IMPACT OF 2015 GORKHA EARTHQUAKE ON NEPAL'S HYDROPOWER PROJECTS: A REVIEW AND LESSONS LEARNT

Abstract

Central Nepal was jolted by the M_w 7.8 Gorkha earthquake on 25 April 2015. The tremor affected 32 administrative districts of the country and killed over 8,790 people. It also caused enormous damage to physical infrastructures, including residential buildings, schools, colleges, hospitals, industries, hydropower projects, roads, and highways. Based on a post-disaster need assessment, the Government of Nepal estimated the rehabilitation and reconstruction cost at NPR 669 billion or US$ 6.7 billion. This paper provides an overview of geological setting and seismicity of the country followed by a brief discussion on impact of the earthquake on hydropower projects. The quake severely damaged surface structures like powerhouse, settling basin, penstock pipe, and access road of many operating and under-construction projects. The earthquake-induced landslide debris accumulated on hillslopes is being gradually transported each year by rainwater into the nearby river. This excess sediment load to the river further reduces the lifespan of turbines and storage capacity of reservoirs. Hence, hydropower projects are under the risk of seismic and sediment disasters for which preparedness, including policy measures, are of utmost importance. Taking lessons from the Gorkha earthquake, this paper recommends carrying out sediment-control measures in the hilly areas, install accelerometers in major hydropower projects for recording strong ground motion from future earthquakes, and revise the existing operating guidelines and seismic codes.