The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
medians rise to near -0.2 feet. The largest break in the distribution of daily minimum
stage values, however, occurs near 17-18 cfs, where the medians and the inter-quartile
ranges all rise dramatically. Above 17 cfs, the median values daily minimum stage
generally remain above 0.2 feet, or slightly half a foot higher than the minimum stages
recorded under very low flows.
Figure 5-10. Box and whisker plot of daily minimum water levels in
the upper spring run in 1 cfs flow classes from Sulphur Springs pool.
These results indicate that at as flows decline below 17 cfs a greater amount of the run
bottom is exposed at low tides, changing these areas from sub-tidal habitats (always
submerged) to inter-tidal habitats (exposed at low tide). This would have implications for
some largely sessile organisms that require continuous inundation. Highly motile
animals, such grass shrimp or fish, can migrate with the tides and utilize these areas as
water levels rise and fall. The total amount of submerged habitat in Sulphur Springs is
about 0.3 hectares (0.75 acres) at a water level of 0.0 feet, and 0.27 hectares (0.67
acres) at a water level of –0.4 feet (Figure 2-8). Thus, reduction of daily minimum stage
from medium flows (17 to 24 cfs) to very low flows changes about 10 percent of the subtidal
habitat in the run to inter-tidal habitat. However, this reduction occurs in the shallow
margins of the spring pool, where the diversity of aquatic macroinvertebrates is the
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