334 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



south end of this great valley is at the northern foot of the San Juan 

 Mountains. Thence it extends nearly northwest, embracing, with its 

 slopes, all the drainage of the Uncoinpahgre, a large branch of the Gun- 

 nison, which in turn is the largest branch of the Grand. Near the mouth 

 of the Uncompahgre the Gunnison turns from west to northwest, keep- 

 ing the course of the valley, and occupying a caiion on the west edge of 

 the middle of the valley. At the mouth of the Gunnison the Grand 

 takes its direction, following the northwestern course, and hugging the 

 cliffs on the southwest side of the valley. At the mouth of Salt Creek 

 the river turns sharply at right angles and flows off to the southwest. 

 The valley, also, bends around to the west, in deference to the course of 

 the Roan Cliff's, which here border it on the north. Altogether this val- 

 ley has in Colorado a length, northwest and southeast, of 114 miles. Its 

 width is variable. On the Uncompahgre it is widest, reaching 18 miles, 

 while farther down it is from to 12 miles in width. Its area is between 

 1,300 and 1,400 square miles. In the course of this valley wo find all 

 grades ot natural fertility or barrenness. At its head, in Uncompahgre 

 Park, the valley is filled with meadow grass, and, in season, Is carpeted 

 with flowers. The timber on the hill-sides is heavy spruce and pine. 

 Going down the valley, the abundant growth of grass disappears to make 

 way for sage ; then that becomes stunted and scant^^ and below the 

 mouth of tfje Gunnison the valley is nearly destitute of vegetation, and 

 presents a hard, smooth surface of white, sun-baked clay. Uf this val- 

 ley, the waters of the Grand River can reach only about 200 square 

 miles, all which is situated on the northeast side of the river. The south 

 bank is a vertical wall, of too great a height to surmount with the slight 

 fall of the river. The soil of this part of the valley is a stiff, adhesive, 

 bottomless clay, containing considerable alkali. Its elevation is about 

 4,500 feet above sea. This is the last arable area on the Grand in 

 Colorado. 



The Gunnison, from its mouth up to the mouth of Eoubideau's Creek, 

 i. e., nearly to the mouth of the Uncompahgre, is in a canon 600 to 1,000 

 feet deep., cut in the edge of the valley, with the exception of a mile or 

 two at the mouth of Whitewater Creek. At this point there is a small 

 area of meadow-land, easily irrigated. 



The surface of this part of the valley is quite uneven, being much cut 

 up by ridges running down from tiie Grand Mesa just east of it. This 

 portion of the valley between the Gunnison and Grand is almost utterly 

 worthless. The only iiart of that can be irrigated are the bottom-lands 

 above the mouth of Eoubideau's Creek. These average two miles in 

 width, and are just high enough to escape floods. 



In the upper portion, known as the Uncompahgre Yalley, a different 

 condition of things exists. The bottom-lands of the Uncompahgre aver- 

 age at least a mile in width. The bench is smooth, sloping with the 

 river-bed approximately, and but 50 to 100 feet above it, while the 

 fall of the river is quite rapid. The whole volume of the river can be 

 used to advantage, with ]5lenty of land remaining to aw^ait a change 

 of climate. 



In September the river was gauged at the agency, near the head of 

 the valley, and found to carry 356 cubic feet of water per second. This 

 implies about 600 cubic feet at the end of July; an amount sufficient to 

 irrigate about 200 square miles. The elevation of this valley is from 

 5,000 to 6,000 feet. 



The Gunnison River heads in the saddle connecting the Elk and Sa- 

 watch Ranges. Its drainage-basin, of 8,000 square miles, includes most 

 of the western slopes of the Sawatch Range, the southern slopes of the 



