Pakistan is largely an arid to semiarid country with an average annual rainfall of about less than 100 mm in parts of lower Indus plains to more than 750 mm in the northern foothills, against crop water requirements ranging from 1487 mm in Jacobabad, Sindh, to 900 mm in Paraehinar, NWFP, 1280 mm in Faisalabad, Punjab, and 1400 mm, Turbat, Balochistan. Therefore, agriculture in the country heavily depends on the irrigation supplies delivered by the Indus Basin Irrigation network. This Indus Basin Irrigation System comprises three storage reservoirs. 19 diversion barrages, 12 link canals, 43 canal commands, and over 100,000 community watercourses irrigating an area of about 16 million hectares (Mha) out of about 31 Mha of cultivable land available. Most of the development of this irrigation system took place because of the Indus Water Treaty signed in September 1960 between India and Pakistan over water conflict.
Soon after independence on April 1, 1948, India unilaterally stopped the water supplies to Central Ban Doab Canal (CBDC) and Dipalpur Canal, claiming her sovereign right over the water passing through its territory. The control of the headworks regulating flows to these canals was with India. The border line between the two countries was drawn in disregard to the irrigation supplies. This water conflict, however, was settled through good offices of the World Bank in the form of Indus Water Treaty. As a result of this treaty, India was given the right to make exclusive use of the three eastern rivers (Ravi, Sutlej and Beas) with an average annual flow of about 43 million acre-feet (MAF. Under this treaty, Pakistan got the right to make full use of the three western rivers (Indus, Jhelum and Chenab) with an average annual flow of about 140 MAF. Also, the World Bank provided assistance to Pakistan to augment its irrigation supplies by diverting water from the western rivers to the eastern rivers so that areas af fected by this treaty can be irrigated. Under this agreement, two reservoirs (Mangla and Tarbela), eight link canals (Trimmu-Sidhnai, Sidhnai-Mailsi, Mailsi-Bahawal, Rasul-Qadarabad, Qadarabad-Balloki, Ballok-Suleimanki, Balloki, Balloki-Suleimanki, Taunsa-Panjna, Chashma-Jhelum), and six diversion barrages (Chasma, Rasul. Qadirabad, Marala, Sidhnai, Mailsi Syphon) were constructed to provide alternative sources of water to feed the eastern canals affected by this treaty.