The Research Of Flood Warning And Forecast System In Small And Medium-sized Watershed In Qinling-daba Mountains

The complex terrain and geological conditions and special climate and rainfall characteristics in China lead to frequent flood disasters.Especially in a large number of small and medium-sized river areas,affected and restricted by the economic and social development,the lack of observation data,the limited monitoring means,the complex underlying surface,the damage of infrastructure and the loss of personnel and property caused by flood disaster are more serious.Based on hydrological analysis and model comparison,it is important to develop a suitable flood early warning and forecasting system for small and medium-sized rivers in Qinba mountain area.There are frequent rainstorm and flood in the construction areas of the Sanhekou Water Conservancy project and the Qinling Tunnel of the Han-to-Wei river valley water diversuon project,which are located in the middle and high mountain area.The study on flood warning and forecast of inter-basin water diversion projects can provide reliable basis for the scientific and orderly implementation of flood control plan before the occurrence of catastrophic flood.Concurrently,personnel should be organized to implement flood control measures in a timely manner to avoid or reduce heavy casualties and losses of facilities caused by flood disasters,ensure the safety of all construction areas,and lay the foundation for scientific operation and management of the Sanhekou Reservoir.Based on the monitoring data of historical water level,flow and rainfall,this study analyzes and studies the dynamics and variability of river runoff for determining the early-warning threshold of floods in the construction area.It is of great practical significance to select a flood early warning and forecast model suitable for watershed characteristics.For this purpose,this study utilizes digital elevation(DEM)technology to develop a flood forecasting system during the construction period of the Project.The main research results obtained in this study are as follows:(1)The rainstorm and flood characteristics were analyzed based on historical rainfall and runoff data,the results show that the correlation between annual runoff and average annual precipitation is good(R2=0.87),the correlation between the runoff depth(R)and the calculated average rainfall and the pre influence rainfall(P+Pa)is good(R2=0.80).The 1 h unit hydrograph of Daheba station with rainfall centers at the Jiaoxi River,Wenshui River and uniform rainfall in the whole basin were determined,and can be used for real-time flood warning and forecasting.(2)Selected and determined the 0#,1#,3#adit of Qinling tunnel and Sanhekou hydro junction dam for early warning index research based on actual survey.Considering the confluence time,station distribution,information collection and other factors,critical rainfall or water level(flow)and the corresponding early warning response time were determined by establishing the flood warning index of the small watershed.Combined with the construction progress and flood control requirements,the critical discharge of Sanhekou dam site is determined to be 2640 m3/s in 2016-2017 and 5240 m3/s in 2018.(3)Combined with the actual factors such as the location,topography,hydrology and data integrity of the study area and the application effect of the model,three hydrological models,Xinanjiang(XAJ),TOPMODEL and API were selected to prepare the model scheme.The model parameters were calibrated,based on the data of rainfall and flood and evapotranspiration,and the accuracy evaluation and error analysis were carried out through the simulation of 13 typical flood processes measured at Daheba hydrological station from 2010 to 2015.The results show that the qualified rate and forecast accuracy of model scheme meet the demand,and it is determined to carry out flood early warning and forecast based on XAJ model,TOPMODEL model and API model(4)The study constructed the real-time flood forecasting system for the construction area of the Hanjiang-to-Weihe river valley water diversion project.According to the real-time rain and the forecast of rainfall in the near-future period,the flood process,maximum discharge and occurrence time of the Sanhekou reservoir and warning flow(rainfall)of the Qinling tunnel are predicted accurately and rapidly,which provides multi-level and multi-directional accurate information for supporting the management and construction of the project.The flood early warning model constructed in this study improves the scientific and information level of flood control decision-making,and enhances the analysis and synthetical decision-making ability of flood control.