Emergy theory to quantify the sustainability of large cascade hydropower projects in the upper Yangtze

Abstract

Cascade development of hydropower projects in a river basin can fully enhance the utilization of hydropower resources. Yet, the impacts of cascade hydropower projects on river ecosystems and social-economic systems are not well elaborated. The current research proposed an emergy estimation method to evaluate the environmental sustainability of two large hydropower projects and suggest the reasonable scale of hydropower development at river basin scale. Unlike traditional approach that used a single hydropower project as a system, the method took river reach as a system. The cascade hydropower development in lower Jinsha River, the river reach in the upper Yangtze River in China, were taken as the case study to apply the method. The results shown that at current level of construction and management, the development of Xiangjiaba and Xiluodu are still sustainable but insufficient. And the scale of large hydropower development in the lower reaches of the Jinsha River is suggested to be 29000 MW to 54000 MW. Then the transformity of hydroelectricity would be 9.50E+04seJ/J to 6.85E+04seJ/J. The Emergy sustainability indicator (ESI) decreases with the increasing of development scale, ESI would be 6.5 in the case of current development plan (45200MW), which means a good utilization efficiency and sustainability. However, the on-grid electricity price was suggested to increase to 0.40 CNY/kW•h for the reason that fair price of the electricity is higher than the on-grid electricity price. Such evaluation results could have a greater reference for hydropower planning in river basin. We believed that this approach can help policymakers and stakeholders make more reliable decisions in hydropower planning.