鄱阳湖流域降雨侵蚀力变化及其对入湖悬移质输沙量的影响

Change of the Rainfall Erosivity in Poyang Lake Basin and Its Influence on Suspended Sediment Load into the Lake

鄱阳湖是中国最大的淡水湖,揭示流域降雨侵蚀力时空演变及其对入湖泥沙的影响对科学指导流域生态保护与修复、促进流域生态文明高质量发展具有重要意义。基于鄱阳湖流域63个气象站1961—2017年逐日降雨量和鄱阳湖“五河”入湖悬移质输沙量(以下简称“输沙量”)年数据,采用Mann—Kendall非参数检验、双累积曲线、线性回归等方法,分析了流域降雨侵蚀力和入湖输沙量动态过程,定量评估了降雨侵蚀力变化和人类活动对入湖输沙量的影响。结果表明:鄱阳湖流域平均降雨侵蚀力为10034.1(MJ·mm)/(hm^(2)·h),介于6738.8~12734.8(MJ·mm)/(hm^(2)·h),呈西南地区低、东北地区高的空间分布格局;降雨侵蚀力年际间呈不显著的上升趋势(P>0.05),在21世纪10年代最大,20世纪60年代最小。鄱阳湖入湖年均总输沙量1183.3×10^(4) t,呈极显著下降趋势(P<0.01),在20世纪70年代最大,21世纪00年代最小。入湖总输沙量和赣江、信江及修水输沙量分别在1992年、1999年后发生趋势性减少(P<0.01)。以输沙量突变前的时段为基准期,突变年份后人类活动和降雨侵蚀力变化对入湖总输沙量变化的影响程度分别为-138.1%和38.1%;对赣江入湖输沙量变化的影响程度分别为-125.8%和25.8%;对信江入湖输沙量变化的影响程度分别为-121.3%和21.3%;对修水入湖输沙量变化的影响程度分别为-141.4%和41.4%。近60年降雨侵蚀力变化表现为增加入湖输沙量,而人类活动(水库建设、水土保持和采砂活动)是鄱阳湖入湖输沙量减少的主要原因。

As the largest freshwater lake in China,revealing the spatial-temporal evolution of the rainfall erosivity and its impacts on sediment into the Poyang Lake is of great significance to scientifically guide the ecological protection and the development of the high-quality development of the ecological civilization in the basin.In this paper,change of the rainfall erosivity in Poyang Lake basin(PYLB)and its effects on suspended sediment load(SSL)into the lake were investigated based on the daily rainfall data of the 63 weather stations within the PLYB and the annual SSL into Poyang lake from its five tributaries from 1961 to 2017,using the non-parameter Mann-Kendall test,Double mass curve and Linear regression method.The results showed that annual average rainfall erosivity of PYLB was 10034.1(MJ·mm)/(hm^(2)·h),ranging from 6738.8 to 12734.8(MJ·mm)/(hm^(2)·h).The spatial pattern of the rainfall erosivity showed that low rainfall erosivity mainly distribute in the southwest region and high rainfall erosivity mainly distribute in the northeast region.The rainfall erosivity showed an insignificant increasing trend(P>0.05)during 1961—2017,of which the greatest value was in the 2010s and the smallest in the 1960s.In the same period,the annual average total SSL into the lake was 1183.3×10^(4) t,showing a significant decreasing trend(P<0.01).The greatest value of the SSL was in the 1970s and the smallest was in the 2000s.The change points of the total SSL into the lake and the SSL of the Ganjiang river,Xinjiang River and Shuishui River were in 1992,and 1999,respectively(P<0.01).Taken the period before the change points of the SSL as the baseline period,the contribution rate of human activity and rainfall erosivity on the total changes of SSL into the lake was-138.1%and 38.1%,respectively during the period after the change point.The contribution rate of human activity and rainfall erosivity on the SSL changes of the Ganjiang river was-125.8%and 25.8%,respectively.The contribution rate of human activity and rainfall erosivity on the SSL changes of the Xinjiang river was-121.3%and 21.3%,respectively.The contribution rate of human activity and rainfall erosivity on the SSL changes of the Xiushui river was-141.4%and 41.4%,respectively.The change of rainfall erosivity was advantageous to increase the SSL into the lake,and human activities,e.g.reservoir construction,soil and water conservation and sand mining were the main driving forces for the decrease of the SSL into the Poyang Lake in the recent 60 years.