2o can exist stored in Lake Okeechobee each rainy flavour for subsequent apply in hydrating the Everglades in the dry out season. The amount of water stored in Lake Okeechobee and how it is released also affects the ecological health of the lake and the due east and west coast estuaries that are connected to the lake by man-made canals.
To ensure that water levels in Lake Okeechobee exercise not weaken the Herbert Hoover Dike—the levee that near completely surrounds the lake and that is the lake'southward main flood protection mechanism—the United states Army Corps of Engineers (henceforth "the Corps") follows a regulation schedule, a fix of rules stipulating when water must be released from the lake at a given fourth dimension of the yr and how much water to release each time. More water is released just before the summer rainy season, and less is released going into the winter dry out flavor.
Regulation schedules are not perfect, and sometimes they cause controversy. In the case of Lake Okeechobee, the major controversy is well-nigh releases of lake water into the St. Lucie and Caloosahatchee estuaries to foreclose failure of the Herbert Hoover Dike. Large amounts of fresh water as well as harmful nutrients are transported from the lake to the estuaries during those flood-control releases. This can crusade harm to the estuaries, which rely on a frail combination of salt and fresh water to stay good for you, and which tin can develop baneful blooms of algae when food levels become loftier. All the same inundation h2o from the lake must exist sent to the estuaries because of major physical constraints in the mode the region's flood control organisation is built, every bit well as legal constraints to sending phosphorus-rich water due south to the Everglades.
This article provides a history of Lake Okeechobee regulation schedules and an overview of the risks, constraints, and merchandise-offs that the Corps must consider when deciding to release flood water from the lake.
The Historical Lake and Its Surroundings
Lake Okeechobee is a 730-square-mile natural lake located south of Orlando and well-nigh immediately west of Stuart. Historically, the lake was the major source of water to the Everglades. The lake and surrounding wetlands filled with water in the rainy flavour, and this water slowly flowed to the south, providing water to the Everglades in the dry out flavour.
Before Europeans settled in Florida near the plough of the xxthursday century, h2o flowed into the lake forth its northeastern shore from meandering rivers and wetlands and exited by numerous small creek channels to the southward and southeast toward Florida'southward west coast via a wetland and lake system that no longer exists. The lake'southward boundaries naturally fluctuated with the wet and dry out seasons (Figure i). After heavy rain events and large volumes of h2o inflow, lake levels sometimes rose to over 20 feet above sea level, spread out over the surrounding wetlands, and increased the size of the lake considerably. Outflows to the Everglades happened in a broad canvas menstruation at the southern end, into a vast wood of swimming apple trees, then into the Everglades sawgrass plains.
Credit: US Geological Survey
From Natural Lake to Reservoir
When European settlers came to Florida and developed towns and cities along the land's lower e declension, they viewed the Everglades as a useless swamp. A series of developers attempted to drain parts of it to make information technology suitable for human uses like agriculture. Many early attempts were failures, but somewhen much of the northern Everglades was tuckered by ditches that directed h2o flow due south and due east toward the bounding main. Developers besides synthetic a rudimentary earthen levee to concord back h2o at the south end of Lake Okeechobee. Nonetheless, catastrophic hurricane-related floods in the early and mid-1900s caused the lake to overflow its southern levee, drowning thousands of people and destroying communities and tremendous areas of agricultural land.
Portions of a more substantial dike system around the lake began to emerge in the 1930s to 1950s. Herbert Hoover spoke when the dike was named and dedicated in 1961. The Herbert Hoover Dike completely encircles the lake except for a portion on the west side where a large wetland from Fisheating Creek flows into the lake. In addition to the dike, the Corps constructed a network of drainage canals that led to compartmentalization of the northern Everglades. The project also resulted in large canals from Lake Okeechobee to the east, connecting to the St. Lucie River and Estuary past a series of gates and locks, and to the west, connecting to the Caloosahatchee River and Estuary (Figures 2 and three). Smaller canals to the south were constructed mainly to provide water for agriculture and to convey water to the growing urban area along the lower east of the state. Once surrounded past a dike, the lake now functions equally a reservoir.
Credit: South Florida H2o Management District
Credit: Google Earth
Managing High Water
I major characteristic of the Lake Okeechobee reservoir is unusual—in years with heavy rain, the capacity for water to flow in profoundly exceeds the capacity for water to menstruum out. This creates a potentially dangerous situation. Further, the dike effectually Lake Okeechobee was constructed more often than not of soil, with concrete-reinforced structures placed only at the major canal outlets. Building a soil dike on the underlying basis was risky, peculiarly in areas where that basis was largely comprised of frail peat soil. Designers of the dike knew early that a large hurricane could create waves that might compromise the dike at high h2o levels.
In light of this risk, and because south Florida has singled-out rainy and dry seasons, the Corps developed a regulation schedule to manage Lake Okeechobee h2o levels. In the about general sense, this allows the lake to fill to higher levels simply before the winter dry out season to ensure adequate water supply for urban and agronomical uses. In jump, water is released to create as much space equally possible to concord water earlier the wet season brings summertime tropical storms.
At times lake levels still become dangerously high in the wet flavor, and the Corps must discharge h2o at a high book. Since the Herbert Hoover Dike was constructed, the largest discharges have gone to the St. Lucie and Caloosahatchee Rivers and ultimately to the St. Lucie and Caloosahatchee Estuaries.
The Lake Okeechobee regulation schedule has changed over time, both for the purpose of belongings more water for downstream human being uses and too to strike a balance that provides options for flood protection, water supply, and estuary health. The regulation schedule must also back up the wellness of a large wetland along the western shore of the reservoir that formed inside the dike after information technology was constructed.
Confounding the effects of water levels and discharges are the massive amounts of phosphorus that have accumulated in Lake Okeechobee from past inputs from agronomics located north of the lake. Phosphorus is an essential nutrient for crop and other constitute growth and as well fuels growth of algae and plants in lakes. Yet, when it reaches loftier levels information technology can stimulate harmful algae blooms and have other negative furnishings mentioned beneath.
Near of the agricultural phosphorus in Lake Okeechobee now resides in muddy sediments on the lesser of the deepest part of the lake. Wind routinely stirs up this mud and the associated phosphorus. As a result, the middle of the lake is commonly turbid and phosphorus-rich, and it sometimes has algae blooms. When water is discharged to the estuaries, information technology can carry high amounts of phosphorus and mayhap seed the St. Lucie Estuary with blooms. The phosphorus in the mid-lake sediments also can impairment the lake's own coastal zone.
When lake levels are low, less than xv feet above ocean level, the littoral zone has naturally low concentrations of phosphorus, much similar the Everglades, and it can support a various mosaic of plants including sawgrass, spike rush, and willow. These provide excellent habitat for many species of wading birds, more 30 species of fish, and the federally endangered snail kite.
Even so, having a mid-lake area that is highly polluted with phosphorus creates a run a risk for the pristine littoral zone habitat. If lake levels rising to the 16-pes range, water from mid-lake mixes with the littoral zone. The associated phosphorus causes cattails to invade the habitat of the same desirable plants. Dense cattail is non practiced habitat for birds and other animals, and once it takes over, it takes human intervention such every bit burning or herbicide to remove. A high lake level tin also cause harm to the littoral zone past assuasive moving ridge energy to tear up its shoreline and by flooding plants. If birds are nesting in the littoral zone and the lake quickly rises, their nests are destroyed. There have been years when most wading birds have experienced total nesting failure for this reason.
Credit: Karl Havens, UF/IFAS
When the h2o depth in Lake Okeechobee becomes dangerously high, there are constraints on where h2o tin be sent when information technology is discharged from the lake. Canals to the south are modest and mainly intended to send water for agricultural and urban uses. Their capacity for moving flood waters is limited. Furthermore, storage areas south of the lake, in item the Everglades Water Conservation Areas, ofttimes are total of water and cannot accept more from the lake. Those big areas of the old Everglades also are surrounded by levees that lie correct up confronting lower east coastal metropolitan areas. Filling these areas with too much water puts millions of people at risk from flooding. Some water tin make its way through the relatively small canals south of the lake and get all the way from Lake Okeechobee to the body of water, but this too cases harm from phosphorus pollution in places similar the Lake Worth Lagoon and Biscayne Bay.
The two options with greatest chapters to accept h2o from Lake Okeechobee are the St. Lucie and Caloosahatchee Rivers, which are fed from the modern-solar day lake by large, deep canals. The trade-off however, is that when loftier amounts of Okeechobee flood waters catamenia from these canals, salinity in the St. Lucie and Caloosahatchee Estuaries can drop to nearly zero, killing oysters and other organisms that need brackish h2o to survive. Inflow of food-rich and algae-laden water from the lake also has led to astringent blooms of toxic algae in the St. Lucie Estuary and even in the adjacent nearshore waters of the Atlantic Ocean.
In contempo decades, further constraints take been placed on the ability of agencies to send water south from Lake Okeechobee when h2o levels are high. The settlement of a federal lawsuit about phosphorus pollution of the Everglades at present strictly limits the amount of phosphorus-laden water that may exist discharged to the south, unless the discharged water is treated. Still, the capacity of stormwater handling areas to remove phosphorus is express by both size of treatment wetlands and the long residence time of water needed to take phosphorus downwardly to legally required levels. Further, if migratory birds are nesting inside h2o treatment areas, those areas may non exist able to accept on more water because the Migratory Bird Treaty act mostly does not allow flooding of migratory bird nests.
When lake levels are high, all of these risks, constraints, and trade-offs are taken into consideration each week when the Corps decides whether to hold water in the lake or release information technology. How volition a decision affect the dike integrity? How volition it affect the health of the littoral zone? How will information technology bear on the estuaries? Are oysters spawning in one of the estuaries only not in the other? This is all information that may in part guide where water is sent. Ultimately, the lake's regulation schedule mandates the amount of h2o to be released when lake levels ascent above a certain point at a particular time of the year. In general, when the regulation schedule requires large flood-control releases, there tend to be fewer risks and constraints when releasing the h2o to the eastward and west than when releasing information technology south.
A More Detailed Look at Lake Okeechobee Regulation Schedules
Several different regulation schedules have existed since the Herbert Hoover Dike was completed. The earliest schedules were controlled by the Everglades Drainage District, and they were focused on decision-making flood waters that endangered communities around the lake, as well every bit providing water for irrigation of crops due south of the lake. In 1951, the Corps implemented a formal regulation schedule with singled-out regulatory bands, which are lines on a schedule that ascertain maximally acceptable water levels at any particular time in the year. When h2o levels rise above a particular band, the Corps discharges h2o from the lake. The book of the discharges is greater if water levels rise above higher bands in the regulation schedule. The Corps modified the lake regulation schedule in 1954, 1958, 1965, 1972, and 1978. The refinements led to increasingly greater storage capacity and water levels in the lake, and were responses to shortfalls in the amount of water that was available for a growing agriculture industry, especially due south of the lake.
After several years had passed, an evaluation of the 1978 regulation schedule by the Corps, the South Florida H2o Management District, and the United states of america Environmental Protection Agency concluded that the very high dry-flavour water levels allowed by the schedule were overly protective of water-supply demands. The high h2o levels in the dry season were causing big, damaging releases of fresh water to the St. Lucie and Caloosahatchee Estuaries and flooding habitat for plants and birds and other animals in the littoral zone of Lake Okeechobee. Post-obit a federal environmental bear on study (EIS), a new regulation schedule chosen Run 25 was adopted, with the goal of reducing loftier-volume releases to the estuaries while yet meeting requirements of water users. This new schedule was not sufficient to assist the lake, and harm from deep flooding continued to occur in the coastal zone.
In 2000, another EIS prompted the Corps to implement a new regulation schedule called Water Supply and Surroundings, or WSE. Its goal was to meet water supply demands, reduce harmful estuary discharges, and reduce the frequency of deep flooding to the littoral zone. This was attempted by incorporating, for the beginning fourth dimension, a proactive "determination tree" into lake operations. This meant that decisions about whether to agree or release water were made based on current h2o levels, every bit well as both short- and long-term outlooks of inflow volume. Short-term outlooks were based on whether the tributaries north of the lake were moisture or dry. Long-term outlooks were based on climate cycles that influence rainfall in s Florida, in detail the now familiar El Niño Southern Oscillation (ENSO) or another climate bicycle, the Atlantic Multi-Decadal Oscillation, or AMO. In an El Niño yr, the Pacific Jet Stream is displaced to the s and flows over the Gulf of Mexico, bringing more rainfall to southward Florida in winter. In its contrary phase, known as La Niña, that jet stream is farther north across the North American continent, resulting in less rainfall in the dry flavour. As much every bit 60 percent of the variation in wintertime rainfall over the due south Florida peninsula tin be predicted based on the stage of the El Niño cycle.
Too, a warm stage of the AMO climate cycle has historically resulted in greater summertime rainfall and up to twoscore percent more arrival to Lake Okeechobee than when the AMO is in a common cold stage. When the WSE operating schedule was in effect, the Corps used this data to be more aggressive about water releases when a potent El Niño was developing, particularly when coupled with a warm-phase AMO. The WSE schedule was more conservative about h2o releases when a potent La Niña was developing, particularly when coupled with a cold-phase AMO.
The implementation of the WSE was only mildly successful; the limitation of holding enough water remained a central problem. At the same time, structural repairs to the Herbert Hoover Dike continued to mount. In 2007, the Corps began more than $300 one thousand thousand worth of projects to reinforce the Herbert Hoover Dike that surrounds Lake Okeechobee because of overflowing risk and prophylactic concerns (Figure five). H2o had begun to seep through the mostly earthen dike following hurricanes and high lake levels in 1998, 2004, and 2005. When the dike rehabilitation project began, a concrete cut-off wall was installed inside the most risky areas of the dike, and water command structures effectually the lake where seepage was occurring were replaced. Work was initially planned to exist done in segments, starting with those determined from geotechnical studies to be at greatest risk of breach.
Credit: US Army Corps of Engineers
In 2013, after completing the construction of a cut-off wall in the highest-take a chance southern reach of the dike, the Corps began replacing 32 water-control structures around the lake considered to pose the side by side greatest risk of dike failure. Construction of the remaining cut-off walls then started again, and they are slated to exist done earlier 2025.
Because the underlying reason for dike rehabilitation was a loftier take a chance of structural failure, the Corps conducted an EIS and in 2008 adopted a new regulation schedule chosen the Lake Okeechobee Regulation Schedule 2008, or LORS 2008. The new regulation schedule is intended to concur the lake at what the Corps considers to be safe levels until dike rehabilitation is complete. As with all the old schedules described above, LORS 2008 has seasonally varying bands identifying highest water levels above which flood-control releases must occur. LORS 2008 also includes a benign employ band below the flood-control bands, where the SFWMD may recommend sending h2o out of the lake for beneficial uses. There are many kinds of beneficial uses of h2o in the dry out season. For example, a beneficial apply might exist a pulse of water sent to the Caloosahatchee River in the dry out season to prevent salt water from reaching the Ft. Myers drinking water intake. Other benign uses could be releasing water from the lake for irrigation of crops or sending water south to treatment areas where afterward removal of phosphorus it could be used to hydrate the Everglades.
LORS 2008 has many features that are like to WSE (Figure 6). Just like the flood-control bands in the WSE, releases of water from the lake in LORS 2008 are adamant based on rainfall outlook, the amount of water in tributaries, and multi-season climate outlooks. A major modify from WSE is the explicit objective of LORS 2008 to hold Lake Okeechobee at a lower level achieved in role by continual depression-volume releases to the estuaries.
Credit: South Florida Water Management District
More specifically, the objective of LORS 2008 is to "maintain a lake level between 12.5 and 15.5 feet," according to the Corps. This is achieved by managing h2o inside bands shown in Effigy half dozen, equally follows:
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High lake management ring—includes lake levels above 16 feet in accelerate of the moisture flavor or levels above 17.25 feet during the dry out season. Within this band, operations are focused on reducing the lake level and freeing up boosted capacity for runoff from future heavy rains. Maximum h2o releases occur when the lake is in this ring.
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Operational bands—these are five sub-bands that guide decisions to remainder the needs of all users while maintaining a lake level in the Corps' preferred range of 12.5 and 15.5 feet. Toward the lower end of the range, the Corps relies heavily on input from the SFWMD to aid with water allocations. In the upper bands, regulatory releases frequently are made to achieve the Corps' desired water levels.
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Water shortage management ring—this band includes lake levels below 10.5 feet in advance of the wet flavor or levels below 13 feet at the start of the dry out season. In this ring, the Corps typically defers decisions on water releases to the SFWMD.
Consequences of Belongings the Lake Lower and Time to come Options
The current LORS 2008 is 1.25 feet lower than Run 25 and WSE. This equates to, on average, more than 500,000 acre feet of lost storage capacity in the lake. Every bit a result, unless a new regulation schedule restores some or all of that chapters, there may exist bereft water stored in the regional ecosystem to provide all of the environmental and water-supply benefits expected to happen when CERP is complete. This is considering, as noted earlier, the lake is the main place in the regional system to concord water in the dry season and so arrive available for restoration due south of the lake in the dry out season. Options to make up for the lost lake storage include surface storage in other reservoirs beyond the chapters in the CERP plan, dispersed storage on land, or undercover storage. Or the bands could be raised in a new regulation schedule for Lake Okeechobee.
Storing More Water in the Lake
At this time, the Corps has not announced what, if anything, will exist done with the LORS 2008 regulation schedule once rehabilitation of the Herbert Hoover Dike is complete. The main reason for belongings the lake low nether LORS 2008—to protect a weakened dike—will no longer be. A contempo independent report by the Academy of Florida indicated that in order to meet the goals of CERP, which include providing h2o for Everglades restoration and coming together the water-supply demands of a growing population in the lower east coast of Florida, an additional 1.46 to 1.76 1000000 acre anxiety of storage is needed, across what the agencies plan to build in CERP. While a careful evaluation will be required to weigh pros and cons given the multiple features of the region (estuaries, littoral zone, water supply, Everglades), reverting to the prior WSE schedule would increment the lake's ability to shop more 500,000 acre feet of water. That is nearly a 3rd of the "missing" water needed for CERP to come across all of its originally intended restoration objectives.
The Corps volition need to conduct a new EIS if information technology attempts to modify LORS 2008. Perhaps when considered in the context of CERP project storage features, managers will exist able to identify a schedule that is less harmful to the lake and estuaries than WSE, and more beneficial for sending water south to the Everglades.
Farther Reading
Aumen, North.Thousand., and R.M. Wetzel. 1995. "Ecological studies on the littoral and pelagic systems of Lake Okeechobee, Florida (USA)." Archiv fur Hydrobiology, Advances in Limnology, 25, 356 pp.
Enfield, D.B., A.M. Mestas-Nuñez, and P.J. Trimble. 2001. "The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental US." Geophysical Research Letters 28: 2077–2080.
Havens, Grand.E., and D.Due east. Gawlik. 2005. "Lake Okeechobee conceptual ecological model." Wetlands 25: 908–925.
Havens, K.E., N.M. Aumen, R.T. James, and 5.H. Smith. 1996. "Rapid ecological changes in a large subtropical lake undergoing cultural eutrophication." Ambio 25: 150–155.
Johnson, K.G., M.S. Allen, and Grand.East. Havens. 2007. "A review of coastal vegetation, fisheries and wild fauna responses to hydrologic variation at Lake Okeechobee." Wetlands 27: 110–126.
NRC. 2015. Review of the Everglades aquifer storage and recovery regional study. National Research Council of the National Academies, Washington, DC, 57 pp.
SFWMD. 1988. Preliminary evaluation of the Lake Okeechobee regulation schedule. Southward Florida Water Management Commune, Due west Palm Beach, FL, 73 pp (plus appendices).
Steinman, A.D., K.E. Havens, H.J. Carrick, and R. Van Zee. 2002. "The by, nowadays and future hydrology and environmental of Lake Okeechobee and its watershed." Pp. 19–36 in Porter, J.W. and One thousand.G. Porter (eds.), The Florida Everglades, Florida Bay, and Coral Reefs of the Florida Keys: An Ecosystem Source book. CRC Printing, Boca Raton, FL.
Steinman, A.D., M.E. Havens, and L. Hornung. 2002. "The managed recession of Lake Okeechobee, Florida: integrating scientific discipline and natural resources management." Conservation Ecology 6: 17 [online] http://world wide web.consecol.org/vol6/iss2/art17.
Graham, W.D, M.J. Angelo, T.K. Frazer, P.C. Frederick, Thou.E. Havens, and K.R. Reddy. 2015. Options to reduce high volume freshwater flows to the St. Lucie and Caloosahatchee estuaries and movement more water due south from Lake Okeechobee to the southern Everglades. University of Florida, Gainesville, FL, 143 pp. https://www.flsenate.gov/UserContent/Topics/WLC/UF-WaterInstituteFinalReportMarch2015.pdf
USACE. 2007. Final supplemental environmental impact argument: Lake Okeechobee regulation schedule. US Army Corps of Engineers, Jacksonville District, FL, 821 pp.
USACE. 2012. Review programme for Herbert Hoover Dike design and construction phases Martin, Palm Beach, Hendry, Glades and Okeechobee Counties, Florida. The states Army Corps of Engineers, Jacksonville Commune, 12 pp (plus appendices).
USACE and SFWMD. 1999. Central and Southern Florida Project comprehensive review study final integrated feasibility study and programmatic environmental bear upon statement. United states of america Army Corps of Engineers and South Florida Water Direction District.
USACE and SFWMD. 2015. Central and Southern Florida Project Comprehensive Everglades Restoration Plan last technical data report aquifer storage and recovery regional study. U.s. Ground forces Corps of Engineers, Jacksonville District, and Due south Florida H2o Management Commune, 269 pp.
Wossenu, A., and P. Trimble. 2010. "El Niño southern oscillation link to south Florida hydrology and water direction applications." Water Resources Management 24: 4255–4271.
Source: https://edis.ifas.ufl.edu/publication/SG154
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