Study On The Dynamic Characteristics And Prediction Of Groundwate In Chengdu Plain

By investigating the geology and hydrogeological conditions of the Chengdu Plain,based on the dynamic monitoring data of multi-year groundwater levels in the study area,groundwater dynamics were analyzed,the type of groundwater dynamics was determined;And mathematical statistics were used to analyze the depth of water depth in the study area;Using the gray correlation analysis method to determine the main influencing factors of water depth in different watersheds;Using spectrum analysis method to analyze the periodicity and trend of the water depth of the study area;.Using Visual MODFLOW software to simulate and predict the groundwater seepage field in the study area.Through the study,the following conclusions are drawn:1.There are five major types of groundwater dynamics in the study area.The dynamic type of groundwater in the alluvial-proluvial fan section of the study area is precipitation-hydrological-impact type,and the middle-lower reaches of the piedmont alluvial fan,which is far from the river,are precipitation-influenced,the Min and Tuo River and and its tributary floodplains and some first-order regions are hydrologically influential,the groundwater exploitation area and the concentrated water extraction area are mining types,near the subway is engineering-affected type.2.Between 1985 and 2010,the water depth of the Min River basin in the Chengdu Plain averaged between 2.48 and 5.12 m.,the average water depth in the Tuo River Basin was between 3.17 and 6.78 m,the average water depth in the Xihe River Basin was between 3.14 and 4.74 m.The inter-annual dynamics of the groundwater level in the Chengdu Plain are showing a downward trend,and the water level dropped by 1.5~3.5m in 25 years.3.The influencing factors are basically the same in different watersheds.Runoff depth and agricultural irrigation have little effect on groundwater level in different watersheds.The correlation with water depth is less than or equal to 0.6.Temperature and underground mining volume play a major role in different watersheds and their correlations are all greater than 0.8.,the rainfall also has a certain impact on the water level,the correlation degree is above 0.7,in the Tuo River Basin even above 0.8.4.There is a period of one year for the groundwater level in the study area to reflect the seasonal change of groundwater and another period that reflects the variation of rainfall and surface water in the study area for five to seven years.According to the stochastic model,the groundwater level in the study area will decrease slowly mainly from 2010 to 2020,and will drop by 1~3m in 10 years.The water level will only increase in some areas of Mianzhu City,and will increase by 0.3m in 10 years.Chengdu City and Deyang City will be the largest decline,falling by 2~5m in 10 years.5.It is predicted that the groundwater levels in 2025 and 2028 will both decrease from 2005.The overall decline will be 1 to 5 meters,and the decline rate in urban areas near Chengdu and Deyang will reach 5 to 8 meters.If the groundwater in the study area continues to be mined according to the existing conditions,the groundwater level will continue to decline slowly,decrease in years between 0.1~0.2m.