The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
5.5.2 Methods and description of thermal model
A two-dimensional laterally averaged hydrodynamic and water quality model was
utilized to evaluate the effect of various flow scenarios on the thermal regime of the
Lower Hillsborough River. This work was performed by Janicki Environmental, Inc. for
the District. The model that used was CE-QUAL-W2, which was developed and is
supported by the US Army Engineer Waterways Experiment Station (Cole and Wells
2000). At a minimum, the model predicts water surface elevations, velocities, and
temperature at a specified time interval. The Hillsborough River temperature model
developed using the CE_QUAL-W2 software was previously calibrated as described in
Pribble et al. (2003). For the flow scenarios described in this report, the model was set
to output data at hourly frequencies.
The model provides predictions that are laterally averaged (across the entire water body
perpendicular to the direction of horizontal flow) so that the model integrates any lateral
differences in velocities, temperatures, or other modeled constituents. Given the narrow
width of the channel of the lower river, the District's LAMFE model indicated that threedimensional
modeling was not necessary to characterize circulation in the lower river
(Chen et al. 2001). The thermal model accommodates multiple inflows and time-varying
boundary conditions for surface elevation and temperature.
5.5.3 Model Data Requirements
The model requires the following input data:
• geometric data,
• initial conditions,
• boundary conditions, and
• hydraulic parameters.
The geometric data for the system being modeled were generated using the system
bathymetry from the District's LAMFE model. The bottom depth as well as the lateral
(cross-stream) width of the system at selected depths was estimated from the
bathymetry. The grid construct derived for the modeled system was also based on the
bathymetry from the LAMFE model, and was refined to provide the greatest resolution
in those regions of greatest importance to the objectives of the model study.
Initial conditions were input for temperatures and salinity concentrations, as these
variables can exert strong effects on water density and circulation. These conditions
were input either as a single value over the entire domain as a vertical profile of values
over all columns or as longitudinally and vertically varying fields over the model domain.
Initial conditions were also input for downstream tidal elevation. The model scenarios
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