Risks and Countermeasures in Water Quality Target Oriented Watershed Management

Xiaoling Zhang, Zhongyao Liang, Yong Liu, Rui Zou, Feifei Dong, Huaicheng Guo, Lei Zhao, Bin He

Abstract: The total pollutant load control program currently implemented in China will be supplemented by the water quality target-oriented management (WQTOM) to form the framework for future watershed management. The WQTOM is essentially a feedback control procedure involving quantification of the water quality response to specific control measures, and make adjustment to the management based on the actual system feedback until the water quality target is achieved.  However, due to the nonlinearity and uncertainty in watershed systems, it is impossible to derive an exact quantification of the water quality response to a load reduction scheme, hence any developed watershed management scheme would be subjected to various degrees of risks of not achieving the water quality target compliance.  A methodological framework and conceptual model is proposed for risk-based water quality management in this study. The water quality target compliance risks are identified as (a) risks in water quality responses due to the nonlinear and time-lag effects of water quality response to load reduction, and the unbalanced strategy on watershed pollutants control; and (b) risks in watershed control and management resulted from the lack of adaptive regulation and feedback. We then propose the corresponding countermeasures and solutions for risk-based WQTOM to support more efficient and reliable watershed management in China.

Key words: Water Quality Management; Risk; Uncertainty; Adaptive Decision; Simulation-Optimization Model