Editing Irrigation (section)

===Surface irrigation===
{{Main|Surface irrigation}}

[[File:LevelBasinFloodIrrigation.JPG|thumb|Basin [[flood irrigation]] of [[wheat]]]]

Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In ''surface'' (''furrow,'' ''flood'', or ''level basin'') irrigation systems, water moves across the surface of agricultural lands, in order to wet it and infiltrate into the soil. Water moves by following gravity or the slope of the land. Surface irrigation can be subdivided into furrow,'' border strip or basin irrigation''. It is often called ''flood irrigation'' when the irrigation results in flooding or near flooding of the cultivated land. Historically, surface irrigation is the most common method of irrigating agricultural land across most parts of the world. The water application efficiency of surface irrigation is typically lower than other forms of irrigation, due in part to the lack of control of applied depths. Surface irrigation involves a significantly lower capital cost and energy requirement than pressurised irrigation systems. Hence it is often the irrigation choice for developing nations, for low value crops and for large fields. Where water levels from the irrigation source permit, the levels are controlled by dikes ([[levee]]s), usually plugged by soil. This is often seen in terraced rice fields (rice paddies), where the method is used to flood or control the level of water in each distinct field. In some cases, the water is pumped, or lifted by human or animal power to the level of the land.
[[File:Residential flood irrigation in Phoenix, Arizona, in the United States of America.jpg|thumb|Residential flood irrigation in Phoenix, Arizona, US]]
Surface irrigation is even used to water urban gardens in certain areas, for example, in and around [[Phoenix, Arizona]]. The irrigated area is surrounded by a [[berm]] and the water is delivered according to a schedule set by a local [[irrigation district]].<ref>{{cite web|title=Flood Irrigation Service|url=http://www.tempe.gov/home/showdocument?id=3194|publisher=City of Tempe, Arizona|access-date=29 July 2017}}</ref>

A special form of irrigation using surface water is [[spate irrigation]], also called floodwater harvesting. In case of a flood (spate), water is diverted to normally dry river beds (wadis) using a network of dams, gates and channels and spread over large areas. The moisture stored in the soil will be used thereafter to grow crops. Spate irrigation areas are in particular located in semi-arid or arid, mountainous regions.