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

5.8 Short-Term Compliance Standard for Buckhorn Springs Main
For the Buckhorn Creek/Buckhorn Springs Main system, PHABSIM analyses
yielded a prescribed flow reduction of 15% for all months when run using
Buckhorn Spring flow data, corrected for withdrawals. When using Buckhorn
Creek flow data, corrected for withdrawals, the prescribed flow reduction was 5%
for July through October, and 10% for the rest of the year except March when a
20% reduction is appropriate. Buckhorn Spring Main accounts for a clear
majority of the flow in Buckhorn Creek a large majority of the time. Both flow
records generate answers that are similar. A 15% reduction in spring flow
compared to a 10% reduction in creek flow does not differ greatly.
Minimum flow requirements for the estuarine portion of the Alafia River are
currently being evaluated by the District. Because compliance with minimum
flows and levels for the estuary may be contingent on flow or discharge from
Buckhorn Spring, we recommend that establishment of a minimum flow for the
spring be deferred until analyses for the estuarine segment of the Alafia River are
completed. The report for the estuarine portion of the Alafia River will include
recommendations for minimum flows for Buckhorn Spring and will consider the
PHABSIM analysis already performed.
5.9 Compliance Standards and Proposed Minimum Flows for
the Freshwater Segment of the Alafia River
We have developed short-term compliance standards that comprise a flow
prescription for preventing significant harm to the Alafia River. Compliance
standards were developed for three blocks that represent periods of low (Block
1), medium (Block 2) and high (Block 3) flows at two USGS Alafia River, FL gage
sites (Tables 5-6). During Block 1, which runs from April 20 to June 24, the
allowable withdrawal from the Alafia River that may be withdrawn for
consumptive-use is 10% of the daily flow as measured at the USGS Lithia gage,
once flows exceed 66 cfs. During Block 1, it is also proposed that no withdrawals
be allowed when flows at the Lithia gage are below 59 cfs and that withdrawals
when flows at the site are between 59 and 66 cfs not be allowed to lower the flow
below 59 cfs. During Block 2, which extends from October 28 of one year to April
19 of the next, withdrawals of up to 15% of the daily flow at the Lithia gage may
be allowed, with the exception that withdrawals should not be allowed to reduce
the flow to less than 59 cfs. During Block 3, which extends from June 25 to
October 27, withdrawals should be limited to a stepped flow reduction of 13%
and 8% of flows, with the step from 13% to 8% occuring at 374 cfs at the Lithia
gage. Proposed Block 3 reduction also must comply with the low flow threshold
and assure that withdrawals not reduce the flow to less than 59 cfs at the Lithia
gage.
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