8089

• UCREFRP Catalog Number: 8089
• Author: U.S. Bureau of Reclamation.
• Title: Final Environmental Assessment Gunnison River Activities, Passageway Around the Redlands Diversion Dam and Interim Agreement to Provide Water for Endangered Fish.
• USFW Year: 1995.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: NO

acre feet as the amount of water available from Blue Mesa for the interim water agreement, it
was decided that a 300 cfs flow recommendation for July through October would represent up
to 73,190 acre feet, which would be well under the 148,000 acre foot number. Thus the 148, 000
figure does not play a significant pan in developing the interim water agreement.
As further background, the interim agreement does provide for the release of sufficient water to
maintain a nummum,flow of 300 cfs during July through October below the Redlands Diversion
Dam. Under worst case conditions, this would require an Aspinall release of 73,190 acre feet.
Additional releases would be required to meet operational commitments as outlined in the interim
agreement to satisfy downstream Gunnison River mainstem users senior in priority to the Aspinall
Unit decrees year-round as hydrologic conditions and available water supplies allow.
For purposes of studies associated with this report, such hydrologic conditions were assumed to
be met if the flow at the Gunnison River near Whitewater was kept at 1,095 cfs. Operation
studies covering the period November 1973 through September 1994 were prepared for
evaluation of No Action and Alternatives A and B. These show no net deference in total Aspinall
Unit releases. Operation studies showed that commitments in the interim agreement can be met
under all but very dry year conditions (such as occurred in 1977) by redistribution of historic
release patterns.
In the operation studies, Aspinall Unit releases were reduced below those required to meet
desired flow levels if hydrologic conditions indicated that the projected volume of Blue Mesa
Reservoir would drop below 400,000 acre feet by the end of the calendar year. Under such
conditions, operations were modified and shortages to senior water rights and fish ,flows were
shared.
The operation study completed for Alternatives A and B showed that water year 1977 was the
only year in which the end of the year content of Blue Mesa Reservoir was expected to drop
below the 400, 000 acre-foot target. For example purposes, the operation study shows a possible
shortage scenario for 1977 in which flows below the Redlands Diversion Dam were allowed to
go to zero in March through June and only 200 cfs was provided below Redlands during July
through October, This is an example of how, under certain dry year conditions, supplies to
water rights could be impacted. Aspinall releases are curtailed while a portion of flows
available to downstream senior users under No Action conditions are reallocated to fish flows
below Redlands Diversion Dam.
Summary statistics show an average annual increase inflows below Redlands of 1, 416 acre feet
offset by an average annual decrease in, flows available to water rights below Whetewater by an
equal amount. This represents a reallocation of available flows at the Whitewater gage between
water right users and fish f lows below Redlands.
Additional information has been added to the final EA on the effect of the proposals on Blue
Mesa Reservoir. In addition, tables have been added to Appendix E showing effects on reservoir
elevation.
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