Final Environmental Assesment and Finding of No Significant Impact Gunnision River Activities June 1995

• Description: Final Environmental Assesment and Finding of No Significant Impact Gunnision River Activities June 1995
• State: CO
• Basin: Gunnison
• Date: 6/1/1995
• Title: Final Environmental Assesment and Finding of No Significant Impact Gunnision River Activities June 1995
• Water Supply Pro - Doc Type: Report/Study

interim agreement alternatives would have no effect on reservoir levels when supplies of water
are adequate. In a dry year such as 1990, Alternatives A and B would reduce the reservoir
content compared to No Action and Alternative C, as illustrated by the bar graph in Figure 6.
The reduction in storage levels is caused by the provision of flows to water users and the fish
under Alternatives A and B. In very dry years such as 1977, large drawdowns occur under all
alternatives, including No Action.
Use of the 148,000 acre-feet of storage in Blue Mesa Reservoir reserved for endangered fish
would ensure that water released under the interim agreement for endangered fish would not be
removed from other possible uses.
River Administration -- Impacts of the agreement alternatives on water users are seen through
calls for river administration being placed by senior water rights, which result in curtailment of
use by upstream junior rights. Table 5 summarizes the number of months shortages or river
administration (calls) would occur under the alternatives. It predicts that implementation of
Alternatives A or B would succeed in protecting water users in the basin from calls to levels
similar to those of No Action conditions.
Table 5
Comparison of River Administration Occurrences
1 Based on the 22- year.period of study as shown in Appendix E.
In summary, providing for passage and maintaining habitat for endangered fish would cause
changes in river flows, water use, storage, and river administration when water shortages occur.
The impacts do not differ between Alternatives A and B. Releasing water stored in Blue Mesa
Reservoir would cause storage levels to decrease under dry year conditions such as occurred in
25
Number of Months River
Percentage of Months River
Alternative
Administration Occurs in a
Administration Occurs '
22 -year Period 1
No Action
January - December
13
5%
July - October
3
3%
A and B
January - December
12
5%
July - October
4
5%
C
January - December
23
9%
July - October
13
15%
1 Based on the 22- year.period of study as shown in Appendix E.
In summary, providing for passage and maintaining habitat for endangered fish would cause
changes in river flows, water use, storage, and river administration when water shortages occur.
The impacts do not differ between Alternatives A and B. Releasing water stored in Blue Mesa
Reservoir would cause storage levels to decrease under dry year conditions such as occurred in
25