| It is of great significance for regional soil and water conservation planning and watershed management to study the rules of runoff and sediment loss in slope-watershed system.In this study,artificial simulated rainfall and SWAT model were combined to study the law of water and sediment loss at different spatial scales in the Yanhe river basin,and the runoff-sediment correlation and its spatial scale effect in different catchments in the Yanhe river basin were preliminarily explored.The main conclusions are as follows:(1)The indoor artificial simulated rainfalls were applied to examine the rules of runoff and sediment loss under six different rainfall intensities of 45-120 mm/h and five different slopes of 5°-25°.The runoff under each rain-intensity increased gradually with the extension of the rainfall duration.The runoff under rain-intensities of 60,75,105 and 120mm/h in 25°slope surface were 1.54,1.34,1.31 and 1.06 times that of 5°slope surface,respectively.It can be seen that the runoff gap of 5°and 25°slope decreased with the increase of rain-intensity.There is a significant quadratic polynomial relationship between runoff yield and slope under each slope surface,R~2 above 0.83.In the first 10 minutes of uniform runoff under different rainfall intensities,the growth rate of runoff was large,but the sediment yield tended to decrease.After runoff production for 10 min,the changing trends of runoff increased slowly and gradually became gentle,and the changing trends of sediment yield under different rainfall intensities and slopes were different with the extension of rainfall duration.The sediment yield under the same slope did not change with the increase of rainfall intensity,but the sediment yield under the same rainfall intensity increased with the increase of slope.(2)The SWAT model is adopted to simulate the runoff processes in each hydrological stations of Yanhe river basin.Ansai station of regular rate is 1984-1991,validation period is1992-1998,jujube,Yan'an,Ganguyi station of regular rate is 1974-1982,validation period is1983-1988,the results show that the river apricot,jujube,Ansai,Yan'an,regular Ganguyi station rate NS were 0.53,0.58,0.54,0.68,0.73,validation period of NS were 0.51,0.55,0.54,0.66,0.61.The annual runoff of each hydrological station increased with the increase of catchment area,and the measured and simulated runoff of Yan'an station and Ganguyi station changed more obviously than that of the other three stations.The measured runoff from May to July showed an increasing trend in each station.With the increase of catchment area,the average growth rate was successively 131.06%,168.49%,122.29%,171.43%and 130.00.However,the growth rate of simulated runoff in this period only showed an increasing trend in Xinghe station and Yan'an station,while the growth rate of simulated runoff in other stations showed a decreasing trend.There is no regular change trend between the annual precipitation,measured and simulated annual runoff depth of each station,but the fluctuation is continuous.There was a significant linear relationship between measured runoff and sediment discharge in each station from June to September,R~2 is in the range of 0.80~0.91,the runoff-sediment correlation was stronger in July to August at each hydrological station,and its R~2 is in the range of 0.86~0.95,and with the increase of catchment area,the linear relationship between runoff and sediment discharge gradually weakens.(3)The change of forest land,grassland and cultivated land in the controlled catchment area of each station in 1995 was lesser than that in 1985.The curve of runoff simulation under the two-year land use data of each station almost coincides with each other,and the change trend of runoff is consistent with that of precipitation.Under the land use condition from 1985 to 1995,the average annual runoff of Xinghe station in 1985 was 5.65 m~3/s,0.02m~3/s less than 1995,the annual runoff of Zaoyuan station presented a change trend of increase,while that of Ganguyi station was contrary to that of Zaoyuan station,both of Ansai station and Yan'an station showed a continuous decrease trend.The sediment transport scale in the control catchment area of each station shows the trend of interannual fluctuation.As the catchment area increases,the fluctuation range of sediment transport amount in each station also increases gradually,and the fluctuation range is(0.10~0.69)×10~7 t?(0.02~1.37)×10~7 t?(0.18~2.18)×10~7 t?(0.45~5.91)×10~7 t?(1.53~8.42)×10~7 t.(4)The ratio of the measured runoff and the ratio of the simulated runoff respectively with the ratio of the corresponding catchments area has significant linear relationship,and R~2 is 0.98,but the ratio of the measured sediment discharge and the ratio of the corresponding catchments area have been more apparent,the R~2 is 0.54,according to all stations runoff,sediment discharge and the relation of the catchment area forecast of runoff,sediment loads.The measured annual average runoff growth rate of each station showed no obvious change trend with the increase of catchment area.Except Zaoyuan station,the annual average sediment transport growth rate of the other four stations decreased with the increase of catchment area.Yan river basin runoff,sediment and watershed area are available between fractal theory for spatial dimension measurement,runoff,sediment discharge and the catchment area of the double logarithm curve of R~2 is about 0.97,0.98respectively,the runoff,sediment of fractal dimension were 1.53,1.57,and stability index were 0.03,0.07,shows that runoff distribution form is good,and the sediment discharge space distribution shape is complex,but the spatial structure stability of runoff and sediment discharge is poor. |
PDF Full Text Request