Alafia River Minimum Flows and Levels - Southwest Florida Water ...

development and implementation, the building block approach is viewed as a
reasonable means for ensuring the maintenance of similar, although dampened,
natural hydrographic conditions.
Conceptually, the approach used by the District for development of MFLs for the
upper Peace River (SWFWMD 2002) was consistent with the building block
approach. Available flow records were summarized and used to describe flow
regimes for specific historical periods. Resource values associated with low,
medium and high flows were identified and evaluated for use in the development of
MFLs for each flow range. Low minimum flows, corresponding to maintaining
instream flow requirements for fish passage and wetted perimeter, were proposed.
Medium and high minimum flows were not, however, proposed for the river segment,
due primarily to an inability to separate the effects of natural and anthropogenic
factors on flow declines. Nonetheless, methods were used to evaluate potential
ecological changes associated with variation in medium to high flows. The methods
focused on the inundation of desirable in-stream habitats and on floodplain
wetlands. Implicit in this approach was the concept that the three ranges of flow
(low, medium and high) were associated with specific natural system values or
functions.
For development of minimum flows and levels for the Alafia River, the District has
explicitly identified three building blocks in its approach. The blocks correspond to
seasonal periods of low, medium and high flows. The three distinct flow periods are
evident in hydrographs of median daily flows for the Alafia River (Figure 1-1).
Lowest flows occur during Block 1, a 65-day period that extends from April 20 to
June 24 (Julian day 110 to 175). Highest flows occur during Block 3, the 124-day
period that immediately follows the dry season (June 25 to October 27). This is the
period when the floodplain is most likely to be inundated on an annual basis;
although high flows can occur in early to mid-March. The remaining 176 days
constitute an intermediate or medium flow period, which is referred to as Block 2.
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