WSP02017

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/1/1994
• Title: Lower Gunnison Basin Unit East Side Laterals - Colorado River Water Quality Improvement Program - SUPPLEMENT TO FEASIBILITY REPORT
• Water Supply Pro - Doc Type: Report/Study

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SUMMARY

Authority and Purpose

The Lower Gunnison Basin Unit (LGBU) was authorized for construction by
Public Law 98-569, enacted on October 30, 1984. The purpose of the unit is
to reduce salt loading to the Colorado River system, which receives an
estimated 360,000 tons of salt each year from the unit area. This salt
contribution is attributed to seepage losses from unlined canals and laterals
as well as deep percolation from irrigation water. Water dissolves the salts
as it passes through the underlying saline soils and carries them to the
Uncompahgre River and eventually to the Colorado River.

The plan of development for the entire unit, as presented in the Feasibility
ReporUFinal Environmental Statement, consisted of six components. One of
these components would eliminate winter flows throughout the
Uncompahgre Project delivery system, while the remaining five would
improve the five separate canal and lateral systems which traverse the area
east of the Uncompahgre River. Construction of the Winter Water
Replacement Program began in fiscal year (IT) 1990 and is scheduled to be
completed in 1996. However, construction of the last five components was
deferred because of the marginal cost effectiveness associated with canal
and lateral lining.

This Supplement to the Feasibility Report recommends piping only the
laterals and some small canal segments from the five deferred components.
This report provides a complete description of the proposed plan of
development and provides a basis for budget justifications in support of
appropriating construction funding.

Setting

The LGBU is located in west-central Colorado in the upper Colorado River
Basin. The unit area encompasses the Gunnison River drainage area
downstream from the Black Canyon of the Gunnison National Monument
and upstream from the confluence of the Gunnison and Uncompahgre
Rivers near the city of Delta. The unit includes portions of Delta,
Gunnison, Montrose, and Ouray Counties (see general map).

The unit area referred to in this report is within the Uncompahgre River
Valley and, specifically, the area served by the Uncompahgre Project, a
Federal development constructed in the early 1900's. The project provides
irrigation water for approximately 86,000 acres by diverting water from the
Gunnison and Uncompahgre Rivers.