三峡水库蓄水初期寸滩站洪水预报方法研究

The Research on Flood Forecast Method of Cuntan Hydrologic Station in the Initial Period of the Three Gorges Reservoir Impoundment

寸滩站作为长江上游重要控制站,承担着上游防汛和三峡蓄水的双重任务。基于三峡蓄水初期寸滩站水力学特性发生改变和该时段“高水位、低流量”现象,发现Q≤25000m^(3)/s时,寸滩受顶托显著,Z-Q关系线发生“左偏”。在此变化条件下,分别研究了平水期、涨水期的水位、流量预报方法,即先由河道演算的流量查询预报综合线得到水位预报,进而通过水位反查报汛综合线(或绳套、临时关系线)获得流量预报。平水期,依适用条件采用落差指数或多元门限回归开展预报,成果基本能够满足防汛和蓄水需求;涨水期,以“嘉陵江2021年第3号洪水”寸滩预报为例,分析了洪水组成、Z-Q关系绳套化、洪峰水位流量错时出现、水库实时调度和下游顶托等多种因素,采用多源、多尺度水文气象耦合与预报调度一体化辅以主客观融合的人工校正技术实时预警预报,支撑长江上游水库群联合调度,降低寸滩水位约1~2.5 m.研究可为长江上游秋汛防洪和保障三峡蓄水提供支撑。

As an important control station in the upper reaches of Changjiang River Cuntan hydrologic station undertakes the task of flood control and the Three Gorges reservoir impoundment.Based on the changing hydraulic characteristics and the phenomenon of"a high water level with a low flow",the study finds that when the flow is less than 25000 m^(3)/s,the floods'piling-up is significant,and the relation curve of water level and discharge is"left deviated",which leads the previous forecasting method to be invalidity.This paper investigates the water level and flow prediction methods in both water-stable and flood period.During water-stable period,we adopt the fall exponent method or multi-threshold regression model for forecast according to its applicable conditions.During the Flood No.3 of Jialing River,we use the technology of coupled multi-source and multi-scale hydrology and meteorology,the technology of coupled flood forecast and reservoir operation,and the technology of coupled subjective and objective manual correction to execute the real-time early warning and flood forecasting.The forecast provides an effective support for the joint operation of reservoir group and it reduces the water level by about 1 to 2.5 meters at Cuntan and it guarantees the water storage of Three Gorges Reservoir.