ANALYSIS OF MECHANISM OF WATER CIRCULATION IN KUSHIRO WETLAND FROM COMPARISONS WITH 1970S

Abstract

Kushiro wetland located in the eastern part of Hokkaido was registered by Ramsar Treaty in 1980, and was registered as a national park in Japan in 1987. The previous studies reveal that the area of alders have been expanding, which results in the decrease in the wetland area in the past 30 years. It is demonstrated that the increase in alders is due to the accumulation of sediment and the increase in nutrient in the wetland. However, the mechanisms, which control sedimentation and nutrient transport, have not been clarified. Therefore, this study aims to understand the mechanism of water circulation in Kushiro wetland by using distributed hydrological model from the comparisons between 2003 and 1970s. As a result, rainfall pattern is found to change which leads to in the increase in discharge from 1970s to 2003.