Temperature and precipitation play an important role in the distribution of intra-annual runoff by influencing the timing and contribution of different water sources.In the northern and southern slopes of the Middle Tianshan Mountains in China,the water sources of rivers are similar;however,the proportion and dominance of water sources contributing to runoff are different.Using the Manas River watershed in the northern slope and the Kaidu River watershed in the southern slope of the Middle Tianshan Mountains as case studies,we investigated the changes in annual runoff under climate change.A modified hydrological model was used to simulate runoff in the Kaidu River and Manas River watersheds.The results indicated that runoff was sensitive to precipitation variation in the southern slope and to temperature variation in the northern slope of the Middle Tianshan Mountains.Variations in temperature and precipitation substantially influence annual and seasonal runoff.An increase in temperature did not influence the volume of spring runoff;but it resulted in earlier spring peaks with higher levels of peak flow.Damages caused by spring peak flow from both slopes of the Middle Tianshan Mountains should be given more attention in future studies.
Accompanied by global climate change, the annual mean air temperature has experienced a strongly increasing trend in the western China, especially in Xinjiang. The Global Climate Model （GCM） provides an efficient and direct method to assess the process of global climate change and project future climate driven by various factors, especially human activity. Since GCMs＇ low spatial resolution cannot capture the characteristics of local climate change due to the land surface＇s complexity, downscaling methods, including Regional Climate Model （RCM）, Bias Correction method and Statistical Method, are proposed to process raw data from GCMs for local climate change assessment. This study applied the delta method, one of Bias Correction methods, to make horizonta! resolution of 24 GCMs models＇ monthly outputs into 0.5~C for analyzing Xinjiang＇s future climate pattern under three IPCC SRES. A comparison between the results from downscaled dada and raw data from GCMs shows that downscaling methods can improve local climate changing feature in complex land surface and topography and to reduce the uncertainty of climate data generated from GCMs in Xinjiang. The results showed that scenarios A1B, A2 and B1 generated similar patterns and trends in annual mean air temperature and annual precipitation in the early 21st century with fluctuations in the middle of the 21st century. The annual mean air temperature will reach 10℃ 11.1℃ and 8.5℃ in A1B, A2 and B1 by the end of the 2Pt century, respectively, while the annual precipitation during the projection period will experience an increasing trend with a little fluctuation. During 2020 and 2070, the annual temperature in A1B scenario is greater than the other scenarios on regional average. The annual precipitation in the A1B scenario is also greater than other scenarios during 2020 and 2040 on regional average. However, there exists a large uncertainty within different SRES with an range of 6℃ in annual temperature and about 200 mm in annual precipitation.
The sensitivity and vulnerability of water resources to climate change is difficult to assess. In this study, we used a conceptual hydrologic model to investigate the sensitivity of streamflow to climate change. We also pro- posed a framework to evaluate the vulnerability of water resources in arid regions. We applied this framework to a case study of the Shiyang River Basin in Northwest China. Results showed that the precipitation and streamflow in Shiyang River Basin exhibited no significant trends of change from 1956 to 2010. In the past five decades, however, the temperature increased significantly by 0.37℃ per decade. According to the sensitivity assessment, a 10% in- crease in precipitation and a 1℃ increase in temperature altered mean annual streamflow by averages of 14.6% and -0.5%, respectively, from 1988 to 2005. In the 2000s, the calculated vulnerability of water resources in Shiyang River Basin was more than 0.95, indicating severe vulnerability. The increase in the amount of precipitation and the imple- mentation of water-saving measures can reduce the vulnerability of water resources in the future; if precipitation in- creases by 10% per decade and the use of irrigation water decreases by 15% in the 2030s, the evaluated value of water resources vulnerability will be reduced to 0.79. However, the region remains highly vulnerable. The proposed framework for vulnerability assessment can be applied to the arid regions in Northwest China, and the results of our efforts can identify adaptation strategies and improve the management of water resources in such regions.
Long WANJun XIAHongMei BUSi HONGJunXu CHENLiKe NING
