The Determination of Minimum Flows for Sulphur Springs, Tampa

3.5 Dissolved oxygen concentrations in the spring run and response to
withdrawals from the spring pool. ...................................................... 3-9
3.6 Other water quality characteristics of the spring run...................... ..3-10
3.7 Biological habitats and communities in the spring run..................... 3-11
3.7.1 Benthic habitats............................................................................... 3-11
3.7.2 Shoreline vegetation........................................................................ 3-11
3.7.3 Benthic macroinvertebrates............................................................. 3-12
3.7.3.1 1997 Macroinvertebrate survey ....................................................... 3-12
3.7.3.2 Invertebrate collections from 2000 to 2003...................................... 3-13
3.7.3.3 Results of FWC qualitative samples ................................................ 3-14
3.7.3.4 Percent composition in various habitats ......................................... 3-17
3.7.3.5 Quantitative samples from May 2000, November 2001,
and December 2003 ........................................................................ 3-18
3.7.3.6 Possible factors affecting changes in the macroinvertebrate
community ....................................................................................... 3-21
3.8 Fish populations in the spring run.................................................... 3-22
3.9 Relationships of Sulphur Springs discharge to the hydrology, water
quality and ecology of the Lower Hillsborough River....................... 3-26
3.9.1 Hydrology of the Lower Hillsborough River ..................................... 3-26
3.9.2 The effects of flows from Sulphur Springs on salinity distributions in the
Lower Hillsborough River ................................................................ 3-31
3.9.2.1 Empirical salinity data plots ............................................................. 3-33
3.9.2.2 Hydrodynamic salt transport model of the river ............................... 3-36
3.9.3 Relationships of freshwater inflows on dissolved oxygen
concentrations in the lower Hillsborough River................................ 3-38
3.9.4 Effects of low flows on salinity distributions and dissolved oxygen
concentrations between the dam and Sligh Avenue........................ 3-42
3.10 Biological characteristics of the Lower Hillsborough River and relation
to the management of Sulphur Springs ........................................... 3-48
3.10.1 Intertidal vegetation ......................................................................... 3-48
3.10.2 Benthic macroinvertebrates............................................................. 3-49
3.10.3 Fishes.............................................................................................. 3-50
3.11 Thermal characteristics of the spring run and the lower river and use
by cold sensitive species ................................................................. 3-52
3.11.1 Thermal characteristics of Sulphur Springs pool and run ................ 3-53
3.11.2 Thermal characteristics of the Lower Hillsborough River................. 3-56
3.11.3 Vertical and diurnal variations in river water temperatures .............. 3-60
3.11.4 Temperature variability and relation to biological use...................... 3-60
ii
DRAFT
Chapter 4 – Technical Approach for Determining Minimum Flows for Sulphur
Springs
4.1 Overview ........................................................................................... 4-1
4.2 Consideration of structural alterations to the determination of minimum
flows .................................................................................................. 4-1
4.3 Consideration of seasonal variations of springflow and relationships to
flows from the Hillsborough River reservoir ....................................... 4-2
4.4 Selection of management goals and ecological indicators
for evaluating the effects of reduced flows ........................................ 4-3