紫色丘陵区侵蚀性降雨与降雨侵蚀力特征

降雨侵蚀力（R值）的空间分布反映了区域气候对土壤侵蚀的作用。利用四川盆地紫色丘陵区多年实测降雨资料，应用频率分析法，推求该地区侵蚀性降雨的一般雨量标准，揭示该地区侵蚀性降雨及其侵蚀特征，进而运用降雨侵蚀力日降雨量计算方法，分析紫色丘陵区降雨侵蚀力时空分布特征。结果表明：1）紫色丘陵区顺坡休闲农耕地的侵蚀性降雨的一般雨量标准为11．3mm；2）紫色丘陵区多年平均总降雨量中有60％以上属于侵蚀性降雨，侵蚀性降雨主要集中于5—9月，其中7、8月年均侵蚀性降雨量和土壤侵蚀量最大，空间分布上表现为丘陵区边缘地区大于中部地区；3）紫色丘陵区年均R值介于5000～6500MJ／（mm·hm^2·h）之间，由丘陵区周边向中心逐渐减小，研究区北部的巴中、达县、阆中3站的年均降雨侵蚀力形成高值区，中部的遂宁站形成低值中心，北部大于南部，西部大于东部；4）紫色丘陵区R值主要由≥15mm的降雨构成，占76．9％-82．1％，年内集中度较高，主要分布在汛期5—10月份，占年R值的89％以上；5）R值的年际变化较大，达到中等程度变异，不同地区的R值年际变化差异较大，但并未表现出明显的随时间变化的增减趋势。

Erosive rainfall and rainfall erosivity in purple hilly area

The spatial distribution of rainfall erosivity could reflect the role of the regional climate for soil erosion. Based on measured rainfall data for many years, frequency analysis method was employed to calculate the general rainfall standards of the erosive rainfall, and the erosive rainfall and its soil erosion characteristics were analyzed in the purple hilly area in Sichuan Basin. The rainfall erosivity was calculated using daily rainfall amounts and the spatial-temporal characteristics of rainfall erosivity were analyzed. The results showed that： 1 ） The general rainfall standard of erosive rainfall of the downstope cultivation land was 11.3 ram. 2） Over 60% of rainfall events were erosive rainfall. Erosive rainfall mainly fell on May to September. The erosive rainfall amount and soil erosion amount in the July and August was the largest. To the spatial distribution, the erosive rainfall of the edge region was greater than that of the central region. 3） The annual average rainfall erosivity value was between 5 000 and 6 500 M J/ （mm.hm^2.h）. It decreased from the edge to the central regions gradually, and was greater in the northern and western area than the southern and eastern areas. The annual average rainfall erosivity of the Bazhong station, Daxian station and Langzhong station in northern area formed the high value area, and the Suining station in central area formed the low value area. The rainfall erosivity was mainly composed by I〉 15 mm rainfall events, accounting for 76.9% - 82.1% of total rainfall events. It was mainly distributed in flood season （ between May to October） and accounted for more than 89% of annual rainfall erosivity. The interannual variability of rainfall erosivity was larger up to moderate variation, but did not occur to obvious increase or decrease trend over time.