THE RELATIONSHIP AND TREND OF MONTHLY AVERAGE FLOW AND TOTAL PRECIPITATION OF VARIOUS PERIODS IN MOUNTAINOUS WATERSHEDS WITH DIFFERENT TYPES OF GEOLOGY

Abstract

 This study analyzed the correlation coefficient (R) between the monthly average flow (MF) and the total precipitation (TP) of various periods in several mountainous watershed in Japan, discussing the difference between watersheds mainly focusing on the difference of geology. As a result, in low-water periods, TPs showing strong correlations with MFs differed by watersheds. The dominance of volcanic rock formed in the Quaternary period seemed to be related to higher Rs between the MFs and TPs of longer periods because of its high permeability. In addition, Mann-Kendall test was conducted for MFs, TP of various periods and the annual precipitation to verify the validity of comparing the trend of the flow and the total precipitation of influential periods rather that the annual precipitation. No trend was seen in the annual precipitations of all watersheds, although MFs showed increasing trends in some months and watersheds during low-water periods and some of the TPs whose Rs were higher than 0.6 with that flow also showed increasing trends.