Simulation Study On The Effects Of Different Soil And Water Conservation Measure Combinations On Soil Erosion In The Loess Hilly Region

Loess Plateau is regarded as one of the most heavily eroded and the most fragile area across the world.This study is mainly based on the effect of the human factors on Loess hilly region and cause irreversible damage,using model methods,research re-establishment measures and biological measures.The results of this study aim to provide theoretical basis and scientific and technological support for soil and water conservation measures.The results show that:?1?Select the Caragana as the research object,the sensitivity analysis of WEPP model show that runoff is sensitive to effective hydraulic conductivity,soil erosion is sensitive to effective hydraulic conductivity and interill erodibility.The calibrated values of effective hydraulic conductivity and interill erodibility were 12.2 mm/h,6.995×10⁶ kg?s?m^-4,respectively.The rest of the parameters used the model default values.In this study,the WEPP model was used to simulate runoff and sediment yield with increasing gradients,show that runoff remained stable and sediment yield increased slowly with increasing gradients before reaching a critical slope gradient?20°?.?2?The important way to control soil erosion is re-establishment measures,The major purpose was to analyze the characteristics of soil erosion on different level terraces.Compared with slope,when the field widths increased,the regulation rates of runoff increased from 6.5%to 61.2%and from 10.1%to 69.7%,under medium?1.0 mm/min?and strong?1.5 mm/min?rainfall intensity,respectively.Level terraces with two stages and field width greater than 1.5m captured less sediment than the slopes.The regulation rates of sediment yield of the two-and three-stage level terraces increased from 1.1%to 68.8%and from 1.4%to 82.3%,respectively.According to maximize the efficiency of sediment reduction the table width of level benches should be appropriately designed.When suffering from small?0.5 mm/min?,medium?1.0 mm/min?,and strong?1.5 mm/min?rainfall,three-stage level terraces with field widths of1.0 m?1.5 m two-stage level terrace?,1.5 m,and 2.0 m can play prominent roles in water erosion control,the maximum sediment reductions of unit field were 0.13 kg/m³ and 0.12 kg/m³,0.17kg/m³,0.30 kg/m³,respectively.?3?Vegetation is also important to reduce soil erosion.In this study,the regular soil loss of slope vegetation and the effect vegetation canopy cover,slope position on soil erosion were researched.The results showed that:the regular of soil loss was significantly affected by rainfall intensity.At the early rain,runoff and sediment yield increased obviously,over time,runoff and sediment yield had different trends,0.5 mm/min of stable runoff earlier than 1.0 mm/min,and1.0 mm/min of runoff value greater than the 0.5 mm/min.At 0.5 mm/min,and 1.0 mm/min,the stable time of sediment yield were begin with 30 min,10—30 min.But when 1.0 mm/min,after30 min,the sediment yield had increased obviously,it was illustrated that vegetation could reduce soil erosion when rainfall early.By used WEPP model,compared soil loss of Caragana and Stipa bungeana at different slope position.Result showed that:the soil loss change not obviously of vegetation cover.The interception rate of sediment Stipa bungeana slope greater than the Caragana,increased from57%to 96,36%to 90%,respectively.At medium?1.0 mm/min?and high rainfall?1.5 mm/min?intensities,when the vegetation canopy cover was less than 20%or above 80%,the sediment yield of Stipa bungeana slope was greater than that of the Caragana slope.However,when the vegetation canopy cover was between 40%to 60%,the sediment yield of Stipa bungeana slope was less than the Caragana slope.Meanwhile,double factor variance analysis showed that slope position and vegetation cover exhibited inverse relationship.Both had significant effect on sediment yielding on slopes?P<0.001?.Specifically,the interaction between slope position and Stipa bungeana vegetation cover showed the significant effect on sediment yield?P<0.01?,but when the vegetation was changed into Caragana,the interaction between slope position and vegetation cover became insignificant on sediment yield.Moreover,when Stipa bungeana was allocated at the down slope,or when the allocation of Caragana and Stipa bungeana was1:2,both captured the least sediment yield.