A seepage flow meter for determining the exchange amount of coastal groundwater-surface water

Abstract

The application discloses a permeation flow meter for determining the exchange amount of coastal groundwater-surface water, and relates to the technical field of measuring instruments.The permeation flow meter comprises a permeation chamber, a water tank joint, an elbow, a hose, a pipe sleeve, a ball valve and a water storage bag.The permeation chamber is composed of a barrel, the barrel top is provided with the water tank joint, the water tank joint is connected with the hose through the elbow, the hose is movably connected with the ball valve, and the ball valve is sealingly connected with the water storage bag through the pipe sleeve.The water storage bag forms an independent sealing unit when the ball valve is closed, and the water storage bag is in communication with the inside of the barrel when the ball valve is opened.The barrel bottom is inserted into the water bottom sediment to form a sealing contact.The present application reduces the water head loss through a large-diameter connecting piece, reduces the deformation resistance by using a thin-walled water storage bag, adapts to the tidal environment by using a flexible hose, and determines the optimal waiting time and the optimal correction coefficient through indoor sand tank simulation experiments, thereby significantly improving the measurement accuracy and the reliability of field work.

Description

Technical Field

[0001] This invention relates to the field of measuring instrument technology, and in particular to a permeation flow meter for measuring the exchange rate of groundwater and surface water in coastal zones. Background Technology

[0002] The exchange between surface water and groundwater is a crucial factor influencing the formation and structural characteristics of regional water resources. Scientifically determining the amount of exchange between groundwater and surface water has become a hot research topic both domestically and internationally. Current methods for investigating groundwater-surface water exchange mainly include hydrodynamic methods, isotope methods, and permeameter methods. Among these, the permeameter method can directly measure the amount of exchange at the groundwater-surface water interface. Previous studies have shown that factors such as the material of the collection bag and the diameter of the permeameter can affect the measurement results, but these studies are mainly limited to indoor simulation experiments. This patent describes the design and fabrication of a set of permeameters. A sand tank simulation test system was used to determine the influence of seepage time and the size of the permeameter on the seepage flow rate, and an interface water exchange correction coefficient was determined. Field measurements of groundwater and surface water seepage flow in the coastal zone were conducted, achieving excellent results. This has significant scientific and application value for water resource development, utilization, and protection.

[0003] Traditional percolator flowmeters often suffer from significant errors due to poor sealing, loose contact with sediments, uncertain seepage waiting times after insertion into bottom sediments, small diameter at the connection between the water storage bag and the seepage chamber affecting measurement, and rupture caused by water storage bag quality issues or aquatic organism activity. To address these problems, this invention utilizes indoor experimental design to determine a reasonable seepage waiting time and a calibration coefficient for the percolator. Furthermore, the design of the hose and connectors is adaptable to various tidal variations along the coast, effectively reducing errors and enabling direct in-situ measurement of groundwater-surface water exchange in coastal areas. Summary of the Invention

[0004] This application provides a permeate flow meter for measuring the exchange rate between groundwater and surface water in coastal zones, which solves the problems of insufficient sealing and unclear measurement timing in existing permeate flow meter systems, thereby achieving the technical effects of improving measurement accuracy, ensuring the reliability of operational data, and improving work efficiency.

[0005] This application provides a permeation flow meter for measuring the exchange rate between groundwater and surface water in coastal zones. The permeation flow meter includes: a permeation chamber, a water tank connector, an elbow, a hose, a pipe sleeve, a ball valve, and a water storage bag. The infiltration chamber is composed of a cylindrical barrel, with an installation hole at the center of the top of the barrel. The water tank connector is fixedly installed in the installation hole. The upper end of the water tank connector is connected to one end of the elbow, and the other end of the elbow is connected to one end of the hose. The other end of the hose is movably connected to one end of the ball valve, and the other end of the ball valve is sealed to the opening of the water storage bag through the sleeve to form a sealed structure. When the ball valve is closed, the water storage bag is disconnected from the hose, and the water storage bag forms an independent sealing unit; When the ball valve is opened, the water storage bag is connected to the internal space of the barrel through the hose, the elbow, and the water tank connector; the bottom edge of the barrel is used to insert into the sediment at the bottom of the water, and the barrel and the sediment form a sealed contact through the weight of the sediment.

[0006] Furthermore, the diameter of the cylindrical container is 28cm and the height is 15cm; the volume of the water storage bag is 4L and the wall thickness of the water storage bag does not exceed 0.3mm.

[0007] Furthermore, the inner diameter of the water tank connector and the hose are the same, both set to 12mm.

[0008] Furthermore, the water storage bag is pre-filled with 500 to 1000 mL of water before connection, and the air inside the water storage bag is completely emptied, with the pre-filled water volume not exceeding 75% of the volume of the water storage bag.

[0009] Furthermore, when the ball valve is closed, the water storage bag is disconnected from the hose, and the water storage bag forms an independent sealing unit, maintaining a sealed state during movement, weighing, or replacement.

[0010] Furthermore, an indoor sand bath simulation experiment was conducted using the aforementioned permeation flow meter. The experimental method is as follows: S1: Construct a sand trough simulation experimental system. Based on the experiment, determine the optimal thickness of the water storage bag. Spread gravel with a height of 10cm evenly at the bottom of the sand trough. The gravel should bury the water distribution pipe without blocking the water outlet on the water distribution pipe. Spread a stainless steel screen with a aperture of 0.1mm on top of the gravel. Fill the stainless steel screen with sand using the wet filling method. Compact the sand with a wooden mallet every 3cm of sand filling, for a total of 30cm. S2: Use a constant head device to continuously pass water from the bottom of the sand tank for 8 hours to rinse the fine particles. Then, use a water pump to pump the water out of the sand tank into the constant head device to form a water circulation. Run continuously for 2 days to remove air bubbles from the sand layer. S3: Slowly insert the permeate flow meter into the sand layer of the sand tank to a depth of 10cm, continue to supply water at a constant head for 24 hours, and then conduct an indoor calibration experiment. Change the waiting time, seepage velocity and seepage direction, measure the seepage velocity under different conditions, and determine the optimal waiting time and calibration coefficient.

[0011] Furthermore, determining the optimal waiting time includes: The infiltration flow rate in the sand tank was controlled at 20 cm / d, and the flow rate measured by the infiltration flow meter was measured after different waiting times of 5 min, 10 min, 15 min, 20 min, 30 min, and 45 min. When the waiting time was 5 minutes, the measured flow rate was 12.3 cm / d with a relative error of 38.5%; when the waiting time was 10 minutes, the measured flow rate was 15.8 cm / d with an error of 21.0%; when the waiting time was 15 minutes, the measured flow rate was 17.5 cm / d with an error of 12.5%; when the waiting time was 20 minutes, the measured flow rate was 18.2 cm / d with an error of 9.0%; when the waiting time was 30 minutes, the water storage bag was close to saturation, and the measured flow rate began to decrease; 20 minutes was determined as the optimal waiting time.

[0012] Furthermore, the optimal thickness of the water storage bag was determined experimentally, including: testing with three different wall thicknesses: thin-walled, conventional, and thick-walled bags, with wall thicknesses of 0.2 mm, 0.5 mm, and 1.0 mm, respectively; comparative measurements were conducted under the same sand tank infiltration flow rate of 20 cm / d and a waiting time of 20 min; the experimental results showed that when the water storage bag wall thickness was 0.2 mm, the instrument measured a flow rate of 18.2 cm / d, with a working efficiency of 0.91 and a relative error of 9.0%; when the wall thickness increased to 0.5 mm... When the wall thickness increased to 1.0 mm, the measured flow velocity dropped to 16.5 cm / d, the working efficiency decreased to 0.825, and the relative error increased to 17.5%. When the wall thickness further increased to 1.0 mm, the measured flow velocity was only 13.8 cm / d, the working efficiency dropped to 0.69, and the relative error was as high as 31.0%. When the wall thickness increased from 0.2 mm to 1.0 mm, the working efficiency decreased from 0.91 to 0.69, and the measurement error increased by 22 percentage points. The wall thickness of the water storage bag does not exceed 0.3 mm, minimizing the impact of bag deformation resistance on measurement accuracy.

[0013] One or more technical solutions provided in this application have at least the following technical effects or advantages: By systematically optimizing the structure of the permeation flow meter, a cylindrical container with a diameter of 28 cm and a height of 15 cm was used to construct the permeation chamber, ensuring large-area contact and good sealing with the sediment. A water tank connector and hose with an inner diameter of 12 mm were used to effectively avoid head loss caused by traditional small-diameter pipes. The water storage bag was made of a thin-walled material with a wall thickness not exceeding 0.3 mm. Comparative experiments verified that as the wall thickness increased from 0.2 mm to 1.0 mm, the working efficiency decreased from 0.91 to 0.69, and the measurement error increased by 22 percentage points. Therefore, the thin-walled material was selected to minimize the bag's deformation resistance. Based on this, a universal correction coefficient was determined through indoor sand tank simulation experiments to correct the remaining system deviations. Due to the dual guarantee of the above structural optimization and correction coefficients, the final measurement results closely approximate the true value, effectively solving the technical problem of large measurement errors in traditional instruments.

[0014] Through systematic indoor sand tank simulation experiments, the optimal waiting time was scientifically determined to be 20 minutes. This ensures that the seepage flow tends to stabilize while reserving sufficient safety volume. It avoids failures caused by improper measurement timing and ensures that each measurement is conducted under relatively stable seepage conditions, making the data more representative and comparable.

[0015] By replacing traditional rigid tubing with flexible hoses, the instrument is designed to withstand the cyclical rise and fall of water levels in coastal tidal environments. The hoses passively adapt to these fluctuations and flow direction changes, absorbing the pulling force of tidal currents and maintaining overall instrument stability. In continuous operation tests simulating tidal fluctuations (water level variation ±0.5m, period 12h), the instrument using flexible hoses showed no connection detachment or seal failure within 7 days, while the control group using rigid tubing exhibited loose connections and leakage on the 3rd day. Furthermore, the ball valve and water storage bag form a permanent sealed connection via a tubing sleeve. When the ball valve is closed, the water storage bag becomes an independent sealed unit, preventing water leakage and air ingress during movement, weighing, or replacement. Additional protective plastic bags can be added, significantly improving the reliability and convenience of fieldwork. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the experimental apparatus for measuring the exchange rate of groundwater and surface water in coastal zones, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a permeation flow meter for measuring the exchange rate of groundwater and surface water in coastal zones, as described in an embodiment of the present invention. The attached diagram is labeled as follows: 1. Infiltration chamber; 2. Circular barrel; 3. Water tank connector; 4. Elbow; 5. Hose; 6. Pipe sleeve; 7. Ball valve; 8. Water storage bag; 9. Sand trough; 10. Gravel; 11. Water outlet; 12. Stainless steel screen; 13. Constant head device; 14. Water pump; 15. Infiltration flow meter. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] Example 1: As Figure 1 As shown, a permeation flow meter for measuring the exchange rate of groundwater and surface water in coastal zones is provided. The permeation flow meter 15 includes: a permeation chamber 1, a water tank connector 3, an elbow 4, a hose 5, a pipe sleeve 6, a ball valve 7, and a water storage bag 8. The infiltration chamber 1 is composed of a cylindrical barrel 2. A mounting hole is provided at the center of the top of the cylindrical barrel 2. The inner diameter of the mounting hole is 12mm, which is the same as the inner diameter of the hose 5. The water tank connector 3 is fixedly installed in the mounting hole. The upper end of the water tank connector 3 is connected to one end of the elbow 4, and the other end of the elbow 4 is connected to one end of the hose 5. The other end of the hose 5 is movably connected to one end of the ball valve 7. The other end of the ball valve 7 is sealed to the opening of the water storage bag 8 through the sleeve 6 to form a sealed structure. When the ball valve 7 is closed, the water storage bag 8 is disconnected from the hose 5, and the water storage bag 8 forms an independent sealing unit; when the ball valve 7 is open, the water storage bag 8 is connected to the internal space of the cylindrical barrel 2 through the hose 5, the elbow 4, and the water tank connector 3. The bottom edge of the cylindrical barrel 2 is used to insert into the sediment at the bottom of the water, and the cylindrical barrel 2 and the sediment form a sealed contact through the weight of the sediment.

[0020] In some embodiments, the cylindrical barrel 2 serves as the contact and collection unit of the entire device. It is cut from a 20kg waterproof coating barrel, with a diameter of 28cm and a height of 15cm, ensuring the barrel's sealing and structural strength. The water storage bag 8 is made of thin-walled material (4L volume) to reduce deformation resistance. Before measurement, a certain amount of water (usually 500-1000mL, adjustable according to flow direction, but not exceeding 75% of the volume) needs to be pre-filled and the air removed.

[0021] In the measuring device of this application, when the ball valve 7 is closed, the water storage bag 8 becomes an independent, sealed unit. During movement, weighing, or replacement, the water inside the bag will not leak, and external air will not enter, ensuring the accuracy of the measurement and the convenience of operation.

[0022] Based on the flow meter in this application, an indoor sand tank simulation experimental device is also provided, such as... Figure 2 As shown, the experimental apparatus includes a sand tank 9, gravel 10, a water outlet 11, a stainless steel screen 12, a constant head device 13, a water pump 14, and a permeation flow meter 15.

[0023] In some embodiments, the following operating method is provided based on the above-described permeation flow meter 15 and indoor sand tank 9 simulation experimental apparatus: S1: Evenly spread gravel 10 to a height of about 10cm at the bottom of the sand trough 9, ensuring that the water distribution pipe is buried but not blocked by the water outlet 11 on the water distribution pipe. Lay a stainless steel screen 12 with a 0.1mm aperture on top of the gravel to prevent fine sand from moving downwards and blocking the water outlet 11. Then, fill the sand sample using the wet filling method, that is, fill the sand sample and water at the same time. After filling every 3cm of sand layer, compact it with a wooden mallet to ensure that the sand layer density is uniform. Repeat this process for a total of 30cm. S2: After the sand sample is filled, water is continuously circulated from the bottom of the sand tank 9 for 8 hours using the constant head device 13 to wash away fine particles. After the sand tank 9 is clear, the water from the sand tank 9 is pumped into the constant head device 13 by the water pump 14, which then supplies water to the sand tank 9 to circulate the water. This process is repeated for 2 days to allow the sand tank 9 to stabilize and remove any air bubbles that may exist in the sand layer. During this period, the permeate flow meter 15 is not used for measurement. S3: After removing air bubbles and fine particles from the sand trough, slowly insert two 28cm diameter permeate flow meters 15 into the sand layer of the sand trough 9 to a depth of 10cm. Continue to supply water at a constant head for 24 hours. After the water flow in the sand trough 9 stabilizes, begin the indoor calibration experiment of the permeate flow meters 15 to calculate the permeation velocity between groundwater and surface water. Repeat the measurement three times to calculate the average permeation velocity. Then calculate the working efficiency of the permeate flow meters 15. The calibration coefficient of the permeate flow meters 15 is the reciprocal of its working efficiency.

[0024] The indoor calibration experiment is as follows: A full-factor sand tank 9 seepage test is conducted by changing the waiting time, seepage velocity, and seepage direction. During the seepage process, two permeability flow meters 15 are used simultaneously to measure the seepage velocity. Before measurement, a water storage bag 8 is pre-filled with a volume V1 of water. After purging the air from the water storage bag 8, the ball valve 7 is closed and connected to the hose 5. The ball valve 7 is immediately opened to begin measurement. After the waiting time, the ball valve 7 is closed, the water storage bag 8 is removed, and the volume of water in the water storage bag 8 is measured using a graduated cylinder and recorded as V2. The seepage velocity between groundwater and surface water is calculated. When the calculated value is positive, it indicates that the seepage direction is upward, and groundwater recharges surface water. Conversely, if the value is negative, it indicates that the seepage direction is downward, i.e., surface water recharges groundwater. The calculation formula is as follows: ; in, Q is the infiltration velocity between groundwater and surface water; A is the exchange rate per unit time; T is the cross-sectional area of ​​infiltration chamber 1; V1 is the waiting time; V2 is the volume of pre-filled water; and V2 is the volume of water in storage bag 8 after measurement.

[0025] Repeat the measurement three times and calculate the average permeation velocity. Calculate the operating efficiency of the permeation flow meter 15; the correction factor for the permeation flow meter 15 is the reciprocal of its operating efficiency. The calculation formula is as follows: ; ; in, It is the average permeation velocity; This represents the actual infiltration velocity in the sand tank. To improve the working efficiency of the permeate flow meter; This is the correction factor.

[0026] In some embodiments, different seepage waiting times have different effects on the results. The head height is adjusted, and the seepage velocity in the sand trough 9 is controlled at 20 cm / d. The working efficiency of the seepage flow meter 15 is measured and calculated under different waiting times. Then, the head height is changed, and the seepage velocity in the sand trough 9 is controlled successively at 200 cm / d, -20 cm / d, and -200 cm / d, and measurements are performed. When groundwater recharges surface water, abnormal water flow has a greater impact on the measurement results when the waiting time is short. When the waiting time increases, the average seepage velocity is more stable. An excessively long waiting time will cause the water storage bag 8 to reach saturation, thus preventing groundwater from entering the water storage bag 8 through the seepage chamber 1, leading to measurement failure. When surface water recharges groundwater, a waiting time that is too short will result in a large measurement error and inaccurate measurement results, while a waiting time that is too long will cause the pre-filled water in the water storage bag 8 to drain, leading to measurement failure.

[0027] In some embodiments, taking upward seepage (groundwater recharges surface water) as an example, when the seepage velocity in the sand tank 9 is 20 cm / d, experimental data shows that: after a waiting time of 5 minutes, the measured velocity is 12.3 cm / d with a relative error of 38.5%; after 10 minutes, it is 15.8 cm / d with an error of 21.0%; after 15 minutes, it is 17.5 cm / d with an error of 12.5%; after 20 minutes, it is 18.2 cm / d with an error of 9.0%; and after 30 minutes, it is 18.0 cm / d. However, at this time, the water storage bag 8 is already close to saturation (the water storage capacity reaches 3.8 L, accounting for 95% of the volume). If the waiting time is extended to 45 minutes, the water storage bag 8 will be completely saturated, the water flow will stop, and the measured velocity will drop sharply to 5.2 cm / d. Therefore, 20 minutes is determined to be the optimal waiting time. This time point ensures that the seepage tends to stabilize and also reserves sufficient safety volume (saturation of about 75%) to avoid measurement failure due to saturation or emptying.

[0028] In some embodiments, determining the correction coefficient of the permeate flow meter includes: setting the waiting time for measurement to 20 minutes, adjusting the head height, and controlling the permeate flow rate of the sand tank 9 to be 5 cm / d, 10 cm / d, 20 cm / d, 25 cm / d, 50 cm / d, 100 cm / d, 150 cm / d, and 200 cm / d, respectively, to obtain the relationship between the permeate flow rate measured by the permeate flow meter 15 and the actual permeate flow rate of the sand tank 9. The influence of changing the sand tank permeate velocity on the accuracy of the measurement results of the permeate flow meter 15 is considered a basic error, and its impact on the final result can be ignored. Based on the measurement results, the correction coefficient of the permeate flow meter 15 is calculated to be between 1.06 and 1.20, and the comprehensive calculation yields a correction coefficient of 1.10 for the permeate flow meter 15.

[0029] As a preferred option, the calibration coefficient of the permeation flow meter is accurately determined through indoor tests. A calibration coefficient between 1.00 and 1.10 indicates a high-efficiency permeation flow rate.

[0030] In some embodiments, a well-sealed cylindrical barrel 2 is selected. During installation, the seal between the permeation flow meter 15 and the sediment must be ensured. If the permeation flow meter 15 is not placed securely and leaks, mud is needed to help fix the bottom of the permeation flow meter 15. If the sediment at the bottom is too loose to support the weight of the permeation flow meter 15, a higher permeation flow meter 15 needs to be selected according to the actual situation so that it can be inserted deeper and more stably into the sediment.

[0031] In some embodiments, after the sediment is inserted into the infiltration chamber 1, the water storage bag 8 needs to be connected to the infiltration chamber 1 to measure the infiltration flow rate. The connecting hose 5 and connector 4 directly affect the measurement results. If the diameter at the interface is too small, it will cause head loss. Water entering or flowing out of the bag will be subject to certain resistance, affecting the measurement. In addition, the thickness of the bag also has a certain impact on the water flow. Thick-walled bags will generate greater resistance during contraction and expansion. Before connecting the water storage bag 8 to the infiltration chamber 1, the air needs to be expelled to avoid the gas in the water storage bag 8 generating buoyancy that affects the measurement.

[0032] In some embodiments, the effect of wall thickness was quantified through comparative experiments: three types of water storage bags 8 with different wall thicknesses were used for testing: thin-walled, conventional, and thick-walled types, with wall thicknesses of 0.2 mm, 0.5 mm, and 1.0 mm, respectively. Comparative measurements were performed under the same sand tank 9 conditions: a permeation flow rate of 20 cm / d and a waiting time of 20 min. The experimental results showed that when the wall thickness of the water storage bag 8 was 0.2 mm, the instrument measured a flow rate of 18.2 cm / d, with a working efficiency of 0.91 and a relative error of 9.0%. When the wall thickness increased to 0.5 mm, the measured flow rate decreased to 16.5 cm / d, the working efficiency decreased to 0.825, and the relative error increased to 17.5%. When the wall thickness further increased to 1.0 mm, the measured flow rate was only 13.8 cm / d, the working efficiency decreased to 0.69, and the relative error reached as high as 31.0%.

[0033] Experimental results show that when the wall thickness increases from 0.2 mm to 1.0 mm, the working efficiency decreases from 0.91 to 0.69, and the measurement error increases by 22 percentage points. Therefore, this application preferably uses a thin-walled water storage bag 8 with a wall thickness not exceeding 0.3 mm to minimize the impact of bag deformation resistance on measurement accuracy.

[0034] In some embodiments, residual air inside the water storage bag 8 forms an air cavity at the top of the bag, creating a buoyancy effect. When water flows into the water storage bag 8, the air cavity is compressed, generating additional reverse pressure that hinders water flow; when water flows out, the air cavity expands, generating suction and accelerating water flow out, causing the measurement results to deviate from the true seepage direction and flow rate.

[0035] This application quantifies the impact of residual air through comparative experiments: Under the condition that the water storage bag 8 is pre-filled with the same amount of water (500mL), different residual air volumes are set, and tests are conducted under the conditions that the infiltration flow rate in the sand tank 9 is 20cm / d (upward flow) and -20cm / d (downward flow). The experimental results show that when the air in the water storage bag 8 is completely emptied, the infiltration flow rate measured for upward flow is 18.2cm / d, with a relative error of 9.0%; the infiltration flow rate measured for downward flow is -18.2cm / d, with a relative error of 9.0%.

[0036] When the residual air volume is 50 mL, the upward flow velocity is measured to be 16.8 cm / d, with a relative error of 16.0%; the downward flow velocity is measured to be -19.5 cm / d, with a relative error of 2.5%.

[0037] When the residual air volume increased to 100 mL, the upward flow velocity was measured to be 15.1 cm / d, with the relative error further increasing to 24.5%; the downward flow velocity was measured to be -21.2 cm / d, with the relative error increasing to 6.0%.

[0038] When the residual air volume reaches 200 mL, the upward flow velocity is only 12.5 cm / d, with a relative error as high as 37.5%; the downward flow velocity is -23.8 cm / d, with the relative error expanding to 19.0%.

[0039] As shown in the data above, when the water flows upwards, residual air hinders the water flow into the water storage bag 8, resulting in a lower measured flow velocity. The measurement error increases significantly with the increase in residual air volume. Conversely, when the water flows downwards, residual air accelerates the water flow out of the water storage bag 8, resulting in a higher measured flow velocity. Again, the measurement error increases continuously with the increase in residual air volume. Therefore, this application requires that the air inside the water storage bag 8 be completely purged before connection to ensure measurement accuracy.

[0040] In some embodiments, the most common leakage is the rupture of the water storage bag 8. Quality problems with the bag itself and the activity of aquatic organisms in the surface water may cause the water storage bag 8 to rupture. Therefore, the water storage bag 8 should be handled with care and checked frequently for leaks. If necessary, protective measures can be added to the outside of the water storage bag 8, such as covering the water storage bag 8 with a plastic bag. Leaks may also occur between the water storage bag 8 and the cylindrical barrel 2 of the permeate flow meter 15. Such leaks are generally at the joints of the hose 5, valve 7, etc., and need to be handled according to the actual situation. This application will not elaborate on this further.

[0041] In some embodiments, the design of the flexible hose 5 differs from the rigid tubing used in traditional infiltration meters, making it suitable for various coastal tidal variations. Traditional infiltration flow meters 15 typically use rigid plastic or metal tubing as the connection between the infiltration chamber 1 and the water storage bag 8. In coastal tidal environments, water levels rise and fall periodically with the tides, and water flow velocity and direction change frequently. Simultaneously, tidal currents exert continuous thrust and pulling forces on the instrument. Rigid tubing cannot absorb these dynamic loads, easily leading to the instrument being displaced by the water flow, disrupting the seal with sediments; loosening or detachment at connections due to stress concentration; and fatigue fracture of the rigid tubing itself during repeated bending.

[0042] This application uses flexible tubing (such as reinforced PVC tubing or silicone tubing) instead of rigid tubing. Its advantages are: the tubing is flexible, passively adapting to water level fluctuations and flow direction changes, absorbing the pulling force generated by tidal currents, and maintaining the overall stability of the instrument; the tubing 5 allows for a certain relative displacement between the infiltration chamber 1 and the water storage bag 8, facilitating deployment in complex terrain; and the tubing 5 disperses stress through its own deformation when subjected to external forces, effectively reducing the risk of connection detachment or breakage. Experimental verification shows that in continuous operation tests simulating tidal fluctuations (water level change range ±0.5m, period 12h), the instrument connected with tubing 5 did not experience connection detachment or sealing failure within 7 days, while the control group using rigid tubing showed loose connections and leakage on the 3rd day.

[0043] In some embodiments, according to such Figure 1 The example shown is an indoor sand trough simulation calibration experiment. A 10cm layer of gravel 10 is laid at the bottom of the sand trough 9, covered with a 0.1mm stainless steel mesh 12, and then a 30cm thick layer of medium sand is filled using a wet-filling method, compacted layer by layer with a wooden mallet. A constant head device 13 and a water pump 14 are connected to form a water circulation system. The permeation flow meter 16 (28cm in diameter) described in this invention is slowly inserted 10cm deep into the sand layer.

[0044] Stabilization time experiment: The upward seepage velocity in sand tank 9 was set at 20 cm / d. Measurements were taken after different stabilization times (5, 10, 15, 20, 30, 45 min). The results showed that the flow velocity fluctuated greatly before 10 min; after 20 min, the flow velocity stabilized at 18.2 cm / d; after 30 min, the water storage bag 8 was close to saturation, and the flow velocity began to decrease. The upward / downward and high / low velocity experiments were repeated, and 20 min was finally determined as the standard stabilization time.

[0045] Correction coefficient experiment: With a fixed stabilization time of 20 min, the actual seepage velocity V_tank in sand tank 9 was varied (5, 10, 20, 50, 100, 200 cm / d), and the seepage velocity between groundwater and surface water was measured using instruments. Calculations showed that, under all flow velocities, the working efficiency E... m The accuracy remained stable between 83% and 94%. Fitting all data yielded the optimal correction coefficient C = 1.10. This example provides scientific operating parameters and quantitative correction basis for the instrument's field application, proving that the instrument's design is reasonable and that the measurement results are calibrable and traceable.

[0046] In some embodiments, an in-situ measurement example was conducted in a coastal zone. Fifteen infiltration flow meters 15, which had undergone indoor calibration (C=1.10), were evenly distributed around a river in a coastal zone, 1.5-2 m from the riverbank. This area is affected by tides and human activities. The instruments were stabilized for 24 hours after installation. Water storage bags 8 pre-filled with 1000 mL of water were used, connected, and the ball valve 7 was opened. The measurement time was set to 3 hours (adjusted according to the estimated flow rate). The measurement was repeated three times at each location, the average value was taken, and multiplied by the calibration factor 1.10 to obtain the final infiltration flow rate.

[0047] Measurements showed that the area is primarily fed by groundwater throughout the year, with the average exchange rate during the wet season (15 cm / d) significantly higher than that during the dry season (5 cm / d). A record showed that after a heavy rainfall, the river level rose sharply by 0.7 m within 3 hours, causing a reversal of the hydraulic gradient. The instrument sensitively detected this change, and in the following 24 hours, all locations showed surface water replenishing groundwater, demonstrating its responsiveness to short-term, drastic environmental changes.

[0048] Data analysis shows that the exchange rate is strongest in the northeastern section of the river (>20 cm / d), while it is weakest in the southwestern section (<2 cm / d). Combined with field investigations, it was found that the southwestern section is a dumping ground for domestic waste, and the riverbed is clogged with sediment. Instrumental measurements quantify the impact of human activities on riverbed permeability, providing crucial data support for environmental management and ecological restoration.

[0049] This embodiment addresses several technical issues inherent in traditional permeate flowmeter systems, including insufficient sealing leading to leakage errors, unclear measurement timing resulting in unstable data or measurement failures, excessively thin connecting pipe diameters and thick bag walls causing additional resistance leading to lower measured values, easy rupture of the water storage bag 8 and residual air causing buoyancy interference, rigid pipes being unsuitable for tidal environments, and the lack of a unified correction coefficient resulting in uncorrectable measurement results. Through structural optimization, sealing, resistance, and reliability issues are fundamentally reduced. An experimentally determined optimal waiting time of 20 minutes ensures the scientific validity of the measurement timing. A correction coefficient of 1.10 is used to correct system deviations, bringing the measurement results closer to the true values. The flexible hose design allows the instrument to adapt to tidal changes, broadening its application scenarios. Field examples verify its sensitive response to rainfall events and the impact of human activities, providing reliable data support for environmental management and ecological restoration.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A permeate flow meter for measuring groundwater-surface water exchange in coastal zones, characterized in that, The permeation flow meter (15) includes: a permeation chamber (1), a water tank connector (3), an elbow (4), a hose (5), a pipe sleeve (6), a ball valve (7), and a water storage bag (8). The infiltration chamber (1) is composed of a cylindrical barrel (2). An installation hole is provided at the center of the top of the cylindrical barrel (2). The water tank connector (3) is fixedly installed in the installation hole. The upper end of the water tank connector (3) is connected to one end of the elbow (4), and the other end of the elbow (4) is connected to one end of the hose (5). The other end of the hose (5) is movably connected to one end of the ball valve (7). The other end of the ball valve (7) is sealed to the opening of the water storage bag (8) through the sleeve (6) to form a sealed structure. When the ball valve (7) is closed, the water storage bag (8) is disconnected from the hose (5), and the water storage bag (8) forms an independent sealing unit; When the ball valve (7) is opened, the water storage bag (8) is connected to the internal space of the barrel (2) through the hose (5), the elbow (4), and the water tank connector (3); the bottom edge of the barrel (2) is used to insert into the sediment at the bottom of the water, and the barrel (2) and the sediment form a sealed contact through the weight of the sediment.

2. The permeate flow meter for measuring groundwater-surface water exchange in coastal zones according to claim 1, characterized in that, The diameter of the cylindrical barrel (2) is 28cm and the height is 15cm; the volume of the water storage bag (8) is 4L and the wall thickness of the water storage bag (8) does not exceed 0.3mm.

3. The permeate flow meter for measuring groundwater-surface water exchange in coastal zones according to claim 1, characterized in that, The inner diameter of the water tank connector (3) and the hose (5) is the same, both set to 12mm.

4. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 1, characterized in that, The water storage bag (8) is pre-filled with 500 to 1000 mL of water before connection, and the air inside the water storage bag (8) is completely emptied. The pre-filled water volume does not exceed 75% of the volume of the water storage bag (8).

5. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 1, characterized in that, When the ball valve (7) is closed, the water storage bag (8) is disconnected from the hose (5), and the water storage bag (8) forms an independent sealing unit, maintaining a sealed state during movement, weighing or replacement.

6. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 1, characterized in that, An indoor sand bath simulation experiment was conducted using the aforementioned permeation flow meter (15). The experimental method was as follows: S1: Construct a sand trough simulation experimental system, determine the optimal thickness of the water storage bag (8) based on the experiment, and evenly spread gravel (10) with a height of 10cm at the bottom of the sand trough (9). The gravel (10) buries the water distribution pipe and does not block the water outlet (11) on the water distribution pipe. A stainless steel screen (12) with a aperture of 0.1mm is laid on top of the gravel (10). Sand samples are filled on top of the stainless steel screen (12) using the wet filling method. Every 3cm of sand layer is compacted with a wooden mallet, and a total of 30cm is filled. S2: Use the constant head device (13) to continuously pass water from the bottom of the sand tank (9) for 8 hours to rinse the fine particles. Then, use the water pump (14) to pump the water out of the sand tank (9) into the constant head device (13) to form a water circulation. Run continuously for 2 days to remove air bubbles from the sand layer. S3: Slowly insert the permeation flow meter (15) into the sand layer of the sand trough (9) to a depth of 10cm. After continuing to supply water at a constant head for 24 hours, conduct an indoor calibration experiment, change the waiting time, seepage velocity and seepage direction, measure the seepage velocity under different conditions, and determine the optimal waiting time and calibration coefficient.

7. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 6, characterized in that, The indoor calibration experiment is as follows: change the waiting time, seepage velocity and seepage direction, and conduct a full-factor sand tank (9) seepage test; during the seepage process, use two permeation flow meters (15) to measure the seepage velocity at the same time. Before the measurement, fill the water storage bag (8) with a volume of V1 of water; after the air in the water storage bag (8) is emptied, close the ball valve (7) and connect it to the hose (5), immediately open the ball valve (7) to start the measurement, after the waiting time, close the ball valve (7) and take out the water storage bag (8), use a graduated measuring cylinder to measure the volume of water in the water storage bag (8), and record it as V2; calculate the seepage velocity between groundwater and surface water. When the calculated value is positive, it indicates that the seepage direction is upward, and at this time the groundwater replenishes the surface water; conversely, if it is negative, it indicates that the seepage direction is downward, that is, the surface water replenishes the groundwater; the calculation formula is as follows: ； in, Q is the infiltration velocity between groundwater and surface water; A is the cross-sectional area of ​​the infiltration chamber (1); T is the waiting time; V1 is the volume of pre-filled water; V2 is the volume of water in the water storage bag 8 after measurement.

8. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 6, characterized in that, Determining the optimal waiting time includes: The permeation flow rate in the sand tank (9) was controlled at 20 cm / d. The flow rate measured by the permeation flow meter (15) was measured after different waiting times of 5 min, 10 min, 15 min, 20 min, 30 min and 45 min. When the waiting time was 5 minutes, the measured flow rate was 12.3 cm / d with a relative error of 38.5%; when the waiting time was 10 minutes, the measured flow rate was 15.8 cm / d with an error of 21.0%; when the waiting time was 15 minutes, the measured flow rate was 17.5 cm / d with an error of 12.5%; when the waiting time was 20 minutes, the measured flow rate was 18.2 cm / d with an error of 9.0%; when the waiting time was 30 minutes, the water storage bag (8) was close to saturation, and the measured flow rate began to decrease; 20 minutes was determined as the optimal waiting time.

9. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 6, characterized in that, Determining the correction coefficient includes: fixing the optimal waiting time, controlling the actual infiltration velocity of the sand tank (9) to be 5cm / d, 10cm / d, 20cm / d, 25cm / d, 50cm / d, 100cm / d, 150cm / d, and 200cm / d respectively, and measuring the flow velocity measured by the infiltration flow meter (15) respectively; repeating the measurement three times and calculating the average infiltration velocity; calculating the working efficiency of the infiltration flow meter (15), and the correction coefficient of the infiltration flow meter (15) is the reciprocal of its working efficiency; the calculation formula is as follows: ； ； in, It is the average permeation velocity; This represents the actual infiltration velocity in the sand tank. To improve the working efficiency of the permeate flow meter; This is the correction factor.

10. A permeability meter for measuring groundwater-surface water exchange in coastal zones according to claim 6, characterized in that, The optimal thickness of the water storage bag (8) was determined experimentally, including: testing with three different wall thicknesses of water storage bags (8), namely thin-walled, conventional, and thick-walled types, with wall thicknesses of 0.2 mm, 0.5 mm, and 1.0 mm, respectively; comparative measurements were conducted under the same sand tank (9) with a permeation flow rate of 20 cm / d and a waiting time of 20 min; the experimental results showed that when the wall thickness of the water storage bag (8) was 0.2 mm, the instrument measured a flow rate of 18.2 cm / d, a working efficiency of 0.91, and a relative error of 9.0%; when the wall thickness increased to 0.5 mm... When the wall thickness is increased to 1.0 mm, the measured flow velocity drops to 16.5 cm / d, the working efficiency drops to 0.825, and the relative error increases to 17.5%; when the wall thickness is further increased to 1.0 mm, the measured flow velocity is only 13.8 cm / d, the working efficiency drops to 0.69, and the relative error is as high as 31.0%; when the wall thickness increases from 0.2 mm to 1.0 mm, the working efficiency drops from 0.91 to 0.69, and the measurement error increases by 22 percentage points; the wall thickness of the water storage bag (8) does not exceed 0.3 mm, so as to minimize the influence of the bag deformation resistance on the measurement accuracy.

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