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

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To further investigate limiting factors associated with the Braden River floodplain, percent-of-flow reductions that would result in a 15% loss of the number of days river flows reached a range of flows were identified for the Braden River near Lorraine gage, using flow records for the period of record (Figure 5-8). The low end of the flow range examined reflects the approximate 50% exceedance flow for the period of record (6 cfs), a flow which defines the beginning of Block 3. The high end of the plotted flow range was selected to exclude rare flow events (approximately the 1% exceedance) that would be expected to occur for relatively short durations; durations for which 15% changes would be difficult to evaluate. Figure 5-8 indicates that for flows of approximately 100 cfs or greater, flow reductions that result in a 15% reduction in the number of days the flow is achieved, tend to stabilize around 10% for Braden River near Lorraine gage site. This percent-of-flow reduction is comparable to the flow reduction values derived for mean flows that would inundate dominant wetland vegetation classes, mucky soils, and top of bank elevations (Table 5-3). Collectively, these data indicate that up to a 10% reduction in the flows necessary to inundate floodplain features of the Braden River, including those we have not identified, will result in a 15% or less reduction in the number of days the features are inundated. However, Figure 5-8 also shows that there is a range of flows that occur during Block 3 which do not require flow reductions to be limited to 10% to avoid a 15% reduction in the number of days the flows are achieved. Using the period of record 15% exceedance flow of approximately 54 cfs at the Braden River near Lorraine gage as a cutoff for this range of flows, we can apply a stepped prescription, which allows a 10% reduction in flows when flow exceeds 54 cfs, and a 19% reduction in flows when the flow is below 54 cfs (Figure 5-8). While additional flow reduction steps or percentages could be identified, or an algorithm applied to determine allowable percent-of-flow reductions, the single step approach provides a conservative means for assuring that unidentified factors are likely to be protected and that flows not necessary for prevention of significant harm are available for consumptive use. Unidentified factors could include vegetative classes or species that we did not examine, or inundation of vegetative classes to specified depths. 5-16
80 70 60 Flow reduction (%) 50 40 30 20 10 0 0 100 200 300 400 500 600 700 800 Flow (cfs) Figure 5-8. Percent-of-flow reductions that result in a 15% reduction in the number of days flow are achieved, based on period of record (1988-2005) flow records from the USGS Braden River near Lorraine gage. 5.4.4 Short-Term Compliance Standards for Block 3 Short-Term Compliance Standards represent a flow prescription that can be utilized for evaluating minimum flows compliance on a short-term basis, for example, based on measured daily flows. For the USGS Braden River near Lorraine gage site, the following Short-Term Compliance Standards are proposed for Block 3, which for the upper Braden River begins on June 20 and ends on October 24: 1) The low-flow threshold is 7 cfs; 2) A 19% reduction of all flows between 7 cfs and 54 cfs are available for use, provided that the low-flow threshold is not violated; and 3) A 10% reduction of all flows above 54 cfs is available for use. 5-17
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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
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
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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
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Page 89 and 90: Wetted Perimeter Requirements Flow
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Page 93 and 94: Floodplain profiles and vegetation
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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: Table 5-7. Median elevations, in fe
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Page 109 and 110: Table 5-9. Mean elevation of instre
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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
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Page 123 and 124: Confined Aquifer - A term used to d
Page 125 and 126: Instream Habitats - A specific type
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Page 129 and 130: Chapter 8 Appendix A A Review of
Page 131 and 132: steps to reduce the uncertainty and
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Page 149 and 150: Summary, Special Publication SJ2002
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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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