Surface irrigation is the oldest and most widely used method of irrigation. Also called gravity irrigation or field flooding, surface irrigation relies on the natural slope of a field to distribute water. Water is released at the head of a sloping field and is allowed to flow to the other end.
The efficiency of a surface irrigation system is dependent on the type of soil and the slope of the field. The soil serves two roles: the first is distribution, to convey the water to other parts of the field, and the second is infiltration, the delivery of the water to the plant roots. Variations in the soil's infiltration capacity lead to non-uniform water distribution, making it necessary to over-irrigate some parts of a field in order to give adequate coverage to the whole field (Crow, 2000).
Surface irrigation systems have low energy requirements, since most of the work is done by gravity. The energy required for surface irrigation is the energy needed to pump the water to the distribution unit. Initial setup costs for surface irrigation are generally low. Through terracing, surface irrigation can be applied to sloping land as well, though the construction and maintenance of terraces requires added labor expense (Hillel, 1987).