Discuss why basin-level, rather than project-level, environmental impact assessment is necessary for riverine biodiversity conservation in the Himalayan region.

Environmental clearance in India is granted project by project, so each dam is judged on its own footprint. In the Himalaya, where a single river carries a cascade of hydroelectric schemes, this fragmented lens systematically underestimates ecological cost and endangers riverine biodiversity.

Cumulative impacts are invisible at project scale

• One run-of-the-river scheme may seem benign, but a cascade collectively alters flow regime, sediment load and turbidity along the entire river, destroying the shallow, clear, fast-flowing stretches that specialist fauna depend on.
• MoEFCC itself commissioned carrying capacity and cumulative impact studies for the Lohit basin [1] and the Beas sub-basin [2] — an official admission that project-level appraisal is insufficient.
• River continuum fragmentation — blocked fish migration, dewatered stretches between barrage and powerhouse — is a basin-scale effect no single EIA captures.

Species are basin-distributed, projects are point-located

• The Critically Endangered white-bellied heron (Ardea insignis), an obligate fish-eater of clear rapids, survives globally in fewer than 60 birds [3], with only 6–9 individuals in India, concentrated in Arunachal Pradesh's Lohit system [4].
• The 1,200 MW Kalai-II project on the Lohit received in-principle forest clearance although the heron reportedly did not figure in the list of impacted species [4] — a point assessment cannot perceive a population spread across a basin.

Integrity of assessment and offsets

• Compensatory afforestation for such projects is often sited far outside the affected basin, restoring tree cover but not riverine ecological function [4].
• Precedent: the Wildlife Institute of India's cumulative assessment of the Alaknanda–Bhagirathi basins found a large share of proposed projects would cause irreversible biodiversity loss — a conclusion no individual EIA had reached [5].

Basin-level assessment is therefore not an additional formality but the correct scientific unit for a connected, flowing ecosystem. Making cumulative and carrying-capacity studies a binding pre-condition for clearance, with mandatory environmental flows and in-basin restoration, would align hydropower expansion with SDG-15 and Article 48A's mandate to protect the natural environment.