
5A 
North Platte in North Park, Colorado, the two rivers flowing eastward 
and uniting in Nebraska. 
At the northwest the Big Horn, Yellowstone, and Upper Missouri 
Rivers rise within or near the Yellowstone Park, and find outlet 
through the channel of the Missouri. Crossing the Continental Divide 
westward, it is found that Clark’s Fork of the Columbia, the Salmon 
river, and Lewis or Snake River, also rise in the same region, but, as 
tributaries of the Columbia, send their waters to the Pacific Ocean. 
In the southwest the principal streams flowing into the lakes of the 
Great Salt Lake Basin are the Bear, Weber, and Sevier. The Green 
River, which has its source in the Wind River Mountains, Wyoming; 
the Grand River, which drains Middle Park, Colorado, and the San 
Juan River, which rises in the southern part of the same State, unite 
in southern Utah and form the Colorado River of the West. 
The Rio Grande and Arkansas Rivers drain the southeastern portion 
of the Rocky Mountain region. They have a common origin in the 
mountains of Colorado, but the first seeks an outlet directly in the Gulf 
of Mexico, while the latter, at a point some 800 miles northeastward, 
unites with the Mississippi river. 
The Rio Grande, Arkansas, North and South Platte, and their main 
affluents, debouch upon high planes which slope rapidly to the south and 
east; and while the most of these streams pass through deep canyons 
in emerging from the mountains, they flow with a rapid current (de- 
scending from 5 to 8 feet to the mile) in shallow channels. ‘Therefore 
itis not difficult to utilize their waters for irrigation and other pur- 
poses. 
In Montana the plains have much less elevation than in the region 
southward, and the principal streams, the Upper Missouri and the Yel- 
lowstone, following a long and devious course to the junction of the 
two, have a gradual descent and sluggish flow ; hence it is not easy to 
bring their waters to the level of the adjacent country. What can be 
done there by a system of reservoirs which will save the flood waters of 
spring and early summer, is a question for the future. 
In Idaho, upon the western slope of the range, the principal streams 
flow rapidly, through arable valleys, and the waters can be easily util- 
ized. 
Southward, in western Colorado, the streams, in descending from the 
mountains, have a swift current and pass through valleys of much nat- 
ural fertility. As they approach the plateau region, farther south and 
west, some of them enter profound canyons, and thus are lost for irri- 
gating purposes. 
ALTITUDES. 
The altitudes of the Rocky Mountain region, inclusive of the valleys, 
plains, and plateaus, vary from 680 feet above sea-level at Lewiston, 
Idaho, to an extreme height of 14,460 feet in the mountains of Colorado. 

