山东省药乡小流域侵蚀性降雨分布特征

为探究山东省药乡小流域侵蚀性降雨分布特征,本研究选择裸地坡面径流小区为研究对象,利用小区观测法得到的降雨、径流以及泥沙等资料,通过频率分析法拟定研究区侵蚀性降雨标准,并运用数理统计方法从时间、降雨强度、降雨侵蚀力角度分析侵蚀性降雨分布特征.结果表明:1)该研究区侵蚀性降雨标准为降雨量17.3 mm;2)7月份侵蚀性降雨场次、降雨量、径流量和产沙量占侵蚀性降雨比例为42.31％、45.71％、85.78％和97.97％,其他月份侵蚀性降雨分布较少;3)大雨、暴雨以上侵蚀性降雨,高降雨强度型降雨场次分别占相应雨量等级比例为60％和100％,其产沙量所占比例分别为75.07％、100％;4)降雨侵蚀力＞1000MJ·mm/(h·hm2)侵蚀性降雨产沙量占侵蚀性降雨比例为95.26％,其径流深是≤1 000 MJ·mm/(h·hm2)侵蚀性降雨3倍以上.以上研究表明,研究区侵蚀性降雨标准为17.3 mm,其主要分布在中雨以上雨量等级,造成严重土壤侵蚀的侵蚀性降雨多为高降雨强度型降雨或降雨侵蚀力＞1 000 MJ·mm/(h.hm2)的降雨,且其多分布于7月份.本文结果有助于研究区小流域侵蚀性降雨规律分析以及土壤侵蚀规律研究.

Distribution characteristics of erosive rainfall in Yaoxiang Small Watershed of Shandong Province

Background] In order to study the effect of erosive rainfall on runoff and sediment yield in the mountainous area of North China,we first need to study the distribution characteristics of erosive rainfall.In this paper,the research object is runoff plot of bare land that is typical in Yaoxiang Small Watershed of Shandong Province.Methods] The characteristics of erosive rainfall were analyzed by mathematical statistics,based on the data of rainfall observed by tipping bucket rain gauge,runoff calculated by plot runoff and sediment yield measured by oven-drying method in the period of 2013-2015.In addition,rainfall erosive force was calculated by I30max.In this paper,erosive rainfall standard was proposed by the method of Wang Wanzhong.Here is the method:1) calculating the total erosion amount of erosive rainfall:the rainfalls of the selected samples are sorted by descending order,and the corresponding amount of soil erosion is accumulated,thus the total erosion amount in n erosive rainfalls is obtained;2) classifying the amounts of rainfalls as several levels,and then calculating the proportion of the accumulated erosion amount over a given rainfall amount to the total erosion amount;3) the standard of erosive rainfall is the amount of rainfall corresponding to the proportion of the accumulated soil erosion amount after the allowable soil erosion is deleted,to total erosion amount.Results] 1) The reference value of standard erosive rainfall in the study area was 17.3 mm.2) In July,times of erosive rainfall,precipitation,runoff volume,and sediment yield accounted for 42.31％,45.71％,85.78％,and 97.97％ in all erosive rainfalls,respectively,and erosive rainfall occurred little in other months.3) In the class of heavy rain,the rainfall times of high rainfall intensity type accounted for 60％ and sediment yield accounted for 75.0％.While in the class of above rainstorm,the rainfall times of high rainfall intensity type accounted for 100％ and sediment yield accounted for 100％.4) In the class of rainfall erosive force ＞ 1 000 MJ·mm/(h· hm2),sediment yield accounted for 95.26％ in all erosive rainfalls,and the runoff depth was over 3 times of the erosive rainfall ＜ 1 000 MJ· mm/(h·hm2).Conclusions] Therefore,the standard of erosive rainfall in the study area is 17.3 mm,which is mainly distributed in the moderate and above rainfall grades.The rainfall causing serious soil erosion is high rainfall intensity type or the erosive force of the rainfall is ＞ 1 000 MJ·mm/(h·hm2),and it mainly distributes in July.This research is conducive to study the erosive rainfall in the small watershed,and provides a reference for understanding the erosive rainfall in the northern rocky mountains.