两类阈值法识别的东江流域水文干旱形成与演化过程差异

Differences in hydrological drought formation and evolution processes identified by two threshold methods in the Dongjiang River Basin

基于东江流域上、下游控制断面龙川站和博罗站1956—2010年逐月流量及流域内枫树坝、新丰江和白盆珠水库逐月入库和出库流量数据,采用水库调控流量还原法,结合动态阈值法和固定阈值法识别水文干旱,系统分析了两类阈值法识别的水文干旱形成与演化过程的差异及其对大型水库调控的响应规律。结果表明:两类阈值法针对的干旱本底概念不同,识别的水文干旱年内分布和干旱开始、峰值和终止月份差异显著;动态阈值法识别的水文干旱在年内各月均匀分布,固定阈值法识别的水文干旱集中分布在枯水季(10月至次年3月),干旱峰值多出现在11月至次年2月,干旱终止月份以汛前期3、4月为主,干旱开始、峰值和终止月份与研究区水文丰枯转换月份较吻合;两类阈值法均能较好地表征水文干旱的发展和恢复过程及其对大型水库调控的响应特征,即水库调控在缩短干旱历时、降低干旱烈度、延后水文干旱开始和峰值月份以及提前干旱终止月份等方面发挥重要作用。

Monthly flow data from the Longchuan and Boluo stations,representing upstream and downstream control sections of the Dongjiang River Basin,as well as monthly inflow and outflow data from the Fengshuba,Xinfengjiang,and Baipenzhu reservoirs within the basin for the period 1956-2010 were used.The reservoir regulation flow reconstruction method was employed,along with the variable drought threshold(VDT)and fixed drought threshold(FDT)methods,to identify hydrological drought events.Furthermore,the study analyzed the disparities in the formation,evolution process,and response to large reservoir regulation between hydrological droughts identified by the two threshold methods.The results reveal that,due to the different target drought background concepts for the VDT and FDT methods,the evolution processes,such as the start,peak intensity,and end months and the distribution within a year of hydrological droughts identified by the two methods are significantly different.Moreover,hydrological droughts identified by the VDT method are evenly distributed in each month of a year,while those identified by the FDT method are concentrated in dry season(from October to March of the following year)in the Dongjiang River Basin.The FDT method typically identifies the peak intensity of hydrological droughts,occurring from December to February of the next year,with the majority of droughts ending in pre-flood season,specifically in March and April.The utilization of the FDT method ensures that the start,peak intensity,and end months of hydrological droughts align well with the dryness/wetness characteristics of the Dongjiang River Basin.Both the VDT and FDT methods are able to characterize the development and recovery patterns of hydrological droughts.The changes in the evolution characteristics of hydrological droughts identified by the two methods and their responses to reservoir regulation are similar.In particular,both methods can reflect the effects of large reservoir regulation in shortening drought duration,reducing drought severity,delaying the start and peak intensity months of hydrological droughts,and advancing the end month of droughts.