A method for storing and utilizing water in a mining area covered by loess layer

Abstract

The present invention relates to a method for storing and utilizing water in a mining area covered with loess. The present invention mainly applies the following principles: First, the groundwater storage area is selected in the mining area, taking into account the groundwater impact radius of coal mining and the depth of coal mining floor damage, and the vertical and horizontal areas are determined. Second, in order to control the water quality, the actual soil and water loss in the loess area is taken into account, and a surface water storage system is adopted. Third, by using water replenishment drilling holes to limit the water storage height of the underground aquifer, the minimum distance between the selected groundwater storage area and the area where coal has been mined is determined. At the same time, the harm of the loess water level to the surface ecology and the safety issues of coal mines are taken into consideration. Fourth, since the water levels before and after replenishment are functions of time, the amount of available water resources is determined based on the first observation data and the second observation data, so as to replenish groundwater by collecting surface water, effectively improve the amount of available water resources in the mining area, and do not affect the ecological environment and coal mine safety production.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogeology and mining engineering, and in particular to a water storage and utilization method in a mining area covered with loess layers. Background Art

[0002] Loess-covered areas are rich in coal resources but lack water resources. Mining areas covered by loess layers generally lack usable water resources. Therefore, water storage and utilization methods in loess-covered mining areas are important for ensuring coal resource extraction. Previous methods to address this issue included water storage and supply in goafs, mine water recycling, and the establishment of water-retaining coal pillars. However, these methods generally suffer from the following problems:

[0003] (1) The goaf poses a great threat to adjacent coal seams due to the randomness of large rock collapse, and it is difficult to ensure safety after water storage.

[0004] (2) Due to the poor infiltration conditions in the loess-covered area, the underlying aquifers are generally poorly water-rich, and the amount of recycled mine water is limited, which cannot meet the water resource needs of the mining area.

[0005] (3) Surface water reservoirs can effectively store water resources, but due to the large amount of surface water evaporation and the pressure on coal resources, the efficiency of water resource utilization is low.

[0006] (4) The atmospheric precipitation in the loess-covered area is large, resulting in a large amount of ineffective runoff.

[0007] (5) Coal mining in loess-covered areas causes complex and changeable groundwater flows in mining areas. There is no accurate calculation of the amount of water stored and utilized, which can easily lead to over-exploitation of aquifers and damage to the groundwater system. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the present invention provides a method for storing and utilizing water in a mining area covered with a loess layer.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A method for storing and utilizing water in a loess-covered mining area, comprising:

[0011] Select groundwater storage areas within the mining area;

[0012] Observing groundwater parameters in the water storage area to obtain first observation data;

[0013] Arrange a surface water storage system upstream of the water storage area; the upstream refers to the section where the total amount of water collected by the loess layer ditch in the rainy season within the water storage area reaches a preset range;

[0014] Setting a water replenishment borehole at the surface water storage system;

[0015] After the water replenishment drilling hole stores water in the rainy season, observing groundwater parameters in the water storage area again to obtain second observation data; the groundwater parameters include water level and flow rate;

[0016] Drawing relationship curves between water level before and after water storage and time based on the first observation data and the second observation data;

[0017] Determine the amount of available water resources in each aquifer and loess layer in the water storage area based on the relationship curve;

[0018] When the mining area is in the dry season, water storage and utilization are carried out in the mining area based on the available water resources.

[0019] Preferably, it also includes:

[0020] When the available water resources in the water storage area cannot meet the needs of the mining area, the surface water storage system is dismantled, the water replenishment borehole is closed, and a new water storage area is selected.

[0021] Preferably, the selection conditions of the water storage area include:

[0022] There is no coal mining plan in the current area within the next two hydrological years, and the minimum distance from the mined coal is greater than the maximum drainage impact radius of the first aquifer within the range of 1.5D to 5D between the coal seam roof and floor;

[0023] There is at least one aquifer of weak or medium water-rich level within 1.5D to 5D below the mined coal seam; where D is the depth of damage to the coal seam mining floor.

[0024] Preferably, observing the groundwater parameters of the water storage area to obtain the first observation data specifically includes:

[0025] Determine the observation position; the observation position is each aquifer, loess layer and the bottom plate of the mined coal seam above the mined coal seam;

[0026] First observation data is obtained by continuously observing groundwater parameters for a specific time period on the first aquifer 1.5D below the observation position.

[0027] Preferably, the specific time period is not less than one hydrological year; the number of observation points is not less than 1 / km 2 .

[0028] Preferably, the preset range is 30% to 60%.

[0029] Preferably, the ground water storage system is provided with a debris interception net, a yellow mud filter net and a ground water storage low dam body from top to bottom according to the direction of water flow; wherein, the debris interception net allows water and suspended matter below 0.01 meters to pass through; the yellow mud filter net adopts a soft membrane; the preparation material of the soft membrane is a polymer woven fabric; the water storage low dam body is 0.5 to 1.5 meters higher than the river channel; the horizontal interval between the debris interception net, the yellow mud filter net and the ground water storage low dam body is 1 to 10 meters.

[0030] Preferably, the water supply borehole is arranged between the yellow mud filter and the ground water storage low dam; the distance between two adjacent water supply boreholes is 10 to 100 meters; the water supply borehole extends from the ground to the bottom plate of the first aquifer below 1.5D of the mined coal seam bottom plate; the water supply borehole is set as a variable flower pipe in the exposed loess layer section and each aquifer section, and the remaining sections are waterproof casings.

[0031] Preferably, the upper limit of the water storage capacity of the water replenishment borehole meets the following conditions:

[0032] Rainwater is fed into the loess layer and the aquifer through the water-feeding boreholes, and the feed is stopped when the water level of the loess layer rises to a depth of 3.5 to 5 meters.

[0033] The water levels of the aquifers below the loess layer after rising should decrease from top to bottom, and none of them should be higher than the water level in the loess layer;

[0034] The maximum height of water recharge of the first aquifer below 1.5D of the coal seam floor should be less than the coal seam floor;

[0035] The water level rise height of the aquifer with the largest flow rate should also be less than (X×C÷t÷Y)-C, where t is the time of one hydrological cycle, X is the minimum distance between the selected groundwater storage area in the mining area and the area where coal has been mined, C is the average water level of the aquifer with the maximum groundwater flow rate between the selected groundwater storage area in the mining area and the area where coal has been mined in one hydrological year, and Y is the maximum groundwater flow rate between the selected groundwater storage area in the mining area and the area where coal has been mined.

[0036] Preferably, the amount of water resources available in a certain aquifer is

[0037] Where t is the time of a hydrological cycle, f(H) is the functional relationship between the water level after recharge and time, f(h) is the functional relationship between the water level before recharge and time, S is the distribution area of the aquifer or loess layer, and μ is the water supply degree or elastic storage coefficient of the aquifer.

[0038] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0039] The water storage and utilization method for the loess-covered mining area provided by the present invention mainly uses the following principles: First, the groundwater storage area is selected in the mining area, taking into account the groundwater impact radius of coal mining and the depth of coal mining floor damage, and the vertical and horizontal areas are determined. Second, the problem of soil erosion in the loess area is taken into consideration, and the use of a surface water storage system can effectively control the water quality. Third, by using water replenishment drilling holes to limit the water storage height of the underground aquifer, the minimum distance from the selected groundwater storage area to the area where coal mining has already occurred is determined. At the same time, the harm of the excessively high loess water level to the surface ecology and the safety issues of coal mines are taken into consideration. Fourth, since the water levels before and after replenishment are functions of time, the amount of available water resources is determined based on the first observation data and the second observation data, so that the amount of available water resources in the mining area can be effectively increased by collecting surface water to replenish groundwater, without affecting the ecological environment and coal mine safety production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

[0041] Figure 1 This is a flow chart of the method for storing and utilizing water in a loess-covered mining area provided by the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The purpose of the present invention is to provide a method for storing and utilizing water in a mining area covered with loess layers, which has the advantages of being simple and easy to implement, effectively regulating the temporal unevenness of water resources, improving the utilization rate of water resources, having better control over the storage and utilization of water resources in the complex groundwater flow field of the mining area, controlling the damage to the groundwater system, storing the water in aquifers outside the coal mining area, posing little threat to coal mining, being safer, and not affecting the mining of coal resources.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, the present invention provides a method for storing and utilizing water in a loess-covered mining area, comprising:

[0046] Step 100: Select a groundwater storage area within the mining area. The selected groundwater storage area must meet two conditions: First, there must be no coal mining planned for the next two hydrological years, and the minimum distance X from existing coal mining areas must be greater than R. Second, there must be one or more weakly or moderately water-rich aquifers within 1.5D to 5D below the mined coal seam. R is the maximum dewatering radius of the first aquifer within 1.5D to 5D of the coal seam roof and floor, determined through pumping experiments. D is the depth of the coal seam floor failure, predicted by a fitting formula established through field measurements of similar coal mining faces.

[0047] Step 101: Observe groundwater parameters in the water storage area to obtain the first observation data. Before water storage, water level monitoring and groundwater flow velocity measurement shall be continuously carried out for at least one hydrological year for each aquifer above the mined coal seam, the loess layer, and the first aquifer 1.5D below the bottom of the mined coal seam. The number of water level monitoring points shall be no less than 1 / km 2 The maximum groundwater flow rate measured is Y, and the average water level of the aquifer with the maximum groundwater flow rate is C.

[0048] Step 102: Deploy a surface water storage system upstream of the water storage area. The upstream section refers to the area within the water storage area where the total rainy season water catchment in the loess layer reaches 30% to 60%. The surface water storage system consists of a debris interception net, a mud filter, and a low surface water storage dam, arranged from top to bottom in the direction of water flow. The debris interception net only allows the passage of water and suspended solids below 0.01 meters. The mud filter uses a flexible membrane made of a polymer woven fabric. The mud filter is permeable to water but blocks the influx of small suspended solids and some mud. The low surface water storage dam is 0.5 to 1.5 meters higher than the river channel and has gentle slopes on both sides. The debris interception net, mud filter, and low surface water storage dam are spaced 1 to 10 meters apart horizontally.

[0049] Step 103: Install water replenishment boreholes in the surface water storage system. These are located between the loess filter and the low surface water storage dam. The distance between adjacent water replenishment boreholes is 10 to 100 meters. The water replenishment boreholes extend from the surface to the floor of the first aquifer below 1.5D below the mined coal seam floor. The exposed loess and aquifer sections of the water replenishment boreholes are equipped with variable-flow pipes, while the remaining sections are waterproof casings. The variable-flow pipes can be manually adjusted on the surface to control the water permeability or waterproofing of the corresponding loess or aquifer.

[0050] Step 104: After the recharge boreholes are filled during the rainy season, groundwater parameters are again observed in the water storage area to obtain second observation data. Groundwater parameters include water level and flow rate. The upper limit of the recharge borehole water storage is subject to the following four conditions: First, rainwater recharges the loess layer and aquifer through the recharge boreholes, and recharge stops when the loess layer water level rises to a depth of 3.5 to 5 meters. Second, the water levels of the aquifers below the loess layer should decrease from top to bottom and should not exceed the water level in the loess layer. Third, the maximum recharge height of the first aquifer below 1.5D of the mined coal seam floor should be lower than the coal seam floor. Fourth, the water level rise in the aquifer with the highest flow rate must be less than (X × C ÷ t ÷ Y) - C, where t is the duration of a hydrological cycle, X, C, and Y are the minimum distance between the selected groundwater storage area and the mined area, the average water level of the aquifer with the highest flow rate over one hydrological year, and the maximum groundwater flow rate measured in step 2. Recharge of each aquifer and loess layer is achieved using the variable flower pipes described in step 4, with recharge occurring in descending order from the top of the strata.

[0051] Step 105: Draw relationship curves between the water level before and after water storage and time based on the first observation data and the second observation data.

[0052] Step 106: Determine the available water resources in each aquifer and loess layer in the water storage area based on the relationship curve. For example, the available water resources in a certain aquifer are Where t is the time of a hydrological cycle, f(H) is the functional relationship of the water level after recharge with respect to time, f(h) is the functional relationship of the water level before recharge with respect to time, S is the distribution area of the aquifer or loess layer, and μ is the water supply degree or elastic water storage coefficient of the aquifer. When the aquifer is phreatic, μ is the water supply degree, and when the aquifer is confined water, μ is the elastic water storage coefficient.

[0053] Step 107: When the mining area is in the dry season, the mining area uses water based on the available water resources. For example, water is used sequentially from bottom to top until the water resource reaches Q in the corresponding stratum. The water stored in the loess is utilized using electroosmosis based on water replenishment drilling.

[0054] As coal is mined, if the groundwater storage area selected in step 100 does not meet the conditions, the surface water storage system in step 102 is dismantled, the water replenishment borehole in step 103 is sealed, and a new water storage area is reselected until there is no new water storage area that meets the conditions.

[0055] The loess-covered mining area has a huge amount of atmospheric precipitation during the rainy season, but the infiltration water resources are very limited, which causes the loss of water resources in the mining area. The present invention designs a water storage and utilization method for a loess-covered mining area in an unmined coal area, mainly using the following principles. First, the groundwater storage area is selected in the mining area, taking into account the groundwater impact radius of coal mining and the depth of coal mining floor damage, and the vertical and horizontal areas are determined. Second, considering the problem of soil and water loss in the loess area, a combined filtration method such as a fragment interception net and a soft membrane material is used to effectively control the water quality. Third, combined with Darcy's law, it is calculated that the groundwater loss rate increases under the combined effects of coal mining and water storage. Therefore, by limiting the water storage height of the underground aquifer, the minimum distance from the selected groundwater storage area to the area where coal mining has already occurred is determined. At the same time, the harm of excessively high loess water levels to the surface ecology and the safety issues of coal mines are taken into consideration. Fourth, since the water levels before and after recharge are functions of time, the integral method can be used to calculate the amount of available water resources Q. In summary, by collecting surface water to replenish groundwater, the amount of available water resources in the mining area has been effectively increased without affecting the ecological environment and coal mine safety production.

[0056] An example is provided below to illustrate the specific implementation process of the method for storing and utilizing water in a loess-covered mining area provided by the present invention.

[0057] A coal mine is located in a loess-covered mining area, where precipitation infiltration is very limited, and available water resources are very limited. While measures such as goaf water storage are being adopted, goaf water poses a potential threat to production mines, and as the loess heals, water resources in the goaf become unavailable. Therefore, an artificial water storage and utilization strategy has been implemented using aquifers in unmined areas. The specific steps are as follows:

[0058] Step 1: Select a groundwater storage area in the mining area. The selected groundwater storage area must meet the following two conditions: First, there is no coal mining plan in the next two hydrological years, and the minimum distance X (X = 500) meters from the existing coal mining area should be greater than R (R = 388) meters. Second, there is an aquifer with a weak water-rich level within 1.5 to 5D (D = 13.02) meters below the mined coal seam. R is determined through pumping experiments. D is the depth of the coal seam mining floor failure. It is predicted by a fitting formula established through field measurements of similar coal mining working faces. The fitting formula is D = 9.26 + 0.71lnL, where L is the inclined length of the working face, which is 200 meters here, and D can be calculated as 13.02 meters.

[0059] Step 2: Before water storage, conduct water level monitoring and groundwater flow rate measurement for each aquifer above the mined coal seam, the loess layer, and the first aquifer 1.5D below the bottom of the mined coal seam for more than one hydrological year in the water storage area selected in step 1. The density of water level monitoring points shall not be less than 1 / km 2The maximum groundwater flow rate measured was Y = 0.92 m / day, and the average water level of the aquifer with the maximum groundwater flow rate was C = 18.8 m.

[0060] Step 3: Deploy a surface water storage system upstream of the loess precipitation catchment area in the selected water storage area. This refers to the section of the loess channel that receives 42% of its total rainy season water. The surface water storage system consists of a debris interception net, a mud filter, and a low surface water storage dam, arranged in descending order of flow. The debris interception net only allows the passage of water and suspended solids below 0.01 meters. The mud filter utilizes a flexible membrane, a polymer woven material that is permeable to water but allows the inflow of small suspended solids and some mud. The low water storage dam is 1.0 meter higher than the riverbed and has gentle slopes on both sides. The horizontal spacing between the debris interception net, mud filter, and low surface water storage dam ranges from 1 to 10 meters.

[0061] Step 4: Set up underground stratum water replenishment boreholes for the rainy season at the surface water storage system set up in the selected water storage area. The water replenishment boreholes are arranged between the loess filter and the surface water storage low dam. The distance between adjacent water replenishment boreholes is 50 meters. The water replenishment boreholes extend from the ground to the bottom of the first aquifer below 1.5D below the mined coal seam floor. The water replenishment boreholes are equipped with variable flower pipes in the exposed loess sections and each aquifer section, and the remaining sections are waterproof casings. The variable flower pipe means that the corresponding loess or aquifer can be manually adjusted on the ground to control the water permeability to waterproof effect.

[0062] Step 5: Use recharge boreholes to store water during the rainy season. The upper limit of recharge borehole water storage is subject to the following four conditions: First, rainwater must recharge the loess layer and aquifer through the recharge boreholes, and recharge must cease when the loess water level rises to a depth of 4 meters. Second, the water levels of each aquifer below the loess must decrease from top to bottom and never exceed the water level in the loess. Third, the maximum recharge height of the first aquifer below 1.5D below the mined coal seam floor must be lower than the coal seam floor. Fourth, the water level rise of the aquifer with the highest flow rate determined in Step 2 must be less than (X × C ÷ t ÷ Y) - C = 9.19 meters, where t = 365 days, X = 500 meters, C = 18.8 meters, and Y = 0.92 meters / day. Recharge of each aquifer and loess layer is achieved using the variable flower pipes described in Step 4, with recharge occurring in the order of the strata from top to bottom.

[0063] Step 6: After the borehole is filled with water, continue with the water level monitoring in step 2.

[0064] Step 7: Based on the monitoring results of steps 2 and 6, draw the relationship curve between water level and time before and after water storage.

[0065] Step 8: Based on the relationship curves from Step 7, calculate the available water resources in each aquifer and loess. The available water resources in a particular aquifer are Q. The detailed calculation process is described above and will not be repeated here.

[0066] Taking the first aquifer below 1.5D of the coal seam floor as an example, h=-0.0008t is obtained by fitting the observed data. 2 +0.2706t+6.875, H=-0.0009t 2 +0.3086t+9.75, Q=240,000 cubic meters.

[0067] Step 9: During the dry season, begin utilizing the water stored in the mining area during the rainy season. Utilize water from bottom to top, until the amount utilized reaches the Q of the corresponding stratum. The water stored in the loess is utilized through electroosmosis, using water-replenishing boreholes.

[0068] Step 10: With the mining of coal, if the groundwater storage area selected in step 1 does not meet the conditions, the surface water storage system in step 3 will be dismantled and the water replenishment borehole in step 4 will be sealed.

[0069] The above steps have produced a total of 2.29 million cubic meters of usable water resources from multiple aquifers and loess layers over a two-year period. The water resources have been utilized without causing any degradation to the ecological environment of the mining area.

[0070] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0071] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for storing and utilizing water in a loess-covered mining area, characterized in that: include: Select groundwater storage areas within the mining area; Observing groundwater parameters in the water storage area to obtain first observation data specifically includes: determining an observation location; continuously observing groundwater parameters for a specific time period on the first aquifer 1.5D below the observation location to obtain the first observation data; the observation location is each aquifer, loess layer, and the floor of the mined coal seam above the mined coal seam; the specific time period is no less than one hydrological year; and D is the damage depth of the coal seam floor; Arrange a surface water storage system upstream of the water storage area; the upstream refers to the section where the total amount of water collected by the loess layer ditch in the rainy season within the water storage area reaches a preset range; Setting a water replenishment borehole at the surface water storage system; After the water replenishment drilling hole stores water in the rainy season, observing groundwater parameters in the water storage area again to obtain second observation data; the groundwater parameters include water level and flow rate; Drawing relationship curves between water level before and after water storage and time based on the first observation data and the second observation data; Determine the amount of available water resources in each aquifer and loess layer in the water storage area based on the relationship curve; When the mining area is in the dry season, water storage and utilization are carried out in the mining area based on the available water resources.

2. The method for storing and utilizing water in a loess-covered mining area according to claim 1, characterized in that: Also includes: When the available water resources in the water storage area cannot meet the needs of the mining area, the surface water storage system is dismantled, the water replenishment borehole is closed, and a new water storage area is selected.

3. The method for storing and utilizing water in a loess-covered mining area according to claim 1, wherein: The selection conditions of the water storage area include: There is no coal mining plan in the current area within the next two hydrological years, and the minimum distance from the mined coal is greater than the maximum drainage impact radius of the first aquifer within the range of 1.5D to 5D between the coal seam roof and floor; There is at least one aquifer with a weak or medium water-rich level within 1.5D to 5D below the mined coal seam.

4. The method for storing and utilizing water in a loess-covered mining area according to claim 1, wherein: The number of observation points is not less than 1 / km 2 .

5. The method for storing and utilizing water in a loess-covered mining area according to claim 1, characterized in that: The preset range is 30% to 60%.

6. The method for storing and utilizing water in a loess-covered mining area according to claim 1, characterized in that: The surface water storage system is provided with a debris interception net, a yellow mud filter net and a surface water storage low dam body from top to bottom according to the direction of water flow; wherein, the debris interception net allows water and suspended matter below 0.01 meters to pass through; the yellow mud filter net adopts a soft membrane; the preparation material of the soft membrane is a polymer woven fabric; the surface water storage low dam body is 0.5 to 1.5 meters higher than the river channel; the horizontal interval between the debris interception net, the yellow mud filter net and the surface water storage low dam body is 1 to 10 meters.

7. The method for storing and utilizing water in a loess-covered mining area according to claim 6, characterized in that: The water supply borehole is arranged between the yellow mud filter and the ground water storage low dam; the distance between two adjacent water supply boreholes is 10 to 100 meters; the water supply borehole extends from the ground to the bottom plate of the first aquifer below 1.5D of the mined coal seam bottom plate; the water supply borehole is set as a variable flower pipe in the exposed loess layer section and each aquifer section, and the remaining sections are waterproof casings.

8. The method for storing and utilizing water in a loess-covered mining area according to claim 1, wherein: The upper limit of water storage in the water replenishment borehole meets the following conditions: Rainwater is fed into the loess layer and the aquifer through the water-feeding boreholes, and the feed is stopped when the water level of the loess layer rises to a depth of 3.5 to 5 meters. The water levels of the aquifers below the loess layer after rising should decrease from top to bottom, and none of them should be higher than the water level in the loess layer; The maximum height of water recharge of the first aquifer below 1.5D of the coal seam floor should be less than the coal seam floor; The water level rise height of the aquifer with the largest flow rate should also be less than (X×C÷t÷Y)-C, where t is the time of one hydrological cycle, X is the minimum distance between the selected groundwater storage area in the mining area and the area where coal has been mined, C is the average water level of the aquifer with the maximum groundwater flow rate between the selected groundwater storage area in the mining area and the area where coal has been mined in one hydrological year, and Y is the maximum groundwater flow rate between the selected groundwater storage area in the mining area and the area where coal has been mined.

9. The method for storing and utilizing water in a loess-covered mining area according to claim 1, characterized in that: The amount of water resources available in a certain aquifer is Where t is the time of a hydrological cycle, f(H) is the functional relationship between the water level after recharge and time, f(h) is the functional relationship between the water level before recharge and time, S is the distribution area of the aquifer or loess layer, and μ is the water supply degree or elastic storage coefficient of the aquifer.

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