Research On The Response Of Groundwater To Climate Change In Anyang River Alluvial Fan

Groundwater plays an important role in maintaining climate and ecosystem changes.In the context of global warming,the frequency and intensity of extreme weather such as droughts and floods have increased,posing threats to the safety of human life and property.The impact of climate change on surface water resources has caused humans to reduce or increase the development and utilization of groundwater resources,thereby indirectly affecting the groundwater cycle.Therefore,the impact of climate change on groundwater resources has received extensive attention at home and abroad.Studying the impact of climate change on groundwater is conducive to the rational development and utilization of water resources and the effective protection of the ecological environment.This paper takes the groundwater of Anyang River alluvial fan as the research object to analyze the response of groundwater level to climate change.First,through a series of meteorological data,analyze the change characteristics of precipitation,temperature,and evaporation from three aspects:trend,periodicity,and sudden change;secondly,establish the numerical value of groundwater in the study area by constructing a hydrogeological conceptual model and corresponding mathematical models Model;use FEFLOW to establish steady-state and non-steady-state models,and identify and verify the non-steady-state models;finally,use Delta downscaling Global Climate Model(GCM)to predict future climate changes in the study area under different greenhouse gas emission scenarios Trends,and predict the changes of groundwater level under different scenarios by running the model after identification and verification.The main findings of the thesis are as follows:(1)The temperature in the study area from 1951 to 2018 showed an overall upward trend(?T=1.3 ?).From 1951 to 20108,the precipitation showed a slight downward trend,with a decline rate of 1.54 mm/10a.The Anyang River alluvial fan had relatively abundant precipitation from 1951 to 1980.After 1980,the precipitation entered a relatively dry year,and the precipitation has been relatively abundant since 2000.The precipitation changes have periodic changes on four time scales:8-12 years,15-20 years,42-48 years,and 58-62 years.The average groundwater level in the study area continued to decline,and the groundwater level in Anyang urban area declined the most.The groundwater level and precipitation changes have a good convergence.Under extreme precipitation conditions,such as the 7.19 heavy rain in 2016(24-hour maximum precipitation at Anyang Station is 413.9mm),the groundwater level has recovered significantly.The water level in the study area is about 3.20 m higher on average from August to December than from January to June.The groundwater temperature and air temperature show good consistency in inter-annual and intraannual changes.As the global temperature warms,the groundwater temperature rises accordingly,Typical well points show that the water temperature increased by 0.016?/a from 2010 to 2014.(2)On the basis of establishing the conceptual model of the study area,this paper establishes the corresponding mathematical model and uses the three-dimensional numerical model to simulate.The simulation result of the steady-state flow model shows that the average error between the simulated value and the measured value is 0.35 m,and the root mean square error is 1.63 m,less than one-tenth of the simulated head change.Using unsteady flow to compare the simulated and measured groundwater level changes of some monitoring points in the study area from 2014 to 2017,the results show that the fitting process is good,the numerical model meets the accuracy requirements,and can better describe the hydrogeological conditions of the study area.It can be used to predict the future groundwater level.(3)Global Climate Model(GCM)data show that the future temperature in the study area will continue to rise under different Representative Concentration Pathways(RCP).By 2050,under the three climate scenarios of RCP2.6,RCP4.5 and RCP8.5,the temperature will increase by about 1.74?,1.83? and 2.70? respectively compared with 2018.Under the RCP2.6,the future precipitation will change steadily,showing a slight decline.The falling water volume in the RCP4.5 and RCP8.5 scenarios generally declines,but the probability of extreme precipitation in the RCP8.5 has increased significantly and the inter-annual fluctuations have been large.The model shows that the future groundwater level will still show a downward trend under different emission scenarios.The groundwater drops in the RCP2.6 is the smallest,and the groundwater level drops significantly in the RCP4.5 and RCP8.5.Model predictions show that the groundwater level in Anyang City has a higher rate of decline in consecutive dry years,and it has recovered significantly under extreme precipitation conditions.The Anyang River alluvial fan is a complete hydrogeological unit of the Haihe River Basin,with good water supply conditions.Research shows that the study area can better respond to climate change.