Hydropower Infrastructure Performance after the 2015 Gorkha, Nepal, Earthquake Sequence

Abstract

Hydropower infrastructure, the primary source of electricity in Nepal, experienced severe damage following the 2015 Gorkha earthquake sequence, resulting in a 15% loss in the country's energy production. The performance of hydropower infrastructure during and after the sequence was one of the unique focuses of the Geotechnical Extreme Events Reconnaissance (GEER) study. The GEER team visited damaged hydropower projects along the Trishuli and Sunkoshi rivers by road and on foot, along with the ongoing 465-MW Upper Tamakoshi hydropower project by helicopter. The primary cause of damage to the hydropower infrastructure was landslide and rockfall debris falling on powerhouses, penstocks, and dam structures. Moreover, landslides blocked road access to many sites, delaying necessary repairs to damaged structures and resumption of power generation. Power production in Nepal before and after the 2015 Gorkha earthquake sequence, seismic performance of visited hydropower projects, and short- and long-term effects, together with residual risks for Nepal's hydro-power infrastructure, are discussed in this paper.

Topographic and Seismic Constraints on the Vulnerability of Himalayan Hydropower

“…The Gorkha earthquake hit Nepal in the dry season, and the following monsoon seasons led to a large number of landslides (Thapa, ). Ongoing mass movement events were reported at few HPP sites in our database (Rasuwagadhi and Upper Trishuli 3A) and delayed resumption of construction (Pehlivan et al, ). Besides these HPPs, we found no further reports indicating postseismic damage.…”

“…Ground settlement and structural damage were common in lower alluviated reaches. Steep terrain, in turn, experienced mass movements (Kargel et al, ; Roback et al, ), and rockfall, debris flows, and landslides impacted HPPs and appurtenant infrastructure such as access roads and power lines (Moss et al, ; Pehlivan et al, ; Shrestha et al, ). Based on a compilation of documented and estimated HPP losses, we show that, among these mechanisms, landslides had the largest share.…”

“…In particular, the 2015 M w 7.8 Gorkha earthquake damaged >30 Nepalese HPPs with a capacity of ~270 MW, leading to a loss of 34% of the nationally generated hydropower. The total cost of the physical damage is ~200 million USD including revenue loss during reconstruction (Pehlivan et al, ). The earthquake's estimated return period (Stevens & Avouac, ) was well below seismic design criteria for HPPs.…”

Overview of the 2015 Gorkha, Nepal, Earthquake and the Earthquake Spectra Special Issue

“…In the electric power system, transmission performed reasonably well, but generation, which is mostly hydropower, and distribution were heavily damaged. Damage to generation was dominated by the effects of landslide debris on power houses, penstocks, and dam structures, and by landslides inhibiting road access, thereby delaying service restoration (Pehlivan et al 2017). There was also approximately 800 km of distribution lines out of service (NPC 2015).…”

“…First, as in other developing countries, even before the earthquake, electric power and water supply systems were not meeting the demand in Nepal. In 2014, for example, 45% of the peak electricity demand of 1,292 MW was not being met, which resulted in load shedding of up to 11 hours a day (Pehlivan et al 2017). Similarly, the water supply was inadequate, resulting in highly intermittent service.…”