Summary

The Everglades, one of the world’s treasured ecosystems, once encompassed about 3 million acres of slow-moving water, which supported an array of wetland and estuarine habitats from Lake Okeechobee in the north to the Florida Keys in the south. During the past century, the Everglades has been dramatically altered by drainage and water management infrastructure to improve flood management, urban water supply, and agricultural production. The remnants of the original Everglades now compete for water with urban and agricultural interests and are impaired by contaminated runoff from these two sectors. The Comprehensive Everglades Restoration Plan (CERP), a joint effort launched by the state and federal governments in 2000, seeks to reverse the decline of the ecosystem. This multibillion-dollar plan was originally envisioned as a 30- to 40-year effort with 68 individual project components including water storage reservoirs, water quality treatment using constructed wetlands, seepage management, and removal of barriers to sheet flow (e.g., canals, levees). Collectively these CERP projects aim to achieve ecological restoration by reestablishing the natural hydrologic characteristics of the Everglades—quality, quantity, timing, distribution, and flow—where feasible, and creating a water system that serves the needs of both the natural and the human systems of South Florida.

The National Academies of Sciences, Engineering, and Medicine established the Committee on Independent Scientific Review of Everglades Restoration Progress in 2004 in response to a request from the U.S. Army Corps of Engineers (USACE), with support from the South Florida Water Management District (SFWMD) and the U.S. Department of the Interior, based on Congress’s mandate in the Water Resources Development Act of 2000. The committee is charged to submit biennial reports that review the CERP’s progress in restoring the natural ecosystem. This is the committee’s ninth report. Each report provides an update on progress toward natural system restoration during the previous 2 years, describes substantive accomplishments, and reviews developments in research, monitor-

ing, and assessment that inform restoration decision making. The committee also identifies issues for in-depth evaluation stemming from new CERP program developments, policy initiatives, or improvements in scientific knowledge that have implications for restoration progress (see Chapter 1 for the committee’s full statement of task). For the 2022 report, the committee reviewed water quality progress for the stormwater treatment areas (STAs) and its importance to CERP progress and the consideration of climate change in CERP planning.

CERP implementation is occurring at a remarkable pace (Figure S-1), thanks to record funding levels. Large-scale restoration of the natural system is now under way, with the Combined Operational Plan increasing flows to the central Everglades through a suite of recently completed CERP and non-CERP projects and through ongoing restoration in Picayune Strand. Both efforts employ intensive project monitoring to track progress and learn from the monitoring results. This accelerated progress has illuminated two challenges that deserve additional attention moving forward—water quality and climate change. Fortunately, many opportunities exist to leverage scientific expertise to address these challenges without slowing the pace of restoration and to enhance the science support for decision making. Through a renewed initiative to develop a multiagency science plan, the Everglades science enterprise can ensure that the needed tools, research, analysis, and synthesis are available to support these and other critical restoration management decisions.

RESTORATION PROGRESS

In Chapter 3, the committee outlines the major accomplishments of restoration, with an emphasis on natural system restoration progress from the CERP in the past 2 years, and discusses issues that may affect progress.

Record funding levels for Everglades restoration planning, implementation, and construction are further expediting restoration progress and expanding its geographic scope. In 2022, six CERP projects are under construction, one project and one major project component have been officially completed, and the new Lake Okeechobee Systems Operating Manual (LOSOM) was released. Several projects are nearing completion in the next 2-3 years. The Everglades restoration program is exhibiting impressive momentum with three additional CERP projects expected to begin construction in the next 2 years. This implementation progress places the restoration at a pivot point with increasing demands associated with project- and systemwide operation and adaptive management, as well as with planning and implementation of remaining projects. An ambitious proposed implementation schedule (the Integrated Delivery Schedule) is being realized, and the Central Everglades Planning Project (CEPP)—the key project in

the restoration of the central Everglades—continues to make impressively rapid implementation progress.

Hydrologic restoration progress and early vegetation response is evident over large areas of the central and western Everglades after implementation of recent CERP and non-CERP initiatives. The Combined Operational Plan, which utilizes seepage management and water conveyance infrastructure from two non-CERP foundation projects that were recently completed (Mod Waters, C-111 South Dade), is rehydrating Northeast Shark River Slough and appears to be facilitating increased flow into Everglades National Park. The rehydration of Northeast Shark River Slough in Everglades National Park represents the largest step yet toward restoring the hydrology and ecology of the central Everglades. Shifts in vegetation in marl prairies are an early indicator that the predicted restoration benefits of the Combined Operational Plan may be realized. During the past 2 years, plugging of canals at Picayune Strand (Figure S-1) has approximately doubled the area with full hydrologic restoration to approximately 13,500 acres. Monitoring wells in the fully hydrologically restored area show immediate increases in hydroperiod and typical water levels. Understory vegetation response is trending toward reference conditions, but tree canopy response has been slower, as expected. The benefits attributable to restoration efforts cannot be adequately distinguished from the effects of other factors, such as unusually wet or dry years, without the use of available modeling tools to analyze the effects of these various factors on project outcomes.

Current progress on implementation and record levels of funding increase the need for and importance of analyzing and synthesizing natural system responses. The long-term hydrological, ecological, and water quality trend data needed to assess restoration response are challenging to find, and analyses of these trends are inconsistent across projects. As noted in the committee’s past reports (NASEM, 2018, 2021), quantitative objectives and accompanying expectations of how and when they will be achieved by management actions are critical for adaptive management processes. Some projects invest substantial time and energy in data analysis, while other projects conduct only limited analysis and primarily report recent results, a situation that complicates evaluation of progress toward project objectives. Adaptive management of the partially implemented system requires quantitative objectives as well as resources and staffing to support the assessment of ecosystem response. In addition, as recommended by NASEM (2021), more sophisticated strategies that use modeling tools to compare observed results to model predictions of current conditions based on recent precipitation and climate data (termed “nowcasting”) would help managers understand project responses under a range of weather conditions and improve their capacity to adjust operations as needed.

Water quality is an ongoing concern that could potentially constrain progress on several fronts, including the Combined Operational Plan and the CEPP. Increased dry season flows are a specific objective for the CEPP, but new infrastructure and recent operational changes under the Combined Operational Plan that have facilitated higher dry season flows have also resulted in total phosphorus exceedances. Better understanding of the underlying processes is needed to assess whether additional steps can help to mitigate these impacts without adversely affecting the intended flow benefits. Resolving this issue may necessitate additional research into the ecological implications of increased phosphorus concentrations and loads amid flow restoration and the development of improved water quality modeling tools to analyze the potential consequences of various alternatives.

The final plans for LOSOM and the Lake Okeechobee Watershed Restoration Plan provide for substantially less storage than originally envisioned in the CERP, which highlights the importance of a CERP mid-course assessment (i.e., CERP Update). The new System Operating Manual for Lake Okeechobee generally retains upper lake stages similar to those of the prior Lake Okeechobee Regulation Schedule (LORS 2008), which lowered lake stages to reduce the risk of catastrophic failure of the Herbert Hoover Dike. Consequently, LOSOM poses a potential loss of up to 800,000 acre-feet (AF) of storage in the rainy season compared to the lake regulation schedule in place in 1999 when the CERP was planned. In addition, the final Lake Okeechobee Watershed Restoration Plan includes 55 aquifer storage and recovery (ASR) wells, compared to the 200 ASR wells and 250,000 AF of surface storage proposed in the original CERP. As recommended by NASEM (2016, 2018), a mid-course assessment of expected CERP outcomes that accounts for newly identified constraints in storage and incorporates the latest climate change science would inform future management decisions regarding restoration planning, funding, sequencing, and adaptive management.

The SFWMD has implemented a rigorous approach to address uncertainties associated with ASR in the Lake Okeechobee Watershed Restoration Plan. The SFWMD appointed an independent peer review panel to provide input in the development of the ASR Science Plan, which includes 26 studies through 2030. The panel will continue to meet annually to evaluate progress on the ASR Science Plan and will provide recommendations on additional studies needed or modifications to ongoing work. The committee commends the SFWMD for soliciting independent input, both in the development of the plan and on an ongoing basis, to enhance the effectiveness of the science investments.

The USACE should implement a process for periodic multi-stakeholder review of Lake Okeechobee operations relative to the objectives of LOSOM to build confidence that the flexibility of the new operational schedule is being used as designed and to support learning to enhance future decision making.

The final LOSOM regulation schedule is similar to the prior schedule in many ways, including the high and low water management bands. The key differences are found in the lack of specificity of management in the largest band, Zone D. This lack of specificity affords water managers flexibility to use recent data and near-term forecasts to optimize water management. At the same time, this new flexibility leaves other agencies and stakeholders uncertain about how tradeoffs in management objectives will be balanced in the future compared to the balance of outcomes projected by the models during the LOSOM development process. Efforts to routinely report the rationale for operational adjustments within Zone D could be valuable in keeping stakeholders abreast of water management activities. In addition, an annual or semi-annual multi-stakeholder meeting or workshop would enable periodic assessment of how well competing priorities were balanced, increasing understanding, supporting transparency, and identifying lessons learned in support of adaptive management.

STA WATER QUALITY AND CERP PROGRESS

Implementation and refinement of STAs over the past nearly three decades has resulted in marked reductions in phosphorus concentrations in outflow waters, particularly in STA-3/4, which currently meets the requirements codified in the water quality−based effluent limit (WQBEL).¹ A considerable volume of rigorous, peer-reviewed, and applicable science has been generated by the SFWMD, as well as its academic and consulting partners, that has helped inform the design and performance of STAs. However, as discussed in depth in Chapter 4, the extent of phosphorus removal varies across STAs, and some STA discharges remain far from target values. The state’s current efforts through Restoration Strategies and other actions are expected to continue to improve the function of the STAs, although meeting and sustaining the WQBEL requirements in all STAs starting in water year (WY) 2027 will be a significant challenge. Given the dependence of CERP progress on WQBEL attainment—particularly the timely delivery of full CEPP benefits—the committee offers the following recommendations and conclusions to support the state’s efforts to understand and improve the effectiveness of STAs.

To support and sustain WQBEL attainment, the SFWMD should implement a rigorous adaptive management framework that increases efforts in data collection, data analysis, modeling, and synthesis. Talented and experienced

___________________

¹ The Florida Department of Environmental Quality set a WQBEL for total phosphorus in STA discharge to not exceed 19 µg/L as an annual flow-weighted mean in any water year and 13 µg/L as an annual flow-weighted mean in more than 3 out of 5 water years on a rolling basis (FDEP, 2017a). This footnote and text in Chapters 3 and 4 were edited after prepublication release of the report to clarify responsibility for setting total phosphorus limits.

SFWMD scientists and engineers are working on the STAs, as evidenced by the phosphorus removal performance to date, and substantial research is under way through the Restoration Strategies Science Plan that should be useful to STA management. Nonetheless, the extent of phosphorus removal needed to meet and sustain the WQBEL will likely require even stronger science support for decision making, cell-by-cell monitoring, new modeling tools, detailed analysis of available data, and frequent feedback between science and management to support rapid, science-informed decision making and to reduce the likelihood of water quality impeding CERP progress.

A rigorous adaptive management program should include development of near-term milestones for each STA flow-way. The WQBEL sets clear quantitative targets to assess STA performance starting in WY 2027, but quantitative interim milestones over the next few years should also be developed based on the activities associated with Restoration Strategies and other STA remediation actions. These milestones would help communicate to managers the science-based expectations of STA function and recovery times in each flow-way and would provide a basis for further analysis and possible action if outcomes do not meet expectations, thereby supporting more nimble decision making. They would also increase transparency of restoration progress to the community interested in water treatment by STAs and Everglades restoration.

Additional monitoring, research, analysis, and modeling will provide insight on ways to optimize and sustain STA performance. Despite decades of research and lessons learned through STA operations, key gaps remain in the understanding of phosphorus mobility and removal processes within STAs and optimal strategies to manage STA hydrology, vegetation, and biogeochemical processes. Moreover, currently available tools are limited in their ability to forecast STA responses to management actions. The cumulative retention of phosphorus in soils threatens the long-term performance of the STAs. The committee identified several priority research needs:

• Cell-by-cell monitoring along with the development of cell-by-cell phosphorus budgets would help managers identify problem areas and focus additional efforts to better understand and address the mechanisms that drive elevated phosphorus conditions. These activities would identify cells that may be transitioning to conditions of phosphorus saturation.
• Additional analysis of nutrient dynamics (total phosphorus, phosphorus forms, total nitrogen, nitrogen forms and associated secondary elements) along STA flow-ways could illuminate strategies to more effectively manage phosphorus. Dissolved organic and particulate phosphorus can represent substantial fractions of total phosphorus concentrations in

STA outflows, but current management efforts are generally focused on total phosphorus rather than individual forms of phosphorus. The interplay between nitrogen and phosphorus and the significance of nitrogen-limiting conditions deserves additional attention in understanding factors that affect phosphorus removal efficiency.

• Field research in STA cells that appear to be approaching phosphorus saturation and thereby increased internal phosphorus load and that are experiencing reduced efficiencies could provide insight on the effect of soil phosphorus accumulation on the ability of STA cells to retain phosphorus, and the benefits and timing of cell refurbishment in maintaining the effective performance of STAs over the long term. Field research would also provide an opportunity to examine the best strategies for refurbishment and recovery.
• Application and continued refinement of STA biogeochemistry and hydrology models would enhance the understanding of STA function and inform maintenance and operations decisions.
• Additional field research on the effects of STA hydraulics, such as inflow and outflow velocities, hydroperiod, and hydraulic loading, on phosphorus discharge could inform future operations.

An independent, external STA science advisory committee would provide additional perspective and expertise to assist the SFWMD in evaluating water quality progress of Restoration Strategies relative to expectations for phosphorus removal and in identifying areas of concern and promising strategies. An external STA science advisory committee, analogous to the ASR independent peer review panel convened by the SFWMD, could meet annually to discuss progress toward the milestones and to provide additional expertise and advice to support WQBEL attainment. With a mix of specialists, including in biogeochemistry, regional water operations, and agricultural source control measures, this group could also advise on data collection, data analysis, research, modeling, and synthesis efforts that inform actionable management activities.

Although a variety of factors affect outflow phosphorus concentrations, phosphorus inflow concentrations and loading rates are key drivers affecting WQBEL attainment. The only STA (3/4) that consistently meets water quality conditions that approach the WQBEL has an annual phosphorus loading rate that is generally much lower than 1 g/m²-yr. In contrast, STA-1E, -1W, and -5/6 routinely have a phosphorus loading rate that exceeds 1 g/m²-yr, and in some years exceeds this rate by a factor of two or more. Recent average flow-weighted inflow concentrations for STA-3/4 were approximately 50 percent (or less) than the inflow concentrations of the three worst-performing STAs. Thus, for

some STAs the annual phosphorus loads and/or concentrations will likely need to be cut in half to achieve annual effluent total phosphorus concentrations that approach the WQBEL. Three approaches can be pursued to manage elevated phosphorus loading rates in a given STA: improve the phosphorus removal efficiency within the STA, increase the footprint (surface area) of the STA (as is under way in STA-1W), and/or decrease the upstream phosphorus loading entering the STA (source control). Restoration Strategies includes all three approaches in some capacity to reach the WQBEL, with most efforts devoted to improving phosphorus removal efficiency, but little progress has been made to reduce subregional phosphorus loads in the Eastern Flow Path. The concentrations of some STAs are so high that efficiencies beyond those of the best-performing STA would be needed to meet the WQBEL. In these cases, additional source control measures may ultimately be needed to meet the WQBEL.

RESTORATION IN THE CONTEXT OF CLIMATE CHANGE

The one near certainty regarding Florida climate change is that temperature and sea level will continue to rise. Increases in sea level will alter the salinity and habitats in coastal and near coastal regions, and increases in air temperature will drive increases in evapotranspiration and decreases in runoff, unless compensatory changes in precipitation occur. However, changes in precipitation and resulting discharge will remain uncertain and highly variable during CERP planning and implementation. Progress is under way to increase the rigor in which sea level–rise scenarios are considered in CERP project planning (e.g., coastal wetland and estuarine salinity changes), but analytical capabilities are limited by the tools presently available. In contrast, minimal progress is being made in the use of precipitation and temperature scenarios in project planning. No clear signal of the direction of change is not equivalent to an expectation of no change. In Chapter 5, the committee reviewed examples of how climate change is being incorporated into CERP planning and operations and offers the following conclusions and recommendations.

The USACE and the SFWMD should proactively develop scenarios of future precipitation and temperature change, including changes in variability, and a strategy to use them to inform future project planning decisions and ensure more reliable project performance. 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. Meaningful

consideration of climate for restoration decision making would include selection of appropriate performance measures and focused analysis and assessment of risk using multiple plausible scenarios of the future. The impacts of changes in interannual variability could be examined based on the historical record (e.g., by using a Monte Carlo approach), which would provide valuable insight into potential project performance. Exploring the effects of trends in air temperature and precipitation—individually, in combination, and with sea-level rise—during the planning process will help ensure that projects that perform reliably under future change move forward. If appropriate, additional data collection and further analysis can be conducted in preconstruction engineering and design.

Existing modeling tools, although effective for many CERP-related purposes, constrain the ability to improve planning to consider the effects of sea-level rise and other climate change impacts. Current models have limited flexibility to incorporate alternative climate futures, especially those that reflect increased variability and non-stationarity. Such limitations introduce risks into the project planning process because projects may not perform as anticipated. The USACE and the SFWMD should develop improved tools and analytical approaches that enable the examination of progressive change over time, rather than time slices of future conditions, to enable identification of environmental conditions when ecological thresholds are crossed. Examination of progressive change is especially important for the assessment of sea-level rise. Improved tools are needed to assess the project-related effects of various rates of sea-level rise and its interaction with hydrologic changes, and to examine sensitivity to the magnitude, frequency, and sequence of episodic events. In addition, hydrologic models should be able to readily accommodate a range of plausible future conditions that differ from historical conditions. Development of a modeling and analysis framework to plan for climate change in a system as complex as the Everglades will be a challenging endeavor but should be initiated as soon as possible to provide appropriate tools for future planning and evaluation efforts.

Inadequate consideration of water availability under future conditions and potential variations in the rate of sea-level rise could cause a project to move forward that is not viable under future climate change. The Biscayne Bay and Southeastern Everglades Ecosystem Restoration (BBSEER) planning process is a step in the right direction, especially in its novel consideration of resilience. However, it is constrained by the capacity of the models that support it. Climate change analysis should not be based on a single performance metric; rather, it should underlie all aspects of project planning, and all performance measures should be evaluated for outcomes under different climate conditions. BBSEER provides lessons to inform future CERP planning efforts. Planning should consider the effects of a range of plausible future conditions (precipitation and

air temperature) on freshwater availability, including, for example, extended droughts or wet years, to understand the vulnerability of project outcomes to climate change and to avoid delays and additional costs as the project moves forward. Furthermore, progressive change over time due to sea-level rise should be considered, rather than just time slices, so that potential tipping points in habitat change can be identified and project alternatives adjusted as needed.

Each revision of LOSOM and the System Operating Manuals should incorporate the latest information on climate change and variability to ensure anticipation of and planning for a wide range of conditions. Regular revisions to the System Operating Manual and other major operational plans, such as LOSOM or the Combined Operational Plan, provide an opportunity to incorporate 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, providing an incomplete view of their performance under potential future conditions. Efforts to update these operational manuals should identify data collection and information needs to ensure that the manuals reflect the current dynamics of the system and its variability.

Systemwide analysis of climate change on CERP performance is essential to assess the robustness of the restoration effort to possible futures and support program-level decision making. The work being conducted for the CERP Update provides a critical opportunity to examine the functionality of the system as a whole, but whether or how climate change analyses will be included in this work remains unclear. If not included as part of the CERP Update, additional analyses should be conducted outside of this process. These system-level climate change analyses will inform priorities for the remaining unplanned CERP projects and adjustments to system operations and will illuminate potential restoration actions that may be needed to enhance ecosystem resilience, either within or outside the CERP.

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. The USACE has progressively advanced guidance on the consideration of sea-level change in its activities, but the success of the CERP also relies on understanding the effects of other climate change impacts. To reduce future vulnerabilities, the committee urges

the USACE to develop guidance on the use of climate-affected hydrology data for civil works studies discussed in the USACE climate action plan, which was anticipated in 2021. This guidance is critical to support Action 1 of the USACE Climate Action Plan to “[e]nsure that new USACE-built projects are built to last and perform reliably for their intended design lives, despite uncertainty about future climatic conditions.” Providing the USACE Districts with the tools and guidance needed to effectively plan for future conditions is an urgent priority. The lack of guidance on the use of quantitative approaches to consider climate change and variability in hydrologic analyses fundamentally limits the potential success of CERP investments in ecosystem restoration.

THE CASE FOR AN EVERGLADES RESTORATION SCIENCE PLAN

As the CERP pivots from planning to implementation and adaptive management during a time of rapid global change, it requires support from a science enterprise with the collective capacity and ability to contribute financial resources, skills and expertise, and facilities and/or other resources to undertake scientific activities that respond to the critical knowledge impediments to restoration. In Chapter 6, the committee presents three essential, interlinked tasks of a science enterprise directed at the production of an Everglades Restoration Science Plan: (1) identification of knowledge gaps; (2) science coordination to advance and exchange knowledge; and (3) identification and establishment of focused science actions necessary to support progress. These tasks can be undertaken concurrent with ongoing work to advance restoration, with new science being incorporated into planning and implementation as it is developed.

Everglades restoration progress is inhibited by the lack of collectively identified science needs to support CERP decision making. There is no recent centralized compilation of critical management questions and associated knowledge gaps that could guide CERP science funding decisions or serve as a basis for proposal solicitations or collaborative initiatives. Instead, short-term demands command the attention of the available staff, and long-term, systems thinking is generally de-prioritized. Clearly identified science needs enable the science enterprise to stay focused, leading to more efficient utilization of science-provisioning resources and the presence of a critical linkage between management and science.

The Everglades science enterprise should develop a science plan to advance and implement essential science actions that directly support restoration decision making. This effort will require extensive multiagency and stakeholder coordination. This Everglades Restoration Science Plan could serve as a central document that highlights and communicates priority science needs and manage-

ment linkages to a broad audience of potential funders, much as the Integrated Delivery Schedule does for project implementation. The plan would guide the CERP program, other restoration initiatives, and individual funding agencies in their science investments for research, monitoring, modeling, and synthesis to meet agreed upon priority needs. The plan should be updated every 5 years and with the engagement of a diverse range of stakeholders to respond to changing needs, with annual implementation plans and progress reports to facilitate coordination and communication of progress toward addressing the science needs.

The Science Coordination Group is best positioned to lead an updated multiagency assessment of priority science needs and gaps at a programmatic level and to develop an Everglades Restoration Science Plan. This group should be clearly tasked to lead this effort and receive appropriate resources to do so from the South Florida Ecosystem Restoration Task Force. This effort would be a much-needed update to the 2008-2010 Plan for Coordinating Science. A lead scientist could guide implementation of the Science Plan, ensure completion of the work, and consult with decision makers to identify additional science needs to supplement plan activities (see also NASEM, 2018).

This page intentionally left blank.