首次利用GIS技术并结合沉积学研究结果,计算全新世两个时段石羊河流域终闾湖泊的面积,建立石羊河流域水热平衡模型,进而恢复全新世两个时期的降水量。
The study of lake evolution is one of the important aspects of study of global change.Inland lakes are influenced by climatic change more sensitively than lakes in humid area.It is significant to study the evolution of inland lakes.Gansu Corridor is located in the regional edge of the Eastern Asia Monsoon.Because it is sensitive to climatic change due to its fragile eco-environment, it is an ideal regied for studying global change.In the prehistoric period a large terminal lake——Zhuyeze Lake once existed in the studied area——Shiyang River drainage that is located in the eastern Gansu Corridor.Since the historic period it has gradually shrunk into many small lakes, and these small lakes dried up and disappeared in succession.This article first tries to inquire into terminal lake evolution in this studied area by combining techniques of GIS with the results of deposit study.Digital Terrain Model(DTM) of lake area in the lower reaches of the Shiyang River is built.Space time evolution of terminal lakes was analyzed and the lake area of different periods in Holocene was calculated according DTM.The precipitation of two periods during Holocene was calculated by a mathematical model which applies to an ideal situation of terminal lake in the Shiyang River drainage, following the water and energy budget principle under the situation that no lake exists now.Preliminary results indicate that water levels reached 1320 m and 1314 m in 5000 a B.P.and 3600 a B.P.during Holocene, and terminal lake areas are 2130 km2 and 870 km2.Landforms around the basin reflected in the DTM suggest that if the water level reaches 1320-1330m, the Shiyang River drainage will become an outflow drainage.The lake of 2130 km2 maybe is the largest lake in this drainage.During late Holocene after 3600 a B.P., the large terminal lake broke into two parts.According to the model of water and energy budget in the Shiyang River drainage, precipitation of above two periods was 250-256 mm and 186-188 mm, more than that of modern time by 49%-52% and 11%-12% respectively.And a lake of 580 km2 would have appeared in the basin if there were no human activities in this area under modern climate situations.Analysis of sensitivity factors of the model indicates that temperature and vaporpressure have less effect on precipitation than cloudiness, albedo and the Bowen ratio.Compared to other regions, the Shiyang River drainage is more sensitive to climate variations.
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