WSP00353

• File Number: 8240.200.43.H.2
• Description: Grand Valley/Orchard Mesa -
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/11/1993
• Title: Analysis of the Orchard Mesa Check Operation Under Current and Historic Stream Administration Practices
• Water Supply Pro - Doc Type: Publication

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Presently, streamflows must average approximately 1,950 cfs to meet the same demand. The increased
demand of the Cameo call is graphically shown in Figure 4. The figure compares the actual recorded
streamflow at Cameo during dry years for both administrative periods. It is clear that under current
administration, late summer streamflows at Cameo are maintained at a greater volume than they were
historically. Most, if not all, of this increased water is made available to the Cameo call through release of
water from Green Mountain Reservoir. We believe that this represents a new demand on the river that was
not contemplated by the Bureau of Reclamation during development of the December 22, 1983 Green
Mountain Reservoir operating policy.

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POTENTIAL IMPACT - WEST SLOPE WATER USERS

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The 66,000 AF of Green Mountain Reservoir storage identified to meet the demands of west slope

beneficiaries was established by the Bureau based upon actual releases made in 1977. 1977 was

an extreme drought year in Colorado and severe shortages in the Colorado River placed high

demand on Green Mountain Reservoir. Hydrologic studies of various basins in western Colorado

indicate that a drought as severe as 1977 occurs on a frequency of only 1 year in 70. Due to the

severity of the drought, the Bureau, in developing it's operating policy, believed that the 66,000

AF represented the maximum amount of storage that would have to be set aside for west slope

beneficiaries. The remaining yield of the 100,000 AF power pool was made available for sale to

private and public entities under long-term contracts.

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The releases made from Green Mountain Reservoir in 1977 occurred during the period of historic
administration of the Check. During this year, the wrinen call and subsequent release of water
from Green Mountain were made only after the Check structure was fully implemented. This
condition was confirmed in a lener to the Bureau from then Division Eng'ineer Enewold (Anachment

2).

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The water demand analysis outlined in the previous chapter suggests that if the Check had been

administered as it is currently, substantially more water than 66,000 AF would have been released

from Green Mountain Reservoir to protect west slope beneficiaries, Because the Bureau's

operating policy limits releases to no more than 66,000 AF for this purpose, it is probable that the

reservoir pool would be exhausted at some point during the summer and west slope users would

be vulnerable to a call during the late irrigation season. This concern was substantiated in part

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