Developing surface water quality standards in China

A methodology for setting lake nutrient standard was proposed in this study based on review of water quality standards (WQS) in China and understanding of lake nutrient criteria. There are very few studies about lake nutrient criteria and water body classification system, which may cause difficulties in nutrient level assessment and management. This paper reviewed WQS system in the US, EU, and Japan, and then presented the development procedures for revising surface WQS in different periods in China. The amendment includes indicators, standard values, and framework of the standard system. However, current WQS set in light of the criteria and standards of the US and Europe couldn't adapt to the natural conditions of lakes in China. Therefore, by learning from the water quality criteria setting method of USA and taking the regional differences into consideration, a methodology of combining structure equation model and expert elicitation was recommended for setting WQS. Furthermore, it considered to investigate the differences (climate, elevation and geographical condition, etc.) in each region, and set lake nutrient criteria and standards on regional scale. Consequently, the proposed methodology for setting standards could be applied to each region in China. Yungui ecoregion was taken as an example for setting up the lake nutrient standards with considering TP, Chl-a, TN and CODMn four influence factors for designated use attainment, and a suitable TP standard 0.02 mg/L was recommended by using the proposed methods.