Teesta River

The Teesta River is the largest river of Sikkim and a principal tributary of the Brahmaputra system, ranking among the most geopolitically charged rivers of the eastern Himalaya. It rises at an elevation of roughly 7,068 metres at the Tso Lhamo (Cholamu) Lake in northern Sikkim, fed by the Zemu and other glaciers descending from the Kangchenjunga massif. From its source the river runs about 414 kilometres before discharging into the Brahmaputra (locally the Jamuna) inside Bangladesh. As an antecedent river that predates the uplift of the Himalaya, the Teesta has carved deep gorges, and its name is popularly derived from "Trishrota," meaning the river of three streams, a reference to its braided headwater channels. For UPSC General Studies Paper I physical geography, the Teesta is the archetypal example of a snow-fed-plus-rain-fed Himalayan river with a perennial regime.

The river's course divides into clear physiographic segments. In its upper reaches the Teesta flows southward through Sikkim, where the Rangit River, draining western Sikkim, is its most important tributary and joins it near Melli at the Sikkim–West Bengal border. Below this confluence the river enters the gorge country and emerges onto the plains at Sevoke, near Siliguri in the Darjeeling district of West Bengal. Until the catastrophic flood of 1787, the Teesta is recorded to have flowed southward to join the Ganga system through the Karatoya channel; the flood diverted its course eastward, after which it turned to discharge into the Brahmaputra. This avulsion is a standard case study in fluvial geomorphology and river-capture dynamics. After leaving the Indian plains the river enters Bangladesh's Rangpur Division, traverses the districts of Nilphamari, Lalmonirhat and Rangpur, and merges with the Brahmaputra near Chilmari.

The Teesta has been intensively developed for hydropower owing to its steep gradient and high discharge. The Teesta Stage-III, Stage-V and Stage-VI projects, together with numerous run-of-the-river schemes, form a cascade across Sikkim, while the Teesta Low Dam projects operate in West Bengal. The Teesta Barrage Project, India's largest irrigation undertaking in the region, diverts water near Gajoldoba in Jalpaiguri district to irrigate the parched Terai tracts of north Bengal. Bangladesh operates a corresponding barrage at Dalia (Doani) in Lalmonirhat, commissioned to serve the Teesta Barrage Irrigation Project across its northern districts. The competing diversion infrastructure on both sides of the boundary is the proximate engineering reason the river's lean-season flow has become a scarce and contested resource.

The Teesta water-sharing question has dominated India–Bangladesh relations for decades. A draft interim agreement negotiated under the Joint Rivers Commission proposed allocating roughly 37.5 percent of the dry-season flow to Bangladesh and 42.5 percent to India, with the remainder left for the river. The accord was scheduled for signature during Prime Minister Manmohan Singh's visit to Dhaka in September 2011, but was withdrawn at the last moment after West Bengal Chief Minister Mamata Banerjee declined to endorse it, citing inadequate flows for north Bengal's farmers. The deadlock persisted through subsequent summits, including Prime Minister Sheikh Hasina's visits in 2017 and 2019 and again during the bilateral engagements of 2022 and 2024, with the central government in New Delhi repeatedly affirming intent while the state government's consent remained the binding constraint under India's federal water arrangements.

The Teesta is frequently confused with adjacent eastern-Himalayan rivers and frameworks, and the practitioner should keep the distinctions precise. Unlike the Ganges, whose sharing is governed by the 1996 Ganga Water Treaty signed at Farakka and valid for thirty years, the Teesta has no binding treaty at all; it remains regulated only by the consultative Joint Rivers Commission. It is also distinct from the Brahmaputra itself, of which the Teesta is merely a tributary—a point that matters because Brahmaputra-basin diplomacy additionally implicates China as an upper riparian, whereas the Teesta dispute is strictly bilateral between India and Bangladesh. The Teesta should not be conflated with the Torsa, Jaldhaka or Mahananda, the neighbouring north-Bengal rivers that share the same Terai catchment.

A significant recent development is the entry of external actors into Teesta basin management. Bangladesh advanced the Teesta River Comprehensive Management and Restoration Project, a large-scale dredging, embankment and reservoir scheme on its territory, for which Chinese financing and technical involvement were proposed. The prospect of Chinese construction activity close to India's strategically sensitive Siliguri Corridor—the narrow "Chicken's Neck" connecting the northeastern states—prompted India to offer its own assistance for the project in 2024, converting the river into an instrument of regional infrastructure competition. The river's ecology, the seismic vulnerability of its dam cascade exposed by the October 2023 South Lhonak glacial lake outburst flood that destroyed the Teesta-III dam, and the downstream desertification of Bangladesh's Rangpur belt have all sharpened the urgency of a settlement.

For the working diplomat, civil servant or desk officer, the Teesta is a compact illustration of how transboundary water, federalism and great-power rivalry intersect. Its unresolved sharing arrangement is routinely cited as the principal irritant in an otherwise cooperative India–Bangladesh relationship, and any movement on it requires aligning the interests of New Delhi, Kolkata and Dhaka simultaneously. Aspirants preparing for the civil services should be able to locate its source and course, name its barrages and tributaries, explain the 2011 collapse of the draft accord, and situate the river within the broader debate on India's lack of a comprehensive transboundary water doctrine.