Dhankuta, Nepal. Proper climate and hydrological risk assessment is crucial for managing multi-hazards risks in the hydropower sector. (Sharmila Dhungana/ICIMOD)

The Hydropower Transboundary Working Group (TWG) under the Koshi Disaster Risk Reduction Knowledge Hub (KDKH) organised a webinar to highlight multi-hazard vulnerability and risk in the hydropower sector and impacts on projects using selected case studies. The webinar shed light on how integrated geo-hazards assessment, which can be done in stages, is essential for hydropower sustainability. Fifty-six participants from government agencies, the private sector, and the UN, along with KDKH transboundary working group members and academics, learned about multi-criteria analysis for assessing the potential for glacial lake outburst floods (GLOFs).

The webinar, supported by the World Bank, was facilitated by Neera Shrestha Pradhan (ICIMOD) and moderated by Vishnu Pandey (CWRS). John M. Reynolds, Senior Advisor to the World Bank on the Arun Valley Disaster Risk Management Roadmap Development Project, Nepal, delivered a presentation on the importance of the multi-hazard risk management approach in the hydropower sector in Nepal and how it can be customised for Nepal and the Arun River basin. This was followed by interactive discussion session.

The participants and speakers discussed the impact of climate change and the importance of having a proper climate and hydrological risk assessment in parallel to identifying the physical process and the role of climate change to the specific events. Furthermore, the speaker highlighted the government’s role in breaking bottlenecks in interventions and managing risks by contributing to policy, governance, as well as gathering and sharing information among stakeholders.

Integrated geo-hazards assessment for risk management

During the presentation, Reynolds spoke about different types of natural disasters prevalent in the region (earthquakes, cloudbursts/heavy rainfall, rock/ice avalanches, and ice dam failure) that lead to various flood events. He also highlighted the importance of having knowledge on the scale of such events and the types of the hazards – geo-physical, hydrogeological, or geological.

Reynolds discussed the importance of understanding multi-phase geo-hazards and their cascading impacts on hydropower projects by showcasing the examples of the Chamoli disaster of 7 February 2021 and the Upper Bhotekoshi floods of 2016. The Chamoli event was predominantly mud flow triggered by large rock avalanches coupled by rock slide, which damaged Tapovan Vishnugad Hydropower Plant. The Upper Bhotekoshi event was a composite rainstorm burst event with cascading small GLOFs, landslides, LDOFs, and release of 2–2.5 million m³ of water and debris. This event damaged key structures of the Bhotekoshi Hydropower Plant in Nepal in about 20 minutes, causing loss of over USD 112 million, in addition to the loss of energy production for 18 months.

Hence, integrated geo-hazards assessment is essential, and this can be conducted in different stages, starting with the identification of the events in the catchment, followed by the assessment of physical processes (such as event triggers, site/environment conditions, and possible sensitivity) identification. The third step is to include the specific event types (glacial hazard, seismicity, location of active fault, climate change), followed by development of a risk register and resilience building in terms of risk management plans. The final step is to prepare the disaster risk management (DRM) action plan (e.g., mitigation, avoidance). The DRM action plan should be developed along with the local communities and authorities and in tandem with the emergency response plan for hydropower projects, along with communication plans, which should be updated based on the environmental conditions. This assessment is applicable at any stage of hydropower projects, and at any scale, that is, a specific catchment or the entire country. This helps manage multi-hazard risks in the hydropower sector. A successful approach in managing multi-hazard risks was demonstrated 22 years ago in Tsho-Rolpa in Rowling, Nepal, where an open canal was controlled by sluice gates and syphons.

The speaker proceeded to provide an example of multi-criteria analysis of glacial lakes to identify potential GLOFs using thresholds parameters (area, freeboard, channel: dam width ratio and width: height) and the triggered parameters (ice cliff, avalanches, thermokarst, gradient, or other factors) for each glacial lake. Each parameter is then given a weightage score to constitute a ranking system highlighting hazards. Participants pointed out that this could also be helpful from the government perspective as it allows categorising glacial lakes and conducting assessments.

About the Hydropower TWG

The KDKH is a platform led and driven by its members to foster transboundary collaboration on disaster risk reduction and explore interlinkages among science, policy, and practice mainly in the Koshi basin area. The Hydropower TWG, one of eight transboundary working groups of the KDKH, is led by the Center for Water Resources Studies (CWRS), Institute of Engineering (IoE), and Tribhuvan University and run with secretariat support from ICIMOD. The newly formed group focuses on assessing multi-hazard vulnerability and risk in hydropower sector; identifying potential ways of enhancing the resilience of hydropower to changing climate; enhancing collaboration in terms of research, publishing, and advocacy; and dissemination to promote the concept of resilient hydropower.

Nisha Wagle

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