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| Erosive rainfall and rainfall erosivity in purple hilly area |
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Abstract 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 downslope cultivation land was 11.3mm. 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 5000 and 6500MJ/ (mm·hm2·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 ≥15mm 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.
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Received: 04 September 2012
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