Weeki Wachee River System Recommended Minimum Flows and ...

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Nevertheless, a major concern with the salinity regression equation is that the salinity at the river mouth is not included as an independent variable. Although the analysis described in the District’s report concluded that flow from Weeki Wachee Spring did not have a significant impact on salinity at the river’s mouth near Bayport, the salinity level in the river system is obviously dependent on the salinity level in the nearshore Gulf waters. This is an important boundary condition in the numerical model, described below, which was applied to assess the impact of flow reductions on the thermal regime. The regression equation for the location of salinity isohalines is used extensively in determining what flows result in a 15% reduction of various biological resources. It seems clear to the Panel that boundary salinity at the river mouth should have been included as an independent variable in the predictive equations. Application of the EFDC Numerical Model to WWRS The Environmental Fluid Dynamics Code (EFDC), a three-dimensional finite difference hydrodynamic model, was applied to the WWRS by Applied Technology and Management, Inc. (ATM 2007). The purpose of the modeling effort was to determine the level of flow reduction that would result in a 15% reduction of the thermal regime that is tolerable by the West Indian manatees. Manatee habitat refuge areas and volumes were defined as waters that met the following criteria: - Daily average temperatures were greater than 20 º C over a critical 3-day period - Passage for manatee was available upstream based upon District defined minimum depths When conducting a review of numerical modeling, the review is initially focused on the following questions: - Are the mathematical model’s physics adequate for its intended use? - Is the numerical grid adequate to resolve the spatial component? - Are sufficient data available for model calibration and validation? - Has model calibration and validation been achieved? 16
A Task Committee of the American Society of Civil Engineers (ASCE) is currently in the process of publishing a monograph describing model verification, calibration and validation. Verification is the process of demonstrating that the proper physical equations are correctly solved and that the computer code is free from errors. The EFDC is a well known model that is supported by the EPA and contains all the basic physics required to make hydrodynamic computations in estuaries and coastal areas. As such, users can be confident that the EFDC is a well-verified numerical hydrodynamic model. Calibration and validation are part of the user’s application of the verified model’s code to a particular water body. Specifically, calibration is the process of varying model parameters so that the simulation matches the observed data. In the strictest sense, validation is then the process of taking the calibrated model and applying it to a different data set in order to demonstrate its accuracy using the same model parameters set in the calibration phase. In practice, the demarcation between calibration and validation can become a little fuzzy. If the model is calibrated to a relatively short data set (perhaps a month or two) that does not cover a period in which all processes governing the hydrodynamics of the water body occur, the model should be applied to a separate data set to make sure it is still working correctly. However, if the model simulation covers a long enough period of time (i.e., many months or even years) during which virtually all processes occur, if the model’s parameters are within acceptable ranges, and if the parameters stay the same during the long simulation period, the case can be made that both calibration and validation have been achieved. The Panel’s comments on the calibration and validation of the EFDC model, as applied by ATM to the WWRS, are given below. These observations are based on results presented in the consultant’s report “Impacts of Withdrawals on the Thermal Regime of the Weeki Wachee River” (ATM 2007). The ATM report shows the curvilinear numerical grid in the horizontal plane (Figure 4-1) and with the river’s bathymetry displayed on the grid (Figure 4-2). Strictly speaking, the EFDC is only applicable on grids that are completely orthogonal. It can be seen that the Weeki Wachee 17
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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
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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 198 and 199: 6.0 Discharge:Precipitation (cfs/in
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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