Influences of Climate Change and Human Activities on Tarim River Runoffs in China over the Past Half Century

Water cycle and runoff formation in hydrographic basins evolve as complex nonlinear systems under the influence of climate change and human activities. The runoffs of inland rivers in the northwest arid region of China are more sensitive to climate change than of those in the other areas. Economic growth and ecological restoration in arid region have been greatly constrained by the fragility of the environment, population growth and the unregulated use of water resources. Therefore, it is necessary to examine how climate change and human activities influencing the runoff formation in the arid region of northwest China under the conditions of global warming.

Tarim River Basin is the largest inland river basin in China, where abundant natural resources coexist with an ecologically fragile environment. A large number of studies have demonstrated the changing characteristics in temperature, precipitation, glacier, and runoff in the Tarim River Basin. But there are few quantitative analyses conduct to determine exactly how climate change and human activity worked in the runoff formation in the drainage system. Therefore, the changes in annual runoff of the three original rivers and the mainstream of Tarim River were analyzed by the non-parametric tests based on the hydrologic data during the period of 50 years.

The results indicated that: (1) headstream runoff has increased in the past 50 years, and has sharply jumped after 1990; (2) mainstream runoff decreased progressively in the past 50 years, which indicated that interference from human activities was the main cause for the decreasing runoff. This had greater negative influence than positive influence, which caused the mainstream average runoff to decrease by 5.4×10⁸ m³ from 1990 to 2008 as compared to 1957–2008; (3) if human activities remained at pre-1990 levels, climate change alone would have caused the runoff of mainstream of Tarim River to increase by 5.4×10⁸ m³ annually in the past 20 years; (4) if the climate had remained at pre-1990 conditions, human activities alone would have caused the runoff of mainstream of Tarim River to increase by 5.4×10⁸ m³ annually over the past 20 years. However, mainstream average runoff was 42.6×10⁸ m³ from 1990 to 2008 with the negative effects of human activities masked by the larger, positive effect of climate changes. The results provide a scientific basis for conservation strategies, sustainable management, and ecological restoration of the Tarim River Basin.

The result has been published on Environmental Earth Sciences, 2012, 67: 231-241. The paper can be downloaded from http://www.springerlink.com/index/395J7Q08623N3970.pdf。