流域初始状态对环境同位素法划分流量的影响

Influence of Initial State of Watershed on Hydrograph Separation Using Stable Isotopes

在使用同位素示踪剂划分流量时,流域初始状态会对事件水和事件前水分割产生影响。为研究流域初始状态对环境同位素法划分流量的影响,以和睦桥流域2015—2016年间4场降雨事件为研究对象,根据稳定同位素含量(δ 18 O)确定其在流域出口断面径流的不同水源组成比例,着重分析流域不同初始流量和前期土壤含水量对流量过程线划分的影响。结果表明:流域出口径流总量中事件前水占优,洪峰流量以事件水为主;流域不同初始状态下同位素分割结果不同,表明该流域存在多种产流机制,流域初始流量与总径流系数及事件水贡献比例呈负相关;前期土壤含水量与事件水贡献比例的影响模式复杂多变,但在前期土壤含水量较高或前期降雨较多的情况下,总径流中事件水贡献比例将降低。

The separation of storm hydrographs using stable isotope tracers provides a scientific basis for the study of runoff-formation mechanism and runoff calculation.Many research results show that there is a correlation between the initial watershed state and the event/pre-event water proportion. Hydrograph separations were conducted using stable isotope(δ 18 O) to analyze the proportion of event/pre-event water on four rainfall events during 2015-2016 in Hemuqiao watershed and especially the influence of antecedent streamflow and soil moisture. The results indicated that pre-event water dominated streamflow but the event water accounted for more in the peak;the difference in hydrograph separations implied that multiple runoff generation patterns existed in different initial system states. The runoff coefficient and the contribution of event water to streamflow were negatively correlated with antecedent streamflow. The relationship between the contribution of event water and antecedentsoil moisture was complicated and the percentage event water of streamflow would decrease in the condition of high antecedentsoil moisture or large antecedent 5-day rainfall.