Secondary river basins

On the basis of the information layer of the river basins at national scale 1:250,000, which is consistent with the water grid, the sub-basins relating to the I order streams with an area greater than or equal to 200 sq.km were identified, in accordance with Legislative Decree No 152/99 and subsequently by the Water Framework Directive 2000/60/EC.本数据集以与水系网格（water grid）匹配的国家级1:25万比例尺流域信息图层为基础，依据第152/99号立法令及后续施行的《水框架指令（Water Framework Directive）2000/60/EC》，识别出流域面积大于等于200平方千米的一级溪流所对应的子流域。