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

1) maintenance of minimum water depths in the river channel for fish
passage and recreational use;
2) maintenance of water depths above inflection points in the wetted
perimeter of the river channel to maximize aquatic habitat with the least
amount of flow;
3) protection of in-channel habitat for selected fish species and
macroinvertebrate assemblages;
4) inundation of woody habitats including snags and exposed roots in the
stream channel; and
5) maintenance of seasonal hydrologic connections between the river
channel and floodplain to ensure floodplain structure and function.
These goals are consistent with management goals identified by other
researchers as discussed in Chapter 1. The rationale for identifying these goals
and the habitats and ecological indicators associated with the goals are
addressed in subsequent sections of this chapter. Field and analytical methods
used to assess hydrologic requirements associated with the habitats and
indicators are presented in Chapter 4, and results of the minimum flows and
levels analyses are presented in Chapter 5.
3.3.1 Fish Passage and Recreational Use
Ensuring sufficient flows for the passage or movement of fishes is an important
component of the development of minimum flows. Maintenance of these flows is
expected to ensure continuous flow within the channel or river segment, allow for
recreational navigation (e.g., canoeing), improve aesthetics, and avoid or lessen
potential negative effects associated with pool isolation (e.g., high water
temperatures, low dissolved oxygen concentrations, localized phytoplankton
blooms, and increased predatory pressure resulting from loss of habitat/cover).
Tharme and King (1998, as cited by Postel and Richter 2004) in developing a
"building block" approach for South African rivers listed the retention of a river's
natural perenniality or nonperenniality as one of eight general principles for
managing river flows. For many rivers within the District, flows and
corresponding water depths adequate for fish passage are currently or were
historically maintained by baseflow during the dry season. For example, in the
upper Peace River, historical flows were sufficient for maintaining a naturally
perennial system and flow was sufficiently high during the low flow season to
permit passage of fish along most of the river segment (SWFWMD 2002).
Recent flows in the upper Peace River have not, however, been sufficient for fish
passage much of the time. Historic flows in other District rivers, such as the
Myakka River were probably intermittent, historically, but have increased in
recent years. Evaluation of flows sufficient for fish in support of minimum flows
development may, therefore, involve consideration of historic or recent flow
conditions with respect to perenniality and the likelihood of fish passage being
maintained naturally (i.e., in the absence of consumptive water use).
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