9593

• UCREFRP Catalog Number: 9593
• Author: Tetra Tech Inc.
• Title: Concept Development Report Hartland Diversion Dam Fish Passage Structure Delta, Colorado.
• USFW Year: 2000.
• USFW - Doc Type: Grand Junction, CO.
• Copyright Material: NO

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calibration of the model. Cross section 1900 is the most upstream section located
approximately % miles upstream of the diversion structure. The most downstream cross
section is 100 and is located 2 % miles below the diversion structure. In addition to the cross
section surveys, Reclamation prepared a detailed topographic survey at the Hartland headgate
and dam structure.
The hydraulic analysis for the development of the alternatives is based on the
assumption that the water levels are controlled by the top of the dam and the rock cribbing
along the dam does not have a permeability that results in a significant flow capacity.
5.1 Model Calibration, hydraulic parameters
Manning's n values (roughness coefficient) are estimated from inspection of the
channel. The n values within the channel banks are further refined by calibration of the HEC-
RAS model based on surveyed water surface elevations. Surveyed water surface elevations
are utilized as the downstream boundary conditions and for comparison with the calibration
model. Flows utilized in the calibration run are from the USGS gage information at Delta
recorded at the time of the water surface elevation surveys. For n-values above the banks,
where surveys and calibration runs are not possible, values from the Delta County FIS are
used. The flow change option within the HEC-RAS steady flow data editor is used to model a
flow intake of 60 cfs at the Hartland headgate. The inline weir editor within HEC-RAS is used
to model the diversion as a weir using a weir coefficient of 2.64.
Manning's n values in the model are shown in Table 5.1. These selected n values are
within the range of values used by FEMA for the hydraulic analysis of the Gunnison River for
preparation of the Delta County FIS. The FEMA values are included in Table 5.1 for
comparison purposes. A typical coefficient of contraction of 0.1 and coefficient of expansion of
0.3 is also used in the HEC-RAS model. The calibration run and results are presented in
Appendix C.

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