Abstract
Filter separation AR method has been carried out on the daily hydrologic data of watershed of the Pin River of A=3, 850km2 in Thailand. Daily runoff time series are separated into time series of interflow and groundwater flow by the coherence gap between rainfall and runoff and daily effective rainfalls is inversely estimated from the daily runoff data. We investigated the runoff characteristics of the Pin River, that is, paying attention to runoff ratios in monthly unit. Consequently, the main results are as follows.
(1) The storage volume of the watershed seems large for the forest because runoff ratio is small and the volume of ground water is small.
(2) The monthly runoffratio changes about from 0.1 to 0.25 during the wet season in the Pin River in Thailand.
