The 1947 boundary cut the world's largest integrated irrigation system in half, leaving headworks in India and command areas in Pakistan. On 1 April 1948 India stopped water to canals feeding Pakistani Punjab. Supply was restored under an interim agreement in May.
Negotiations under World Bank auspices ran for nine years. The Indus Waters Treaty was signed at Karachi on 19 September 1960 by Jawaharlal Nehru and Ayub Khan.
It divided the rivers rather than sharing them. The three eastern rivers, Ravi, Beas and Sutlej, went to India. The three western rivers, Indus, Jhelum and Chenab, went to Pakistan, with limited Indian use upstream. Pakistan built replacement works, Mangla and Tarbela and the link canals, partly with international funding.
It has survived three wars. It is routinely described as the most successful water treaty in the world, which says as much about the others.
For Punjab on the Indian side it meant that the eastern rivers had to be fully used, which is the origin of the Bhakra and Pong projects, the Rajasthan canal and the entire subsequent quarrel between Punjab, Haryana and Rajasthan about who owns the water.
David Lilienthal, who had run the Tennessee Valley Authority, published an article in 1951 arguing that the Indus was an engineering problem rather than a political one. Eugene Black at the World Bank read it and offered to broker. A magazine piece started the nine years of negotiation that followed.
Pakistan was paid to rebuild. The Indus Basin Development Fund put money from Britain, the United States, Canada, Australia, West Germany, New Zealand and India itself into Mangla, Tarbela and the link canals, which is how an agreement that took three rivers away was made acceptable to the country losing them.
It has survived every war between the two countries. It is also the reason the Punjab plain on the Indian side is irrigated from three rivers rather than five.