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1 Introduction The St. Johns River in central and northeast Florida is a 310-mile-long waterway that flows north from Indian River County to the Atlantic Ocean. The river and its floodplain comprise a broad, low-gradient system that transitions from dominance by freshwater wetlands in the headwaters near Vero Beach to dominance by a wide estuarine channel in its lower reaches near Jacksonville. The river is the longest in Florida, and drops only 30 feet from its headwaters to its mouth at the Atlantic Ocean. The lower 100 miles are subject to tidal influence. The St. Johns River Water Management District (SJRWMD or âthe Districtâ; see Figure 1-1) is responsible for managing water resources in the basin and its surroundingsâan area of 12,283 square miles, or 23 percent of Florida. The District must provide for water to meet the needs of human society and protect natural systems within the river basin. Each task is challenging in its own right, but together they require careful integration of many technological, scientific, social, economic, and environmental factors. There are approximately 4.4 million people (21 percent of Floridaâs population) living in the area served by the District and 110 municipalities, including the growing cities of Jacksonville, Orlando, and Gainesville. The District expects an increase in basin population from 3.5 million in 1995 to 7.2 million in 2030 (SJRWMD, 2009a). In order to meet the water supply needs of the Districtâs residents and its industrial and agricultural users (the total demand was 1.49 billion gallons per day in 2000), the District historically has relied on groundwater, with the upper Floridan aquifer as the primary source for public supply (SJRWMD, 2006). As a result of its ongoing water supply planning efforts, however, the District has determined that its useable groundwater supplies will reach their sustainable limits in the near future, prompting a search for alternative water supplies. Indeed, groundwater withdrawals in the Central Florida Coordination Area (CFCA) that lies in the southwest portion of the District, near Orlando, are expected to reach their sustainable limits in the year 2013 (SJRWMD, 2006). The predicted growth in withdrawals from the Floridan aquifer for most of the rest of the District is not sustainable through the 2030 planning horizon (SJRWMD, 2009a). Alternative water supplies under consideration include four new surface water withdrawal sites in the St. Johns River, one in the lower Ocklawaha River, and a desalination facility on the Coquina Coast (see Figure 1-2). Due partly to stakeholder concern about the shift to reliance on surface water sources, the District has embarked on an intensive study of the potential impacts of increased surface water withdrawals in the St. Johns River basin (described in more detail later in this chapter), and, in 2008, it requested that the National Research Council (NRC) form a committee to review scientific aspects of the impact assessment and provide advice to its ongoing effort. To set the context of this report, this introduction begins with a discussion of the Districtâs water resources 10
Introduction 11 FIGURE 1-1: The St. Johns River Water Management District. SOURCE: http://sjrwmd.com/about.html.
12 Review of the St. Johns River Water Supply Impact Study: Report 1 FIGURE 1-2: The five surface water basins of the St. Johns River Water Management Basin and the location of six alternative water supply projects, including five surface water withdrawal sites. SOURCE: Tom Bartol, SJRWMD, personal communication, 2009.
Introduction 13 planning process, including how it identifies future water demands, evaluates water resources, and selects alternative water supply options. The chapter then describes the Districtâs Water Supply Impact Study and the role of the NRC. SJRWMD WATER RESOURCES PLANNING The District is tasked with (1) ensuring that adequate water supplies are available to meet future demands, and (2) preventing the occurrence of unacceptable impacts to water resources and related natural systems. As population growth and associated land development continue, these goals can increasingly come into conflict with each other. Thus, careful water supply planning is required. Water Resources Assessments The District works closely with water suppliers to ensure that adequate water supplies are available to sustainably address future demands, and it forecasts water demands for public and private needs, including domestic, agricultural, commercial, industrial, and power generation purposes. The most recent water demand forecasts, developed collaboratively with the District and area water suppliers, are outlined in the 2008 Water Supply Assessment (WSA; SJRWMD, 2009a). The latest assessment states that total average annual demand is expected to increase from 1,346 million gallons per day (MGD) in 1995 to 1,742 MGD in 2030.1 The WSA is produced on a five-year cycle, allowing for the successive application of improved analytical tools and resulting refinement of long-term plans (e.g., incorporating potential effects of climate change). Such frequent water demand forecast production cycles have been shown to be beneficial (Hagen et al., 2005). The demand forecasting process for the 2008 WSA used a planning horizon of the year 2030. A horizon of approximately 20 years is typical and appropriate for water management planning, especially considering the unavoidable uncertainties in the supporting forecasts and the Districtâs five-year cycle of updating. The District also makes projections to the year 2050 to identify longer-term trends and raise awareness of potential future demands. Based on its demand projections, the District analyzed the adequacy of available water resources, including consideration of conservation, water reuse, and the development of new sources. The Districtâs approach to water supply assessment assumes that the 2030 planning horizon year is one of average rainfall. However, the assessment is also conducted assuming 1- in-10 year drought conditions, which provides some degree of sensitivity analysis. From the demand and resource analyses, the District identified approximately 40 percent of its area as Priority Water Resource Caution Areas (PWRCAs), where anticipated sources of water and conservation efforts would be inadequate to meet future demands while sustaining water resources and related natural systems through 2030. Further preliminary analysis has led to almost all of the remainder of the District being identified as âpotentialâ PWRCAs. Therefore, 1 Data for 2005 is considered atypical because of high rainfall and low demand.
14 Review of the St. Johns River Water Supply Impact Study: Report 1 the District has designated its entire 18-county jurisdictional area as one water supply planning region pursuant to the requirements of Subparagraph 373.036(2)(b)2 of the Florida Statutes. There are several alternatives available to the District to meet water future needs, including conservation, reclaimed wastewater, brackish groundwater, surface water, and seawater. All are being used today to some extent, and the District imposes stringent conservation and wastewater reuse provisions in its water appropriation permits. The resulting treated wastewater is currently put to many secondary uses, such that 74 percent of treated municipal wastewater effluent in the SJRWMD is beneficially reused (SJRWMD, 2008). The extent of wastewater reuse varies widely by county, from being reused more than once in Orange, Indian River, Osceola, and Okeechobee counties to only 9 percent reuse in Duval County (FDEP, 2009). Florida Statute 373.019(1) defines alternative sources, in part, as seawater or brackish surface water or groundwater, captured wet weather flows, stormwater, or other non-traditional sources as designated in the applicable water supply plan. In its most recent Water Supply Plan (SJRWMD, 2006), the District presented many possible water supply development project options from which water utilities could select to address future supply needs including new or expanded brackish groundwater desalination facilities, surface water withdrawal sites, and seawater desalination plants. Before the District issues permits for new consumptive use withdrawals from a water source, it determines how much water is available (if any) for human use without harming the resource and its related natural systems. This is accomplished via the derivation of a minimum flow and/or level (MFL) for the relevant surface water or aquifer source. An MFL (particularly for a surface water source) takes into account seasonality and varying flow regimes in order to protect biological communities. At a given location, the MFL describes the flow magnitude, duration, and frequency necessary to prevent harm to ecological communities under a variety of high-, average-, and low-flow conditions. The MFL for the St. Johns River near DeLand is based upon an analysis by Mace (2006). Water withdrawal scenarios that do not violate MFLs can be developed in infinite variations of seasonal pumping rates and short-term storage volumes. Of the many possible scenarios, a withdrawal rate of 155 MGD was determined to be the maximum continuous yield at DeLand that would meet all MFL criteria without requiring storage (see Robison, 2004). The MFL for the lower Ocklawaha River basin is expected to be developed in the near future. MFLs are the result of statistical analyses of available and historic data and are developed to be protective of the water and ecological resource. The District conducts periodic reassessment of adopted MFLs based on consideration of new data and information as they become available (SJRWMD, 2006). Consumptive use permits are typically issued for periods of 20 years, but they may be re-opened at any time, and restrictions may be imposed on one or more use categories in response to reassessments of source yield and/or water shortages. Selection of Potential Surface Water Withdrawal Sites In order to determine potential sites for public water supply withdrawal along the St. Johns River, the District employed a structured process of data assessment, feasibility evaluation, potential project selection, and quantitative water supply availability and yield analysis (CH2M Hill, 1996a, 1996b, 1997). Briefly, this process requires first evaluating data from long-term
Introduction 15 river gauges. Yields at these gauge locations are then screened on the basis of magnitude, variability, minimum instream requirements, and other withdrawal constraints. The yield information is compared spatially with expected growth in demand at population centers in order to balance meeting demands with the least distance from a withdrawal point of adequate yield, which may or may not be coincident with a flow gauge (SJRWMD, 2006). This quantitative analysis led to the selection of the sites shown in Figure 1-2, which could supply a total combined yield of 155 MGD from the headwaters to DeLand. Additionally, in-stream monitoring and treatability studies at these sites indicated that several effective and efficient water treatment combinations (including desalting) could be used to produce water of a quality that is suitable for use as public supply and at an affordable cost (CH2M Hill, 2004; Burton and Associates, 2004). The lower Ocklawaha River basin was identified as a potential source in the Districtâs 2000 Water Supply Plan (SJRWMD, 2000) and was the subject of a separate analysis by Hall (2005), in which it was estimated to have a relatively large potential water supply yield of 107 MGD. However, it was acknowledged that a more accurate assessment of water availability would only be determined with the development of an MFL. Unique hydrologic factors make this a favorable resource for surface water supply development because inflow to the Ocklawaha River includes the 876 MGD discharge from Silver Springs. The water quality of the lower Ocklawaha River is very good, due in large part to this substantial fresh groundwater contribution. The combination of relatively good raw water quality and significant base flow make this an attractive candidate for surface water supply development. Many other smaller resource development projects have been identified as possible options for providing minor amounts of supply (SJRWMD, 2009b). WATER SUPPLY IMPACT STUDY As described in the previous section, recent water supply planning efforts, including the development of statutory minimum flows and levels (MFLs) for portions of the St. Johns River, indicate that up to 262 MGD could be withdrawn from the St. Johns (155 MGD) and Ocklawaha (107 MGD) rivers for public water supply without causing significant environmental harm. To more fully explore this possibility and at the request of the Districtâs Governing Board, in January 2008 the District embarked on a two-year, two-phase study called the St. Johns River Alternative Water Supply Cumulative Impact Assessment (CIA). The District initiated the CIA to (1) evaluate the potential environmental effects of withdrawing water from these rivers, and (2) alleviate public concern by ensuring that the best possible scientific effort has been made to evaluate potential environmental effects. Due to confusion with respect to its title, the District has subsequently renamed the study the âSt. Johns River Water Supply Impact Studyâ (WSIS) to more accurately reflect its goals. In order to maintain consistency with future NRC reports on this topic, the District study will be referred to as the WSIS in this report. The WSIS is being conducted by District staff with the assistance of several outside experts and is divided into seven workgroups: 1) Hydrologic and hydrodynamic modeling, 2) Biogeochemistry, 3) Plankton, nutrients, and total maximum daily loads,
16 Review of the St. Johns River Water Supply Impact Study: Report 1 4) Benthos, 5) Littoral zone/submersed aquatic vegetation, 6) Fish, and 7) Wetlands and wetland-dependent species. Each workgroup is examining its defined issues across the entire St. Johns River system, from the headwaters to the mouth, from the channel to beyond the margin of the floodplain, and from the soil and channel substrate to the water surface and above. Impacts to the Ocklawaha River basin are not being considered as part of this assessment because they will be addressed during the development of the MFL. However, impacts on the lower St. Johns River from withdrawal of 107 MGD from the Ocklawaha River will be included. In Phase I of the WSIS, existing models and available data were used to examine potential changes in hydrology caused by withdrawals and consequential impacts on salinity, wetland soil chemistry, flora and fauna of the river channels and associated wetlands, and effects on the littoral zone. The results of the hydrologic analyses consist largely of ranges of responses of river and wetland water flow, velocity, and depth, and the upstream extent of salinity. The biochemical analyses conducted in Phase I posited a wide range of potential impacts due to the alteration of hydrologic conditions under the influence of increased withdrawals from the river. Quantitative ranges of the biochemical impacts were developed from reaction rates extracted in the literature, and applied over the areal extent of susceptible riverine and wetland regimes. Analytical and data deficiencies will be reduced in Phase II by focused model improvement and the collection of needed monitoring data. Specific environmental impacts are expected to be better determined in Phase II. The District will use this information to delineate environmental effects boundaries and assess the potential for crossing response thresholds at various levels of water withdrawal. In each case, in order to assess the significance of these effects they will need to understand (1) the strength of the effect, (2) its likelihood, and (3) the persistence of that effect relative to recovery time. In Phase II the District also plans to recommend ways to avoid or minimize adverse hydrologic effects (e.g., low-flow cessation, altered timing of withdrawals, and design of intake structures). NRC STUDY AND REPORT ROADMAP The District has requested that the National Academies provide peer review and advice as the study progresses. The task of this NRC Committee is to review and critique the ongoing work of the WSIS via short reports and a final report (see Box 1-1). This first report is based upon a review of the draft report of the Phase I work (SJRWMD, 2008), an onsite meeting with District staff and stakeholders in January 2009, and information subsequently requested and received by the committee including a document describing plans for Phase II studies by the workgroups (SJRWMD, 2009c). As is often the case for large projects that are developed rapidly by multiple research teams and authors, the sections of the Phase I report can be criticized readily for many deficiencies in presentation, missing data, and incomplete analysis. However, the Phase I report is a first step in a complex endeavor that crosses many disciplines. This NRC report does not include critiques of details that are inherent in the preliminary nature of the Phase I study. Instead the report focuses on the key points that will lead to necessary improvements in the Phase II study. Furthermore, because this report is the first in a series, it does not attempt to cover every possible issue related to water withdrawal
Introduction 17 BOX 1-1 NRC STATEMENT OF TASK An NRC committee overseen by the Water Science and Technology Board of the National Academies will review the progress of the St. Johns River Alternative Water Supply Cumulative Impact Assessment, now known as the Water Supply Impact Study (WSIS). Communities in the St. Johns River watershed in east central Florida are facing future drinking water supply shortages that have prompted the St. Johns River Water Management District (the District) to evaluate the feasibility of surface water withdrawals. At the current time, drinking water is almost exclusively supplied by withdrawals from groundwater. Reliance on groundwater to meet growing the growing need for public supplies is not sustainable. The St. Johns River and the lower Ocklawaha River are being considered as possible alternatives to deliver up to 262 million gallons of water per day to utilities for public supply. In January 2008, the District began an extensive scientific study to determine the feasibility of using the rivers for water supply, and it has requested the advice of the National Academies as the study progresses. The WSIS is composed of six major tasks, being carried out by District staff scientists aided by a suite of outside experts, each with national standing in their scientific discipline. These activities include modeling of the relevant river basins, determining what criteria should be used to evaluate the environmental impacts of water withdrawals, evaluating the extent of those impacts, coordinating with other ongoing projects, and issuing a final report. The NRC committee will review scientific aspects of the WSIS, including hydrologic and water quality modeling, how river withdrawals for drinking water will affect minimum flows and levels in the two rivers, the impact of removing old and introducing new wastewater streams into the rivers, the cumulative impacts of water withdrawals on several critical biological targets, and the effects of sea level rise. Potential environmental impacts being considered by the District include altered hydrologic regimes in the river, increased pollutant concentrations in the rivers (e.g., sediment, salinity, nutrients, and temperature), associated habitat degradation, and other direct effects on aquatic species due to the operation of the new water supply facilities. from the St. Johns River, but rather focuses specifically on the Districtâs Phase I report. Thus, longer-term subjects such as changing land use in the St. Johns river basin, post-WSIS monitoring of the resource to accompany ongoing water withdrawals from the St. Johns, and future climate change are not addressed in this report, but will be considered for inclusion in subsequent reports of the committee. Finally, the report does not discuss predisturbance conditions in the basin because they are not used as the baseline conditions in the WSIS. This report is organized along the lines of the seven workgroups. Chapter 2 presents several overarching issues and conclusions of the committee about the Phase I Draft Report. Tackling these issues should be the highest priority of the District as it commences Phase II of the WSIS. Chapter 3 focuses on the extensive hydrologic and hydrodynamic modeling effort underway that supports the remaining biogeochemical and ecological analyses, and Chapter 4 reviews the Phase I work of the biogeochemistry, plankton, benthos, littoral zone, fish, and wetlands and wetland-dependent species workgroups. Whenever possible, conclusions and recommendations made for one workgroup that are critical or relevant to another workgroup are mentioned in both places.