Abstract:Based on the temperature, precipitation and runoff data of Lake Issyk-Kul in the past 70 years, the Mann—Kendall method, abrupt change test, and wavelet analysis were used to study the characteristics and differences of the temperature, precipitation and runoff in the typical watershed. On this basis, the effects of regional climate change on runoff were also discussed. The results showed that: (1) The temperature in the typical small watershed of Issyk-Kul basin in 1951—2012 tended to increase; the temperatures in Cholpon- Ata Station (central lake basin) and Kyzyl—Suu Station (eastern part) rised from 1975 and 1989 respectively. The increasing trend of temperature in autumn had a greater contribution to the temperature increase. The variation of precipitation was relatively complicated, and the overall trend was increasing. Among them, the precipitation in autumn had the largest increase. (2) The annual runoff changes of 4 typical hydrological stations in the study area were not the same due to the direct influence of temperature and precipitation. The runoff of Cholpon-Ata, Chong-Ak-Suu and Chong- Kyzyl-Suu station showed an obvious increasing trend While Karakol Station showed a significant downward trend. The trend of autumn in each station was significant, showing an increasing trend. From the runoff distribution in different seasons in a year, the increase of runoff in El Pont and Chong- Kyzyl-Suu station was obvious with the largest increase in summer. However, the decrease of summer runoff in Cholpon-Ata station was the largest. (3)Through Pearson correlation analysis and principal component analysis, on the inter-annual scale, there was a significant correlation between the runoff of each hydrological station and the temperature and precipitation. The increase in temperature and precipitation affected the runoff output. (4) From the analysis of cyclical changes, the cyclical changes of temperature, precipitation and runoff were obvious, and the fluctuations were basically the same, indicating that the response of runoff to temperature and precipitation was prominent.