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'. 0'1:').' f:.,'" , , ~:.. v :t I Affected Environment & Consequences 3-35 vegetation along the Uncompahgre River can be classified as wetland. Characteristics of these zones are discussed in detail in Section 3.10 below, and in Greystone (1994). 3.9.2 Impacts of Alternatives 3.9.2.1 No Action Changes in vegetation may occur under the No Action alternative along the Gunnison River as a more natural hydrograph is implemented on the river. This may result in more vegetation scouring in the canyon. No major changes are projected along the Uncompahgre River, although continued residential development may infringe on riparian areas. 3.9.2.2 Development Alternatives Under the development alternatives, vegetation disturbance would occur in construction areas. Disturbed areas would be restored and reseeded. The PElS concluded that lower flows in the Gunnison River would allow the establishment of additional riparian and wetland vegetation; however, scouring of the vegetation would occur during high flows as now occurs. As indicated previously, high spring flows are the primary factor in controlling vegetation in this area, and the magnitude and frequency of these high flows would not be significantly affected by the Project. In an independent study commissioned by the National Park Service, Auble et al (1993) found that riparian vegetation along the Gunnison River depends more upon the maximum and minimum flows than the mean flow. Peak flows come, and the channel is scoured of vegetation. During dry periods, vegetation encroaches into the channel. Because the proposed project would have little or no effect on the peak or minimum flows, the project is not expected to have significant impacts to the Gunnison's riparian vegetation, This conclusion tends to confirm the predictions made in the PElS. Between peaks, vegetation will likely encroach into the channel more so than in the past. However, the peak flows that occur during the spring would limit the encroachment. During scoping, a member of the public commented that the hydrologic changes to the Uncompahgre River resulting from the proposed Project would limit recruitment and growth of cottonwood and willow communities along the river. The proposed Project would reverse the natural hydrograph of the river. That is, winter flows would at times approach those normally seen only in the spring and early summer. During the summer and early fall, flows would diminish to slightly more than historical averages. However, high flows during the winter months are expected to be within the normal channel, since such flows are well below typical spring flood flows. The potential scouring effect on cottonwood seedlings is thus likely to be minimal. . AS Lateral Hydropower Project July 2000 .~"" . ' .' \ .'~' , , ...LP~ &,_ _____;.',,'~ ,!:i" ,.':k .....!