Irrigation is the watering of land by some means other than rain-fall. There are many parts of the world that do not receive very much rainfall. Farmers in these areas cannot grow the crops that are needed to feed people who live there. In these places, irrigation is used. This is only possible if there is water available nearby in the form of well, rivers, lakes, or manmade reservoirs. There are many different ways in which the irrigation water may be brought up to the field and crops. If the slope of the land is right, small irrigation ditches may be dug from a main reservoir leading to the fields where they branch out. At other times, pumps must be used. Often a combination of pumps and sprinklers is used.
About 500,000 acres of land in the Imperial Valley of California as well as large parts of Utah, Arizona, New Mexico and Texas, have been irrigated for years by brining water from reservoir, lakes and streams many miles away. In the state of Washington, Grand Coulee Dam on the Columbia River has brought water to more than a million acres of otherwise arid land. Each year more arid land in the western United States is made into good farmland by irrigation. When the water is brought to the soil, minerals and nutrients become available to the plants.
Fields of sugar beets, wheat, alfalfa and other crops are grown in what were at one time desert regions of the West. Orange groves throve where once only cacti could survive. Some farms branch out water from their deep wells of irrigation. Irrigation is one way to supply water to plants that otherwise could not grow.