Abstract: Geographic Information System(GIS) gets more attention in many fields by its special function. In this paper, common problems in regional water resources assessment models are discussed at first. Then, one of GIS softwares,Arcview, has been introduced especially for its spatial analysis and contour generation. Regional precipitation, runoff and their statistic parameters are created by the contour of precipitation and surface runoff. All of these new methods are applied to the calculation of regional water resources.