The purpose of this study was to obtain optimal amount of groundwater development for a rural small watershed. The optimal amount of groundwater development in this experimental watershed is 13.8 %(0.67 x 10⁶m³) of the annual rainfall by SCS-CN method. The Visual MODFLOW analyses showed the optimal amount of groundwater development were 14.9 %(0.72 x 10⁶ m³) of the annual rainfall.