Primitive humans, observing that natural floods stimulated plant growth, learned to lead river water onto their fields. At an early date, Middle Eastern farmers invented labor-saving devices for lifting irrigation water from rivers. These devices still are used in many parts of the world. The oldest, invented before 2000 B.C., is the shaduf, a counterweighted pole that provides leverage for a filled bucket. Other water-lifting devices from Egypt are Archimedes' screw (invented in the third century B.C., or earlier) and the undershot water wheel (about 200 B.C.).

Along the Nile, irrigation was relatively simple. The river rose gently and predictably in spring and early summer, and the water was diverted by a simple system of dikes and canals to nearby fields. The soaked soil sustained the crops through the hot season. A more elaborate system was required in ancient Mesopotamia. There, floods of the Tigris and Euphrates rivers were violent and unpredictable. Mesopotamian farmers had to impound, store, and convey irrigation water—much as the irrigators of the western United States do today. Archeologists have found evidence of large irrigation structures in Mesopotamia.

Prehistoric Indian civilizations of Peru and Mexico depended on irrigation. In China the Tukiangyien system, constructed about 300 B.C., spreads the waters of the Min River over 500,000 acres (2,000 km2). The Romans built irrigation systems in Algeria and Spain. A notable project of medieval times was the Grand Canal, which irrigated 80,000 acres (300 km2) in Lombardy, northern Italy.

Water law was codified as early as 1750 B.C., when King Hammurabi of Babylon decreed punishments for those who neglected the upkeep of ditches or usurped the water rights of others. The Koran (seventh century A.D.), sacred book of the Muslims, considers observance of water rights a test of good neighborliness.

As early as 300 B.C., Hohokam Indians of the American Southwest irrigated patches of corn, squash, and beans. In the 16th century, Spanish missionaries and settlers in California irrigated gardens and vineyards. About 1685, the growing of lowland rice—an irrigated crop—was introduced in South Carolina.

The Mormon settlers of Utah were pioneers of irrigation in the West; they built an irrigation system near the present site of Salt Lake City soon after their arrival in 1847. Since the early 1900's, the federal government has been responsible for the development of a number of large-scale irrigation projects in the western states.

Since World War II many governments have undertaken irrigation projects. A notable example was the construction of the Aswan Dam on the Nile River in Egypt. The Food and Agriculture Organization of the United Nations has helped to teach improved irrigation methods to farmers in many parts of the world.