Study On Aquifer System Parameters Identification Based On Channel Water Level Fluctuations

The effective assessment of regional groundwater resources and management requires precise understanding of aquifer characteristics and hydrological parameters.Hydrogeological parameters are the basis for numerical simulation of groundwater flow and solute transport simulation,and are also necessary for groundwater resource evaluation and aquifer pollution risk evaluation.There are close hydraulic connections and frequent interaction between rivers and groundwater.Diversion irrigation is an important agricultural activity in arid and semi-arid areas,and the study of groundwater movement patterns near rivers and canals is of great significance for groundwater resource evaluation,agricultural irrigation,and the construction of gates and water storage in rivers.This article takes Qingtongxia Irrigation Area in Yinchuan Plain of Ningxia as study area to integrate multiple research methods to obtain hydrogeological parameters via the field investigation,in situ test and dynamic observation,indoor physical and numerical simulation,data collection and parameter inversion.Using the natural stimulation behavior of groundwater fluctuation in the surrounding groundwater caused when the water level in the river and canal fluctuations during irrigation diversion,hydrogeological parameters are obtained through the integration of different scales and methods.Results include the followings:(1)Correlation analysis theory was applied to study the correlation between water level fluctuation and groundwater level during irrigation channel diversion,and it was found that the correlation coefficient is highly correlated,with a correlation coefficient of 0.9 or more,reflecting that the signal of water level fluctuation in the river canal can be propagated to the aquifer far away from the river canal.With the fluctuation of water level in the river and canal as the transmitter and the change of water level in the surrounding monitoring wells as the signal receiver,the fluctuation range and sequence of the signal waves reflect the heterogeneity of the aquifer in the region.(2)Based on the flood wave response model,the PEST parameter estimation software package is integrated to develop a software tool for calculating aquifer diffusivity and river resistance by applying the forward and inverse of flood wave response model,which uses the "exhaustive method" based forward model to peek at the initial values of parameters and solve the problem of local optimum of the inversion of PEST parameters.The software uses the "exhaustive method" based forward model to peek at the initial values of the parameters,which solves the problem that the inversion of the PEST parameters falls into the local optimal solution.The actual verification of the data in the study area shows that the parameters calculated by the developed tool software of flood wave theory are consistent with the actual situation in the study area,and can easily evaluate aquifer diffusivity and river resistance in the river-aquifer system.Closer distance of monitoring wells with the river brings more accurate parameters.(3)Based on the theory of river stage tomography,the diversion of irrigation water from irrigation canals in the study area can be used as a natural stimulation source to characterize the groundwater basin.On the premise that water level changes in aquifers are strongly correlated with water level changes in river canals,the river stage tomography can quantitatively estimate the spatial distribution of hydraulic parameters of large-scale aquifers in the Qingtongxia irrigation area through practical verification of data in the study area.(4)Traditional numerical simulation is one of the main methodologies to quantitatively evaluate the relationship between river and groundwater.By comparing the parameters retrieved by GMS software numerical simulation method of finite volume model with results from other methods,it shows that the hydraulic diffusion coefficient of aquifer retrieved by flood wave method is basically consistent with the parameters of numerical simulation,and the distribution of permeability coefficient obtained by numerical method and river hydraulic tomography method is also roughly consistent.(5)Numerical methods was used to analyze the seepage of the two irrigation canals and concluded that the groundwater change caused by seepage recharge of the river canal is continuous and slow,and the recharge of the Huinong canal to the surrounding groundwater is much larger than the recharge of the Hanyan canal to the groundwater,while the irrigation infiltration recharge is pulsed recharge,causing the water level to inflect instantaneously and then rise nearly vertically,and the larger the irrigation infiltration is,the more the water level rises.(6)The applicability of various methods to obtain hydrological parameters is summarized,and it is concluded that both flood wave and river stage tomography methods require the river water level change to be relatively correlated with the surrounding groundwater level change.The paper also gives suggestions on the layout of monitoring wells for obtaining hydrological parameters through channel water level changes.