Impact of climate change on surface water resource and tendency in the future in the arid zone of northwestern China

The surface water resource in the arid zone of northwestern China is pregnant in the 6great mountain systems induding snow covers,glaciers,rivers and lakes.Though the climate fluctuates,becoming warmer and drier,and the water resource trends to wither during the 20th century,it is evident thatin the Holocene Megathermal there would be a more plentiful water resource.During the Little Ice Age,theglacier area and the amount of runoff and lake water were also higher than those at present.It is estimated thatthe temperature in mountains of western China would be 1℃ warmer by 2030 A.D.,when the precipitationand evaporation would be some higher,the snow cover would be lower in plains and higher in mountains,gla-ciers would retreat further,many small glacier would disappear,river runoff would increase with a highervariability,most of the lakes would be in a negative balance state and would wither further.