Multiple-risk assessment of water supply, hydropower and environment nexus in the water resources system

Hydropower has been one of the effective and reliable renewable sources utilized for electricity generation globally, which forms over 70% of all the renewable energy measures since 2016. However, this effective energy source can be greatly affected by the uneven spatiotemporal distributions of water resources in the catchment, leading to the potential risks of insufficient water supply, hydropower and ecological water uses. In this study, the multi-dimensional models by coupling water supply, hydropower generation and environment effects were developed to improve the efficiency and sustainability of water resources utilization. To this end, the joint distributions and conditional expectation models were established to analyze the nexus of water supply, hydropower and environment variables, thereby to evaluate multiple risks in the water resources system. For the validation and demonstration of the proposed method, the upper Yangtze River Basin was selected for a case study through multivariate analysis under different conditions. The application results of bivariate analysis indicated that the probability of water supply exceeding a threshold value decreases gradually with the increase of hydropower generation, which means that the risk of insufficient water supply increases with the increasing of the hydropower generation. Specifically, when the frequency of hydropower generation exceeds 90%, both the expected values of water supply sufficiency and water use sustainability will decrease sharply, causing potential risks of water supply insufficiency and environment damage at upstream of the dam. Furthermore, the application results of trivariate analysis evidenced that different combinations of hydropower generation and ecological water use may be achievable for optimally compromising the water resources supply and utilization. The results and findings of this study may provide useful implications for effective multiple function-based development of water resources, with aims to reduce the water supply risks as well as to improve the water utilization efficiency and environmental sustainability.