1999～ 2 0 0 0年度黄河流域凌汛期气温较常年偏低 ,宁蒙河段槽蓄增量 ( 18.6亿ｍ3 )是刘家峡水库建库以来最大值 ,头道拐站又出现了历史上少有的长时间小流量过程 ,黄河下游出现了两封两开的凌情。黄河上、中、下游封冻河段总长达 12 0 8ｋｍ ,其中宁夏、内蒙古、河曲河段封冻 During the flood season in the Yellow River Basin from 1999 to 2000, the temperature in the flood season was lower than that of normal years. The increment of tank storage (1.86 billion m3) in the Ningmeng reach was the maximum since the reservoir was built and the first round of Shoudui station appeared in history The process of small flow for a long time, the lower reaches of the Yellow River there have been two open two Lingshi. The total length of the frozen section of the upper, middle and lower reaches of the Yellow River reaches 12 0 8 km, of which Ningxia, Inner Mongolia and Hequ reach are frozen