Secular Changes of Statistical Dry-Season Discharges in Hii River Basin

The low-water design of a river in Japan, such as the dry-season discharge, is usually based on probabilistic river discharge data. In this paper, some hydrological and statistical analyses for the dry-season discharges between 1961 and 2010 in the Hii River basin were executed at 5 stations including 2 tributaries. The results showed that the probabilistic hydrologic dry-season discharges at the main stations in the Hii River and its tributaries have been arising as it nears to the present. It means the dry-season discharges in the Hii River basin have been intensified. At the same time, it also indicates that these indexes even for the same return period may fluctuate in the future.