WSPP283

• File Number: 8240.200.39.C
• Description: Colorado River Threatened-Endangered - RIPRAP - CFOPS - Water Availability
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/1/2003
• Author: Brown and Caldwell
• Title: Phase 2 Coordinated Facilities Water Availability Study for the Endangered Fishes of the Upper Colorado River - Final Report - 09-01-03
• Water Supply Pro - Doc Type: Report/Study

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CHAPTER 2

GROUND RULES, ASSUMPTIONS AND ANALYSIS PROCEDURES

2.1 INTRODUCTION

The Executive Committee and the consultant team established ground rules in Phase 1 under which
the feasibility investigation of alternatives for supplying an average of 20,000 acre-feet of water in
those years when the forecast spring peak flows are between 12,900 cfs and 26,600 cfs would proceed.
The Executive Committee and the team also identified assumptions that are necessary to facilitate the
study. The purpose of this section is to detail the ground rules and assumptions that have been made
for this investigation and to provide explanation and justification for them. The frequency and
certainty with which the 20,000 acre-feet will be made available is detailed in the Flow Targets section
below.

2.2 GROUND RULES

2.2.1 Administration

Recommended alternatives from this investigation do not need to include recommendations for a
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spring peak to the head of the 15-Mile Reach. This is because there is unappropriated water available
during the spring peak in years when flows at the head of the 15- Mile Reach are in the range of
12,900 to 26,600 cfs. From an administrative standpoint, the river is under "free river" conditions, and
therefore administration of flows past intervening water rights is currendy unnecessary. As specified in
the PBO, any new depletion during this period of the year may be covered under the PBO. For the
same reason, the conversion of water rights to instream flows in order to protect and convey flows to
the head of the 15-Mile Reach during the spring peak will not be considered further.

With regard to the secondary study purpose of providing flows in the late irrigation season, potential
administrative mechanisms will need to be identified to protect the water to and through the 15-Mile
Reach because the river is generally on call during that time of the year.

During Phase 1, the issue of how bypassed diversions to storage would be administered has been
discussed. Several alternatives for administration exist:

.

Bypassed diversions to storage would be credited toward a "paper filf' of the reservoir
and the reservoir would attempt to achieve a subsequent physical fill using a junior
refill right. This is essentially the administration agreed to by the SWAT team and used
to decree the Clinton Gulch, Green Mountain and Dillon refills.

Bypassed diversions to storage would not be credited toward a paper fill under an
administrative policy such that bypasses are regulatory in nature and the reservoir
would attempt to fill later under its own priority.

.

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