Model Construction And Parameter Regionalization Of Typical Jialing River Basin

The Jialing River is the second largest tributary of the Yangtze River.It is divided into three sub-basins:the Qujiang River Basin,the Fujiang River Basin and the Jialing River mainstream.It is also an important source of flood and sediment in the Three Gorges Reservoir in China.The terrain and geological conditions in the basin are complex,and the rainfall distribution is uneven during the year.Small and medium-sized basins are prone to flood risks,and most areas lack runoff observation data,resulting in insufficient flood and hydrological simulation accuracy.Therefore,this paper takes nine typical watersheds in the Jialing River Basin as the research area.Based on the data of rainfall runoff,DEM and land use,the runoff and confluence model is constructed from four aspects:model input,surface runoff,underground runoff and dry season runoff.Then,Hufeng,Pingwu,Jiangyou and Shehong are used as verification basins to explore the regionalization scheme of model parameters suitable for the ungauged areas of Jialing River Basin.Through the above research,the regionalization law of Jialing River Basin parameters is revealed,in order to provide scientific basis and technical support for the accurate prediction of hydrology and flood disasters in ungauged areas.The main conclusions are as follows:(1)The climate differentiation characteristics of topography and geomorphology in different scales are revealed.The three-dimensional fractal dimension and the coefficient of variation of topographic elevation gradually decrease with the increase of watershed scale.Based on the terrain humidity index distribution curve,it is judged that the typical watershed selected in the study area has a consistent runoff process.(2)The hydrological model of runoff yield and confluence in the basin was constructed and improved,and the model application and adaptability evaluation were carried out.The NRCSCN runoff model was optimized,the initial loss coefficient was selected as 0.05,and the CN value was checked by the table method.The surface runoff calculated by confluence is determined by geomorphic instantaneous unit line and dimensionless unit line.The underground runoff is estimated by linear reservoir method,and the flow in dry season is determined by regression curve method.Through simulation verification,the average qualified rates of SCSGIUH model field simulation in Wan’an,Lizikou,Zitong,Santai and Shehong watersheds were 90%,96%,76%,79%and 100%,respectively,and the average prediction level reached Class B accuracy.In the daily scale simulation,the average NSE of SCS-GIUH model at small,medium and large scales was 0.7,0.61 and 0.63,respectively.SCS-GIUH is suitable for runoff yield and concentration simulation of typical watersheds in Jialing River Basin.(3)The parameter regionalization scheme suitable for the typical basin of Jialing River is clarified.The accuracy of parameter transplantation is ranked as LASSO model>stepwise regression>attribute similarity method>spatial proximity method.The LASSO model has a median Nash coefficient of 0.7 in the validation basin,so the LASSO parameter regionalization scheme is suitable for the typical basin of Jialing River.