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

2.3.4.3.2 Discharge from Lithia Springs Major and Buckhorn Springs Main
Discharge from Lithia and Buckhorn Springs is measured manually; daily values
like those for the USGS gage sites on the Alafia River are, therefore, not
available. Fortunately, Tampa Bay Water measures discharge at both locations
on a regular basis (weekly and sometimes more often). For this report, daily flow
records were constructed by interpolating between available flow values and
adjusting measured flows by including reported withdrawal volumes.
Withdrawals at both spring sites are reported as monthly totals; within each
month, monthly totals are distributed evenly between days of the month.
In comparison to USGS maintained gage sites on the Alafia River and its major
tributaries, the flow records for Lithia Springs Major and Buckhorn Springs Main
are relatively short. The Buckhorn Springs record begins in 1987 with a four-year
gap extending from January 1997 to August 2000. The Lithia Springs Major
record begins in March 1983 and extends to present. The Lithia Springs Major
record can be extended somewhat by using periodic flow measurements made
by the USGS. USGS measurements have been made on about a quarterly basis
since 1966 with infrequent measurements (much less than one per year) in prior
years.
Lithia Springs Major Discharge
The reconstructed daily flow from Lithia Springs Major (referred to hereafter
simply as Lithia Springs) is shown in Figure 2-27. Discharge from Lithia and
Buckhorn Springs is not well correlated with Floridan aquifer well levels. Various
workers have therefore concluded that the springs are connected to a local
conduit that is not directly influenced by the regional potentiometric surface
(Jones and Upchurch 1993, Basso 1998, SDI 2002). A poor relationship
between stage and discharge has also been reported for Lithia Springs (see
Figure 2-28). Close inspection of the data, however, indicates that there is a
good relationship (R 2 =0.???) between stage and discharge (as should be
expected) when flows in the Alafia River are low (Figure 2-28). The correct
interpretation of the stage to discharge relationship observed for Lithia Springs is
that once the stage of the Alafia River increases beyond a certain point, the river
essentially controls stage in the Lithia Springs run and in the pool. The data
suggest that there is a fairly well defined relationship between stage and
discharge at Lithia Springs until the Alafia River discharge as measured at the
Lithia gage exceeds approximately 70 cfs. The stage at Lithia Springs is under
control of the river for much of the year.
The daily flows for Lithia Springs are shown in Figure 2-27. Despite the extreme
low flows encountered during the period of record drought in 2000, a Kendall’s
tau test on daily flows since 1983 indicates a statistically significant increasing
trend in flows for Lithia Springs (p = 0.0000; slope = 0.00245, Figure 2-29).
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