A method and system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone

Abstract

The present invention relates to a method and system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, including the steps of: establishing an analytical model of groundwater flow movement including the influence of the vadose zone, and solving to obtain an analytical solution of the groundwater level in the aquifer driven by tides; collecting borehole water level monitoring data of the area to be estimated, and analyzing the water level time series in the borehole water level monitoring data to obtain groundwater level fluctuations; fitting the analytical solution of the groundwater level with the groundwater level fluctuations in the water level monitoring data, and selecting the parameter values corresponding to the fitting curve that meets the requirements; based on the Richards equation describing groundwater flow in the vadose zone, the present invention establishes a mathematical model of groundwater flow in an unsaturated-saturated coupled aquifer driven by tides, obtains analytical solutions of groundwater levels at different positions in the vadose zone and aquifer through mathematical analytical methods, and fits them with borehole observation data, which can effectively invert and estimate the hydrogeological parameters of the vadose zone and aquifer.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogeological parameter evaluation, and more specifically, to a method and system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone. Background Art

[0002] The accurate evaluation of hydrogeological parameters in the coastal zone is crucial for preventing seawater intrusion and formulating sustainable development plans for the coastal zone. To obtain these parameters, a hydrogeological parameter estimation method based on the tidal response of the groundwater level has been widely used because it is economical, effective, and more in line with the natural hydrogeological environment of the coastal zone. Compared with the traditional pumping test, this method analyzes and inverses parameters based on long-term natural water level observation data, which is not only free from human interference but also allows for long-term monitoring. Therefore, it has advantages in both economy and practicality. In addition, due to the widespread existence of ocean tides in the coastal zone, the applicable range of this method is relatively wide.

[0003] However, existing studies on the tidal response of the groundwater level are usually limited to saturated aquifers, ignoring the unsaturated vadose zone that is widespread in the coastal zone. If the influence of the vadose zone is ignored, it often leads to varying degrees of deviation in parameter estimation, thus limiting the popularization and application of the groundwater level tidal response method. To solve the above problems, a method and system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone are needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, and also provide a system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, aiming at the above-mentioned defects of the prior art.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] Construct a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, wherein the method includes the steps of:

[0007] Establish an analytical model of groundwater flow movement including the influence of the vadose zone, and solve the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer driven by tides;

[0008] Collect the borehole water level monitoring data of the hydrogeological parameters of the area to be estimated, and analyze the water level time series in the borehole water level monitoring data to obtain the groundwater level fluctuations;

[0009] Fit the analytical solution of the groundwater level with the groundwater level fluctuations in the water level monitoring data, select the parameter values corresponding to the fitting curve that meets the requirements, and use the obtained parameter values as the estimated values of the hydrogeological parameters of the vadose zone and aquifer in the area to be estimated.

[0010] The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, wherein establishing an analytical model of groundwater flow movement considering the influence of the vadose zone and solving the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal driving includes:

[0011] For the part of groundwater flow driven by tides, both the vadose zone and the semi-pervious layer are in one-dimensional vertical flow, and the confined aquifer is in two-dimensional vertical and horizontal flow;

[0012] Coupling the interface between the saturated zone and the unsaturated zone by equal head and equal flux to obtain a coupled model of the one-dimensional unsaturated zone, one-dimensional semi-pervious layer and two-dimensional confined aquifer;

[0013] Using mathematical analytical methods to solve the coupled model to obtain the analytical solution of the groundwater level at different tidal propagation positions and different depths in the aquifer under tidal driving.

[0014] The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, wherein the two-dimensional basic differential equation of groundwater flow movement in the confined aquifer and its initial and boundary conditions are described by the following control equations: In the formula is the head of the confined aquifer, is the head of the confined aquifer at the coordinate (x, y) at time t; and are the hydraulic conductivities of the confined aquifer in the x direction and the z direction respectively; is the elastic storage rate / release rate of the confined aquifer; is the distance between the river and the inland water divide; is the time-varying head at the boundary; is the thickness of the semi-pervious layer; is the thickness of the confined aquifer.

[0015] The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, wherein the one-dimensional basic differential equation of groundwater flow movement in the semi-pervious layer adopts the formula: In the formula: represents the head of the semi-pervious layer, is the hydraulic conductivity of the semi-pervious layer; is the elastic storage rate / release rate of the semi-pervious layer; is the position of the moving phreatic surface.

[0016] The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, wherein the one-dimensional Richards equation of groundwater flow movement in the unsaturated zone and its boundary conditions adopt the formula: In the formula is the total head of the vadose zone; is the relative permeability coefficient; is the volumetric water content of the soil; is the water capacity; is the pressure head of the vadose zone; is the thickness of the vadose zone.

[0017] For the method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, the control equations at the interface between the vadose zone and the semi-permeable layer and the control equations at the interface between the semi-permeable layer and the confined aquifer adopt the formula: .

[0018] For the method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, the control equations (1a), (1b), (1c), (1d), (2), (3a), (3b), (4a), (4b), (4c), (4d) are linearized so that the position of the phreatic surface is at , and the Gardner-Kozeny water characteristic curve model is applied to the Richards equation. The simplified control equation is: In the formula, and , and are respectively the zero-order approximations of the relative permeability coefficient and the water capacity at the static volumetric water content of the soil, is the soil moisture retention index, is the relative permeability coefficient index, is the specific yield, and are respectively the pressure heads at the point where air starts to enter the saturated medium and the point where the relative permeability coefficient starts to equal 1;

[0019] Based on the expression of the water level oscillation change caused by ocean tides , where is the complex amplitude, is the angular frequency, is the tidal oscillation period, , the periodic head change is transformed into the complex amplitude form: In the formula, is the complex amplitude of , is the complex amplitude of , is the complex amplitude of ;

[0020] Substitute the above complex amplitude form into the governing equations (5a), (5b), (5c), (5d), (5e), (5f), (5g), (5h), (5i), (5j), (5k) to obtain the new governing equations, expressed as, where, ;

[0021] For perform variable substitution to homogenize the boundary conditions in order to solve equation (7h) using the Fourier transform method: where, is governed by a partial differential equation with homogeneous boundary conditions. The governing equations (7a), (7b), (7c), (7d), (7e), (7f), (7g), (7h), (7i), (7j), (7k) can be written as: Based on integral transform, eliminate the term in to convert the partial differential equation into an ordinary differential equation. At the same time, to maintain the consistency of both sides of the equation, perform Fourier transforms on and , which are represented by the following integral forms: where is the kernel, is the eigenvalue, , can be expressed as: Substitute equations (9a), (9b), (9c) into equations (8a), (8b), (8c), (8d), (8e), (8f), (8g), (8h), (8i), (8j), and (8k) respectively to obtain the integral-transformed governing equations as: The general solutions of equations (11a), (11e), and (11h) are respectively: where, , , and are the first and second kind Bessel functions of order respectively;

[0022] Using equations (11b), (11c), (11d), (11f), (11g), and (11i), the expressions of , , , , and can be determined: where, the expressions of the introduced intermediate variables are: The groundwater levels at specific locations in the vadose zone, semi-permeable layer, and confined aquifer are calculated using the formula: .

[0023] For the method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, the hydrogeological parameters include water level data and time series data of boreholes; the time series obtained from monitoring is detrended to extract the tidal part, resulting in groundwater level fluctuations.

[0024] For the method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the present invention, the analytical solution of the groundwater level is fitted to the groundwater level fluctuations of the water level monitoring data, and the parameter values corresponding to the fitting curve that meets the requirements are selected. The obtained parameter values are used as the estimated values of the hydrogeological parameters of the vadose zone and aquifer at the location to be estimated, including:

[0025] Draw an image of the groundwater level of the monitoring data changing with time, and then use the analytical expression of the groundwater level to gradually adjust the various hydrogeological parameters involved for fitting until the analytical solution can fit the monitoring data. At this time, the parameter values corresponding to the analytical solution can be used to estimate the hydrogeological parameters of the vadose zone and aquifer in this area.

[0026] A system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, which is applied to the method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone as described above. The system includes: a modeling unit, a data processing unit, a data acquisition unit, and an image fitting unit;

[0027] The modeling unit is used to establish an analytical model of groundwater flow movement including the influence of the vadose zone;

[0028] The data acquisition unit is used to collect borehole water level monitoring data of the hydrogeological parameters at the location to be estimated;

[0029] The data processing unit is used to solve the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal drive, and to analyze the water level time series in the borehole water level monitoring data to obtain groundwater level fluctuations;

[0030] The image fitting unit is used to fit the analytical solution of the groundwater level to the groundwater level fluctuations of the water level monitoring data, and to select the parameter values corresponding to the fitting curve that meets the requirements; the obtained parameter values are used as the estimated values of the hydrogeological parameters of the vadose zone and aquifer at the location to be estimated.

[0031] The beneficial effects of the present invention are as follows: Based on the Richards equation describing the flow of vadose zone groundwater, the present invention establishes a mathematical model of groundwater flow in unsaturated-saturated coupled aquifers driven by tides. By means of mathematical analysis, the analytical solutions of groundwater levels at different positions in the vadose zone and the aquifer are obtained, and they are fitted with the borehole observation data, which can effectively invert and estimate the hydrogeological parameters of the vadose zone and the aquifer. This method helps to promote the further application of technologies based on the tidal response of groundwater levels in the field of hydrogeology, and provides a more accurate and reliable reference for the sustainable utilization and management of coastal zone groundwater resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will further explain the present invention in conjunction with the drawings and embodiments. The drawings in the following description are only partial embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings:

[0033] Figure 1 is a flowchart of a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to a preferred embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of unsaturated-saturated flow caused by tides in a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to a preferred embodiment of the present invention;

[0035] Figure 3 is a time series diagram of water levels in boreholes at different positions in a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to a preferred embodiment of the present invention;

[0036] Figure 4 is a best-fit match line diagram of groundwater levels at different positions in boreholes and analytical solutions in a method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to a preferred embodiment of the present invention;

[0037] Figure 5 is a block diagram of the principle of a system for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are partial embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0039] The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to the preferred embodiment of the present invention is as follows Figure 1 as shown, and also refer to Figures 2 - 4 , the method includes the steps:

[0040] S01: Establish an analytical model of groundwater flow movement including the influence of the vadose zone, and solve the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal drive;

[0041] S02: Collect the borehole water level monitoring data of the hydrogeological parameters of the area to be estimated, and analyze the water level time series in the borehole water level monitoring data to obtain the groundwater level fluctuation;

[0042] S03: Fit the analytical solution of the groundwater level with the groundwater level fluctuation of the water level monitoring data, select the parameter values corresponding to the qualified fitting curve, and use the obtained parameter values as the estimated values of the hydrogeological parameters of the vadose zone and aquifer in the area to be estimated;

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The method of the present invention is based on the tidal response of the groundwater level. Based on the existing borehole water level observation data, the tidal response of the water level at the borehole is calculated, that is, the groundwater level fluctuation - and it is fitted with the analytical expression of the groundwater level obtained from the analytical model. The optimal curve fitting method is used to determine the corresponding hydrogeological parameters of the vadose zone and aquifer, connecting the measured results with the theoretical results, and fully exploiting the information of the observation data.

[0045] 2. The present invention fully includes the influence of the vadose zone on the tidal response of the coastal zone groundwater level, making the analytical model closer to the actual situation. The derivation is rigorous, and the operation of the present invention is simple and easy to apply, and can provide more accurate estimates of the hydrogeological parameters of the vadose zone and aquifer, improving the traditional parameter estimation method.

[0046] The specific description is as follows:

[0047] Step 1. For the part of the groundwater flow driven by tides, both the vadose zone and the semi-permeable layer are vertically one-dimensional flows; the leaky confined aquifer is vertically and horizontally two-dimensional flows; for the interface between the saturated zone and the unsaturated zone, the water head equality and flux equality are used for coupling; using the mathematical analytical method, the analytical solution of the groundwater level at different tidal propagation positions and different depths in the aquifer under tidal drive is solved.

[0048] Step 2. Collect the borehole water level time series data of the hydrogeological parameters to be estimated, and preprocess the monitored time series (detrending), extract the tidal part, and obtain the groundwater level fluctuation.

[0049] Step 3. Use the analytical solution of groundwater obtained from the model to fit the groundwater level fluctuations of the corresponding data. When the optimal fitting match line appears, the hydrogeological parameters of the vadose zone and aquifer in this area can be estimated based on this.

[0050] The specific contents of Steps 1-3 are as follows:

[0051] The tidal-driven groundwater flow movement model described in Step 1 is a coupled model of a one-dimensional unsaturated zone, a one-dimensional semi-pervious layer, and a two-dimensional leaky confined aquifer (hereinafter referred to as the confined aquifer).

[0052] Furthermore, the two-dimensional basic differential equation of groundwater flow describing the flow movement of the confined aquifer in Step 1 and its initial and boundary conditions can be described by the following control equations: In the formula is the head of the confined aquifer [unit: , is the head of the confined aquifer at the coordinate (x, y) at time t; and are the hydraulic conductivities of the confined aquifer in the x-direction (horizontal direction) and z-direction (vertical direction) [unit: ; is the elastic storage rate / discharge rate of the confined aquifer [unit: ; is the distance between the river and the inland water divide [unit: L]; is the time-varying head at the boundary (i.e., the river water level) [unit: L]; is the thickness of the semi-pervious layer [unit: L]; is the thickness of the confined aquifer [unit: L].

[0053] Furthermore, similar to the leaky confined aquifer, the one-dimensional basic differential equation of groundwater flow in the semi-pervious layer in Step 1 can be written as: In the formula: represents the head of the semi-pervious layer [unit: , is the hydraulic conductivity of the semi-pervious layer [unit: ; is the elastic storage rate / discharge rate of the semi-pervious layer [unit: ; is the position of the moving water table [unit: .

[0054] Furthermore, the one-dimensional Richards equation describing the flow movement of the unsaturated zone in Step 1 and its boundary conditions are written as: In the formula is the total head of the vadose zone [unit: ; is the relative permeability [-]; is the volumetric water content of the soil [-]; is the water capacity [unit: L -1 ; is the pressure head of the vadose zone [unit: L]; is the thickness of the vadose zone [unit: L].

[0055] Furthermore, the governing equations at the interface between the vadose zone and the semi-pervious layer and at the interface between the semi-pervious layer and the confined aquifer described in step 1 are mainly written according to the equality of the water head and the flux at that location as: .

[0056] Furthermore, for the convenience of solving the analytical solution, the governing equations (1)-(4) are linearized so that the position of the water table is at and the Gardner-Kozeny water characteristic curve model is applied to the Richards equation. The simplified governing equations can be written as: where and , and are the zero-order approximations of the relative permeability and the water capacity at the static volumetric water content of the soil , is the soil moisture retention index (reflecting the water holding capacity of the soil) , is the relative permeability index (reflecting the permeability of the soil) , is the specific yield, and are the pressure heads [L] at the point where air begins to enter the saturated medium and at the point where the relative permeability begins to equal 1, respectively;

[0057] Based on the expression of the water level oscillation caused by ocean tides , where is the complex amplitude, is the angular frequency , is the tidal oscillation period , , the periodic water head change is transformed into the complex amplitude form: where is the complex amplitude of , is the complex amplitude of , is the Complex amplitude;

[0058] Substitute the above complex amplitude form into the governing equations (5a), (5b), (5c), (5d), (5e), (5f), (5g), (5h), (5i), (5j), (5k) to obtain new governing equations, expressed as where ;

[0059] For perform a variable substitution to homogenize the boundary conditions in order to solve equation (7h) using the Fourier transform method: where is governed by a partial differential equation with homogeneous boundary conditions, and the governing equations (7a), (7b), (7c), (7d), (7e), (7f), (7g), (7h), (7i), (7j), (7k) can be written as: Based on integral transform, eliminate the term so that the partial differential equation is converted into an ordinary differential equation. At the same time, to maintain the consistency of both sides of the equation, perform Fourier transforms on and which are represented in the following integral form: where is the kernel, is the eigenvalue, , can be expressed as: Substitute equations (9a), (9b), (9c) into equations (8a), (8b), (8c), (8d), (8e), (8f), (8g), (8h), (8i), (8j) and (8k) respectively to obtain the integral-transformed governing equations as: The general solutions of equations (11a), (11e) and (11h) are respectively: where , , and are the th order Bessel functions of the first and second kind respectively;

[0060] Using equations (11b), (11c), (11d), (11f), (11g) and (11i), the expressions of , , , , and can be determined: In the formula, the introduced intermediate variable expressions are as follows: The groundwater levels at specific positions in the vadose zone, semi-pervious layer, and confined aquifer are calculated using the formula: . Further, the hydrogeological data in step 2 includes the water level data of boreholes and time series data with a sufficiently long observation time. The data is detrended and the tidal part is extracted.

[0061] Further, draw the graph of the groundwater level of the monitoring data changing with time, and then use the analytical expression of the groundwater level in step 1 to gradually adjust the hydrogeological parameters involved for fitting until the analytical solution can better fit the monitoring data. At this time, the parameter values corresponding to the analytical solution can be used to estimate the hydrogeological parameters of the vadose zone and aquifer in this area.

[0062] Combined with Figures 2 - 4 The description is as follows:

[0063] Such as Figure 2 As shown, in the present invention, a non-saturated - saturated coupled leakage aquifer groundwater flow model driven by tides is established. The left boundary of the analytical model is a constant head boundary (tidal water level boundary), the right boundary is an impermeable boundary, with a distance of L between the left and right. The interface between the vadose zone and the saturated zone is the water table, located at the origin , and the top of the vadose zone is impermeable.

[0064] The above steps are explained below with a specific simulation example of borehole water level data.

[0065] Such as Figure 3 As shown, this embodiment applies the continuous monitoring data of the water levels of boreholes at different positions for 6 days, with a resolution of 15 minutes. Figure 3 It is the time series change diagram of 3 boreholes.

[0066] Such as Figure 4 As shown, using the same set of parameters, the analytical expression of the groundwater level and the monitoring data are compared and matched at the same time. When the optimal matching combination appears, the estimated values of the hydrogeological parameters are determined as: , , , , , , , , .

[0067] In addition, due to the difficulty in obtaining hydrogeological data, the water level simulation data selected in this method is only used for illustrative purposes and is not used for limitation.

[0068] A vadose zone and aquifer hydrogeological parameter estimation system for the coastal zone, which is applied to the vadose zone and aquifer hydrogeological parameter estimation method as described above, such as Figure 5 As shown, the system includes: a modeling unit 100, a data processing unit 101, a data acquisition unit 102, and an image fitting unit 103;

[0069] The modeling unit 100 is used to establish an analytical model of groundwater flow movement including the influence of the vadose zone;

[0070] The data acquisition unit 102 is used to collect borehole water level monitoring data of the hydrogeological parameters of the area to be estimated;

[0071] The data processing unit 101 is used to solve the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal drive, and to analyze the water level time series in the borehole water level monitoring data to obtain the groundwater level fluctuation;

[0072] The image fitting unit 103 is used to fit the analytical solution of the groundwater level with the groundwater level fluctuation of the water level monitoring data, and select the parameter values corresponding to the fitting curve that meets the requirements; the obtained parameter values are used as the estimated values of the hydrogeological parameters of the vadose zone and aquifer of the area to be estimated;

[0073] Based on the Richards equation describing the groundwater flow in the vadose zone, the present invention establishes a mathematical model of groundwater flow in an unsaturated-saturated coupled aquifer under tidal drive, obtains the analytical solutions of the groundwater levels at different positions in the vadose zone and aquifer through mathematical analysis methods, and fits them with the borehole observation data, which can effectively invert and estimate the hydrogeological parameters of the vadose zone and aquifer. This method helps to promote the further application of technologies based on the tidal response of groundwater levels in the field of hydrogeology, and provides a more accurate and reliable reference basis for the sustainable utilization and management of coastal groundwater resources.

[0074] It should be understood that for those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone, characterized in that, The method includes the steps of: Establishing an analytical model of groundwater flow movement considering the influence of the vadose zone, and solving the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal driving; Collecting the borehole water level monitoring data of the hydrogeological parameters of the area to be estimated, and analyzing the water level time series in the borehole water level monitoring data to obtain the groundwater level fluctuation; Fitting the analytical solution of the groundwater level with the groundwater level fluctuation of the borehole water level monitoring data, selecting the parameter values corresponding to the fitting curve that meets the requirements, and taking the obtained parameter values as the estimated values of the hydrogeological parameters of the vadose zone and the aquifer in the area to be estimated; The establishment of an analytical model of groundwater flow movement considering the influence of the vadose zone, and solving the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal driving includes: Under tidal driving, both the vadose zone and the semi-permeable layer are one-dimensional vertical groundwater flows, and the confined aquifer is a two-dimensional vertical and horizontal groundwater flow; Coupling the interface between the saturated zone and the unsaturated zone by equal head and equal flux to obtain a coupled model of the one-dimensional unsaturated zone, the one-dimensional semi-permeable layer and the two-dimensional confined aquifer; Using mathematical analytical methods to solve the coupled model to obtain the analytical solution of the groundwater level at different tidal propagation positions and different depths in the aquifer under tidal driving, specifically including: The basic differential equations of two-dimensional groundwater flow in the confined aquifer and its initial and boundary conditions are described by the following control equations: In the formula, is the piezometric head of the confined aquifer, is the piezometric head of the confined aquifer at the coordinate (x, z) at time t; and are the hydraulic conductivities of the confined aquifer in the x - direction and z - direction respectively; is the elastic storage rate or specific yield of the confined aquifer; is the distance between the river and the inland water divide; is the time - varying head at the boundary; is the thickness of the semi - permeable layer; is the thickness of the confined aquifer; The basic differential equation of one-dimensional groundwater flow in the semi-permeable layer is expressed by the formula: In the formula: represents the water head of the semi-pervious layer, is the permeability coefficient of the semi-pervious layer; is the elastic water storage rate or water release rate of the semi-pervious layer; is the position of the moving phreatic surface; One-dimensional Richards equation for water flow in the unsaturated zone and its boundary conditions Adopt the formula: where is the total head of the vadose zone; is the relative permeability; is the volumetric water content of the soil; is the specific yield; is the pressure head of the vadose zone; is the thickness of the vadose zone; The control equations at the interface between the vadose zone and the semi-permeable layer and the control equations at the interface between the semi-permeable layer and the confined aquifer are expressed by the formula: ； Linearize the governing equations (1a), (1b), (1c), (1d), (2), (3a), (3b), (4a), (4b), (4c), (4d) such that the position of the water table is at and use the Gardner-Kozeny water characteristic curve model to simplify the Richards equation. The simplified governing equations are: In the formula, and , and are the zero-order approximations of the relative permeability coefficient and the water capacity at the initial soil volumetric water content . is the soil moisture conservation index, is the relative permeability coefficient index, is the specific yield, , and are the pressure heads at the points where air starts to enter the saturated medium and where the relative permeability coefficient starts to equal 1, respectively; Expression for the change in water level oscillation caused by ocean tides , where is the complex amplitude, is the angular frequency, is the tidal oscillation period, , converting the periodic head change to the complex amplitude form: In the formula, is 's complex amplitude, is 's complex amplitude, is 's complex amplitude; Substituting the above complex amplitude forms into the control equations (5a), (5b), (5c), (5d), (5e), (5f), (5g), (5h), (5i), (5j), (5k), a new control equation is obtained, expressed as: wherein, ; perform variable substitution on to homogenize the boundary conditions so as to solve equation (7h) by using the Fourier transform method: Among them, It is controlled by a partial differential equation with homogeneous boundary conditions. The governing equations (7a), (7b), (7c), (7d), (7e), (7f), (7g), (7h), (7i), (7j), (7k) are written as: Based on integral transformation, Eliminate terms, so that the partial differential equation is transformed into an ordinary differential equation, and and are subjected to Fourier transformation and expressed in the following integral form: In the formula is the core, is the eigenvalue, , , , is expressed as: Substituting equations (9a), (9b), (9c) into equations (8a), (8b), (8c), (8d), (8e), (8f), (8g), (8h), (8i), (8j) and (8k) respectively, the control equation after integral transformation is: The general solutions of equations (11a), (11e) and (11h) are respectively: In the formula, , , , , , and are respectively order first and second kind Bessel functions; Using equations (11b), (11c), (11d), (11f), (11g) and (11i), the expressions of , , , , and can be determined: In the formula, the expressions of each introduced intermediate variable are: The groundwater level at a specific position in the vadose zone, the semi-permeable layer and the confined aquifer is expressed by the formula: 。 2. The method for estimating hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to claim 1, characterized in that, The hydrogeological parameters include the water level data and time series data of the borehole; the detrending process is performed on the monitored time series data to extract the tidal part to obtain the groundwater level fluctuation.

3. The method for estimating the hydrogeological parameters of the vadose zone and aquifer in the coastal zone according to claim 1, wherein Fitting the analytical solution of the groundwater level with the groundwater level fluctuation of the borehole water level monitoring data, selecting the parameter values corresponding to the fitting curve that meets the requirements, and taking the obtained parameter values as the estimated values of the hydrogeological parameters of the vadose zone and the aquifer in the area to be estimated includes: Draw the image of the variation of the groundwater level with time of the borehole water level monitoring data, and then use the analytical expression of the groundwater level to gradually adjust each hydrogeological parameter for fitting until the analytical solution can fit the borehole water level monitoring data. At this time, the parameter values corresponding to the analytical solution are used to estimate the hydrogeological parameters of the vadose zone and aquifer of the area to be estimated.

4. A vadose zone and aquifer hydrogeological parameter estimation system for the coastal zone, which is applied to the vadose zone and aquifer hydrogeological parameter estimation method as described in any one of claims 1-3, and is characterized in that The system includes: a modeling unit, a data processing unit, a data acquisition unit, and an image fitting unit; The modeling unit is used to establish an analytical model of groundwater flow movement including the influence of the vadose zone; The data acquisition unit is used to collect the borehole water level monitoring data of the hydrogeological parameters of the area to be estimated; The data processing unit is used to solve the analytical model of groundwater flow movement to obtain the analytical solution of the groundwater level in the aquifer under tidal drive, and to analyze the water level time series in the borehole water level monitoring data to obtain the groundwater level fluctuation; The image fitting unit is used to fit the analytical solution of the groundwater level with the groundwater level fluctuation of the borehole water level monitoring data, and select the parameter values corresponding to the fitting curve that meets the requirements; the obtained parameter values are used as the estimated values of the hydrogeological parameters of the vadose zone and aquifer of the area to be estimated.

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