青海湖水文特征及水位下降原因分析

青海湖自有记载以来,湖水位一直处于下降之中。通过分析流域内的各项水文因子的特征及湖泊水量平衡,看出流域内降水有逐步变小的趋势;湖泊长期处于水量收支负平衡中,致使湖水水位下降。降水变小及湖水位下降又改变了流域水文环境,使径流变小、径流系数下降。通过进一步分析发现,青海湖对降水变化的敏感性要大于其它因子的变化。

THE HYDROLOGICAL CHARACTERISTICS AND THE CAUSEOF THE DECLINING OF WATER LEVEL INQINGHAI LAKE

Qinghai Lake which is a saline lake located in an enclosed drainage basin in the eastern Qinghai-Tibet Plateau is the largest lake in China. The lake has a drainage area of 29,561 km2, of which approximately 15 percent is water surface. Since last century to 1986, the lake level has declined to 3193.84 m and the area of lake has shrunk to 4304 km1. According to the ob-served data in the 1958?986, the annual precipitation and evaporation in the lake region and the runoff flowing into the lake are obtained, which is 407 mm/a, 954.5 mm/a and 63.7 mm/a respectively. There is a declining trend in precipitation and runoff which results in rainfall decrease in the catchment and lake level declining, and causes vegetation degenera-tion and decrease of runoff ratio. Consequently, the annual deficit of Qinghai lake has been calculated. The normal lake deficit is 4.67x10s m3, that is, the average annual lake level dec-lined 10.5 cm. By means of regression, the quantitative relationship between the lake budget and the climatic parameters such as atmopheric temperature and precipitation has been obtain-ed. It shows that the changes in lake level are more sensitive to the precipitation change.