基于REOF的淮河流域降雨侵蚀力时空变化

Spatiotemporal variations of the rainfall erosivity in the Huaihe River Basin using REOF

淮河流域作为中国重要的粮食生产基地,研究其降雨侵蚀力的时空变化特征,对流域水土流失防治、土壤资源保护及农业可持续发展具有重要意义。该研究基于淮河流域内的40个气象站点1960—2018年的日降雨数据,采用Xie方法计算各站点降雨侵蚀力及降雨侵蚀力密度;使用旋转经验正交函数(Rotating Empirical Orthogonal Function,REOF)对淮河流域依据降雨侵蚀力的分布特性进行分区,采用线性倾向率、改进的Mann-Kendall检验和R/S分析法来分析流域内降雨侵蚀力的时空变化特征;并为不同分区提供合理的农业水土流失防治措施。结果表明:1)淮河流域多年年均降雨侵蚀力及降雨侵蚀力密度分别为4264 MJ·mm/(hm^(2)·h)和4.63 MJ/(hm^(2)·h),且降雨侵蚀力未来将呈增长趋势;整体上,流域内年降雨侵蚀力从东南部向西北部递减,年降雨侵蚀力密度从北部向南部递减。2)基于淮河流域40个站点的年降雨侵蚀力序列,使用REOF展开的10个空间特征向量的累计贡献率达74.34%,可着重突出空间分布特征。并依据这10个模态分布将淮河流域的降雨侵蚀力场划分为降雨特征不同的10个地理区。3)降雨侵蚀力较高的分区为第2、3、4、5和6区,主要集中于流域南部和东部;5—9月的降雨侵蚀力约占全年总和的80%~91%,降雨侵蚀力密度较高。3)在降雨侵蚀力较高的5—9月期间,流域内各区域的农业活动过程中需加强水土流失防治措施,尤其是第6区所在的区域。研究结果可为淮河流域内不同区域的耕地水土保持工作提供参考,并进一步保障流域内农业可持续发展。

Huaihe River Basin(HRB)is one of the most important food bases in China.The spatial-temporal variations of Rainfall Erosivity(RE)greatly dominate the local soil erosion prevention,soil resource protection,and agricultural sustainable development.In this study,the daily precipitation records were firstly collected from 40 meteorological stations in the HRB from 1960 to 2018.The RE and Rainfall Erosivity Density(RED)were then calculated using the Xie model.A Rotating Empirical Orthogonal Function(REOF)was also used to divide the HRB into different geospatial zones,according to the distribution characteristics of RE and the spatial-temporal variation of the RE.The RED was determined for each zone by linear,modified Mann-Kendall and R/S analysis.Finally,specific measures were provided for agricultural soil erosion prevention in each geospatial zone.The results show that the annual average RE and RED within the HRB were 4264 MJ·mm/(hm2·h)and 4.63 MJ/(hm2·h),respectively,indicating the ever-increasing RE in the future.Among these 40 meteorological stations,25 stations increased in the RE and 15 stations decreased in the RE,whereas,29 stations increased in the RED,and 11 stations decreased in the RED.As a whole,the annual RE decreased from the southeastern to the northwestern HRB,whereas,the annual RED decreased from the northern to the southern HRB.The REOF was carried out for the spatial feature vector with a cumulative contribution rate of 74.34%,according to the RE of 40 stations in the basin.After that,the HRB was divided into 10 geospatial zones.The higher RE occurred in the Nos.2,3,4,5,and 6 Zones,with an annual average value of 4576,5079,4840,4635,and 4898 MJ·mm/(hm2·h),respectively.The higher RED occurred in the Nos.1,5,6,and 9 Zones,with an annual average value of 4.73,4.98,4.73,and 4.85 MJ/(hm2·h),respectively.Zones Nos.5 and 6 were the regions with both the highest RE and RED.The RE decreased in Zones Nos.2,5,and 9,but increased in other zones.By contrast,the RED decreased in Zones Nos.2,5,6,and 9,but increased in other zones.The higher RE and RED were mainly concentrated during May to September,accounting for about 80%-91%of the annual value.Nevertheless,the RE and RED increased in most months in Zones Nos.2,3,and 4.The soil erosion prevention and control measures can be strengthened from May to September during the agricultural activities within the basin,especially in the No.6 Zone for the effective mitigation of local soil erosion.A correlation analysis between RE and sediment yields in the HRB revealed that the sediment yields were significantly correlated with the RE(P<0.001),whereas,the sediment yield increased with the increase of RE.Therefore,there was an increasing risk of soil erosion in the regions of Tongbai County,the cities of Xinyang,Lu’an,Yancheng,Yangzhou,Zhumadian,Kaifeng,Shangqiu,Pingdingshan,and Luohe,according to the spatial and temporal variations of RE and RED.These regions should pay more attention to soil and water loss monitoring,and suitable soil and water conservation measures in advance for erosion-prone areas.These findings can guide the soil and water conservation in the different areas of the HRB for the sustainable development of agriculture.