Assessment and management of composite risk in irrigated agriculture under water-food-energy nexus and uncertainty

Growing demands for water, energy, and food put many systems at a composite risk of resource shortages. There was a lack of approaches capable of effectively assessing tridimensional composite risk and describing non-linear correlations among subsystem risks within a Water-Energy-Food (WEF) nexus system. In this study, an integrated approach was developed to assess the composite risk of WEF nexus systems and generate risk-based plans. Specifically, a composite risk assessment model that could capture the interdependence among the risk for water, energy, and food shortage was proposed. Furthermore, a generalized Copula-based chance-constrained programming model and its solving algorithm were developed. The proposed approach has been applied to an agricultural WEF nexus system in northern China, where the shortage of water, energy and / or land affected agricultural outputs. Results show that the composite risk of the entire system would be higher than the maximum value among subsystem risks, but less than their sum. Higher composite risks could bring higher benefits. Under a certain composite risk, the overall system benefit would vary with different combinations of subsystem risks; and it could be promoted through coordinating resources supplied by different subsystems. A risk - benefit frontier consisting of optimal solutions corresponding to different combinations of composite and subsystem risks was identified through Monte Carlo simulation. The scheme that could generate 12.76 billion Yuan under a moderate composite risk level of 0.22 was recommended for the study problem. Accordingly, net irrigation water, energy for agriculture, and effective irrigation area should be no less than 1.66 × 109 m3, 81.08 × 103 tce, and 509.12 × 103 hm2, respectively.