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2 St. Johns River Water Supply Impact Study: Cross-Cutting Issues The St. Johns River Water Management District (SJRWMD or âthe Districtâ) has undertaken a large and complicated study to evaluate potential environmental impacts of additional consumptive-use water withdrawals from the St. Johns River and its main tributary, the Ocklawaha River. The study involves nearly one hundred scientists and engineers divided into seven workgroups addressing topics ranging from the effects of withdrawals on river hydrodynamics and hydrology to water quality and a variety of biological and ecological issues. The Phase I report of the study (SJRWMD, 2008) covers initial analyses by the workgroups on all of these topics and totals more than 700 pages of text, tables, and figures. The District is commended for the substantial financial and human resources that they have given this important study, and the workgroups also are commended for the large amount of work they accomplished in a short period of time. Phase I of the study identified important issues related to the proposed water withdrawals, established many of the kinds of information needed to assess impacts of the withdrawals, and for many of the topics made an initial evaluation of the availability of this information. The Phase I report is not very instructive, however, regarding plans for the scope of Phase II studies and how they will be conducted. Based on a request from the committee at its first meeting in January 2009, District staff produced a document describing methods they intend to use in Phase II of the study (SJRWMD, 2009c). That document, hereafter referred to as the Phase II work plans, was provided to the committee prior to its second meeting in May 2009, and it was used by the committee to inform its analysis of the Phase I study and its recommendations for work to be undertaken in Phase II. This chapter is focused on the âbig pictureââthe committeeâs assessment of the St. Johns River Water Supply Impact Study (WSIS) as an integrated wholeâand on issues that cut across or transcend the discipline-based topics of the individual workgroups. General issues such as overall study focus, goals, and design; integration of information across workgroups; and the importance of conceptual models, as well as quantitative simulation models, are the primary focus of this chapter. However, more specific issues such as the importance of quantifying return flows, role of ecological indicators, and assessment of impacts from floodplain dewatering also are discussed, along with the committeeâs recommendations for dealing with them in the WSIS. The committee feels that these should be the highest priority issues for the District to consider as Phase II commences. More specific assessments of the studies conducted by the seven workgroups are given in Chapters 3 and 4. The former chapter deals with studies by the hydrology workgroup on potential changes in the riverâs hydrodynamics and hydrology resulting from the withdrawal of an additional 262 million gallons per day (MGD) of water from the main stem of the St. Johns River and the Ocklawaha River. Chapter 4 addresses studies conducted by the other 18
St. Johns River Water Supply Impact Supply: Cross-Cutting Issues 19 workgroups, which collectively are responsible for addressing the potential water quality and ecological impacts of changes in river hydrodynamics and hydrology. STUDY FOCUS The committee notes that ecological impacts along the largest tributary to the St. Johns, the Ocklawaha River, were not being assessed to the same degree in the WSIS as in the St. Johns River itself. Increases in water withdrawals in the system have the potential to affect hydrologic and ecological conditions in the Ocklawaha, as well as the main channel of the St. Johns, and this is particularly likely given that some of the proposed additional withdrawals will occur from the area near the confluence of the Ocklawaha with the St. Johns River. The committee understands that exclusion of the Ocklawaha from the current WSIS on the St. Johns River was a conscious decision and not an oversight. The decision was based on three reasons. First, the Ocklawaha is hydrologically distinct from the St. Johns, and somewhat different issues likely would be important in an analysis of that system. Second, for financial and human resource reasons SJRWMD managers concluded that a focused study on the St. Johns River itself was more feasible and that including the Ocklawaha would dilute the effort needed for a comprehensive analysis on the St. Johns. Third and probably of greatest importance, a separate, formal (i.e., legally based) analysis of minimum flow and level (MFL) requirements for the Ocklawaha River is planned for the near future (date not yet specified by the SJRWMD). The MFL process would not be as elaborate as the current WSIS, but it would represent an additional several hundred thousand dollar effort on the Ocklawaha River. The committee does not dispute the reasoning of the District in deciding to focus on the St. Johns River. Hydrologic changes in the Ocklawaha River in fact are not being excluded from the St. Johns River WSIS but are being treated as âinput conditionsâ for the assessment of impacts along the St. Johns River. Given the near-term plans (not yet fully specified) for a separate MFL analysis on the Ocklawaha River, it seems prudent to focus the current analysis on the main-stem St. Johns. Nonetheless, the committee recognizes the need for comparable impact analyses on the Ocklawaha River, particularly its lower reaches, which are the most likely to be affected by additional water withdrawals in the basin. In addition, the committee concludes that to avoid future misunderstandings the SJRWMD should provide a better explanation of the basis for its decisions on this issue in public documents, presentations, and web-based materials related to the WSIS and should make the focus of the WSIS on the main stem St. Johns River clear in its publications and presentations. Another concern about the study focus is the lack of attention in the WSIS to the impacts of growth in the human population of the drainage basin that the appropriation of an additional 262 MGD of water will enable. A widely used rule of thumb in water supply planning states that per capita use of water in municipalities on average is about 100-150 gallons per day. This includes water used in the commercial sector, for fire fighting and public use (e.g., in parks), as well as consumption within individual homes. A total additional withdrawal of 262 MGD from the St. Johns River thus would enable approximately 1.7 to 2.6 million more people to live in the drainage basin (assuming no reuse of the withdrawn water occurs). That population, depending on where it is located, could have small or major impacts on water quality in the St. Johns River and its tributaries. The committee recognizes that population growth is a sensitive issue in Florida, that the District has no direct control over this issue, and that accurate predictions of
20 Review of the St. Johns River Water Supply Impact Study: Report 1 impacts resulting from the additional population cannot be made without more knowledge about the geographic locations where the growth would occur. Nonetheless, the committee recommends that the District at least acknowledge the potential impacts of this growth in its assessment documents, even if it cannot quantify the impacts. NEED FOR INTEGRATION Almost any study of the magnitude of the St. Johns River WSIS must be subdivided into components that can be addressed by individuals or small work groups in order to be accomplished in a reasonable timeframe. The committee thus understands and supports the Districtâs approach to divide the WSIS among seven workgroups. The danger in such an approach, however, is that the study could become seven separate studies each with narrowly focused conclusions in the subject expertise of the workgroup rather than an integrated assessment in which output from one workgroup serves as input to another group for an iterative analysis of ecosystem impacts. For example, changes in the benthic macroinvertebrate assemblage may engender changes in the fish assemblage, which in turn may stimulate changes in other segments of the biological community, and feedbacks also occur, making cross- workgroup collaborations essential to a comprehensive analysis. In oral discussions with staff from the District, the committee has been assured that the project managers and staff agree on the need for integration and are experienced at doing this. However, the written document available for the committee to review, the Phase I report, does not provide much evidence for integrative and cross-workgroup analyses. In part this may reflect the short timeframe allowed for Phase I work to be accomplished and the report to be written. The committee strongly recommends that this situation not occur again in Phase II. Sufficient time and project funds need to be allotted to integrative studies and to cross- workgroup analyses before the final report is written. The committee notes that integration is not an âautomatic outcomeâ in any large, multidisciplinary undertaking; it needs to be planned for and managed. Applying a Conceptual Framework to Integrate Studies During two of the Districtâs presentations to the committee, conceptual frameworks depicting how various parts of the river system interact were shown that did not appear in the projectâs written reports. As a way of integrating the work of the seven science groups, it is recommended that the District further develop these conceptual frameworks of qualitative interactions. The term âframeworkâ is used here instead of âmodelâ to clearly distinguish between an overarching organizational framework and the discipline-specific models used in different parts of the study. This framework should provide a means for linking the various ecological and physical relationships affected by surface water withdrawals. The framework should be built from the bottom-up, with the validity and importance of each linkage being independently evaluated. Each process and linkage should be identified as to whether it is demonstrated by data or by model predictions, or whether it is a hypothesis or assumption, thereby allowing cross-disciplinary understanding of the limits of existing science for the St. Johns River. The framework should not be simply a set of one-way descriptive boxes; that is, if
St. Johns River Water Supply Impact Supply: Cross-Cutting Issues 21 it merely illustrates the subsidiary processes and linkages, it will be of limited use. Instead, the District should focus on a framework with feedbacks from individual research project goals and methods that are specific to the St. Johns River. Each piece of the research program should be motivated to fill in specified unknowns in the conceptual framework boxes and linkages. An example of a complete and comprehensive conceptual framework is the one developed for the Florida Everglades (http://www.evergladesplan.org/pm/recover/cems.aspx). It is not expected that the District can develop a similarly comprehensive set of concepts within the scope of the present project. Furthermore, simple adaptation of the Everglades framework is discouraged. However, a more modest conceptual framework might be represented as either a matrix or flow chart that links possible physical effects caused by surface water withdrawal to the perceived chain of ecological effects and their consequences and the resulting research needs. This approach can be used to better connect the field studies, models, and analyses. Such a framework should explain (1) how the field data collected are appropriate to the model/analysis needs, and (2) how the model/analysis outputs will answer the key questions to quantify the linkages and processes that are unknown. The District should use this framework to help formulate which studies form the critical paths to quantifying impacts. The overall goal is to develop a more holistic and linkage-based understanding of the interplay between the different ecological disciplines and the physical process, while ensuring that critical pieces are not neglected. In the spirit of adaptive management, the framework should be revised and updated as new data and information are collected, analyzed, and modeled, and it should provide feedback to help modify monitoring and research strategies (as discussed below). Development of such a framework will be important for scientists within the District to better communicate with one another as well as with their consultants, this committee, and other reviewers of their work including the public. Each of the workgroups of the WSIS is using models to conduct scenario analyses. The District staff should evaluate what should and can be done to connect the models among the workgroups. As a minimum, the assumptions used by one workgroup in running a particular model need to be apparent to other workgroups who intend either to use the model directly or to use model output produced by the first workgroup in their own analyses. The committee is aware of the difficulties involved in linking models that have substantially different computational time-steps and different spatial scales, but efforts to link the models, where feasible, would doubtless lead to more sophisticated and comprehensive analyses, and the committee encourages the District staff to move in that direction. Finally, in both modeling and synthesis of the findings from the WSIS, the District staff and their consultants are encouraged to incorporate uncertainty analyses to the extent possible. Reliance on mean values produced by models or other analyses is highly unlikely to reflect the richness of information obtained by the study and also unlikely to reflect the range of impacts of additional water withdrawals on the St. Johns River and associated ecosystems. Using Testable Hypotheses and Quantitative Research Questions Integration would be more easily achieved if the District were to provide a clearer set of testable hypotheses and quantitative research questions that link the hydrodynamics and hydrology to the ecology and reflect the state of knowledge along with the planned studies. That is, the proposed conceptual framework described above provides organizing
22 Review of the St. Johns River Water Supply Impact Study: Report 1 principles for qualitative understanding of the linkages, whereas the hypotheses and research questions provide the guidelines for the scientific efforts required to quantify the linkages. As an example, an overarching set of physical hypotheses might be framed as follows: withdrawal of surface water from the middle St. Johns River will result in one or more physical consequences: (1) increased reverse flow within the lower St. Johns River, (2) increased downstream flow in the upper St. Johns River, (3) increased groundwater discharge into the river, and (4) reduced water levels. These physical consequences are sketched in Figure 2-1. All the possible consequences should be paths in the conceptual framework, but an organized plan of testing is required to identify and quantify key processes and determine which may be omitted from further consideration. To continue this example, subsidiary physical hypotheses might be: (a) increasing reverse (upstream) flow leads to increasing salinity in the lower St. Johns River due to tidal transport of oceanic water; (b) increased downstream flow in the upper St. Johns River leads to higher velocities and a reduction in wetland area, and (c) increased groundwater flow leads to a lowering of the water table and/or increased saltwater discharge to the river. Each of these physical hypotheses could be linked to hypotheses associated with ecological behavior (for example, increase salinity in the lower St. John River could have negative effects on beds of submersed aquatic vegetation). A similar set of hypotheses could be generated for the effects of sea-level rise. With these hypotheses as the research guidelines, the District could ensure that the individual research projects will provide answers to research questions framed around quantifying the individual paths and processes. Creating hypotheses and research questions as part of a conceptual framework can build on the prior studies of modeling on the lower and middle St. Johns River. The modeling efforts were based on model availability and an initial analysis of what constitutes the major issues. From the Phase I screening studies it appears that there are two likely physical impacts of the proposed surface water withdrawals: (1) increased upstream propagation of salinity in the lower St. Johns River caused by reduced downstream flows below the surface water withdrawal, and (2) alteration of the flow and velocity regimes in the middle St. Johns River that may lead to changes in velocity regimes and possibly increased water age (i.e., the length of time a water parcel remains in the river). The Phase I modeling studies did not consider the upper St. Johns reduced water levels surface water increased withdrawal downstream flow upstream movement of salt water boundary increased increased reversing groundwater (tidal) flows discharge FIGURE 2-1: Sketch of hypothesized chain of physical consequences caused by surface water withdrawals.
St. Johns River Water Supply Impact Supply: Cross-Cutting Issues 23 River and possible effects of increased groundwater discharge, leaving substantial unanswered questions as to whether the surface water withdrawal will be compensated for by increased groundwater discharge, drying of wetlands in the middle and upper St. Johns River, or reversed flow from the lower St. Johns River. These issues should become part of the conceptual framework created during Phase II of the WSIS. Investigating Individual Species as Indicators of Community Change Different workgroups of the WSIS are analyzing potential impacts of additional water withdrawals on several major types of biota: submerged aquatic vegetation (SAV), other wetland vegetation, benthos, fish, and birds. Committee concerns related to individual types of biota are discussed in Chapter 4, but a cross-cutting concern that transcends the individual cases is the basis by which decisions are made to focus on particular species in the WSIS. It generally is not clear to the committee whether the most sensitive species are being considered. Moreover, reliance on single species as indicators of change may underestimate broader biological consequences and miss some of the clearest and most easily interpreted signals of the effects of water withdrawal. That is, a focus on individual species may limit the Districtâs ability to detect and understand a variety of important ecological dynamics caused by water withdrawals. The past two decades have seen the development of more integrative, quantitative methods to characterize the multifaceted aspects of ecological condition (Karr, 2006; Fore et al., 2007; Yoder and Barbour, 2009; Pont et al., 2009). The most integrative of these methods involve (often multimetric) biological indexes, predictive models, or combinations of both approaches. Both American and European governments have acknowledged the utility and need for these integrative ecological approaches (e.g., EPA, 2003, and Pont et al., 2007, regarding the European Water Framework Directive). Widespread successful application of biological indexes for all the major taxa (vegetation, benthos, fish, and birds) and in the major environment types that dominate the St. Johns River basin (wetlands, freshwater streams, and estuaries) underscores their power in understanding and predicting the effects of water withdrawal on St. Johns ecosystems. A clear example of the need for integration (that is elaborated on in Chapter 4) is provided by the fish workgroup. Fishes inhabiting a river as large and varying over its length as the St. Johns have complex life histories. Many estuarine-dependent fishes spawn off shore (or near shore); the larvae are recruited into estuaries and settle into nursery habitat where they grow to late juveniles or adults; and later, adults migrate back offshore to spawn (Beck et al., 2001). In contrast, some freshwater fishes move along salinity gradients from fresh water to low salinity segments (Peterson and Ross, 1991; Wagner, 1999, Wagner and Austin, 1999). The overlap of these two faunas makes estuarine systems diverse and productive (Peterson and Meador, 1994). Thus, a full understanding of the effects of water withdrawals on St. Johns River fishes will require, at the very least, coordinating the results of the fish studies with studies on hydrology, benthic macroinvertebrates, and aquatic vegetation. Fish behavior and ecology are influenced both directly by salinity and indirectly by many other factors that also may be influenced by salinity shifts. The cumulative interaction of the assemblage will be critical to understand fish responses to salinity (Peterson, 2003). Furthermore, fishes likely will respond to changes in SAV and macroinvertebrate communities in ways that are entirely independent of salinity
24 Review of the St. Johns River Water Supply Impact Study: Report 1 changes. The WSIS has yet to integrate the fish work with work on other biological assemblages. One final issue is the potential change in the landscape habitat mosaic of the St. Johns River (also known as beta- or between-habitat diversity, MacArthur, 1965) that might occur with water withdrawals. Davis et al. (2002) noted that common estuarine fauna were replaced by hard-substrate marine fauna and fishes in areas of mud bottom altered with large granite rip-rap in San Diego Bay, California. In this example, human alteration of the environment changed the estuarine community to resemble an open water marine community. Water withdrawals on the St. Johns River could alter beta-diversity in the basin by causing some environments and their associated communities to disappear (e.g., as in the San Diego Bay example just cited) within segments of the basin. Water withdrawal could also alter the mosaic of environment types in both estuarine and freshwater segments of the basinâchanges that could substantially affect resident species and migratory fishes and birds that use mosaic environments to survive throughout the year. WATER AND NUTRIENT BUDGETS In reviewing Phase I of the WSIS, the committee often had difficulties placing the proposed water withdrawals into context relative to current conditions in the river. Specifically, the committee found it difficult to obtain answers to such questions as: (1) What proportion of the total flow at various locations along the river does 262 MGD represent, and (2) How does this proportion vary in relation to standard hydrologic statistics like annual average, seven-day average low flow at a ten-year recurrence interval (7Q10), and other analogous flows? The committee is confident that the District has large and detailed historical records of flows at various locations in the river, whereby such calculations can be made, and we encourage the District to do so. Indeed, the District recently informed the committee that the 155 MGD proposed continuous withdrawal at DeLand is approximately 7.8 percent of the average daily flow over the period of record. This is clearly a significant fraction of the average daily flow, and will have increased effects under low flow conditions. Thus, seasonal analysis of the relationship between the proposed withdrawal and the water budget should be provided. On a broader scale, it also would be useful for the District to assemble basic water budget information for the drainage basin and its major subunits. These budgets should include the standard sources, sinks, and storage components of such budgets, as well as information on how these components vary over time. One important use of the water budget information will be to develop nutrient (nitrogen and phosphorus) budgets for key subunits of the drainage basin. As mentioned in more detail in Chapter 4, such information is needed in the WSIS to conduct a credible analysis of the impacts of water withdrawals on algal blooms in the river and especially in the large lakes (e.g., Lake George) that constitute major parts of middle portion of the St. Johns River. Comprehensive information on nitrogen and phosphorus loadings to the system currently is lacking, or at least has not been assembled in a system-wide way. The budgets need to include nitrogen and phosphorus loadings from springs, as it has been noted by District monitoring activities that elevated concentrations of nitrate and phosphate occur in some springs, apparently as a result of
St. Johns River Water Supply Impact Supply: Cross-Cutting Issues 25 human activities in the recharge areas of the Floridan Aquifer. Nutrient budget information also is needed to evaluate the importance of nutrient loadings from the return flows discussed below. The extent to which extended periods of low flow conditions will exacerbate algal bloom conditions in Lake George and other large impoundments of the river cannot be assessed properly without more comprehensive nutrient budget information for the system as a whole. Quantifying Return Flows Water withdrawals are treated in the WSIS as consumptive uses with no return flows of withdrawn water to the system. District scientists stated that they used this approach because (1) they do not know where, how, or to what extent withdrawals would return to the system and (2) this is the most conservative case to analyze. The committee appreciates the difficulties involved in estimating future patterns of consumptive water use, given uncertainties regarding future climatic and land-use conditions (e.g., types and extent of agriculture, further development of low-density residential areas, and water-demanding recreational facilities like golf courses). Nonetheless, substantial data are available to the SJRWMD staff on past and current consumptive and non-consumptive uses of water in the drainage basin based on existing patterns of development. It should be feasible to provide a range of scenarios of the extent to which future withdrawals will be consumptive uses. For both hydrologic and water quality budgeting purposes it also is important to predict the extent to which non-consumptive uses will return directly to surface streams versus recharge of groundwater. Return flows of water used for agriculture almost certainly will have elevated concentrations of nutrients, and depending on the agricultural use also may have elevated levels of pesticides, antibiotics (used in animal production), and eroded soils. Return flows from residential uses and such associated uses as golf course irrigation similarly can be expected to be degraded in terms of nutrient concentrations and a wide variety of organic contaminants. Consequently, to the extent that withdrawn water is returned to the river (directly or indirectly), it is likely to return in a degraded condition. DEWATERING OF FLOODPLAINS AND WETLANDS Results from the hydrologic modeling studies suggest that the decline in surface water levels produced by the proposed water withdrawal will be small, perhaps 1 cm to at most 4 cm. Initial consideration of this result might suggest that the likely environmental effects will be minimal. The project team should avoid such a judgment as they consider two issues. First, careful analysis should be completed to determine the floodplain area to be dewatered as a result of the lower water levels, including the timing and duration of dewatering events. Because of the flat terrain of the St. Johns River Basin as a whole and the extremely flat terrain near the river channel, the river has an extensive floodplain and associated riparian wetlands that are of great ecological significance. The flatness of the terrain also implies that water withdrawals are likely to induce small changes over very large areas. Thus, hydrologic modeling of the floodplain is essential to address questions about water withdrawal impacts on wetland biota and on important biogeochemical cycling processes in floodplain and riparian wetlands. This type of hydrologic modeling was not conducted in the Phase I effort, although it is of
26 Review of the St. Johns River Water Supply Impact Study: Report 1 critical importance to the biogeochemistry, benthic, fish, and wetlands workgroups. The committee is pleased to find that this modeling will be a part of the Phase II studies (see SJRWMD, 2009c), but it is unclear how this information will be used by the District to address questions about impacts on wetland biota and biogeochemical cycling processes. Second, an effort should be made to determine the nature and areal extent of locations that may not become completely dewatered but may experience altered biology (e.g., benthic invertebrates, vascular plants, algae and diatoms, soil changes, fish). As discussed in Chapter 4, partial dewatering of wetlands and floodplains may affect species composition and abundance and other ecological characteristics, including production. Direct effects on those areas and from these changes in habitat should be considered. For example, do the larval stages of any fish depend on relatively shallow areas that will be altered by water withdrawals? The Phase I report includes a thoughtful discussion on the differential sensitivity of diverse invertebrate taxa to water level fluctuations. Coupling that discussion with knowledge of the areal extent of habitat changes, especially the floodplain edge microenvironments such as emergent vegetation and woody debris, will be an important component of the next phase of the project. SUMMARY In summary, several issues touch on the goals of many of the workgroups and should be considered by each as the WSIS enters its second phase. These include the need for integration of information and results across the workgroups, assessment of future growth in the basin and its relationship to potential withdrawals, creation of water and nutrient budgets for the basin, and more comprehensive investigation of how the floodplains and wetlands in the basin will be dewatered by potential water withdrawals.