A fish passing system adaptive to large water level fluctuation downstream of dam

Abstract

This invention provides a fish passage system and method adapted to large water level fluctuations downstream of a dam, relating to the field of fish passage facilities in hydraulic engineering. The fish passage system includes: a fishway on the dam, with at least two independently operable fishway inlets at different elevations downstream of the dam; and a water supply system for providing fish-attracting water flow to each inlet. This invention solves the problem of fishway inlet failure caused by large downstream water level fluctuations in existing technologies, achieving continuous and efficient fish passage under all water level conditions.

Description

Technical Field

[0001] This invention relates to the field of fish passage facilities in water conservancy projects, and in particular to a fish passage system that adapts to large water level fluctuations downstream of a dam. Background Technology

[0002] With the continuous construction of water conservancy and hydropower projects, dams and other hydraulic structures have disrupted the continuity of rivers, posing a serious threat to the survival and reproduction of migratory fish. To restore river ecological connectivity, fish passage facilities (such as fishways) have become an important engineering remedial measure. Currently, the mainstream trend in fishway design is to pursue higher fish passage efficiency and wider adaptability to cope with complex and variable river hydrological conditions. However, in practical engineering applications, especially in high-head, high-flow-rate projects with drastic downstream water level fluctuations, traditional fishways face severe technical challenges.

[0003] Currently, there has been relevant research in the industry regarding the adaptability of fishway inlet water level. For example, an existing technical solution (publication number: CN120906102A) discloses a flow diversion system and its operation method that adapts to the fluctuation of fishway inlet water level, belonging to the field of water conservancy and hydropower ecological protection technology. This flow diversion system includes a fishway, a water level and flow velocity monitoring device, a diversion outlet device, branch diversion pipes and valves, a main diversion pipe and a main valve. The diversion outlet device is arranged at the bottom of a section of the pool or resting room near the downstream fishway inlet and is connected to the branch diversion pipes. The flow rate at the end of each branch diversion pipe is controlled by a valve. All branch diversion pipes converge into a main diversion pipe arranged along the length of the fishway sidewall, and a main valve is provided at the end of the main diversion pipe. A water level and flow velocity monitoring device is arranged in the pool room to control the opening and closing amplitude of the valve in real time, thereby realizing the dynamic adjustment of the diversion flow rate. This invention reduces the water level difference and vertical slit velocity in the inlet section of the pool by diverting the flow along the fishway, thus improving the adaptability of the fishway inlet water level fluctuation.

[0004] However, the aforementioned existing technical solutions still have significant limitations in practical applications. The core issue is that these solutions can only optimize the fish-attracting water flow at a single fixed fishway inlet, and cannot fundamentally solve the problem of insufficient submersion depth or fishway inlet being removed from the water surface due to large fluctuations in downstream water levels, thus preventing fish from effectively finding and entering the fishway. When water levels change drastically, these solutions cannot guarantee that the fishway inlet is always in optimal hydraulic conditions, resulting in large fluctuations in fish passage efficiency under different water level conditions, and even temporary failures. This fails to meet the fundamental requirement of ecological protection for the efficient operation of fish passage facilities around the clock and under all operating conditions. Therefore, there is an urgent need in this field for a solution that can solve the above problems. Summary of the Invention

[0005] In view of the problem in the existing technology that the fish passage inlet is not submerged enough or is removed from the water surface due to large changes in the downstream water level, which leads to large fluctuations in fish passage efficiency or even temporary failure, the present invention provides a fish passage system and method that can adapt to large water level fluctuations downstream of the dam.

[0006] The present invention provides the following technical solution to achieve the above objectives: A fish passage system adapted to large water level fluctuations downstream of a dam includes a dam with a fish passage on it; the fish passage includes an upstream fish passage section and a downstream fish passage section, the downstream fish passage section having at least two fish passage inlets at different elevations, each of which can be opened and closed independently; and a water replenishment system for providing fish-attracting water flow to the at least two fish passage inlets at different elevations.

[0007] Furthermore, the fishway section downstream of the dam is a multi-layered spiral or rotary fishway, and the at least two fishway inlets are respectively located on fishway sections at different elevations.

[0008] Furthermore, the fishway section below the dam includes a fixed top-level fishway and a movable fishway section that can be raised and lowered, with a fishway inlet at the end of the movable fishway section.

[0009] Furthermore, the water replenishment system includes a water replenishment inlet located upstream of the dam and a water replenishment outlet located adjacent to the fishway inlet, as well as a water replenishment landslide extending downstream along the dam or bank slope; the water replenishment outlet is intersecting with the fishway section downstream of the dam, and a water replenishment flip plate is installed on the intersecting section.

[0010] Furthermore, the top-level fishway and the fishway moving section are connected by an elevator, which is used to transfer fish from the fishway moving section to the top-level fishway.

[0011] Furthermore, the elevator includes a lifting shaft, a fish collection and transfer box, a lifting assembly, and a gate lifting assembly; the lifting shaft is a vertically arranged well-shaped structure with a guide rail inside, and the fish collection and transfer box is slidably mounted on the guide rail for temporarily accommodating and transferring fish; the side wall of the fish collection and transfer box is provided with a fish inlet and a fish outlet; the fish inlet faces the fishway moving section and is used to receive fish swimming in from the fishway moving section; the fish outlet faces the top fishway and is used to release fish to the top fishway.

[0012] Furthermore, the fishway moving section is driven to rise and fall by a lifting rod.

[0013] Furthermore, a water supply pipe is installed on the fish inlet connecting the top-level fish passage to the elevator.

[0014] Furthermore, an energy dissipation box is also installed between the water replenishment landslide and the water replenishment outlet.

[0015] Furthermore, the energy dissipation box is box-shaped, with energy dissipation inlets and outlets on opposite sides, and several energy dissipation plates are arranged alternately inside the energy dissipation box.

[0016] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: (1) A comprehensive fish passage system adapted to large water level fluctuations downstream of the dam was constructed. For water conservancy and hydropower projects with large water level fluctuations downstream of the dam, two fish passage modes were set up: multi-level fish passage sections downstream of the dam with different working conditions and fish passage mode with fish passage section + elevator coordinated with different working conditions. Among them, the multi-level fish passage section downstream of the dam can control the opening and closing of the inlet gates of different levels of fish passages in real time according to the water level changes, which is flexible and highly adaptable. The fish passage mode with fish passage section + elevator coordinated with different working conditions sets the top fish passage as a fixed section, and adds a fish passage moving section to cooperate with elevator and lifting rod to achieve smooth fish passage under different water level operating conditions. This not only provides a variety of selectable operating modes for the fish passage system, but also further improves the efficiency and convenience of the fish passage system through the setting of fixed sections, providing a new design idea for the fish passage system with large water level fluctuations downstream of the dam in the context of cascade development of the basin.

[0017] (2) An innovative layered fishway system and its ancillary facilities were developed. The two embodiments of the integrated fish passage system provided by this patent are based on the principle of providing fish passage channels with fish passage facilities and providing suitable hydrodynamic conditions for fish with water replenishment systems. In embodiment 2 (multi-layered fishway section below the dam), the water replenishment system and the fish passage channel are switched at different levels to adapt to water level changes. When the water level fluctuation is too large, embodiment 3 (fishway section below the dam + elevator) changes the height of the fishway moving section by lifting rods to connect with the fish inlet of the elevator. The fish collection box is transferred through the lifting component and the gate lifting component and connected to the top fishway section to realize fish passage. Fish can also be passed directly through the top fishway section at high water levels. This solves the problem of increasing operational complexity caused by setting up multiple inlets in traditional fish passage facilities to adapt to large water level fluctuations. It perfectly combines the autonomous upstream function of the fishway with the auxiliary upstream function of the fish lifter, further improving the fish passage efficiency of the fish passage system.

[0018] (3) A flexible and multifunctional water replenishment flip-over plate was created. The fishway sidewalls of each layer in Example 2 are connected in series with the water replenishment system, and the fishway sidewalls achieve a dual function: when fish are passing normally, the sidewalls are closed to form a fishway; when replenishing water to attract fish, the sidewalls are opened to both sides with the central axis as the center line to form a water replenishment channel (i.e., the water replenishment flip-over plate), and at the same time, the fishway of that layer is isolated and switched to a spiral rising fishway that is more adaptable to the operating water level (e.g., when switching from a medium water level condition to a high water level condition, the bottom fishway is isolated by opening the water replenishment flip-over plate, shortening the length of the fishway and reducing the migration distance of the fish). This design cleverly connects the fishway and the water replenishment channel to form a flexible and adjustable fish passage system, further improving the operating efficiency of the fish passage system. Attached Figure Description

[0019] Figure 1 This is the overall structural layout diagram of this patent (Example 1, Example 2); Figure 2 This is the overall structural layout diagram of this patent (Example 3); Figure 3 This is the overall structural diagram of the downstream fishway section (the water replenishment flip-over plate of the bottom and middle fishway sections in Example 2 is opened). Figure 4 This is the overall structural diagram of the downstream fishway section (the water replenishment flip-over plate of the bottom and top fishway sections in Example 2 is opened). Figure 5 This is a diagram of the overall structure of the downstream fishway section (Example 3). Figure 6 This is the overall structural diagram of the downstream fishway section (fish passage conditions in the middle or top layer of the fishway section in Example 3). Figure 7 This is the overall structural diagram of the downstream fishway section (Example 3: Fish passage conditions in the bottom or top fishway section). Figure 8 This is a cross-sectional view of the elevator; Figure 9 This is a cross-sectional view of the lifting components of the elevator; Figure 10 This is a cross-sectional view of the lifting assembly of the elevator gate; Figure 11 This is a cross-sectional view of the elevator and a partial diagram of the fishway structure; Figure 12 This is a structural diagram of the elevator and a section of the fishway; Figure 13 This is a partial structural diagram of the water replenishment system; Figure 14 This is a structural diagram of an energy dissipation box.

[0020] Explanation of reference numerals in the attached diagram: 1—Dam; 2—Fishway; 201—Fishway section above the dam; 202—Fishway section below the dam; 2021—Bottom-level fishway; 2022—Middle-level fishway; 2023—Top-level fishway; 2024—Fishway moving section; 203—Fishway inlet; 204—Fishway outlet; 205—Fishway sidewall; 206—Fishway partition; 207—Inlet gate; 208—Inlet gate motor; 209—Top-level fishway section gate; 3—Water replenishment system; 301—Water replenishment outlet; 302—Water replenishment inlet; 303—Flow valve; 304—Water replenishment slope; 305—Water replenishment tilting plate one; 306—Tilting plate motor; 307—Energy dissipation box; 3071—Energy dissipation inlet; 3072—Energy dissipation plate; 3073—Energy dissipation outlet; 308—Water replenishment pipe; 309—Water replenishment tilting plate two ; 4—Elevator; 401—Lifting assembly; 4011—Motor 1; 4012—Rotating shaft; 4013—Steel cable; 402—Guide rail 1; 403—Lifting shaft; 404—Fish collection and transfer box; 405—Fish inlet; 406—Fish outlet; 407—Gate lifting assembly; 4071—Lifting motor; 4072—Screw rod; 4073—Connecting block; 408—Guide rail 2; 5—Support column; 6—Lifting rod. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0022] It should be noted that the terms "vertical," "horizontal," "up," "down," "left," "right," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] Example 1. As... Figure 1 As shown, this embodiment provides a fish passage system adapted to large water level fluctuations downstream of a dam. The system includes a dam 1, a fish passage 2, and a water replenishment system 3.

[0025] Dam 1 is the main body of the water conservancy project, forming a high-water reservoir upstream. The water level downstream of the dam fluctuates due to the influence of downstream cascade operation and natural flow. Fishway 2 is located on one side of dam 1 (e.g., the left or right bank) to connect the upstream and downstream of dam 1, providing a passage for fish to migrate upstream. Fishway 2 includes an upstream fishway section 201 and a downstream fishway section 202. The starting end of the upstream fishway section 201 connects to the upstream of dam 1, and its ending end connects to the downstream fishway section 202. The downstream fishway section 202 extends downstream along the downstream face or bank slope of dam 1, with its ending end extending into the downstream water. At least two fishway inlets 203 at different elevations are provided along the extension direction of the downstream fishway section 202. Each of the fishway inlets 203 is equipped with an independently openable and closed gate to control the opening or closing of the inlet. When the fishway inlet 203 has a sufficiently suitable working water depth, the fishway inlet 203 is opened to form an entrance for fish to enter the fishway 2.

[0026] The water replenishment system 3 is used to provide fish-attracting water flow to the at least two fishway inlets 203 at different elevations. Specifically, the water replenishment system 3 includes a water replenishment inlet 302 located upstream of the dam 1 and a water replenishment outlet 301 located adjacent to the fishway inlet 203, as well as a water replenishment slope 304 extending downstream along the dam 1 or the bank slope. The water replenishment system 3 draws water from upstream of the dam 1 and guides the water flow to each fishway inlet 203 of the fishway section 202 downstream of the dam. At each fishway inlet 203, a water replenishment outlet 301 is provided to release water flow into the inlet area.

[0027] The working principle of this embodiment is as follows: When the water level downstream of the dam changes, the operator selects an inlet from at least two fishway inlets 203 at different elevations that matches the current water level and opens the gate corresponding to that inlet. Simultaneously, the water replenishment system 3 is activated to provide fish-attracting water flow to the opened fishway inlet 203. Guided by this fish-attracting water flow, fish enter the fishway 2 from the fishway inlet 203 and swim upstream along the fishway 2 to the upstream of the dam 1.

[0028] With the above structure, this embodiment ensures that a fish passage inlet 203 is always at the optimal submersion depth under different water level conditions, thereby solving the problem of fish passage inlet failure caused by large water level changes in the prior art.

[0029] Example 2. This example is a preferred structural form of the fish passage system adapted to large water level fluctuations downstream of the dam, as described in Example 1. For example... Figure 1 , Figure 3 and Figure 4As shown, in this embodiment, the fishway section 202 downstream of the dam is a multi-layered spiral or rotary fishway. Specifically, taking a three-layer structure as an example, the fishway section 202 downstream of the dam includes a bottom fishway 2021, a middle fishway 2022, and a top fishway 2023 arranged sequentially along the elevation direction. The bottom fishway 2021, the middle fishway 2022, and the top fishway 2023 are connected sequentially by a spiral or rotary structure to form a continuous upstream channel. Each of the bottom fishway 2021, the middle fishway 2022, and the top fishway 2023 is provided with a fishway inlet 203, which is used to adapt to low water level, medium water level, and high water level conditions, respectively. Each fishway inlet 203 is provided with an independently openable and closable inlet gate 207, which is used to control the opening or closing of the inlet. A water supply outlet 301 is provided adjacent to the fishway inlet 203. The inlet gate 207 is driven to open and close by a corresponding inlet gate motor 208.

[0030] like Figure 3 , Figure 4 , Figure 13 and Figure 14 As shown, the water replenishment system 3 includes a water replenishment outlet 301, a water replenishment inlet 302, a flow valve 303, a water replenishment ramp 304, an energy dissipation tank 307, and a water replenishment tilting plate 305. The water replenishment inlet 302 is located upstream of the dam 1 and is used to draw water from the upstream reservoir area. Water flows through the water replenishment inlet 302 into the water replenishment system 3, flows downstream along the water replenishment ramp 304 into the energy dissipation tank 307, and replenishes the adjacent fishway inlet 203 after the flow rate is regulated by the flow valve 303. Figure 13 As shown, a water replenishment flip plate 2 309 that can be flipped is provided at the connection between the energy dissipation box 307 and the water replenishment slope 304. By setting the water replenishment flip plate 2 309, when the water level down the dam changes, the water replenishment flip plates 2 309 corresponding to the bottom fish passage 2021, the middle fish passage 2022 and the top fish passage 2023 are opened to provide water replenishment flow to the fish passage inlet 203 that needs water replenishment.

[0031] The energy dissipation box 307 is box-shaped, with an energy dissipation inlet 3071 and an energy dissipation outlet 3073 on opposite sides. Several energy dissipation plates 3072 are arranged alternately inside the energy dissipation box 307. After the water flows into the energy dissipation box 307 from the energy dissipation inlet 3071, it flows through the alternately arranged energy dissipation plates 3072, where excess energy is consumed through collision and turbulence. The water then flows out from the energy dissipation outlet 3073 after the flow rate is regulated by the flow valve 303. The section where the water supply outlet 301 intersects with the fishway section 202 downstream of the dam is constructed using a water supply flip plate 305 as a sidewall. The water supply flip plate 305 is driven to flip by a flip plate motor 306. When the water supply flip plate 305 is in the closed state, it serves as part of the fishway sidewall, blocking the water supply flow. When the water supply flip plate 305 is flipped open, the water supply outlet 301 provides fish-attracting water flow to the adjacent fishway inlet 203, while simultaneously blocking the corresponding level of the fishway chamber. This allows the fish to enter the fishway level by level along the corresponding level of the fishway inlet 203 and ascend gradually (without entering the fishway chamber space below that level), shortening the ascending distance of the fish and preventing them from wandering in the long fishway chamber.

[0032] The working process of this embodiment is as follows: When the water level downstream of the dam is in the low water level range, the operator opens the inlet gate 207 corresponding to the fishway inlet 203 at the end of the bottom fishway 2021, and simultaneously opens the water replenishment flip plate 1 305 and water replenishment flip plate 2 309 corresponding to the fishway inlet 203, and closes the inlet gate 207 and the corresponding water replenishment flip plate 305 of the middle fishway 2022 and the top fishway 2023; at this time, the water flow of the water replenishment system 3 is dissipated by the energy dissipation box 307, and enters the bottom fishway 2021 through the opened water replenishment flip plate 1 305 and water replenishment flip plate 2 309, forming a fish-attracting water flow at the fishway inlet 203 of the bottom fishway 2021; under the guidance of the fish-attracting water flow, the fish enter the fishway 2 from the fishway inlet 203 of the bottom fishway 2021, and go upstream along the bottom fishway 2021, the turning section, the middle fishway 2022, and the top fishway 2023 to the upstream of the dam 1. When the water level downstream of the dam rises to the middle water level range, the inlet gates 207 of the bottom fishway 2021 and the top fishway 2023, along with their corresponding water replenishment flaps 305, are closed, while the inlet gate 207 of the middle fishway 2022 and its corresponding water replenishment flaps 305 are opened. At this time, fish enter from the fishway inlet 203 of the middle fishway 2022 and swim upstream along the middle fishway 2022, the turning section, and the top fishway 2023. When the water level downstream of the dam rises to the high water level range, the inlet gates 207 of the middle fishway 2022 and the bottom fishway 2021, along with their corresponding water replenishment flaps 305, are closed, while the inlet gate 207 of the top fishway 2023 and its corresponding water replenishment flaps 305 are opened. At this time, fish directly enter from the fishway inlet 203 of the top fishway 2023 and swim upstream along the top fishway 2023.

[0033] Through the above structure, this embodiment designs the fishway section 202 downstream of the dam as a multi-layered spiral or rotary fishway, with independent fishway inlets 203 and corresponding water replenishment and tilting plates 305 set in different layers. This enables precise and flexible control of the fish passage path and fish-attracting water flow under different water level conditions. At the same time, the spiral or rotary structure makes full use of vertical space and significantly reduces the horizontal footprint.

[0034] Example 3. This example is another preferred structural form of the fish passage system adapted to large water level fluctuations downstream of the dam, as described in Example 1. For example... Figure 2 , Figures 5 to 12 As shown, in this embodiment, the fishway section 202 downstream of the dam includes a fixed top fishway 2023 and a movable fishway section 2024. The top fishway 2023 is fixedly installed on the downstream face or bank slope of the dam 1, and its inlet elevation corresponds to the highest operating water level downstream. The movable fishway section 2024 is movably installed below the top fishway 2023, and its end constitutes one of the fishway inlets 203. The movable fishway section 2024 is driven to rise and fall by a lifting rod 6. The lifting rod 6 is preferably a hydraulic cylinder or an electric push rod, with its fixed end installed on the foundation of the dam 1 or bank slope, and its movable end hinged to the bottom or side of the movable fishway section 2024, used to drive the movable fishway section 2024 to rise and fall vertically along the guide rail 408. The guide rail 408 is set vertically on the lifting shaft 403 to guide the rising and falling movement of the movable fishway section 2024 and ensure its smooth operation.

[0035] like Figures 8 to 12 As shown, the system also includes an elevator 4 for transferring fish from the fishway movement section 2024 to the top fishway 2023. The elevator 4 includes a lifting shaft 403, a fish collection and transfer box 404, a lifting assembly 401, and a gate lifting assembly 407. The lifting shaft 403 is a vertically arranged well-shaped structure with a guide rail 402 inside. The fish collection and transfer box 404 is slidably mounted on the guide rail 402 for temporarily accommodating and transferring fish. The side wall of the fish collection and transfer box 404 has a fish inlet 405 and a fish outlet 406. The fish inlet 405 faces the fishway movement section 2024 and is used to receive fish swimming in from the fishway movement section 2024; the fish outlet 406 faces the top fishway 2023 and is used to release fish into the top fishway 2023. Both the fish inlet 405 and the fish outlet 406 are equipped with independently openable and closable gates to control the entry and exit of fish.

[0036] The lifting assembly 401 is used to drive the fish collection box 404 to move up and down within the lifting shaft 403. Specifically, as shown... Figure 9 As shown, the lifting assembly 401 includes a motor 14011, a rotating shaft 4012, and a steel cable 4013. The motor 14011 is mounted on the top of the lifting shaft 403, and its output shaft is connected to the rotating shaft 4012 for transmission. One end of the steel cable 4013 is fixed and wound around the rotating shaft 4012, and the other end is fixedly connected to the fish collection box 404. When the motor 14011 drives the rotating shaft 4012 to rotate, the steel cable 4013 is wound up and down, thereby driving the fish collection box 404 to rise and fall along the guide rail 402.

[0037] The gate lifting assembly 407 is used to control the opening and closing of the gates at the fish inlet 405 and the fish outlet 406. Specifically, as shown... Figure 10 As shown, the gate lifting assembly 407 includes a lifting motor 4071, a lead screw 4072, and a connecting block 4073. The lifting motor 4071 is mounted on the top of the fish collection box 404, and its output shaft is connected to the lead screw 4072 for transmission. The connecting block 4073 is threadedly engaged with the lead screw 4072 and is fixedly connected to the gate at the fish inlet 405 or fish outlet 406. When the lifting motor 4071 drives the lead screw 4072 to rotate, the connecting block 4073 drives the gate to move vertically, thereby opening or closing the gate.

[0038] A water supply pipe 308 is installed on the fish outlet 406 connecting the top fishway 2023 and the elevator 4; a water supply pipe 308 is also installed on the fish inlet 405 connecting the elevator 4 and the fishway moving section 2024. Preferably, a regulating valve is installed on the water supply pipe 308 to regulate the water supply flow. The water supply pipe 308 guides the water flow to the fish outlet 406 and the fish inlet 405, forming an attractive water flow that guides fish from the fishway moving section 2024 into the fish collection and transfer box 404 and from the fish collection and transfer box 404 into the top fishway 2023.

[0039] The working process of this embodiment is as follows: When the water level downstream of the dam is in the low or medium water level range, the fishway moving section 2024 is driven to descend by the lifting rod 6, so that the fishway inlet 203 at its end is submerged below the current water surface and meets a sufficiently suitable working water depth; at this time, the inlet gate 207 corresponding to the fishway inlet 203 at the end of the fishway moving section 2024 is opened, and the fish inlet gate 405 of the elevator 4 is opened. At the same time, a fish-attracting water flow is provided to the fish inlet 405 of the elevator 4 through the water supply pipe 308. Under the guidance of the fish-attracting water flow, the fish enter the fishway moving section 2024 from the fishway inlet 203, and then swim into the fish collection and transfer box 404. When a certain number of fish have gathered in the fish collection and transfer box 404, the fish inlet gate 405 is closed, and the lifting component 401 is activated to raise the fish collection and transfer box 404 to the elevation of the top fishway 2023. Subsequently, the fish outlet gate 406 is opened, and the fish swim out of the fish collection and transfer box 404, enter the top fish passage 2023, and swim upstream along the top fish passage 2023 to the upstream of dam 1. When the water level downstream of the dam rises to the high water level range, the inlet gate 207 of the top fish passage 2023 is opened directly, the top fish passage section gate 209 is closed, and the elevator 4 system is shut down. The fish then directly enter from the inlet of the top fish passage 2023 and swim upstream.

[0040] Through the above structure, this embodiment achieves proactive and precise adaptation to extreme water level fluctuations by cooperating with the liftable fishway section 2024 and the elevator 4. When the water level is low, the fishway section 2024 can be lowered to the water surface, and fish can be safely and efficiently transferred to the top fishway 2023 at a fixed elevation via the elevator 4, avoiding excessive energy consumption by fish due to long-distance upstream migration.

[0041] This embodiment provides a fish passage method based on the fish passage system adapted to large water level fluctuations downstream of the dam described in Embodiment 3; the method includes the following steps: Step S1: Based on the change in water level downstream of the dam, select and open one fishway inlet 203 corresponding to the current water level from at least two fishway inlets 203 at different elevations. Specifically, when the water level downstream of the dam is in the first elevation range, open the first fishway inlet 203 located in that range; when the water level downstream of the dam changes to the second elevation range, close the first fishway inlet 203 and open the second fishway inlet 203 located in the second elevation range. The opening and closing of the fishway inlet 203 is achieved by operating the corresponding inlet gate 207.

[0042] Step S2 involves using the water replenishment system 3 to provide a fish-attracting water flow to the opened fishway inlet 203. Specifically, in step S1, while opening a fishway inlet 203, the water replenishment system 3 is activated, releasing water into the area of ​​that opened fishway inlet 203. This fish-attracting water flow forms a directional flow with a higher velocity than the surrounding water at the fishway inlet 203, creating a velocity difference that guides fish to discover and enter the fishway 2. When a change in water level causes the fishway inlet 203 to switch, the water supply path of the water replenishment system 3 is simultaneously switched, ensuring that it only supplies water to the currently opened fishway inlet 203.

[0043] In step S3, when water level changes cause the fishway inlet 203 to switch, the fish are transferred from the fishway moving section 2024 to the top fishway 2023 via the elevator 4. Specifically, when the water level downstream of the dam drops below the inlet elevation of the top fishway 2023, the fishway moving section 2024 descends to a suitable working depth, and the fish enter from the fishway inlet 203 at the end of the moving section 2024. Subsequently, the fish are lifted to the elevation of the top fishway 2023 via the elevator 4 and continue to swim upstream in the top fishway 2023. When the water level downstream of the dam rises back above the inlet elevation of the top fishway 2023, the fish can directly pass through the inlet of the top fishway 2023, at which point the elevator 4 stops operating.

[0044] Comparative Example 1. This comparative example provides a conventional fish passage system as a benchmark for comparison with the embodiments of the present invention. This conventional system includes a dam and a fishway. The fishway is a straight or meandering fishway with a fixed elevation, and a fishway inlet with a fixed elevation is provided at its downstream end. The bottom elevation of the fishway inlet is fixed and cannot be adjusted according to changes in the water level downstream of the dam. The system also includes a diversion and replenishment system along the passage, which is arranged along the sidewall of the fishway, and its outlet is located near the fishway inlet to continuously create a fish-attracting water flow at the inlet.

[0045] The traditional system operates as follows: regardless of changes in the downstream water level, fish can only enter the fishway through this single, fixed-elevation fishway inlet. The water replenishment system continuously operates, providing an attractive flow of water to the fishway inlet.

[0046] This traditional system suffers from the following significant technical defects: 1. Inability to adapt to large water level fluctuations: When the water level downstream of the dam drops significantly, the fishway inlet at a fixed elevation may be completely exposed above the water surface or submerged to a shallow depth, preventing fish from entering. When the water level downstream of the dam rises significantly, the fishway inlet may be over-submerged, resulting in excessively low flow velocity at the inlet, significantly weakening or even eliminating the fish-attracting effect.

[0047] 2. Low fish passage efficiency: Due to its inability to actively adapt to water level changes, the system can only effectively pass fish when the water level downstream of the dam is exactly within the optimal submergence depth range of the fishway inlet. Under other water level conditions, the fish passage efficiency is extremely low, or even completely ineffective.

[0048] 3. Inflexible regulation: The system lacks the ability to make precise structural adjustments based on water level changes, and cannot provide a stable and efficient passage for fish under different water level conditions.

[0049] By comparing with embodiments 1 to 4 of the present invention, it can be clearly seen that the present invention, by setting "at least two fishway inlets 203 at different elevations" or "liftable fishway movable sections 2024", and matching them with corresponding water replenishment systems 3 and transfer devices (such as elevators 4), achieves proactive and precise adaptation to changes in the water level downstream of the dam. The present invention solves the technical problem in the comparative examples where the fixed elevation inlets cannot adapt to large water level fluctuations, significantly improving the environmental adaptability and operational reliability of the fish passage system, thus highlighting the inventiveness of the present invention.

[0050] Obviously, the above description is only a part of the embodiments of the present invention, and not all of the embodiments. The above embodiments are not intended to limit the present invention, and various modifications and variations can be made to the present invention by those skilled in the art. Any combination, modification, equivalent substitution, improvement, and all other embodiments that can be made by those skilled in the art within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. A fish passage system adapted to large water level fluctuations downstream of a dam, comprising a dam (1), characterized in that: A fishway (2) is provided on the dam (1); the fishway (2) includes a fishway section (201) above the dam and a fishway section (202) below the dam, the fishway section (202) below the dam is provided with at least two fishway inlets (203) at different elevations, each fishway inlet (203) can be opened and closed independently; and a water supply system (3) is provided to provide fish-attracting water flow to the fishway inlets (203).

2. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 1, characterized in that: The fishway section (202) below the dam is a multi-layered spiral or rotary fishway, and the at least two fishway inlets (203) are respectively set on fishway sections at different elevations.

3. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 1, characterized in that, The fishway section (202) below the dam includes a fixed top fishway (2023) and a movable fishway section (2024) that can be raised and lowered. The fishway inlet (203) is provided at the end of the movable fishway section (2024).

4. The fish passage system adapted to large water level fluctuations downstream of the dam according to claim 1 or 2, characterized in that, The water replenishment system (3) includes a water replenishment inlet (302) located upstream of the dam (1) and a water replenishment outlet (301) located adjacent to the fishway inlet (203), as well as a water replenishment landslide (304) extending downstream along the dam (1) or the bank slope; the water replenishment outlet (301) is intersecting with the fishway section (202) downstream of the dam, and a water replenishment flip plate (305) is provided on the intersecting section.

5. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 3, characterized in that, The top fishway (2023) and the fishway moving section (2024) are connected by an elevator (4) for transferring fish from the fishway moving section (2024) to the top fishway (2023).

6. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 5, characterized in that, The elevator (4) includes a lifting shaft (403), a fish collection and transfer box (404), a lifting assembly (401), and a gate lifting assembly (407); the lifting shaft (403) is a vertically arranged well-shaped structure with a guide rail (402) inside, and the fish collection and transfer box (404) is slidably arranged on the guide rail (402); the side wall of the fish collection and transfer box (404) is provided with a fish inlet (405) and a fish outlet (406); the fish inlet (405) faces the fish passage moving section (2024) and is used to receive fish swimming in from the fish passage moving section (2024); the fish outlet (406) faces the top fish passage (2023) and is used to release fish to the top fish passage (2023).

7. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 3, characterized in that, The fishway moving section (2024) is driven to rise and fall by a lifting rod (6).

8. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 3, characterized in that, A water supply pipe (308) is installed on the fish inlet (405) connecting the top fish passage (2023) and the elevator (4).

9. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 4, characterized in that, An energy dissipation box (307) is also installed between the water replenishment landslide (304) and the water replenishment outlet (301).

10. The fish passage system adaptable to large water level fluctuations downstream of the dam according to claim 9, characterized in that, The energy dissipation box (307) is box-shaped, with an energy dissipation inlet (3071) and an energy dissipation outlet (3073) on opposite sides, and several energy dissipation plates (3072) are arranged alternately inside the energy dissipation box (307).

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