| The Pisha sandstone area which is the main source of coarse si]tation in the lower reaches of the Yellow River at the junction of shanxi,shaanxi and Mongolia,and it is also the key area of complex erosion prone area and ecological environment construction and soil and water conservation in China.The main problem of ecological environment in this area is soil erosion.In recent years,evaluation of'ecological and hydrological effects of combined erosion control has become a research hotspot in this area.Based on the long-term observation data of runoff plots on slopes,the eco-hydrological characteristics of Erlaogou small watershed which is a typical small watershed in Pisha sandstone area of Zhungeer Banner,Ordos Plateau,are systematically analyzed by using the location observation method of runoff plots.The applicability of WEPP(Water Erosion Prediction Project)water erosion prediction model in arsenic sandstone area was evaluated,and the runoff and sediment on slope were simulated and predicted by WEPP model,and the effects of different erosion control measures on runoff and sediment reduction were compared and analyzed.The main conclusions are as follows:(1)The precipitation in Erlaogou watershed mainly concentrated in June-September,and reached the highest level in August.The number of erosive rainfall in July and August accounted for 41.5%of the total erosive rainfall.Soil erosion mainly occurred in this period.(2)The order of soil water content in different slope positions is:gully bottom in July>top of slope>bottom of slope>middle of slope>top of slope;gully bottom in October>bottom of slope>middle of slope>top of slope;and soil water content in shady slope>soil water content in sunny slope.The total soil water content in April-June is low,July-August is the highest,and September-October is low.Rainfall has a significant impact on the change of soil water content.(3)Based on the measured data of producing sand in runoff areas with Pisha sandstone from 2014 to 2016,article analyzed the coupling relationship between rainfall,runoff and sediment.The relationship between rainfall and cumulative runoff keep a linear relation,and the relationship between cumulative runoff and cumulative sediment yield is power exponential.(4)Sensitivity analysis of soil parameters in WEPP model shows that effective conductivity,critical shear force and rill soil erodibility are sensitive parameters;effective hydraulic conductivity after calibration is 4.73 mm/h,critical shear force is 1 Pa,and rill soil erodibility parameter is 0.01 m/s.The validation results of model validity ME and determinant coefficient R2 show runoff and erosion are 0.7223 and 0.6160,0.7025 and 0.6167 respectively,while the R2 and ME of WEPP model for runoff and erosion are 0.7116 and 0.6741,0.8447 and 0.6903 respectively,based on the runoff measured data and simulation values from 2014 to 2016.The comparison of ME values shows that WEPP model has better applicability on the slope of Pisha sandstone area,the simulation effect of erosion amount is better than that of runoff,and the simulation effect of measure plot is better than that of no measure plot.(5)Based on field investigations,six scenarios of plant erosion control measures were constructed and simulated by WEPP model.The results showed that scenario a(herbs with low coverage on sunny slope),scenario B(shrubs with low coverage on sunny slope),scenario C(shrubs with medium coverage on sunny slope),scenario D D(shrubs on shady slope),scenario e(shrubs with high coverage on shady slope),scenario f(shady slope).The effect of reducing runoff and sediment was 13.04%-91.28%and 44.46%-99.98%respectively.Generally speaking,the effect of reducing runoff and sediment in different scenarios:scenario d>scenario E>scenario C>scenario f>scenario b>scenario a. |
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