Three major water sources in Pakistan are rain water, ground water and rivers. Irrigation system is not something new. Since olden days, people had devised various methods to water their fields. Some traditional methods of irrigation are Persian Wheel, Charsa and Shaduf.
Karez is another traditional irrigation system practiced in Baluchistan only. Karez is a horizontal canal located mainly on the foot hills and it brings the underground water to the surface. Modern advancements in the irrigation system are the perennial canals and tube wells.
Pakistan is basically a dry country with the River Indus and its tributaries being the main source of water supply. Dams both large and small and barrages have been built on the Indus and its tributaries. Large dams such as Tarbela Dam and Mangla Dam are multipurpose plans which not only store water, irrigate lands but also generate hydroelectricity.
Small dams like Khanpur Dam, Rawal Dam and Hub Dam supply water for agriculture, industrial and domestic purpose and act as a reservoir as well. A hilly terrain is required to build a dam.
Barrages on the other hand are built on flat places they also supply water for irrigation purpose and industrial and domestic use. Some barrages are Sukkur Barrage, Guddu Barrage, Kotri Barrage, and Chashma Barrage.
Canals are taken out from rivers, dams and barrages. Pakistan has one of the largest canal irrigation systems in the world. The Inundation canals are taken from rivers and they receive water only when the water level in the rivers is high such as during floods.
The perennial canals are taken from dams and barrages and supply water to the fields throughout the year. In Pakistan, there are a total of 150 dams; 3 large dams, 85 small dams, 19 barrages, 12 inter link canals, 45 canals and 0.7 million tube wells to meet the commercial, domestic and irrigational needs of the country.