STUDIES ON WATER STAGE FLUCTUATION OF YAMZHO LAKE IN XIZANG

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Studies on water stage fluctuation of Yamzho Lake in Xizang

Yamzho Lake, with a drainage area of 6, 100km2, is the largest closed interior lake in the southern part of the Qinghai-Xizang Plateau. The elevation of the lake stage is 4, 440m, lake storage is about 16 billion m3. Water recharge mainly depends on rainfall, melting water from glacier area, taking up 16%. In the drainage basin about 2% of the area is covered with glacier. Seasonal range of variation in the lake stage is small, usually less than 0. 6m. The biggest water level in a year appears in September or October, not in July or August of the rainfall concentrated period, because of the lake's self-adjustment.The lowest lake level occurs in May, June or July. In wet years the stage fluctuation has clear periodicity, in dry years the lake level tends to fall down around the year. There is a close correlation between rainfall and water level variation.Based on the analysis of the patterns of the lake level fluctuation during the recent 100 years, according to the measuring and investigation data, the fluctuation range of the lake level varied at 4 to 5 meters, and the water level has been gently descending at the rate of 0. 6m/100 years.