流域水质目标管理的风险识别与对策研究

以水质目标为约束和核心的管理将逐步完善、补充和强化当前的总量控制模式,成为我国中长期流域水环境管理的重要内容.流域水质目标管理是一个"响应→调控"并不断反馈调整的过程,但由于流域系统的非线性和不确定性,流域污染减排并不能完全确保水质目标的实现.本文将这种由不确定性而引致的流域水质目标的不完全可达性界定为风险,并在分析流域水质目标管理框架思路的基础上,识别并实证了水质目标管理中的主要风险来源,主要包括:1在"响应"层面,由于水质响应与负荷削减等措施间的非线性、时滞性、指标不协同等不对应关系带来的风险;2在"调控"层面,由于水环境管理缺乏适应性的调控和反馈机制而产生的水质达标风险.在此基础上,提出了流域水质目标风险管理的转变途径及其定量表征方法,以期为流域水质目标风险管理提供借鉴.

Risks and countermeasures in water quality target-oriented watershed management

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 in non-compliance of the water quality target.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 cor-responding countermeasures and solutions for risk-based WQTOM to support more efficient and reliable watershed management in China.