New Delhi: The National Green Tribunal (NGT) has intensified its scrutiny of the rising threat of Glacial Lake Outburst Floods (GLOFs) in the Indian Himalayan region, following detailed disclosures by the Ministry of Jal Shakti on glacial lake expansion due to climate-induced melting.
The Central Water Commission (CWC), in its affidavit dated July 8, 2025, informed the Tribunal that it has analyzed 100 glacial lakes larger than 10 hectares. Of these, 34 lakes show an increasing trend in water spread area, a development the Tribunal noted with concern due to its potential to trigger catastrophic flooding events.
The CWC has developed a risk indexing framework that evaluates lake size, slope stability, and downstream vulnerabilities such as human settlements and infrastructure. Applying this framework, one lake in Sikkim has been marked under the highest risk category (Category-1).
The analysis also revealed the presence of 67 dams along the flow paths of these glacial lakes, emphasizing the potential for widespread downstream impact in the event of a GLOF.
Recognizing the importance of scientific expertise in mitigation planning, the Tribunal formally impleaded the National Institute of Hydrology (NIH) as a party to the proceedings and has granted it four weeks to file a detailed affidavit suggesting remedial measures.
In its order dated April 23, 2025, the Tribunal had impleaded the Ministry of Jal Shakti as respondent and presented a detailed analysis conducted by the Central Water Commission (CWC) on 100 glacial lakes larger than 10 hectares across six Himalayan states and Union Territories.
According to the CWC’s findings, 34 of these lakes are showing an increasing trend in water spread area, raising concerns of overflow or bursting.
The highest number of increasing trend lakes were identified in Sikkim (15), Himachal Pradesh (6), and Jammu & Kashmir (5). Importantly, the analysis also mapped the potential impact zones by marking major dams and hydrological observation stations along the lakes’ flow paths — revealing that 67 dams lie downstream of these lakes.
To better assess the threat, the CWC has developed a Risk Indexing Criteria that evaluates the likelihood of lake failure and potential downstream damage.
Lakes were categorized into four risk levels based on various parameters, including lake size, stability, and surrounding vulnerabilities like human habitation and infrastructure.
The risk categorization flagged Sikkim with one glacial lake in the most hazardous Category-1 (score above 70), while several others across Himachal Pradesh, Jammu & Kashmir, and Uttarakhand fell into moderate-to-low risk brackets.
The CWC also disclosed that it has so far approved GLOF studies for 90 infrastructure projects, with nine of these studies conducted directly by the Commission on a consultancy basis.
Highlighting the need for expert input, the Tribunal observed that the National Institute of Hydrology (NIH), which serves as Secretary to the GLOF Monitoring Committee, must be formally involved in the matter.
NIH has now been impleaded as respondent no.6 and granted four weeks to file its affidavit with specific suggestions and remedial measures. The Tribunal has directed the Registry to amend the memo of parties accordingly.
