Research On The Disaster Risk Threshold Of Rainstorm And Flood In Jialing River Basin Based On Distributed Hydrological Model

With global warming,the ability of the atmosphere to retain moisture is enhanced,which leads to the increase of global evapotranspiration and the acceleration of water cycle.As a result,regional precipitation has changed significantly,and the frequency and intensity of extreme climate events associated with precipitation(droughts and floods)have increased.The frequent occurrence of drought and flood disasters has seriously affected the society,economy and people's life.In this paper,the semi-distributed hydrological model HBV-D,combined with the support of GIS technology,was used to simulate the hydrological process of the area above Jinxi hydrological station in Jialing River basin.Then,the relationship among area rainfall,runoff and water level was established.According to the warning water level and the safety water level of Jinxi hydrological station as critical criterions for different warning grades,the area precipitation thresholds were determined.The results are as follows:(1)From 1985 to 2014,the average annual precipitation and temperature in study area showed an upward trend,especially the average annual precipitation with a significant upward trend at a rate of 4.7mm per decade.The distribution of precipitation during the year is quite different,with abundant precipitation from May to September.The average annual runoff at the Jinxi hydrological station showed a fluctuating growth trend from 2004 to 2015.The inter-annual variation of average runoff is obvious.The high flow period is July,August and September,while the stable runoff period is from November to next June.The runoff mainly recharged by groundwater,and there is a significant positive correlation with precipitation on both the annual and monthly scales.(2)Using the meteorological data,DEM,land-use data,and field capacity data,the study area has divided into 25 sub-basins and the database of the HBV hydrological model has established.Taking 2013-2015 as the calibration period and 2010-2012 as the validation period to rate the model parameters.The results show that the Nash-Sutcliffe efficiency coefficient for calibration and validation periods were 0.68 and 0.67 respectively,the correlation coefficients for both periods were 0.82,and the water balance coefficients were 1.0 and 0.94 respectively.It indicates that the HBV model has better applicability in study basin,and can be used for hydrological simulation of the region.(3)Through the HBV model,the relationship among area rainfall,runoff and water level was established.According to the warning water level and the safety water level of Jinxi hydrological station as critical criterions for different warning grades,the area precipitation thresholds curves were determined.And the validity of the area precipitation thresholds curves was verified by the flooding process on July 24,2010.The research indicates that the HBV model has good applicability in the Jialing River Basin,and can be used to simulate watershed runoff processes.On the basis of the model,the critical rainfall curve is efficient in flood warning,and this will provides some references about rain-caused flood hazard for meteorological department.