2007～2008年黄河宁蒙河段凌汛成因分析

黄河宁蒙河段2007～2008年凌汛期封冻河段长,平均冰厚较厚,最大槽蓄水增量达16.95×108 m3,封河期部分河段冰塞壅水严重,三湖河口站1月25日水位达1 020.84m,3月18日达1 020.86m,均创历史记录,3月20日开河时鄂尔多斯市杭锦旗独贵特拉奎素段黄河大堤先后发生两处溃堤.其原因是河道淤积日趋严重,跨河建筑物增多和不利的河道形态等综合因素造成冰下过流能力减小,12月上旬～3月上旬兰州站来水量47.0×108 m3,较前10a同期平均偏大7.3％,以及开河期气温急剧升高,三湖河口站开河前夕连续2d槽蓄水增量释放量均＞1 100 m3/s,直接导致测站下游河段形成冰坝壅水,造成溃堤灾害.

Ice floods occurred in the Ningmeng section of Yellow River in 2007-2008

A large ice thickness and the maximum channel-storage increment of 1. 695 billion m^3 for ice flood, occurred at Ningxia-Inner Mongolia reach of Yellow River in 2007-2008. During the freeze-up period, heavily dammed water due to the ice jam occurred at some reaches and two record-breaking water level at Sanhuhekou Hydrological Staion reached to 1 020.84 m on Jan. 25 th and 1 020.86 m on Mar. 18 th respectively. During the break-up period on Mar. 20 th, two dike burst occurred at Duguitelakuisu reach of Yellow River in Hangjin Banner, ordos area. The reason for this disaster was the decreased discharging ability under the ice surface caused by the facters of heavy channel sedimentation, increase of structures crossing over river, adverse channel morphology and so on. And it resulted in an amount of 4.7 billion m3 inflow at Lanzhou Station from the first ten days of Dec. to the first ten days of next Mar. , which is 7.3 percentage lager than that at the same time of the former ten years. Adding the adverse temporal and spa tial transformation of atmospheric temperature and the dramatic increasement of the air temperature during the break-up period. , the release amount of channel-storage increment at Sanhuhekou Station exceeded 1 100 m^3/s for 2 d just before the break up date and dammed water due to the ice dam was formed downstream of the station, resulting in a disaster of dike burst.