The quality of water in the river decreases gradually towards the delta and the coastal plains. Also likely to aggravate pollution is the use of chemical fertilizers, which has increased fourfold in the last two decades, partly in response to the Aswan High Dam's reduction of the flow of silt downstream. Almost all agriculture in Egypt is irrigated. Even the small, more humid area along the Mediterranean coast requires supplementary irrigation to produce reasonable yields. However, all future possibilities for irrigation will depend on the sharing of the Nile waters among the Nile basin countries.
All irrigation is full or partial control irrigation.
The irrigation system in the old lands of the Nile Valley is a combined gravity and water lifting system. At the third level, distributaries receive water according to a rotation schedule. In the new reclaimed areas, farmers have to use sprinkler or drip irrigation. Surface irrigation techniques are banned by law. The main reason for this ban is that these areas, located at the end of the systems, are more subject to water shortages.