Chapter 1 Minimum Flows and Levels - Southwest Florida Water ...

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The draft upper Braden report continues the District’s practice of using a 15% change in habitat availability as the threshold for defining significant harm and now applies this threshold broadly to include both spatial and temporal loss of habitat or connectivity. The Panel again acknowledges that the use of this criterion is rational and pragmatic, but also recognizes that the specific value of 15% is subjective and has only modest validation or support from the primary literature. Arguments can and likely will be made for both lower and higher percentages of habitat loss to be used for defining significant ecological harm. Other work has been done, in addition to the literature that is already cited, and the Panel believes it would be prudent to expand the literature review to gather as much additional supporting documentation as possible, much of which will be gray literature. Where lower or higher percentages have been used elsewhere, it would be illuminating to understand the rationale for these decisions (e.g., lower percentages used where imperiled or more sensitive species are concerned, higher percentages for more degraded systems, etc.). What happens if you use a 5% or a 33% reduction in habitat in your analyses? How would these values affect the recommendations for MFLs for an ecosystem like the upper Braden River? The Panel is not advocating doing the analyses on all rivers with multiple values for acceptable habitat loss, but it would be informative to do such a sensitivity analysis for a less difficult river like the upper Braden River. Such an analysis of the sensitivity of the MFLs to setting different thresholds of habitat loss where significant harm occurs would assist in the discussion of why a specific value (e.g., 15%) has been chosen. More importantly, however, is the need for the District to commit the resources necessary to validate the presumption, that a 15% decrease in spatial or temporal habitat availability or a 15% increase in violations of the low-flow threshold, does not cause significant harm. The District would appear to be in an excellent position to implement monitoring, natural experiments, and other analyses necessary to evaluate the effectiveness of this threshold and establish a framework for adaptive management. Several riverine MFLs 8-10
have now been developed and adopted by the District using the same or similar criteria, and the infrastructure for field work used to develop these MFLs is still in place. The present drought conditions that prevail over most of Florida as this peer review is written would seem to make for ideal conditions for testing and evaluating assumptions regarding minimum flows. Several previous peer reviews have called on the District to collect additional site-specific data to validate and refine assumptions used in the development of MFLs (Cichra et al. 2005 and 2007; Gore et al. 2002; Shaw et al. 2005), and the District has committed to periodic re-evaluation of its MFLs as structural changes or changes in the watershed warrant. Despite this, the Panel has seen little evidence so far that the District is moving rapidly to implement the needed monitoring or assessment. The Panel strongly believes that without such follow-up, the 15% threshold remains a presumptive criterion vulnerable to legal and scientific challenge. Analytical Tools Used to Develop MFLs PHABSIM Previous peer review reports have discussed at length and affirmed the District’s use of the Instream Flow Incremental Methodology (IFIM) and the related Physical Habitat Simulation (PHABSIM) software (Cichra et al. 2005 and 2007; Gore et al. 2002; Shaw et al. 2005). The District likewise employs this methodology to the upper Braden River, using habitat suitability curves for the same suite of three common Centrarchid (sunfish) fish species, plus invertebrates that were used in developing MFLs for the Middle Peace, Myakka, Alafia, and upper Hillsborough Rivers. Overall, the District’s use of the methodology and its description of the development of habitat suitability curves are consistent with standard practice and follow the recommendations of previous peer reviews. Habitat suitability curves were developed for spotted sunfish (Lepomis punctatus), largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), and macroinvertebrate community diversity (Gore et al. 2001, Stuber et al. 1982). These are appropriate species for consideration in rivers of the southern Florida peninsula, and their selection is validated by reported fish abundance data for these rivers. However, the Panel notes that both bluegill and largemouth bass are habitat generalists and are not especially sensitive to changes in hydrologic regime. As such, they may be rather poor choices for use in establishing MFLs, despite the merits of the IFIM/PHABSIM methodology. In keeping with previous peer reviews, the Panel recommends that the District invest the resources necessary to evaluate whether additional habitat suitability curves should be developed and PHABSIM analyses be conducted for other species that may be more sensitive to hydrological change than those used here. 8-11
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Proposed Minimum Flows and Levels f
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Table of Contents TABLE OF CONTENTS
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5.5 PRESCRIBED FLOW REDUCTION FOR B
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Figure 2-19. Potassium concentratio
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Figure 5-13. Median daily flow at t
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mean feature elevations are listed
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For the high flow season of the yea
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Acknowledgements The authors would
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fluctuations in water flows or leve
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Common to this list and the flow re
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Fundamental to the approach used fo
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300 250 Block 1 Block 3 Block 2 Flo
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are outlined in Chapter 4. In Chapt
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as the freshwater segment upstream
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attributed to analytic precision di
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Figure 2-4. 1999 land use/cover map
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Table 2-2. Land use/cover and land
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Figure 2-8. 1999 Land use/cover map
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Figure 2-10. 1972 Land use/cover ma
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Smith and Stopp (1978) note that "i
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2.4.2.1 Multidecadal Periods of Hig
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2.4.3.2 Step Trend in River Flows K
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Table 2-4. Results of Kendall's tau
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2.4.4 Benchmark Periods Climate-bas
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Oscillation were examined. On a sea
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Water Chemistry 2.4.6 Water Quality
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Braden River near Lorraine, FL 0.6
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Peace River at Arcadia, FL 10 Potas
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Table 2-8. Summary statistics for B
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3.2 Resources and Area of Concern T
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habitat, the greater area of stream
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levels such as fish have been shown
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Figure 3-1. Example of low flow in
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USGS Braden River near Lorraine gag
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instream cross-sections were sample
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Figure 4-2. Upstream vegetation cro
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supports water surface profile calc
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The HEC-RAS model was run using 21
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Adult Spotted Sunfish Adults - Brad
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species of interest. For example cu
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4.4 Seasonal Flow and Development o
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Wetted Perimeter - Sta. 44.9 25 20
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factors, the most conservative of w
Page 87 and 88: Chapter 5 Results and Recommended M
Page 89 and 90: Wetted Perimeter Requirements Flow
Page 91 and 92: 40 35 30 25 20 15 10 5 0 May June M
Page 93 and 94: Floodplain profiles and vegetation
Page 95 and 96: mean elevation of the Oak/popash ve
Page 97 and 98: Table 5-3. Mean (±SD) flows at the
Page 99 and 100: Elevaton (NGVD) 27.0 22.0 17.0 12.0
Page 101 and 102: Table 5-7. Median elevations, in fe
Page 103 and 104: 80 70 60 Flow reduction (%) 50 40 3
Page 105 and 106: Table 5-8. Recommended percent flow
Page 107 and 108: 100 90 80 % DOMINANCE 70 60 50 40 3
Page 109 and 110: Table 5-9. Mean elevation of instre
Page 111 and 112: The second standard was developed t
Page 113 and 114: Table 5-10. Proposed Minimum Flows
Page 115 and 116: Division Information and Technology
Page 117 and 118: Hupalo, R., C. Neubauer, L. Keenan,
Page 119 and 120: communities in the corridors of the
Page 121 and 122: Wharton, C.H., W.M. Kitchens, E.C.
Page 123 and 124: Confined Aquifer - A term used to d
Page 125 and 126: Instream Habitats - A specific type
Page 127 and 128: Riffle - A relatively shallow reach
Page 129 and 130: Chapter 8 Appendix A A Review of
Page 131 and 132: steps to reduce the uncertainty and
Page 133 and 134: 2007). In addition, the approach us
Page 135 and 136: with limited biological knowledge o
Page 137: the other factors listed above or w
Page 141 and 142: An example of the primary output fr
Page 143 and 144: prevent negative effects associated
Page 145 and 146: methods, such as LiDAR, to improve
Page 147 and 148: habitat reduction criterion and the
Page 149 and 150: Summary, Special Publication SJ2002
Page 151 and 152: Errata / comments by page number in
Page 153 and 154: 4-20 Section 4.7.1, 1 st paragraph,
Page 155 and 156: Chapter 9 Appendix B - Staff Respon
Page 157 and 158: 2) The panel notes that the period
Page 159 and 160: 4) One aspect of Chapter 2 should b
Page 161 and 162: Preventing Significant Harm - 15% C
Page 163 and 164: they aren't getting enough particul
Page 165 and 166: Habitat Criteria and Characterizati
Page 167 and 168: Compliance Standards and Proposed M
Page 169 and 170: Glossary of Terms 13) When an inter
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