The Climate Change And Its Impact On The Runoff In Songpan

In this paper, Songpan were selected as the main research object, based on the data of Zipingpu hydrological stations and Songpan weather stations, climate change trends, multi-scale variations and mutability of temperature, precipitation, rainy days and extreme temperature were analyzed by using Linear trend estimation, Wavelet transform method and Mann-Kendall test. Furthermore, the Pearson correlation analysis was used to study the response of runoff to climate change. The results show that:(1) Within the study period, the annual and four season average temperature have obvious rise with fluctuation, the temperature rise of autumn and winter is the main reason for the average temperature rise. After Wavelet analysis, it showed that there are 36a, 9a, 20a, 28a primary period in the average temperature of spring, summer, autumn,winter respectively. Besides, the annual and four season average temperature appeared significant mutations rising trend at the turn of 21 century.(2) Within the study period, the annual average precipitation in the study area showed weak down trend and 19a primary period. For the average precipitation of the four seasons in the study area, it presents rise trend in spring and winter, while drop in summer and autumn. After Wavelet analysis, it showed that there are long periodic signal in the average temperature of spring, autumn and winter; summer precipitation exists 5a primary period. In addition, it appeared significant mutation rising trend in 1952 among the average precipitation of spring.(3) During the study period, the annual average rainy days in the study area showed weak down trend and distinct long periodic signal. Furthermore, it appeared significant mutations rising trend in 1957 and 1967 among the average precipitation of autumn.(4) During the study period, the annual average extreme minimum and highest temperature in the study area showed upward trend. In addition, the annual average extreme minimum temperature existed 3 a, 6a faintly periodic signal and occurred significant mutation rising trend in 1990. While during 2005 to 2014 is significant mutation rising period.(5) The correlation between contemporary of climate elements in Songpan and the annual runoff Zipingpu hydrologic among 1966 to 2001 are weaker, are low related or weak. The influence of precipitation change on runoff is more distinct than temperature and there is the most obvious change in the summer. Besides, only -correlation between runoff in Zipingpu hydrological stations and precipitation of summer in Songpan through the 0.05 significance test. While the correlation between runoff in Zipingpu hydrological stations and average annual precipitation, the annual average precipitation days, the precipitation days of summer and autumn in Songpan through the 0.05 significance test. Yet the correlation between runoff in Zipingpu hydrological stations and the other time scale of precipitation, temperature and precipitation days are not through the 0.05 significance test, which is not statistically significant. This is mainly due to the Songpan just source area of the upper reaches of Minjiang river, the catchment area is just a small part of the collection of the upstream water front field, and the climate of headwaters area in Minjiang river is very different with other parts of the upper reaches of Minjiang river.Moreover, both of the runoff in Zipingpu hydrological stations and the annual,autumn, winter average temperature in Songpan were took 12a as primary period. In the same way, both of the runoff in Zipingpu hydrological stations and the autumn average temperature, the winter precipitation in Songpan were took 5a as primary period; both of the runoff in Zipingpu hydrological stations and the spring precipitation in Songpan were took 20a as primary period.