| The Loess Plateau is located in the hinterland of China's mainland.It is the highest land with the widest loess distribution area,the deepest thickness,and the most complete stratum distribution in the world.It covers an area of ??about642,000 km2 and is part of the middle reaches of the Yellow River.In this study,field simulated rainfall experiments were used to reveal the relationship between slope and rainfall intensity on the erosion and runoff and sediment yield of the Malan loess slope.In addition,the SWAT model was applied to the Nanxiaohegou watershed in the arid and semi-arid area of ??the middle and upper reaches of the Yellow River.Continuous monthly runoff simulation was carried out,and the water source division and calculation process of SWAT were analyzed.From the perspective of runoff mechanism,SWAT was discussed and summarized in the arid and semi-arid The applicability and limitations of the region have laid the foundation for SWAT application research and model improvement in arid and semi-arid areas.According to the on-site detection data of the sponge city construction platform in Qingyang City and the meteorological data provided by the China Meteorological Data website,the actual evaporation is calculated by the Penman-Wilson formula,and the evaporation is fitted by the VADOSE / W finite element software.The main results are as follows:Study on soil erosion process of loess slopes under different slopes.Under the same slope and uniform rainfall intensity,the runoff rate of the loess slope with the change of rainfall duration is gradually increased and finally stabilized,while the change of the sediment yield with the rainfall duration is first increased to a certain peak and then gradually decreased to a certain value A stable value,the greater the slope,the more obvious the phenomenon of sand production rate;under the same rain intensity,the sand production rate increases with the increase of slope,and the impact of slope on the sand production rate also shows due to the difference in rain intensity A big difference.It can be seen from the change process of the sediment yield curve that the erosion of the loess slopes has a critical slope between 20 ° and 25 ° slopes under the rain intensity of 45 mm / h and 60 mm / h.Study on soil erosion process of loess slopes under different rainfall intensities.The runoff time on the loess slope is shortened with the increase of slope and rain intensity.The runoff rate on the loess slope increases slowly with the increase of slope,and increases rapidly with the increase of rain intensity.The influence of rain intensity on the runoff rate on the loess slope has always been dominant,and the influence of slope on the runoff rate is very high.To a large extent,it was covered by Yuqiang.Under the same rainfall intensity,the rate of erosion and sediment yield on the loess slope increases with the increase of slope.Under the rainfall intensity of 75 mm / h,there is a critical slope around 20 ° under the intensity of the erosion and sediment yield on the loess slope.The rainfall intensity increases.Under the condition that the planting soil lasts for 24 hours under changing rain conditions,the sand production rate of slopes on three slopes increases with the increase of rainfall intensity,and the sand production rate of slopes is 30 °> 15 °> 10 °.The runoff rate and flow rate of the three slopes are 15 °> 30 °> 5 °.Under the condition of changing soil with a short duration of 3h,the sand yield rate of the slopes of the three slopes increases with the increase of rainfall intensity,and the sand yield rate of the three slopes is 30 °> 15 °> 5 °.The rainfall in the rain shed is not affected by the slope.The runoff rate and flow rate of the three slopes are15 °> 30 °> 5 °.In the construction of sponge cities,the urban rainfall interception capacity should be improved as much as possible.Different land use types have large differences in precipitation interception capacity.From large to small,they are forest land,grassland,cultivated land,and construction land.Can increase the coverage of forest and grassland.In the construction of sponge city,the rain infiltration capacity of the city should be increased as much as possible.The hard paving area such as roofing,paving and roads in the planning area before reconstruction is large,and the green area is small,which is not conducive to penetration.Sponge city construction should improve the ability of rain and water seepage,such as permeable pavement.The water cycle in the soil mainly occurs in shallow layers.The current observation results show that the depth of influence of evaporation can reach 0.6m,which preliminarily shows that the water infiltration within 0.6m from rainfall infiltration is upward if there is no subsequent rainfall replenishment Evaporation.Combining VADOSE / W finite element software and actual meteorological conditions on the spot,the evaporation of the loess surface layer of the observation site is calculated,and the simulated value and the actual calculated value have a highdegree of fit. |
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