IN A WORD: “BADLY.” How India’s Threat to Block Rivers Could Devastate Pakistan.

The agreement became necessary after 1947, when India and Pakistan became independent countries, although the treaty took a decade to negotiate and was signed in 1960, with the World Bank as a mediator. The treaty outlined the rights and obligations of both countries for “equitable use” of water flowing in the Indus river system.

India has unrestricted use of the waters of the three eastern rivers: the Ravi, the Sutlej and the Beas, two of which then flow into Pakistan. Pakistan has control of the Indus, the Chenab and the Jhelum, known as the western rivers, which pass through Indian-controlled territory but primarily reside in Pakistan. The treaty obligates India to let the waters of those rivers flow freely to Pakistan for its “unrestricted use.”

For decades, the treaty has been hailed as a landmark that could serve as a template for solving international water disputes. But in the past decade, India has threatened to weaponize the treaty during conflicts with Pakistan.

After Pakistani terrorists attacked an Indian Army base in the Kashmiri town of Uri in 2016, Mr. Modi told Indus Waters Treaty officials that “blood and water cannot flow together.” And in 2019, Indian government officials threatened to divert the flow of the eastern rivers away from Pakistan after a suicide bombing that killed dozens of Indian security forces in Kashmir.

It would put Pakistan in a tough spot. The country is arid and has been battling acute water shortages, partly because of extreme weather events. Last month, Pakistan’s water regulator warned that Punjab and Sindh, the country’s key agricultural provinces, could already face water shortfalls of as much as 35 percent during the final phase of the current crop season.

Upcoming monsoon rains also hold risks for Pakistan because India could choose to release surplus water from the eastern rivers without prior notification, potentially triggering floods, said Naseer Memon, an Islamabad-based policy analyst focusing on water governance.

Pakistan is in a tough spot, but maybe that’s something Islamabad should consider when deciding to support terrorist groups.