Inexact Optimization Model for Supporting Waste-Load Allocation in the Xiangxi River Basin of the Three Gorges Reservoir Region, China

In this study, a large-scale inexact two-stage waste-load allocation (ITS-WLA) model is developed to identify desired decision alternatives for supporting economic development and water quality management. In this model, uncertainties expressed as both probability distributions and discrete intervals are incorporated within a general optimization framework. A two-step interactive solution algorithm is used to generate interval solutions, and four scenarios are developed to examine tradeoffs between system benefits and system-failure risks. The ITS-WLA model applied to a case study in Xingshan County, China. Because of the extensive impacts of the Three Gorges Reservoir (TGR), the largest newly built reservoir worldwide, Xingshan County is facing many challenges in formulating development strategies. It is thus desired to develop effective decision-support tools to help local decision makers identify strategies to balance economic development and water-quality protection. This study represents a first attempt to apply inexact optimization approaches to a real-world waste-load allocation case at the watershed level in TGR. The results could provide scientific bases for supporting water-quality management and sustainable development.