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Section 5 Formulation of Alternative Plans

EAA Storage Reservoirs Revised Draft PIR and EIS February 2006

5-49

The team feels the Habitat Units, which encompass the habitat provided for a

diversity of wetland species, gained by these environmental features outweigh

the additional cost for creating those features.

5.4.4 Risk and Uncertainty

Risk and uncertainty associated with the project were considered, including the

adaptive assessment strategy.

5.4.4.1 Hydrologic Modeling

To formulate, evaluate, assess, and adaptively manage the CERP and this

project, regional hydrologic simulation models, the SFWMM and the Natural

Systems Model (NSM) were used. Both models use two-mile square grids with

resolution based on available spatially distributed data. These models have

been peer reviewed and represent the best available science and are considered

reliable for current decision-making processes (and have been repeatedly used to

support decision-making). However, there are inherent uncertainties in the

prediction of ecological benefits or impacts as well as the functions associated

with the reservoirs themselves.

These models depict general hydrologic conditions that are assumed to be

representative throughout the individual 4-square-mile area (or in the case of

Lake Okeechobee, the entire lake) grid cells that comprise the model. Therefore,

they may not be fine enough in their resolution to simulate minor hydrologic

changes that would result from variations in topography, soils, and vegetation

within the grid cells, but which may be significant in terms of ecological

response. Even if the hydrologic model shows differences in alternative plans in

relationship to hydrologic targets, it is often difficult to discern the ecological

magnitude of the relative differences between alternatives. Also, the relative

size difference between the reservoirs and the affected areas (Lake Okeechobee,

the St. Lucie and Caloosahatchee Estuaries, and WCA-3) is such that even large

changes in volume of water stored within the reservoirs cannot be easily seen

when water is spread over such a large area. Thus, with the combined effect of

the model grid size and scale of reservoirs compared with the ecosystem, the

model cannot readily discern the differences among alternatives.

The uncertainties in using these models to predict reservoir function relate to

the use of historical data, including:

1. Failure to be filled by the time of commissioning.

2. Mean flow below what has been expected.

3. Clustering of wet and dry years, especially occurrence of a prolonged dry

period.

4. Faster reservoir sedimentation than expected.

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