International Rivers Law and the Indus Waters Treaty

Rivers do not stop at borders, and about half the world's land lies in shared river basins. International law governs how riparian states use shared waters, balancing the upstream state's sovereignty against the downstream state's needs. This note covers the theories, the main rules in the UN Watercourses Convention and the case law, and India's river treaties, with particular attention to the Indus Waters Treaty and its current status.

1. Kinds of Rivers and Theories

• Kinds. National rivers lie wholly within one state; boundary or contiguous rivers form a frontier; successive rivers flow from one state into another; the modern term international watercourse covers the whole system of surface and connected ground waters.

Figure 1: Theories of riparian rights

• Harmon doctrine. In 1895, US Attorney General Harmon asserted that the United States could use the Rio Grande as it wished regardless of the effect on Mexico; the doctrine has been abandoned.
• Territorial Jurisdiction of the International Commission of the River Oder, PCIJ, 1929. The community of interest of riparian states in a navigable river is the basis of a common legal right, marked by the perfect equality of all riparians.
• Lake Lanoux (Spain v France), 1957. France could divert waters upstream if it restored an equivalent flow; an upstream state must consult and take account of downstream interests in good faith, but the downstream state has no veto.

2. The Modern Rules

• Helsinki Rules, 1966. Adopted by the International Law Association, they set out equitable utilisation; later revised as the Berlin Rules, 2004.
• UN Watercourses Convention, 1997. Based on ILC drafts, it entered into force in 2014; India, Pakistan and China are not parties, but its core principles are widely regarded as customary.
• Equitable and reasonable utilisation, Articles 5 and 6. Each state uses the watercourse in an equitable and reasonable manner, weighing factors such as geography, hydrology, social and economic needs, population, existing and potential uses, and alternatives.
• No significant harm, Article 7. States must take all appropriate measures to prevent causing significant harm to other watercourse states.
• Cooperation and notification, Articles 8 to 19. A general duty to cooperate, regular exchange of data, and prior notification of planned measures that may have a significant adverse effect, with time for the other state to respond.
• Gabčíkovo-Nagymaros (Hungary/Slovakia), 1997. Czechoslovakia's unilateral diversion of the Danube under Variant C deprived Hungary of its right to an equitable and reasonable share of the river's resources.
• Pulp Mills on the River Uruguay (Argentina v Uruguay), 2010. Uruguay breached its procedural duties to inform and notify; an environmental impact assessment is required under general international law where an activity risks significant transboundary harm.
• Silala (Chile v Bolivia), 2022. The Silala is an international watercourse governed by customary law, including equitable use and no significant harm.

3. The Indus Waters Treaty, 1960

The treaty was signed at Karachi on 19 September 1960 by Prime Minister Nehru and President Ayub Khan, with the World Bank as a signatory for specified purposes, after nine years of negotiations facilitated by the Bank. Instead of sharing each river, it divides the six rivers of the Indus system.

Figure 2: Allocation under the treaty

Figure 3: Three tier dispute settlement (Article IX)

• Baglihar (2007). A Neutral Expert largely upheld India's design for the Baglihar project on the Chenab, with some modifications.
• Kishenganga (Pakistan v India), 2013. A Court of Arbitration held that India could divert waters for the Kishenganga project, but must maintain a minimum flow of 9 cumecs downstream, and could not use drawdown flushing below dead storage level in new run-of-river plants.
• Parallel proceedings. Over the Kishenganga and Ratle projects, Pakistan sought a Court of Arbitration and India a Neutral Expert; both proceeded from 2022; India took part only before the Neutral Expert, who found himself competent in January 2025.

4. Status of the Treaty

Figure 4: Recent developments

• Notices for modification. In January 2023 and again in 2024, India gave notice seeking modification of the treaty under Article XII(3), citing changed circumstances and Pakistan's conduct in the dispute process.
• Abeyance, April 2025. By a letter of 25 April 2025, India informed Pakistan that the treaty would be held in abeyance, citing sustained cross-border terrorism, Pakistan's refusal to negotiate, and changes in population, energy needs and water use.
• Court of Arbitration. In June 2025, the Court of Arbitration issued a supplemental award holding that India's decision did not affect its competence, and in August 2025 an award on general interpretation of the design criteria; India, which does not recognise the Court's constitution, rejected these.
• Legal debate. The treaty has no clause for unilateral suspension, and Article XII(4) allows termination only by a ratified treaty between the two governments; India relies on the general law on fundamental change and on Pakistan's conduct (Topic 17)

5. India's Other River Treaties

• Bangladesh. The Ganga Water Treaty, 1996 on sharing waters at Farakka during the lean season, concluded for thirty years.
• Nepal. The Kosi (1954) and Gandak (1959) agreements and the Mahakali Treaty, 1996.
• China. There is no water sharing treaty on the Brahmaputra; India and China have memoranda on sharing hydrological data.
• Domestic contrast. Disputes between Indian states over inter-state rivers are governed by Article 262 of the Constitution and the Inter-State River Water Disputes Act, 1956, not by international law.

6. Frequently Asked Questions

Can an upstream state use a river without regard to downstream states?

No. The Harmon doctrine has been abandoned. An upstream state must use shared waters equitably and reasonably, avoid significant harm, and consult downstream states, though the latter have no veto (Lake Lanoux, 1957).

How does the Indus Waters Treaty resolve disagreements?

In three tiers under Article IX: questions go to the Permanent Indus Commission, technical differences to a Neutral Expert, and disputes to a Court of Arbitration.

7. Related Topics

• Topic 17: Law of Treaties V. Termination, suspension and fundamental change.
• Topic 47: International Environmental Law. Transboundary harm.
• Topic 48: Peaceful Settlement of Disputes. Arbitration and neutral experts.