基于同位素示踪的黄土塬区小流域径流组分来源解析研究

Study on runoff components in small watershed in loess tableland based on isotope tracing

黄土塬区独特的水文地质结构极大地增加了当地水循环过程的复杂性。为探究黄土塬区河道径流组分演变过程及产流机制,选择黄土塬区王东沟小流域为研究区,针对3次典型降雨-径流事件,对雨水与径流流量及~2H含量进行了高频连续采集与测试分析,并通过二端元混合模型对径流的主要组分(降雨产流和基流)进行分割解析,得到以下主要结论:(1)小雨和中雨事件下径流水δ~2H呈现先增长后减小的变化趋势,而大雨事件呈现先减小后增加的趋势。大雨事件和小雨事件洪峰径流组分几乎全部来自于降雨直接产流,这可能与雨强有关。(2)3场降雨的有效产流面积由大到小排列为小雨(3.76 km^(2))、大雨(3.54 km^(2))和中雨(2.89 km^(2))。有效产流面积和平均雨强、30 d影响雨量呈现正相关关系,但与降雨量的相关性很弱。(3)试验中,事件尺度下小流域的主要产流机制为超渗产流。本研究对黄土塬区水资源的高效利用与配置优化具有重要意义。

The unique hydrogeological structure of the loess tableland region greatly increases the complexity of the local water cycle process. To explore the evolution process of runoff components and the mechanism of runoff generation in the loess tableland region, Wangdonggou small watershed is selected as the study area. In response to 3 typical rainfall-runoff events, continuous observations are made on rainfall and river runoff processes, and the ~2H content in rainwater and runoff water are continuously collected with high frequency. With test analysis, the main components of runoff(rainfall runoff and base flow) are segmented and analyzed through a two-terminal mixed model, and the following main conclusions are obtained:(1) Under light rain and moderate rain events, the δ~2H in runoff water shows a trend of first increasing and then decreasing, while the heavy rain events show a trend of decreasing first and then increasing. Almost all the peak runoff components of heavy rain and moderate rain event come from direct rainfall, which may be related to the rain intensity.(2) The effective runoff area of the three rainfall-runoff events in descending order is light rain event(3.76 km^(2)), heavy rain event(3.54 km^(2)) and moderate rain event(2.89 km^(2)). The effective runoff area is positively correlated with the average rainfall intensity and 30 d impact rainfall, but the correlation with precipitation is very weak.(3) In this experiment, the main runoff generation mechanism is infiltration-excess runoff at the event scale. This research is of great significance to the efficient use and allocation of water resources in the loess tableland region.