A method and system for measuring and calculating the methane reserves of a reservoir in an ice-covered region
Patent Information
- Application Number
- CN202611424269.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-15
- Publication Date
- 2026-10-20
AI Technical Summary
[0002]受限于环境条件与采样分析方法，甲烷年排放估算中冰封期的研究较少，使得甲烷排放估算的数据不全面，影响到排放模型的建立
[0056]本方法主要依托实测资料开展，基于水库地形数据、水位与水环境等常规观测数据的计算，在水库温室气体扩散通量、气泡通量的基础上，拓展为甲烷储量的计算方法。通过选取典型的冰封时期的序列（冰封稳定期），分析冰封时期水库各区域冰体、水体、沉积物中的甲烷现存量、水库中甲烷变化量，结合不考虑冰封期水库冰面破碎逃逸的甲烷量，计算冰封稳定期水库甲烷的现存量，按照Stefan公式计算冰封时长，进而计算水库甲烷变化量，基于现存量和变化量，计算冰封期水库甲烷储量。计算数据依据充分，方法机理明确，实施过程清楚，技术手段可行。
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Abstract
Description
Technical Field
[0001] This application relates to the field of technology development related to water resources and water environment, and in particular to a method and system for measuring and calculating methane reserves in reservoirs in ice-covered areas. Background Technology
[0002] Limited by environmental conditions and sampling analysis methods, there are few studies on the ice-covered period in annual methane emission estimation, resulting in incomplete data and affecting the establishment of emission models. Furthermore, existing models rarely address the unique environmental conditions of ice-covered areas, leading to limited understanding of methane occurrence characteristics during this period. There is an urgent need to explore a model capable of accurately calculating the methane occurrence characteristics in reservoir sediment-water-ice systems, thereby quantitatively assessing methane emissions from reservoirs in ice-covered regions and providing technical support for greenhouse gas accounting systems and water environment management and protection in these areas. Summary of the Invention
[0003] The purpose of this application is to provide a method and system for measuring and calculating methane reserves in reservoirs in frozen areas. This method can support greenhouse gas accounting in reservoirs in frozen areas and can also be used to identify methane-producing hotspots and hotspots in reservoirs, assess the carbon source and carbon sink relationship in reservoirs, and provide a basis for reservoir protection and management planning.
[0004] The technical solution of this invention:
[0005] In a first aspect, embodiments of this application provide a method for measuring and calculating methane reserves in reservoirs in ice-covered areas, comprising the following steps:
[0006] Step 1. Divide the reservoir into sediment bubble generation zones and non-bubble generation zones;
[0007] Step 2. Calculate the current methane content in ice, water, and sediments during the ice-covered period;
[0008] Step 3. Measure the methane bubble formation rate, methane diffusion formation rate, and methane oxidation rate in the water at the sediment-water interface;
[0009] Step 4. Model and calculate the methane reserves in the reservoir during the ice-covered period.
[0010] The implementation method of step 1 is as follows:
[0011] Step 11. Reservoir water level distribution profile, dividing the reservoir into deep water and shallow water areas;
[0012] Step 12. The shallow water area is divided into bubble zone and non-bubble zone, which are distinguished by the bubbles encased in the ice surface. Through on-site observation, sampling points with obvious bubbles encased in the ice surface are defined as bubble zone points, and the remaining points are defined as non-bubble zone points.
[0013] The implementation method of step 2 is as follows:
[0014] Step 21. Current methane levels in the deep water area of the reservoir during the ice-covered period. This refers to the current methane levels within the ice in the deep water area. :
[0015]
[0016] In the formula This represents the concentration of methane in the ice in the deep water area. The surface area of the deep water zone; The thickness of the ice in the deep water area.
[0017] Regarding methane reserves in deep-water areas :
[0018] ,
[0019] In the formula, , , These represent the concentrations of methane in the surface, middle, and bottom layers of deep-water bodies, respectively. The surface area of the deep water zone. The depth of the water in the deep water area.
[0020] Regarding the current methane content in deep-water sediments :
[0021] ,
[0022] In the formula, This represents the concentration of methane in sediments from deep water areas. The surface area of the deep water zone. The thickness of sediments in deep water areas.
[0023] Step 22. Methane content in shallow water areas of the reservoir during the ice-covered period: For the methane content in the ice of the shallow water area, ice-covered bubbles were classified and quantified based on UAV imagery, resulting in a planar density distribution map of ice-covered bubbles in the bubble region. Combined with the methane concentration (gaseous + dissolved) in the ice obtained from the ice-melting experiment, a linear fitting model was established to determine the methane concentration in the ice (…). Regarding the area density of ice-sealed bubbles ( The regression equation for methane in the shallow water ice body and the methane content in each region were obtained by combining this equation with the bubble area ratio map and the distribution map of the bubble area in the shallow water area.
[0024] The current methane content in shallow water bodies is calculated as follows:
[0025]
[0026] In the formula, These represent the concentrations of methane in the surface, middle, and bottom layers of shallow water, respectively. The water surface area of the shallow water area. These represent the depths of the surface, middle, and bottom layers of the shallow water area. Divided into non-bubble areas and bubble area t is the day the model is set, which is t = 1 d.
[0027] The depth of the middle water layer is:
[0028] .
[0029] The implementation method of step 3 is as follows:
[0030] Step 31. Measure the methane bubble formation rate at the sediment-water interface, the methane diffusion formation rate at the sediment-water interface, and the methane oxidation rate in the water body;
[0031] The methane concentration in sediment interstitial water was calculated as follows:
[0032] ,
[0033] In the formula, The concentration of methane in the interstitial water. To determine the headspace methane concentration in the culture flask, The volume of headspace gas in the culture flask. This refers to the volume of interstitial water inside the culture bottle.
[0034] The methane diffusion flux at the sediment-water interface is calculated using Fick's first law, based on the difference in greenhouse gas concentration between the interstitial water of the sediment surface layer and the overlying water. It represents the amount of material that passes vertically through a unit area per unit time. The formula is as follows:
[0035]
[0036] In the formula, It is the gas diffusion flux at the sediment-water interface. It refers to the porosity of sediments; It is the correction curvature (represented as) ); It is the diffusion coefficient of methane in water as a function of temperature. At 5℃, The value is 1.12 × 10 -9 m 2 / s; It is the vertical gradient of dissolved gas concentration in the sediment.
[0037] Step 32. Methane bubble transport flux was collected using an inverted funnel method positioned 10 cm from the sediment-water interface and calculated in time increments. The calculation formula is as follows:
[0038]
[0039] In the formula, It is the methane bubble transport flux. It refers to greenhouse gas concentration. It is the volume of gas collected. It is the area at the opening of the funnel. It is the time the funnel is placed. It is the standard volume of a gas.
[0040] Step 33. Ten replicate water samples (120 mL each) were collected from both the deep and shallow water areas. In the laboratory, the bottles were incubated at a constant temperature of 5°C in the dark. The methane concentration in the sealed bottles was measured five times on days 1, 2, 3, 5, and 7, using the following formula:
[0041] ,
[0042] In the formula, It is the rate of methane oxidation in water. and These are the initial concentration and the concentration at t(h), respectively.
[0043] The implementation method of step 4 is as follows:
[0044] Step 41. Calculation of freezing duration: the number of freezing days is the total number of days from the first day of freezing to the complete thawing, i.e., the entire freezing process. The number of days of ice cover is the total number of days from the complete freezing of the entire reservoir area to the complete disappearance of the ice cover.
[0045] Step 42. Changes in methane levels in the reservoir during the ice-bound period. The model basis for the generation amount is the parameters measured in the field during the ice-stable period. The data for bubble generation is obtained from the bottom methane bubble transport rate obtained by the inverted funnel. The data for diffusion generation is obtained from the sediment-water interface methane diffusion flux calculated from the concentration gradient between sediment interstitial water and bottom water. The model basis for the oxidation amount is obtained from the methane oxidation rate at 5℃ obtained from the simulation experiment. The change in methane reserves is calculated as the time elapsed from the ice-stable period to the ice melting time.
[0046] Step 43. Methane reserves in reservoirs in ice-bound areas: The methane reserves in reservoirs in ice-bound areas are the sum of the current methane reserves in the reservoirs during the ice-stable period and the changes in methane reserves in the reservoirs during the ice-bound period.
[0047] Secondly, embodiments of this application provide a system for calculating methane reserves in reservoirs in ice-covered areas, including,
[0048] The data collection module is used to collect observation data on the area, water depth, and sediment depth of the deep water area, shallow water bubble area, and shallow water non-bubble area of the reservoir during the ice-covered period.
[0049] The correlation establishment module is used to establish the methane concentration in ice. Regarding the area density of frozen bubbles The correlation;
[0050] The module for calculating the methane reserves in sediments calculates the methane reserves in sediments in each section of the reservoir.
[0051] The module for calculating the current amount of methane in the water body calculates the methane reserves in each section of the reservoir.
[0052] The module for calculating the duration of ice cover combines the Stefan formula with the actual opening date of the reservoir to calculate the number of days the reservoir is frozen.
[0053] The module for calculating methane changes in the reservoir combines the sediment bubble rate, sediment diffusion rate, and methane oxidation rate in the water body measured by simulation experiments to calculate the methane changes in the reservoir.
[0054] The module for calculating methane reserves in reservoirs in ice-bound areas uses the existing methane levels in ice, water, and sediments, as well as the changes in methane levels in the reservoir, to calculate the total methane reserves in reservoirs in ice-bound areas.
[0055] Compared with the prior art, the beneficial effects of the present invention are:
[0056] This method primarily relies on measured data, calculating based on conventional observational data such as reservoir topography, water level, and aquatic environment. Building upon the calculations of greenhouse gas diffusion flux and bubble flux in reservoirs, it extends this method to calculate methane reserves. By selecting a typical ice-covered period sequence (ice-stable period), the method analyzes the existing methane reserves in ice, water, and sediments in various areas of the reservoir during the ice-covered period, as well as the changes in methane levels within the reservoir. Considering the amount of methane escaped due to ice breakup during the ice-covered period, the existing methane reserves in the reservoir during the ice-stable period are calculated. The ice-covered duration is calculated using the Stefan formula, and then the changes in methane levels in the reservoir are calculated. Based on the existing reserves and changes, the methane reserves in the reservoir during the ice-covered period are calculated. The calculation data is well-supported, the methodological mechanism is clear, the implementation process is straightforward, and the technical means are feasible. Attached Figure Description
[0057] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0058] Figure 1 Conceptual diagram of methane reserves during reservoir ice-covered period;
[0059] Figure 2 This is a flowchart illustrating a method for calculating methane reserves in a reservoir in a frozen area, according to an embodiment of the present invention.
[0060] Figure 3 This relates the bubble area density to the methane concentration in the ice.
[0061] Figure 4 This is a system block diagram according to an embodiment of the present invention. Detailed Implementation
[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0063] like Figures 1 to 2 As shown in the embodiment of this application, a method for calculating methane reserves in a reservoir in a frozen area is provided, which includes the following steps:
[0064] The implementation method of step 1 is as follows:
[0065] Step 11. Reservoir water level distribution profile, dividing the reservoir into deep water and shallow water areas;
[0066] Step 12. According to the "ice bubble classification method," the shallow water area is divided into bubble zone and non-bubble zone. This method uses the bubbles encased in the ice surface to distinguish them. Through on-site observation, sampling points with obvious bubbles encased in the ice surface are defined as bubble zone points, and the remaining points are defined as non-bubble zone points.
[0067] The implementation method of step 2 is as follows:
[0068] Step 21. Current methane levels in the deep water area of the reservoir during the ice-covered period. This refers to the current methane levels within the ice in the deep water area. :
[0069]
[0070] In the formula, The concentration of methane in the ice in the deep water area, in μmol / L; The surface area of the deep water zone is in meters. 2 ; The thickness of the ice in the deep water area is in meters (m).
[0071] Regarding methane reserves in deep-water areas :
[0072]
[0073] In the formula, , , These represent the concentrations of methane in the surface, middle, and bottom layers of deep-water bodies, respectively, in μmol / L. The surface area of the deep water zone is in meters. 2 ; The depth of the deep water area, in meters (m).
[0074] Regarding the current methane content in deep-water sediments :
[0075]
[0076] In the formula, The concentration of methane in deep-water sediments, in μmol / L; The surface area of the deep water zone is in meters. 2 ; The thickness of the sediment in the deep water area is expressed in meters (m).
[0077] Step 22. Methane content in shallow water areas of the reservoir during the ice-covered period: For the methane content in the ice of the shallow water area, ice-covered bubbles were classified and quantified based on UAV imagery, resulting in a planar density distribution map of ice-covered bubbles in the bubble region. Combined with the methane concentration (gaseous + dissolved) in the ice obtained from the ice-melting experiment, a linear fitting model was established to determine the methane concentration in the ice (…). Regarding the area density of ice-sealed bubbles ( The regression equation for methane in the bubble zone is derived. Combining this equation with the bubble area proportion map and the distribution maps of different regions within the bubble zone in the shallow water area, the methane content in the ice body of the shallow water area and the methane content in each region are summed to obtain the total methane content. Using average values to estimate the methane content in the bubble zone will underestimate the actual methane content in the ice body. The bubble modeling method based on UAV observations can optimize the estimation of the methane content in the bubble zone.
[0078] The current methane content in shallow water bodies is calculated as follows:
[0079]
[0080] In the formula, The concentrations of methane in the surface, middle, and bottom layers of shallow water, respectively, are shown in μmol / L. The surface area of the shallow water area is expressed in meters. 2 ; , , These represent the depths of the surface, middle, and bottom layers of the shallow water area, in meters (m). Shallow water area Divided into non-bubble areas and bubble area mmol / m 2 / d; t is the day the model is set, which is t = 1 d.
[0081] Based on the experimental results observed in the field, methane accumulation was observed in the surface water of both the bubble zone and the non-bubble zone in the shallow water area, with an accumulation range of 0-50 cm. Therefore... and The sampling depth in the bottom water body is 0.50 m; the sampling depth is 50 cm from the sediment-water interface. and The depth of the middle layer of water is 0.50 m;
[0082] .
[0083] The implementation method of step 3 is as follows:
[0084] Step 31. Measure the methane bubble formation rate at the sediment-water interface, the methane diffusion formation rate at the sediment-water interface, and the methane oxidation rate in the water body;
[0085] The methane concentration in sediment interstitial water was calculated as follows:
[0086]
[0087] In the formula, The concentration of methane in the interstitial water is in nmol / L. The headspace methane concentration in the culture flask is expressed in μL / L. The volume of headspace gas in the culture flask, in mL; The volume of interstitial water in the culture flask is expressed in mL.
[0088] The methane diffusion flux at the sediment-water interface is calculated using Fick's first law, based on the difference in greenhouse gas concentration between the interstitial water of the sediment surface layer and the overlying water. It represents the amount of material that passes vertically through a unit area per unit time. The formula is as follows:
[0089]
[0090] In the formula,
[0091] It is the gas diffusion flux at the sediment-water interface, μmol / m 2 / d; It refers to the porosity of sediments; It is the correction curvature (represented as) ); It is the diffusion coefficient of methane in water as a function of temperature, m 2 / s, at 5℃ The value is 1.12 × 10 -9 m 2 / s; It is the vertical gradient of dissolved gas concentration in the sediment, mmol / m³ 4 To calculate the methane gradient at the sediment-water interface, this study used the gas concentration in the overlying water (measured at a depth of 50 cm above the surface sediments) and the gas concentrations at the first two depths in the interstitial water (sampling depths of 2 cm and 4 cm in the sediments) to represent the concentration at the sediment-water interface, and determined the concentration gradient through linear regression. Our flux estimation method is based on the assumption of steady-state diffusion transport in interstitial water and neglects the effects of gas generation and consumption, as well as the possible influence of the water-side concentration boundary layer.
[0092] Step 32. Methane bubble transport flux was collected using an inverted funnel method positioned 10 cm from the sediment-water interface and calculated in time increments. The calculation formula is as follows:
[0093]
[0094] In the formula, This is the methane bubble transport flux, mmol / m³. 2 / d; This refers to the concentration of greenhouse gases, in µL / L. It is the volume of gas collected, in L; It is the area at the opening of the funnel, m 2 ; It is the time the funnel was placed, d; It is the standard volume of gas, which is 22.4 mol / L.
[0095] Step 33. Ten replicate water samples (120 mL each) were collected from both the deep and shallow water areas. In the laboratory, the bottles were incubated in the dark at a constant temperature of 5°C (representing winter water temperature). The methane concentration in the sealed bottles was measured five times on days 1, 2, 3, 5, and 7, using the following formula:
[0096]
[0097] In the formula, It is the rate of methane oxidation in water. ; and These are the initial concentration and the concentration at t (h), respectively, in nmol / L.
[0098] The implementation method of step 4 is as follows:
[0099] Step 41. Calculation of freezing duration.
[0100] The entire freezing process begins and ends with accumulated negative temperature. Meteorologically, the cumulative value of daily average temperatures below 0°C is called accumulated negative temperature. It reflects the total amount of temperature or heat resources that a local climate can provide for a particular natural process. Since the freezing point of freshwater ice in reservoirs is 0°C, ice thickness is directly related to accumulated negative temperature. Specifically, if the daily average temperature is below 0°C for three consecutive days, the fourth day is called the first frost day. After the first frost day, as the temperature drops, the ice thickness continuously increases until it reaches its maximum; subsequently, the temperature gradually rises, and the ice begins to melt and disappear. The cumulative number of days with daily average temperatures above 0°C after freezing is called accumulated positive temperature. The first day is defined as the first day of a three-day period with daily average temperatures above 0°C. The accumulated positive temperature of the ice is calculated from the first frost day until the reservoir opens. As the accumulated daily average positive temperature increases, the ice thickness gradually decreases. The definition of a melting day is related to various factors such as accumulated positive temperature, wind speed, and solar radiation. Combining the Stefan formula and the actual opening date of the reservoir, this study assumes that the ice cover disappears when the accumulated daily average positive temperature reaches 50℃. The number of freezing days is the total number of days from the first freezing day to the complete thawing, i.e., the entire freezing process, while the number of ice-covered days is the total number of days from the complete freezing of the entire reservoir area to the complete disappearance of the ice cover.
[0101] Step 42. Changes in methane levels in the reservoir during the ice-covered period.
[0102] The model for methane generation is based on parameters measured in-situ during the ice-stabilized period. Specifically, data on bubble generation comes from the bottom-layer methane bubble transport rate obtained using an inverted funnel; data on diffusion generation comes from the sediment-water interface methane diffusion flux calculated from the concentration gradient between interstitial water and bottom water. The model for methane oxidation is based on the methane oxidation rate obtained from simulation experiments at 5°C. Changes in methane reserves are calculated as the time elapsed from the ice-stabilized period to the ice melt.
[0103] Step 43. Methane reserves in reservoirs in ice-covered areas.
[0104] The methane reserves in reservoirs in ice-bound areas are the sum of the current methane reserves during the ice-stable period and the changes in methane reserves during the ice-bound period.
[0105] The specific steps of the embodiment are as follows:
[0106] Step 1: Conduct an investigation on the ice body during the ice stabilization period of a certain reservoir in 2023. The spatial scale is divided into deep water area, shallow water bubble area and shallow water non-bubble area. The area of each area is extracted with the assistance of drones.
[0107] Step 2: On-site measurement of ice thickness, water depth, and sediment thickness;
[0108] Step 3: Sample and determine the methane concentration in ice, water, and sediment;
[0109] Step 4: Establish the methane concentration in the ice ( Regarding the area density of ice-sealed bubbles ( The related relationships, such as Figure 3 ;
[0110] Step 5: Calculate the methane reserves in the ice.
[0111] like Figure 4 As shown in the embodiment of this application, a system for calculating methane reserves in reservoirs in ice-covered areas is provided, including:
[0112] Data collection module 1 is used to collect observation data on the area, water depth, and mud depth of the deep water area, shallow water bubble area, and shallow water non-bubble area of the reservoir during the ice-covered period.
[0113] Module 2, which establishes the correlation, is used to establish the methane concentration in ice. Regarding the area density of ice-sealed bubbles ( The relationship between them;
[0114] Module 3, which calculates the methane reserves in the ice body of each section of the reservoir, calculates the methane reserves in the ice body of each section of the reservoir.
[0115] Module 4, which calculates the methane reserves in sediments of each zone of the reservoir, is used to calculate the methane reserves in the sediments of each zone.
[0116] Module 5, which calculates the methane reserves in the water body, calculates the methane reserves in each section of the reservoir.
[0117] Module 6, which calculates the duration of freezing, combines the Stefan formula with the actual opening date of the reservoir to calculate the number of days the reservoir is frozen.
[0118] Module 7, which calculates the change in methane in the reservoir, combines the sediment bubble rate, sediment diffusion rate, and methane oxidation rate in the water body measured by simulation experiments to calculate the change in methane in the reservoir.
[0119] Module 8, which calculates the methane reserves in reservoirs in frozen areas, uses the existing methane levels in ice, water, and sediments, as well as the changes in methane levels in the reservoir, to calculate the total methane reserves in reservoirs in frozen areas.
[0120] The above embodiments are merely illustrative examples of the technical solution of the present invention. The method for constructing time-varying forms of hydrodynamic mathematical model parameters involved in the present invention is not limited to the content described in the above embodiments, but is subject to the scope defined by the claims. Any modifications, additions, or equivalent substitutions made by those skilled in the art based on these embodiments are within the scope of protection claimed by the present invention.
Claims
1. A method for measuring and calculating methane reserves in reservoirs in ice-covered areas, characterized in that, Includes the following steps: Step 1. Divide the reservoir into sediment bubble generation zones and non-bubble generation zones; Step 2. Calculate the current methane content in ice, water, and sediments during the ice-covered period; Step 3. Measure the methane bubble formation rate at the sediment-water interface, the methane diffusion formation rate at the sediment-water interface, and the methane oxidation rate in the water. Step 4. Model and calculate the methane reserves in the reservoir during the ice-covered period.
2. The method for measuring and calculating methane reserves in a reservoir in a frozen area according to claim 1, characterized in that, The implementation method of step 1 is as follows: Step 11. Reservoir water level distribution profile, dividing the reservoir into deep water and shallow water areas; Step 12. The shallow water area is divided into bubble zone and non-bubble zone, which are distinguished by the bubbles encased in the ice surface. Through on-site observation, sampling points with obvious bubbles encased in the ice surface are defined as bubble zone points, and the remaining points are defined as non-bubble zone points.
3. The method for measuring and calculating methane reserves in a reservoir in a frozen area according to claim 1, characterized in that, The implementation method of step 2 is as follows: Step 21. Current methane levels in the deep water area of the reservoir during the ice-covered period. This refers to the current methane levels within the ice in the deep water area. : ， In the formula, This represents the concentration of methane in the ice in deep water. The surface area of the deep water zone. The thickness of the ice in the deep water area, Regarding methane reserves in deep-water areas : ， In the formula, , , These represent the concentrations of methane in the surface, middle, and bottom layers of deep-water bodies, respectively. The surface area of the deep water zone. The depth of the deep water area Regarding the current methane content in deep-water sediments : ， In the formula, This represents the concentration of methane in sediments from deep water areas. The surface area of the deep water zone. The thickness of sediments in deep water areas, Step 22. Current methane levels in shallow water areas of the reservoir during the ice-covered period. The current methane levels in shallow water areas are calculated as follows: ， In the formula, , , These represent the concentrations of methane in the surface, middle, and bottom layers of shallow water, respectively. The water surface area of the shallow water area. , , These represent the depths of the surface, middle, and bottom layers of the shallow water area. Divided into non-bubble areas and bubble area t is the day the model is set. The depth of the middle water layer is: 。 4. The method for measuring and calculating methane reserves in a reservoir in a frozen area according to claim 1, characterized in that, The implementation method of step 3 is as follows: Step 31. Measure the methane bubble formation rate at the sediment-water interface, the methane diffusion formation rate at the sediment-water interface, and the methane oxidation rate in the water body; The methane concentration in sediment interstitial water was calculated as follows: ， In the formula, The concentration of methane in the interstitial water; To determine the headspace methane concentration in the culture flask, This refers to the volume of headspace gas in the culture flask. To determine the volume of interstitial water within the culture vessel, the methane diffusion flux at the sediment-water interface is calculated using Fick's first law, based on the difference in greenhouse gas concentration between the interstitial water in the sediment surface layer and the overlying water. This flux is the amount of substance that passes vertically through a unit area per unit time. The formula is as follows: ， In the formula, It is the gas diffusion flux at the sediment-water interface; It refers to the porosity of sediments; It is the correction curvature, expressed as ; It is the diffusion coefficient of methane in water as a function of temperature; It is the vertical gradient of dissolved gas concentration in the sediment; Step 32. Methane bubble transport flux was collected using an inverted funnel method positioned 10 cm from the sediment-water interface and calculated in time increments. The calculation formula is as follows: ， In the formula, It is the methane bubble transport flux. It refers to greenhouse gas concentration. It is the volume of gas collected. It is the area at the opening of the funnel. The time it takes for the funnel to set is... It is the standard volume of a gas; Step 33. Ten replicate water samples (120 mL each) were collected from both the deep and shallow water areas. In the laboratory, the bottles were incubated at a constant temperature of 5°C in the dark. The methane concentration in the sealed bottles was measured five times on days 1, 2, 3, 5, and 7, using the following formula: ， In the formula, It is the rate of methane oxidation in water. and These are the initial concentration and the concentration at t(h), respectively.
5. The method for measuring and calculating methane reserves in a reservoir in a frozen area according to claim 1, characterized in that, The implementation method of step 4 is as follows: Step 41. Calculation of freezing duration: the number of freezing days is the total number of days from the first day of freezing to the complete thawing, i.e., the entire freezing process, while the number of frozen days is the total number of days from the complete freezing of the entire reservoir area to the complete disappearance of the ice cover. Step 42. Changes in methane levels in the reservoir during the ice-bound period. The model basis for the generation amount is the parameters measured in the field during the ice-stable period. The data for bubble generation is obtained from the bottom methane bubble transport rate obtained by the inverted funnel. The data for diffusion generation is obtained from the sediment-water interface methane diffusion flux calculated from the concentration gradient between sediment interstitial water and bottom water. The model basis for the oxidation amount is obtained from the methane oxidation rate at 5℃ obtained from the simulation experiment. The change in methane reserves is calculated as the time elapsed from the ice-stable period to the ice melting time. Step 43. Methane reserves in reservoirs in ice-bound areas: The methane reserves in reservoirs in ice-bound areas are the sum of the current methane reserves in the reservoirs during the ice-stable period and the changes in methane reserves in the reservoirs during the ice-bound period.
6. A system for calculating methane reserves in reservoirs in ice-covered areas, characterized in that, include, The data collection module is used to collect observation data on the area, water depth, and sediment depth of the deep water area, shallow water bubble area, and shallow water non-bubble area of the reservoir during the ice-covered period. The correlation establishment module is used to establish the methane concentration in ice. Regarding the area density of ice-sealed bubbles The correlation; The module for calculating the methane reserves in sediments calculates the methane reserves in sediments in each section of the reservoir. The module for calculating the current amount of methane in the water body calculates the methane reserves in each section of the reservoir. The module for calculating the duration of ice cover combines the Stefan formula with the actual opening date of the reservoir to calculate the number of days the reservoir is frozen. The module for calculating methane changes in the reservoir combines the sediment bubble rate, sediment diffusion rate, and methane oxidation rate in the water body measured by simulation experiments to calculate the methane changes in the reservoir. The module for calculating methane reserves in reservoirs in ice-bound areas uses the existing methane levels in ice, water, and sediments, as well as the changes in methane levels in the reservoir, to calculate the total methane reserves in reservoirs in ice-bound areas.