WSP06888

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/1/1982
• Author: USDA
• Title: Colorado River Water Quality Improvement Program - Final Environmental Impact Statement for Lower Gunnison Basin Unit - Montrose and Delta Counties CO and Uintah Basin Unit
• Water Supply Pro - Doc Type: EIS

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SUH.'1ARl' - LOwER GliSSISOS BASIN USlT

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This USDA salinIty control study of the Lo...er Gunnison Basin Unit of the Colorado
Rivpr water Quality Improvement Program \Oas carried out under Public La... 93-320,
the Colorado River Bdsin Salinity Control ACl. dated June 24, 1974, as a means
to Impl~ment the salInity control policy adopted for the Colorado River.
Irri~ated agriculture on 171,000 acres In the Lower Gunnison River Valley
contributes about 840,000 lons of sdlt to the Colorado River annually. ~easures
for improved management of Irrigation ...aler including land leveling, measuring
of ...ater onto the fields and lining onfarm and oft-farm earthern ditches and
laterals could rt'duct> the Colorado River's salt load by as much as 500,000
tons, reducing salinity concentratIons of the Colorado River at Imperial Dam
by S2 milligrams per litt,r. Ho....ever, the practical limit of reduction is
about 420,000 tons, or 44 milligrams per liter. Local benefits resulting from
these improvements ,.:ould be reflected in reduced costs of production, improved
irrigation systems and increased crop YIelds. Improvements at this level
could, based on a ~orst-case analysis, adversely impact up to 13,200 acres of
the 14.800 acres of irri~dtion influenced wetlands that have developed as a
result of introducing irrigation into the valley about 100 years ago. There
are an additional 24,800 acres of riparian ~etlands that would not be adversely
affected.

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Eight alternative plans address four It'vels of resource development for reducing
the river's salt load. Tbese levels are: a continuation of ongoing USDA pro-
grams (no accelerated action), onfarm irrigation ""ater manaJ::ement (nonstructural
alterndtive), ontarm ditch lining only, and combining improved ontarm irrigation
water management ...ith ditch lining at t~o options of onfarro improvement (manual
or automatic), linIng of at [-farm laterals is displayed as a supplemental
action to six of these alternatives.

Plan 7 is recommended for implementation and ~as selected after revie~ing the
eight candidate plans ~ith farmers and ranchers in the valley; ~ith officials
from local. state and federal agencies; with other interested groups; and
after considerin~ comments on th~ draft report received from public revie~.
!1aJor factors influenCing the selection include tht> 11esires of local lando...'ners
.lnd OPf'f,ltors, cost effective salinity reduction, overall lInplementation cost,
and program adminlstration.

Plan 7 tneludes improvt'ment of off-farm laterals in addition to those needed
fOf proper operation of the onfarm improvements. The implementation period
should be ten years and program effectiveness should he evaluated at three-year
intervals to dett'rmine if the program is achieving the expected degree of
salinity reduction,

The total Installation cost including mitigation of Plan 7 is estimated to be
$169,400,000. It is recommended that the federal government share the construc-
tion cost at a rate not gn'ater than 75 percent. At 75 percent cost-share the
cost to the federal government is 5137.885,000 over the 10-year implementation
period, consisting of $94.S4~,OOO tor construction. 525,740,000 for administrative
and technical assistance, and 517.600,000 to mitigate the loss of habitat
values. The total cost to the local people is estIm.:tted to be $31,515.000 for
construction and S800.000 per year for operation, maintenance and replacement
after the program is fully implemented.

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