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

TABLE 4.4 DESCRIPTIONS OF DESIGN FLOW. GUNNISON:RIVERAT HARTLAND DIVERSION DAM

Flow Description
210 cfs Lowest flow in period of record.
350 cfs 90% exceedence of low flow in August. Lowest flow analyzed for ladder design
650 cfs Average low flow used to establish ladder inverts.
1 ,200 cfs Average flows in August
3,000 cfs Average flows last week of April (anticipated pre-runoff migration period)
3,460 cfs 1.25-year flood event
6,470 cfs 2-year flood event
11,600 cfs 5-year flood event
13,500 cfs 10-year flood event (FIS)
18,700 cfs 50-year flood event (FIS)
21,200 cfs Regulatory 1 OO-year flood event (FIS)

HIC reports that they typically spill approximately 10 cfs (HIC 2000) at the spill channel,
which indicates that the amount of water diverted out of the Gunnison River at the headgates is
50 to 70 cfs. To provide sufficient depth and velocities for the fish in the by-pass channel, an
additional 10 cfs is added to the spilled amount of flow. This requires an additional 10 cfs at
the headgate to the ditch. Thus the screen is designed for 40 to 60 cfs with 20 cfs being
diverted into the spill/by-pass channel.

v. HYDRAULICS
To develop design parameters and evaluate the impacts of a fish passage structure on
the hydraulic conditions at the Hartland diversion, a hydraulic model was developed using the
Army Corp of Engineers HEC-RAS program, version 2.2 (USACE 1997). A total of 19 river
cross sections were surveyed upstream and downstream of the diversion structure by

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