Characteristics of Hydrogen and Oxygen Isotopes in Rainy Season Precipitation in Jiangjiagou Watershed

The rainfall events occurred from 2001 to 2009 in Jiangjiaou watershed was analyzed.The rainfall frequency and cumulative frequency of rainfall before triggering of a debris flow can be fitted by power exponent distribution and logarithmic distribution,respectively.This result shows that the triggering of debris by rainfall is a random phenomenon,and subjects a random distribution.The isotopic compositions of precipitation over the Jiangjiagou watershed in the summer of 2010 are studied.Local meteoric water line is fitted as δD=7.1086δ18O-14.22.Its intercept is lower than that of Chinese meteoric water line which is related to the geographical and meteorological characteristics in this area.With the change of air humidity,the values of deuterium excess are positive before mid-July,and are much lower during mid-July and mid-August,then increase again after the mid-August.The δ18O value in an individual rainfall is lower as the rainfall increases.By the effort of the randomness of the mountain area precipitation,the stable isotopic concentration is higher as the attitude rises.