Characteristics And Regulation Of Runoff And Sediment Production On Slope In Water-wind Erosion Crisscross Region

In the loess area,the benefits of reducing the loss of soil and water from Grain for Green are significant.At the same time,soil desiccation has occurred,and there has been a reduction in surface runoff and a decrease in vertical infiltration,which in turn has affected negative results such as groundwater and base flow recharge.Therefore,it is particularly important to explore the law of rainfall-infiltration-runoff and sediment production under the new situation and the appropriate control measures were used to improve this situation.This paper analyzed the located monitoring database of slope runoff in the Liudaogou watershed of water-wind erosion crisscross region on the Loess Plateau,and explored the characteristics of the runoff and sediment production of coarse texture soil under natural rainfall conditions.In addition,artificial rainfall simulations were conducted on the alfalfa plots to consider the different ASWC and slopes in the early stage to explore the effects of high water-consuming plants on the rainfall-infiltration-runoff process under different water levels and slopes.On the basis of this research,planting a plant with low water consumption,Leymus chinensis,artificially simulates rainfall on different canopy heights of Leymus chinensis to explore the benefits of soil and water conservation,the results showed that:?1?Rainfall in the Liudaogou small watershed during the rainy season from2014 to 2017 accounted for more than 50%of annual rainfall in July-September,and erosive rainfall mainly occured during the rainy season.The date which generated the annual maximum runoff and erosion for farmland and bare land were basically the same as the maximum rainfall dates for that year.The runoff of farmland was significantly correlated with rainfall?P<0.05?,and the runoff of bare land was significantly correlated with rainfall?P<0.01?.There was a highly significant positive correlation between runoff and erosion in farmland and bare land and I₁₅,I₃₀,and I₆₀?P<0.01?,of which farmland and bare land runoff had the best correlation with I₃₀,I₁₅ and erosion amount of farmland had the best fitting relationship,and I₆₀had the best fitting relationship with soil erosion of bare land.The standard SCS-CN model could be directly applied to the Liudaogou small watershed on the Loess Plateau.The predicted value was significantly related to the measured value,but the runoff was lower simulated by the model under small rainfall events.?2?The ammonium in bare land and farm land runoff did not change greatly over time,and the nitrate changed greatly over time.Both nitrate and ammonium fluctuate substantially between 0-1.0 mg/L.The fluctuation range of available phosphorus in bare land was less than that of farmland as a whole,and the available phosphorus content in bare land as a whole was lower than the available phosphorus content in farmland.The loss of total nitrogen and total phosphorus of the loss of sediments from farmland and bare land had not changed much with time.The amount of nutrient losses in runoff varied greatly from year to year.The loss of nitrate was 43.0-250.7 g/ha,and the loss of ammonium was 39.7-416.6 g/ha.Losses of total phosphorus in farmland and bare land were higher than total nitrogen losses.?3?Under the three kinds?5°,15°,25°?of slope conditions,the runoff processes of bare land and alfalfa land have increased at the beginning of the experiments and then stabilized,the difference in runoff between different slopes was not significant,but the amount of sediment loss increased significantly with the increasing slopes,which were increased firstly and then tended to be stable.The fluctuation of the rainfall process in bare land was greater than that of alfalfa land.The effects of ASWC on the runoff and average infiltration rate of the two treatments reached significant levels,the effect of slope on sediment loss and sedimentation rate was significant.Both runoff and sediment loss were significantly lower than bare land at the same slope and ASWC.The runoff of each ASWC of the alfalfa land was lower than that of the bare land runoff with the same ASWC,which was reduced by 27.4%⁴2.6%?5°?,25.2%⁴2.9%?15°?,and 15.5%³0.4%,respectively?25°?.?4?Under 60 mm/h field simulated rain conditions,the runoff from the grassland of 15,30,and 60 cm canopy height was 11.2,5.6 and 4.2 mm,respectively.The runoff decreased with the increase of the height of Leymus chinensis,and all of them did not produce sediments.It is indicated that Leymus chinensis has good soil conservation function,and the increased runoff after control the height of the canopy may increase the other components of the water cycle,which is a good control measure for the slope water circulation in the loess area.