Assessing the reliability, resilience and vulnerability of water supply system under multiple uncertain sources

Abstract

Abstract Water reservoirs often contain multiple runoff water sources, each of which is affected by a variety of uncertainties. The encounter situation defined in multiple water sources is the imbalance spatial-temporal distribution of water resources, which has a profound impact on the risk of water scarcity. This study presents a framework to evaluate the performance of a water supply system considering the encounter situations between different water sources. Based on the Han to Wei Inter-Basin Water Transfer (IBWT) project in the Shaanxi Province of China, the synchronous and asynchronous encounter probabilities are calculated using copula-based approach to characterize the encounter risks for water supply. Then, the synthetic monthly series of different water sources are generated through a synthetic streamflow-generated method based on the simulated annealing algorithm and fragment method, which is applied as the input variables of a reservoir optimization operation model. The metrics of reliability, resilience, and vulnerability are used to evaluate the performance of the water supply system. Results indicate that (1) regardless of whether the annual flow series is a full sequence or a pre- or post-changed sequence, the encounter probabilities between different water sources remain stable. However, there are obvious changes in the encounter probabilities of each month between different water sources; (2) The generated monthly flow series effectively preserves the internal composition of the historical data, which are adequate to evaluate the performance of the water supply system; (3) as the water demand increases, the reservoir’s storage capacity decreases, and the reliability of the water supply depends on the wet encounter situations for different water sources; (4) the ability to describe the states of the system varies significantly according to the metrics selected, and the choice of the metrics of reliability, resilience (max), and vulnerability (mean) can adequately describe the states of the water supply system. This study appropriately constrained the uncertain inputs of the reservoir operation model to improve the credibility of decision making.