Engineering Wonders of the World
Volume I

90 ENGINEERING WONDERS OF THE WORLD. The Arkansas River, like the Platte, is a typical river of the arid regions. It has its sources near those of the latter, in th© highest mountains of Central Colorado, The Arkansas. _ . and emerges upon tne plain from one of the most remarkable canyons in the world. Its valley comprises two low benches, the narrower being a present flood plain along part of it, owing to deficient rainfall, agricul- ture is wholly dependent upon irrigation. Owing to its vast extent, the economic import- ance of compensating for the absence of natural moisture in order to bring about its proper development cannot be estimated. In this region the lands are classified as follows— irrigable lands, pasturage lands, and timber SCENE IN THE GREAT PLAINS REGION. LAND WHICH WILL BE IRRIGATED; the banks of the stream. Irrigation is con- fined largely to this portion of the valley, and extends across the Colorado line into Kansas. The Arkansas River supplies water to approxi- mately 450,000 acres of land each year in Colorado and Kansas, the irrigation works representing an initial outlay of not less than $6,000,000. THE TRUE DESERT. West of the Rocky Mountains lies the true arid region of the United States, comprising an area equal to four-tenths of the whole country, exclusive of Alaska. Over the greater lands. Irrigable lands usually lie along the streams, and comprise only a small part of the total. Above the lowlands are valleys, hills, and mountain slopes, covered with grasses, and affording pasturage for cattle, horses, and sheep. On the mountain sides and high plateaus are vast areas, heavily forested, extending far above the elevation at which agriculture can be practised. Various estimates of the total irrigable area in the arid region have been made from time to time. Owing to the fact, however, that our know- ledge of the flow of streams and storage possi- bilities is yet incomplete, and that largo areas