| The process of rainfall and runoff and sediment yield were important parts of soil water erosion on slope land. The rainfall and soil physicochemical properties directly affected the runoff and sediment process and the establishment of soil erosion prediction model. The project area was located on YiMeng- Mountain Tai area which was the key harnessing region of soil and water loss in our country. Soil erosion was relatively serious in this region and had a serious impediment to the local agricultural production and economic development. With the combining methods of field site monitoring, laboratory test and data analysis method, this paper studied the rainfall, runoff and sediment yield in the experiment area in nearly 4 years,and analyzed the distribution of rainfall characteristic, the rainfall process of the typical rainfall and the process of runoff and sediment. The relationships between different types of rainfall intensity and runoff and sediment yield, soil physical property index and runoff and sediment yield and its reasons were also studied. The research results were as follows:(1) Monthly rainfall distribution was uneven, the rainfall and average rainfall intensity in July and August were significantly higher than other months. The frequency of heavy rain,rainstorm and heavy rainstorm was less, but the amount of them was larger which accounted for 83.6% of the total rainfall. The critical rainfall of erosive rainfall was 14 mm and the critical rainfall intensity was 0.942 mm/h in the study area. The seasonal distribution of rainfall erosive agent was not uniform, and rainfall erosive agent in summer was the biggest in the whole observation period which was 14159.34 MJ?mm/(ha?h).It accounted for 73.01%of the total rainfall erosive agent. The average rainfall erosive agent in July and August was the highest in the whole observation period.(2)When rainstorm occurred, the runoff rate would change greatly with the rain intensity increasing or decreasing, the sediment yield rate trends were consistent with the change of rain intensity in the 10 ° longitudinal ridging farmland plot. The runoff rate lagged behind rainfall, and runoff rate had a very good correspondence with rain intensity in 15 ° terraced plot. The slope runoff responded quickly to the rain, and the fluctuation of runoff rate and sediment yield rate were relatively consistent in 15 ° bare land plot, but the magnitude of the change was much less than the variation of runoff. The runoff rate showed a corresponding trend with rain intensity, the magnitude of the change was much bigger than that of runoff in25 ° grassland plot.Rain intensity and run off rate were linearly related. The 10 ° longitudinal ridging farmland and 15 ° bare land plot were highly correlated. 15 ° terrace and 25 ° grassland plot were less correlated.There was a positive correlation between sediment yield rate and runoff rate. Extremely significant correlation exited among 10 ° longitudinal ridging farmland plot, 15 ° terraced plot and 15 ° bare land plot. The correlation between the runoff rate and the sediment yield showed a low degree in the 25 ° grassland plot.(3) When the moderate rain and light rain occurred, the runoff rate and sediment yield rate on slope land were relatively small, and the runoff and sediment often interrupted during the process of rainfall. There was a good linear correlation between rainfall and runoff in every runoff plot. When the content of soil water was close to saturation, the runoff and sediment yield rate of the slope showed a significant linear correlation.(4) In 4 runoff plots with different measures, 15 ° terrace planting sweet potatoes could better reduce the flow of rainfall and runoff, and thus reduce runoff and sediment yield;25 °linear slope grassland could reduce sediment yield, but it could not significantly affect the runoff yield; 10 ° longitudinal ridging farmland planting peanut and bare land could not significantly reduces the runoff and sediment yield?... |
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