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

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, 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. Evaluating these effects is important for regional water resources assessment and management.

Now, sensitivity analysis method is widely used to estimate the sensitivity of annual runoff to precipitation and potential evaporation. Researchers have used the sensitivity analysis method to separate the effects of climate variability and human activities on runoff in some river basins. The results showed that the impacts of climate variability and human activities on river discharge were more significant in arid and semiarid areas than that in humid areas.

In the last 50 years, the inland river basins in arid region of northwest China have experienced changes both in climate and land use/cover. It is important to understand the hydrological responses to these changes in order to develop sustainable basin management strategies. So, Prof. CHEN Yaning and his research team investigate the changes in one of the inland river basins in arid region, the Kaidu River Basin. The objective of this study was to (1) determine trends and step change points in annual runoff of the basin and (2) estimate the effects of climate variability and human activities on runoff.

The nonparametric Mann–Kendall test and the Mann–Kendall–Sneyers test were used to identify trend and step change point in the annual runoff. It was found 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 has been published on Theoretical and Applied Climatology, 2012. doi: 10.1007/s00704-012-0680-4. The paper can be downloaded from http://www.springerlink.com/content/h3t7548682427041/.