An agricultural technique of supplying water to land to sustain the growth of crops. Developing irrigation system is an ancient practice being used as early as 500 BC along the banks of such regularly flooding rivers as the Nile, by digging channels to extend the area covered by the flood. Water distribution systems are of two broad types: surface and closed-conduit distribution system. In surface irrigation system, the entire land surface may be covered with water, or the water may be restricted to small ditches called furrows or rills. Closed-conduit irrigation systems use pipes to distribute water over wide areas or to the ground area around each plant. The major problems of irrigation system are increases in salinity as the water table begins to rise in areas not having good drainage. Naturally occurring salt can concentrate in irrigated fields eventually presenting a threat to the plants being cultivated.