Abstract
This study analyses, compares and correlates historical hydrometeorological data for the Zhetysu Alatau region and its main rivers (Lepsy, Sarykan, Koktal, Byzhy) to document characteristics and evidence of changes in climate change (temperature and precipitation) and its impact on annual and monthly river runoff. This study applies Andreyanov method for computation of runoff data and Mann-Kendall statistic method for assessing statistically significant or weak trends. The study reveals that the pattern of temperature for period of 1960-2020 and runoff for period of 1930-2019 has changed in the region. Mann-Kendall test result indicates a statistically significant increase in temperature at all meteorological stations (p < 0.01), while the fluctuations in precipitation trends are not meaningful (p > 0.05). Andreyanov method shows significant changes in intra-annual runoff trends, e.g., calculations for the period of 1965-2019 show a decrease of 5.3% in summer runoff in the Sarykan river, and the increase in runoff in the remaining months was 6.4% higher compared to the period of 1930-1965. Furthermore, the Mann-Kendall test confirms a significant positive trend in the change of seasonal runoff for the Sarykan, Byzhy, and Koktal rivers (p < 0.02). The precipitation is one of the main factors influencing river runoff and the correlation coefficient between river runoff and precipitation for Lepsy river is r = 0.81; for Byzhy river is r = 0.70; for Koktal river is r = 0.62; for Sarykan river is r = 0.60.