Quantifying the Effects of Climate Variability and Human Activities on Runoff for Kaidu River Basin

The hydrological cycle of a basin is a complex process influenced by climate, physical characteristics of the basin, and human activities. With the worsening of the water shortage problems and the increasing number of water-related disasters globally, the effects of climate variability and human activities on water resources have long been a focus of global hydrology research. In arid and semiarid regions, the effects of climate variability and human activities on runoff are significantly more sensitive, and these effects have resulted in reduction or increase in water yield. Evaluating these effects quantitatively is important for regional water resources assessment and management.

The Kaidu River, a main tributary that discharges into the downstream of the Tarim River, is situated at the north fringe of the Yanqi Basin on the south slope of the Tianshan Mountains in Xinjiang. In the Kaidu River Basin, climate variability and water-related human activities have influenced water resources, and basin water resources management is facing a huge challenge.

Therefore, CHEN Zhongsheng et al. used data from the Kaidu River Basin during the period of 1960–2009 to estimate the effects of climate variability and human activities on runoff for the Kaidu River Basin and determine trends and step change points in annual runoff of the basin. The nonparametric Mann–Kendall test and the Mann–Kendall–Sneyers test were used to identify trend and step change point in the annual runoff.

The results showed that the basin had a significant increasing trend in annual runoff. Step change point in annual runoff was identified in the basin, which occurred in the year around 1993 dividing the long-term runoff series into a natural period (1960–1993) and a human-induced period (1994–2009). Then, the hydrologic sensitivity analysis method was employed to evaluate the effects of climate variability and human activities on mean annual runoff for the human-induced period based on precipitation and potential evapotranspiration. In 1994–2009, climate variability was the main factor that increased runoff with contribution of 90.5 %, while the increasing percentage due to human activities only accounted for 9.5 %, showing that runoff in the Kaidu River Basin is more sensitive to climate variability than human activities.

This study quantitatively distinguishes the effects between climate variability and human activities on runoff, which can do duty for a reference for regional water resources assessment and management. The result was published in Theoretical and Applied Climatology in February 2013, 111: 537-545.