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Section 5 Formulation of Alternative Plans

EAA Storage Reservoirs Revised Draft PIR and EIS February 2006

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performance measures fully characterize all of the attributes of ecosystem

functions, since the analytical tool for system-wide effects is a hydrologic

simulation model. This assumption results in some uncertainty with respect to

the evaluation of system-wide ecological responses because not all ecological

attributes can be simply reduced to hydrologic terms. However, to reduce some

levels of uncertainty, the hydrologic performance measures have been related to

certain ecological attributes by the Ecological Sub-team.

Another uncertainty exists in the correlation between small hydrologic changes

seen in the outputs of a regional model, and the ecological significance of those

changes. The hydrologic change in a model grid cell, indicator region, or

geographic sub-region that may result from individual projects is typically small

in relative magnitude. Although target conditions are established for these

hydrologic performance measures, the scientists on the ecological subteam have

determined that the relatively small differences between alternatives (difference

of less than 10%) for some of the performance measures does not lend itself to

meaningful ecological differences. Therefore, there is some uncertainty in

predicting the extent of system-wide change in ecological attributes due to

relatively small differences in the hydrologic changes associated with

incremental implementation of individual CERP projects.

To reduce the uncertainty in evaluating relative differences among the

alternatives, the ecological subteam accepted only those scores of differences of

at least 10 percent. In light of these uncertainties, the predicted ecological

benefits should be considered in terms of trends and relative differences among

the alternatives.

5.4.4.4 Variability of Ecological Response Time

Determining the individual variable spatial response to hydrologic change of

each attribute within an ecosystem is uncertain at best. Each of the conceptual

ecological models (CEMs) that are the basis for the system-wide hydrologic

performance measures encompass multiple ecological attributes (for example,

oyster beds, submerged aquatic vegetation, and fish populations are all

attributes of the St. Lucie Estuary CEM). Each attribute may vary

independently in the response time to changes in hydrology. Changes in

freshwater wetland vegetation will be gradual and increase over time as

hydropatterns and hydroperiods within the natural system are altered; changes

in estuarine vegetation typically occur on a shorter time scale. Depending on the

life cycles, different resources in the natural system will differ in ecological

response time.

Also, different aspects of wildlife responses to hydrologic change occur over

different time scales. For example, snail kite nesting and foraging is dependent

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