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

flow reductions that would result in more than a 15% reduction in the number of
days of inundation during Block 3. Analyses of similar decreases in the number
of days a range of flows at the USGS Lithia gage were exceeded was also used
to identify a percent-of-flow reduction for the block. These percent-of-flow
reductions were considered to be limiting factors and used for development of a
prescribed flow reduction (PFR3) for Block 3.
4.9 Prescribed Flow Reductions for Lithia Springs Major and
Buckhorn Springs Main
Because the range of flows or discharge from Lithia Springs Major and Buckhorn
Springs Main is substantially less than that of the Alafia River (e.g., see Figures
2-18, 2-28 and 2-31 ), prescribed flow reductions were evaluated for application
on a year-round basis rather than for seasonal blocks. To develop prescribed
flow reductions for both springs, changes in the availability of aquatic habitat for
selected fish species and macroinvertebrate populations were evaluated using
the Physical Habitat Simulation Model (PHABSIM). Flow requirements for
recreational swimming at Lithia Springs Major were also considered to determine
whether this factor could be used to identify a prescribed flow reduction.
4.9.1.1 PHABSIM – Application for Lithia Springs Major and Buckhorn
Springs Main (Buckhorn Creek)
PHABSIM was used to evaluate potential habitat changes associated with
variation in flow in the Lithia Springs Major run and in Buckhorn Creek,
downstream from Buckhorn Springs Main. Simulations were conducted for
various life-history stages of spotted sunfish, largemouth bass, bluegill and for
macroinvertebrate community diversity. Maximum flow reductions that resulted
in no more than a 15% reduction in habitat from historic conditions were
determined to be limiting factors. These factors were used for consideration in
the development of prescribed flow reductions for the springs.
For the Lithia Springs Major run, PHABSIM data were collected at three crosssections
at a single site between April and July of 2004. Reconstructed flows
from 1983 through 2002 (see Section 2.3.4.3.2) were used for the time series
component of the analysis. For the sampled site on Buckhorn Creek, field-data
were collected at thee PHABSIM cross-sections in July and August of 2004.
Because the Alafia River controls water level in Buckhorn Creek when river stage
rises, due to flow events or tidal influences, sampling was conducted with
consideration of the local tide schedule. Reconstructed low flows from Buckhorn
Springs Main from 1988 through 2002 (see Section 2.3.4.3.2) were used for the
time series component of the analysis. A second time series analysis was also
performed for Buckhorn Springs using the flow record for Buckhorn Creek.
4-26