A method for controlling the excessive growth of invasive submerged plants in rivers

Abstract

This invention belongs to the field of ecological regulation technology of river aquatic plants. Specifically, it discloses a method for preventing the excessive growth of invasive submerged plants in rivers. By accurately calculating the water flow velocity threshold for controlling the excessive growth of submerged plants, and using a combination of upstream reservoir outflow and downstream reservoir water level fluctuations for joint regulation, the aim of preventing the excessive growth of submerged plants in the river section can be achieved.

Description

Technical Field

[0001] This invention specifically relates to a method for preventing the excessive growth of invasive submerged plants in rivers, belonging to the field of ecological regulation technology for river aquatic plants. Background Technology

[0002] Biosecurity, represented by invasive plants, has posed a serious threat to environmental health, ecological security, and sustainable social development. Therefore, biosecurity, represented by invasive plants, has become one of the major global environmental and ecological issues. After invading a new habitat, invasive plants spread rapidly under suitable climate, soil, water, and dispersal conditions, competing with, excluding, and ultimately replacing local biological communities, forming large-scale, single-dominant communities; disrupting native flora and fauna, and leading to the loss of local biodiversity.

[0003] Currently, the main methods for controlling the excessive growth of submerged plants include physical methods (physical interception and mechanical dredging), chemical methods (herbicides), and ecological methods (stocking herbivorous fish). Physical interception methods can lead to excessive accumulation of aquatic plants, with some plants even squeezing through the debris barriers and entering the intake screens, resulting in limited interception effectiveness. Mechanical dredging methods have also been urgently applied, but due to the large amount and wide distribution of aquatic plants in reservoirs, it is difficult to solve the problem of rampant aquatic plant growth, and the economic cost is high. Chemical methods have limitations in terms of water safety, especially in drinking water sources. Although ecological methods are widely recommended, the sustainability of biological methods for controlling aquatic plants during the implementation period is difficult, especially during fishing bans. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preventing the excessive growth of invasive submerged plants in rivers. By accurately calculating the water flow velocity threshold for controlling the excessive growth of submerged plants, and by using a combination of upstream reservoir outflow and downstream reservoir water level fluctuations for joint regulation, the method aims to prevent the excessive growth of submerged plants in the river section.

[0005] The technical solution of the present invention is as follows:

[0006] This invention provides a method for preventing the excessive growth of invasive submerged plants in rivers. By accurately calculating the water flow velocity threshold for controlling the excessive growth of submerged plants, and by using a combination of upstream reservoir outflow and downstream reservoir water level fluctuations for joint regulation, the method aims to prevent the excessive growth of submerged plants in the river section.

[0007] Preferably, the method for preventing the excessive growth of invasive submerged plants in rivers includes the following steps:

[0008] S1. Conduct field aquatic plant surveys during the peak growth period of submerged plants, and use drones to photograph the spatial distribution of submerged plants in the study section. At the same time, use a flow velocity and flow profiler to randomly measure the average flow of several different river sections in the study section. The collected flow data will be used for later model calibration.

[0009] S2. Plot the spatial distribution of submerged plants in the study section of the river on the Ovi map to obtain the specific coordinates of the boundaries of the sheet-like distribution of submerged plants.

[0010] S3. Conduct underwater topographic measurements and construct a two-dimensional hydrodynamic model of the river section based on the measurements.

[0011] S4. Divide the study river section into grids, and locally densify the grids in areas with dense submerged plant growth obtained from field aquatic plant surveys.

[0012] S5. Using the average roughness of the river section of 0.025 as the initial roughness value and the normal water level of the river section under study as the boundary condition, run the hydrodynamic model and read the water depth data of different grids.

[0013] S6, according to formula Let's first assume an initial value. Based on the water depth data of different grids read in step S5, the roughness value n of different grids can be calculated, and the initial roughness field can be established.

[0014] S7. Run the hydrodynamic model in the initial roughness field and read the flow data of different grids in the study river section;

[0015] S8. Run the hydrodynamic model in the initial roughness field, read the velocity data of different grids in the studied river section, and establish the velocity field.

[0016] S9. Overlay the sheet-like distribution boundary of submerged plants drawn on the Ovi map in step S2 onto the velocity field to obtain the velocity value at the distribution boundary of submerged plants. Take the maximum value as the velocity threshold for controlling the excessive growth of submerged plants.

[0017] S10. Based on the flow velocity threshold for controlling the excessive growth of submerged plants determined in step S9, use the hydrodynamic model to calculate the combined conditions of the outflow from the upstream reservoir and the water level fluctuation of the downstream reservoir, and find the flow rate in the area where the average flow velocity can reach the flow velocity threshold through trial calculation.

[0018] S11. Based on the combined conditions obtained in S10, jointly regulate the outflow from the upstream reservoir and the water level fluctuations in the downstream reservoir, thereby preventing the excessive growth of submerged plants in the research section.

[0019] Preferably, the hydrodynamic model is

[0020] ;

[0021] In the formula, h is the actual water depth; ζ is the water level calculated from the average lake surface; u and v are the velocity components along the x and y directions, respectively; g is the gravitational acceleration; ρ is the water density; and f is the Coriolis force coefficient. , This represents the wind stress component on the lake surface. b , b This is the component of underwater friction.

[0022] Among them, the Cochrane coefficient: ;

[0023] In the formula, This is the Earth's rotational angular velocity; The latitude of the lake;

[0024] Among them, the wind stress components on the lake surface are: , ;

[0025] In the formula, This is the wind stress coefficient; air density; The wind speed is 10 meters above the lake surface. , These are the wind speeds in the x and y directions, respectively.

[0026] Among them, the component of underwater friction is: , ;

[0027] In the formula, , where n is the roughness coefficient.

[0028] Preferably, after running the hydrodynamic model and reading the flow data, the hydrodynamic model is roughness calibrated by combining the measured flow data of different profiles obtained in step S1, using the coefficient of determination (R²) and Nash efficiency coefficient (NCO). The accuracy of the model is verified using the following expression:

[0029] ;

[0030] In the formula, For the i-th measured flow rate, m 3 / s; For the i-th simulated flow rate, m 3 / s; The measured average flow rate is m 3 / s; To simulate the average flow rate, m 3 / s; n is the number of data points, such as R²>0.5 and 0.5 <E NS If the value is less than 1.0, it indicates that the roughness parameter of the established model is reasonable and the calculation method is correct, and it can be used to invert the impact of ecological regulation on the river flow field; otherwise, return to step S6 and reset. The value is adjusted until the model's accuracy meets the requirements.

[0031] Preferably, when reading different grid flow and velocity data in steps S7 and S8, the upstream reservoir outflow and downstream reservoir water level conditions measured by the hydrological station on the day of the aquatic plant survey in step S1 should be used as boundary conditions to run the hydrodynamic model.

[0032] Preferably, in step S10, the maximum drop in the water level of the downstream reservoir is controlled within 0.5m of the normal water level drop. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the simulated river section and grid division in the embodiment;

[0034] Figure 2 This is a schematic diagram illustrating the changes in the daily amount of floating aquatic plants and debris removed from the Wangfuzhou Power Plant's wastewater interception and discharge system, along with the inflow rate.

[0035] Figure 3 The example shows a scatter plot of the daily amount of floating weeds and debris removed from the Wangfuzhou Power Plant's wastewater interception and discharge system, along with the inflow rate. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0037] This invention provides a method for controlling the excessive growth of submerged plants in a river section by precisely calculating the water flow velocity threshold. It employs a combination of upstream reservoir outflow and downstream reservoir water level fluctuations for joint regulation, achieving the goal of preventing excessive growth of submerged plants in the river section. Specifically, it includes the following steps:

[0038] S1. Conduct field aquatic plant surveys during the peak growth period of submerged plants, and use drones to photograph the spatial distribution of submerged plants in the study section. At the same time, use a flow velocity and flow profiler to randomly measure the average flow of several different river sections in the study section. The collected flow data will be used for later model calibration.

[0039] S2. Plot the spatial distribution of submerged plants in the study section of the river on the Ovi map to obtain the specific coordinates of the boundaries of the sheet-like distribution of submerged plants.

[0040] S3. Conduct underwater topographic measurements and construct a two-dimensional hydrodynamic model of the river section based on the measurements; the two-dimensional hydrodynamic model is shown below:

[0041] ;

[0042] In the formula, h is the actual water depth; ζ is the water level calculated from the average lake surface; u and v are the velocity components along the x and y directions, respectively; g is the gravitational acceleration; ρ is the water density; and f is the Coriolis force coefficient. , This represents the wind stress component on the lake surface. b , b This is the component of underwater friction.

[0043] Among them, the Cochrane coefficient: ;

[0044] In the formula, This is the Earth's rotational angular velocity; The latitude of the lake;

[0045] Among them, the wind stress components on the lake surface are: , ;

[0046] In the formula, This is the wind stress coefficient; air density; The wind speed is 10 meters above the lake surface. , These are the wind speeds in the x and y directions, respectively.

[0047] Among them, the component of underwater friction is: , ;

[0048] In the formula, where n is the roughness coefficient;

[0049] S4. Divide the study river section into grids, and locally densify the grids in areas with dense submerged plant growth obtained from field aquatic plant surveys.

[0050] S5. Using the average roughness of the river section of 0.025 as the initial roughness value and the normal water level of the river section under study as the boundary condition, run the hydrodynamic model and read the water depth data of different grids.

[0051] S6, according to formula Let's first assume an initial value. The roughness value n of different grids can be calculated based on the water depth data h of different grids read in step S5, and an initial roughness field can be established based on the roughness value n of different grids.

[0052] S7. In the initial roughness field, the upstream reservoir outflow and downstream reservoir water level conditions measured by the hydrological station on the day of the aquatic plant survey in step S1 are used as boundary conditions. The hydrodynamic model is run, and the flow data of different grids in the study river section are read. The flow data of different grids obtained at this time are used to verify the accuracy of the hydrodynamic model. The flow data of different grids are combined with the measured flow data of different profiles measured in step S1 to calibrate the roughness of the hydrodynamic model, using the coefficient of determination (R²) and Nash efficiency coefficient (NCO). The accuracy of the model is verified using the following expression:

[0053] ;

[0054] In the formula, For the i-th measured flow rate, m 3 / s; For the i-th simulated flow rate, m 3 / s; The measured average flow rate is m 3 / s; To simulate the average flow rate, m 3 / s; n is the number of data points, such as R²>0.5 and 0.5 <E NS If the value is less than 1.0, it indicates that the roughness parameter of the established model is reasonable and the calculation method is correct, and it can be used to invert the impact of ecological regulation on the river flow field; otherwise, return to step S6 and reset. The value is adjusted until the model accuracy meets the requirements;

[0055] S8. In the initial roughness field, the outflow from the upstream reservoir and the water level of the downstream reservoir measured by the hydrological station on the day of the aquatic plant survey in step S1 are used as boundary conditions. The hydrodynamic model is run, and the velocity data of different grids in the study section are read to establish the velocity field.

[0056] S9. Overlay the sheet-like distribution boundary of submerged plants drawn on the Ovi map in step S2 onto the velocity field to obtain the velocity value at the distribution boundary of submerged plants. Take the maximum value as the velocity threshold for controlling the excessive growth of submerged plants. High-velocity water flow in the area exceeding the velocity threshold will break the submerged plants, affect the establishment of submerged plants, and cause the submerged plants to stop growing. Therefore, the velocity threshold is determined to regulate the average velocity in the area where submerged plants are easy to grow in the river section. High-velocity water flow in the threshold area will break the submerged plants, affect the establishment of submerged plants, and cause the submerged plants to stop growing.

[0057] S10. Since changes in the outflow from the upstream reservoir and fluctuations in the water level of the downstream reservoir will affect the flow velocity in the river section, it is necessary to calculate the flow velocity threshold for controlling the excessive growth of submerged plants in step S9, combined with the hydrodynamic model, to obtain the flow rate at which the average flow velocity in the area with abundant submerged plant distribution can reach the flow velocity threshold. This will facilitate the subsequent control of the combined conditions of the outflow from the upstream reservoir and the water level fluctuations of the downstream reservoir to control the flow velocity threshold.

[0058] S11. Through hydrodynamic modeling, it can be found that an increase in the outflow from the upstream reservoir will increase the flow velocity in the river section, and a decrease in the water level of the downstream reservoir will also increase the flow velocity in the river section. However, in general, the decrease in the water level of the downstream reservoir should not be more than 0.5m lower than the normal storage level, otherwise it will cause a safety accident. Therefore, based on the combined conditions obtained in S10, the outflow from the upstream reservoir and the fluctuation of the water level in the downstream reservoir should be regulated to ensure that the flow velocity in the area where submerged plants are abundant reaches the flow velocity threshold that inhibits their growth. This allows the water flow to influence the establishment of submerged plants and achieve the goal of preventing and controlling the excessive growth of submerged plants in the research river section.

[0059] In this embodiment, the section of the Han River from the Danjiangkou Dam to the Wangfuzhou Hydropower Station is taken as an example, including the Wangfuzhou Reservoir area and the section downstream of the Danjiangkou Dam, with a length of approximately 35 km. To better reflect the shoreline shape and the complex topography of the calculated river section, the Delaunay triangulation method is used to divide the calculated river section into grids, with a total of 15,741 grids. The grids on the shore of the Waterfront New City (left bank of the Han River), the rubble pile at Mupai Port, and the Elodea growth area on the right side of Zhongzhou Island are locally densified. The size of the undensed triangular grid is 100m × 100m, and the average size of the densified grid is 30m × 30m, with the smallest being 10m × 10m. The model boundary, underwater topography of the lake area, and calculation grid are shown in [reference needed]. Figure 1 ;

[0060] From July 26 to July 31, the Danjiangkou Reservoir opened its gates to release floodwaters. The model was verified using water level data from the upstream of the sluice gate and Huangjiagang hydrological station from July 21 to August 1, 2021. The average roughness of the cross section was used as the initial roughness value. The roughness was corrected according to the water depth of different grids in the model calculation. The roughness coefficient was then adjusted in segments according to the water level and flow field conditions.

[0061] Flow measurement was conducted during the spring aquatic plant survey. The model was validated using the measured flow velocity on the right side of Zhongzhou Island on March 8, as shown in Table 1.

[0062] Table 1. Verification of flow velocity on the right side of Zhongzhou Island

[0063]

[0064] Based on the simulated water level and simulated flow velocity, the coefficient of determination (R²) and Nash efficiency coefficient (E) are used. NS The accuracy of the model was verified, and the verification criteria are shown in Table 2.

[0065] Table 2. Criteria for verifying model accuracy

[0066]

[0067] In summary, the established model can effectively invert the flow motion of the Danjiangkou-Wangfuzhou section of the river. The calibrated calculated values ​​are close to the measured values, indicating that the parameter values ​​of the established model are reasonable and the calculation method is correct. It can be used to invert the impact of ecological regulation on the flow field of the river section.

[0068] The Danjiangkou Reservoir discharged floodwaters from July 26 to July 31. To assess the impact of this high-flow-rate event on aquatic plant growth in the Danjiangkou-Wangfuzhou section, a survey of aquatic plant growth in this section was conducted on August 3. Analysis suggests that the high flow rate (approximately 3500 m³ / h) significantly affected the plant growth. 3 The high flow velocity and high water level brought about by the scheduling significantly affected the Elodea nuttallii community in high-risk areas such as the upstream section of Zhongzhou Island, the main channel near the expressway bridge on the left bank of the Hanjiang River, and the downstream section of Tianhe Hotel. Most of the aquatic plants were washed downstream. This shows that as the flow velocity increases, the biomass of Elodea decreases, and its growth is significantly inhibited. The study found that a flow velocity of 0.14 m / s is an important critical value affecting the growth and coverage of Elodea nuttallii. This embodiment uses a flow velocity of 0.14 m / s as a reference target to verify whether 0.14 m / s is the flow velocity threshold for controlling excessive growth of Elodea nuttallii. Based on the amount of aquatic plants dredged by the Wangfuzhou Power Plant's cleaning fleet before the power plant's interceptor discharge, the correlation between the amount of aquatic plants cleaned and the inflow was statistically analyzed. The daily cleaning volume of floating aquatic plants before the Wangfuzhou Power Plant's interceptor discharge and the changes in the inflow during December 2020 to October 2021 show that the cleaning volume and the inflow process are basically consistent (e.g., ...). Figure 2When the inflow to Wangfuzhou Reservoir is below 1500 m³ / s, the amount of aquatic plants cleared is relatively small, generally less than 100 tons / day. During the major floods from August to October 2021, especially in the early stages of the floods in August and September, the amount of aquatic plants cleared increased significantly with the rising water level, reaching a maximum of 582 tons per day. In the later stages of the floods in September and October, the amount of aquatic plants cleared gradually decreased, mainly because most of the aquatic plants in the Danjiangkou-Wangfuzhou section had already been washed away in the early stages of the floods in August and September, and the remaining aquatic plants in the section gradually decreased. Therefore, the amount of aquatic plants cleared is not simply positively correlated with the inflow. In the early stages of the flood, the amount of aquatic plants cleared is directly proportional to the inflow, but in the later stages of the flood, due to the reduction in the remaining aquatic plant biomass, the amount of aquatic plants cleared is no longer directly proportional to the inflow.

[0069] Further analysis of the correlation between the inflow rate and the amount of aquatic plants removed at Wangfuzhou Reservoir shows that (the scatter plot of the two is shown). Figure 3 When the inflow to Wangfuzhou is less than 1500m³ 3 When the flow rate is 1500 m³ / s, the amount of aquatic plants cleared is less than 100 t / d; when the flow rate reaches 1500 m³ / s... 3 At a rate of / s, the daily amount of aquatic plants cleared suddenly increased, ranging from 100 tons to 500 tons, indicating that the inflow to Wangfuzhou Reservoir reached 1500 m³ / s. 3 At / s, in some areas, the aquatic plant communities dominated by Elodea nuttallii have been eroded and destroyed, reaching 1500m. 3 A flow rate of / s is a hydrodynamic condition that can produce a significant scouring effect on densely growing mature populations of Elodea. Meanwhile, when the flow rate reaches 3000 m³ / s... 3 At a flow rate of 582 t / s, the daily removal of aquatic plants reached its maximum value. Afterwards, with even higher discharge rates from the Danjiangkou Reservoir, the removal of aquatic plants gradually decreased. This indicates that at 3000m... 3 A flow rate of 1500-3000 m³ / s may be more effective at scouring densely growing, mature Elodea colonies. In summary, during the peak summer growth period of Elodea, the dense growth of the Elodea community forms aggregates, further enhancing its resistance to water scouring. To effectively scour and disrupt these aggregates of mature Elodea plants, the inflow rate at Wangfuzhou Reservoir may need to be 1500-3000 m³ / s. 3 Flood volume per second;

[0070] The average and maximum flow velocities at three typical water areas within the flood level range—Shui'an Xincheng, the right side of Zhongzhou Island, and the rubble pile in Mupai Port—were statistically analyzed. The results indicate that the flow velocity at Wangfuzhou 1500m... 3Under the inflow rate of 3000 m³ / s, the average flow velocity in the waterfront new town is only 0.06 m / s, and the maximum flow velocity is 0.13 m / s, indicating that the scouring effect on Elodea in this area may not be ideal. The average flow velocities on the right side of Zhongzhou Island and in the rubble pile area of ​​Mupai Port are 0.16 m / s and 0.13 m / s, respectively, with maximum flow velocities of 0.51 m / s and 0.55 m / s, respectively. The Elodea in the waters of Zhongzhou Island and the rubble pile area of ​​Mupai Port are significantly affected by scouring, which is consistent with the field survey results. When the inflow rate at Wangfuzhou is 3000 m³ / s... 3 At a flow rate of 0.12 m / s, the average flow velocity in the Waterfront New City increased to 0.12 m / s, with a maximum velocity of 0.31 m / s. The average flow velocities on the right side of Zhongzhou Island and in the rubble-strewn area of ​​Mupai Port were 0.31 m / s and 0.26 m / s, respectively, with maximum velocities reaching 0.92 m / s and 1.04 m / s. Therefore, the average flow velocity range in areas significantly affected by scouring is 0.13–0.31 m / s, but the specific flow velocity threshold controlling excessive growth of *Elodea nuttallii* remains undetermined. According to the aquatic plant survey conducted on August 3rd, *Elodea nuttallii* is mainly distributed along the shore of the Waterfront New City, upstream of Mupai Port, and on the right bank of Zhongzhou Island. To determine the flow velocity threshold controlling excessive growth of *Elodea nuttallii*, flow field analysis was performed on the flow velocity at the *Elodea nuttallii* growth boundary in the above areas. The flow field analysis results show that the maximum flow velocity at the *Elodea nuttallii* growth boundary is approximately between 0.06 m / s and 0.17 m / s; the maximum value of 0.17 m / s was taken as the flow velocity threshold.

[0071] Based on the established velocity threshold of 0.17 m / s for controlling excessive growth of Elodea, the Mike21 model was used to set the combined conditions of the outflow from Danjiangkou Reservoir (i.e., the inflow from Wangfuzhou Reservoir) and the water level fluctuation at the Wangfuzhou Reservoir dam. Through trial calculations, the water level fluctuation conditions at which the flow velocity on the right side of Zhongzhou Island, the shore of Shui'an New City, and the rubble pile in Mupai Port (within 200m) could reach 0.17 m / s were found. Table 3 shows the flow velocities at the shore of Shui'an New City, the right side of Zhongzhou Island, and the rubble pile in Mupai Port under different combined conditions.

[0072] Table 3. Flow velocity at the shoreline of Waterfront New City, the right side of Zhongzhou Island, and the rubble pile of Mupai Port under different combinations of conditions.

[0073]

[0074] As shown in the table above, the rise in water level of Wangfuzhou Reservoir will reduce the flow velocity at key points, creating hydrodynamic conditions unfavorable to inhibiting the growth of Elodea. Therefore, the water level of Wangfuzhou should be lowered during ecological regulation. Considering the impact of the drop in water level on power generation and dam safety, the drop in water level of Wangfuzhou Reservoir should not be too large. According to statistics on the actual operating water level of Wangfuzhou since 2014, its lowest water level is 85.8m, which is 0.43m lower than the normal storage level. Therefore, the maximum drop in water level of Wangfuzhou during ecological regulation should be controlled within 0.5m.

[0075] From the correlation between the inflow rate and the amount of aquatic plants removed at Wangfuzhou Reservoir, we can obtain that 1500m 3 A flow rate of / s is a hydrodynamic condition that can significantly scour dense, mature populations of Elodea. Based on this, the available ecological regulation scheme requires a minimum inflow rate of 1500 m³ / s. 3 / s, while the water level of Wangfuzhou Reservoir fluctuates and drops by 0.5m, only when the flow velocity threshold of 0.17m / s, which controls the growth of Elodea, is reached near Zhongzhou Island; while near Mupai Port, the inflow rate needs to reach 2000m³ / s to reach the flow velocity threshold that controls the growth of Elodea. 3 The flow rate is approximately 1000 m³ / s; however, near the Waterfront New City, the required flow rate for controlling Elodea is too large, exceeding 3000 m³ / s. 3 / s; Wang Fuzhou suggests that the key area for ecological regulation and control of aquatic plant growth should be located near Zhongzhou Island. It is recommended that during the late autumn and spring ecological regulation periods, the outflow from Danjiangkou should reach at least 1500m. 3 The peak flow rate is / s, and the Wangfuzhou Reservoir adopts a water level "fluctuation regulation method" to maintain the water level drop at around 0.5m.

[0076] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for controlling the excessive growth of invasive submerged plants in rivers, characterized in that, By precisely calculating the water flow velocity threshold for controlling excessive growth of submerged plants, and using a combination of upstream reservoir outflow and downstream reservoir water level fluctuations for joint regulation, the aim is to prevent excessive growth of submerged plants in the river section. This includes the following steps: S1. Conduct field aquatic plant surveys during the peak growth period of submerged plants, and use drones to photograph the spatial distribution of submerged plants in the study section. At the same time, use a flow velocity and flow profiler to randomly measure the average flow of several different river sections in the study section. The collected flow data will be used for later model calibration. S2. Plot the spatial distribution of submerged plants in the study section of the river on the Ovi map to obtain the specific coordinates of the boundaries of the sheet-like distribution of submerged plants. S3. Conduct underwater topographic measurements and construct a two-dimensional hydrodynamic model of the river section based on the measurements. S4. Divide the study river section into grids, and locally densify the grids in areas with dense submerged plant growth obtained from field aquatic plant surveys. S5. Using the average roughness of the river section of 0.025 as the initial roughness value and the normal water level of the river section under study as the boundary condition, run the hydrodynamic model and read the water depth data of different grids. S6, according to formula Let's first assume an initial value. Based on the water depth data of different grids read in step S5, the roughness value n of different grids can be calculated, and the initial roughness field can be established. S7. Run the hydrodynamic model in the initial roughness field and read the flow data of different grids in the study river section; S8. Run the hydrodynamic model in the initial roughness field, read the velocity data of different grids in the studied river section, and establish the velocity field. S9. Overlay the sheet-like distribution boundary of submerged plants drawn on the Ovi map in step S2 onto the velocity field to obtain the velocity value at the distribution boundary of submerged plants. Take the maximum value as the velocity threshold for controlling the excessive growth of submerged plants. S10. Based on the flow velocity threshold for controlling the excessive growth of submerged plants determined in step S9, use the hydrodynamic model to calculate the combined conditions of the outflow from the upstream reservoir and the water level fluctuation of the downstream reservoir, and find the flow rate in the area where the average flow velocity can reach the flow velocity threshold through trial calculation. S11. Based on the combined conditions obtained in S10, jointly regulate the outflow from the upstream reservoir and the water level fluctuations in the downstream reservoir, thereby preventing the excessive growth of submerged plants in the research section.

2. The method for preventing excessive growth of invasive submerged plants in rivers as described in claim 1, characterized in that, The hydrodynamic model is ； In the formula, h is the actual water depth; ζ is the water level calculated from the average lake surface; u and v are the velocity components along the x and y directions, respectively; g is the gravitational acceleration; ρ is the water density; and f is the Coriolis force coefficient. , This represents the wind stress component on the lake surface. , This is the component of underwater friction. Among them, the Cochrane coefficient: ; In the formula, This is the Earth's rotational angular velocity; The latitude of the lake; Among them, the wind stress components on the lake surface are: , ; In the formula, This is the wind stress coefficient; air density; The wind speed is 10 meters above the lake surface. , These are the wind speeds in the x and y directions, respectively. Among them, the component of underwater friction is: , ; In the formula, , where n is the roughness coefficient.

3. The method for preventing excessive growth of invasive submerged plants in rivers as described in claim 2, characterized in that, After running the hydrodynamic model and reading the flow data, the hydrodynamic model was roughness calibrated using the measured flow data from different profiles determined in step S1, employing the coefficient of determination R² and the Nash efficiency coefficient. The accuracy of the model is verified using the following expression: ； In the formula, For the i-th measured flow rate, m 3 / s; For the i-th simulated flow rate, m 3 / s; The measured average flow rate is m 3 / s; To simulate the average flow rate, m 3 / s; n is the number of data points, such as R²>0.5 and 0.5 <E NS If the value is less than 1.0, it indicates that the roughness parameter of the established model is reasonable and the calculation method is correct, and it can be used to invert the impact of ecological regulation on the river flow field; otherwise, return to step S6 and reset. The value is adjusted until the model's accuracy meets the requirements.

4. The method for preventing excessive growth of invasive submerged plants in rivers as described in claim 1, characterized in that, When reading different grid flow and velocity data in steps S7 and S8, the upstream reservoir outflow and downstream reservoir water level conditions measured by the hydrological station on the day of the aquatic plant survey in step S1 should be used as boundary conditions to run the hydrodynamic model.

5. The method for preventing excessive growth of invasive submerged plants in rivers as described in claim 1, characterized in that, In step S10, the maximum drop in water level in the downstream reservoir is controlled within 0.5m of the normal storage level.

Images