弥河下游冲洪积扇咸水入侵数值模拟研究

发布时间：2018-05-14 11:39

本文选题：弥河冲洪积扇 + 咸水入侵　；参考：《济南大学》2015年硕士论文

【摘要】：咸水入侵是目前世界上滨海平原地区普遍存在地下水环境问题。其主要原因是由于人为超量开采地下淡水,引起地下水位大幅度下降,咸水与淡水之间的水动力平衡遭到破坏,导致海水或古咸水以各种方式向内陆淡水含水层入侵。咸水入侵的发生具有动态变化快、潜在危害大,难以治理等特点。研究区位于弥河下游冲洪积平原,属于农业集约化、专业化、规模化的蔬菜大棚种植区。据了解,该区域北部曾经历了三次海水入侵现象,赋存了大量卤水。研究区由于弥河多次改道形成了不同时期的古冲洪积扇、古河道带,为北部咸卤水向内陆淡水含水层的入侵提供了良好的通道。过量的地下水开采加之良好的地层条件导致研究区北部咸水入侵现象愈发严重。本文依托国家海洋局公益性行业科研专项项目“环渤海区域海水入侵、土壤盐渍化预警与防控关键技术研究示范”(201105020),在对弥河下游冲洪积扇地下水开发利用状况、水文地质条件以及咸水入侵程度调查的基础上,深入分析了研究区地下含水层分布特征以及咸水入侵的动态变化规律,构建了三维地下水流水质耦合数值模型,预测未来不同方案下的咸水入侵变化趋势,为咸水入侵防治提供科学依据。本论文主要研究内容及工作量如下:(1)本文通过对弥河下游冲洪积扇地区的气象、水文、地形地貌及水文地质等资料的收集整理,根据研究区域地质结构和水文地质条件资料,明确了地下含水层的分布特征和地下水水动态变化特征。(2)通过对弥河下游冲洪积扇地区咸水入侵历史情况的调查,在咸淡水分界线附近布设了16个水质监测剖面,对79个井点的水质情况进行取样化验分析。以1981年250mg/L氯离子浓度等值线为弥河下游冲洪积扇地区咸水入侵的初始分界线,确定了弥河下游冲洪积扇2014年咸淡水分界线的位置。(3)建立了三维非稳定流和变密度溶质运移模型,利用Visual ModFlow4.6软件中的SEAWAT模块对研究区域进行数值模拟。模拟过程中选取2008年10月1日至2010年12月31日作为本次模型的识别时段,2011年1月1日至2011年12月31日作为模型的验证时段,模拟时间1187天,共计39个应力期,时间步长设为6。通过模型反复的验证求解,选取了合适的水文地质参数。(4)利用建立好的地下水数值模型对弥河下游冲洪积扇地区进行不同地下水开采方案下未来咸水入侵变化趋势进行预测。结果表明,在未来气候条件变化下和局部压采地下水条件下,咸水入侵现象都得到了一定程度上的缓解,但局部压采地下水的方案对咸水入侵的缓解较为明显。(5)根据上述预测结果,从水利工程建设方面和相关管理部门角度出发,提出了弥河下游冲洪积扇地区相应的咸水入侵防治措施。
[Abstract]:Salt water intrusion is a common problem of groundwater environment in coastal plain area of the world at present. The main reason is that the groundwater level is greatly decreased and the hydrodynamic balance between salt water and fresh water is destroyed, which leads to the invasion of seawater or paleo-salt water into inland freshwater aquifers in various ways. The occurrence of salt water intrusion has the characteristics of fast dynamic change, great potential harm and difficult to control. The research area is located in the alluvial plain of the lower reaches of Mihe River, which belongs to the intensive, specialized and large-scale vegetable greenhouse planting area. It is understood that the northern part of the region has experienced three sea-water intrusions and a large amount of brine. In the study area the ancient alluvial fan and the paleo-channel belt were formed in different periods due to the multiple diversion of Mihe River which provided a good channel for the intrusion of the brine from the northern brine to the inland fresh water aquifer. Excessive groundwater exploitation and good stratigraphic conditions lead to more and more salt water intrusion in the northern part of the study area. This paper relies on the special project of the public welfare industry of the State Oceanic Administration, "study and demonstration of key techniques of seawater intrusion, soil salinization early warning and prevention and control" in the area around Bohai Sea, in order to develop and utilize the groundwater of alluvial fan in the lower reaches of Mihe River. Based on the investigation of hydrogeological conditions and the degree of salt water intrusion, the distribution characteristics of groundwater aquifers and the dynamic variation of salt water intrusion in the study area are analyzed in depth, and a three-dimensional numerical model of groundwater quality coupling is constructed. The trend of salt water intrusion in the future is predicted, which provides scientific basis for the prevention and treatment of salt water invasion. The main contents and workload of this paper are as follows: 1) by collecting and arranging the data of meteorology, hydrology, topography and hydrogeology in the alluvial fan area of the lower reaches of Mihe River, the paper studies the regional geological structure and hydrogeological conditions. By investigating the history of salt water intrusion in the alluvial fan area of the lower reaches of Mihe River, 16 water quality monitoring sections have been set up near the dividing line of salt and fresh water. The water quality of 79 well sites was analyzed. Taking the 1981 250mg/L chloride concentration isoline as the initial dividing line of salt water intrusion in the alluvial fan area of the lower reaches of Mihe River, the location of the salt and fresh water boundary of the alluvial fan in the lower reaches of Mihe River in 2014 is determined. The SEAWAT module in Visual ModFlow4.6 software is used to simulate the research area. During the simulation process, the model was identified from October 1, 2008 to December 31, 2010, and from January 1, 2011 to December 31, 2011, as the verification period. The simulation time was 1187 days, with a total of 39 stress periods and a time step of 6. Through the repeated verification and solution of the model, the suitable hydrogeological parameters are selected. The established groundwater numerical model is used to predict the future trend of salt water intrusion in the alluvial fan area of the lower reaches of Mihe River under different plans of groundwater exploitation. The results show that the salt water intrusion has been alleviated to some extent under the future climatic conditions and local pressure groundwater conditions. However, the scheme of local pressure extraction of groundwater can obviously alleviate the invasion of salt water. (5) according to the above forecast results, from the point of view of water conservancy engineering construction and relevant management departments, The corresponding saline water intrusion prevention measures in the alluvial fan area of the lower reaches of Mihe River are put forward.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641.8

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