EMergy accounting for the Three Gorges Dam project: three scenarios for the estimation of non-renewable sediment cost

Abstract

Dam construction conflicts are typically multidimensional, complex, and dynamic. Until recently, the environmental impact assessment of large dam projects was not fully acknowledged due to the uncertainty of the issue and the current knowledge on the accountability of ecological services. The measurement on the sustainability of the production system with a holistic view are thus of great relevance for the decision makers to implement the sustainable energy policy. In this paper, an integrated EMergy accounting was presented for assessing how the Three Gorges Dam project has performed based on the sustainability criteria. We quantified each EMergy flow component of energy, material and purchased input with available data in an assumed 100-year lifetime run. Special attention is focused on three simplified scenarios for estimating the EMergy cost of sediment. Our results showed that when the EMergy cost of sediment was counted, the Environmental Sustainability Index decreased dramatically with the increasing of the nonrenewable input. The results serve as a reminder of the necessity to apply different transformities for sediment EMergy cost in any hydro project, depending on the unique ecological service of sediment in the local river system. However, due to the high intensity of local renewable EMergy flow, the Environmental Loading Ratios and the Investment Ratios of the Three Gorges Dam system were relatively low. In spite the fluctation, the Environmental Sustainability Index remained higher than that of China in 1996, no matter the sediment EMergy cost was included or not.