Progress Toward Restoring the Everglades The Ninth Biennial Review - 2022 (2023) / Chapter Skim
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5 Restoration in the Context of Climate Change
5 Restoration in the Context of Climate Change
Pages 171-210
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From page 171... ...
CLIMATE CHANGE IN SOUTH FLORIDA South Florida, a subtropical region surrounded by ocean with strong surface and deep water currents, is characterized by a distinct and highly variable climate regime. The climate is tropical and monsoonal, with variations manifested by large-scale phenomena (El Niño South Oscillation [ENSO]
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From page 172... ...
They also found large relative changes in air temperature extremes, with many more extreme hot temperatures and far fewer extreme cold temperatures in recent decades than would be expected based on 20th century data. For example, in the 1990s and 2000s, South Florida had twice the number of months with extreme hot temperatures (defined as >90 percent of the 20th century distri bution of temperature values)
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From page 173... ...
Future air temperature projections for two emission scenarios -- Representative Concentration Pathway (RCP) 4.5, the lower emission scenario, and RCP 8.5, the higher emission scenario -- suggest that temperature changes will continue to increase in South Florida through the 21st century (Figure 5-1)
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. Future projections of precipitation for South Florida are highly uncertain and do not capture the variability evident in observations.
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Restoration in the Context of Climate Change 175 FIGURE 5-3 Historical measurements and future projections of annual dry days (top) and the number of precipitation events per year in which precipitation exceeded 3 inches (7.6 cm; bottom)
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SOURCE: https://www2.usgs.gov/landresources/lcs/nccv/maca2/maca2_counties.html. Similar projections are available for evapotranspiration and runoff.2 Although future changes in precipitation are highly uncertain and projections of average annual precipitation currently appear relatively stable, it is quite certain that future climate will drive increases in rates of evapotranspiration due to pro jected increases in air temperature that will subsequently drive decreased runoff (Figure 5-4)
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) , each with projected increases in air temperature and evapotranspiration combined with projected future rainfall.
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Annotated measurements on right of figure are computed by subtracting the 5-year average mean sea levels for the years listed. The sea-level rise computed based on the linear trend will differ from the 5-year mean sea-level trend shown.
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FIGURE 5-7 Unified projections of sea-level rise for South Florida.
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for a review of climate change effects on South Florida e stuaries and their restoration goals. Understanding the potential effects of climate change and their relationships to CERP projects is necessary to ensure sound investments that enhance the resilience of the South Florida ecosystem.
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It provides options for how the scenarios should be used in USACE decision making, including the following: • When local conditions and plan performance are not considered highly sensitive to the rate of sea-level change, a single sea level−rise scenario could be used to develop and compare alternatives; the preferred alterna tive is then tested against other sea level−rise scenarios. • When local conditions and plan performance are deemed to be very sensitive to the rate of sea-level change, alternatives could be formulated and then evaluated under all sea level−change scenarios.
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However, it may be used by project partners, such as the South Florida Water Management District (SFWMD) , to understand potential vulnerabilities
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Restoration in the Context of Climate Change 183 FIGURE 5-8 USACE process for qualitative analysis of climate change impacts on inland hydrology. NOTES: CoP = Community of Practice, CPR = Climate Preparedness and Resiliency, HUC = hydrologic unit code, NWS = National Weather Service, PDT = project development team.
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emphasizes that the historical record provides a relatively limited sampling of the conditions that will be experienced in the future. It cannot be assumed that the future climate will be well represented by historical condi BOX 5-1 South Florida Water Management District Resiliency Planning The South Florida Water Management District (SFWMD)
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Simulations of plausible climate scenarios have been applied to water systems planning throughout the world and may be beneficial to CERP planning efforts. Several examples of successful approaches that could be highly appropriate for CERP project planning are described in Box 5-2.
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. Application of these methods in CERP planning would be straightforward in principle, notwithstanding the inevitable details of implementation in the exist ing suite of modeling tools.
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From page 187... ...
In this low-elevation coastal system, the BBSEER Project is on the front line of climate change effects. Because the project addresses coastal and near-shore issues and how they can be alleviated by increasing freshwater flows, it exemplifies the ways in which climate change effects on runoff and sea level can influence project performance.
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From page 188... ...
tion benefits. The committee has previously noted that ongoing climate change, including changes in precipitation patterns, sea-level rise, and ocean warming, challenge the ability of many CERP restoration efforts to meet the "essential hydrological and biological characteristics that defined the undisturbed South Florida ecosystem" (NASEM, 2016)
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In principle, increased freshwater flow to the area could promote restoration of peat accreting vegetation, thereby resisting transgression due to sea-level rise. The new Adaptive Foundational Resilience performance measure (F.
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From page 190... ...
restore freshwater depths, hydroperiods, and flows in terrestrial wetlands; and connect habitats from the sawgrass marsh through saltwater wetlands to open water across a 0-35 psu gradient.5 Many of the desired outcomes of the BBSEER Project depend upon increased freshwater flow (by volume) in the southern Everglades afforded by new storage and/or wastewater reuse.
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From page 191... ...
Biscayne and Southern Everglades Coastal Transport (BISECT) , which was developed to evaluate South Florida surface-water stages and 6 Following release of the prepublication report, this text was edited to provide an accurate description of the BBSM.
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From page 192... ...
192 Progress Toward Restoring the Everglades flows, groundwater levels, and salinity in response to changes in water- management practices and sea-level rise by combining two models: Tides and Inflows to the Mangrove Everglades (TIME) and the Flow and Transport in a Linked Overland/Aquifer Density Dependent System (FTLOADDS)
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for 2085. The FWO will capture the effect of a step increase in sea level without BBSEER but including authorized CERP projects, including the Central Everglades Planning Project (CEPP)
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Despite ongoing collaborative efforts between the SFWMD and Florida International University to develop new scenarios of precipitation under climate change to support restoration decision making, future precipitation scenarios will not be incorporated into the BBSEER analysis. The BBSEER modeling for the evaluation of project alternatives will be based on the prior climate record, which assumes that the historical time series of precipitation and air temperature provide an adequate set of conditions to fully test the robustness of the candi date plans to future climate conditions.
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. Such methods range from incrementally shifting the historical precipitation and air temperature time series to systematically explore plausible climate changes (e.g., +5 and +10 percent mean annual rainfall and +1, +2, +3°C mean annual temperature)
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Although the exact future conditions cannot be known, the potential for impacts can be explored. Rather than redesigning an entire planning process that is already under way, a near-term solution may be to conduct parallel exploratory analyses of some of these potential climate impacts using modeling tools available from the research community to assess the potential sensitivity of project outcomes to climate change factors, such as more variable rainfall and increasing air temperature and evapotranspiration.
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From page 197... ...
A dedicated focus on models that can more fully consider climate change effects, including the combined effects of climate stressors, will reduce the risks exemplified in the BBSEER planning discussed above and will ensure project planning can identify measures that will perform under an array of plausible future conditions. Such an initiative will take focused effort, time, financial support, and dedicated expertise.
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This was not a trivial task, and considerable effort was devoted to both the analyses and the synthesis of the results to better meet the competing demands of the South Florida ecosystem. LOSOM was evaluated in accordance with USACE climate guidance.
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For example, stakeholders throughout South Florida have expressed serious concerns about Lake Okeechobee operations. In the northern estuaries, excess releases from Lake Okeechobee result in high nutrient loads and changes in salinity, leading to losses in the shellfish and pinfish communities; loss of Vallisneria (Doering et al., 2002)
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. In the scenario with 1.5°C increase in air temperature and an associated increase in evapotranspiration with no difference in rainfall, surface elevations in Lake Okeechobee were projected to decrease to an elevation of 6.9 feet (2.1 m)
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base: a future condition that assumes no change in climatic conditions; (2) a future with an increase in air temperature of 1.5°C and associated evapotranspiration; (3)
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. Lake surface elevations of 12 feet (3.7 m)
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The System Operating Manual consists of seven volumes, organized according to geographical regions, that are designed to collectively provide a systemwide framework for the operation of components of the Central & Southern Florida Project and CERP projects to ensure that they function in a coordinated, systematic way. The Programmatic Regulations (33 CFR §385.3)
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This provision recognizes that changes can occur between project planning and operations of the final projects, because of changes not only in individual project features but also in other aspects of the system. Because CERP principles dictate the use of adaptive management based on the best available science, it is appropriate that the System Operating Manual be viewed as a vehicle to modify system operations based on evolving understanding of climate change and its effects to achieve CERP goals.
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The latter may be an especially useful way to incorporate new information on progressive change in the ecosystem due to climate change when there is an extended period between the end of project planning and project operation. Periodic revisions to the System Operating Manual will ensure that an updated climate record, reflecting recent records of climate variability and trends (which may differ from the patterns shown in longer-term records)
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From page 206... ...
Increases in sea level will alter the salinity and habitats in coastal and near coastal regions, and increases in air tempera 8 According to the Programmatic Regulations, "The periodic CERP updates will be accomplished by the Corps of Engineers and the South Florida Water Management District, in consultation with Tribes, Federal, State, and local agencies, to conduct an evaluation of the Plan using new or updated modeling that includes the latest scientific, technical, and planning information. The periodic CERP updates will provide a basis for determining if management actions are necessary to seek improvements in the Plan based upon new information resulting from changed or unforeseen circumstances, new scientific and technical information, new or updated modeling; information developed through the assessment principles contained in the Plan; and future authorized changes to the Plan." The periodic CERP updates will also "determine the total quantity of water that is expected to be generated by implementation of the Plan, including the quantity needed for the natural system and human environment."
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From page 207... ...
USACE project planning efforts seek to identify justifiable solutions to current problems that will ensure performance for the next 50 years at minimum, and USACE policy requires that restoration planning must meaningfully consider climate change trends and potentially increasing climate variability. Past CERP evaluations of climate change effects have been inconsistent and often limited to a step increase in sea-level rise.
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From page 208... ...
Regular revisions to the System Operating Manual and other major operational plans, such as LOSOM or the Combined Operational Plan, provide an opportunity to incor porate evolving understanding of climate variability and change into Everglades restoration. Several recent major operational planning efforts, such as LOSOM, have proceeded based on analysis of a prior 52-year climate record, with limited assessment of potential changes in future air temperature or precipitation, provid ing an incomplete view of their performance under potential future conditions.
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From page 209... ...
The lack of USACE guidance on the use of accepted information related to changes in precipitation and air temperature in quantitative analysis as part of project planning leads to future vulnerabilities to climate change and variability as CERP projects come on line. The science of global climate change is mature and rigorous, and many other water resources planning projects, in the United States and globally, routinely use climate change scenarios to examine project performance under a range of future conditions.
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