Background Operation of Grand Valley Diversions

• Description: Background Operation of Grand Valley Diversions
• State: CO
• Title: Background Operation of Grand Valley Diversions
• Water Supply Pro - Doc Type: Project Overview

1
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 one of the conditions for granting the right -of -way across Federal land,
the OMID to agreed to share water supply shortages. 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 also needed to protect themselves against calls by the
senior GVIC right of 520 cfs or risk water shortages in most years. Consequently, as
another condition and to further mitigate supply shortages, the OMID was required to return
all pumping power water to the Colorado River above the GVIC's point of diversion. The
bypass channel was constructed and placed in service in 1926. Before the Grand Valley
Project was completed, the OMID system had been absorbed and was functioning as part of
the Project.
The bypass channel provided a means of returning the pumping plant tailrace water to the
Colorado River above the senior GVIC diversion. 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
from Green Mountain, and full administration of the river could be avoided. This river