Gate control hub regulation and control method adaptive to up and down migration of multi-target fishes

Abstract

The invention discloses a gate control hub regulation and control method adaptive to up and down migration of multi-target fishes. The method comprises the following steps: determining a flow velocity suitability curve suitable for multi-target adult fishes and juvenile fishes; performing gate control engineering flow field numerical simulation under different flow conditions to obtain upstream and downstream flow fields of each representative working condition; according to the determined flow velocity suitability curve of the adult fish and the juvenile fish, flow velocity suitability evaluation is carried out on the obtained upstream and downstream flow fields of the representative working conditions, and migration channels of the adult fish ascending and the juvenile fish descending are predicted according to the flow velocity suitability evaluation result; according to the predicted migration channel of adult fish ascending and juvenile fish descending, if the migration channel is discontinuous, the magnitude relation between the flow speed of the discontinuous area and the fish swimming capacity is compared, and the gate opening mode is changed under the condition that the discharge amount is not changed. The invention provides the gating hub regulation and control method based on adult fish ascending and juvenile fish descending migration channel prediction, which is adaptive to the swimming ability of adult fish and juvenile fish, so that the bidirectional migration requirement of fish can be met, and technical support is provided for water ecology protection work.

Description

Technical Field

[0001] The present invention relates to the field of ecological water conservancy, and specifically to a regulation method for a sluice control hub adapted to the upstream and downstream migrations of multi-target fish. Background Art

[0002] The sluice control hub project built on a river affects the connectivity of the river. Migratory fish have the two-way migratory needs of adult fish migrating upstream to the river water to spawn and reproduce, and juvenile fish migrating downstream to the lake to feed and fatten. Restoring the upstream and downstream migration channels blocked by sluice dams is particularly important for migratory fish.

[0003] Existing fish upstream passage technologies include fishways, fish elevators, natural-like channels, fish locks, etc. Adult fish can successfully migrate upstream using fishways. However, due to the differences in the behavioral characteristics between juvenile fish and adult fish, the upstream water flow inlet of the fishway is difficult to attract juvenile fish migrating downstream, resulting in that fish passage facilities such as fishways are not suitable for juvenile fish to migrate downstream. Existing fish downstream passage technologies include water turbines, spillways, downstream bypass systems, fish collection technologies, etc. These downstream facilities play a certain role in the downstream migration of fish, but there are also various disadvantages such as safety and adaptability.

[0004] Previous studies mostly focused on the blocking effect of power generation hubs on the upstream passage of adult fish, evaluated the flow velocity suitability of different flow conditions of power stations, predicted the upstream passage suitable for multi-target adult fish according to the evaluation results, and proposed suggestions for the inlet layout of fishways and the optimization of power station operation scheduling. There are two deficiencies in previous studies. One is that only the connectivity of the upstream passage of adult fish is considered, and the connectivity of the downstream passage of juvenile fish is not concerned. The other is that there is no analysis of the fish migration passage of the sluice control hub. The sluice control hub only discharges water through the gate, and its regulation method is different from that of the power generation hub. Currently, there is almost no technology that uses the sluice control hub regulation method to improve the connectivity of fish upstream and downstream migration channels on the premise of adapting to the swimming abilities of adult fish and juvenile fish. Summary of the Invention

[0005] The present invention fills the gap in the field of two-way fish passage of sluice control hubs. By predicting the fish migration passages of adult fish migrating upstream and juvenile fish migrating downstream, a regulation method for sluice control hubs adapted to the swimming abilities of adult fish and juvenile fish is formed. Without additionally building a downstream bypass, the characteristics of the sluice control hub are fully utilized to solve the needs of fish two-way migration, providing technical support for water ecological protection work.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A regulation method for a sluice control hub adapted to the upstream and downstream migrations of multiple target fish species. The purpose of building the sluice control hub is to regulate the river water level during the dry season, and it adopts an operation mode of regulating the dry season without regulating the flood. The sluice control hub includes a sluice gate and a fishway. The sluice gate adopts a pneumatic shield gate, and the gate opening is adjusted between 0 and 1. The inlet of the fishway is located on the bank below the sluice, and the discharge of the gate close to the bank provides a fish-attracting water flow condition for the inlet of the fishway. The method includes the following steps:

[0008] Step S1: Determine the flow velocity suitability curves suitable for adult fish and juvenile fish of multiple targets;

[0009] Step S2: Conduct numerical simulations of the flow fields of the sluice control project under different flow conditions to obtain the upstream and downstream flow fields of each representative working condition;

[0010] Step S3: According to the flow velocity suitability curves of adult fish and juvenile fish determined in Step S1, evaluate the flow velocity suitability of the upstream and downstream flow fields of each representative working condition obtained in Step S2, and predict the migration channels for adult fish to move upstream and juvenile fish to move downstream based on the evaluation results of the flow velocity suitability;

[0011] Step S4: According to the migration channels for adult fish to move upstream and juvenile fish to move downstream predicted in Step S3, if the migration channels are discontinuous, compare the magnitude relationship between the flow velocity in the discontinuous area and the swimming ability of the fish, and change the gate opening method under the condition that the discharge remains unchanged.

[0012] Further, Step S1 includes:

[0013] S11: Obtain the body lengths of adult fish and juvenile fish of multiple target fish species passing through the river section where the sluice control hub project is located;

[0014] S12: Obtain the swimming ability data corresponding to the body lengths of adult fish and juvenile fish passing through the fish, including the induced flow velocity, critical swimming speed, and burst swimming speed;

[0015] S13: Define the area where the flow velocity is less than the induced flow velocity as the non-perception area, that is, U < U i ; Define the area where the flow velocity range is between the induced flow velocity and 0.5 times the critical swimming speed as the induction area, that is, U i ≤U < 0.5U c ; Define the area where the flow velocity range is between 0.5 times the critical swimming speed and the critical swimming speed as the preference area, that is, 0.5U c ≤U ≤ U c ; Define the area where the flow velocity range is between the critical swimming speed and the burst swimming speed as the burst area, that is, U c <U ≤ U b ; Define the area where the flow velocity is greater than the burst swimming speed as the barrier area, that is, U > U b ;

[0016] S14: Define the dimensionless flow velocity suitability index VSI to represent the suitability of the flow velocity for the migration of adult fish and juvenile fish. A suitability of 0 indicates that the flow velocity in this area is not suitable for fish migration, and a suitability of 1 indicates that the flow velocity in this area is most suitable for fish migration. Define the flow velocity suitability score value of the non-perception area and the barrier area as 0, and the flow velocity suitability score value of the preference area as 1;

[0017] S15: When U < U i , VSI = 0; When U i ≤U < 0.5U c , when VSI = (U - U i ) / (0.5U c - U i ); When

[0018] 0.5U c ≤U ≤ U c , VSI = 1; When U c <U ≤ U b , VSI = (U - U b ) / (U c - U b ); When U > U b , VSI = 0;

[0019] S16: According to the induced flow velocity, critical swimming speed, and burst swimming speed of adult fish and juvenile fish obtained in step S12, and the piecewise flow velocity suitability index defined in step S15, formulate the flow velocity suitability curves for adult fish and juvenile fish respectively.

[0020] Furthermore, in step S11, the fish body length is obtained by collecting the fish resource survey results of this river section in the literature. The principle for taking the representative body lengths of adult fish and juvenile fish is to select the smaller value within the body length range, and the representative body lengths of adult fish and juvenile fish are respectively selected for multiple fish passage objects.

[0021] Furthermore, the induced flow velocity U i in step S13 is the minimum value of the induced flow velocities of multiple fish species, the critical swimming speed U c is the minimum value of the critical swimming speeds of multiple fish species, and the burst swimming speed U b is the maximum value of the burst swimming speeds of multiple fish species.

[0022] Furthermore, the said step S2 includes:

[0023] S21: Establish a two-dimensional or three-dimensional mathematical model of the long river section upstream and downstream of the sluice control hub to simulate the numerical value of the flow field of the sluice control project. The simulation range includes the upstream river section, the sluice gate, and the downstream river section;

[0024] S22: Verify the mathematical model described in step S21;

[0025] S23: Select representative flows according to the regulation operation plan of the sluice control pivot to formulate calculation conditions.

[0026] S24: Calculate the upstream and downstream flow fields of each condition to obtain hydraulic characteristics, where the hydraulic characteristics include flow velocity, flow direction, and water depth.

[0027] Furthermore, the mathematical model described in step S21 can simulate the discharge under different gate opening conditions.

[0028] Furthermore, step S22 verifies the reliability of the mathematical model by using the hydraulic parameters obtained from the physical model test of the same sluice control pivot.

[0029] Furthermore, the said step S3 includes:

[0030] S31: According to the flow velocity suitability curves of adult fish and juvenile fish formulated in step S1, evaluate the flow velocity suitability of the upstream and downstream flow fields of each representative condition obtained in step S2, so as to obtain the flow velocity suitability distribution conditions suitable for the upstream migration of adult fish and the downstream migration of juvenile fish under each representative condition.

[0031] S32: Select the flow velocity suitability index of 0.4 - 1.0 as the suitable migration channel for fish, and predict the migration channels for the upstream migration of adult fish and the downstream migration of juvenile fish accordingly. Among them, there are two types of upstream migration channels for adult fish. One is that adult fish migrate from the downstream natural river to the fishway entrance and migrate upstream through the fishway, and the other is that adult fish migrate from the downstream natural river to the opened gate and migrate upstream through the fully opened gate; the downstream migration channel of juvenile fish in the sluice control pivot refers to that juvenile fish migrate from the upstream natural river to the opened gate and flow downstream along with the overflow at the top of the gate.

[0032] Furthermore, the said step S4 includes:

[0033] S41: Identify the connectivity of the upstream and downstream migration channels of fish in each representative condition. When the migration channel is discontinuous, it is necessary to change the gate opening method under the condition of unchanged discharge. Specifically:

[0034] S42: When the upstream migration channel is discontinuous, if the flow velocity in the discontinuous area is close to the burst swimming speed of adult fish, then reduce the opening of the gate corresponding to the position on the streamline in this area. If the flow velocity in the discontinuous area is close to the induced flow velocity of adult fish, then increase the opening of the gate corresponding to the position on the streamline in this area.

[0035] S43: When the downstream migration channel is discontinuous, if the flow velocity in the discontinuous area is close to the burst swimming speed of juvenile fish, then reduce the opening of the gate corresponding to the position on the streamline in this area. If the flow velocity in the discontinuous area is close to the induced flow velocity of juvenile fish, then increase the opening of the gate corresponding to the position on the streamline in this area.

[0036] S44: After adjusting the gate opening, the connectivity of the upstream and downstream migratory channels of the working condition is re-predicted according to steps S2 and S3 until both the upstream and downstream migratory channels are continuous.

[0037] Furthermore, the connectivity judgment standard of the upstream migratory channel in step S41 is: from the downstream river channel to the fishway entrance or the fully open gate, if there is a migratory channel with a width exceeding twice the fish body and is continuous and uninterrupted, it indicates that the upstream migratory channel of adult fish is continuous, otherwise it is discontinuous; the connectivity judgment standard of the downstream migratory channel is: from the upstream river channel to the open gate, if there is a migratory channel with a width exceeding two fish bodies and is continuous and uninterrupted, it indicates that the downstream migratory channel of juvenile fish is continuous, otherwise it is discontinuous.

[0038] The beneficial effects of the present invention are:

[0039] 1. The velocity suitability curve suitable for multi-target adult fish and juvenile fish proposed in the present invention fully considers the swimming ability of adult fish and juvenile fish, and avoids water flow obstruction in the fishway or inability to sense the migration direction during fish migration.

[0040] 2. The present invention predicts the upstream and downstream migratory channels based on the velocity suitability curve, quantitatively predicts the position of the migratory channels, provides a reference for the arrangement and operation of auxiliary fish passing devices such as fish intercepting electric fences, and further improves the effect of two-way fish passing.

[0041] 3. The gate control hub control method adapted to the upstream and downstream migration of multi-target fish proposed in the present invention optimizes the connectivity of the upstream and downstream fish migration channels by changing the gate opening method. Compared with upstream fish-passing facilities such as fishways, it meets the two-way migration needs of adult fish in the river section where the gate control hub is arranged to migrate upstream for spawning and reproduction, and juvenile fish to migrate downstream for feeding and fattening, and has the advantages of simplicity and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of one embodiment of a gate control hub control method adapted to upstream and downstream migration of multiple target fishes of the present invention;

[0043] Figure 2 A schematic diagram of the plan layout of a gate control hub in an embodiment;

[0044] Figure 3 It is a schematic diagram of a pneumatic shield gate;

[0045] Figure 4 To adapt the flow velocity suitability curve for adult fish to go up and juvenile fish to go down;

[0046] Figure 5 It is a two-dimensional mathematical model of the long river section upstream and downstream of the gate control hub;

[0047] Figure 6Flow velocity zoning results adapted for adult fish upstream migration and juvenile fish downstream migration under typical working conditions;

[0048] Figure 7 Migration channel prediction results for adult fish upstream migration and juvenile fish downstream migration under typical working conditions;

[0049] Figure 8 Flow velocity zoning results adapted for adult fish upstream migration and juvenile fish downstream migration after adjusting the gate opening mode under typical working conditions;

[0050] Figure 9 Migration channel prediction results for adult fish upstream migration and juvenile fish downstream migration after adjusting the gate opening mode under typical working conditions. Specific implementation manners

[0051] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0052] The embodiments of the present invention provide a gate control hub regulation method adapted to the upstream and downstream migrations of multi-target fish, and the steps are as Figure 1 shown. In the embodiments, the gate control hub mainly consists of buildings such as 20 flood discharge gates, fishways and connecting sections, as Figure 2 shown. The hub project adopts a regulation and operation plan of regulating low water levels without regulating flood levels. All flood discharge gates adopt pneumatic shield gates, and the gates can be adjusted at any opening degree, as Figure 3 shown. The fishway is located on the left bank of the hub. The fishway fish inlet is located on the bank 80 meters downstream of the No. 1 flood discharge gate, and the fishway fish outlet is located on the bank 250 meters upstream of the No. 1 flood discharge gate. The water flow discharged from the flood discharge gate provides a fish-attracting water flow condition for the fishway inlet.

[0053] The embodiments of the present invention provide a gate control hub regulation method adapted to the upstream and downstream migrations of multi-target fish, as Figure 1 shown, and specifically include the following steps:

[0054] Step S1: Determine the flow velocity suitability curves suitable for multi-target adult fish and juvenile fish, including the following sub-steps;

[0055] S11: Obtain the multi-target fish passage objects in the river section where the sluice control pivot project is located. The fish passage objects are the four major Chinese carps, black carp, grass carp, silver carp, and bighead carp. Obtain the body lengths of the adult and juvenile fish of the fish passage objects. The representative body length of the adult fish is taken as 20 cm, and the representative body length of the juvenile fish is taken as 10 cm. The fish passage objects and data such as fish body lengths in step S11 can be obtained by collecting the fish resource survey results in the literature of this river section. To ensure that fish with migratory needs can migrate smoothly, the principle for taking the representative body lengths of adult and juvenile fish is to select the smaller value within the body length range, and the representative body lengths of adult and juvenile fish are respectively selected for various fish passage objects.

[0056] S12: Select the induced flow velocity U i , critical swimming speed U c , and burst swimming speed U b measured under the conditions of a test temperature of 20 °C, a body length of 20 cm, and a body length of 10 cm, which respectively represent the swimming abilities of the adult and juvenile fish of the four major Chinese carps, as shown in Table 1.

[0057] Table 1 Swimming abilities of adult and juvenile fish of the four major Chinese carps

[0058]

[0059] The swimming ability data described in step S12 refers to the induced flow velocity, critical swimming speed, and burst swimming speed obtained from literature materials that match the representative body lengths of adult and juvenile fish. Generally speaking, the relative swimming speed decreases with the increase in body length, and the absolute swimming speed increases with the increase in body length. Therefore, it is very important to select the swimming ability data corresponding to the body length.

[0060] S13: Define the area where the flow velocity is less than the induced flow velocity as the non-perception area, i.e., U < U i ; define the area where the flow velocity ranges between the induced flow velocity and 0.5 times the critical swimming speed as the induction area, i.e., U i ≤ U < 0.5U c ; define the area where the flow velocity ranges between 0.5 times the critical swimming speed and the critical swimming speed as the preference area, i.e., 0.5U c ≤ U ≤ U c ; define the area where the flow velocity ranges between the critical swimming speed and the burst swimming speed as the burst area, i.e., U c < U ≤ U b ; define the area where the flow velocity is greater than the burst swimming speed as the barrier area, i.e., U > U b .

[0061] S14: Define the dimensionless flow velocity suitability index VSI to represent the suitability of the flow velocity for the migration of adult and juvenile fish. A suitability of 0 indicates that the flow velocity in this area is not suitable for fish migration, and a suitability of 1 indicates that the flow velocity in this area is most suitable for fish migration. Define the flow velocity suitability score values of the non-perception area and the barrier area as 0, and the flow velocity suitability score value of the preference area as 1.

[0062] S15: When U < U i , VSI = 0; When U i ≤ U < 0.5U c , VSI = (U - U i ) / (0.5U c - U i ); When 0.5U c ≤ U ≤ U c ,

[0063] VSI = 1; When U c < U ≤ U b , VSI = (U - U b ) / (U c - U b ); When U > U b , VSI = 0.

[0064] S16: According to the sensed flow velocities U i of adult fish and juvenile fish collected, the critical swimming speed U c and the burst swimming speed U b , respectively formulate the flow velocity suitability curves for adult fish and juvenile fish. The flow velocity zoning results and flow velocity suitability indices for adult and juvenile fish of the four major Chinese carps are shown in Table 2, and the flow velocity suitability curves are as shown in Figure 4 .

[0065] Table 2 Flow velocity zoning and flow velocity suitability indices for adult fish upstream and juvenile fish downstream

[0066]

[0067] Step S2: Numerical simulation of the flow field of the sluice control project under different flow conditions, including the following sub - steps;

[0068] S21: Establish a two - dimensional mathematical model for the long river sections upstream and downstream of the sluice control hub. The simulation range includes 2 km of the upstream river section, the sluice gate, and 3 km of the downstream river section, as shown in Figure 5 .

[0069] S22: Verify the two - dimensional mathematical model using the flow velocity data obtained from the existing physical model of the gate section.

[0070] S23: According to the regulation and operation plan of the sluice control hub, select representative flow rates to formulate calculation conditions. The selected typical conditions are: the discharge of the gate is 910 m 3 / s, the upstream water level is 17.5 m, the downstream water level is 15.17 m, and the gate opening method is: the opening of gates 1 - 6 is 1.7 m; the opening of gates 7 and 16 is 2.0 m.

[0071] S24: Calculate the upstream and downstream flow fields under typical working conditions to obtain hydraulic characteristics such as flow velocity, flow direction, and water depth.

[0072] Step S3: Prediction of the migration channels for adult fish moving upstream and juvenile fish moving downstream, including the following sub-steps;

[0073] S31: According to the flow velocity zones and flow velocity suitability curves for adult fish and juvenile fish formulated in Step S1, conduct a flow velocity suitability evaluation on the upstream and downstream flow fields of each representative working condition obtained in Step S2, so as to obtain the flow velocity suitability indices suitable for the upstream migration of adult fish and the downstream migration of juvenile fish under each representative working condition. The flow velocity zones are as Figure 6 shown.

[0074] S32: Select the flow velocity suitability index of 0.4 - 1.0 as the suitable migration channel for fish, and accordingly predict the migration channels for adult fish moving upstream and juvenile fish moving downstream. The predicted upstream and downstream migration channels are as Figure 7 shown. The gates in the typical working conditions are all partially opened. Therefore, the upstream migration channel for adult fish is that adult fish migrate from the downstream natural river to the fishway entrance and move upstream through the fishway, and the downstream migration channel for juvenile fish is that juvenile fish migrate from the upstream natural river to the opened gate and flow downstream along with the water overflowing from the top of the gate.

[0075] Step S4: According to the migration channels for adult fish moving upstream and juvenile fish moving downstream predicted in Step S3, if the migration channels are discontinuous, compare the relationship between the flow velocity in the discontinuous area and the swimming ability of fish, and change the gate opening method under the condition of constant discharge, including the following sub-steps;

[0076] S41: According to the migration channel prediction results obtained in Step S3, it can be seen that both the upstream migration channel and the downstream migration channel are discontinuous. Among them, there is a discontinuous area with a length of about 20 m in the 80 m area downstream of the fishway in the upstream migration channel, and the downstream migration channel is discontinuous at the opened Gates 1 - 7 and Gate 16. It is necessary to change the gate opening method under the condition of constant discharge.

[0077] The judgment criterion for the connectivity of the upstream migration channel in Step S41 is: from the downstream river to the fishway entrance or fully opened gate, if there is a continuous migration channel with a width exceeding twice the fish body length, it indicates that the upstream migration channel for adult fish is continuous, otherwise it is discontinuous; the judgment criterion for the connectivity of the downstream migration channel is: from the upstream river to the opened gate, if there is a continuous migration channel with a width exceeding twice the fish body length, it indicates that the downstream migration channel for juvenile fish is continuous, otherwise it is discontinuous.

[0078] S42: Analyzing the flow velocity zone results obtained in S3, it can be seen that in the discontinuous area of the upstream migration channel, that is, the 80 m area downstream of the fishway, the flow velocities all exceed the burst swimming speed, and it is necessary to reduce the discharge of Gates 1 - 6.

[0079] S43: By analyzing the flow velocity zoning results obtained in S3, it can be seen that in the discontinuous areas of the downstream migration channel, that is, at the opened gates No. 1-7 and No. 16, the flow velocities all exceed the burst swimming speed, and the discharge of a single gate needs to be reduced.

[0080] After multiple optimizations, the finally determined optimized gate operation mode is as follows: the downstream discharge is 910 m 3 / s, the upstream water level is 17.5 m, the downstream water level under the gate is 15.17 m, the opening of gates No. 1-2 is 1.7 m, the opening of gates No. 6-8 is 1.9 m, and the opening of gates No. 13-15 is 0.7 m.

[0081] S44: After adjusting the gate opening, re-evaluate the connectivity of the upstream and downstream migration channels of this working condition according to steps S2 and S3. The flow velocity zoning results are as Figure 8 shown, and the predicted migration channel results are as Figure 9 shown. It can be seen that there are continuous migration channels for adult fish going upstream and juvenile fish going downstream, and the narrowest width of the channels exceeds 10 m. Among them, adult fish can enter the fishway inlet from the left side of the downstream river channel, and juvenile fish can overflow from the top of the opened gates No. 6-8 on the right side of the upstream river channel and enter the downstream.

[0082] Based on the above-mentioned gate control hub regulation scheme that ensures the connectivity of the two-way fish passage, auxiliary fish passage devices such as fish screens and fish electric fences can be arranged at the gate control hub to improve the fish passage efficiency. Its function is to prevent the adult fish going upstream from gathering downstream of the not fully opened gates and guide the juvenile fish going downstream to pass through the appropriate gates.

[0083] The present invention proposes a gate control hub regulation method that adapts to the swimming abilities of adult fish and juvenile fish and is based on the prediction of the upstream migration channels of adult fish and the downstream migration channels of juvenile fish, and fully utilizes the characteristics of the gate control hub to solve the needs of fish for two-way migration.

[0084] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A gate control hub control method adapted to the upstream and downstream migration of multiple target fish, characterized in that: The gate control hub is used to control the water level of the river during the dry season, and adopts an operation mode of regulating the dry season but not regulating the flood season. The gate control hub includes a sluice gate and a fishway. The sluice gate adopts a pneumatic shield gate, and the gate opening is adjusted between 0 and 1. The entrance of the fishway is located on the bank below the gate. The gate discharge near the bank provides fish-attracting water flow conditions for the fishway entrance. The method includes the following steps: Step S1: Determine the flow velocity suitability curve suitable for multiple target adult fish and juvenile fish; Step S2: numerically simulate the flow field of the gate control project under different flow conditions to obtain the upstream and downstream flow fields of each representative working condition; Step S3: According to the flow velocity suitability curves of adult fish and juvenile fish determined in step S1, the flow velocity suitability of the upstream and downstream flow fields of each representative working condition obtained in step S2 is evaluated, and the migration channels of adult fish upstream and juvenile fish downstream are predicted according to the flow velocity suitability evaluation results; Step S4: Based on the migratory channels for adult fish to go up and juvenile fish to go down predicted in step S3, if the migratory channels are discontinuous, the relationship between the flow velocity in the discontinuous area and the swimming ability of the fish is compared, and the gate opening mode is changed under the condition that the discharge volume remains unchanged.

2. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 1 is characterized in that: The step S1 comprises: S11: Obtain the body lengths of adult and juvenile fish of multiple target fish species in the river section where the gate control hub project is located; S12: Obtaining swimming ability data of adult and juvenile fish of the fish object corresponding to their body length, including induced flow velocity, critical swimming speed and burst swimming speed; S13: Define the area where the flow velocity is less than the sensing flow velocity as the non-sensing area, that is, U<U i The flow velocity range between the sensing velocity and 0.5 times the critical velocity is defined as the sensing area, that is, U i ≤U<0.5U c ; Define the area between 0.5 times the critical swimming speed and the critical swimming speed as the preferred area, that is, 0.5U c ≤U≤U c ; The area between the critical swimming speed and the burst swimming speed is defined as the burst zone, that is, U c <U≤U b ; The area where the flow velocity is greater than the burst speed is defined as the barrier area, that is, U>U b ; S14: Define the dimensionless velocity suitability index VSI to represent the suitability of the velocity for the migration of adult and juvenile fish. A suitability of 0 means that the velocity in the area is not suitable for fish migration, and a suitability of 1 means that the velocity in the area is most suitable for fish migration. Define the velocity suitability score of the non-perceptible zone and barrier zone as 0, and the velocity suitability score of the preferred zone as 1; S15: When U < U i , VSI = 0; When U i ≤ U < 0.5U c , VSI = (U - U i ) / (0.5U c - U i ); When 0.5U c ≤ U ≤ U c , VSI = 1; When U c <U ≤ U b , VSI = (U - U b ) / (U c - U b ); When U > U b , VSI = 0; S16: Based on the induced flow velocity, critical swimming speed and burst swimming speed of the adult fish and the juvenile fish obtained in step S12, and the segmented flow velocity suitability index defined in step S15, flow velocity suitability curves for the adult fish and the juvenile fish are respectively formulated.

3. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 2 is characterized in that: In step S11, the body length of fish is obtained by collecting the results of fish resource surveys in the river section from literature. The principle for selecting the representative body lengths of adult fish and juvenile fish is to select smaller values ​​within the body length range. Representative body lengths of adult fish and juvenile fish are selected for multiple fish passing objects, respectively.

4. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 2 is characterized in that: The sensed flow rate U described in step S13 i is the minimum value of the flow velocity sensed by various fish species, and the critical swimming speed U c is the minimum critical swimming speed of various fish species, and the burst swimming speed U b It is the maximum value of the burst swimming speed of many fish species.

5. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 1 is characterized in that: The step S2 comprises: S21: Establish a two-dimensional or three-dimensional mathematical model of the long river section upstream and downstream of the gate control hub to simulate the flow field of the gate control project numerically. The simulation range includes the upstream river section, sluice gate and downstream river section; S22: verifying the mathematical model described in step S21; S23: According to the gate control hub regulation and operation plan, select representative flow rates to formulate calculation conditions; S24: Calculate the upstream and downstream flow fields of each working condition to obtain hydraulic characteristics, where the hydraulic characteristics include flow velocity, flow direction, and water depth.

6. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 5 is characterized in that: The mathematical model described in step S21 can simulate the discharge flow under different gate opening conditions.

7. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 5 is characterized by: Step S22 verifies the reliability of the mathematical model by obtaining hydraulic parameters through a physical model test of the same sluice control hub.

8. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 1 is characterized by: The step S3 comprises: S31: According to the flow velocity suitability curves for adult fish and juvenile fish developed in step S1, the flow velocity suitability of the upstream and downstream flow fields of each representative working condition obtained in step S2 is evaluated, so as to obtain the distribution of flow velocity suitability suitable for adult fish to go up and juvenile fish to go down under each representative working condition; S32: Select flow velocity suitability index 0.4-1.0 as suitable fish migration channel, and predict the migration channel for adult fish upstream and juvenile fish downstream based on it. There are two types of adult fish upstream migration channel, one is that adult fish migrate from the downstream natural river channel to the fishway entrance and upstream through the fishway, the other is that adult fish migrate from the downstream natural river channel to the open gate and upstream through the fully open gate; the juvenile fish downstream migration channel of the gate control hub refers to the juvenile fish migrating from the upstream natural river channel to the open gate and overflowing through the gate top and downstream with the water flow.

9. The gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 1 is characterized in that: The step S4 comprises: S41: Identify the connectivity of the upstream and downstream migration channels of fish in each representative working condition. When the migration channel is discontinuous, it is necessary to change the gate opening method while keeping the discharge flow unchanged. Specifically: S42: When the upstream migration channel is discontinuous, if the flow velocity in the discontinuous area is close to the burst swimming speed of adult fish, the opening of the gate at the corresponding position on the streamline of the area is reduced; if the flow velocity in the discontinuous area is close to the induced flow velocity of adult fish, the opening of the gate at the corresponding position on the streamline of the area is increased; S43: When the downstream migration channel is discontinuous, if the flow velocity in the discontinuous area is close to the burst swimming velocity of the juvenile fish, the opening of the gate at the corresponding position on the streamline of the area is reduced; if the flow velocity in the discontinuous area is close to the induced flow velocity of the juvenile fish, the opening of the gate at the corresponding position on the streamline of the area is increased; S44: After adjusting the gate opening, the connectivity of the upstream and downstream migratory channels of the working condition is re-predicted according to steps S2 and S3 until both the upstream and downstream migratory channels are continuous.

10. A gate control hub control method adapted to the upstream and downstream migration of multiple target fish species according to claim 9, characterized in that: In step S41, the connectivity judgment standard of the upstream migratory channel is: from the downstream river channel to the fishway entrance or the fully open gate, if there is a migratory channel with a width exceeding twice the fish body and is continuous and uninterrupted, it indicates that the upstream migratory channel of adult fish is continuous, otherwise it is discontinuous; the connectivity judgment standard of the downstream migratory channel is: from the upstream river channel to the open gate, if there is a migratory channel with a width exceeding two fish bodies and is continuous and uninterrupted, it indicates that the downstream migratory channel of juvenile fish is continuous, otherwise it is discontinuous.

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