渭河流域降雨侵蚀力时空分布特征

[目的]揭示渭河流域降雨侵蚀力的时空变化特征,为区域水土保持规划提供依据。[方法]根据渭河流域及其周边范围30个气象站点1957—2014年逐日降雨资料,采用章文波日降雨量侵蚀模型计算各站点的降雨侵蚀力,分析其空间分布规律和年内分布特征。[结果]渭河流域多年平均降雨侵蚀力值分布范围为806.25~3 510.81 MJ·mm/(hm2·h),平均值1 798.97 MJ·mm/(hm2·h),与多年平均侵蚀性降雨的空间分布基本一致,总体呈现西北低东南高的趋势。渭河流域降雨侵蚀力年内变化呈单峰型,主要集中在7—9月,占全年降雨侵蚀力的63.91%。北部黄土高原地区和关中平原发生水土流失的时期集中在7—9月,而秦岭北麓地区5—10月均有可能发生较大的水土流域,侵蚀风险由西北向东南递增。流域降雨侵蚀力年际波动较大,年际变率Cv值在34%~56%之间,整体而言,流域西北部地区的降雨侵蚀力年际变化幅度大于东南部地区。除洛川、长武、环县、平凉4个站点降雨侵蚀力在研究时段内有所增大外,其余地区降雨侵蚀侵蚀力呈不同速率的减小趋势。[结论]渭河流域降雨侵蚀力时空分布差异显著,尽管流域降雨侵蚀力呈减弱趋势,由于流域地处黄土高原,水土保持与水源涵养工作仍需高度重视。

Spatial and Temporal Variations of Rainfall Erosivity inWeihe River Basin

[Objective] To study the temporal variability and spatial distribution of rainfall erosivity in Weihe River basin in order to provide a reference for soil and water conservation.[Methods] Based on the daily rainfall data from 1957 to 2014 in 30 meteorological stations in Weihe River basin, the rainfall erosivity model proposed by Zhang Wenbo was used to calculate the rainfall erosivity, and its temporal variability and spatial distribution were analyzed.[Results] The range of annual rainfall erosivity in Weihe River basin was 806~4 017.81 MJ·mm/(hm²·h) with an average value of 1 798.97 MJ·mm/(hm²·h). The average annual erosivity decreased from the northwest to the southeast in general. There was strong correlation between the average annual erosive rainfall and the rainfall erosivity, and they had similar spatial distribution. The rainfall erosivity from July to September account for 63.91% of the total annual rainfall erosivity, showing an unimodal annual variation. Soil water loss was found mainly concentrated from July to September in the northern of the Loess Plateau and Guanzhong region. Great soil erosion might potentially occurred from May to October in Qinling Mountains. The risk of erosion increased from the northwest to the southeast; The inter-annual change of rainfall erosivity in Weihe River basin was obvious with the C_v value ranging from 34% to 56%. C_v value of rainfall erosivity in northwest region was larger than that in southeast region in general. The annual rainfall erosivity of most areas in Weihe River basin showed upward trend with different rates, except for the decline trends of Luochuan, Changwu,Huanxian and Pingliang stations.[Conclusion] There were significant differences of rainfall erosivity in spatial and temporal distribution. Although rainfall erosivity in Weihe River basin showed a decreasing trend, soil and water conservation work is still very important.