Study On Snowmelt Erosion Of Hillslope And Watershed Scale At Huifa River Basin

As researched snowmelt erosion characteristics on the scale of slope and basin,select Jilin province Jixing small watershed slope land by in situ observation of snow properties,soil factors,runoff and sediment.Get the snow melting process by analyzing the variation of runoff and sediment,and snow water equivalent,soil thaw,and discuss snowmelt erosion characteristics and changing process on the slope scale snowmelt erosion.At the same time,select the Wu Dao Gou Hydrological Station toanalysis the hydrologica and erosion characteristics,and the characteristics and relations of snowmelt erosion process under different scales are studied through the comparative analysis of the two scales.The results of this study can provide scientific theoretical support for multi-scale snowmelt erosion mechanism and lay a foundation for the prediction and control of snowmelt erosion.The main conclusions of this study are as follows:(1)The temporal and spatial variation of snow cover on the slope is regular.RMSEof snow depth difference increased first and then decreased,the RMSE of snow density decreased,the change of liquid water content is complicated and unstable,generally presents with snow depth reduction in melting process,liquid water content increased,the density decreased gradually.The snow concentrated in test site in the southwest on the space,snow density along the north-south direction of the initial stage showed increasing decreasing,but the east-west direction is decreasing.The liquid water content in the north-south direction of the trend is not obvious,but the east-west direction decreased.The degree of influence of terrain factors on snow cover parameters is snow depth,liquid water content and snow density.The variation tendency of positive temperature and snow density and liquid water content is similar,which is the first increase,then decrease and then increase.(2)The snowmelt erosion process lasted 6 days.In the early period,snowmelt runoff accounted for 59.15%of total runoff;in the mid,snow melt stability,surface soil began to thaw,runoff reduced but erosion sediment increased,reached the maximum and total erosion amount of 41.74%;in the end of snowmelt runoff,the depth of soil thawing increases,sediment concentration reaches the maximum and is 8.00kg/m3.The characteristics of erosion are the main runoff production in the early snowmelt period,and the sediment yield in the middle and late stages is similar.Snowmelt runoff sediment lag relationship between runoff and sediment peak frequency by the complexity of the effect,when the frequency is consistent,runoff sediment is "8" lag relationship;when frequency differences,runoff sediment is complex on lag relationship.The relationship between the lag of snowmelt runoff sediment that snowmelt erosion of slope farmland is significantly affected by tillage area and catchment basin of the terrain changes.The source of runoff followed by melting snow and ice melt,furrows soil liquid water,and depression on both sides of slope erosion process is not synchronized.(3)The snowmelt runoff and the thawing depth of surface soil are the main factors that affect the snowmelt erosion in the process of snowmelt erosion.The snow is melting from the upper part of the slope to the slope with the change of the spatial heterogeneity of snow water equivalent.Snowmelt runoff from the upper part and middle part of slope in March 16th;the runoff from the upper,middle andlower part of slope in March 17th,in March 18th and 19th snowmelt runoff from middle andlower part of slope.The spatial heterogeneity of soil thawing depth on slope surface is more uniform.With the snow melt,the soil thaw depth change is complex and affected by snowmelt water migration,thaw depth position in the middle of the slope change is the most dramatic,the upper part next,then the lower part,and the sediment content was positively correlated.(4)The basin scale,the average annual flow and annual snowmelt runoff sediment concentration of runoff in the relatively more volatile,but the discrete degree of relative annual runoff is relatively concentrated,and the average is 14.18%of the runoff of snowmelt runoff,sediment concentration accounted for years of snowmelt sediment 18.68%.In the year of less water and less sand,the snowmelt runoff is 7.23%.In the year of normal water and sand,the snowmelt runoff is 22.67%.In the year of plenty water and sand,the proportion of snowmelt runoff is 23.08%.The hydrographic features of Meihekou Railway Station in 2015is equivalent to Wu Dao Gou Railway Station of 1971.(5)Compared the snowmelt erosion process of slope scale and watershed,the duration of snowmelt erosion process of slope is relatively longer than basin,and time of occurrence is similar.slope depth and snowmelt runoff and erosion modulus relatively smaller than Wu Dao Gou Hydrological Station.According to the lag relation of sediment content,the change of sediment source in snowmelt erosion is similar to that of river basin.