Amochhu River

The Amochhu (Dzongkha: Amo Chhu; also Toorsa or Torsa in India, Machu in Tibet) is the westernmost of Bhutan's major rivers. It rises in the Chumbi Valley of Tibet's Yadong county, enters Bhutan in the upper Haa region, and flows south through Samtse before crossing into the Indian state of West Bengal as the Torsa.^[1]

The river is around 358 kilometres long in total, of which approximately 145 kilometres lie within Bhutan. It is the principal drainage of the western fringe of the country, which is geographically separated from the central and eastern basins by the Haa range. The Amochhu basin holds substantial unrealised hydropower potential and contains the Jigme Khesar Strict Nature Reserve (formerly Toorsa Strict Nature Reserve), one of Bhutan's three strict nature reserves.^[2]

Compared with the Wangchhu and Manas systems, the Amochhu has historically been the most isolated of Bhutan's basins. Its narrow, steeply incised valley discouraged the formation of large monastic estates or settlement clusters in the pre-modern period, and even today the population in the Bhutanese reach is small relative to the basin area.

Course

The river enters Bhutan from Tibet through a high-altitude saddle north-west of Haa town and runs south past Phuentsholing's western flank before exiting at the Torsa border post. It does not pass through any major Bhutanese town except the Phuentsholing peri-urban area, where it forms the western boundary of the industrial estate of Pasakha and the Amochhu Reclamation Project — a riverbank land-development scheme begun in the 2010s to expand Phuentsholing southward.^[3]

Below the border the river runs past Jaigaon (West Bengal) and through Cooch Behar district, eventually joining the Brahmaputra system in Bangladesh. The Indian reach is heavily abstracted for irrigation and is the source of the Torsa Tea Estate area's water supply.

Hydropower potential

The Amochhu basin is one of the few Bhutanese basins where no large hydropower plant has yet been built. The flagship proposal is the Amochhu Reservoir Project, a 540 MW reservoir scheme planned for the lower Bhutanese reach. The project has been included in successive India–Bhutan hydropower cooperation agreements but has not progressed to construction, with funding terms and the post-2018 review of the cross-border programme cited as principal causes of delay.^[4] A separate run-of-the-river scheme on a tributary, the Pasakha Stage Hydropower Project, has also been studied.

Two factors complicate development on the Amochhu. The lower basin abuts the Indian states of West Bengal and Assam in a low-lying area where reservoir-induced flooding is politically sensitive. The upper basin lies inside the Jigme Khesar Strict Nature Reserve, which is closed by law to commercial development.

Jigme Khesar Strict Nature Reserve

The Jigme Khesar Strict Nature Reserve, renamed in 2008 from the original Toorsa Strict Nature Reserve in honour of the Fifth King, covers 609.51 square kilometres of the upper Amochhu basin in Haa and Samtse dzongkhags. Established by royal decree in 1993, it borders Sikkim to the west and Tibet to the north, and is connected to Jigme Dorji National Park by a designated biological corridor.^[2][5]

The reserve spans an altitudinal range of 1,400 to over 4,800 metres and protects the westernmost stands of Bhutanese temperate broadleaf forest, conifer forest and alpine meadow. It contains no permanent human population. Recorded mammals include the snow leopard, red panda and Himalayan serow; the avifauna includes the Tibetan snowcock and rufous-necked hornbill. The reserve operates on a strict-protection model under the Department of Forests and Park Services, with no commercial extraction or tourism infrastructure permitted.^[5]

Communities and isolation

The Bhutanese Amochhu basin contains scattered settlements in upper Haa, Lower Haa, Samtse town and Phuentsholing's western fringe. Several communities along the river are Lhotshampa agricultural villages dating from the late nineteenth and early twentieth centuries. The terrain has historically isolated western Bhutan from the central road network: the lateral road connecting Samtse to Phuentsholing was completed only in stages between the 1990s and 2010s, and the upper Haa valley remains accessible to vehicles only through the Chuzom–Haa road built in the 1980s.

This isolation has shaped both the demographic and political profile of the basin. Western Bhutanese border communities feature prominently in the historical record of the 1864–65 Duar War and again in the 1990s displacement of southern Bhutanese populations.

References

1. Torsa River — Wikipedia
2. Torsa Strict Nature Reserve — Wikipedia
3. Bhutan Water Resources Context — Bhutan Integrated Water Resources Management
4. Status of hydropower dams in Bhutan — International Rivers
5. Toorsa / Jigme Khesar Strict Nature Reserve — Bhutan Trust Fund for Environmental Conservation
6. Toorsa Strict Nature Reserve renamed — WWF Bhutan