Review of the St. Johns River Water Supply Impact Study Report 3 (2010) / Chapter Skim
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Chapter 3 Model Limitations and Other Recommendations
Chapter 3 Model Limitations and Other Recommendations
Pages 24-30
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From page 24... ...
In addition, the increased amounts of urban stormwater runoff that would be a major source of water compensating for the WSIS withdrawals have important implications with regard to both water quality in the St. Johns River and on water quantity -- flow and stage, as predicted by the hydrologic modeling.
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From page 25... ...
to 2009-2010 land use conditions and 2009-2010 observed rainfall and streamflow to provide a basic understanding of how the model behaves for a case outside the calibration range that has observed data. DEPENDENCY ON URBANIZATION AND RESULTING STORMWATER FLOW A key problem inherent in water budget studies on urbanizing catchments is that increasing impervious surfaces tends to decrease water fluxes through the vadose zone and increase surface water flow.
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From page 26... ...
. In general, such systems are moderately effective in removing suspended matter by simple settling processes, but they do a poor job removing pollutants present in the dissolved state or sorbed onto colloidal material.
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From page 27... ...
There is consequent deterioration of stream biogeochemical function and declines in species diversity and indices of biotic integrity in such streams. These effects are compounded by human actions to improve drainage, such as channel straightening and lining to reduce friction, increasing flow capacity, and stabilizing channel position.
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From page 28... ...
APPLICABILITY OF HSPF TO WETLANDS HYDROLOGY The HSPF model that the District is using to predict hydrological changes for the different water withdrawal scenarios has limited value for modeling wetlands because HSPF output does not include water table elevation data. Essentially HSPF models water infiltration to the active groundwater, and this water either becomes base flow to the river or is "sunk" to the P R E P U B L I C A T I O N C O P Y
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From page 29... ...
To help address the above issues and shortcomings of HSPF with regard to wetlands, the wetlands workgroup is adopting the Hydroperiod Tool from the South Florida Water Management District. This tool estimates daily water depth over an area by subtracting the ground surface elevation (obtained from a digital elevation model or DEM)
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From page 30... ...
In the committee's view, this is the only way to make the STELLA modeling output spatially explicit. Because the committee views this as an ambitious undertaking, it is unlikely to be an optimal use of staff resources at this point in the project, and may distract from the other efforts described above.
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