封河期头道拐水位与万家寨水库水位关系研究

Study on the Relationship Between Water Levels of Toudaoguai and Wanjiazhai Reservoir

头道拐水文站至万家寨库尾回水末端(拐上)河段长42 km,其间以黑圪劳湾为界,上段属平原型河道,比降较小,历史上年年封河;下段比降增大,历史上较少封河,万家寨蓄水后几乎年年封河。凌汛期间,头道拐河段水位变化是否受万家寨水库水位影响,颇受关注。分析2015年封河期头道拐至万家寨水库河段水位变化过程,得出:库区冰塞头部形成位置取决于河道条件、水库水位和河道流量;库尾冰塞一旦形成,库水位变化不对库尾冰塞产生影响;什四份弯道卡冰封河后头道拐至万家寨河段凌情趋于稳定;头道拐河段水位,流凌、稳定封冻阶段由流量决定,封河发展阶段受冰塞壅水影响,与万家寨库水位变化无关。

The river reachbetween Toudaoguai Hydrological Station and the upstream end of the backwater zone of Wanjiazhai Reservoir is 42 km long. Heigelaowan is considered as the turning point of the river bed slope from mild to steep. Before the construction of Wanjiazhai Reservoir,the reach at the upstream of Heigelaowan always formed ice cover during the freeze up period due to its mild bed slope,while that at the downstream of Heigelaowan often remained open water with surface ice run. Whether or not the backwater due to the Wanjiazhai Reservoir caused the rise of the water level in the reach downstream of Heigelaowan and resulted in the ice cover formation during freeze up is a concern. The objective of this paper was to gain the understanding of the effects of the Wanjiazhai Reservoir on the water level at Toudaoguai during freeze up. The ice jam is prone to form near the upstream end of the backwater resulted from the Wanjiazhai Reservoir. The analysis of the water level variations from Toudaoguai to Wanjiazhai Reservoir indicates that the channel geometry,reservoir water level and river discharge play important roles in the ice jam toe location; the operation of the water level in the reservoir will not affect the ice jam once the jam has formed; the channel bend at Shensifen is subject to ice jam formation which reduces the ice supply to the downstream reach between Toudaoguai and Wanjiazhai Reservoir; the water level at Toudaoguai is determined by the flow in ice run date and steady freeze-up period,influenced by backwater of ice jam in freeze-up stage of development and independent of the change of the water level at the Wanjiazhai Reservoir