A method for constructing flux equation of change of underground fresh water storage of coral reef island

Abstract

This invention discloses a method for constructing a flux equation for changes in groundwater storage on coral reef islands. The method includes the following steps: based on the principle of water balance, the change in groundwater storage is defined as the difference between effective rainfall infiltration and freshwater discharge; feature extraction is performed on the rainfall process on the coral reef to obtain rainfall characteristic parameters; the rainfall characteristic parameters are input into the effective rainfall infiltration equation to obtain the effective rainfall infiltration; the chloride ion concentration gradient of the freshwater-saline transition zone and the freshwater-seawater head difference are input into the freshwater discharge equation to obtain the freshwater discharge; the chloride ion transport control equation and the water balance equation are combined to construct a flux equation for changes in groundwater storage based on the effective rainfall infiltration and the freshwater discharge; using chloride ion concentration profile data and head change data collected from mechanistic experiments, machine learning methods are used to fit the undetermined parameters in the flux equation to obtain a calibrated flux equation.

Description

Technical Field

[0001] This invention belongs to the field of groundwater resources and environmental technology for coral reef islands, and particularly relates to a method for constructing a flux equation for changes in groundwater storage on coral reef islands. Background Technology

[0002] Coral reef islands are important carriers for marine resource development, and their groundwater storage is a key resource for the ecological supply, vegetation maintenance, security, and development of the islands and reefs. Existing studies on island and reef freshwater storage mostly focus on static storage estimation, neglecting the coupled influence of rainfall characteristics (rainfall intensity, amount, and pattern) and the permeability of coral sand media, and failing to incorporate the migration patterns in the freshwater-saline transition zone. This results in significant errors in the quantitative results of freshwater storage changes, failing to provide accurate theoretical support for the dynamic management of island and reef freshwater resources. Therefore, this invention proposes a method for constructing a flux equation for groundwater storage changes in coral reef islands. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for constructing a flux equation for changes in underground freshwater storage on coral reef islands, thereby resolving the issues present in the prior art.

[0004] To achieve the above objectives, this invention provides a method for constructing a flux equation for changes in groundwater storage on coral reef islands, comprising: Based on the principle of water balance, the change in groundwater storage is defined as the difference between effective rainfall infiltration and freshwater discharge. Feature extraction was performed on the rainfall process of coral islands and reefs to obtain rainfall characteristic parameters; The rainfall characteristic parameters are input into the effective infiltration equation to obtain the effective infiltration amount of rainfall; The chloride ion concentration gradient in the freshwater-saline water transition zone and the freshwater-seawater head difference are input into the freshwater discharge equation to obtain the freshwater discharge. By combining the chloride ion transport control equation and the water balance equation, a flux equation for the change in groundwater storage is constructed based on the effective infiltration of rainfall and the freshwater discharge. Chloride ion concentration profile data and head change data collected from mechanistic experiments were used to fit the undetermined parameters in the flux equation using machine learning methods to obtain the calibrated flux equation.

[0005] Optionally, the rainfall characteristic parameters include: rainfall pattern, rainfall intensity, and rainfall duration; The process of obtaining the rainfall characteristic parameters includes: extracting rainfall patterns based on the temporal distribution characteristics of the rainfall process, wherein the rainfall patterns are divided into continuous rainfall patterns and intermittent rainfall patterns; extracting rainfall intensity based on rainfall per unit time; and extracting rainfall duration based on rainfall duration.

[0006] Optionally, the process of inputting the rainfall characteristic parameters into the effective rainfall infiltration equation to obtain the effective rainfall infiltration includes: The effective infiltration threshold of coral sand media was determined by mechanistic experiments. The rainfall intensity was compared with the effective infiltration threshold to screen out the rainfall intensity that triggers effective replenishment. The selected rainfall intensity, rainfall duration, and rainfall pattern are input into the effective infiltration equation. The infiltration process is corrected based on the rainfall pattern control coefficient and the infiltration capacity decay function to obtain the effective infiltration amount of rainfall.

[0007] Optionally, the effective infiltration equation is: ; In the formula, For effective infiltration, This is the control coefficient for the rainfall pattern. Let T be the infiltration capacity decay function, T be the total rainfall duration, and I be the rainfall intensity. is the saturated permeability coefficient of the infiltrating medium.

[0008] Optionally, the process of inputting the chloride ion concentration gradient in the freshwater-saline water transition zone and the freshwater-seawater head difference into the freshwater discharge equation to obtain the freshwater discharge includes: Based on the migration patterns in the freshwater-saline water transition zone, the chloride ion concentration gradient is input into the transition zone discharge equation to obtain the transition zone discharge amount; Based on the hydraulic gradient driving law, the freshwater-seawater head difference and the distance from the edge of the freshwater lens to the ocean are input into the hydraulic driving discharge equation to obtain the hydraulic driving discharge. The freshwater discharge is obtained by summing the discharge from the transition zone and the hydraulically driven discharge.

[0009] Optionally, the freshwater discharge equation is: ; In the formula, This refers to freshwater discharge. This refers to the discharge volume in the transition zone. The discharge volume is driven by hydraulic power.

[0010] Optionally, the flux equation for the change in groundwater storage is: ; In the formula, Changes in underground freshwater storage The permeability coefficient of the coral sand medium, For freshwater lens head, For seawater head, The distance from the lens to the ocean. The density is that of fresh water. The density of seawater, This represents the vertical gradient of chloride ion concentration. Chloride ion concentration, This represents the vertical distance.

[0011] Optionally, the process of constructing a flux equation for changes in groundwater storage based on the effective infiltration of rainfall and the freshwater discharge, by simultaneously establishing the chloride ion transport control equation and the water balance equation, includes: Substituting the effective infiltration of rainfall and the freshwater discharge into the difference expression defined based on the principle of water balance, we obtain the flux equation framework. By combining the flux equation framework with the chloride ion transport control equation, and constraining the flux equation based on the chloride ion mass conservation relationship, a flux equation for the change in groundwater storage containing undetermined parameters is obtained.

[0012] Optionally, the chloride ion transport control equation is: ; In the formula, Here, is the dispersion coefficient, and t is the rainfall duration. Porosity.

[0013] The present invention also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention, by screening rainfall characteristic parameters (intensity, duration, and pattern), based on the principle of water balance and the law of conservation of mass, coupled with the permeability characteristics of coral sand media, constructs equations for effective rainfall infiltration and freshwater-saline water discharge, and simultaneously establishes chloride ion transport control equations to obtain flux equations for changes in groundwater storage; and by combining mechanistic experiments and machine learning fitting parameters, it achieves precise quantification of changes in groundwater storage on islands and reefs. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a diagram illustrating the physical experimental mechanism of groundwater storage changes under the influence of rainfall characteristics in an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] Example 1 like Figure 1 As shown, Figure 1 This diagram illustrates the physical experimental mechanism by which rainfall characteristics affect changes in groundwater storage, showcasing the device structure and process in the initial stage (distribution of seawater layer and coral sand medium layer) and the experimental stage (rainfall, formation of freshwater lens, and discharge of freshwater and brackish water). This embodiment provides a method for constructing a flux equation for changes in groundwater storage on coral reef islands, including the following steps: Based on the principle of water balance, the change in groundwater storage is defined as the difference between effective rainfall infiltration and freshwater discharge; feature extraction is performed on the rainfall process of the coral reef to obtain rainfall characteristic parameters; the rainfall characteristic parameters are input into the effective rainfall infiltration equation to obtain the effective rainfall infiltration; the chloride ion concentration gradient of the freshwater-saline water transition zone and the freshwater-seawater head difference are input into the freshwater discharge equation to obtain the freshwater discharge; the chloride ion transport control equation and the water balance equation are combined to construct a flux equation for changes in groundwater storage based on the effective rainfall infiltration and freshwater discharge; using chloride ion concentration profile data and head change data collected from mechanistic experiments, machine learning methods are used to fit the undetermined parameters in the flux equation to obtain a calibrated flux equation. The specific implementation process includes: S1: Filter representative characteristic parameters of rainfall on coral reefs, including rainfall pattern, rainfall intensity, and rainfall duration; S2: Based on the principle of water balance and the law of conservation of mass, the change in groundwater storage is defined as the difference between infiltration and discharge, i.e. S3: Construct the equation for effective rainfall infiltration. By coupling rainfall characteristic parameters, the permeability coefficient of coral sand media, and the media infiltration capacity attenuation function, we obtain... ,in This is the control coefficient for the rainfall pattern. This is the infiltration capacity decay function; S4: Construct a freshwater discharge equation, and combine the transport laws of the freshwater-saline transition zone with the hydraulic gradient driving law to obtain the discharge volume. ,in This refers to the discharge volume in the transition zone. The discharge volume is driven by hydraulic power. S5: By combining the chloride ion transport control equation and the water balance equation, the flux equation for changes in groundwater storage is obtained: ; In the formula, Changes in underground freshwater storage The permeability coefficient of the coral sand medium, For freshwater lens head, For seawater head, The distance from the lens to the ocean. The density is that of fresh water. The density of seawater, This represents the vertical gradient of chloride ion concentration, where C is the chloride ion concentration. This represents the vertical distance.

[0019] S6: The chloride ion concentration profile and head change were determined through mechanistic experiments, and the flux equation was verified and solved by combining the parameters with machine learning.

[0020] S7: Construct the desalination rate equation for freshwater lenses in coral reefs. Specifically, using the decrease in chloride ion concentration in the freshwater lens per unit time as the desalination rate V, and combining the convective mass transfer term and the edge diffusion term, we obtain: in, To account for evaporation and the geological structure of coral islands and reefs, the effective rainfall infiltration correction factor is used. The average concentration of the freshwater lens. R The radius of the island / reef. The characteristic diffusion radius, This represents the average concentration at the edge transition zone.

[0021] In step S1, the effective infiltration threshold of rainfall characteristic parameters is determined experimentally: critical recharge intensity under different rainfall characteristics. ,when Triggering effective supply replenishment Let be the saturated permeability coefficient of the infiltration medium, when When the infiltration medium reaches saturation, it can only infiltrate further. Intensity of infiltration.

[0022] In step S5, the governing equation for chloride ion transport is: ， in Here, denoted as the dispersion coefficient, and t is the rainfall duration. Porosity.

[0023] As another specific implementation of this embodiment, a method for constructing a flux equation for changes in groundwater storage on a coral reef island includes: Experimental preparation: A coral reef mechanism experimental setup was constructed, including a coral sand medium layer, an in-situ coral sand layer, and a seawater layer. Initially, the chloride ion concentration in the seawater was controlled to be [value missing]. The head of the freshwater lens is .

[0024] Rainfall characteristic parameter control: 90 sets of rainfall experimental data were selected to control rainfall patterns and intensity. I Duration T The control coefficient during intermittent rainfall ( (Effective infiltration correction factor).

[0025] Effective infiltration rate determination: The infiltration threshold of coral sand media was determined experimentally. ,when When the medium reaches saturation, the infiltration rate is calculated according to... Calculation; combined with infiltration capacity decay function Points earned .

[0026] Excretion volume measurement: Freshwater-saline transition zone discharge: according to Measurement; Hydraulic-driven discharge volume: based on Measurement.

[0027] Solving the simultaneous equations: By combining the chloride ion transport governing equation and the water equilibrium equation, we obtain the flux equation: Fitting chloride ion concentration profile using machine learning Data, iteratively solve the equation parameters.

[0028] The selection of rainfall characteristic parameters specifically includes: rainfall patterns are divided into continuous rainfall patterns and intermittent rainfall patterns; rainfall intensity... I The quantification range is 0.5~20 mm / h; total rainfall duration T The quantization range is 1~72 h.

[0029] The effective infiltration threshold is determined by controlling the rainfall intensity at different gradients. I Mechanism experiments were conducted, and the rainfall intensity corresponding to the observed continuous water accumulation on the surface of the coral sand media layer was defined as the effective infiltration threshold. .

[0030] In step S3, the infiltration capacity decay function attenuation coefficient k The determination method is as follows: measuring different rainfall durations. tThe actual infiltration rate, with the ratio of the actual infiltration rate to the initial infiltration rate as the dependent variable and the duration. t By performing an exponential fit on the independent variable, the decay coefficient is obtained. k The value range is 0.01~0.1 h. -1 .

[0031] In step S3, the rainfall pattern control coefficient Medium correction coefficient The method for determining this is as follows: when the rainfall pattern is continuous, When rainfall is intermittent, The value ranges from 0.6 to 0.9, and the specific value is determined by the proportion of the intermittent rainfall's pause in the rain.

[0032] In step S4, the discharge volume in the transition zone Permeability coefficient of medium coral sand media layer K The determination method is as follows: The Darcy test with constant head is used to determine the permeability coefficient of coral sand media under different compaction degrees. The permeability coefficient matching the actual compaction degree of the coral reef is selected as the... K The value of .

[0033] In step S4, the hydraulically driven discharge volume Distance from the medium lens to the ocean L The measurement method is as follows: The horizontal extension of the coral reef medium layer is detected using ground-penetrating radar, and the horizontal distance from the edge of the freshwater lens to the reef coastline is used as the baseline. L The value of .

[0034] In step S5, the dispersion coefficient in the chloride ion transport governing equation The calculation method is as follows: determine the migration distance of the freshwater-saline water front and the corresponding time. Using the frontal transport formula The dispersion coefficient was calculated. .

[0035] In step S6, the specific steps for fitting parameters using machine learning are as follows: (1) Chloride ion concentration profiles at different times during the sampling mechanism experiment Changes in water head Data on the rate of infiltration surface decline; (2) The gradient descent algorithm was selected as the fitting algorithm, and the objective function was to minimize the mean square error between the calculated and measured values ​​of the flux equation. (3) Obtain parameters through iterative fitting , The optimal value.

[0036] This invention discloses a method for constructing flux equations for changes in groundwater storage under rainfall characteristics in coral reefs based on the principle of water balance, relating to the field of groundwater engineering in marine coral reefs. This method, by selecting rainfall characteristic parameters (intensity, duration, and pattern), and based on the principle of water balance and the law of conservation of mass, coupled with the permeability characteristics of coral sand media, constructs equations for effective rainfall infiltration and freshwater-saline water discharge, and simultaneously establishes chloride ion transport control equations to obtain flux equations for changes in groundwater storage. Furthermore, by combining mechanistic experiments and machine learning to fit parameters, it achieves precise quantification of changes in groundwater storage in islands and reefs.

[0037] This embodiment also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0038] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for constructing a flux equation for changes in groundwater storage on a coral reef island, characterized in that, Includes the following steps: Based on the principle of water balance, the change in groundwater storage is defined as the difference between effective rainfall infiltration and freshwater discharge. Feature extraction was performed on the rainfall process of coral islands and reefs to obtain rainfall characteristic parameters; The rainfall characteristic parameters are input into the effective infiltration equation to obtain the effective infiltration amount of rainfall; The chloride ion concentration gradient in the freshwater-saline water transition zone and the freshwater-seawater head difference are input into the freshwater discharge equation to obtain the freshwater discharge. By combining the chloride ion transport control equation and the water balance equation, a flux equation for the change in groundwater storage is constructed based on the effective infiltration of rainfall and the freshwater discharge. Chloride ion concentration profile data and head change data collected from mechanistic experiments were used to fit the undetermined parameters in the flux equation using machine learning methods to obtain the calibrated flux equation.

2. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 1, characterized in that, The rainfall characteristic parameters include: rainfall pattern, rainfall intensity, and rainfall duration; The process of obtaining the rainfall characteristic parameters includes: extracting rainfall patterns based on the temporal distribution characteristics of the rainfall process, wherein the rainfall patterns are divided into continuous rainfall patterns and intermittent rainfall patterns; extracting rainfall intensity based on rainfall per unit time; and extracting rainfall duration based on rainfall duration.

3. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 1, characterized in that, The process of inputting the rainfall characteristic parameters into the effective infiltration equation to obtain the effective infiltration amount includes: The effective infiltration threshold of coral sand media was determined by mechanistic experiments. The rainfall intensity was compared with the effective infiltration threshold to screen out the rainfall intensity that triggers effective replenishment. The selected rainfall intensity, rainfall duration, and rainfall pattern are input into the effective infiltration equation. The infiltration process is corrected based on the rainfall pattern control coefficient and the infiltration capacity decay function to obtain the effective infiltration amount of rainfall.

4. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 3, characterized in that, The effective infiltration rate equation is: ； In the formula, For effective infiltration, This is the control coefficient for the rainfall pattern. Let T be the infiltration capacity decay function, T be the total rainfall duration, and I be the rainfall intensity. is the saturated permeability coefficient of the infiltrating medium.

5. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 3, characterized in that, The process of inputting the chloride ion concentration gradient in the freshwater-saline transition zone and the freshwater-seawater head difference into the freshwater discharge equation to obtain the freshwater discharge volume includes: Based on the migration patterns in the freshwater-saline water transition zone, the chloride ion concentration gradient is input into the transition zone discharge equation to obtain the transition zone discharge amount; Based on the hydraulic gradient driving law, the freshwater-seawater head difference and the distance from the edge of the freshwater lens to the ocean are input into the hydraulic driving discharge equation to obtain the hydraulic driving discharge. The freshwater discharge is obtained by summing the discharge from the transition zone and the hydraulically driven discharge.

6. The method for constructing the flux equation for changes in groundwater storage on coral reef islands according to claim 5, characterized in that, The equation for the freshwater discharge volume is: ； In the formula, This refers to freshwater discharge. This refers to the discharge volume in the transition zone. The discharge volume is driven by hydraulic power.

7. The method for constructing the flux equation for changes in groundwater storage on coral reef islands according to claim 6, characterized in that, The flux equation for the change in groundwater storage is: ； In the formula, Changes in underground freshwater storage The permeability coefficient of the coral sand medium, For freshwater lens head, For seawater head, The distance from the lens to the ocean. The density is that of fresh water. The density of seawater, This represents the vertical gradient of chloride ion concentration. C Chloride ion concentration, This represents the vertical distance.

8. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 7, characterized in that, The process of constructing a flux equation for changes in groundwater storage based on the effective infiltration of rainfall and the freshwater discharge, by simultaneously establishing the chloride ion transport control equation and the water balance equation, includes: Substituting the effective infiltration of rainfall and the freshwater discharge into the difference expression defined based on the principle of water balance, we obtain the flux equation framework. By combining the flux equation framework with the chloride ion transport control equation, and constraining the flux equation based on the chloride ion mass conservation relationship, a flux equation for the change in groundwater storage containing undetermined parameters is obtained.

9. The method for constructing the flux equation for changes in underground freshwater storage on coral reef islands according to claim 8, characterized in that, The governing equation for chloride ion transport is: ； In the formula, Here, is the dispersion coefficient, and t is the rainfall duration. Porosity.

10. A computer comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in claim 1.

Images