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

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Chapter 2 BASIN DESCRIPTION WITH EMPHASIS ON LAND USE, HYDROLOGY AND WATER QUALITY 2.1 Overview This chapter includes a brief description of the Braden River watershed and is followed by a presentation and discussion of land use, hydrology, and water quality data relevant to the development of MFLs on the upper, freshwater segment of the Braden River above the USGS Braden River at Linger Lodge near Bradenton FL gage site (or alternatively above the Bill Evers Reservoir). Land use changes within the basin are evaluated to support the hydrology discussion that follows and to address the potential impact of land use changes on river flow volumes. Flow trends and their potential causes are discussed for the Braden River and compared with other regional rivers to provide a basis for identifying benchmark periods and seasonal flow blocks that are used for a building block approach in the establishment of minimum flows. Water chemistry changes are discussed to illustrate how land use changes may have affected observed trends in certain water quality parameters, and to demonstrate how these trends are useful in interpreting flow changes over time. 2.2 Watershed Description (material in this section was taken largely from DelCharco and Lewelling, 1997). 2.2.1 Geographic Location The Braden River is the largest tributary to the Manatee River, which empties into the southern portion of Tampa Bay (Figure 2-1). In 1936, the Braden River was dammed approximately six miles upstream from its mouth with a weir structure, named the John Ward Dam, to provide a freshwater source for the City of Bradenton. The initial dam was a 838-foot broad-crested weir which created a backwater effect extending approximately 6 miles upstream. The resulting 167- acre reservoir was named Ward Lake and stored approximately 585 million gallons. The reservoir was expanded in 1985 to 359 acres and storage capacity was increased to 1,400 million gallons by dredging the channel and surrounding riverbank upstream of the weir. Ward Lake was renamed the Bill Evers Reservoir at that time. Approximately 90 percent of the 83 square mile watershed lies within Manatee County, and the remaining 10 percent lies in northern Sarasota County. DelCharco and Lewelling (1997) identified three segments to the Braden River; the lower, middle and upper. The lower segment is the area downstream of the Evers Reservoir and is the estuarine portion of the river. The middle segment is essentially the reservoir, and the upper segment was identified as an incised channel free of any backwater effect. For the establishment of MFLs outlined in this report, the upper Braden River is defined 2-1
as the freshwater segment upstream of the USGS Braden River at Linger Lodge, near Bradenton gage site. For practical purposes, this is equivalent to the portion of the river upstream from the Bill Evers Reservoir. Development of MFLs, applicable to the estuarine segment of the Braden River, will be addressed as part of the Manatee River estuary system. Figure 2-1. Map of the Braden River watershed showing the Braden River main-stem and tributaries, sub-basins and USGS gage site locations. 2.2.2 Climate The climate of the watershed is characterized as subtropical with high average annual rainfall and temperatures. For the period of record (1911 to 2004), rainfall has averaged 54.9 inches with 61% occurring in the typical rainy season which extends from June through September (Figure 2-2). November is typically the driest month (averaging approximately 2 inches) and September the wettest (averaging 9.5 inches). Periodic cold fronts account for most of the rainfall from December through March, while heavy rainfall is often associated with tropical storms and hurricanes that typically occur between June and November. Annual air temperature averages 72ºF. Evaporation in Manatee County has been estimated at about 39 inches per year (Cherry et al. 1970), while average lake evaporation is reported to average about 52 inches per year (Kohler et al. 1959). 2-2
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: are outlined in Chapter 4. In Chapt
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 and 46: Table 2-4. Results of Kendall's tau
Page 47 and 48: 2.4.4 Benchmark Periods Climate-bas
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
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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
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Chapter 5 Results and Recommended M
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Wetted Perimeter Requirements Flow
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40 35 30 25 20 15 10 5 0 May June M
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Floodplain profiles and vegetation
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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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