Weeki Wachee River System Recommended Minimum Flows and ...

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6.0 Discharge:Precipitation (cfs/in) 5.0 4.0 3.0 2.0 1.0 0.0 1929 1939 1949 1959 1969 1979 1989 1999 2009 Year Figure 5. Time series plot of Weeki Wachee Spring annual discharge:precipitation ratio. One potential explanation for the lack of a strong relationship between groundwater pumpage and spring discharge is the pumpage data itself. The surface drainage basin for Weeki Wachee Spring covers ~38 square miles (mi 2 ), but the springshed is much larger (~260 mi 2 ) and extends into adjacent Pasco County. This means that land use, water management practices and hydrogeological conditions outside the local area are affecting the Weeki Wachee Spring discharge. The District’s report indicates that the pumpage data are from Hernando County, yet the largest wellfields in or near the springshed, in terms of pumpage, are in Pasco County. Therefore, inclusion of the Pasco County pumpage data, coupled with appropriate response lags, might strengthen the apparent relationships. Moreover, a thorough characterization of the springshed, rather than the surface-water basin, will assist in establishing the background and basis for the District’s development of MFLs for Weeki Wachee and the other springs in the system, as required by Florida statutes. Regression Equations for Tide and Salinity The District needed to develop regressions for predicting salinity in the system since many of the biological impacts of reduced flow are related to salinity. Initially the thinking was that the salinity regressions would likely have the tide at Bayport as an independent variable. Thus, a 14
egression equation for the harmonic constituents of the tide at Bayport was developed (page 49, SWFWMD 2008). It appears that this equation contains an error of omission; that is, it omits the phase-lag term for each tidal constituent, which would be added to the time term. The tidal signal could have been removed by applying an approximate 60-hr low pass filter to the water level data. The addition of the two low frequency constituents is important because this seasonal water level change has been found to affect salinities in other Gulf Coast estuaries. However, in the final development of the salinity regression equation that was used by the District in determining the MFL, the predicted tide at Bayport was not used. Before developing regression equations to predict salinity at a particular point on the WWRS and to predict the longitudinal location along the river of bottom isohalines, a regression analysis was undertaken to predict the salinity at Bayport. Various components were considered as independent variables (e.g., springflows, flow from the Withlacoochee River, Gulf tides, wind, etc.). It was found that springflows have virtually no impact on salinity at Bayport. Although a regression equation was developed with a coefficient of determination (r 2 ) of ~0.6, predicted salinity at Bayport was not included as an independent variable in the regressions for salinity in the WWRS. Regressions were developed for salinity at a particular river location and for the location of a particular bottom isohaline. These ended up with the following equational forms: Salinity = β 0 + β 1 * Flow + β 2 * R km R km = β 0 + β 1 * Flow + β 2 * Bottom Salinity Isohaline Obviously, many regression equation forms are possible; however, one particular form containing an auto-regressive salinity term with appropriate time lag is often used to improve salinity regression equations in estuarine systems. With this form of the equation it is simple to solve for one of the variables (e.g., flow) given values for the other two. This character of the isohaline equation was of great utility in determining the MFLs. The r 2 for the regression equation used to predict the location of an isohaline zone has a reasonable value of 0.66. 15
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Weeki Wachee River System Recommend
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Conversion Table Metric to U.S. Cus
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5.2 FISH ..........................
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Figure 3-2 Location of Bathymetric
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LIST OF TABLES Table 1-1 Rule-of-Th
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Table 8-1 Summary of Weeki Wachee M
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Executive Summary Minimum Flows and
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CHAPTER 1 - PURPOSE & BACKGROUND OF
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1) flood flows that determine the b
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the area." What constitutes "signif
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Table 1-1 Rule-of-Thumb Estimates f
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this report identifies specific res
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1.6 Content of Remaining Chapters I
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CHAPTER 2 - WATERSHED CHARACTERISTI
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# # # circular vent 1.8 meters in d
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Figure 2-5 1970s Aerial with 1999 U
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is a variation of the Seminole word
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Figure 2-6 Hurricane Tracks near Ba
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varied by period. The variation was
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2.3.2 Baseline Period Figure 2-10 i
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found (ktau p=0.06) between total g
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similarly across the springsheds ex
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Figure 2-15 Wavelet Filtered Discha
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Figure 2-16 INTB Groundwater Model
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2.6 Seasonal Blocks As described in
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Table 2-6 Median (cfs) Flow by Bloc
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# # # Surface waters in this stretc
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3.1.3 Segmentation Segmentation was
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Figure 3-5 Dominant SAV and Median
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Figure 3-6 Sediment Characteristics
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Figure 3-7 Shoreline / Buffer Veget
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CHAPTER 4 - TIDE, SALINITY & WATER
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Two additional harmonic pairs were
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Figure 4-5. Median Bottom Salinity
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Figure 4-7 Salinity Range (1984-200
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uncovering in response to strong wi
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E) Salinity = β o + β 1 *Flow 2 +
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Additional exploratory attempts usi
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86 = 186 cfs, SWFWMD 1994-96 = 167
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A regression of the form below was
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Table 4-8 Median Water Quality of W
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Figure 4-10 Nitrate Concentration a
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CHAPTER 5 - BIOLOGICAL CHARACTERIST
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Figure 5-1 Principal Component Anal
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measured volume sampled which was t
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5.2.2 Relation to inflow Response t
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Table 5-7 Location Response (km u )
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Table 5-9 Abundance Response to Inf
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animals can survive chronic exposur
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Figure 5-3 Number of Aerial Manatee
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Figure 5-5(a) Molluscan Presence /
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Table 5-11 Rank Order of Mollusc Ab
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Figure 5-5 Polymesoda caroliniana A
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Figure 6-1 Plankton Tow Flows Compa
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In application, a baseline area and
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6.1.4 Benthos Protection for benthi
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Figure 6-3. Location of the Three P
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7.2 Manatee Approach Establishing a
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Figure 7-2 Joint Probability of Occ
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Figure 7-3 Maximum Day Manatee Usag
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Figure 7- 6 Example Calculations fo
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Figure 7- 7 Estimation of Flow Redu
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Figure 7-8. Summary Results for the
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The reductions in flow that meet th
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probably accounts in part for the d
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Postel, S. and B.Richter. 2003. Riv
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Stanford, J.A., J.V.Ward, W.J. Liss
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Culter, J.K. 1986. Water Chemistry.
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CHAPTER 10 - APPENDICES 10.1 Append
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The wavelet used is the symmlets wa
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explains, the energy plot shows the
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0 if no significant withdrawal Z =
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One advantage of using this regress
Page 148 and 149: Technical Memorandum January 22, 20
Page 150 and 151: Lecanto 1 & 2 #S Well Site Descript
Page 152 and 153: Figure 4. HSPF subbasins in the INT
Page 154 and 155: Most of the limestone mines located
Page 156 and 157: 3.1.3 Septic Tank Recharge in the S
Page 158 and 159: Figure 10. Groundwater grid in the
Page 160 and 161: Basso, R.J., 2004, Hydrogeologic Se
Page 162 and 163: 10.2 Appendices - Chapter 3 Appendi
Page 164 and 165: 10.3 Appendices - Chapter 4 Appendi
Page 166 and 167: Appendix 4-2 Data Sources Water qua
Page 168 and 169: Appendix 4-3 Water Quality Trend Gr
Page 170 and 171: Water Quality Trend Graphics, conti
Page 180 and 181: United States Department of the Int
Page 182 and 183: October 8,2008 Florida Fish and Wil
Page 184 and 185: Martin Kelly, Ph.D. Page 3 October
Page 186 and 187: Scientific Peer Review of the Propo
Page 188 and 189: Determining a low flow need during
Page 190 and 191: Current state water policy, as expr
Page 192 and 193: Spring, Twin Dees Spring and possib
Page 194 and 195: under varying flow regimes. The fir
Page 196 and 197: Weeki Wachee Rainfall, Springflow a
Page 200 and 201: Nevertheless, a major concern with
Page 202 and 203: system grid is not totally orthogon
Page 204 and 205: In a hydrodynamic model study, one
Page 206 and 207: analysis was rather cursory. The Di
Page 208 and 209: (taxa) richness in the WWRS. If the
Page 210 and 211: Freshwater Habitats Approximately 1
Page 212 and 213: ERRATA and EDITORIAL COMMENTS Page
Page 214 and 215: Page Paragraph Line Comment 14 Some
Page 216 and 217: Page Paragraph Line Comment 21 The
Page 218 and 219: Page Paragraph Line Comment 26 The
Page 220 and 221: REFERENCES Alber, M. 2002. A Concep
Page 222 and 223: Richter, B. D., J. V. Baumgartner,
Page 224 and 225: the regression equation used to pre
Page 226 and 227: and the three independent approache
Page 228 and 229: The Southwest Florida Water Managem
Page 230 and 231: the model in terms of tides, salini
Page 232 and 233: Attachment 1 - Comparison of salini
Page 234 and 235: Figure 1. Predicted drawdown (feet)
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