WSP10375

• File Number: 8240.200.46.J
• Description: Ruedi Reservoir
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/28/1992
• Title: Effect of 1991 Flow Releases from Ruedi Reservoir on Endangered Fish Habitat in the 15-Mile Reach
• Water Supply Pro - Doc Type: Publication

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1991 Ruedi Releases

Releases of the first 10,000 ac ft began on August 13, and continued through
September 30, 1991. The release of the second 10,000 ac ft began on October 1
and continued through November 2, 1991. The releases made for endangered fish
in 1991 are summarized in Table 1 below and the complete data sets are enclosed.

Table 1.

Units CFS

Month Fryingpan Ruedi Head of End of Reach
River Flow Endangered IS-Mil e IS-Mil e Gains
Fish Release Reach Reach 1
Auaust' 209 82 783 1091 308
Sentember 167 91 9S0 1204 2S4
October 19S IS8 782 1043 261
November' 120 34 181S 2003 188

Prior to August 13, 1991, flows in the IS-Mile Reach either fell within or were
in excess of the recommended 700-1200 cfs range. From August 13 - October 31,
1991, there were 80 days from when Ruedi provided supplemental flows for the
IS-Mile Reach. This included an 8-day period when the extra releases were
temporarily suspended in response to excess water in the reach as a result of
heavy rainstorms.

Ouring the 80-day period, Service hydrologists determined the amount needed for
release on a daily basis (Monday through Friday) by monitoring flows at the
Pal isade gage and calculating how much was required to bring the total to
900 cfs. A temporary gage was operated by Richard D. Piland and Associates at
the lower end of the reach during August to December of 1991. Preliminary data
from this gage indicates that cumulative return flows amounted to an average of
223 cfs in August, 2S4 cfs in September, and 260 cfs in October. Considerable
rain during 1991 inflated these returns above what would normally be attributed
to irrigation return only.

Estimates of the effect the additional releases from Ruedi had on meeting the
IS-Mile Reach flow recommendation can be made by comparing the actual discharge
(gage readings) during the 80-day period with what the discharge would have been
if the releases had not been made. A comparison of the 'with' and 'without'
flows at the top and the bottom of the IS-Mile Reach is illustrated in Figure 1.

1 Based upon preliminary data provided by Richard Piland and Associates

Z Based upon flows from August 13-31

'Based upon flows for November 1-2

2