WSP02737

• File Number: 8276.120
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1981
• Title: Plan of Study: Grand Valley Unit Stage Two
• Water Supply Pro - Doc Type: Report/Study

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,..::, CHAPTER I

INTRODUCTION

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private water user organizations. Most of the laterals arE' owned and operated
independently of the canals, and many of the owners have incorporated for oper-
ation and maintenance purposes. The Grand Valley Unit was authorized to up-
grade these existing irrigation systems, and the lands associated with them, to
decrease salt loading to the Colorado River.

The plan for the overall Grand Valley Unit is to decrease the amount of
ground-water resulting from irrigation return flows and conveyance system seep-
age by lining canals and laterals and implementing on-farm irrigation improve-
ments. This reduction is expected to result in a decrease in salt loading to
the Colorado River of about 410,000 tons and a decrease in salinity at Imperial
Dam of approximately 43 mg/L. The plan would be accomplished by a two-segmen~
program conducted by the Bureau and the Soil Conservation Service (SCS). The
Bureau is conducting a water systems improvement program in which canals and
laterals are being lined or placed in pipe to reduce seepage. On-farm im-
provements which include upgrading irrigation systems by cost assistance, im-
proving irrigation management, improving grazing lands and grazing practices
on private rangeland, and directing voluntary wildlife improvement measures,
are being conducted by the Soil Conservation Service to reduce deep percola-
tion from farm operations.

At present the Grand Valley Unit is divided into two stages. Stage One,
which is under construction, involves the western end of th.. Grand Valley be-
tween Big Salt Wash and Mack Wash and between the Government Highline Canal
and the private distribution system. Stage Two involves essentially the rest
of the valley. (See frontispiece map)

Stage One development involves the concrete lining and rehabilitation of
structures along a 6.8-mile section of the Government Highl:lne Canal between
Big Salt Wash and Mack Wash in the western end of the Grand Valley. About 6.5
miles of interceptor ditch and four small detention ponds WE,re constructed
above the canal section to prevent runoff from entering the canal and some
existing cross-drainage features will be enlarged. Thirteen laterals with a
combined length of 34.2 miles now serve the area and will be consolidated into
12 laterals which will be placed in pipe sections for a total length of about
29 miles. A field station has been constructed for use as a construction
headquarters for the overall unit and will be used for operation and main-
tenance or for other project uses. Wildlife measures consisting of watering
ponds and acquisition of land to compensate for wildlife habitat losses are
under consideration by Congress.

Although this study on Stage Two is in the advanced planning stage, it
differs from other advance planning investigations because lining of canals
and laterals and other construction activity, authorized by Congress in 1974,
is already underway and partially complete in the Stage One area. Stage Two
investigations will include a re-evaluation of various alternatives and,
because nonlining options were only marginally evaluated before authorization,
salinity control measures other than lining will be evaluated.

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