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

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Table 2-5. Results of Mann-Whitney tests for flow differences between mean annual flows at selected gage sites for two multidecadal time periods (1940 to 1969 and 1970 to 1999). P values of 0.1 or less are highlighted in bold; p values that indicate a flow decrease between periods are shaded yellow. Excerpt of table from Kelly (2004). Site Name Median of 1940 to 1969 Median of 1970 to 1999 Test p mean annual flows n mean annual flows n Alafia River at Lithia 374.9 30 268.1 30 Pre>Post 0.0054 Hillsborough River at Zephyrhills 247 30 187 30 Pre>Post 0.0021 Hillsborough River near Tampa 516 30 264 30 Pre>Post 0.0000 Little Manatee River near Wimauma 178 30 139 30 Pre>Post 0.0954 Myakka River near Sarasota 215 30 228 30 Pre>Post 0.4094 Peace River at Arcadia 1113 30 738 30 Pre>Post 0.0035 Peace River at Bartow 241 30 145 30 Pre>Post 0.0003 Peace River at Zolfo Springs 636 30 422 30 Pre>Post 0.0007 Withlacoochee River at Croom 431 30 330 30 Pre>Post 0.0033 Withlacoochee River at Trilby 339 30 244 30 Pre>Post 0.0054 Withlacoochee River near Holder 1038 30 742 30 Pre>Post 0.0023 2-21
2.4.4 Benchmark Periods Climate-based differences in flows associated with ocean warming and cooling phases of the AMO and identification of step-trends for Florida river flows suggest that separate benchmark periods should be utilized for evaluating minimum flow criteria. For peninsular Florida, a benchmark period from 1940 through 1969 corresponds to a warm phase of the AMO, and is correlated with a multidecadal period of higher rainfall and increased river flows; the period from 1970 through 1994 corresponds to a cool phase of the AMO, and is correlated with a multidecadal period of lower rainfall and lower river flows. An apparent shift to a warmer AMO phase in the mid-1990s has recently been identified (e.g., see Goldenberg et al. 2001, Sutton and Hodson 2005), suggesting that consideration of at least three benchmark periods may be appropriate for development of minimum flows and levels. Several approaches could be used to develop minimum flows and levels given that high and low flow benchmark periods have been identified. If permitting or allowing consumptive water use is conducted on a fixed-quantity basis (e.g., 50 million gallons per day) a conservative approach for protecting the ecology and aquatic resources of river systems would be to use the drier period as the benchmark period, since this would yield the lowest withdrawal recommendation. This approach would prevent significant harm from withdrawals during the low flow benchmark period, and provide greater protection during the period of higher flows. If, however, permits are issued on a percent-of-flow basis (e.g., 10% of the preceding day's flow is available for use), the most conservative approach would be to base permitting on the benchmark period that produces the lower percent-of-flow reduction associated with the criterion or key resources identified for protection from significant harm. This would allow the recommended percentof-flow reduction to be used in either benchmark period while affording protection to the key resource(s) during both flow periods. A third option would be to adjust either the fixed quantity or percent-of-flow withdrawal restrictions according to the current AMO period or phase. From a water supply perspective, this would probably be the most desirable approach, since it would allow the maximum amount of water to be withdrawn irrespective of the multidecadal phasing of the AMO. This option, however, would be difficult to apply since there is currently no method for determining when a step change to a new climatic regime has occurred, except in hindsight. Based on the difficulty of determining when a step change in flows has occurred and given that there are several advantages to the "percent-of-flow" approach (e.g., maintenance of the seasonality and distribution of flows in the natural flow regime) over the fixed-quantity approach, we have developed minimum flow criteria that are based on percent-of-flow reductions. Under most circumstances we anticipate that for most rivers, these criteria will be based on the most restrictive flow reductions associated with analyses involving two benchmark 2-22
Page 1 and 2: Proposed Minimum Flows and Levels f
Page 3 and 4: Table of Contents TABLE OF CONTENTS
Page 5 and 6: 5.5 PRESCRIBED FLOW REDUCTION FOR B
Page 7 and 8: Figure 2-19. Potassium concentratio
Page 9 and 10: Figure 5-13. Median daily flow at t
Page 11 and 12: mean feature elevations are listed
Page 13 and 14: For the high flow season of the yea
Page 15 and 16: Acknowledgements The authors would
Page 17 and 18: fluctuations in water flows or leve
Page 19 and 20: Common to this list and the flow re
Page 21 and 22: Fundamental to the approach used fo
Page 23 and 24: 300 250 Block 1 Block 3 Block 2 Flo
Page 25 and 26: are outlined in Chapter 4. In Chapt
Page 27 and 28: as the freshwater segment upstream
Page 29 and 30: attributed to analytic precision di
Page 31 and 32: Figure 2-4. 1999 land use/cover map
Page 33 and 34: Table 2-2. Land use/cover and land
Page 35 and 36: Figure 2-8. 1999 Land use/cover map
Page 37 and 38: Figure 2-10. 1972 Land use/cover ma
Page 39 and 40: Smith and Stopp (1978) note that "i
Page 41 and 42: 2.4.2.1 Multidecadal Periods of Hig
Page 43 and 44: 2.4.3.2 Step Trend in River Flows K
Page 45: Table 2-4. Results of Kendall's tau
Page 49 and 50: Oscillation were examined. On a sea
Page 51 and 52: Water Chemistry 2.4.6 Water Quality
Page 53 and 54: Braden River near Lorraine, FL 0.6
Page 55 and 56: Peace River at Arcadia, FL 10 Potas
Page 57 and 58: Table 2-8. Summary statistics for B
Page 59 and 60: 3.2 Resources and Area of Concern T
Page 61 and 62: habitat, the greater area of stream
Page 63 and 64: levels such as fish have been shown
Page 65 and 66: Figure 3-1. Example of low flow in
Page 67 and 68: USGS Braden River near Lorraine gag
Page 69 and 70: instream cross-sections were sample
Page 71 and 72: Figure 4-2. Upstream vegetation cro
Page 73 and 74: supports water surface profile calc
Page 75 and 76: The HEC-RAS model was run using 21
Page 77 and 78: Adult Spotted Sunfish Adults - Brad
Page 79 and 80: species of interest. For example cu
Page 81 and 82: 4.4 Seasonal Flow and Development o
Page 83 and 84: Wetted Perimeter - Sta. 44.9 25 20
Page 85 and 86: factors, the most conservative of w
Page 87 and 88: Chapter 5 Results and Recommended M
Page 89 and 90: Wetted Perimeter Requirements Flow
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Page 93 and 94: Floodplain profiles and vegetation
Page 95 and 96: mean elevation of the Oak/popash ve
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Table 5-3. Mean (±SD) flows at the
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Elevaton (NGVD) 27.0 22.0 17.0 12.0
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Table 5-7. Median elevations, in fe
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80 70 60 Flow reduction (%) 50 40 3
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Table 5-8. Recommended percent flow
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100 90 80 % DOMINANCE 70 60 50 40 3
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Table 5-9. Mean elevation of instre
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The second standard was developed t
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Table 5-10. Proposed Minimum Flows
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Division Information and Technology
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Hupalo, R., C. Neubauer, L. Keenan,
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communities in the corridors of the
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Wharton, C.H., W.M. Kitchens, E.C.
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Confined Aquifer - A term used to d
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Instream Habitats - A specific type
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Riffle - A relatively shallow reach
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Chapter 8 Appendix A A Review of
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steps to reduce the uncertainty and
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2007). In addition, the approach us
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with limited biological knowledge o
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the other factors listed above or w
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have now been developed and adopted
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An example of the primary output fr
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prevent negative effects associated
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methods, such as LiDAR, to improve
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habitat reduction criterion and the
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Summary, Special Publication SJ2002
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Errata / comments by page number in
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4-20 Section 4.7.1, 1 st paragraph,
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Chapter 9 Appendix B - Staff Respon
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2) The panel notes that the period
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4) One aspect of Chapter 2 should b
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Preventing Significant Harm - 15% C
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they aren't getting enough particul
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Habitat Criteria and Characterizati
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Compliance Standards and Proposed M
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Glossary of Terms 13) When an inter
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