The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
CHAPTER 3
ECOLOGICAL RESOURCES OF SULPHUR SPRINGS AND THE
LOWER HILLSBOROUGH RIVER
3.1 Introduction
Sulphur Springs functions ecologically as a distinct spring run and as an important
component of the Lower Hillsborough River system. The plants and animals that inhabit
the spring run and the nearby areas of the river are closely related to the flow and water
quality of the spring discharge. In that regard, the hydrologic and water quality
characteristics of the spring run are described first below, followed by a discussion of
the ecological characteristics of the spring run and how the spring influences the water
quality and ecology of the Lower Hillsborough River.
3.2 Salinity and water level records in the spring and river system
Historical physical and water quality data for the spring run are scarce. Data collected
over the last several years, however, demonstrate how water levels, salinity, and water
temperatures in the spring run respond to changes in flow from the spring pool. As part
of these studies, a series of continuous recorders were installed by the USGS in the
spring and lower river system in the late 1990s. Two recorders that measure
temperature and specific conductance every fifteen minutes were installed in the upper
spring run and at the spring mouth in May 1999. The recorder in the upper run, which
also measures water levels, is located on the channel bottom near the south shore of
the run about 100 ft (30 m) upstream of the weir (Figures 2-4 and 2-5.D). The other
recorder is located on the channel bottom at the footbridge at the mouth of the run.
Specific conductance data from these recorders can be used to calculate approximate
salinity values, although actual salinity will be dependent on the ionic composition of the
water. For better comparison to the lower river, calculated salinity values in the spring
run are discussed below rather than specific conductance.
Recorders were also installed by the USGS at five locations in the Lower Hillsborough
River: at the bridge at Rowlett Park Drive (km 15.6); near Hanna's Whirl (km 14.5);
Nebraska Avenue (km 13.0); Interstate 275 (km 12.6); and at the mouth of the river at
Platt St (Figure 2.1). The recorder with the longest period of record is at Rowlett Park
Drive, where the current series of records began in 1996. Data collection at the
remaining sites began between 1999 and 2002. Water level, salinity (calculated from
specific conductance) and water temperature data from these recorders are discussed
in various sections of this report.
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