Hydropower development in the Himalaya: identifying critical river stretches

Area of Science:

• Ecology
• Environmental Science
• Hydrobiology

Background:

• The Alaknanda River hosts two operational hydroelectric projects.
• Riverine ecosystems are susceptible to impacts from anthropogenic activities like hydropower generation.

Purpose of the Study:

• To bio-assess the health of the Alaknanda River ecosystem downstream of hydroelectric projects.
• To evaluate the impact of hydropower projects on riverine diatom communities and water quality.

Main Methods:

• Bio-assessment using diatom indices (IPS, IBD, TDI, IDS/E) and van Dam ecologic values.
• Analysis of samples from three key river stretches: Birahi (S3), Narkota (S5), and Bagwan (S8).
• Computation of ecological parameters using OMNIDIA software.

Main Results:

• Diatom indices indicated mild pollution in upper and lower stretches, with elevated pollution at Narkota (S5).
• Moderate organic pollution was detected at S3 and S5 (TDI), while IDS/E showed low degradation.
• Environmental variables indicated persistent impacts from organic/nutrient load and altered flow regimes.

Conclusions:

• The Narkota stretch (S5) is in a critical state, characterized by eutrophication and moderate oxygen levels.
• The river stretches were classified as 'polyoxybiontic-cum-mesotrophic' (S3, S8) and 'moderate O2-cum-eutrophic' (S5).
• Findings highlight the significant organic and nutrient load affecting the river section near the Srinagar dam.