7750

• UCREFRP Catalog Number: 7750
• Author: U.S. Bureau of Reclamation.
• Title: Study of Alternative Water Supplies for Endangered Fishes in the "15-Mile Reach" of the Colorado River.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

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CHAPTER II BACKGROUND

The Orchard Mesa Check
Historic Need for the "Check"
' In 1907-08, the OMID began supplying irrigation water to its service area on the bluffs south
of the Colorado River near Palisade, but needed a right-of-way from the United States to
' complete the project. At the same time, the Reclamation Service was planning a major
irrigation project north of the river that would be seriously affected by OMID's senior
irrigation rights. As a condition for granting the right-of-way across Federal land, the OMID
to agreed to share shortages. To further mitigate supply shortages the bypass channel was
constructed and placed in service in 1926. The bypass channel provided a means of
returning the pumping plant tailrace water to the Colorado River above the senior GVIC
diversion. Before the Grand Valley Project was completed, the OMID system had been
absorbed and was functioning as part of the larger project.
' Because there was no stored water to augment late-season flows at Cameo before Green
Mountain Reservoir was built in 1943, operators of the Grand Valley Project needed to
protect themselves against calls by the senior GVIC right of 520 cfs or risk water shortages
' in most years. When the natural flow of water in the Colorado River was insufficient to
satisfy the water rights at the Cameo diversion dam, some or all of the GVIC senior water
right was diverted at the Cameo Diversion dam. The portion of the GVIC senior right which
' was diverted was used for pumping purposes of the Orchard Mesa Pumping Plant and, after
1933, to generate electricity in the Orchard Mesa Powerplant. After the portion of GVIC
senior right was used for power generation and pumping purposes, that portion was diverted
(checked) in the Orchard Mesa bypass channel to a point upstream of the GVIC diversion
dam and then into the Colorado River for use by GVIC. This operation allowed continued
service to the Highline Canal and Orchard Mesa Canals until river flows were insufficient to
' satisfy all the irrigation demands. The OMID powerplant and pumping plant could continue
to operate under shortage conditions by diverting up to the full GVIC share at the Grand
Valley Project Dam and returning it to the river just upstream from the demand point. The
' United States, GVWUA, and OMID agreed to this method of operating for their mutual
benefit, but did not address any need to use the "check" for other purposes.
' After construction of Green Mountain Reservoir, additional water was available for irrigation
use on the West Slope. Water from Green Mountain was released whenever natural West
' Slope water supplies were insufficient to cover the major demands at Dotsero and Cameo.
Transmountain diversions were forced to use replacement sources if they continued to divert,
and the Division Engineer would make sure the "check" was installed before releasing water
' from Green Mountain Reservoir. By using the "check" to take care of a shortage to the
120-cfs junior right of GVIC (the most junior part of the Cameo call), less water was needed
(Revised 3/92) 11