白洋淀流域径流过程对极端气象干旱的响应分析

ANALYSIS ON STREAMFLOW PROCESSES RESPONSE TO EXTREME METEOROLOGICAL DROUGHT IN THE BAIYANGDIAN BASIN,CHINA

以白洋淀流域为研究对象,选取唐河、沙河、白沟引河3条支流上游4个水文站1959-2016年的日径流数据,采用改进退水常数后的数字滤波法中的Chapman-Maxwell法对4个子流域的日径流进行基流分割,利用水文气象要素异常值法划分干旱时期,分析水文干旱(径流干旱与基流干旱)对极端气象干旱过程的响应规律。结果表明:1)白洋淀年降水量呈减少趋势,线性倾向率为1.81 mm/a^2。在1979年发生减少突变,突变后降水量减少8%;并检测到白洋淀流域发生极端气象干旱,持续时间从1996年8月至2011年5月;2)4个子流域的水文干旱较气象干旱具有明显的时间滞后,且水文干旱持续时间比气象干旱更长,烈度、强度更大,表明长期干旱期间降雨-径流关系的不稳定性;3)4个子流域水文恢复时间较气象恢复平均滞后55个月,且基流恢复滞后于径流恢复。研究结果可加深径流与基流对气候变化的响应的理解,为核算河道生态需水以及维持河道生态系统健康提供一定理论依据和实践参照。

Using the digital filtering method with the improved regression constant-Chapman-Maxwell,the baseflow was separated from daily streamflow in the four hydrological stations in the Baiyangdian Basin.Monthly anomalies of three specific hydrometeorological variables(precipitation,streamflow,and baseflow)were used to analyze the hydrological drought response(runoff drought and baseflow drought)to extreme meteorological drought process.The results showed that:1)annual precipitation in the Baiyangdian Basin presented decreasing trends with a rate of 1.81 mm/a,and a downward abrupt change was found around 1979,which resulted in about 8%of precipitation decrease.Consistent with the decreasing trend in precipitation,an extreme meteorological drought was also detected,and ranged from August 1996 to May 2011;2)hydrological drought,resulting from meteorological drought,exhibited a time lag and had a longer drought duration and greater drought intensity,suggesting a nonstationarity in the rainfall-runoff relationship during a prolonged drought;3)hydrological recovery lagged behind meteorological recovery by about an average of 55 months,and baseflow recovery lagged the runoff recovery.All of these results can help to understand the hydrological response to climate change better,and provide certain theoretical and practical references for calculating river ecological water demand and maintaining river ecosystem health.