Underground water three-dimensional grid model construction method for regional underground water level research

Abstract

The invention relates to the technical field of underground water mathematical model construction, in particular to an underground water three-dimensional grid model construction method for regional underground water level research, which comprises the following steps: establishing a hydrogeological conceptual model, selecting a model region, conceptualizing an aquifer structure and conceptualizing boundary conditions; establishing an underground water flow mathematical model, abstracting the hydrogeological conceptual model into a mathematical simulation model, and obtaining an underground water three-dimensional unstable flow control equation; establishing a groundwater flow numerical model, and solving the groundwater three-dimensional unstable flow control equation by using a finite difference method to obtain a finite difference format of the groundwater three-dimensional unstable flow control equation; and displaying a three-dimensional grid model of underground water flow by utilizing underground water numerical simulation software GMS. The method aims at improving the precision of model numerical values under the conditions of wide regional area, different geological structures and complex geological structures.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater mathematical model construction, and in particular to a groundwater three-dimensional grid model construction method for regional groundwater level research. Background Art

[0002] The groundwater mathematical model is a mathematical structure that represents a practical problem, which is composed of a mathematical equation describing the movement of groundwater flow in a certain research area and its boundary conditions. It consists of two parts: the control equation and the boundary conditions. That is, starting from the physical model, a set of mathematical expressions is used to describe its quantitative relationship and spatial form, thereby reflecting the geological, hydrogeological conditions and basic characteristics of groundwater movement of the studied geological body, and achieving the purpose of replicating or reproducing the basic state of an actual water flow system.

[0003] The mathematical model of groundwater is to describe the migration process of saturated groundwater flow in porous media by partial differential equations based on the structural characteristics, recharge and drainage, dynamic laws, various source and sink elements of the groundwater system. Its establishment first requires generalizing the complex hydrogeological conditions into a hydrogeological conceptual model, and then abstracting the conceptual model into a mathematical simulation model. The mathematical simulation model can not only quantitatively characterize the relationship between variables and parameters in the groundwater system, but also provide model values ​​for the water level and changes of the groundwater system. These numerical models can be used to construct and simulate the entire model, providing a basis for the impact of regional underground engineering construction on groundwater levels. When constructing a regional groundwater model, due to the wide area of ​​the region, different geological structures and complex geological structures, there is a certain degree of accuracy deviation in the numerical values ​​of the model construction. As for this accuracy problem, it is still a crucial and constantly improving problem in exploration. How to improve the calculation accuracy of the model is the key problem to be solved in this application. Summary of the invention

[0004] The present invention provides a method for constructing a three-dimensional groundwater grid model for regional groundwater level research, so as to solve the problem of how to improve the accuracy of model values ​​in the case of a wide regional area, different geological structures and complex geological structures.

[0005] The method for constructing a groundwater three-dimensional grid model for regional groundwater level research of the present invention adopts the following technical solutions: An embodiment of the present invention provides a method for constructing a groundwater three-dimensional grid model for regional groundwater level research, the method comprising the following steps: Develop a hydrogeological conceptual model, select the model area, conceptualize the aquifer structure, and conceptualize the boundary conditions; Establish a mathematical model of groundwater flow, abstract the hydrogeological conceptual model into a mathematical simulation model, and obtain the three-dimensional unsteady flow control equation of groundwater; A groundwater flow numerical model is established, and the finite difference method is used to solve the three-dimensional unsteady flow control equation of groundwater, and the finite difference format of the three-dimensional unsteady flow control equation of groundwater is obtained; The three-dimensional grid model of groundwater flow is displayed using the groundwater numerical simulation software GMS.

[0006] Furthermore, the hydrogeological conceptual model is established, the model area is selected, the aquifer structure is conceptualized, and the boundary conditions are conceptualized; Based on the hydrogeological survey data and the regional geological structure, the karst landform was selected as the research object. In the model area, carbonate rocks are widely distributed, karst is strongly developed, and karst landforms account for more than 90% of the total area, with the watershed of the model area as the boundary; In the conceptualization of aquifer structure, there is no obvious stable barrier between adjacent aquifers, and they are unified as a single unconfined aquifer in the model area; Conceptualize the boundary conditions according to the location of aquifers and impermeable layers, geological structures, groundwater flow characteristics on the boundaries, and the hydraulic connection between groundwater and surface water; generalize the lateral boundary conditions of the model area into the first-class boundary for a given groundwater level, the second-class boundary for a given lateral runoff, or the third-class boundary for a given flow and water level relationship; generalize the vertical boundary conditions into boundary conditions with water exchange and boundary conditions without water exchange; the model area is based on the surface watershed as the regional boundary, which is generalized as a water-impermeable boundary with zero flow; the lowest point in the southeast direction is the regional discharge point, which is generalized as the first-class head boundary; the top is the regional surface, which is the recharge area of ​​atmospheric precipitation, which is generalized as the recharge boundary, and the bottom of the model area is less affected by groundwater, so it is generalized as a water-impermeable boundary.

[0007] Furthermore, the hydrogeological conceptual model is abstracted into a mathematical simulation model: Assuming that the groundwater flow obeys Darcy's law and the principal value of the permeability coefficient is consistent with the direction of the coordinate axis, the three-dimensional unsteady flow control equation of groundwater can be expressed as: ; Where: H —groundwater head (m); K xx , K yy , K zz —x, y, z direction permeability (m / d); —Water supply of aquifer or specific water storage coefficient; gravity water supply of phreatic layer μ d , the specific elastic water release (water storage) coefficient of the confined aquifer is selected ; —initial water head of aquifer (m); H 1—Boundary water level of each layer (m); —Recharge flow rate per unit area of ​​the second-class boundary of the aquifer (m / d); 1—Intensity of source and sink items (including mining intensity) (m / d); —seepage area; B1—is the boundary with known hydraulic head, the first type of boundary; B2—is the boundary with known flow, the second type of boundary; —Direction of the unit external normal to the boundary of the vadose zone.

[0008] Furthermore, the finite difference method is used to solve the three-dimensional unsteady flow control equation of groundwater to obtain the finite difference format of the three-dimensional unsteady flow control equation of groundwater: Divide the solution domain into a differential grid; The continuous solution domain is replaced by a finite number of grid nodes, and the derivatives of the variables are written in the form of functions according to the Taylor series expansion. The derivatives in the control equations are discretized by replacing them with the difference quotients of the function values ​​at the grid nodes, and a set of algebraic equations with the values ​​at the grid nodes as unknowns is established.

[0009] Furthermore, the finite difference format of the three-dimensional unsteady flow control equation of groundwater is expressed as: ; Where: H —aquifer head (m), the superscript is the time and the subscript is the unit cell, e.g. represents the water head value of cell (i,j,k) at time n+1; , , , , , —Hydraulic conductivity in x, y, z directions (m / d), where: ; ; ; ; ; ; ; ;

[0010] Δx, Δy, and Δz represent the step size of the aquifer spatial grid along the x, y, and z directions. represents the permeability coefficient between the cell (Δx, Δy, Δz) and the cell (Δx, Δy+1, Δz) .

[0011] Furthermore, the establishment of the groundwater flow numerical model also includes partitioning the model according to the infiltration coefficient α according to the geological conditions, first obtaining the amount of atmospheric precipitation recharging groundwater corresponding to the partition number, and then obtaining the amount of atmospheric precipitation recharging groundwater for the entire model.

[0012] Furthermore, the infiltration coefficient α is specifically solved as follows: The dynamic analysis method is used to measure the groundwater level rise Δh after precipitation using a groundwater self-recording water level gauge. The product of Δh and the water value μ brought by the water level change is equal to the precipitation infiltration recharge, expressed as: Pr=μΔh. Dividing it by the precipitation in the same period gives the α value.

[0013] Furthermore, the amount of groundwater recharged by atmospheric precipitation corresponding to the partition number is specifically: Since the effective recharge of groundwater aquifer is closely related to the infiltration coefficient, the formula of infiltration coefficient is expressed as: α = Pr / P; Where P is the precipitation in a certain period, Pr is the effective recharge of groundwater through infiltration, and α is the infiltration coefficient.

[0014] Furthermore, the amount of groundwater recharged by atmospheric precipitation in the entire model is specifically: The amount of atmospheric precipitation recharging groundwater in the same partition number is summed up and the average value is calculated, and then the average values ​​obtained in different partition numbers are added together.

[0015] Furthermore, the permeability coefficient , considering the single-hole diving incomplete well in groundwater dynamics, the permeability coefficient It is expressed as: ; ; Where: K is the permeability coefficient (m / d); Q is the water inflow (m³ / d); S is the water level drawdown (m); H is the static water level or aquifer thickness (m); R is the influence radius (m); r is the pumping hole radius (m).

[0016] The beneficial effects of the technical solution of the present invention are as follows: first, complex hydrogeological conditions are generalized into a hydrogeological conceptual model, and then the conceptual model is abstracted into a mathematical simulation model, wherein the mathematical simulation model can not only quantitatively characterize the relationship between variables and parameters in the groundwater system, but also evaluate the behavior and function of the groundwater system, and provide a basis for complex and diverse regional groundwater level research; and a finite difference method is used to divide the solution domain into differential grids, and then a finite number of grid nodes are used to replace the continuous solution domain, and the derivatives of the variables are written into a function form according to the Taylor series expansion, and then the derivatives in the control equation are replaced by the difference quotient of the function value of the grid node for discretization, and an algebraic equation group with the values ​​on the grid nodes as unknown numbers is established, and a numerical model involving more parameters is established to improve the calculation accuracy; and the model is partitioned and numbered according to the infiltration coefficient α, and the amount of atmospheric precipitation replenishing groundwater corresponding to the partition number is first obtained, and then the amount of atmospheric precipitation replenishing groundwater of the entire model is obtained, while improving the calculation accuracy, the work intensity is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention is a flowchart of the steps of the method for constructing a three-dimensional groundwater grid model for regional groundwater level research.

[0019] Figure 2 The present invention is a flowchart of the steps of establishing a groundwater flow numerical model in the method for constructing a three-dimensional groundwater grid model for regional groundwater level research.

[0020] Figure 3 Schematic diagram of the research area in the embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the boundary conditions of the research area in an embodiment of the present invention.

[0022] Figure 5 It is a three-dimensional graph of the model grid in an embodiment of the present invention.

[0023] Figure 6 It is a plan view of the model mesh division in an embodiment of the present invention.

[0024] Figure 7 It is a schematic diagram of rainfall infiltration coefficient zoning in an embodiment of the present invention.

[0025] Figure 8Schematic diagram of the infiltration coefficient value in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the method for constructing a three-dimensional groundwater grid model for regional groundwater level research proposed by the present invention, its specific implementation method, structure, features and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0027] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0028] The specific scheme of the method for constructing a three-dimensional groundwater grid model for regional groundwater level research provided by the present invention is described in detail below with reference to the accompanying drawings.

[0029] See also Figure 1 , which shows a flowchart of the steps of a method for constructing a groundwater three-dimensional grid model for regional groundwater level research provided by an embodiment of the present invention, the method comprising the following steps: A method for constructing a three-dimensional groundwater grid model for regional groundwater level research includes the following steps: Step S100: Establishing a hydrogeological conceptual model, selecting a model area, conceptualizing the aquifer structure, and conceptualizing the boundary conditions; (1) Based on the hydrogeological survey data and the regional geological structure, karst landforms were selected as the research objects. Carbonate rocks are widely distributed in the model area, karst is strongly developed, and karst landforms account for more than 90% of the total area. The watershed of the model area is the boundary.

[0030] In this example, a typical hydrogeological unit (i.e., the Yangguan to Sanqiao karst spring system) was selected as the research object. Figure 3 Shown is a schematic diagram of the study area, with a total simulated area of ​​23.46 km².

[0031] (2) In the conceptualization of aquifer structure, there is no obvious stable impermeable layer between adjacent aquifers, and they are uniformly generalized as a single unconfined aquifer in the model area.

[0032] The terrain of the study area is high in the northwest and low in the southeast, with a relative height difference of 100m-200m. The ridge altitude is between 1200-1400m. The highest point is in the northeast, with an elevation of about 1345m, and the lowest point is in the southeast, with an elevation of 1115m, with a relative height difference of 230m. The groundwater aquifer is recharged by atmospheric precipitation. Under the control of the terrain, it flows and discharges from the north to the south and then to the east. Groundwater is mainly recharged by atmospheric precipitation. The karst pipelines in the area are poorly developed, and the Mesozoic Triassic strata are exposed. The lithology is mainly limestone, dolomite, and calcareous claystone. The lithology of the aquifers is as follows: Triassic Gaicha Formation T 2-3 g, Triassic Yangliujing Formation T2y, Triassic Guanling Formation T2g, Triassic Anshun Formation T 1-2 a. Triassic Daye Formation T1d. The Gaicha Formation is composed of variegated claystone, sandstone and gray medium-thick to thick limestone and dolomite; the Yangliujing Formation is composed of light gray and gray medium-thick to massive dolomite, brecciated dolomite and top limestone; the Guanling Formation is composed of gray and dark gray medium-thick limestone intercalated with marl and a small amount of dolomite; the Anshun Formation is mainly composed of light gray-dark gray thin to thick micrite limestone and dolomite, with mostly dissolved brecciated dolomite at the top; the Daye Formation is light gray, gray thin-layered laminated and medium-thick micrite limestone, muddy limestone, intercalated with shale, marl and gravelly limestone. The groundwater type is mainly carbonate karst water. The water-bearing media of Yangliujing Formation, Guanling Formation and Anshun Formation are dolomite pores and cracks, and the groundwater distribution is relatively uniform, with medium water richness. The water-bearing media of Gaicha Formation and Daye Formation are limestone caves, pipes and cracks, and the groundwater distribution is uneven, with medium to strong water richness. There is no obvious stable impermeable layer between adjacent aquifers, so they are uniformly generalized as a single phreatic aquifer in the model.

[0033] (3) Conceptualization of boundary conditions. The generalization of boundary conditions is a relatively complex but very important issue in establishing a hydrogeological conceptual model. The correctness of boundary condition treatment is directly related to the accuracy of the description of groundwater seepage field and the prediction of water resources in the spring area. According to the location of aquifers and impermeable layers, geological structures, groundwater flow characteristics on the boundaries, and the hydraulic connection between groundwater and surface water; the lateral boundary conditions of the model area are generalized as the first-class boundary for a given groundwater level, the second-class boundary for a given lateral runoff, or the third-class boundary for a given flow and water level relationship; the vertical boundary conditions are generalized into boundary conditions with water exchange and boundary conditions without water exchange; the model area is based on the surface watershed as the regional boundary, which is generalized as a water-impermeable boundary with zero flow; the lowest point in the southeast direction is the regional discharge point, which is generalized as the first-class head boundary; the top is the regional surface, which is the recharge area of ​​atmospheric precipitation, which is generalized as the recharge boundary. The bottom of the model area is less affected by groundwater, and the bottom of the model area is generalized as a water-impermeable boundary, such as Figure 4 Shown is a schematic diagram of the boundary conditions of the study area.

[0034] Step S200: Establishing a groundwater flow mathematical model, abstracting the hydrogeological conceptual model into a mathematical simulation model, and obtaining a three-dimensional groundwater unsteady flow control equation; The groundwater mathematical model is a mathematical structure that represents a practical problem, which is composed of a mathematical equation describing the movement of groundwater flow in a certain area and its boundary conditions. It consists of two parts: the control equation and the boundary conditions. That is, starting from the physical model, a set of mathematical expressions is used to describe its quantitative relationship and spatial form, thereby reflecting the geological, hydrogeological conditions and basic characteristics of groundwater movement of the geological body under study, and achieving the purpose of replicating or reproducing the basic state of an actual water flow system.

[0035] The groundwater mathematical model describes the migration process of saturated groundwater in porous media by using partial differential equations based on the structural characteristics, recharge, drainage and dynamic laws of the groundwater system, various source and sink elements, etc. Its establishment first requires generalizing the complex hydrogeological conditions into a hydrogeological conceptual model, and then abstracting the conceptual model into a mathematical simulation model. The mathematical simulation model can not only quantitatively characterize the relationship between variables and parameters in the groundwater system, but also evaluate the behavior and function of the groundwater system after identification and verification.

[0036] Assuming that the groundwater flow obeys Darcy's law and the principal value of the permeability coefficient is consistent with the direction of the coordinate axis, the three-dimensional unsteady flow control equation of groundwater can be expressed as: ; Where: H —groundwater head (m); K xx , K yy , K zz —x, y, z direction permeability (m / d); —Water supply of aquifer or specific water storage coefficient; gravity water supply of phreatic layer μ d , the specific elastic water release (water storage) coefficient of the confined aquifer is selected ; —initial water head of aquifer (m); H 1—Boundary water level of each layer (m); —Recharge flow rate per unit area of ​​the second-class boundary of the aquifer (m / d); 1—Intensity of source and sink items (including mining intensity) (m / d); —seepage area; B1—is the boundary with known hydraulic head, the first type of boundary; B2—is the boundary with known flow, the second type of boundary; —Direction of the unit external normal to the boundary of the vadose zone.

[0037] Step S300: Establish a groundwater flow numerical model, use the finite difference method to solve the three-dimensional unsteady flow control equation of groundwater, and obtain the finite difference format of the three-dimensional unsteady flow control equation of groundwater. Figure 2 Shown is a flow chart for establishing a numerical groundwater flow model.

[0038] Step S301: Divide the solution domain into differential grids; After the regional groundwater mathematical model is established, the seepage zone needs to be discretized (divided). The grid size of the model determines its hydraulic characteristics and stress change capability. If the grid size is too large, the characteristics of the groundwater system may be missed. In order to ensure that the undulating terrain of the study area is portrayed, the study area is divided relatively densely.

[0039] In this embodiment, the model area is 4612m long from east to west and 11974m long from north to south. The horizontal coordinate range is 663442~668054m under the UTM48N projection coordinates; the vertical coordinate range is 2938758~2950732m. The surface elevation of the model is generated by interpolation of digital elevation data (DEM), and the overall bottom elevation is 1110~1360m. The model base is set at 300m above the surface elevation.

[0040] Step S302: using a finite number of grid nodes to replace the continuous solution domain, and writing the derivative of the variable into a function form according to the Taylor series expansion.

[0041] In this embodiment, the finite difference method is used to divide the solution domain into difference grids, and then a finite number of grid nodes are used to replace the continuous solution domain, and the derivatives of the variables are written in function form according to the Taylor series expansion.

[0042] The finite difference format of the governing equations for three-dimensional unsteady groundwater flow is expressed as: '' Where: H —aquifer head (m), the superscript is the time and the subscript is the unit cell, e.g. represents the water head value of cell (i,j,k) at time n+1; , , , , , —Hydraulic conductivity coefficient in x, y, and z directions (m / d).

[0043] Step S303: The derivatives in the control equation are replaced by the difference quotients of the function values ​​of the grid nodes for discretization, and an algebraic equation system is established with the values ​​on the grid nodes as unknown numbers: in: ; ; ; ; ; ； ； ; Δx, Δy, and Δz represent the step size of the aquifer spatial grid along the x, y, and z directions. represents the permeability coefficient between the cell (Δx, Δy, Δz) and the cell (Δx, Δy+1, Δz) .

[0044] In this embodiment, the model area is discretized and divided into 47 columns along the east-west direction with a grid spacing of 100m, and 120 rows along the north-south direction with a grid spacing of 100m. It is divided into 3 layers vertically with a maximum layer thickness of 200m. Through the above division, a total of 16,920 units are divided. According to the setting of the boundary conditions of the hydrogeological conceptual model, the parts outside the boundary are set as inactive units, so 7,170 valid calculation units and 9,750 invalid calculation units are obtained. The three-dimensional diagram of the model grid is shown in the figure below: Figure 5 The model meshing plan is shown as Figure 6 shown.

[0045] The permeability coefficient involved in this application , considering the single-hole diving incomplete well in groundwater dynamics, the permeability coefficient It is expressed as: ; ; Where: K is the permeability coefficient (m / d); Q is the water inflow (m³ / d); S is the water level drawdown (m); H is the static water level or aquifer thickness (m); R is the influence radius (m); r is the pumping hole radius (m).

[0046] Step S400: using the groundwater numerical simulation software GMS to display the three-dimensional grid model of groundwater flow.

[0047] In this embodiment, the groundwater numerical simulation software GMS (Groundwater Modeling System) is used to establish a three-dimensional geological model and a three-dimensional groundwater flow model of the Yangguan to Sanqiao karst spring system in the model area.

[0048] The establishment of a numerical groundwater flow model in the present application also includes partitioning the model according to the infiltration coefficient α according to the geological conditions, first obtaining the amount of atmospheric precipitation recharging groundwater corresponding to the partition number, and then obtaining the amount of atmospheric precipitation recharging groundwater for the entire model.

[0049] Considering that the karst water in the study area is mainly recharged by atmospheric precipitation, the intensity of recharge is closely related to the topography and the degree of karst development. Since the rainfall in the model area is the same, but the rainfall mainly recharges the aquifer through surface infiltration, the effective recharge obtained by the aquifer is closely related to the infiltration coefficient. The infiltration coefficient represents the recharge intensity, which measures the ability of surface water to be converted into groundwater. It is a comprehensive expression of the surface karst negative shape and geomorphic conditions. Therefore, based on the comprehensive consideration of the topography and karst development degree of the model area, the model is divided into areas with different recharge intensities. The rainfall infiltration coefficient divisions are as follows: Figure 7 As shown in Figure 8 shown.

[0050] In this embodiment, the amount of groundwater recharged by atmospheric precipitation corresponding to the partition number is specifically: Since the effective recharge of groundwater aquifer is closely related to the infiltration coefficient, the formula of infiltration coefficient is expressed as: α = Pr / P; Where P is the precipitation in a certain period, Pr is the effective recharge of groundwater through infiltration, and α is the infiltration coefficient.

[0051] The amount of atmospheric precipitation recharging groundwater in the entire model is: In this embodiment, the amount of atmospheric precipitation recharging groundwater with the same partition number is summed and then the average value is calculated, and then the average values ​​calculated with different partition numbers are added.

[0052] This is the end of the present invention.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a three-dimensional groundwater grid model for regional groundwater level research, characterized in that: The method comprises the following steps: Develop a hydrogeological conceptual model, select the model area, conceptualize the aquifer structure, and conceptualize the boundary conditions; Establish a mathematical model of groundwater flow, abstract the hydrogeological conceptual model into a mathematical simulation model, and obtain the three-dimensional unsteady flow control equation of groundwater; A groundwater flow numerical model is established, and the finite difference method is used to solve the three-dimensional unsteady flow control equation of groundwater, and the finite difference format of the three-dimensional unsteady flow control equation of groundwater is obtained; Specifically: divide the solution domain into differential grids; The continuous solution domain is replaced by a finite number of grid nodes, and the derivatives of the variables are written in the form of functions according to the Taylor series expansion. The derivatives in the control equations are replaced by the difference quotients of the function values ​​of the grid nodes for discretization, and a set of algebraic equations with the values ​​at the grid nodes as unknowns is established; The three-dimensional grid model of groundwater flow is displayed using the groundwater numerical simulation software GMS.

2. The method for constructing a groundwater three-dimensional grid model for regional groundwater level research according to claim 1, characterized in that: The aforementioned establishment of a hydrogeological conceptual model, selection of a model area, conceptualization of aquifer structure and conceptualization of boundary conditions; Based on the hydrogeological survey data and the regional geological structure, the karst landform was selected as the research object. In the model area, carbonate rocks are widely distributed, karst is strongly developed, and karst landforms account for more than 90% of the total area, with the watershed of the model area as the boundary; In the conceptualization of aquifer structure, there is no obvious stable barrier between adjacent aquifers, and they are unified as a single unconfined aquifer in the model area; Conceptualize the boundary conditions according to the location of aquifers and impermeable layers, geological structures, groundwater flow characteristics on the boundaries, and the hydraulic connection between groundwater and surface water; generalize the lateral boundary conditions of the model area into the first-class boundary for a given groundwater level, the second-class boundary for a given lateral runoff, or the third-class boundary for a given flow and water level relationship; generalize the vertical boundary conditions into boundary conditions with water exchange and boundary conditions without water exchange; the model area is based on the surface watershed as the regional boundary, which is generalized as a water-impermeable boundary with zero flow; the lowest point in the southeast direction is the regional discharge point, which is generalized as the first-class head boundary; the top is the regional surface, which is the recharge area of ​​atmospheric precipitation, which is generalized as the recharge boundary, and the bottom of the model area is less affected by groundwater, so it is generalized as a water-impermeable boundary.

3. The method for constructing a groundwater three-dimensional grid model for regional groundwater level research according to claim 1, characterized in that: The hydrogeological conceptual model is abstracted into a mathematical simulation model: Assuming that the groundwater flow obeys Darcy's law and the principal value of the permeability coefficient is consistent with the direction of the coordinate axis, the three-dimensional unsteady flow control equation of groundwater can be expressed as: ； Where: H —groundwater head (m); K xx , K yy , K zz —x, y, z direction permeability (m / d); —Water supply of aquifer or specific water storage coefficient; gravity water supply of phreatic layer μ d , the specific elastic water release coefficient of the confined aquifer is ; —initial water head of aquifer (m); H 1—Boundary water level of each layer (m); —Recharge flow rate per unit area of ​​the second-class boundary of the aquifer (m / d); 1—source-sink intensity (m / d); —seepage area; B1—is the boundary with known hydraulic head, the first type of boundary; B2—is the boundary with known flow, the second type of boundary; —Direction of the unit external normal to the boundary of the vadose zone.

4. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 1, characterized in that: The finite difference format of the three-dimensional unsteady flow control equation of groundwater is expressed as: ； Where: H —aquifer head (m), the superscript is the time and the subscript is the unit cell, e.g. represents the water head value of cell (i,j,k) at time n+1; , , , , , —Hydraulic conductivity in x, y, z directions (m / d), where: ； ； ； ； ； ； ； ； Δx, Δy, and Δz represent the step size of the aquifer spatial grid along the x, y, and z directions. represents the permeability coefficient between the cell (Δx, Δy, Δz) and the cell (Δx, Δy+1, Δz) .

5. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 1, characterized in that: The establishment of the groundwater flow numerical model also includes partitioning the model according to the infiltration coefficient α according to the geological conditions, first obtaining the amount of atmospheric precipitation replenishing groundwater corresponding to the partition number, and then obtaining the amount of atmospheric precipitation replenishing groundwater for the entire model.

6. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 5, characterized in that: The infiltration coefficient α is specifically solved as follows: The dynamic analysis method is used to measure the groundwater level rise Δh after precipitation using a groundwater self-recording water level gauge. The product of Δh and the water value μ brought by the water level change is equal to the precipitation infiltration recharge, expressed as: Pr=μΔh. Dividing it by the precipitation in the same period gives the α value.

7. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 5, characterized in that: The amount of atmospheric precipitation recharging groundwater corresponding to the subdivision number is specifically: Since the effective recharge of groundwater aquifer is closely related to the infiltration coefficient, the formula of infiltration coefficient is expressed as: α = Pr / P; Where P is the precipitation in a certain period, Pr is the effective recharge of groundwater through infiltration, and α is the infiltration coefficient.

8. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 7, characterized in that: The amount of groundwater recharged by atmospheric precipitation in the entire model is specifically: The amount of atmospheric precipitation recharging groundwater in the same partition number is summed up and the average value is calculated, and then the average values ​​obtained in different partition numbers are added together.

9. The method for constructing a three-dimensional groundwater grid model for regional groundwater level research according to claim 3 or 4, characterized in that: The permeability coefficient , considering the single-hole diving incomplete well in groundwater dynamics, the permeability coefficient It is expressed as: ； ； Where: K is the permeability coefficient (m / d); Q is the water inflow (m³ / d); S is the water level drawdown (m); H is the static water level or aquifer thickness (m); R is the influence radius (m); r is the pumping hole radius (m).

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