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<br />o <br />o <br />00 <br />I-'" <br /> <br />CHAPTER 3 - AFFECl'ED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES <br /> <br />Descriotion of Area <br /> <br />The Lower Gunnison Basin Unit includes lands irrigated by the Uncompahgre Project <br />between the Uncompahgre Plateau to the southwest and Black Canyon uplift on the northeast. <br />The Gunnison River, a major tributary of the Colorado River, is joined by the Uncompahgre <br />River at Delta, Colorado and forms the northern boundary of the project area. All irrigation <br />waterways proposed for improvement are east of the Uncompahgre River. <br /> <br />East of the Uncompahgre River, the valley is undulating to rolling. The landscape formed <br />by the irregular erosion and deposition of the underlying Mancos Formation. Barren hills in <br />the area are shallow over the shale bedrock. Climate is semi-arid, with precipitation ranging <br />from 8 to J3 inches. Irrigated croplands, often bordered by small areas of uncultivated <br />vegetation, dominate the area. Natural vegetation is well interspersed with few large areas <br />dominated by a single type. At lower elevations, greasewood occurs on moist sites, while <br />saltbush is common on dry sites. The riparian corridors of the Uncompahgre and Gunnison <br />Rivers form the border of the project area. Natural ponds, permanent streams, open marshes <br />are rare, and irrigation ditches are the area's major open water resource. <br /> <br />The Uncompahgre River is generally considered poor aquatic habitat from Montrose to Delta <br />due to siltation and periodic low flows. Upstream from Montrose, the habitat improves and <br />a trout fishery exists. The Gunnison River upstream of the mouth of the North Fork (above <br />the project area) supports a gold medal trout fishery. The reach between the North Fork and <br />Uncompahgre River confluence is transitional to habitat for warm water fish species below <br />the confluence. <br /> <br />General Impacts <br /> <br />Improving lateral systems according to the 1984 Plan or the East Side Laterals proposal <br />would reduce seepage and the resultant salt loading by about 63,880 tons per year. Minor <br />reductions would result from UVWUA activities if No Action is taken. More efficient water <br />management would be possible with the piped lateral system, and localized seepage problems <br />in agricultural fields and developed areas would be prevented. The most significant impact <br />of either the 1984 Plan or the current proposal would be the loss or reduction in quality of <br />wetlands and wildlife habitat. Additional "prism" habitat losses associated with open water <br />and vegetated portions of the banks of the laterals would occur. Water and air quality <br />degradation occurs with the use of heroicides and burning to operate and maintain the earthen <br />or concrete-lined ditches. This would not occur if the laterals are placed in pipe. The <br />FR/FES contains additional details. <br /> <br />15 <br />