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Colorado River Water Quality lmprove~ent Program Final Environmental Impact Statement for the Lo~er Gunnison and Uintah Basin Units w ..... o f',;) Lead Agency U.S. Department of Agricultur~, Soil COnStrV3Lion Service Cooperating Agencies Agricultural Stabilization and Conservation Service, USDA Bureau of Reclamation Service, USDI Environmental Protection Agency States and Counties Directly Affected Colorado Delta County Montrose County Utah Duchesne County Uintah County \o-Tasatch County Abstract _ Lower Gunnison Basin Unit. The discussion of the Lover Gunnison unit shows that irrigated agriculture on 171,000 acres, contributes about 840,000 tons of salt to the Colorado River annuillly. Improved management of irrigation water including land leveling, measuring water onlo the field and lining onfarm earthen ditches and off-farm laterals can reduce the river's salt load by as much as 500,000 lons. reducing salinity concentrations at Imperial Dam by 52 milligrams per liter. Local benefits resulting from these improvements would be reflected in reduced costs of production. improved irrigation systems and increased crop yields. A worst-case analysis sho",s improvements to this level could impact up to 13,200 acres of ...etland (in one alternative). that have princi- pally developed as a result of irrigation in the valley for about 100 years. These wetlands have a habitat value of 461.200 units. The recommended plan, if implemented, would reduce salt loading by 335,000 tons per year, which could impact 3,800 acres of wetlands (10 percent of the ...etlands in the Lo...er Gunnison Basin Unit). I Abstract _ Uintah Basin Unit. Onfarm return flow from 205,000 acres of irrigated land in the Uintah Basin Unit presently contributes 177,200 tons of salt to the Colorado River annually. Onfarm irrigation efficiency improvements through better control and management of irrigation ~ater ~ill reduce the annual salt contribul1on by 76,600 tons and increase average annual streamflo"" by 20,200 acre-feel. This reduces the salt concentration by 10.3 milligrams per liter at Imperial Dam or allows the water quality at Imperial Dam to be maintained at the present level ~hlle developing an additional 86,000 acre-feet of water. Improvement in average onfarm irrigation efficiency from 34 to 51 percent will be accomplished by 1) installing and using ...'ater conveyance and control structures and measuring devices, 2) using the irrigation system best adapted to the soil, crops and level of managemenl desired, 3) utilizin6 soils information to properly design and layout irrigation systems, and 4) appl)lng the proper amount of ....ater at the proper time to meet crop consumptive use. There are about 49,000 acres of ~etland I..ildlife habitat in the basin. In the recommended plan, about 20,000 acres having an acre value of about 7.600 acres will be converted to upland habitat and about 1.900 acres of upland ...ildllle habitat having an acre value of 630 acres ",'ill be disturbed during construction. wildlife habitat mainte- nance and improvement and better farm crops with grain and corn added to the rotation will be implemented through long term agreements ~ith individual farmers to help offset losses. In addition loss of irrigation induced ~etland is minimized by th~ fact that conservation measures for salinity control are limited to those acres which have been irrigated for four of the last five years. I I I I Questions on this Supplement should he directed to: Frank Reckendorf. Environmental Resource Specialist ~est Technical SerVlce Center, Soil Consprvation Service 511 s. ~. Broad...ay, Portland, Oregon 97209 Phone _ Commercial: (503) 221-2841 FTS: 423-2841 I