Applications of grey relational method to river environment quality evaluation in China

Grey relational method (GRM) has emerged in recent years as a new tool to deal with problems of small samples and insufficient information. Inexact data, short sample and incomplete hydrological data in water research are very commonly encountered. Statistical, fuzzy set and rough set theories have been applied to deal with uncertainty problems in hydrology. In this paper, we propose a new algorithm for grey relational degree and apply it to water environment quality evaluation of the Han Jiang River, one of the major branches of the Yangtze River in China. Our proposed method possesses some essential and desirable properties which ensure that translational properties of relational degree do not exist and it will give a more precise and finer grading of the overall water quality. Our empirical applications of GRM have demonstrated that GRM is a useful tool for analysis of inexact data, short sample and incomplete hydrological data.