WSP04165

• File Number: 8240.200.10.B
• Description: UCRBRIP - Riverine Fish Flow Investigations
• Basin: Colorado Mainstem
• Date: 6/1/2003
• Author: CDOW
• Title: Riverine Fish Flow Investigations 2003
• Water Supply Pro - Doc Type: Publication

Colorado River - IS-Mile Reach

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The IS-Mile Reach of the Colorado River extends from Palisade, Colorado (RM
185), downstream to the confluence of the Gunnison River at about RM 170 (Figure 4).
The Colorado River Recovery Program (Osmundson et al. 1995) considers the IS-Mile
Reach important for endangered fish recovery. Flows are an issue because of two major
upstream diversions that divert flow from the river during the irrigation season (April I to
November I). The Government Highline diversion is located in lower Debeque Canyon
(RM ] 93.7) and the Highline canal has a capacity of 1620 cfs. The Grand Valley
diversion dam is at RM 185.4. The Grand Valley canal has a capacity of640 cfs.

A USGS gage, which is located about 0.4 krn downstream from the intake for the
Grand Valley canal (Figure 4), began operation in 1990. Flows at the Palisade gage are
typically 1200 to 1600 cfs less than above the divcrsion structurcs in spring and summcr.
Winter (Novcmber to March) flows in the I 5-Milc Rcach do not appcar to create fishery
concerns. Flows rccorded at the Cameo gage (RM 199.9) appear to be at least at pre-
devclopment levcls or higher duc to senior water right calls at the Shoshone power plant
in Glenwood Canyon. Also there can be additional releases for power gencration from
Green Mountain Rescrvoir (Per comm. Karen Flogequest (USBR). Flows recorded at the
Palisade gage are usually higher than at Cameo betwecn November and April bccause
Plateau Creek joins the rivcr at RM 193.3. Pitlick (1999) determined bankfull flow to bc
near 22000 cfs for thc IS-Mile Reach.

Thcre are two study sites in the IS-Mile Reach. In 1999, bed topography was
mapped from thc boat launch at Corn Lake (RM 177.5) downstream to RM ] 75.3 (Figurc
4). This station is named the Com Lake Site. The Com Lake site length, which is 3.9 krn
long and has an average width of 55.2 m at a flow of 1400 cfs, was electro-fished in
1999.2000 and 2001. The river in this section includes five small backwaters. Flow is
generally confined within the main channel as opposed to a braided channel (Figure
AF7).

The Clition Site was added in 2000. This site is about 300 m upstream from the
Com Lake site. The Clifton site is from RM 177.7 to 180.4 and has a total length of 4.2
krn. In this section, the river has split flow in two large sections of the channel. There is
an old diversion structure located at RM 179.7. The dam backs up water along the north
shoreline. There is a large backwater at lower flows. Smaller backwaters like those
found in the Corn Lake are uncommon in this site (Figure AF8).

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The peak flow for the Palisade gage in 1999 was 12700 cfs on June 10. The peak
flow in 2000 was 13,500 cfs on May 31. In 200 I the peak flow was 8,410 cfs on May 21.
The median pcak flow for the II-year Palisade gage history is 13,500 cfs indicating that
peaks for 1999 and 2000 were near normal. Typically, flows in March are near 2000 cfs,
but in some years flows can drop after April I due to diversions into the Government
Highline and Grand Valley canals. In 1999, flows during the ascending limb (April and
May) of the hydro graph flow dropped to 435 cfs on April] 5, ] 999. That was the
minimum flow for the year. The minimum spring flow was] 110 cfs on April 5th, 2000
and 500 cfs on A pri I l7'h, 200 I.

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