1 概述1.1 我国干旱气候带大体以年降水量200～400mm 来划分。对于黄土高原地区,按照实际情况,上述指标宜改为250～500mm。年降水量小于200mm 地区为十分干旱气候带。干旱气候带和十分干旱气候带在我国占面积约为4成,分布于北方和西北及藏北等地,其中小于200mm 的地区约占上述面积的7成。干旱的核心问题是缺水,表现为“五水”奇缺。降水量少,河川径流量少,地下水少,土壤干燥,大 1 Overview 1.1 China’s arid climatic zone with an annual rainfall of 200 ~ 400mm to divide. For the Loess Plateau, according to the actual situation, the above indicators should be changed to 250 ~ 500mm. Annual precipitation is less than 200mm area is very arid climate zone. The arid climate zone and the arid climate zone occupy an area of ​​about 40% in our country, distributed in the north, northwest and northern Tibet, where less than 200mm occupies 70% of the above-mentioned area. The core issue of drought is lack of water, manifested as the scarcity of “five water”. Less precipitation, less runoff, less groundwater, dry soil, large