| In practical projects, the boundary shape irregularity of the lake, reservoir, river and estuary area and the non-linear character of hydrodynamic equation make it difficult to get the theoretical solution of the equation, so the numerical solution has to be the only a choice. The numerical simulation is of some advantages such as low cost, quick speed, complete data, and being capable to change parameters and simulate both the real and the ideal conditions. The non-linear partial differential (integral) equation often needs to be solved in the computational hydraulics, however, the mathematical theory of its numerical method has yet not been sufficient at present, for example, the development of some theories such as the strict stability analysis, error estimate and convergence proof has been unable to keep pace with the development of the numerical simulation method. Therefore, it is necessary to test the computation results and further modify the computation method based on the comparison between the numerical solution of the linear or non-linear equations and the trial value or the computation results of typical cases. The two-dimension numerical simulation of water flow and water quality is required in most practical projects, in which two types aredivided according to the different water area. In the broad water area such as the coast, estuary, lake and large reservoir, the horizontal scale is far larger than the vertical scale, the variation of the hydraulic parameters (for instance, velocity) is smaller in the vertical direction than in the horizontal direction, and the flow field can be expressed as the average flowing value along the water depth, so the two-dimension plane numerical simulation technique of the water flow and water quality may be used in these areas. But, in some other water areas such as the narrow-deep tide channel, narrow-deep valley reservoir and narrow-deep estuary area, the vertical varies of parameters such as the velocity, temperature and concentration is far greater than that in the horizontal direction, so the two-dimension vertical numerical simulation technique should be adopted in these areas.The main contents in this paper are as follows: simulated irregular boundary and researched varies of algorithms; studied the two-dimension plane and two-dimension vertical computing; simulated water flow filed and water quality; researched algorithms and it's examples and combined with GIS tech. In two-dimension plane model the boundary fitted coordinate transformation were adopted to fit in with irregular area shape. In two-dimension vertical model a coordinate transformation were used to following the tracks of free surface and irregular topography boundary. In this paper, in order to fit in with the irregular boundary shape, and further to realize the quick forecast of the water flow and water quality, the two-dimension plane water flow and water quality model were built, in which the techniques of the coordinate transformation, alternate direction, staggered grid, linear recursion and implicit schemes were included. As for the reservoir of which the width to depth ratio is smaller, and the vertical variation of the parameters related such as the velocity, temperature and concentration is greater than their variation in the horizontal direction, the vertical two- dimension water flow model were set up, in which the water depth may change with the time and space, and when the coordinate transformation was made along the vertical direction, the variable area could be changedinto the regular one. In this model, the operator splitting technique, staggered grid technique and finite difference method were used.The two-dimension plane model and two-dimension vertical model developed have been used in practical projects, in which:In the flood simulation of Daqing City, the two-dimension plane unsteady flow model has been built to fit in with the irregular river boundary and realize the rapid forecast of the water flow. In this model, the geographic information sys...
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