| Groundwater resources are important strategic water resources.With the development of industry and population increase,the problem of the contradiction between the supply and demand of water resources in Beijing has become increasingly prominent.In addition,in recent years,the amount of groundwater extracted and recharged is out of proportion,groundwater overexploitation is serious,and the groundwater level continues to decline.In order to further strengthen the restoration of groundwater,since 2019,Beijing has begun to use the Yongding River to implement ecological replenishment projects.Identifying the relationship between ecological replenishment and groundwater dynamic response is the key for making a scientific replenishment plan,and it is also an urgent problem to be solved.In this paper,the Beijing section of the plain area of the Yongding River Basin is used as the research area,groundwater numerical simulation methods are used as the main research method,combined with the ecological replenishment scheme of the Yongding River,to study the dynamic changes of ecological replenishment.The main results of the research are as follows:(1)The groundwater balance in the study area under the current conditions is studied.On the basis of analyzing the hydrogeological conditions of the Yongding River Basin,using GMS groundwater numerical simulation software,a numerical model of groundwater flow in the Beijing section of the Yongding River Basin plain area was established under the current conditions from 2011 to 2018.The total area of the simulation area is about 657.85 km~2.The model was debugged and the results of the model operation were analyzed.During the simulation period,the total groundwater replenishment difference in the Beijing section of the Yongding River Basin plain area was about 0.35×10~8m~3/a,which was in a positive equilibrium as a whole,and the groundwater level rose as a whole,with a maximum increase of about8 m.(2)Analyzed the response process of ecological water replenishment and groundwater in 2019.Combined with the 2019 Yongding River Basin ecological replenishment plan,considering the delayed effect of ecological replenishment on groundwater,a numerical model of groundwater flow under water replenishment conditions was established.The simulation period is from January 2019 to December2019.The results show that the ecological replenishment infiltration in the study area in 2019 is about 1.03×10~8 m~3/a,and the overall groundwater is in a positive equilibrium.At the end of water replenishment on June 8,2019,the impact area of ecological replenishment on groundwater was about 100.82 km~2.At the end of the simulation period on December 31,2019,the area of impact of ecological replenishment on groundwater reached 236.27 km~2.Within the scope of ecological water replenishment,the groundwater level will rise by an average of 2.4 m.(3)Forecast and analyze the scope and extent of the impact of water supplementation on groundwater in 2020.Based on the groundwater flow numerical model under the ecological water replenishment conditions of the Yongding River in2019,combined with the ecological water replenishment plan of the Yongding River in 2020,a groundwater flow prediction model under the water replenishment conditions in the study area was established.The simulation period is from January2020 to December 2020.In 2020,the total recharge of groundwater in the study area is about 3.50×10~8 m~3/a,the total excretion is about 2.99×10~8 m~3/a,and the recharge of ecological water infiltration is about 1.03×10~8 m~3/a.At the end of 2020,the average groundwater level will rise by about 1.46 m,and the total area affected by ecological replenishment will be about 448.44 km~2.The upper reaches of the Beijing section of the Yongding River Basin has a width of about 6km,the middle reaches of about 9 km,and the downstream of about 6-7 km. |
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