WSP01636

• File Number: 8276.100
• Description: Grand Valley Unit - Colorado River Basin Salinity Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1986
• Title: Summary Sheet -- Grand Valley Unit - Colorado River Basin Salinity Control Project
• Water Supply Pro - Doc Type: Project Overview

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concrete-lined and cross-drainage facilities were
constructed. In addition, 13 open channel laterals
were consolidated into 12 pipe laterals and a moss
and debris removal structure was placed at the
beginning of the canal lining.

Construction of Stage One was essentially completed
in April 1983 at a construction cost of about $28
million; it resulted in a reduction in salt loading
to the Colorado River of about 21,900 tons annually
and a decrease in salinity at Imperial Dam of about
2.0 milligrams per liter (mg/L). at a cost
effectiveness of $86 per ton.

Hydrosalinity monitoring of Stage One improvements
began in 1981 and continued through 1984. Under
the 1976 through 1984 monitoring program, water
table measurements and water samples were taken
from observation wells in the study area, a
hydrologically isolated basin. Outflow and
electrical conductivity were continuously recorded.
Inflow and outflow data and electrical conductivity
in the canals in the study area were also recorded.
Data were used for evaluating the effects of all
Stage One improvements on ground- and surface-water
flows and quality.

Analysis of the monitoring data indicated that
canal and lateral seepage was decreased by
approximately 5,700 acre-feet and that salt loading
to the Colorado River decreased by approximately
21,900 tons, supporting recommendations for
initiating construction of Stage Two.

Wildlife was monitored to determine the effect of
Stage One on both wildlife habitat and populations
and recreation associated with wildlife.

Monitoring of wildlife habitat and populations was
conducted between 1981 and 1984 under a contract"
with the Colorado Division of Wildlife. Monitoring
results showed that replacing earth laterals with
pipe caused natural vegetation to be cleared on
approximately 200 acres. and more than one-half of
the cottonwood trees along the laterals were lost.
The acreage of marsh and shrub lands declined 6 to 8
percent in Stage One. Croplands actually
increased, but vegetation bordering croplands
declined by approximately 50 percent.

Wildlife use along the lined canal and laterals
also declined. Water available to some native
vegetation areas decreased dramatically following
lining the canal or placing the laterals in pipes.
Seepage areas below the canal and laterals have a
greatly diminished water supply. Washes have
either remained unchanged or have experienced
increased flows during the irrigation season from
spillage from canal wastewater and decreased flows
during the nonirrigation season from decreased
ground-water flows.

Grand Valley Unit
October 1986
Page 2 of 2

Monitoring results supported recommendations for
wildlife habitat compensation of Stage Two.

STAGE TWO

Beginning in
investigations
alternatives
measures other
were minimally

Novemher 1981, Stage Two
included reevaluating various
and analyzing salinity control
than lining. since nonlining options
studied b~fore authorization.

The Stage Two plan covers the remaining canal and
lateral systems in the valley exclusive of the
Stage One area (see map). In addition to Stage
One, areas excluded from Stage Two include the
Redlands and the Orchard Mesa Power Canal. The
plan provides for installing pipe laterals in the
private and Federal systems within the entire Stage
Two area and lining the west end, middle. and east
end portions of the Gove"rnment Highline Canal. The
west end portion of the canal and laterals will be
constructed first. Construction is planned
beginning the fall of 1986.

Construction costs for Btage Two are estimated at
approximately $200 mill "ion based on January 1985
appraisal-level prices. Implementing the plan
would result in a reduction in salt loading to the
Colorado River of about [39,500 tons per year and a
decrease in salinity at Imperial Dam of about 12.7
mg/L. at a cost effectiveness of $92 per ton.

Replacement measures for wildlife habitat were
authorized by Congress under Public Law 98-569.

STATISTICS FOR TOTAL GRM~D VALLEY UNIT

Construction costs for Stage One plus Stage Two are
estimated at about $230 million based on January
1985 appraisal-level prices. Implementing both
stages would resuLt in a reduction in salt loading
to the Colorado River of about 161,400 tons
annually and a decrease in salinity at Imperial Dam
of about 14.7 mg/L. at a cost effectiveness of $91
per ton.

FINAL EIS

The final environmental impact statement, which
describes alternatives for the construction and
operation of the Grand ValLey Unit, was filed with
the Environmental Protection Agency on May 23,
1986.

LOCAL INTEREST

The Grand Valley Salinity Coordinating Committee
meets three times a year at the Grand Junction
Projects Office and is open to all persons and
agencies interested in c:ttending. The purpose of
the committee is to coordinate salinity studies in
the Grand Valley and to disseminate information to
the public.

Bureau of Reclamation
P.O. Box 1889
Grand Junction, CO 81502

242-8621