以树木年轮宽度重建渭河上游过去377 a来4-6月平均流量

April to June average streamflow reconstruction for Weihe Riverupper reaches during the past 377 years by means of tree rings

目的 探讨渭河流域上游过去377 a的径流流量的变化历史,提供流域百年尺度水文要素波动的变率、强度、周期及其长期演变特征等水资源评估所需的关键信息。方法 使用相关系数法、线性回归法和功率谱法判定树轮年表与平均流量的响应关系、径流变化模型及水文要素周期信号。结果 基于贵清山油松年表与渭河南河川站月流量的相关结果,重建了1630-2006年当年4-6月的平均流量变化,建模期1945-1979年时段的方差解释量为34.9%。树轮流量序列确定了51个极端高流量年和54个低流量年,分别为过去377 a的13.53%和14.32%。其中连续3 a以上的极端高值年份出现在1647-1649年、1699-1701年、1843-1845年、1905-1907年和1909-1911年;极端低流量年份出现在1722-1727年、1747-1749年和1763-1765年。对基于11年滑动平均确定的流量偏高偏低时段水文要素进行量化,显著的低流量年份与区域大尺度干旱事件有较好的印证关系。重建流量具有50.400 a和2.290 a的周期信号。结论 树轮重建的377 a渭河天水段季节径流变化具有变率高幅度大的特点,流域水文气候变化与大尺度气候驱动,如太平洋年代际涛动、厄尔尼诺-南方涛动存在紧密关联。

Purposes—To investigate the historical changes in runoff flow in the upper reaches of the Weihe River basin over the past 377 years,and provide key information needed for water resource assessment,such as the variability,intensity and periodicity of hydrological elements on a centennial scale,as well as their long-term evolutionary characteristics.Methods—Correlation analyses,linear regression equation and power spectrum method were utilized to determine the response relationships between tree rings and streamflow,model construction and period signals.Results—The variations of April to June average streamflow during 1630-2006 were reconstructed.The variance interpretation of 34.9%existed in the calibration period from 1945 to 1979.The reconstructed tree ring streamflow sequence identified 51 extreme high-flow years and 54 low-flow years,accounting for 13.53%and 14.32%over the total 377 years.Extreme high-flow epochs with more than three consecutive years appeared in 1647-1649,1699-1701,1843-1845,1905-1907 and 1909-1911,while extreme low-flow years occurred in 1722-1727,1747-1749 and 1763-1765.The values of high and low streamflow spans based on the 11-year moving average were quantified,and the significant low-flow years had a good relationship with the regional large-scale drought events.The reconstruction had a periodic signal of 50.400 a and 2.290 a.Conclusions—The variations of tree ring seasonal streamflow of the Tianshui section for the middle-upper reaches of the Weihe River during the past 377 years were characterized by high variability and large amplitude,and the hydrological climate changes in the basin were closely related to large-scale climate drives such as the Pacific Decadal Oscillation and El Ni o-Southern Oscillation.