Review of the St. Johns River Water Supply Impact Study Report 1 (2009) / Chapter Skim
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3 Hydrodynamic and Hydrologic Modeling
3 Hydrodynamic and Hydrologic Modeling
Pages 27-42
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From page 27... ...
Hydrodynamic and hydrologic changes are the underlying drivers of ecological change resulting from surface water withdrawals; therefore, the hydrologic effects must be predicted accurately to understand the probable ecological effects. An overall project goal is to develop "quantitative response functions" that link river water withdrawal to hydrologic responses and ecological effects.
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From page 28... ...
Johns River, so future modeling will need to examine how sea level rise may affect upstream propagation of reverseflow tidal effects. The possibility of climate-change induced sea level rise providing a nonlinear interaction with surface water withdrawals cannot be neglected, and the hydrodynamic models the District has should be adequate for this analysis.
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From page 29... ...
Recommendations for Phase II Surface Water Studies Based on the committee's analysis of the Phase I report and a preliminary review of the Phase II work plan, the committee has several recommendations for improving the District's Phase II surface water studies. Specifically, the District should (1)
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From page 30... ...
However, the choice of model configurations and boundaries should be focused on representing the critical physical and ecological effects of surface water withdrawal rather than simply by the availability of pre-existing models and methods. To some extent, the Phase II work plan shows better integration between the hydrodynamics and hydrology workgroup and the ecology workgroups than the Phase I studies, although there is still limited communication across disciplinary boundaries.
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From page 31... ...
Johns River. Thus, in conjunction with improving the existing models, the District should develop a model to represent how surface water withdrawals affect the upstream wetlands and groundwater supply.
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From page 32... ...
Thus, there is the potential for significant amplification of the upstream salt wedge excursion if surface water withdrawals cause the salinity front to be pushed further upstream from the bridge (i.e., reducing mixing)
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From page 33... ...
Range of modification for each variable changed, 5. Error measures of some calibrated variables in un-calibrated and calibrated simulations, 1 There is some confusion in the Phase II work plans regarding the use of the word "verification" for the hydrodynamic models.
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From page 34... ...
For example, sensitivity analyses for the vertical grid resolution cannot be based solely on water surface level because it is possible for a calibrated model to create an excellent and robust model of the water surface elevations that is insensitive to the choice of the vertical grid resolution, whereas modeling the upstream motion of salinity may be extremely sensitive to this parameter. The District should demonstrate the sensitivity of each model to various choices in the model setup.
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From page 35... ...
John River, vertical gradients of salinity and horizontal upstream salinity excursions in the lower river, and the effects of bridges and sea level rise. Third, the District should document model calibration and sensitivity and develop methods to quantify model uncertainty on the time/space scales at which ecological effects occur.
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From page 36... ...
(Not Used in Phase I CIA) LFA Note: SAS = surficial aquifer system, UFA = upper Floridan aquifer, and LFA = lower Floridan aquifer.
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From page 37... ...
includes a change with respect to previous versions of the model in its lateral boundary conditions and recharge and evapotranspiration calculations. The newest design of the NCF includes all groundwater withdrawals for the 1995 conditions in the surficial aquifer system and upper Floridan aquifer.
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From page 38... ...
Sea level change is addressed in the Phase I report only in terms of the projected increase in salinity of the lower river. Adequacy of Groundwater Inputs into Surface Water Models The above limitations have direct consequences for the District's hydrodynamic modeling because the groundwater model results (i.e., groundwater base flow from the aquifer)
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From page 39... ...
Hydrodynamic and Hydrologic Modeling 39 30 15 0 30 Miles St John's River Basin UFA Chloride Concentration 0-50 50-250 250-1000 1000-15000 ´ Lake Okeechobee FIGURE 3-2: Generalized Salinity Map, Layer 2, ECFT Model. SOURCE: SJRWMD Staff.
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From page 40... ...
ECFT includes a Wetlands package, developed by the South Florida Water Management District and the Center for Hydrology and Water Resources at Florida Atlantic University (Restrepo et al., 1998)
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From page 41... ...
The ECFT grid spacing (see Table 3-1) balances the need for resolution of surface water features and local impacts with data availability.
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From page 42... ...
Summary of Groundwater Hydrology In order to improve the groundwater modeling in Phase II of the WSIS, the District should consider using the ECFT transient model, which includes wetlands processes, and a cross-sectional density-dependent model. These models will be critical to understanding how groundwater flow and salinity flux into the river will vary with water withdrawals.
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