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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1998) is approximately 210 cfs which occurred in August of 1977. Calculations indicate that at
210 cfs the headwater over the dam is at elevation 4953.1, which is sufficient to divert at least
80 cfs into the canal as long as the Gunnison River flows are at or above 80 cfs. This low flow
scenario may not be physically practical given that the river could be concentrated on the
opposite bank or is naturally channelized in the center. This analysis assumes that, given
these conditions, which may be similar to the one year noted where HIC bermed the river to
direct flows into the canal, the ladder forebay gates are closed.
The average low flow over the record period is 650 cfs. This is determined by
averaging the lowest flow from each year from 1976 to 1999. The average August flows of
1200 cfs are also analyzed to insure depths and velocities remain within the design criteria
previously addressed. Results are presented in Section VII.
For pre-runoff conditions during fish migration, the average flows in late April and early
May are analyzed. The gage data indicates that the average daily flows vary from 2400 to
3500 cfs averaging approximately 3000 cfs. Flows in excess of 3000 cfs are also analyzed to
evaluate flood conditions for the 1.25-, 2-, 5-, 10-, 50- and 100-year events of which are
typically snowmelt runoff. The higher runoff events are also necessary to evaluate for stability
of the structure. These flows are summarized in Table 4.4.
4.5 Ditch Flows for Fish Screen Design
Flows for the screen analysis and by-pass channel are based on diversion records for
the Hartland Ditch, measured just downstream of the spill channel. Maximum daily flow
records are available from 1970. The average daily diversion is 40 cfs. The maximum daily
diversion is 90 cfs. For the purposes of this analysis the 90 cfs is not included since this flow
occurred only once since 1970. There is also one year with a maximum day of 70 cfs, however
all the other years have peak days that are less than 60 cfs. Thus for the fish screen design a
range of flows used to represent the daily flows is 40cfs and the maximum daily flows is 60 cfs.

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