Averaging Process of Runoff Characteristics within Small Watersheds

流域内的径流现象是地质和水力性质差异很大的区域内水流特性平均化过程的结果。本文通过对两个试验流域的降雨量、土壤含水量、河流流量和地下水位变化等水文要素的观测，研究了小流域内径流特征的平均化过程，并与地表、中间带和地下含水层的水流过程的物理相联系。根据观测数据，讨论了平均过程。通过该项目取得的成果总结如下。<i>由于地质条件的不同，局部地下水位的变化也有很大的差异。通过统计分析，讨论了地下水动态的时间尺度和空间尺度。<ii>本文用&lt;（delta）^（18）&gt; O-氧示踪法研究了小流域内的径流路径。然后，它建议，即使是直接径流分量可能主要由通过次表层区域的流量分量提供。<iii>这些结果已应用于讨论较大流域和城市地区的径流过程。在此基础上，对实际流域内径流过程的平均化过程或集总尺度等问题提出了新的认识。

The runoff phenomena in a watershed appear as the results of the averaging process of the flow charactersitics within various regions with wide diversities in geological and hydraulic properties. This research project intends to investigate the averaging process of runoff characteristics within a small watershed in connection with the physical phases of flow process in the ground surface, intermediate zone and also ground water aquifer.For this purpose the hydrological amounts such as rainfall, soil moisture, river discharge and ground water level fluctuations etc have been observed in the two Test Basins. Based on the observed data, the averaging processes have been discussed. The results obtained through this project are summarized as follows.<i> ) The local fluctuations of ground water level have great diversity due to the geological conditions. The time and spatial scales of ground water behaviours have been also discussed through the statistical analyses.<ii> ) The flow pathes of rainfall-water within a small watershed have been clarified by means of the <(delta)^(18)> O-Oxyzen-tracer. It is then suggested that even the direct runoff component may be supplied mainly by the flow component through the sub-surface region.<iii> ) These results have been applied to discuss the rainfall-runoff process in rahter greater watersheds and also the urban region. Then several knowledges have been newly derived with respect to the averaging process or lumping scales of runoff processes within actual watersheds.