基于GMS的北京市朝阳区地下水环境数值模拟与预测分析

GMS-based numerical simulation and prediction analysis of groundwater environment in Chaoyang District of Beijing

为研究北京市朝阳区地下水压采过程中硝酸盐污染发展趋势,基于近年来地下水观测资料及钻孔资料,利用地下水数值模拟软件GMS,建立地下水水流和溶质运移耦合模型,对研究区地下水硝酸盐的迁移扩散进行了数值模拟,并分别预测了5 a后在丰水年、平水年和枯水年三种情景下硝酸盐的分布状况和浓度变化趋势。研究表明:地下水压采过程中,研究区地下水位基本呈逐年上升的趋势,平水年地下水漏斗中心水位上升2.0~2.5 m,地下水呈西南向东北流向。硝酸盐污染羽的扩散方向与地下水流动方向较为一致,污染中心北侧污染羽向东北方向扩散,且丰水年扩散距离最远。整个区域内Ⅰ、Ⅱ类水质面积逐渐减小。污染较严重的西南地区硝酸盐浓度有所降低,且浓度梯度减小。研究区地下水流与溶质运移两者之间有着密切的联系,应加强对地下水资源的科学调度,防止地下水环境的进一步恶化。

In order to study the development trend of nitrate contamination during the process of groundwater exploitation reduction in Chaoyang District of Beijing,a coupling model of groundwater flow and solute transport is established with the groundwater numerical simulation software—GMS in accordance with the groundwater data and the borehole data observed and obtained in recent years,and then the migration and diffusion of the nitrate in groundwater within the study area are numerically simulated,while both the distribution statuses and the concentration changing trends of nitrate under the three scenarios,i.e.wet year,normal year and dry year,after five years are respectively predicted as well.The study result shows that the groundwater level in the study area basically exhibits an increasing trend year by year during the reduction of groundwater exploitation,while the water level in the center of the groundwater funnel is going to rise by 2.0~2.5 m during normal year and the groundwater is going to flow from southwest to northeast.The diffusion direction of the nitrate contamination plume is generally coincided with the flowing direction of groundwater with the diffusion of the nitrate contamination plume at the northern side of the contamination center to the northeast,while the diffusion distance is the farthest in wet year.Within the whole area,the areas with the water qualities of Class I and Class II are to be gradually decreased.The nitrate concentration of the southwestern area with more serious contamination is going to be decreased with the decrease of the concentration gradient to some extent.Both the groundwater flow and the solute transport within the study area are closely related,thus the scientific water resources dispatch is necessary to be strengthened,so as to prevent further deterioration of the groundwater environment therein.