时段长取值变化下的径流年内分配特征研究

Annual distribution of streamflow with different identifications of time intervals

利用东江流域控制站博罗站1954—2009年日平均流量资料,选取集中度、集中期、不均匀系数和极值比4项指标,研究了河川径流年内分配特征,在不同时段长取值下的变化规律及年际变化特征。结果表明:东江径流年内分配的集中程度及时间,基本上不会受到时段长取值大小变化的影响。集中度多年均值为0.35,集中期多年均值出现在7月上旬。径流年内分配不均匀性和变化幅度,随时段长取值缩短而增大,并与时段长的对数线性负相关。不均匀系数多年均值由基于月平均流量分配的0.62上升到基于1 d平均流量分配的0.89,极值比多年均值由基于月平均流量分配的8.63上升到基于1 d平均流量分配的39.55。径流年内分配特征在不同时段长取值下的逐年变化规律基本相似,但由于流域水资源开发等人类活动的显著影响,1973年之后的集中度、不均匀系数和极值比均明显减小,且径流年内分配的集中程度和不均匀性均要小于珠江流域的另外两大水系西江和北江。

Based on the daily streamflow data at the Boluo station covering 1954-2009,statistical analysis was done on the concentration degree,concentration period,nonuniform coefficient and extrema ratio with aim to understand the annual distribution of streamflow by taking into account the lengths of the time intervals.The results indicate that the concentration degree and the concentration period of hydrological processes are not influenced by the lengths of the time intervals.The long-term average of the concentration degree is 0.35 and the time when the higher concentration degree occurs is usually the early July.The nonuniformity and related changing magnitude is lengthening with shorter time intervals and is in negative relations with the log length values of the time intervals.The long-term average of the nonuniform coefficient is 0.62 based on monthly streamflow data and is 0.89 based on the daily streamflow data;the extrema ratio is 8.63 based on the monthly streamflow and is 39.55 based on the daily streamflow.Annual distribution of streamflow is subjected to similar changing properties with different lengths of the time intervals.However,due to impacts of human activities such as the human withdrawal of water resources,the concentration degree,nonuniform coefficient and extrema ratio are evidently decreasing after 1973 with smaller concentration degree and nonuniformity when compared to other tributaries of the Pearl River basin,i.e.the Beijiang River and the Xijiang River.