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<br />... <br /> <br />..' <br /> <br />. <br /> <br />.' <br /> <br />" <br /> <br />". <br /> <br />2204 <br /> <br />is considered one of the nation's finest examples of major gorge- <br /> <br /> <br />cutting and perhaps the most remarkable bit of scenery in the spec- <br /> <br /> <br />tacular ~an Juan Mountains of Colorado. Beloh the floor of a broader <br /> <br /> <br />outer valley of comparatively recent cretaceous sandstone and shale, <br /> <br /> <br />the Gunnison River has been furiously carving its channel deeper and <br /> <br /> <br />deeper, through several hundred million years, into the pre-Camb- <br /> <br /> <br />rian complex or basic"earth-stuff", which 1mnediately underlies it, <br /> <br /> <br />and at a greater speed than all combined forces can widen it. <br /> <br /> <br />Varying from 1,730 feet to 2,425 feet in depth, the gorge at some <br /> <br /> <br />locations is far deeper than its width between rims. <br /> <br /> <br />The river falls 263 feet per mile through the IlIonu- <br /> <br /> <br />ment and regulation or diversion of the river flow above the gorge <br /> <br /> <br />will have a decided physical effect over a period of years, upon the <br /> <br /> <br />powers of the river to continue cutting the canyon deeper and carry- <br /> <br /> <br />ing away the ~ck debris which falls into the gorge as it has done <br /> <br /> <br />in the past. <br /> <br />From the average river gradient of 263 feet per mile <br />it is possible to picture 50 second feet of water flowing through <br />reaches of the river with a cD-efficient n= 0.030, at 10 feet per <br />second in a channel 2 feet deep and 5 feet .dde. ilhen the coef- <br />ficient is n= 0.050 the water will flow at 5 feet per second in a <br />channell foot deep and 10 feet >iide. The proposal of the Bureau of <br />Reclamation, therefore, is to change the Gunnison iUver to a rapid <br />but small broDk. <br /> <br />20 <br />