A small river barrage construction fish migration device

Abstract

The present application relates to the field of water conservancy and ecological restoration technology, and particularly relates to a small river blocking construction fish migration device, which comprises a culvert, a dredging pipeline one and a plurality of dredging pipelines two, the culvert is provided with a fish passing area, a plurality of bottom sills are arranged in the fish passing area, slopes and slow flow sections are formed between the plurality of bottom sills, a plurality of sand accumulation grooves are arranged on the inner wall of the slow flow sections, the top end of the sand accumulation groove is covered with a baffle, the dredging pipeline one and the dredging pipeline two are connected with the sand accumulation groove, and the dredging pipeline one and the dredging pipeline two are both arranged obliquely. Through the arrangement of the sand accumulation groove, the block valve, the dredging pipeline one and the dredging pipeline two, the fish is blocked by the baffle, the amount of silt accumulation in the fish passing area is reduced, and the influence on the fish is reduced; through the cooperation of the dredging pipeline one and the dredging pipeline two, the silt in the sand accumulation groove is regularly cleaned by the action of the water flow, the culvert does not need to be closed, the fishway operation is not interrupted, the influence of the fish migration period is small, and the working efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering and ecological restoration technology, specifically to a small-scale river dam structure fish migration device. Background Technology

[0002] Fish migration is the periodic, directional, back-and-forth movement of fish caused by physiological needs, genetics, and environmental factors. In recent years, measures to address fish migration have been continuously proposed. Small rivers often pass through villages and towns, and local villagers often construct small dams to retain agricultural water, leading to prolonged periods of river flow interruption downstream. Existing fishway technologies (such as vertical slotted and weir-type fishways) are mostly suitable for large and medium-sized water conservancy projects. For the numerous small river dams, fishways are typically constructed using culverts.

[0003] However, it has the following shortcomings: Existing fishways typically include a sloping surface that fits into the riverbed and a horizontally set slow-flow section. When fish migrate upstream, they pass through the sloping surface and rest in the slower-flowing section. However, due to the low water velocity in the slow-flowing section, sediment easily accumulates there, covering the gravelly bottom and damaging the spawning grounds of benthic fish (such as carp and crucian carp). It also reduces water transparency, inhibits phytoplankton photosynthesis, and affects fish survival. Traditional methods of clearing sediment deposits usually require closing the culvert, interrupting fishway operation, and using manual excavation. This results in high maintenance costs per operation and is greatly affected by the fish migration cycle, leading to labor-intensive and inefficient work. Summary of the Invention

[0004] The technical solution adopted by this invention to solve its technical problem is: to provide a small-scale river dam structure fish migration device, comprising:

[0005] The culvert is located on a dam and has an inlet and an outlet. The inlet is at a lower height than the outlet. Water flows from the outlet to the inlet. A fish passage area is provided between the inlet and the outlet. The fish passage area has multiple bottom sills arranged side by side along the direction of water flow. Each bottom sill has a fish passage opening. The multiple bottom sills form an alternating slope and a slow-flow section. The bottom surface of the slope is inclined, and the bottom surface of the slow-flow section is horizontal. The inlet has a fish-attracting structure.

[0006] The inner wall of the slow-flow section is provided with multiple sand accumulation grooves. The flow direction of the water in the sand accumulation grooves and the flow direction of the water in the slow-flow section intersect each other. The top of the sand accumulation grooves is covered with a baffle plate, and the baffle plate is provided with through holes for sediment to fall into.

[0007] It also includes multiple dredging pipes (first and second) buried within the dam. The dam is equipped with a sealing gate, which is used to control the connection between the dredging pipes (first) and the external water flow. The dredging pipes (first) are connected to the inlet of the sand accumulation groove, and the dredging pipes (second) are connected to the outlet of the sand accumulation groove. Both the dredging pipes (first and second) are inclined. The bottom of the dredging pipes (first) is connected to the sand accumulation groove, and the top of the dredging pipes (second) extends out of the dam and connects to the river. The top of the dredging pipes (second) is connected to the sand accumulation groove, and the bottom of the dredging pipes (second) extends out of the dam.

[0008] Furthermore, the baffle is provided with a blocking protrusion, and the baffle has two sets of through holes. The two sets of through holes are arranged side by side along the width direction of the sand accumulation groove, and the diameter of the through hole near the outlet end is larger than the diameter of the through hole away from the outlet end. The two sets of through holes are located at the two ends of the blocking protrusion.

[0009] Furthermore, a pressure stabilizing cavity is provided between the dredging pipe and the sand accumulation groove. The pressure stabilizing cavity includes an arc segment and a gradually expanding segment. The arc segment is located between the dredging pipe and the gradually expanding segment. The gradually expanding segment has a trumpet-shaped structure. The end of the gradually expanding segment with a larger opening is connected to the sand accumulation groove, and the end of the gradually expanding segment with a smaller opening is connected to the arc segment.

[0010] Furthermore, the sand accumulation groove is provided with multiple guide vanes, and the guide vanes are provided with sand accumulation holes corresponding to the through holes. The guide vanes include an arc-shaped section and a guide section. The arc-shaped section is located at the connection between the dredging pipe and the sand accumulation groove. The guide section is inclined and forms a flushing groove between the guide section and the bottom wall of the sand accumulation groove. The depth of the flushing groove near the dredging pipe is greater than the depth of the flushing groove away from the dredging pipe.

[0011] Furthermore, the diameter of the sand accumulation hole is larger than the diameter of the through hole.

[0012] Furthermore, the top of the blocking protrusion has an arc-shaped structure.

[0013] Furthermore, an energy dissipation pool is provided at the outlet, and a buffer pool is provided between the fish passage area and the inlet. The surfaces of the fish passage area, the buffer pool, and the energy dissipation pool are all covered with energy dissipation stones.

[0014] Furthermore, it also includes a vegetation restoration area set up around the culvert, which contains aquatic plants and wetland plants.

[0015] Furthermore, a guide wall is provided at the outlet. The guide wall has a funnel-shaped structure, and the end of the guide wall closer to the inlet is closer to the central axis of the guide wall than the end of the guide wall farther from the inlet.

[0016] Furthermore, a regulating gate is provided at the outlet, which is used to regulate the flow rate of water entering the culvert.

[0017] The beneficial effects of this invention are as follows: By setting up the sand accumulation groove, the sealing valve, and the first and second dredging pipes, when the water flows through the slow-flow section, it falls into the sand accumulation groove through the through hole. Due to gravity, some of the silt in the water is deposited in the sand accumulation groove. At the same time, the baffle blocks the fish, preventing them from entering the sand accumulation groove and reducing the impact of silt accumulation on the fish. When clearing sand, the sealing gate is opened, allowing the water to enter the sand accumulation groove through the first dredging pipe due to the height difference. The deposited silt is then carried by the water flow through the second dredging pipe into the water flow outside the dam. This reduces the amount of silt accumulation in the slow-flow section and, through the cooperation of the first and second dredging pipes, allows for the regular clearing of silt in the sand accumulation groove by the action of the water flow. It does not require closing the culvert or interrupting the fishway operation, is less affected by the fish migration cycle, and has high working efficiency. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] In the picture: Figure 1 This is a schematic diagram showing the relative positions of the dam and the water flow described in this invention;

[0020] Figure 2 This is a front view of the culvert and dam described in this invention;

[0021] Figure 3 A top view of a small river dam structure fish migration device provided by the present invention;

[0022] Figure 4 for Figure 3 Sectional view along axis AA;

[0023] Figure 5 for Figure 4 A cross-sectional view below a side view of a portion of the structure shown;

[0024] Figure 6 for Figure 4 A sectional view below the front view of the partial structure shown in the image;

[0025] Figure 7 for Figure 3 Top view of the structure shown;

[0026] Figure 8 for Figure 7 The diagram shows the location of the dredging pipeline, the dam, and the sealing gate.

[0027] Attached diagram labels: 100, culvert; 10, entrance; 11, fish passage area; 12, bottom sill; 121, fish passage gap; 13, slope; 14, slow-flow section; 141, sand accumulation groove; 142, baffle; 1421, through hole; 1422, blocking protrusion; 143, guide vane; 1431, sand accumulation hole; 1432, arc section; 1433, guide section; 1434, scour channel; 15, buffer pool; 16, fish guide weir; 21, guide wall; 22, regulating gate; 23, stilling basin; 31, turbulence column; 41, dredging pipe one; 42, dredging pipe two; 43, arc section; 44, gradually widening section; 45, sealing gate; 50, vegetation restoration area; 20, outlet; 200, dam. Detailed Implementation

[0028] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will now be described in detail with reference to the accompanying drawings. This drawing is a simplified schematic diagram, illustrating only the basic aspects of the invention, and therefore only shows the components relevant to the invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] Please refer to Figure 1 , Figure 2 and Figure 3 This invention provides a small-scale river dam structure for fish migration, including a culvert 100, which is installed on a dam 200. The culvert 100 has an inlet 10 and an outlet 20. The height of the inlet 10 is lower than that of the outlet 20, and the water flows from the outlet 20 to the inlet 10. Specifically, in this embodiment, the axis of the culvert 100 should form a small angle (generally less than 30°) with the downstream mainstream direction of the river to facilitate fish finding the culvert entrance. The longitudinal slope of the culvert 100 (i.e., the ratio of the height difference between the inlet 10 and the outlet 20 to its horizontal distance) is controlled between 1:40 and 1:80 to ensure that the flow velocity inside the culvert is less than the overcurrent velocity of the target fish.

[0030] When the target fish species are mainly benthic, the longitudinal slope should be gentler, controlled between 1:50 and 1:100, to reduce the near-bottom flow velocity of culvert 100. Culvert 100 should have a rectangular box culvert or an arch culvert, with the cross-sectional dimensions determined based on the design flow rate and fish passage requirements. The height of culvert 100 should be no less than 10 times the body length of the target fish, and the minimum water depth should be no less than 0.3m; the width of culvert 100 should be no less than 5 times the body length of the target fish. The bottom slab of culvert 100 should be buried below the riverbed, and the top slab should be constructed as a simple bridge to meet structural safety requirements and daily traffic needs.

[0031] Please refer to Figure 3and Figure 4 A fish passage area 11 is provided between the inlet 10 and the outlet 20. Multiple sills 12 are provided within the fish passage area 11, arranged side-by-side along the water flow direction. Each sill 12 has a fish passage opening 121. Slopes 13 and slow-flow sections 14 are formed between the multiple sills 12. The bottom surface of the slopes 13 is inclined, and the bottom surface of the slow-flow sections 14 is horizontal. The inlet 10 has a fish-attracting structure. Specifically, in this embodiment, the sills 12 can be constructed using pine piles or masonry. The interval between adjacent sills 12 is 0.5m, and the sill height is 1 / 10 to 1 / 20 of the height of the culvert 100. This serves to dissipate energy in sections, create an alternating waterfall-deep pool hydraulic environment, and provide resting and sheltering areas for fish. The number and spacing of the sills 12 can be adjusted according to the water flow height difference between the two ends of the dam 200 in the width direction.

[0032] Specifically, in this embodiment, the fish-attracting structure includes multiple turbulence-inducing columns 31 arranged side-by-side at the inlet 10, with the columns 31 arranged in parallel along the width of the riverbed. Based on the Karman vortex street principle, the water flow through the turbulence-inducing columns 31 creates vortices at these columns, thus forming a fish-attracting flow.

[0033] Please refer to Figure 3 , Figure 4 and Figure 5 The inner wall of the slow-flow section 14 is provided with a plurality of sand accumulation grooves 141. The two ends of the sand accumulation grooves 141 are the water inlet and the water outlet, respectively. The flow direction of the water in the sand accumulation grooves 141 and the flow direction of the water in the slow-flow section 14 intersect each other. Furthermore, in this embodiment, the flow direction of the water in the sand accumulation grooves 141 and the flow direction of the water in the slow-flow section 14 are perpendicular to each other. The top of the sand accumulation grooves 141 is covered with a baffle 142. The baffle 142 is provided with a through hole 1421 for the mud and sand to fall into. The cross-sectional area of ​​the through hole 1421 is smaller than the area of ​​the fish, so that the fish are less likely to enter the sand accumulation grooves 141 when the mud and sand are introduced.

[0034] Please refer to Figure 7 The small river dam structure fish migration equipment also includes multiple dredging pipes 41 and 42 buried in the dam 200. The dam 200 is equipped with a blocking gate 45, which is used to control the connection between the dredging pipes 41 and the external water flow. The inlets of the dredging pipes 41 and the sand accumulation groove 141 are connected to each other. The outlets of the dredging pipes 42 and the sand accumulation groove 141 are connected. Both the dredging pipes 41 and 42 are inclined. The bottom of the dredging pipes 41 is connected to the sand accumulation groove 141. The top of the dredging pipes 41 extends out of the dam 200 and connects to the river. The top of the dredging pipes 42 is connected to the sand accumulation groove 141. The bottom of the dredging pipes 42 extends out of the dam 200.

[0035] With the installation of the sand accumulation groove 141, the sealing valve, the first dredging pipe 41, and the second dredging pipe 42, when the water flows through the slow-flow section 14, it falls into the sand accumulation groove 141 through the through hole 1421. Due to gravity, some of the silt in the water is deposited in the sand accumulation groove 141. At the same time, the baffle 142 blocks fish from entering the sand accumulation groove 141, reducing the impact of silt accumulation on fish. During sand removal, the sealing gate 45 is opened, allowing the water to flow at a height difference. The silt enters the sediment accumulation groove 141 through the first dredging pipe 41. Under the action of water flow, the accumulated silt enters the water flow outside the dam 200 through the second dredging pipe 42. While reducing the amount of silt accumulation in the slow-flow section 14, the silt in the sediment accumulation groove 141 can be cleaned regularly by the action of water flow through the cooperation of the first dredging pipe 41 and the second dredging pipe 42. It does not require closing the culvert 100 and interrupting the operation of the fishway. It is less affected by the fish migration cycle and has high work efficiency.

[0036] Please refer to Figure 5 The baffle 142 is provided with a blocking protrusion 1422. The baffle 142 has two sets of through holes 1421. The two sets of through holes 1421 are arranged side by side along the width direction of the sand accumulation groove 141 (from the side view angle, the width direction of the sand accumulation groove 141 is the same as the water flow direction). The diameter of the through hole 1421 near the outlet 20 is larger than the diameter of the through hole 1421 away from the outlet 20. The two sets of through holes 1421 are located at the two ends of the blocking protrusion 1422 respectively.

[0037] Due to the obstruction protrusion 1422, when water flows from outlet 20 into culvert 100, the flow velocity is reduced by the obstruction protrusion 1422. This makes it easier for sediment in the water to briefly linger at the larger aperture through-hole 1421 and accumulate in the sediment accumulation groove 141. Since the sediment in the water first passes through the larger aperture through-hole 1421, most of the sediment flows into the sediment accumulation groove 141 at the larger aperture through-hole 1421 for sedimentation. A small portion of the sediment, after flowing past the obstruction protrusion 1422, falls into the sediment accumulation groove 141 at the smaller aperture through-hole 1421 and accumulates there. The obstruction protrusion 1422 also has a certain energy dissipation effect on the water flow. By setting the blocking protrusion 1422, the flow velocity of the water is reduced under the premise of energy dissipation, so that the water flow stops at the through hole 1421, which makes it easier for silt to enter the sand accumulation groove 141 and accumulate, rather than accumulating on the surface of the slow flow section 14. The baffle 142 blocks the silt, thus separating the living area of ​​fish in the slow flow section 14 from the silt accumulation area and reducing the impact on fish.

[0038] Please refer to Figure 6 and Figure 7A pressure-stabilizing cavity is provided between the dredging pipe 41 and the sand accumulation groove 141. The pressure-stabilizing cavity includes an arc section 43 and a gradually expanding section 44. The arc section 43 is located between the dredging pipe 41 and the gradually expanding section 44. The gradually expanding section 44 has a trumpet-shaped structure. The end of the gradually expanding section 44 with a larger opening is connected to the sand accumulation groove 141, and the end of the gradually expanding section 44 with a smaller opening is connected to the arc section 43. Since the orientation of the external water flow and the sand accumulation groove 141 is perpendicular to each other, in order to connect the sand accumulation groove 141 with the outside, both the dredging pipe 41 and the dredging pipe 42 need to change direction. If the part of the dredging pipe 41 that is used to introduce water flow into the sand accumulation groove 141 is set as a right angle, due to the existence of boundary effect, the straight pipe changes the flow direction and disperses the fluid kinetic energy, reducing the flow velocity. When the water flow passes through the right angle bend, the direction changes abruptly, the flow velocity on the outside increases sharply, and the backflow zone is easily formed on the inside, resulting in strong turbulence and flow separation, and generating high energy dissipation. The water flow is prone to turbulence in the dredging pipe 41 before entering the sand accumulation groove 141, which in turn stirs up the silt in the sand accumulation groove 141. The silt can easily re-enter the fish passage area 11 through the through hole 1421, affecting the sand removal efficiency. Therefore, in this embodiment, an arc section 43 is set to reduce the formation of turbulence, so that the water flow velocity is reduced before entering the sand accumulation groove 141.

[0039] By setting the arc segment 43, the arc transition causes the water flow to gradually change direction, the flow velocity distribution is more gentle, the turbulence intensity and separation zone range are reduced, the flow velocity of the water is reduced, and the mud and sand in the sand accumulation groove 141 are less likely to be stirred and overflow the sand accumulation groove 141.

[0040] Simultaneously, the widening section 44 increases the cross-sectional area of ​​the water flow and reduces the flow velocity, making the water flow gentler before entering the sand accumulation groove 141, thus reducing the velocity difference between the water flows in the gentle flow section 14. This avoids excessive water velocity caused by the inclination of the dredging pipe 41, which would create a pressure difference between the inside and outside of the sand accumulation groove 141. If the internal pressure of the sand accumulation groove 141 is lower than the external pressure, the accumulated silt in the sand accumulation groove 141 would be sucked out, causing the external water flow to become turbid and affecting the sand removal efficiency.

[0041] Please refer to Figure 6 The sand accumulation groove 141 is provided with multiple guide vanes 143. The guide vanes 143 are provided with sand accumulation holes 1431 corresponding to the through holes 1421. The guide vanes 143 include an arc-shaped section 1432 and a guide section 1433. The arc-shaped section 1432 is located at the connection between the dredging pipe 41 and the sand accumulation groove 141. The guide section 1433 is inclined. A flushing groove 1434 is formed between the guide section 1433 and the bottom wall of the sand accumulation groove 141. The depth of the flushing groove 1434 near the dredging pipe 41 is greater than the depth of the flushing groove 1434 away from the dredging pipe 41.

[0042] With the guide plate 143 in place, the water flows into the sand accumulation groove 141 through the sludge removal pipe 41. The arc-shaped section 1432 gently guides the water flow to the bottom of the sand accumulation groove 141. The water then flows along the inclined guide section 1433. Under the gradual guidance of the guide section 1433, the flow cross-sectional area gradually decreases towards the bottom wall of the sand accumulation groove 141, and the silt is basically deposited in the lower part of the sand accumulation groove 141. With the guide plate 143 in place, the water flow gradually flows towards the silt when it enters the sand accumulation groove 141, which facilitates flushing the silt out of the sand accumulation groove 141 and concentrating the water flow at the silt accumulation area. This leaves space between the opening of the through hole 1421 and the water flow, so that when the silt is impacted, it is not easy for it to overflow from the sand accumulation groove 141 through the through hole 1421 and affect the fish in the fish passage area 11.

[0043] Furthermore, in order to prevent silt from accumulating in the gap between the through hole 1421 and the sand accumulation hole 1431 when it falls into the sand accumulation groove 141, the diameter of the sand accumulation hole 1431 is larger than the diameter of the through hole 1421.

[0044] To facilitate the water flow over the obstruction protrusion 1422 and continue flowing, please refer to... Figure 5 The top of the blocking protrusion 1422 has an arc-shaped structure.

[0045] Please refer to Figure 3 and Figure 4 A buffer pool 15 is provided between the fish passage area 11 and the entrance 10, and an energy dissipation pool 23 is provided at the exit 20. The surfaces of the fish passage area 11, buffer pool 15, and energy dissipation pool 23 are all covered with energy dissipation stones (not shown in the figure). Specifically, in this embodiment, the energy dissipation stones are natural pebbles. The energy dissipation stones embedded on the surface of the buffer pool 15 have a particle size of 10-15cm, the energy dissipation stones embedded on the surface of the fish passage area 11 have a particle size of 15-25cm, and the energy dissipation stones embedded on the surface of the energy dissipation pool 23 have a particle size of 40-60cm. The pebbles embedded in the three areas protrude 5-10cm above the bottom plate, forming a three-dimensional rough surface. As the water flows from the exit 20 of the culvert 100 to the entrance 10, the flow velocity gradually decreases. By setting energy dissipation stones with progressively decreasing particle sizes to correspond with the flow velocity, the flow velocity is reduced, buffering the impact of the water flow on the fish, providing a resting and gathering place for the fish before entering the culvert 100, and simulating the natural state of a river.

[0046] Please refer to Figure 4 At entrance 10, a fish guide weir 16 is also provided. The elevation of the weir top is slightly lower than the bottom plate of entrance 10 of culvert 100, so that the outflow of culvert 100 forms an obvious fish-attracting water flow, guiding downstream fish to search for the cave entrance upstream.

[0047] Specifically, the fish guide weir 16 is an arc-shaped fish guide weir 16, and its top can be provided with grooves or gaps to form multiple concentrated water flows, increasing the recognizability of the fish-attracting water flow.

[0048] Please refer to Figure 3 The fish migration device for small river dam structures also includes a vegetation restoration zone 50 set up around the culvert 100, which contains aquatic and wetland plants. By setting up the vegetation restoration zone 50, the riverbank area around the culvert 100 entrance and exit that has been disturbed by construction is restored with vegetation, planting suitable aquatic plants (such as calamus and reeds) and wetland plants, using the plant roots to stabilize the soil and protect the bank, while providing shade and shoreline habitat for fish.

[0049] A guide wall 21 is provided at the outlet 20. The guide wall 21 has a funnel-shaped structure, with one end of the guide wall 21 closer to the inlet 10 than the other end of the guide wall 21 further away from the inlet 10, which is closer to the central axis of the guide wall 21. The funnel-shaped guide wall 21 guides the water flow smoothly into the culvert 100.

[0050] Please refer to Figure 3 A regulating gate 22 is installed at outlet 20 to regulate the flow rate of water entering culvert 100. This allows for flexible adjustment of the water depth and flow rate within culvert 100 according to changes in upstream and downstream water levels, ensuring ecological connectivity in different seasons (especially the dry season).

[0051] It should be noted that the structural construction described in the above embodiments is mainly carried out during the dry season, without the need for large-scale demolition of the original structures, thus having little impact on the river environment and surrounding ecology. The materials can be sourced locally, which is in line with the concept of ecological priority.

Claims

1. A small river dam structure for fish migration, comprising a culvert (100) located on a dam (200), the culvert (100) having an inlet (10) and an outlet (20), the inlet (10) being at a lower height than the outlet (20), water flowing from the outlet (20) to the inlet (10), a fish passage area (11) between the inlet (10) and the outlet (20), a plurality of bottom sills (12) within the fish passage area (11), the bottom sills (12) being arranged side by side along the direction of water flow, the bottom sills (12) having fish passage openings (121), and a slope (13) and a slow-flow section (14) being formed between the plurality of bottom sills (12), the bottom surface of the slope (13) being inclined, the bottom surface of the slow-flow section (14) being horizontal, and the inlet (10) having a fish-attracting structure; Its features are: The inner wall of the slow-flow section (14) is provided with a plurality of sand accumulation grooves (141). The flow direction of the water in the sand accumulation grooves (141) and the flow direction of the water in the slow-flow section (14) intersect each other. The top of the sand accumulation grooves (141) is covered with a baffle (142). The baffle (142) is provided with a through hole (1421) for the sediment to fall into. It also includes multiple dredging pipes 1 (41) and multiple dredging pipes 2 (42) buried in the dam (200). The dam (200) is equipped with a blocking gate (45), which is used to control the connection between the dredging pipe 1 (41) and the external water flow. The dredging pipe 1 (41) is connected to the inlet of the sand accumulation groove (141), and the dredging pipe 2 (42) is connected to the outlet of the sand accumulation groove (141). The dredging pipe 1 (41) and the dredging pipe 2 (42) are both inclined. The bottom of the dredging pipe 1 (41) is connected to the sand accumulation groove (141). The top of the dredging pipe 1 (41) passes through the dam (200) and is connected to the river. The top of the dredging pipe 2 (42) is connected to the sand accumulation groove (141), and the bottom of the dredging pipe 2 (42) passes through the dam (200).

2. The fish migration device for small river dam structures according to claim 1, characterized in that: The baffle (142) is provided with a blocking protrusion (1422), and the baffle (142) has two sets of through holes (1421). The two sets of through holes (1421) are arranged side by side along the width direction of the sand accumulation groove (141), and the diameter of the through hole (1421) near the outlet (20) is larger than the diameter of the through hole (1421) away from the outlet (20). The two sets of through holes (1421) are located at the two ends of the blocking protrusion (1422).

3. The fish migration device for small river dam structures according to claim 1, characterized in that: A pressure stabilizing cavity is provided between the dredging pipe (41) and the sand accumulation groove (141). The pressure stabilizing cavity includes an arc section (43) and a gradually expanding section (44). The arc section (43) is located between the dredging pipe (41) and the gradually expanding section (44). The gradually expanding section (44) has a trumpet-shaped structure. The end of the gradually expanding section (44) with a larger opening is connected to the sand accumulation groove (141), and the end of the gradually expanding section (44) with a smaller opening is connected to the arc section (43).

4. The fish migration device for small river dam structures according to claim 1, characterized in that: The sand accumulation groove (141) is provided with a plurality of guide plates (143). The guide plates (143) are provided with sand accumulation holes (1431) corresponding to the through holes (1421). The guide plates (143) include an arc-shaped section (1432) and a guide section (1433). The arc-shaped section (1432) is located at the connection between the dredging pipe (41) and the sand accumulation groove (141). The guide section (1433) is inclined. A flushing groove (1434) is formed between the guide section (1433) and the bottom wall of the sand accumulation groove (141). The depth of the flushing groove (1434) near the dredging pipe (41) is greater than the depth of the flushing groove (1434) away from the dredging pipe (41).

5. The fish migration device for small river dam structures according to claim 4, characterized in that: The diameter of the sand accumulation hole (1431) is larger than the diameter of the through hole (1421).

6. The fish migration device for small river dam structures according to claim 2, characterized in that: The top of the blocking protrusion (1422) has an arc-shaped structure.

7. The fish migration device for small river dam structures according to claim 1, characterized in that: An energy dissipation pool (23) is provided at the outlet (20), and a buffer pool (15) is provided between the fish passage area (11) and the entrance (10). The surfaces of the fish passage area (11), the buffer pool (15) and the energy dissipation pool (23) are all covered with energy dissipation stones.

8. The fish migration device for small river dam structures according to claim 1, characterized in that: It also includes a vegetation restoration area (50) set around the culvert (100), which is provided with aquatic plants and wetland plants.

9. The fish migration device for small river dam structures according to claim 1, characterized in that: The outlet (20) is provided with a guide wall (21), which has a trumpet-shaped structure. The end of the guide wall (21) near the inlet (10) is closer to the central axis of the guide wall (21) than the end of the guide wall (21) away from the inlet (10).

10. The fish migration device for small river dam structures according to claim 1, characterized in that: A regulating gate (22) is provided at the outlet (20), which is used to regulate the flow rate of water entering the culvert (100).

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