Assessment of the impacts of water resources allocation on the reliability, resilience and vulnerability of the water–energy–food–society (WEFS) nexus system

To ensure water, energy and food supply security in the future, examining resources shortage risks within the integrated management strategy of the water-energy-food-society (WEFS) nexus system under uncertainties is necessary. Reliability, resilience, and vulnerability (RRV) are the most popular criteria for quantifying risks. However, their current applications focus on individual systems and adopt constant resource shortage rate thresholds across different spatial scales. To consider the interconnections in the WEFS nexus system and reflect the spatial heterogeneities of resource shortage risks when estimating the RRV, this study proposed a framework for estimating the RRV of the WEFS nexus system under uncertainties through a WEFS nexus model integrating water resources allocation model. Water availability uncertainty was simulated using Monte Carlo simulation and inputted into the stochastic WEFS nexus model. The water, energy, and food shortage rates outputted from the WEFS nexus model were used to determine the RRV of the WEFS nexus system. The impacts of water resources allocation on the RRV of the WEFS nexus system were studied by investigating its response to different water resources allocation scenarios at the basin and operational zone scales. The results indicated that water resources allocation can effectively ensure water supply through reservoir operation and further decrease the shortage risk of water and food systems through its nexus. The vulnerability of the water system decreased from 15.87% to 6.71% and the RRV of the food system improved from 27.33%, 8.20%, and 13.15–69.84%, 26.17%, and 7.03%, respectively. The energy shortage risk increased with increasing energy demand, with a trade-off between water and energy systems, the RRV of which decreased from extremely low levels to 69.84%, 26.17%, and 7.03%. The water shortage risk exhibited spatial heterogeneities owing to the uneven distribution of the water regulating capacity. The water shortage risk significantly decreased in areas with sufficient water regulating capacity but remained high in areas with few water regulating capacity and further propagated from upstream to downstream through hydrologic connections. Even an insignificant water shortage can be found across the basin, risking water system and further the WEFS nexus system through its nexus. Our proposed framework for assessing the impacts of water resources allocation on the RRV of the WEFS nexus system can not only help understand the risk of the WEFS nexus system under uncertainties, but also contribute to the integrated planning and management of water, energy, and food.