西北干旱区水资源与第四纪盆地系统

THE WATER RESOURCES RELATED WITHQUATERNARY BASIN SYSTEMS IN ARID AREA OF NORTHWEST CHINA

西北干旱区第四纪盆地主要是在中、新生代盆地基础上发展而成，一般可分为前山带山间断拗盆地和山前断拗盆地两大类，前者规模较小，后者规模较大，居主导地位。盆地构造形式大部分为单斜式不对称盆地，又可划分为单列型单斜式盆地和多列型单斜式盆地，包括部分地下隐伏盆地，形成盆地系统。盆地构造主要受区域深大断裂和新构造作用控制，具有明显的方向性和规律性。每条河流一般要流经２～３个盆地，形成由盆地系统构成的一个统一的水文系统。全流域的水循环系统和水资源系统，均受盆地系统的制约。因此，研究干旱区第四纪盆地系统，对合理开发利用水资源具有重要意义。

ll large inland basins in the typical arid area of northwest China,known as the Zhungeer,Tarim,Chaidamu and Hexi Corridor,are Meso Cenozoic fault depressions with identical geological background and structural history.The Quaternary basins with typical foredeeps features inherited from Meso Cenozoic basins are controlled by active deep fractures,and characterized by long sequences of gravel formations and strong neotectonics. There are two basic types of Quaternary basins:the fore depression type and the intramontane depression type.The former is the most frequent type usually exhibiting an asymmetrical,monoclinal depression with a deep trough near the mountains.Two sub types of fore depressions can be distinguished:the mono type and the multi type.The mono type features only one single monoclinal depression,where as the multi type contains two to three or more parallel rows of monoclinal depressions,usually separated by Tertiary anticlinal upwarped folds associated with faulting.All fore depressions show a similar northward trend. The Quaternary basins are allclosely connected with streams originated in the mountains.These streams pass through two or three basins and discharge into an inland lake.Surface water and ground water are transformed to each other repeatedly in these basins.Variations in neotectonics are responsible for the differences in structures and hydrological features among these basins. Because the outflow of the surface runoff from the mountainous area is nearly equivalent to the total water resources of the entire region,a basin system thus also represents a water resource system of the whole drainage.Therefore,in the context of scientific management of water resources,the study of basin systems and hydrological systems is crucial for optimal allocation and integrated development and rational use of surface water and groundwater.