Contents I. Introduction
Grey systematic theory is proposed by Chinese professor Deng Jurong in 1982 [1]. In the theory, there is not only a large amount of known information called white system, but also much unknown and uncertain information called black system. The system including white system and black system is called gray system. Contaminant transport in natural river system usually occurs in varied flow fields and in anisotropic and heterogenous media. Because the applicability of analytical solutions is extremely limited for such conditions, numerical techniques are essential for underground pollution simulation. Mecarthy [2], Li et al. [3],Li & Wang[4], Basha & El-Habel [5] made much work about the uncertain issues. Among the numerical techniques, the gray numerical method has become very popular and is recognized as a powerful numerical tool. The distribution and transport of pollutants mentioned by Liu et al. [6], Chen & Wagenet [7], Xu et al. [8] in groundwater are controlled by physical chemistry and biology functions, which include advection, diffusion, dispersion, sorption, decay and biodegradation. In the courses, there is not only the known information but also uncertain information. Therefore, it can be seen as one gray system. Considering the above mechanism synthetically, two-dimensional gray model about river water pollution is built in this paper. It has the significant practical value for the research of gray simulation of river water pollution.
