降雨径流分布式水文模型中基于物理基础坡面和河道汇流模型及与实测水文资料同化研究

Flood forecasting is an important technical measure of flood prevention and control. The flash flood monitoring, forecasting and warning system for medium and small rivers has been launched and a number of relevant water-level telemetry stations have been established since 2010 in China. The flood forecasting accuracy was constrained by the rainfall-runoff forecasting accuracy. The rainfall-runoff models for flood forecasting have been developed to the physically-based third generation in the United States and Europe. However, the conceptually-based second-generation models are still used in China, especially the hillslope runoff concentration and channel routing models. In order to improve the flood forecasting accuracy, the hydraulic-based hillslope concentration and channel routing model will be built in this project by learning from the theory of the third-generation distributed rainfall-runoff models and assimilating the observed hydrological data with the use of the ensemble Kalman or particle filter method. In the new model, the basin is divided into unit by the natural sub-catchment nested with grid, and it is means that the basin is divided, at first by the method of natural sub-catchment, and then the a sub-catchment is subdivided and nested by the orthogonal grid and this is called the sub-catchment nested with grid. In new hillslope runoff concentration models kinematic wave method and Darcy’s Law will be employed respectively to represent the overland flow and interflow concentration. The kinematic wave or diffusion wave methods will be used to describe channel routing according to the river gradient. The hydrological data of water stage and soil water conten obtained from the medium and small rivers flood warning system will be assimilated into the hillslope concentration and channel routing model. The model parameters will be estimated by the watershed elevation, soil and vegetation types and river’s cross-section characteristics. The calculation spending time of flood forecasting for next 1-2 days by the flow concentration models and data assimilation methods will be less than 10-20 minutes and the results could be used in the real-time flood forecasting and warning.

洪水预报是防洪减灾中重要的技术措施，从2010年开始进行全国中小河流与山洪监测及预警预报，建立了大量水位遥测站。降雨~径流预报精度制约了洪水预报的精度。在用于洪水预报的降雨径流模型方面，欧美已发展了基于物理基础的第三代，我国还是基于概念性的第二代，特别坡面与河道汇流。借鉴欧美第三代分布式降雨径流水文模型理论,并采用基于集合卡尔曼滤波等方法对实测水文资料进行数据同化，研究基于水力学的坡面和河道汇流模型及与实测水位流量资料同化以提高洪水预报精度；采用单元子流域嵌套正交网格方法划分流域，地表与壤中流坡面汇流分别采用运动波和达西定律，根据河道比降确定河道汇流采用运动波或扩散波方法，充分利用中小河流预警系统建设大量水位土壤含水量等实测信息同化水文模型。模型参数根据流域DEM、土壤植被类型及河道断面特征估算。汇流模型及资料同化方法预报一次洪水的计算时间要小于10-20分钟，能够用于实时洪水预警预报。

洪水预报是防洪减灾中重要的技术措施，从2010年开始进行全国中小河流与山洪监测及预警预报，建立了大量水位遥测站。降雨~径流预报精度制约了洪水预报的精度。在用于洪水预报的降雨径流模型方面，欧美已发展了基于物理基础的第三代，我国还是基于概念性的第二代，特别坡面与河道汇流。借鉴欧美第三代分布式降雨径流水文模型理论,并实时校等方法对实测水文资料进行同化，研究基于水力学坡面和河道汇流模型。模型参数根据流域DEM、土壤植被类型及河道断面特征估算，研究的汇流模型及资料同化方法预报一次洪水的计算时间要小于10-20分钟，能够用于实时洪水预警预报。在流域中各级河宽特征估计、新的河道流量演算方法、新安江模型改进（XAJ-DCH）、根据下垫面与河道通知估算河网汇流方法与参数、半湿润半干旱地区蓄超组合的产汇机理、中小河流无资料地区参数规律研究与应用、半湿润与半干旱地区产汇模型及集合预报、网格精细化模型中汇流方法以及资料同化实时校正研究的等9个方面。特别改进新安江河道汇流及半湿润半干旱产汇流机理方面的研究在实际生产中得到了应用，为科技部重大专项中小河流洪水防控技术与示范应用（2018YFC1508100）项目的申请与研究起到了重要的技术支撑作用。把几种新的汇流方法引入新安江模型的过程中，实现子流域汇流与网格河道汇流之间的耦合，改进之后的模型河道汇流参数可根据河道真实情况以及河道糙率进行估算，可计算出各河道断面的水位和流量，XAJ-DCH模型中加入的扩散波方法考虑了回水的影响，适用范围更广。根据流域的主导水文过程，采用空间灵活组合建模方法，探索适用于半湿润半干旱地区的空间组合模型。采用该技术研发的栅格水文模型，有效地提高了半干旱半湿润和人类活动影响较强地区的洪水模拟预报精度。应用到海河大清河流域，把原来预报方案的率定精度从合格率的40%增加到60-70%。