重庆涪陵区降雨侵蚀力时间分布特征

Temporal distribution characteristics of rainfall erosivity in Fuling District, Chongqing

降雨侵蚀力反映降雨引起土壤侵蚀的潜在能力。利用涪陵区49a气象资料,对该地区降雨侵蚀力的年内分布和年际变化特征进行研究。结果表明:(1)涪陵区多年平均降雨侵蚀力为3571.07MJ·mm·hm-2·h-1·a-1,最大年为4039.07MJ·mm·hm-2·h-1·a-1,最小年为1193.76MJ·mm·hm-2·h-1·a-1,年际差异非常显著且明显大于降雨量和侵蚀性降雨量的年际变化。(2)该区降雨侵蚀力季节分布为单峰型,可分为高值期、中值期、低值期和无侵蚀期4个不同的时期;4～10月的降雨侵蚀力可占全年年降雨侵蚀力(R)值的94.06%,6月最大为670.94MJ·mm·hm-2·h-1·a-1,其次7月为664.26MJ·mm·hm-2·h-1·a-1,最小月为0;降雨侵蚀力的季节变化与降雨量和侵蚀性降雨总体变化趋势一致。(3)降雨侵蚀力时间变化与地表状况的配合可对实际土壤侵蚀的发生产生较大影响,在该地区5、6、7月降雨量在147.4mm和176.0mm范围内变化,4月、8、9、10月降雨量在101.9mm和115.7mm范围变化,年降雨量大于1090.6mm的年份,是当地水土流失极易发生的侵蚀敏感期。(4)该地区小流域综合治理中应充分重视每年5、6、7三个月内坡耕地覆盖情况,开发建设活动不仅应避开这3个月,同时在雨季开始前应注意裸露开挖面及弃土弃渣堆放地的水土保持措施布置和完善,以最大程度地减少人为水土流失。

Rainfall erosivity reflects potential ability of soil erosion and is the initial drive of potential water erosion. Characteristics of annual variation and interannual variation of rainfall erosivity were researched meteorological data of 49 years in Fuling District. The results indicate that： （1）The mean annual rainfall erosivity is 3571.07 MJ·mm·hm^-2·h^-1·a^-1 in Fuling District, maximum annual rainfall erosivity is 4039.07 MJ·mm·hm^-2·h^-1·a^-1 and minimum is 1193.76 MJ·mm·hm^-2·h^-1·a^-1, variation of interannual rainfall erosivity is significant difference, the variation range of the annual R is greater than the variation of the annual rainfall and its erosive rainfall. （2）The seasonal distribution of R value is a single peak, concentrating from April to October and taking 94.06% of total annual R value, which can be divided into four periods, including high value period、medium value period、low value period and no erosive period. The maximum of R value is June with 670.94 MJ·mm·hm^-2·h^-1·a^-1,next is July with 664.26 MJ·mm·hm^-2·h^-1·a^-1, the minimum value is 0. The main variety tendency of R value is coincident with rainfall amount and its erosive rainfall but has the biggest amplitude. （3）Temporal change of rainfall erosivity and the slope surface condition can have significant effects to the occurrence of soil erosion. The crisis periods of soil erosion in Fuling District includes these conditions, May, June and July, in which rainfall varying from 147.4 mm to 176.0 mm; April, August, September and October, in which rainfall varying from 101.9 mm to115.7 mm; the special year, in which rainfall beyond 1090.6 mm（.4）The coverage situation of cultivated slope land should be put great importance for comprehensive management of a small watershed during May, June and July every year in Fuling District. All kinds of development and construction projects should avoid these three months, rational implementation for soil and water conservation should be developed on the exposed slope and the ground subsidence before the rainy season, at the same time. These sound measures are especially useful for reducing soil erosion caused by artificial activities.