Emergy-based sustainability evaluation of two hydropower projects on the Tibetan Plateau

Abstract

The abundance of hydroenergy resources on the Tibetan Plateau initiated a rapid increase in the development of hydroelectricity, which may severely impact its fragile ecosystem. This study selected the Pangduo hydropower project on the Lhasa River and the Dagu hydropower project on the Yarlung Tsangpo River in Tibet for a case study. Resources for the construction and operation of two hydropower projects were integrated into an emergy accounting system in addition to both ecosystem service losses and social disruption. This enabled the comprehensive evaluation of the environmental sustainability of the case-study hydropower projects on the Tibetan Plateau in the year 2016 using an emergy analysis approach. This study also compared emergy-based indices with several other hydropower projects to analyze the environmental impact of hydropower development. The results showed that the majority of total emergy yield in both Pangduo and Dagu were related to hydroelectricity generation. Ecosystem service losses of Pangduo (1.49 × 1020 sej) and Dagu (3.85 × 1020 sej) formed the largest emergy flows, which accounted for 29.8% and 23.5% of their total emergy inputs, respectively. As indicated by emergy-based indices (i.e., emergy investment ratio, renewable fraction of emergy use, emergy yield ratio, environmental loading ratio, and emergy sustainability index), both Pangduo and Dagu are less sustainable than comparable hydropower projects in China and worldwide, which could be partly attributed to calculation differences. The results indicate that beyond maximizing the benefits of hydropower systems, it is also necessary to minimize ecosystem service losses.