Movatterモバイル変換

• Al- Shakil

  Graduate School of Science and Technology, Niigata University, Japan

• Andrew Charles Whitaker

  Institute of Science and Technology, Niigata University, Japan

Historically, the Japan Sea region of Honshu has experienced some of the heaviest snowfalls in the world, though snowfalls are now decreasing due to global warming. This study examined changes in streamflow seasonality and trends in monthly runoff during the past 60 years at nine river basins located across Niigata, Yamagata, Akita and Aomori Prefectures. A streamflow seasonality index (Center Time,CT) was adopted, and meteorological stations paired with gauging stations to analyze the dependence of streamflow seasonality on air temperature. Overall, there is a strong tendency for winter and early snowmelt season flows to increase (December to March), while the peak snowmelt season flows in April are decreasing. In most cases,CT shows a trend for earlier seasonal runoff, and we confirm a strong linear relationship betweenCT and temperature during snow cover season (December to April). The relationship betweenCT and temperature appears to be stronger in the south of the study region (meanR² = 0.64) than in the north (meanR² = 0.37). In addition, the regression slope (temperature sensitivity ofCT) is greater in the southern region, with an average value of –6.3 days per degree Celsius compared to –4.2 days per degree Celsius in the northern region.