The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
3
Run_Riv_Stg.grf
Water Surface Elevation (ft, NGVD)
2
1
0
-1
Stage (ft, NGVD) Jan. 14 - 21, 2001.
Sulphur Springs
Hillsborough River
-2
1/14/01
1/15/01
1/16/01
1/17/01
1/18/01
Date
1/19/01
1/20/01
1/21/01
Figure 3-2. Time series graph of water levels in upper spring run
and river near the moth of the spring during a period of normal flow
from the spring pool (January 14 – 21, 2001).
By reducing flow from the spring, withdrawals can affect the elevation of water in the
spring run at low tides. The stage duration curve for the spring run in Figure 3-1 was
based on all flows recorded from the spring pool since May 1999. Two stage duration
curves for the spring run are overlain in Figure 3-3 for periods when there are very low
flows (20 cfs) from the spring pool. The curves are similar
above 0.6 feet, but diverge at lower water surface elevations. During normal flows,
water levels in the spring rarely go below 0.3 feet; whereas during low flows,
approximately 25 percent of water levels drop are less than 0.0 feet. The opening in the
weir restricts discharge from the upper spring run, and at low tide, acts to holds water
levels higher as flows from the spring pool increase. Compared to normal flows (Figure
3-2), Figure 3-4 shows that low-tide water levels in the run fall to lower values during of
periods of low flow (3.5 cfs) from the spring pool. The plots presented in Figures 3-2 and
3-4 were generated for periods when there were no flows from the Hillsborough River
Reservoir to remove the confounding effect of high flows in the river on water levels in
the spring run.
3 - 3