Journal of Earth Science & Climatic Change
Open Access

Abstract

With the increasingly serious situation of water pollution in lakes and reservoirs, the Chinese government is changing the water environmental management strategy from merely pollutant concentration control to environmental capacity management. In this study, a new environmental capacity management system was established. This system is focused on how to calculate the load capacity for a bay of a lake and how to rationally allocate the allowable pollutant loads to each pollutant sources. The management system is composed of a two-dimensional coupled hydrodynamic-water quality model, which is developed for load capacity calculation, and a novel hierarchical allocation subsystem, which allocates the pollutant loads step by step on different levels with different principles and methods. Zhushan Bay of Taihu Lake was selected as a case study. According to the environmental management objectives and the corresponding relationship between pollutant loads and water quality from simulation, the allowable pollutant loads were calculated for TN, TP, NH3-N, and COD. To achieve the goal of meeting the class III of the NESSW, the current pollutant loads of TN, TP, NH3-N, and COD, have to be reduced. The developed hierarchical allocation subsystem for Zhushan Bay consists of 5 geographic levels. In level 0, loads are allocated to the lakeshore and runoffs. In level 1, loads are allocated to the 4 runoffs. In level 2, loads are allocated to upstream and local sources. In level 3, loads are allocated to the point and non-point sources in different towns. In level 4, loads are finally allocated to different villages.

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