巴丹吉林沙漠地下水对湖泊水均衡及其盐分变化的影响

发布时间：2018-02-23 13:09

本文关键词： 泉水盐湖微咸水湖积盐时间数值模拟阿拉善　出处：《中国地质大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：巴丹吉林沙漠是我国第二大沙漠,具有高大沙山和众多湖泊并存的著名景观。其内的湖泊均为地下水补给型湖泊,且多数为盐湖和咸水湖,只有少数是微咸水湖。地下水以多种方式影响巴丹吉林沙漠湖泊的水均衡状态和盐分特征。本文重点研究了地下水向湖泊排泄的方式,以及地下水对封闭盐湖、半封闭微咸水湖水盐动态的影响,并通过数值模拟方法研究湖泊群汇水范围的空间展布特征。在湖泊周边和湖底,地下水可以通过泉的方式集中进行排泄。泉的类型包括4种:沟流型下降泉、渗流型下降泉、岛状上升泉和湖底泉。其中,浅部和深部湖底泉在苏木吉林湖泊洼地都已经观测到。本文建立了地下水补给型湖泊的通用水均衡动态和盐分变化模型,并在苏木吉林南湖这样的封闭盐湖和巴丹东湖这样的半封闭微咸水湖进行了应用分析。简化的封闭盐湖水均衡模型可以重现湖泊水位的季节性变化,表明地下水向沙漠湖泊的补给十分稳定,保证了受强烈蒸发影响的湖泊只有不到0.3 m的季节性水位变幅。苏木吉林、呼和吉林等封闭盐湖的积盐时间为800年至7000年,指示盐湖一般经历了数千年的形成演变历史。半封闭微咸水湖的形成与季节性地表排水通道的存在有关,只要湖泊与下游洼地之间的地貌分水岭相对高度低于湖水位季节性变幅的1/2即可发生,使得溢流期带走的盐量与封闭期增加的盐量平衡。采用简化的水盐均衡模型,证明半封闭湖泊的动态平衡点与净蒸发耗水占地下水对湖泊补给量的比例成非线性关系。模型计算出巴丹东湖的总溶解性固体(TDS)年平均值为1.67 g/L,与观测结果1.64 g/L非常接近,说明模型是可靠的。采用MODFLOW三维有限差分建模,对巴丹吉林沙漠湖泊群三维地下水流场进行了数值模拟。在此基础上划分了湖泊汇水范围,并讨论了湖与湖之间汇水范围的相互影响。湖泊群对区域地下水产生向心流的作用。浅层地下水的分水线呈U字形的包围单个湖泊,并与上游湖泊U字形分水线组成汇水范围,可形成廊道型汇水带。在剖面上,存在分隔浅层地下水和深层地下水的分水线。向湖泊汇水的流线簇具有三维叠置结构,下游湖泊的流线簇存在多个分支。汇水范围控制了湖泊接受地下水的水量来源,并因此而间接控制了湖泊对浅层地下水和深层地下水盐分的输入比例。
[Abstract]:The Badain Jilin Desert is the second largest desert in China, with a famous landscape of high sand mountains and numerous lakes. The lakes in the desert are all groundwater recharge lakes, most of which are salt lakes and saltwater lakes. Only a few are brackish lakes. Groundwater affects the water balance and salt characteristics of Badain Jilin desert lake in many ways. This paper mainly studies the way of groundwater discharging into lake and the effect of groundwater on confined salt lake. The effects of salt and water dynamics in semi-enclosed brackish lakes, and the spatial distribution characteristics of the catchment range of lakes are studied by means of numerical simulation. Groundwater can be discharged centrally by way of springs. The types of springs include four types: trench type descending springs, percolation type descending springs, island rising springs and lake bottom springs. Both shallow and deep lake bottom springs have been observed in the Jiangsu and Jilin lake depressions. In this paper, a general model of water equilibrium and salt variation of groundwater recharge lakes is established. The application analysis is carried out in the closed salt lakes such as the South Lake of Jiangsu Province and the semi-enclosed brackish lakes such as Badandong Lake. The simplified model of the water balance of the closed salt lakes can reproduce the seasonal variation of the lake water level. The results show that the recharge of groundwater to desert lakes is very stable, which ensures that the seasonal water level of lakes affected by strong evaporation is less than 0.3 m. The salt accumulation time of closed salt lakes such as Jiangsu, Huhe and Jilin is 800 years to 7000. The formation of semi-enclosed brackish lakes is related to the existence of seasonal surface drainage channels. As long as the relative height of the geomorphic watershed between the lake and the lower depressions is lower than 1/2 of the seasonal variation of the lake water level, the amount of salt carried away during the overflow period is balanced with the increased salt amount in the closed period. A simplified water-salt equilibrium model is adopted. It is proved that the dynamic equilibrium point of semi-enclosed lake is nonlinear to the proportion of net evaporation water consumption to the recharge of groundwater to the lake. The model calculates that the annual average value of total dissolved solid state TDSs in Badandong Lake is 1.67 g / L, which is very close to the observed result of 1.64 g / L. It is proved that the model is reliable. The 3D groundwater flow field of the Badain Jilin Desert Lake Group is numerically simulated by using MODFLOW 3D finite difference model. On this basis, the catchment range of the lake is divided. The interaction between lake and lake catchment range is discussed. The effect of lake group on regional groundwater flow is discussed. The shallow groundwater is surrounded by U shape and forms a catchment range with upstream lake U zigzag line. In the section, there is a waterline separating shallow groundwater from deep groundwater. The streamlines of catchment to lakes have three dimensional superposition structure. There are many branches in the streamline cluster of the downstream lakes, and the catchment range controls the source of the water quantity accepted by the lake, and thus indirectly controls the input ratio of the lake to the salt content of the shallow groundwater and the deep groundwater.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P641;P343

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