Quantitatively evaluating the effects of climate factors on runoff change for Aksu River in northwestern China

Much attention has recently been focused on the effects that precipitation and potential evapotranspiration (PET) have had on runoff change; however, the influence of temperature on runoff needs to be further studied. We attempted to employ the improved elasticity method to evaluate the effects of climate factors (CF, especially temperature) on runoff change for Aksu River in the arid region of northwest China. Data from Aksu River in the arid region of northwest China were analyzed to investigate changes in annual runoff and CF during the period of 1960-2010. The key findings of this study indicated that the annual runoff had a significant (P<0.01) increasing trend with a rate of 3.78x10(8) m(3)/decade, and the temperature and precipitation also exhibited significant rising trends, at a rate of 0.28 degrees C/decade (P<0.01) and 15.11 mm/decade (P<0.05), respectively, while PET showed a decreasing trend (22.66 mm/decade, P<0.01). Step change point in runoff occurred in the year 1993. Thus, we employed the mean runoff and climate factors during the period 1960-1993 as the benchmark value to measure the change. In 1994-2010, mean runoff increased by 22 %. Results also revealed that temperature rising was the most important factor that increased runoff with contribution of 45 %, while precipitation and PET were responsible for 22 and 27% of the runoff change, respectively, indicating that the runoff of increasing percentage only accounted for 6% owing to human activities and other factors, and showed that climate variability was the main reason for the runoff change in Aksu River.