The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
Figure 3-16 illustrates salinity in the river with no flow at the dam and average flow from
Sulphur Springs uncorrected for withdrawals (31 cfs). Salinity near Rowlett Park Bridge
(km 16) is between 6 and 7 ppt, which is similar to the long-term median value for that
site in the EPCHC data set (Figure 3-14). This figure also shows a shallow lens of low
salinity water at the surface near Sulphur Springs. Similar to the empirical box and
whisker plot (Figure 3-13), modeled surface salinity values there (4-5 ppt) are lower
than at Rowlett Park. The river near Sulphur Springs is highly stratified, as bottom
salinity values at 10 to 11 ppt. The reverse salinity gradient in surface waters and
pronounced salinity stratification in the vicinity of Sulphur Springs is a distinct
characteristic of the river during no-flow conditions.
The next three figures show the effects of different flows of fresh water from the
reservoir spillway on salinity in the river. A flow of 10 cfs of river water creates a zone of
water less than 1 ppt and pushes the 7 ppt isohaline (line of equal salinity) on the river
bottom to kilometer 13.4 near the dam (Figure 3-17). A flow of 60 cfs creates a
freshwater zone of