Hydrological Studies of the Heihe River Basin in the Northwest Arid Region of China

Because of the extremely continental dry climate, the Heihe River basin is characterized by less precipitation, rapid evaporation and low runoff ratio. The mountain watersheds of the Heihe River basin receive much more precipitation, and possess lower temerature and lower evaporation rate as compared with the basin area in front of the mountains, therefore are the runoff generation area of the Heihe River basin. A trend analysis indicate that, in the Heihe River basin during the 40 years from 1956 to 1996, air temperature increase is mainly in winterm, next in autumn, while summer precipitation increase trend. The runoff simulation is carried out with a model for simulating the response of monthly runoff from the mountain watersheds in ta inland area of northwest China to climate change. Taken the mountain watershed of the Heihe River basin controlled by the Yingluoxia Hydrometric station as an example, the water balance and hydrological processes are simulated. The water balance simulation indicates that from the dry years to the wet years, precipitation, evaporation, runoff and runoff decrease. The simulation of funoff change under the global warming indicates that, from 1990s to 2000s, as compared with the runoff during 1980s, along with the increase of air temperature, precipitation and glacier melt water increase in some amount. This compesates in some degree the runoff reduction caused by the increment range is within 3%. Then, to 2010s and 2040s, the increase of precipitation and glacial melt water is not enough to compensate the runoff reduction caused by air temperaturre increase, and the runoff will decrease in the aptitude within 10%

104 Annals of Glaciology 50(53) 2009 Assessment of glacier water resources based on the Glacier Inventory of China

ABSTRACT. According to the division into subareas of water-resource distribution in China, and based on the Glacier Inventory of China (GIC), China’s total glacier water storage is 5040.2 � 10 9 m 3, 33.0% of which is distributed in the southwest drainage basins and 64.1 % in the northwest inland drainage basins, forming enormous solid reservoirs with plentiful freshwater storage. Glacier change in China is estimated for the periods from the Little Ice Age (LIA) maximum to about 1960 and from 1960 to 1995. The relative glacierized area loss is 23 % and 8.9 % respectively for maritime glaciers and 15 % and 4.9 % respectively for continental glaciers. The normal annual glacier meltwater runoff is estimated at 60 465 � 10 6 m 3 by the climate parameter temperature-index method, 38.7 % of which is distributed in the northwest inland drainage basins, and at 61 574 � 10 6 m 3 by the glacier system temperature-index method, 41.5 % of which is distributed in the northwest inland drainage basins. Simulation of glacier meltwater runoff under the temperature change ratio of 0.03 K a –1 by the glacier system model in west China between 1980 and 2000 indicates that the total glacier meltwater runoff increment is 10.8% overall, 14.3 % in the inland drainage basins of northwest China and 9.0 % in the outflow drainage basins of southwest China. 1

Recent and future climate change in northwest china

As a consequence of global warming and an enhanced water cycle, the climate changed in northwest China, most notably in the Xinjiang area in the year 1987. Precipitation, glacial melt water and river runoff and air temperature increased continuously during the last decades, as did also the water level of inland lakes and the frequency of flood disasters. As a result, the vegetation cover is improved, number of days with sand-dust storms reduced. From the end of the 19th century to the 1970s, the climate was warm and dry, and then changed to warm and wet. The effects on northwest China can be classified into three classes by using the relation between precipitation and evaporation increase. If precipitation increases more than evaporation, runoff increases and lake water levels rise. We identify regions with: (1) notable change, (2) slight change and (3) no change. The future climate for doubled CO2 concentration is simulated in a nested approach with the regional climate model-RegCM2. The annual temperature will increase by 2.7 degrees C and annual precipitation by 25%. The cooling effect of aerosols and natural factors will reduce this increase to 2.0 degrees C and 19% of precipitation. As a consequence, annual runoff may increase by more than 10%

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