A day ago, after the Pahalgam attack in which 26 were killed and several injured, India announced that it would keep the Indus Waters Treaty (IWT) of 1960 in abeyance with immediate effect.How will India enforce the suspension of IWT?India can do two things. The first is to halt regulated water flow in the western rivers (Indus, Jhelum and Chenab) – stop releasing water from dams and hydroelectric projects on these rivers. While natural flow through these rivers will continue, regulated releases, which is critical for Pakistan’s irrigation and drinking water, could stop. For example, the Baglihar Dam on the Chenab could retain water, reducing downstream flow to Pakistan.The second is that India could accelerate infrastructure development by fast-tracking storage projects on western rivers, such as the Pakal Dul (1,000 MW) and the Sawalkot (1,856 MW) dams on the Chenab. This would allow India to increase control over water flow in Chenab in the future.In addition, technical meetings, data sharing, and dispute-resolution mechanisms under the IWT can be frozen. India will have to no longer notify Pakistan about water flow changes or project designs.What is the difference between regulated and natural flow?The difference between natural flow and regulated flow in the context of the IWT lies in whether the water’s movement is shaped by human intervention or left to follow its course as determined by nature. The IWT is designed to ensure that India’s regulation of the rivers does not deprive Pakistan of its rightful share of the natural flow.Natural flow refers to the quantity of water that would pass through a river at a given point during a specific period if there were no human-made diversions, impoundments or regulation upstream. It includes direct runoff from precipitation, glacial melt, and groundwater seepage, unaffected by human infrastructure. This is the water that would reach Pakistan from the western rivers if India did not build dams, reservoirs or undertake any activity to alter the river’s course or volume.Regulated flow is the movement of water that is controlled or managed through human-made structures such as dams, reservoirs, weirs and gates. It involves opening or closing valves, adjusting spillways, or releasing water from storage to control the timing and quantity of water downstream. Under the IWT, India is allowed to build certain hydroelectric and irrigation projects on the western rivers, but these must be “run-of-the-river” schemes. This means they can temporarily hold or divert water for power generation but must not significantly alter or reduce the total flow that is reaching Pakistan.What is the allocation of water to Pakistan under the IWT?In Indus, Jhelum and Chenab rivers, 135 million acre feet or MAF per year is allocated to Pakistan, but India can use them for unlimited run-of-the-river hydropower projects such as Baglihar Dam, for irrigation of up to 701,000 acres, and storage limited to 3.6 MAF. The treaty mandates real-time flow data exchange, but disputes arise when Pakistan accuses India of withholding water during critical periods, such as in the pre-sowing season.The IWT allows India the development of 13.4 lakh acres of irrigation in Jammu and Kashmir and Ladakh. However, as of now, only 6.42 lakh acres are being irrigated in these Union Territories. Moreover, India only uses 90% of the 33 MAF it is allocated from the eastern rivers. The unutilised flow of 2 MAF from the Ravi and 5.5 MAF from the Sutlej/Beas systems has historically flowed to Pakistan due to incomplete infrastructure on the Indian side. Which of these will get affected by the suspension of IWT?The average annual flow of 135 MAF originates from glacial melt and monsoon rains, and will continue unaffected by treaty suspension. Regulated releases from India’s dams and barrages of around 3.6 MAF of storage capacity supplement natural flow during dry seasons. Suspending the treaty allows India to halt these releases, but little to no such storage infrastructure currently exists in Jammu and Kashmir for India to exercise that control. At best, only 1.5 MAF of this capacity can exist in the Baglihar Dam. India can only withhold water up to its developed storage capacity from the western rivers. This water can be temporarily held back during lean seasons but must eventually be released downstream. Without additional storage infrastructure, India cannot retain more water. Even if India builds out its full allowed storage (3.6 MAF), it could temporarily regulate and delay flows to Pakistan, especially during critical agricultural periods, but cannot permanently divert or consume this water.The challenge for Pakistan is limited water storage capacity. Major dams such as Mangla and Tarbela have a combined live storage of just 14.4 MAF, a mere 10% of the country’s annual entitlement under the IWT. In times of reduced water flow or seasonal variability, this shortfall in storage leaves Pakistan acutely vulnerable.Can it really hurt Pakistan?The western rivers derive 60-70% of their flow from glacial melt and 30-40% from monsoon rains, which India cannot control. Even with suspended cooperation, 131.4 MAF of natural flow will continue reaching Pakistan annually. During monsoon season (July-September), flow in the three rivers exceeds 5,800 m³/s (cubic metre per second), making artificial restrictions ineffective. The immediate impact is thus hard to state, but the summer of 2025 could test Pakistan’s ability to manage reduced flow during crop-growing seasons.It is in the long term that effects will be visible if India executes major projects and Pakistan does not demonstrate resilience. By developing storage infrastructure, India could gain permanent control over western rivers, compounding Pakistan’s water stress.Finally, what does all this mean?India’s ability to restrict water to Pakistan is constrained by natural hydrological cycles, infrastructure gaps, and treaty design rules. The vast majority of the Indus system’s water will continue to flow to Pakistan due to natural geography and treaty limitations, but with seasonal variations.From the western rivers, while regulated flow (3.6 MAF) can be reduced to some extent, the majority of water reaching Pakistan (131.4 MAF) flows naturally and remains beyond India’s control. Full stoppage would require massive infrastructure investment by India.