WSP11736

• File Number: 8240.200.44.A.1
• Description: Green Mountain Reservoir
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1999
• Author: USDOI/BOR
• Title: 1999 Late Summer and Fall Operations Report of the HUP Managing Entities and Water Managers
• Water Supply Pro - Doc Type: Publication

that point, it was uncertain whether any of the 66,000 acre-feet would be surplus and available
for release to the Grand Valley Power Plant and the 15 Mile Reach.

A total of 9 meetings and/or conference calls were held from July 14 to November 3 to manage
reservoir releases, coordinate irrigation diversions in the Grand Valley, and attempt to maintain
the mean monthly target flows in the 15 Mile Reach.

During the 1999 irrigation season, releases that directly or indirectly benefitted flows in the
15 Mile Reach were made from the following reservoirs:

1) Ruedi Reservoir
2) Wolford Mountain Reservoir
3) Green Mountain Reservoir Historic User's Pool
4) Dillon Reservoir
5) Williams Fork Reservoir
6) Granby Reservoir
7) Willow Creek Reservoir

Beginning in September, representatives from Denver Water (managers of Dillon and Williams
Fork Reservoirs) and the Northern Colorado Water Conservancy District (managers of Gran by
and Willow Creek Reservoirs) participated in conference calls to coordinate planned releases
from their reservoirs.

In October, the Public Service Company of Colorado's Shoshone Power Plant staff participated
in conference calls to request lowered Colorado River flows during their maintenance scheduled
to begin in November.

Flow Recommendations

At the July 14 meeting, the Service set the mean monthly target flow for the IS-Mile Reach at
1,240 cfs, based on an 80% exceedance, or drier than average, year. By the second week of
August, hydrologic conditions in the basin had improved, and the Service revised the target to
1,630 cfs, the flow recommended for an above average water year.

The Service has calculated recommendations for mean minimum flows and the percent of years
(the rate) the flows should be provided. The rate was determined using historical variations in
winter snowpack levels (high, above-average, below-average and low). The Service's mean
monthly flow recommendations for the 15 Mile Reach during the late summer months (from
page 65 of their 1995 report) are:

Snowoack Level
High
Above Average
Below Average
Low

Rate
25%
25%
30%
20%

Aug/Seo/Oct Mean Monthlv Flow
1,630 cfs
1,630 cfs
1,240 cfs
810 cfs

1999 Late SummerlFall Operations

HUP Managing Entities & Water Managers

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