西柳沟流域基流变化特征分析

Trends in Base-flow Index of Xiliugou Stream in Loess Plateau,China

基流是枯水期河川径流的主要来源,可以反映流域地下水的变化过程,是研究流域水量平衡、地下水对气候变化与人类活动响应及预测的关键因子,对干旱内流河流域水文模拟和水资源开发利用至关重要.本文基于1981~1990年及2006~2015年西柳沟龙头拐水文站的实测径流资料,采用递归数字滤波法对西柳沟的流量过程进行了基流分割并计算其基流指数BFI值(Base-flow Index).在此基础上,分别以年、季度及月为单位,分析了基流量和BFI值的变化规律.研究表明,1981~1990年的平均基流量为7.8mm,BFI值为0.355.2006~2015年平均基流量为6.2mm,年平均BFI值为0.517,相比1981~1990年增加了47.2%.春、夏、秋、冬4个季节基流量整体均呈下降趋势且均通过了Mann-Kendall(M-K)突变检验,而BFI值整体呈现上升趋势,除夏季外,均超过了95%显著性水平检验,表明其上升趋势显著.除1月和6月外,其余各个月份的基流量均呈下降趋势,且除5月、8月和9月外,下降趋势明显;对BFI值而言,除12月份BFI值变化比较平缓,2月、9月和11月上升趋势不显著外,其余各个月份均呈显著的下降趋势.

A recursive digital filter method was used for baseflow separation based on the flow data from 1981 to 1990 and 2006 to 2015 recorded by Longtouguai hydrologic statation.Baseflow index(BFI),ratio of long-term baseflow to total stream flow was used to summarize the annual,seasonal and monthly baseflow characteristics in the study area.Results showed that average annual baseflow was 7.8 mm and BFI was 0.355 from 1981 to 1990.Average baseflow was 6.2 mm and BFI was 0.517 from 2006 to 2015.Significant annual decrease in baseflow and increase in BFI were noticed due to the decrease in total stream flow discharge in the past 10 years.Mann-Kendall tests showed that baseflow decrease significantly for the four seasons while BFI showed significant increasing tendency except summer.Baseflow in most of the months showed significant decreasing tendency,but it increased significantly in January and July.BFI,however,showed increasing tendency in all the months.In addition,seasonal and monthly BFI trend and variation analysis showed that,the changes of BFI from 1981 to 1990 were sharp compared to the year from 2006 and 2015.BFI were stable in winter,spring and the months of January,November and December while it fluctuated greatly in summer and months of June,July and August.