Impacts of Climate Variability and Human Activities on Runoff: A Case Study in the Jinghe River Basin

Assessing the impacts of climate variability and human activities on streamflow is crucial to regional water resource management. In recent years, significant decreases in streamflow have emerged in the Yellow River basin. The Jinghe River Basin (JRB), a tributary in the middle reaches of the Yellow River, has experienced dramatic land use changes over the past decades. At the same time, the climate has also shown a significant change. The annual streamflow exhibits an apparent decreasing trend in the JRB. In this study, the non-parametric Mann-Kendall test is employed to detect the trend and breakpoint. The effects of climate variability and human activities are assessed quantitatively using the climate elasticity method and the hydrological model. The results showed that annual streamflow in the JRB decreased significantly (P<0.05) from 1956 to 2012 and that an abrupt change occurred in 1997. The annual precipitation presents a slightly decreasing trend, whereas the annual mean temperature and potential evapotranspiration show an upward trend. The results of quantitative assessment indicated that climate variability was responsible for 44.0% of the decrease in streamflow, whereas the hydrological modeling method indicated a value of 48.8%. The annual amount of water diversion from the Jinghe River increased, accounting for 20.5% of the decrease in streamflow from 1997 to 2010. Moreover, the land use and land cover change contributed to 30.7-35.5% of the decrease in streamflow. All human activities contributed to 51.2-56.0% of the decrease in streamflow. Therefore, the effect of human activities played a dominant role in the decrease in streamflow in the JRB.