7850

• UCREFRP Catalog Number: 7850
• Author: Hydrosphere Resource Consultants.
• Title: Yampa River Basin Recommended Alternatives, Detailed Feasibility Study
• USFW Year: 1994.
• USFW - Doc Type: Draft.
• Copyright Material: NO

Reservoir Operating Studies
'
Table 2-4
Preliminary* Flow Recommendations at Maybell
' Month Recommended Flow (cfs)
October 204 (50% exc.)
' November 255 (50% exc.)
December 228 (50% exc.)
January 217 (50% exc.)
February 256 (50% exc.)
March 498 (50% exc.)
April
May
June **
July 999 (50% exc.)
August 220 (50% exc.)
' September 91 * * * (50% exc.)
* Still under review by U. S. Fish and Wildlife Service
* * Percentile which occurs naturally in any given year.
* * * The 50% exceedance flow for September is 91 cfs based on water availability
considerations associated with the assumptions in the Yampa River Basin Model. The
Service recognizes that the conditions modeled are based on worst case assumptions
and that flows are not likely to drop to this level in the near future. If this flow level
were to regularly occur there may be a need to secure augmentation sources to
' maintain or enhance late summer flows.
' FINAL OPERATIONS STUDIES FOR THE ENLARGED ELKHEAD RESERVOIR
The final reservoir operations studies made using the Yampa River basin model
considered three basic scenarios: 1) current potential conditions, 2) year 2040 conditions
without the reservoir enlargement, and 3) year 2040 conditions WitJ1 the reservoir enlargement.
Several mainstem flow enhancement options were also examined under the latter scenario.
'
These various scenarios were defined so as to characterize the full range of likely water
management futures in the basin and to permit the with/without comparisons necessary for
environmental and biological assessments of the enlargement project. The key assumptions and
' results of these groups of model scenarios are presented below. Detailed tables of scenario
results can be found in Appendices E, F, and G.
'
Current Potential Conditions Scenario
Assumptions
This scenario represents the hydrologic conditions that would ensue if current potential
demands were active over the entire 53-year study period and if existing reservoirs were
operated according to contracts and agreements presently in place. It is = a "no action"
scenario since water demands will change in the future even without development of additional
' water storage or other changes in basin water management. Rather, it represents a "baseline"
that facilitates the characterization of future hydrologic conditions as differences from actual
present conditions. In terms of water demands it reflects a smaller amount of depletion than
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