Averaging Process of Runoff Characteristics within Small Watersheds

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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.