Fig. 286. Pumping Water for Irrigation
The most common source of water for irrigating purposes is a river or a smaller stream. Artesian wells are used in some parts of the country. Windmills are sometimes used when only a small supply of water is needed. Engines, hydraulic rams, and water-wheels are also employed. The water-wheel is one of the oldest and one of the most useful methods of raising water from streams. There are thousands of these in use in the dry regions of the West. Small buckets are fastened to a large wheel, which is turned by the current of a stream. As the wheel turns, the buckets are filled, raised, and then emptied into a trough called a flume. The water flows through the flume into the irrigating ditches, which distribute it as it is needed in the fields. In some parts of California and other comparatively dry sections, wells are sunk in or near the beds of underground streams, and then the water is pumped into ditches which convey it to the fields to be irrigated.
Engines are often used for pumping water from streams and transferring it to ditches or canals. The canals distribute the water over the land or over the growing crops.
Fig. 287. The Main Ditch of an Irrigation Plant
None of these methods, however, can be used for watering very large areas of land. Hence, as the value of farm lands increased other methods were sought. Shrewd men began to turn longing eyes on the wide stretches of barren land in the West. They knew that these waste lands, seemingly so unfertile, would become most fruitful as soon as water was turned on them. Could water enough be found? New plans to pen up floods of water were prepared, and immense sums were spent in carrying out these plans. Enormous dams of cemented stone were thrown across the gorges in the foothills of the mountains. Behind these solid dams the water from the rains and the melting snow of the mountains was backed for miles, and was at once ready to change barrenness into fruitfulness. The stored water is led by means of main canals and cross ditches wherever it is needed, and countless acres have been brought under cultivation.
Water is generally applied either by making furrows for its passage through the fields or by flooding the land. The latter plan is the cheaper, but it can be used only on level lands. Where the land is somewhat irregular a checking system, as it is called, is used to distribute the water. It is taken from check to check until the entire field has been irrigated.
Fig. 288. The Process of Irrigating Corn