Dynamic Analysis And Simulation Of Phreatic Water Level In Yangzhou City

Yangzhou is abundant in wells.According to historical records,there are 1449 wells in Yangzhou,which can be seen everywhere in front and back of houses,at the each end of streets and alleys,at bridge entrances beside trees,and by courtyards and rivers.The widely distributed underwater layer wells in the urban area of Yangzhou provide a certain guarantee for the urban emergency water supply.The relationship between groundwater and human beings is very close.Groundwater is not only an important water source,but its dynamic changes also have an important impact on maintaining ecological balance,regulating rain and flood,and maintaining geological stability.The underwater layer is the most active part of the groundwater with dynamic changes.The underwater layer in the plain area is shallow and is greatly affected by climate change and human activities.If the underwater layer continues to rise,the soil texture will change,and the ability to regulate rainwater and flood will also be weakened;However,the continuous decline of the water level in the underwater layer can cause geological problems such as underground hollow and subsidence,and also make it difficult for plants to grow.Reasonable control of urban phreatic water level is of great significance for urban sustainable development.Rational utilization of phreatic water is conducive to the realization of the "double carbon" strategic goal.Due to changes in the urban water supply system in Yangzhou,the centralized water supply in the city has now replaced the underwater layer water that was used scattered in the past.Enterprises with special requirements will grab pressurized water.There are relatively few underwater layer water users,and only some residents in the old community continue to use it as living water,so there are relatively few observational studies on underwater layer water.It has certain theoretical significance and practical value to study the dynamic characteristics of the urban underwater layer and simulate the changing process of the underwater layer.The research results can provide relevant parameters for analyzing the ability of underwater layer water supply,and lay a foundation for analyzing the impact of dynamic changes in underwater layer on maintaining ecological balance,regulating rainwater and blood,as well as maintaining geological stability.In this research,the area surrounded by the four urban rivers,such as Qinhuai River,North Moat,Erdao River and ancient canal is selected as the study area,and carries out the analysis and research by using a series of underwater layer dynamic observation data and related hydrometeorological data of the Yangzhou Branch of the Jiangsu Hydrology and Water Resources Survey Bureau,as well as the linear tendency estimation method,the Mann-Kendall test method,and the moving T-test method,to analyze the dynamic characteristics of the underwater layer level in the study area and quantitatively analyze the influence of various influencing factors on the underwater layer performance.According to the diving unsteady flow formula,this thesis constructs a underwater layer dynamic simulation model,performs parameter calibration,and simulates and calculates the changes of the underwater layer and the response of the groundwater flow field in the study area under the disturbance of human activities.The main results obtained through the research are as follow:(1)The differential integral method is used to solve the basic differential equation of phreatic unsteady flow movement when there is uniform infiltration in the inter River block,and the one-dimensional flow bushinesk equation is used to deduce the calculation formula of water level variation affected by precipitation evaporation and river water level control.(2)Through reasonable assumptions,the infiltration recharge differential equation considering the change of rainfall infiltration recharge coefficient is derived,and the rainfall infiltration recharge equation is solved according to the definite solution conditions.(3)According to the observation data,the qualitative relationship between the change of phreatic water level and rainfall and evaporation is analyzed,and a quadratic optimization algorithm is proposed.With this algorithm,the parameters are calibrated according to the calculation formula of phreatic water level change,and the quantitative relationship formula between phreatic water level change and rainfall,aviryanov formula,and the calculation formula of the relationship between the decline range of phreatic water level and the water level of phreatic observation well are obtained;Quantitative relationship formula between phreatic water level change and rainfall and phreatic depth.(4)A formula for calculating the variation amplitude of phreatic water level(equal to the variation amplitude of water depth)based on the influence of rainfall evaporation and phreatic hydraulic slope is constructed,the dynamic simulation model of phreatic water level is established,and the objective function of model parameter calibration is established.Based on the previous research results,the water yield is preliminarily calculated ??permeability coefficient k,maximum infiltration recharge rgm and infiltration recharge constant Kg were verified.The application of MODFLOW software in the dynamic change of diving in the study area is studied.