Central arrangement and natural fish guiding structure of fish entrance of large-amplitude water level fishway

Abstract

This invention belongs to the field of ecological restoration technology in water conservancy engineering, specifically involving a fishway inlet centralized layout and natural fish-guiding structure adapted to large-amplitude water levels. It includes a fishway inlet group centrally arranged along the bank slope of the tailrace channel of a power plant, a vertically slit-type fishway main body, and a water replenishment and control system. The inlet group comprises multiple independent inlets arranged along an elevation gradient. Elevation differences are offset by fishway sections with a reversible structure, ensuring all inlets are centrally located within a certain range in the core fish-gathering area. The water replenishment and control system's flow rate is inversely correlated with the real-time water depth and natural flow rate within the fishway. Combined with the natural flow field of the tailrace channel, a natural fish-guiding path without a cross-river electric guide is constructed. This invention solves the problems of dispersed inlets, ecological stress in fish-guiding methods, and disconnected water replenishment and control logic in traditional designs. It achieves precise matching between the inlets and the natural migration paths of fish, significantly improving fish passage efficiency.

Description

Technical Field

[0001] This invention belongs to the field of ecological restoration technology for water conservancy projects, specifically involving a fish passage with centralized fish inlet arrangement and natural fish guiding structure adapted to large water level fluctuations. Background Technology

[0002] While water conservancy projects provide comprehensive benefits such as flood control, power generation, navigation, and water resource allocation, they can also create lateral barriers to natural rivers, disrupt fish migration routes, and lead to a series of ecological problems, including degradation of fish spawning grounds, decline in genetic resources, and reduction in aquatic biodiversity. Fishways are one of the core engineering measures for solving ecological barriers in water conservancy projects and restoring longitudinal connectivity of rivers. The fish inlet is the only passage for fish to find and enter the fishway, and its spatial layout, fish guiding methods, and supporting water replenishment and regulation logic directly determine the overall fish passage efficiency of the fishway.

[0003] The existing fishway inlet designs for downstream hydraulic engineering projects with large downstream water level fluctuations generally suffer from the following common technical defects in the industry:

[0004] 1) The fish inlets are distributed in a gradient manner, and some fish inlets are far away from the core fish gathering area: In order to adapt to the large fluctuations in water level downstream, multiple fish inlets at different elevations are set up. Due to the elevation difference and the longitudinal slope of the fish passage, multiple fish inlets must be distributed in a range of hundreds to thousands of meters downstream of the dam. Some fish inlets are far away from the natural fish gathering area formed by the tailrace of the hub powerhouse, resulting in a low fish passage guarantee rate; Insufficient adaptability to all water levels, which easily leads to the interruption of the migration channel: The elevation coverage of the fish inlets is insufficient and cannot fully adapt to the large changes in downstream water level. The fish inlets are prone to being submerged or exposed, which leads to the interruption of the fish migration channel.

[0005] 2) The fish guiding method is subject to ecological stress and has poor operational stability: In order to guide fish into the fish inlet, the Hengjiang fish guiding electric fence is used. However, the electric fence will exert strong behavioral stress on nationally protected species such as eel and Japanese eel, as well as juvenile fish. At the same time, affected by river siltation, large water level changes, and flood discharge, the electric fence has extremely poor operational stability and is easily damaged, and cannot achieve the expected fish guiding effect.

[0006] 3) The logic of water replenishment flow control is seriously out of touch with the actual engineering practice: First, there is insufficient understanding of the core role of water replenishment flow. Water replenishment is only regarded as an auxiliary means to supplement the flow velocity. It ignores that the water replenishment flow at the fish passage inlet is extremely small compared with the flow of the power generation tailwater. Sufficient water replenishment flow must be used to form a differentiated flow velocity gradient so that fish can identify the fish inlet in a strong background flow field. Second, the control logic is flawed. The water replenishment flow is mistakenly directly linked to the upstream and downstream water levels. It ignores that the core determining factor of the natural flow rate in the fish passage is the real-time water depth in the fish passage. This results in insufficient water replenishment under low water depth and low flow rate. The fish-attracting water flow signal is completely submerged by the power generation tailwater, and the fish cannot find the fish inlet.

[0007] Currently, existing technologies for optimizing fish passage inlets mainly focus on hydraulic adjustments of local structures. They fail to address the core pain points of mismatch between fish inlets and natural fish migration paths, ecological stress of fish guidance methods, and disconnect between water replenishment regulation logic and engineering practice, based on the natural migration habits of target fish, the distribution patterns of river flow fields, and the core mechanisms of fish passage flow. As a result, they cannot meet the actual engineering needs of aquatic life protection in downstream water conservancy projects with large fluctuations in water levels. Summary of the Invention

[0008] The purpose of this invention is to provide a fishway inlet centralized arrangement and natural fish-guiding structure adapted to large water level fluctuations. Starting from the natural migration habits of target fish and the core mechanism of fishway flow, the invention solves the industry pain points of poor fish attraction effect, high ecological stress risk, insufficient adaptability to all water levels, and disconnection of water replenishment logic in existing fishway inlets by using a centralized gradient arrangement of fish inlets, combined with natural flow field fish guidance and precise control of water replenishment flow based on fishway flow capacity. This achieves precise matching between fish inlets and natural fish gathering areas, migration paths, and fishway flow characteristics.

[0009] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0010] This invention provides a fishway fish inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations, including a fishway fish inlet group centrally arranged along the bank slope of the tailrace channel of the hub plant, a vertical slit fishway main body connected to the fish inlet group, and a water replenishment and control system matched with the fish inlet group.

[0011] The fish passage inlet group includes multiple independent fish inlets arranged in a gradient from low to high elevation along the water flow direction. All fish inlets are concentrated in the core fish gathering area of ​​the tailwater channel of the plant, and the overall concentrated arrangement length does not exceed 200m.

[0012] The main body of the vertical slot fishway includes a zigzag or U-shaped fishway section corresponding to each fish inlet. The zigzag or U-shaped fishway section offsets the elevation difference of each fish inlet through a reversing structure, realizing a concentrated and compact arrangement of multiple gradient fish inlets. The outlet end of the main body of the vertical slot fishway is divided into a flood season fishway section and a non-flood season fishway section. An openable and closable switching gate is set between the two sections. The upstream fish outlet of the main body of the fishway is arranged according to the upstream reservoir water level gradient.

[0013] Each fish inlet is set along the downstream water level gradient of the hub, covering the entire operating water level range during non-flood discharge periods of the hub;

[0014] The outflow end of the water replenishment control system is connected to the front-end pool chamber of the corresponding fish inlet, and the water replenishment end is connected to the upstream reservoir area of ​​the hub. The water replenishment flow rate is inversely correlated with the real-time water depth and natural flow rate in the fishway. It is used to accurately control the water replenishment flow rate according to the water depth changes in the fishway, forming a continuous and stable fish-attracting water flow signal at the fish inlet. Combined with the natural outflow of the tailwater channel of the plant, it constructs a natural fish-guiding path without the cross-river fish-guiding electric grid.

[0015] Furthermore, the fishway inlet group includes four independent fish inlets, all of which are located within 200m of the right bank retaining wall of the tailrace outlet of the hub plant.

[0016] Furthermore, the four independent fish inlets are designated as #1, #2, #3, and #4, with the bottom elevation of the sluice gate increasing sequentially. The #1 fish inlet corresponds to the lowest water level of the sluice gate, while the #4 fish inlet corresponds to the highest water level of the sluice gate during non-flood discharge periods. Together, the four fish inlets cover the range from the lowest to the highest water level downstream of the sluice gate.

[0017] Furthermore, the longitudinal slope of the main body of the vertical slot fishway is selected according to the specifications. The standard pool room adopts a cross vertical slot partition structure, and a flat-bottomed resting pool without partition is set every 15 to 20 standard pool rooms along the length of the fishway.

[0018] Furthermore, the non-flood season fishway section is equipped with three upstream fish outlets arranged along the elevation gradient, corresponding to the reservoir water level operation range during the non-flood season of the hub; the flood season fishway section is equipped with at least one upstream fish outlet, corresponding to the flood control limit water level range during the flood season of the hub.

[0019] Furthermore, the water replenishment and control system includes a water replenishment pipeline, a water replenishment pool, and a flow control valve. The water inlet of the water replenishment pipeline is connected to the upstream reservoir area, and the water outlet is connected to the water replenishment pool. The water outlet of the water replenishment pool is connected to the water replenishment and energy dissipation pool at the front end of the fish inlet. The flow control valve is installed on the water replenishment pipeline.

[0020] Furthermore, during the operation of the fishway, only one fish inlet that matches the real-time water level downstream is opened, while the gates of the other fish inlets are completely closed; the water replenishment flow of the water replenishment control system is used to stably control the average flow velocity at the fish inlet cross-section within the inlet fish attraction flow velocity control range of 0.45m / s to 1.19m / s.

[0021] Furthermore, the flow control logic of the water replenishment control system is as follows: determine the current period, match the opening and closing of the connection port, collect the reservoir water level and downstream tailwater water level in real time, and match the opening and closing of the fish outlet and fish inlet; match the water replenishment flow rate by monitoring the flow rate, water depth and fish inlet flow velocity in the fish passage; automatically increase the water replenishment flow rate when the flow velocity at the fish inlet section is lower than 0.45m / s, and automatically decrease the water replenishment flow rate when the flow velocity exceeds 1.19m / s.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention is the first to use a zigzag (or U-shaped) fishway section to offset the elevation difference of different fish inlets. It concentrates all fish inlets with different elevations in the core fish gathering area of ​​the tailrace channel of the plant. The overall arrangement length does not exceed 200m. This completely breaks the technical prejudice of the traditional design that "gradient fish inlets must be distributed". Fish can directly reach the fish inlets by following the water flow of the tailrace channel. This is in line with the fish's habit of swimming upstream in the flowing water during the breeding season. It is predicted that they will swim upstream along one side of the river (the original main river channel) until the downstream end of the physical barrier (near the tailrace channel of the plant). This greatly improves the probability of fish entering the fishway from the structural source.

[0024] 2. This invention completely eliminates the traditional electric fish guide grid in Hengjiang. Relying on the continuous velocity gradient formed by the natural outflow of the tailrace channel of the plant, and the stable fish-attracting water flow formed by the water replenishment and control system, a natural fish-guided path that perfectly matches the natural flow-attracting habits of fish is constructed. This not only completely eliminates the behavioral stress of the electric grid on sensitive protected species, but also significantly reduces the engineering operation and maintenance costs.

[0025] 3. This invention, by arranging multiple fish inlets along an elevation gradient, covers the entire operating water level from the lowest to the highest water level during non-flood discharge periods of the hub. Combined with the fish passage during flood season / non-flood season, it can adapt to large water level fluctuations downstream of the hub, eliminate the ecological risk of interruption of the migration channel, and meet the year-round migration needs of fish.

[0026] 4. This invention overcomes the shortcomings of traditional water replenishment design being disconnected from engineering practice. It anchors the engineering practice that "the core of the natural flow rate in the fish passage is determined by the real-time water depth" and establishes a precise reverse correlation control logic of "fish passage water depth → natural flow rate → water replenishment flow rate". It clarifies that during operation, a large flow rate of water replenishment is given priority within the swimming capacity of fish. This completely solves the core problems of insufficient water replenishment at low water depths and the fish attraction signal being submerged by tailwater in traditional designs, and greatly improves the probability of fish entering the water.

[0027] 5. The reversible centralized layout structure and control logic of the present invention do not require complicated construction technology and do not increase additional engineering investment. It can be applied to the design of fish passages for newly built downstream water conservancy hubs with large fluctuations in water level, and can also be used for the renovation and upgrading of fish inlets of existing fish passages. It provides a replicable and scalable complete set of technical solutions for the repair of fish migration channels in cascade water conservancy hubs in my country's river basins.

[0028] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the centralized arrangement of fish inlets in the fish passage according to the present invention;

[0031] Figure 2 This is a schematic elevation view of the fish inlet elevation gradient arrangement of the present invention;

[0032] Figure 3 This is a schematic diagram of the natural fish-guiding path and flow velocity gradient distribution of the present invention;

[0033] Figure 4 This is a schematic diagram showing the connection between the water replenishment and regulation system of the present invention and the main body of the fish passage;

[0034] Figure 5 This is a block diagram of the water replenishment flow control logic of the present invention;

[0035] In the attached diagram, the component numbers are as follows:

[0036] 1-Fishway inlet, 1-1-#1 fishway inlet, 1-2-#2 fishway inlet, 1-3-#3 fishway inlet, 1-4-#4 fishway inlet; 2-Water replenishment and energy dissipation pool, 2-1-#1 water replenishment and energy dissipation pool, 2-2-#2 water replenishment and energy dissipation pool, 2-3-#3 water replenishment and energy dissipation pool, 2-4-#4 water replenishment and energy dissipation pool; 3-Vertical slotted fishway, 3-1 vertical slot, 3-2 - Pool chamber, 3-3- Resting pool, 3-4- Pool chamber side wall, 4- Plant area retaining wall, 5- Tailwater channel, 6- Plant area platform, 7- Installation room, 8- Power plant building, 9- Inlet maintenance gate, 10- Water supply steel pipe, 10-1-#1 water supply steel pipe, 10-2-#2 water supply steel pipe, 10-3-#3 water supply steel pipe, 10-4-#4 water supply steel pipe, 11- Flow control valve. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figures 1-2As shown, this embodiment provides a centralized arrangement of fish inlets and a natural fish-guiding structure for a hub with large downstream water level fluctuations. It includes fish inlets 1, a reversible inlet connecting section, a vertical slit fishway 3, and a water replenishment and control system that is matched with each fish inlet 1, all arranged along the bank slope of the retaining wall 4 of the hub plant area. The entire structure is located on the bank of the plant platform 6 downstream of the power plant 8 and the installation room 7, adjacent to the core fish gathering area of ​​the tailrace channel 5 outlet. The total length of all fish inlets does not exceed 200m and is completely within 200m to the right of the tailrace channel 5 outlet.

[0039] like Figures 1-2 As shown, the fishway inlet 1 includes four independent fish inlets arranged in a gradient from low to high according to the bottom elevation of the gate, namely #1 fishway inlet 1-1, #2 fishway inlet 1-2, #3 fishway inlet 1-3, and #4 fishway inlet 1-4. The bottom elevation of each fish inlet is precisely matched with the downstream water level variation of the hub, covering the entire operating water level range of the hub during non-flood discharge periods. The four fish inlets at different elevations are independently connected to the vertical slot fishway 3 through corresponding zigzag-shaped reversible inlet connecting sections. The reversible structure cancels out the maximum elevation difference of 1.77m between the fish inlets, achieving a concentrated and compact arrangement of multi-gradient fish inlets without extending the arrangement distance along the river channel.

[0040] like Figures 1-2 As shown, the vertical slot fishway 3 adopts a pure vertical slot structure with a designed longitudinal slope of 1:80. It is divided into a flood season fishway section and a non-flood season fishway section, with a switch gate that can be opened and closed between the two sections. The main body of the fishway consists of continuously arranged pool chambers 3-2 and pool chamber sidewalls 3-4. Vertical slots 3-1 are arranged in a cross pattern between adjacent pool chambers 3-2. The standard pool chamber 3-2 has a net length of 6m, a net width of 5m, and a designed water depth of 3m. The vertical slot 3-1 is 1m wide. Along the length of the fishway, every 18 standard pool chambers 3-2, there is a 12m long flat-bottomed, unpartitioned resting pool 3-3, providing a slow-flowing resting space for fish migrating upstream over long distances, reducing fatigue mortality. There are 4 fish outlets upstream of the vertical slot fishway 3, arranged according to the reservoir water level gradient. The independent operation of the fishway during the flood season and the non-flood season is achieved by switching gates, ensuring unobstructed migration channels throughout the year.

[0041] like Figure 1 , Figure 4As shown, the water replenishment and control system is set up in conjunction with the four fish inlets. Each water replenishment branch includes an inlet maintenance gate 9, a water replenishment steel pipe 10, a flow control valve 11, and a water replenishment energy dissipation pool 2. The water replenishment steel pipe 10 is divided into #1 water replenishment steel pipe 10-1, #2 water replenishment steel pipe 10-2, #3 water replenishment steel pipe 10-3, and #4 water replenishment steel pipe 10-4, corresponding to each fish inlet. The water replenishment energy dissipation pool 2 is divided into #1 water replenishment energy dissipation pool 2-1, #2 water replenishment energy dissipation pool 2-2, #3 water replenishment energy dissipation pool 2-3, and #4 water replenishment energy dissipation pool 2-4, corresponding to each fish inlet. The inlet end of the water supply steel pipe 10 connects to the upstream reservoir area of ​​the hub. An inlet maintenance gate 9 is installed at the inlet to cut off the water flow during equipment maintenance. A flow control valve 11 is installed on the water supply steel pipe 10 for remote and precise control of the water supply flow. The outlet end of the water supply steel pipe 10 connects to the corresponding water supply energy dissipation pool 2, and the outlet end of the water supply energy dissipation pool 2 connects to the front chamber of the corresponding fish passage inlet 1. The maximum water supply capacity of the entire water supply control system is determined by the structural dimensions of the fish passage inlet 1 and the flow capacity of the water supply steel pipe 10. It can maximize the enhancement of the fish-attracting water flow signal without disrupting the flow pattern at the fish passage inlet, thus solving the problem that fish cannot identify the fish passage under the background of large flow of power generation tailwater.

[0042] like Figure 3 As shown, in this embodiment, no electric fish guide grids are installed at any of the fishway inlets 1. Instead, a continuous natural fish-guiding path is constructed from the core gathering area of ​​the tailrace channel 5 to the fishway inlets 1, relying on the velocity gradient formed by the natural outflow of the tailrace channel 5 and the stable fish-attracting flow formed by the water replenishment and control system. The area directly in front of the tailrace channel 5 outlet is a high-speed flow zone, while the bank near the plant retaining wall 4 is a low-speed suitable zone. Fish can naturally swim upstream along the low-speed suitable zone on the bank and directly reach the centrally arranged fishway inlets 1, thus completely eliminating the behavioral stress on fish caused by the fish-guiding facilities.

[0043] like Figure 5 As shown, the operation scheduling and natural fish guidance method in this embodiment fully conforms to the actual operation principles of fishways. The specific steps are as follows:

[0044] Operating mode switching: Determine the current stage of the fishway and adjust the opening and closing of the connection port accordingly.

[0045] Precise opening and closing of fish inlets: Based on the real-time water level downstream and the discharge flow of the hub, only one fish inlet 1 at the corresponding elevation is opened, while the gates of the other three fish inlets remain fully closed to avoid turbulent flow and uncontrolled flow velocity in the vertical slit fishway 3 caused by opening multiple inlets; when the water level changes, the principle of "opening the gate at the new elevation first and then closing the gate at the lower elevation" is followed to avoid sudden changes in water level and flow velocity in the fishway that could stress the fish.

[0046] Closed-loop precise control of water replenishment flow: Real-time data on flow rate, water depth, and cross-sectional flow velocity at the fish inlet 1 of the vertical slotted fishway 3 are collected. The minimum inlet fish attraction velocity of 0.45 m / s and the maximum inlet fish attraction velocity of 1.19 m / s are used as control thresholds. The water replenishment flow rate is precisely adjusted through the flow control valve 11. The core logic is that "the smaller the water depth in the fishway, the smaller the natural flow rate, and the larger the water replenishment flow rate, the higher the design limit should be."

[0047] During operation, when the flow velocity at the fish inlet section 1 is lower than 0.45 m / s, the water supply flow rate is automatically increased within the design limit; when the flow velocity exceeds 1.19 m / s, the water supply flow rate is automatically reduced to ensure that a clear and stable fish-attracting water flow signal is always formed at the fish inlet, which, together with the natural flow field of the tailrace channel 5, enhances the fish-guiding effect.

[0048] This embodiment, through physical model experiments and actual engineering operation verification, shows that the optimized zigzag centralized layout structure and water replenishment control system can achieve a 100% compliance rate of flow velocity at the fish passage inlet section 1, with no interruption of the migration channel throughout the year. The fish passage effect reaches the leading level in China and fully meets the ecological needs of aquatic life protection in the basin.

[0049] Under different water level variations and depths, whether the flow velocity at the fish inlet cross-section meets the fish-attracting flow velocity control range of 0.45~1.19 m / s at the fishway inlet was investigated. Data source: "Research on the Swimming Ability Test of Major Fish Species in the Fish Passage Facility of Datengxia Hydropower Project", Pearl River Water Resources Protection Research Institute and Institute of Hydro-Engineering Ecology, Chinese Academy of Sciences, Ministry of Water Resources, 2016. The comparison before and after water replenishment is shown in Table 1 below. The data are based on the flow data measured by model experiments and the operation mode of the fishway.

[0050] Table 1

[0051]

[0052]

[0053]

[0054] This embodiment is applied to the Qianjiang Fishway of the Datengxia Hydropower Project. The Qianjiang Fishway was put into operation in 2023, and its operation from 2023 to 2026 yielded significant results, demonstrating substantial ecological benefits and long-term economic value. In terms of ecological effectiveness, a total of 95 fish species have been recorded in the downstream waters, with a stable and healthy community structure. A total of 49 fish species have been monitored within the fishway, with native species accounting for 85.71%. Not only were rare species previously unrecorded downstream, such as the large-eyed wrasse and the black carp, discovered, but in April 2026, the rare and endemic species of the Chinese loach, the Bai's thin-skinned loach, was also detected for the first time, filling a gap in the distribution information of this species in the Qianjiang section of the Xijiang River. Significant progress has been made in the protection of rare and economically important fish species. The population of the spotted catfish, a national second-class protected animal, has increased significantly. In 2024, its successful upstream migration was recorded for the first time, with a single species pass rate of 33.33%. By 2025, it had become a common species downstream of the dam. Major economically important fish species such as black carp, silver carp, and bighead carp can all complete their migrations via the fishway. During the peak flood season, an average of 1,872 fish migrated upstream daily. The PIT marker verification fishway showed an overall success rate of 10.34%, with fish species completing their upstream migration within 1-8 days. In terms of economic benefits, the fishway has opened up migration channels for core economically important fish species in the Xijiang River basin, ensuring the natural propagation and sustainable production of fishery resources. It has also reduced the ecological compensation costs for the protection of rare aquatic organisms, enhanced the value of the basin's ecological assets, and provided a replicable benchmark experience for the ecological operation of large-scale water conservancy projects in my country.

[0055] The upstream and downstream water levels determine the opening and closing of the fish passage's inlet and outlet. However, the combination of operating conditions caused by different water levels is too numerous, which is not conducive to the real-time control and operation management of the Qianjiang fish passage. In order to simplify the operation mode while meeting the requirements for fish passage, the water replenishment volume is determined by the water depth and flow rate corresponding to the four characteristic water levels upstream and the downstream water level.

[0056] The scheduling of water supply pipes must meet the following principles:

[0057] 1. Based on the downstream water level E 下 Opening and closing corresponds to the fish inlet.

[0058] 2. Calculate the inlet water depth D of the opened fishway:

[0059] D=E 下 -Ei

[0060] D - Fishway inlet water depth;

[0061] Ei - Elevation of the bottom plate of each fish inlet

[0062] 3. Calculate the flow rate range Q that meets the inlet velocity requirements. i :

[0063] Q i = v i ×D×B

[0064] v i- Flow rate at each fish inlet;

[0065] B - Width of the fish passage inlet;

[0066] 4. Calculate the water supply flow rate Q of the water supply pipe. bi :

[0067] Q bi = Q i -Q5

[0068] Q bi - Water supply flow rate of the water supply pipe, ranging from 0 to 3 m³ / s;

[0069] Q i - Fish inlet flow rate,

[0070] The flow rate measured at point Q5 (near the inlet).

[0071] Multiple groups (D, Q) bi Curve fitting was performed on the data. Preliminary Q... bi It may have a linear relationship with D and Q5, that is, Q bi =k1×v i ×D×B-k2×Q5+C. Where k, n, and C are undetermined coefficients and exponents, respectively, determined through regression analysis.

[0072] Considering factors such as downstream tailwater flow velocity and water temperature (which affect fish activity), a comprehensive correction coefficient α can be introduced, evolving the formula to: Q bi =α×k1×v i ×D×B-k2×Q5+C. α can be determined through big data learning or fuzzy control rules.

[0073] The relevant arrangement in this embodiment is as follows:

[0074] 1) Arrangement of fish inlet group:

[0075] Arrangement length: Strictly controlled within 200 meters, with the optimal range being 150-200 meters. During construction, precise measurements and layout are required to ensure that all fish inlets are located within 200 meters of the factory's tailwater outlet, in the core fish gathering area.

[0076] Elevation Determination: Based on historical water level data from downstream of the hub during non-flood seasons, determine the minimum and maximum operating water levels. The bottom elevations of the four fish inlets should be arranged with equal gradients or optimized gradients according to a guaranteed rate within this range. During construction, the elevation error of the bottom plate of each fish inlet should be controlled within ±1 cm.

[0077] 2) Vertical slotted fishway main body:

[0078] Longitudinal slope: The base slab is poured at a slope of 1:80. This is a proven and optimal slope that balances the fish's ability to swim upstream with the amount of work required.

[0079] Structural construction: Standardized formwork is used to pour the side walls and partitions of the pool chambers, ensuring that all vertical joints are 1 meter wide with an error of ±0.5 cm. A rest pool (12 meters long) is set up every 15 to 20 standard pool chambers (6 meters each), and the positioning must be accurate.

[0080] Construction of the turnaround section: The zigzag or U-shaped connecting section is key to offsetting the elevation difference at the fish inlet and achieving a compact layout. Specialized hydraulic calculations and model tests are required to ensure smooth flow in the turning section and controllable local head loss.

[0081] 3) Installation and commissioning of the water replenishment and control system:

[0082] Pipeline installation: The routing and support installation of water supply pipelines (such as steel pipes) require hydraulic transition calculations to avoid vibration and cavitation. Sufficient straight pipe sections must be ensured before and after the flow control valves to guarantee flow measurement accuracy.

[0083] Sensor placement: A flow meter and a depth meter must be installed in the front chamber of each fish inlet, and the signals are connected to the central control system.

[0084] 4) Standardization of debugging process:

[0085] a. Standalone debugging: Check valve opening and closing, and sensor signals.

[0086] b. Static linkage debugging: In the absence of water, the test control system automatically selects and opens the corresponding fish inlet gate based on the simulated water level signal.

[0087] c. Dynamic hydraulic adjustment: After water flow, first shut off the water supply and measure the natural flow rate Q0 of the fish passage and the flow velocity v0 at the fish inlet at each water level. Then, gradually turn on the water supply to establish the water supply flow rate Q. b The field calibration curve of the fish inlet flow velocity v.

[0088] d. Closed-loop trial operation: Put the system into automatic control mode to verify whether it can automatically adjust the water supply valve according to the real-time flow velocity v (control target: 0.45~1.19 m / s) and observe whether the transition process when switching between different water levels is smooth.

[0089] 5) Standardized construction process

[0090] Measurement and layout: Accurately locate all fish inlets, fishway axes, turning points, resting pools, and outlets.

[0091] Earthwork and foundation engineering: Excavation and foundation treatment shall be carried out with a longitudinal slope of 1:80.

[0092] Structural casting: First, the fishway base slab is cast, then the pool side walls, vertical partitions, resting pool, and fish inlet structure are cast sequentially using standardized templates. Customized templates are used for the turnaround section.

[0093] Metal structure and piping installation: Installation of fish inlet gate, water supply system piping, valves and sensors.

[0094] Civil engineering backfilling and decoration: backfilling around the structure, construction observation and maintenance access.

[0095] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fish passageway with centralized fish inlet arrangement and natural fish guiding structure adapted to large water level fluctuations, characterized in that, It includes a fishway inlet group centrally arranged along the bank slope of the tailrace channel of the pivot powerhouse, a vertical-slot fishway main body connected to the fishway inlet group, and a water replenishment regulation and control system supporting the fishway inlet group; The fishway inlet group includes multiple independent inlets arranged in a gradient manner in the water flow direction and from low to high in elevation. All inlets are centrally arranged within the core fish aggregation area of the tailrace channel of the powerhouse, and the overall centralized arrangement length does not exceed 200m; The vertical-slot fishway main body includes zigzag or U-shaped fishway sections corresponding to each inlet. The zigzag or U-shaped fishway sections offset the elevation differences of each inlet through a turning-back structure to achieve a concentrated and compact arrangement of multi-gradient inlets. The outlet end of the vertical-slot fishway main body is divided into a flood-season fishway section and a non-flood-season fishway section. A switchable gate is arranged between the two sections. The upstream fish outlet of the fishway main body is arranged according to the upstream reservoir water level gradient; Each inlet is arranged along the gradient of the downstream water level variation of the pivot, covering the full operating water level range during the non-flood discharge period of the pivot; The outlet end of the water replenishment regulation and control system is connected to the front pool chamber of the corresponding inlet, and the water replenishment end is connected to the upstream reservoir area of the pivot. The water replenishment flow rate is inversely related to the real-time water depth and natural discharge flow rate in the fishway, and is used to accurately regulate the water replenishment flow rate according to the water depth change in the fishway, forming a continuous and stable fish-attracting water flow signal at the inlet, and cooperating with the natural discharge of the tailrace channel of the powerhouse to construct a natural fish guiding path without a cross-river fish guiding electric grid.

2. The fish passage with centralized fish inlet arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, The fishway inlet group includes 4 independent inlets, all of which are arranged within 200m of the right bank retaining wall at the outlet of the tailrace channel of the pivot powerhouse; 3. The fish passage inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 2, characterized in that, The 4 independent inlets are #1 inlet, #2 inlet, #3 inlet, and #4 inlet respectively, and the bottom elevation of the gates increases in sequence; #1 inlet is adapted to the lowest water level of the pivot, and #4 inlet corresponds to the highest water level of the pivot during the non-flood discharge period. The 4 inlets jointly cover the range from the lowest water level to the highest water level downstream of the pivot; 4. The fish passage with centralized fish inlet arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, The designed longitudinal slope of the vertical-slot fishway main body is selected according to the specification requirements. The standard pool chamber adopts a cross vertical-slot partition structure, and a rest pool without partitions and with a flat bottom is arranged every 15 - 20 standard pool chambers along the fishway length direction; 5. The fish passage inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, The non-flood-season fishway section has 3 upstream fish outlets arranged along the elevation gradient, corresponding to the non-flood-season reservoir water level operating range of the pivot; the flood-season fishway section has at least 1 upstream fish outlet, corresponding to the flood control limited water level range of the pivot during the flood season; 6. The fish passage inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, The water replenishment regulation and control system includes a water replenishment pipeline, a water replenishment pool, and a flow regulation valve. The water inlet end of the water replenishment pipeline is connected to the upstream reservoir area, the water outlet end is connected to the water replenishment pool, the water outlet end of the water replenishment pool is connected to the front water replenishment energy dissipation pool of the inlet, and the flow regulation valve is arranged on the water replenishment pipeline; 7. The fish passageway fish inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, During the operation period of the fishway, only 1 inlet matching the downstream real-time water level is opened, and the gates of the remaining inlets are fully closed; the water replenishment flow rate of the water replenishment regulation and control system is used to stably control the average flow velocity at the inlet cross-section within the inlet fish-attracting flow velocity control range of 0.45m / s - 1.19m / s.

8. The fish passage inlet centralized arrangement and natural fish guiding structure adapted to large water level fluctuations as described in claim 1, characterized in that, The flow control logic of the water replenishment control system is as follows: determine the current period, match the opening and closing of the connection port, collect the reservoir water level and downstream tailwater water level in real time, and match the opening and closing of the fish outlet and fish inlet; match the water replenishment flow rate by monitoring the flow rate, water depth and fish inlet flow velocity in the fish passage; automatically increase the water replenishment flow rate when the flow velocity at the fish inlet section is lower than 0.45m / s, and automatically decrease the water replenishment flow rate when the flow velocity exceeds 1.19m / s.

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