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<br /> <br />05^OP/2003 16:10 FAX 2022084684 <br /> <br />A/S FISH/WILDLIFE/PARK <br /> <br />'4 ~ ~ <br /> <br />proportion of the canyon bottom annually cleared by high flows, thus decreasing the relative <br />importance of sediment mobilization relative to extended inundation. <br /> <br />To prlNent the permanent establishment of woody, riparian vegetation and to limit the <br />encroachment of herbaceous vegetation on depositional fecitures located between the current <br />active channel and the canyon walls requires peakflows of sufficient magnitude to mobilize <br />rooted substrates, prolonged inundation' of at least 85 days within the May 1 - October 1 <br />growing season, and a variable low flow throughout the remainder of the year to prevent <br />vegetation establishment along a fIXed low water line. Rare, large peaks (greater than J O. 000 <br />eft) preclude permanent encroachment of large woody veg~tation on dominant lateral gravel <br />bars, while smaller annual peaks (2,500 - 10,000 cft) maximize the extent of the dynamic <br />vegetation-free zone within the narrow active channel. <br /> <br />Based on the afore-mentioned studies, it is the position of the Department of the Tnterior that the <br />distinctive geologic, hydrologic, biotic, and aesthetic qualities of the Black Canyon of the <br />Gunnison National Park justify protection ofthe full rang~ of flows that are depicted in the <br />following table. These flows represent the minimum amo,unt necessary to protect the <br />environment of Black Canyon of the Gunnison National Park to ,a reasonable degree. <br /> <br />@009 <br /> <br />. <br /> <br />Base Flow 300 cfs 26 out of 26 years <br />Shoulder Flow 300.1000 cfs 22 out of 26 years . <br />Low Peak Flow 2000 - 5000 cfs 8 out of 26 years <br />, Medium Peak Flow 5000 - 10000 cfs 6 out of26 years <br />High Peak Flow 10,000 + cfs 3 out of 26 years <br /> <br />5 <br /> <br />- <br /> <br />. <br /> <br />