The Yarlung Tsangpo–Brahmaputra River is one of Asia’s major transboundary river systems, originating in the Tibetan Plateau and flowing through China, India, Bhutan and Bangladesh before entering the Bay of Bengal. Its hydrological significance is accompanied by considerable ecological, socioeconomic and geopolitical complexity. For downstream India, particularly the north-eastern states, the river is simultaneously a source of water, agriculture, hydropower and livelihood security and a major source of recurrent flood and erosion hazards. In this context, hydrological information is not merely a technical resource but an important instrument of transboundary water governance.

This paper examines the institutional evolution, scope and limitations of hydrological data sharing between India and China in the Yarlung Tsangpo–Brahmaputra basin and analyses its implications for India’s flood management and water security. The study is based on qualitative analysis of secondary data, including bilateral Memoranda of Understanding (MoUs), government documents, hydrological reports, international institutional publications and peer-reviewed academic literature. The analysis demonstrates that India and China have established mechanisms for the exchange of hydrological information, including data on water level, discharge and rainfall from selected upstream stations. However, the existing arrangement remains primarily oriented towards seasonal flood forecasting rather than comprehensive, real-time and basin-wide water governance. The spatial representativeness of the existing stations, restricted temporal coverage, limited institutionalisation and absence of a comprehensive multilateral basin mechanism create significant information asymmetry.

The paper argues that India’s downstream hydrological monitoring capacity cannot fully compensate for limited access to upstream observations. At the same time, the evidence does not support simplistic claims that upstream infrastructure will automatically cause downstream water scarcity. Rather, the principal concern is the management of uncertainty associated with changes in flow timing, extreme events, sediment dynamics, ecological processes and infrastructure operations. The paper therefore proposes a three-level framework comprising technical data exchange, scientific cooperation and basin-level diplomatic dialogue. Strengthening predictable and transparent hydrological data sharing, integrating satellite-based observation with ground measurements and developing a multilateral Brahmaputra information architecture can significantly improve flood preparedness and long-term water security.