A soil runoff observation plot structure

Abstract

The invention discloses a soil runoff observation cell structure, including a slope-shaped observation unit, an upper partition plate detachably connected to the upstream of the observation unit, a filter box arranged at the lower end of the observation unit, a surface flow water collection box, a soil mid-flow water collection box, and a soil bottom flow water collection box arranged in sequence at the rear end of the filter box from top to bottom, a water collection pipe sunk at the rear end of the upper end of the filter box, a notch is provided at the front end of the outer wall of the water collection pipe, a surface flow grate is detachably connected to the notch, a plurality of diversion pipes are connected to the rear end of the inner wall of the water collection pipe, a water level monitoring box is connected to one side below the rear end of the outer wall of the surface flow water collection box, the soil mid-flow water collection box, and the soil bottom flow water collection box, and side partition plates are arranged on both sides of the upper partition plate upstream of the observation unit. The invention is easy to construct and has less disturbance to the soil body, and will not cause the soil mid-flow to mix into the surface flow due to the impermeable partition wall, and can also classify and collect the surface flow, the sediment carried by the surface flow, the soil mid-flow, and the soil bottom flow, so as to improve the accuracy of measuring the amount of soil and water loss.

Description

Technical Field

[0001] The invention relates to the technical field of soil and water loss monitoring, and in particular to a soil runoff observation cell structure. Background Art

[0002] Soil and water loss on slopes is an important part of soil and water conservation monitoring and research. Runoff plots are a common method for observing the amount of soil and water loss on slopes. They are the main means to study the laws and mechanisms of soil and water loss on slope scales and to evaluate the effectiveness of soil and water conservation measures. Small and medium-sized runoff plots are smaller in area, and because their corresponding topography, soil properties, vegetation conditions, etc. are easier to grasp, they are often used in control tests in the field of soil erosion. Runoff plots generally include protection belts, ridges, plots surrounded by ridges, water channels, diversion pipes, water measuring facilities, drainage systems and other parts.

[0003] At present, the construction technology of soil erosion observation plots is usually to build walls with bricks or rocks around a certain size of land and then smooth the surface, or to build walls with concrete to form a rectangle. The wall at the lower end of the slope of the plot is connected to an observation pool or barrel for soil erosion observation. This causes great disturbance to the soil body and has high requirements for terrain. In addition, it is limited by the spatial scale and cannot flexibly observe the runoff conditions of different spatial scales and terrains. In addition, since the surrounding walls are impermeable, especially the walls at the foot of the slope of the plot, when the soil reaches saturation and water holding capacity under the action of rainfall, the mid-soil flow encounters the impermeable walls and seeps out to become surface flow, which increases the scouring of surface flow and causes excessive soil and water loss. Therefore, it is impossible to accurately assess soil erosion. The observation pool is usually simple in structure for the convenience of construction and can only collect surface flow. It is impossible to accurately observe and explore the formation conditions of mid-soil flow and bottom flow, their confluence process and mutual conversion law, and the continuity and volatility of the runoff process. Summary of the invention

[0004] The purpose of the present invention is to provide a soil runoff observation cell structure, which is easy to construct and has little disturbance to the soil. Not only will the intersoil flow not be mixed with the surface flow due to the impermeable partition wall, but the surface flow, the sediment carried by the surface flow, the intersoil flow, and the soil bottom flow can be classified and collected, thereby improving the accuracy of measuring the amount of soil and water loss.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A soil runoff observation cell structure, comprising an observation unit in a slope shape, wherein an upper partition extending into the soil is detachably connected to the upstream of the observation unit, a filter box is arranged at the lower end of the observation unit, and a surface flow water collection box, a mid-soil flow water collection box, and a soil bottom flow water collection box are arranged at the rear end of the filter box in order from top to bottom, wherein the volumes of the surface flow water collection box, the mid-soil flow water collection box, and the soil bottom flow water collection box decrease in order from top to bottom, and water inlets are provided inwardly along the length direction at the upper parts of the front ends of the outer walls of the mid-soil flow water collection box and the soil bottom flow water collection box, and anti-seepage plates are arranged above the mid-soil flow water collection box and the soil bottom flow water collection box in the filter box, and a gap is left between each anti-seepage plate and the front ends of the outer walls of the mid-soil flow water collection box and the soil bottom flow water collection box;

[0007] A hollow water collection pipe is sunken at the rear end of the upper end of the filter box, and a slot of one-quarter the size of the water collection pipe is opened inwardly on the front end of the outer wall of the water collection pipe along its length, and the lower end of the slot is flush with the lower end of the observation unit, and the upper end of the water collection pipe is detachably connected to a surface flow grate that cooperates with it at the position of the slot, and baffles that cooperate with it are set on the left and right sides of the water collection pipe, and a plurality of equally spaced fixed holes are opened inwardly on the rear end of the inner wall of the water collection pipe along its length, and each fixed hole is connected to a guide pipe extending into the surface flow water collection box, and a filter screen connected to it is set at the upper end of each guide pipe, and a water level monitoring hole is opened inward on one side below the rear end of the outer wall of the surface flow water collection box, the mid-flow water collection box and the bottom flow water collection box, and side partitions extending to its downstream are set on the left and right sides of the upper partition upstream of the observation unit.

[0008] By adopting the above technical scheme, when in use, first dig a foundation pit downstream of the observation unit, then place the filter box at the front end of the foundation pit and fix it, so that the front end of the filter box is close to the front end of the foundation pit, and then install the soil bottom flow water collection box, the soil mid-flow water collection box, and the surface flow water collection box from bottom to top at the rear end of the filter box in turn, and make the water inlets of the soil mid-flow water collection box and the soil bottom flow water collection box close to the bottom of the corresponding anti-seepage plate respectively, and then install the water collection pipe behind the upper end of the filter box, and make the notch flush with the slope of the observation unit, and then let the guide pipes in the fixing hole extend into the surface flow water collection box, and then install the surface flow grate on the notch, and then plug the water level monitoring holes on the surface flow water collection box, the soil mid-flow water collection box and the soil bottom flow water collection box, and then fill the filter box, the surface flow water collection box, the soil mid-flow water collection box and the soil bottom flow water collection box with soil and fix them in turn;

[0009] Then bury the upper baffle in the appropriate position upstream of the observation unit, bury the side baffles on the left and right sides of the upper baffle and allow them to extend to the downstream of the observation unit. When it rains, the rainwater in the space enclosed by the upper baffle and the side baffle on the observation unit scours and erodes the surface soil. With the infiltration of rainwater, the rainwater gradually enters the soil middle flow layer and the soil bottom flow layer. The surface flow is filtered along the surface flow grate on the notch of the observation unit and enters the water collection pipe. Vegetation litter is blocked by the surface flow grate, and the silt carried by the surface flow is blocked by the baffle and settled in the water collection pipe. As the surface flow gradually increases, the amount of water in the water collection pipe increases and the diversion pipe in the fixed hole diverts the water to the surface flow water collection tank, while the midflow and bottom flow continue to infiltrate and flow downstream under the action of gravity, and the sediment is filtered by the filter box and then enters the corresponding midflow and bottom flow water collection tanks through the water inlet. Finally, the surface flow grate is removed to collect the sediment at the bottom of the water collection pipe, and then the respective water level lines are determined by the water level monitoring boxes of the surface flow, midflow and bottom flow, so as to measure the amount of soil and water loss, and obtain different runoff samples as needed.

[0010] The present invention is further configured as follows: the total length of the upper partition is 80 cm, of which 60 cm of the observation unit is buried and 20 cm extends out of the observation unit; the side partition is arranged along the slope of the observation unit and has a height of 80 cm, of which 60 cm of the observation unit is buried and 20 cm extends out of the observation unit.

[0011] By adopting the above technical solution: By adopting the above technical solution, the soil mid-flow in the 0-30cm soil layer and the soil bottom flow in the 30-60cm soil layer can be prevented from seeping out of the observation unit.

[0012] The present invention is further configured as follows: the aperture of the surface flow grate is 1 cm.

[0013] The present invention is further configured as follows: the filter box comprises a box body with holes at both ends, four filter areas filled with crushed stone, gravel, coarse sand and fine sand in sequence from front to back, and a filter pad layer arranged at the front end of each filter area and composed of a permeable fabric and a sponge pad layer.

[0014] By adopting the above technical solution, the flow diversion speed can be maintained without affecting the occurrence of blockage.

[0015] The present invention is further configured as follows: the diameter of the crushed stone is 2-5 cm, the diameter of the gravel is 1-2 cm, the diameter of the coarse sand is 0.1-1 cm, and the diameter of the fine sand is less than 0.1 mm.

[0016] The present invention is further configured as follows: the distance between the corresponding anti-seepage plate of the mid-flow water collecting box and the upper end of the inner wall of the box is 30 cm, and the mid-flow water collecting box collects runoff at a soil depth of 0-30 cm; the distance between the corresponding anti-seepage plate of the soil bottom flow water collecting box and the upper end of the inner wall of the box is 60 cm, and the soil bottom flow water collecting tank collects runoff at a soil depth of 30-60 cm.

[0017] The present invention is further configured as follows: the gaps between each anti-seepage plate and the mid-soil flow water collection box and the bottom-soil flow water collection box are filled with sponge blocks.

[0018] By adopting the above technical solution, it is possible to prevent sediment from flowing into the mid-flow water collection tank and the bottom-flow water collection tank, and at the same time, it is possible to prevent the gap between the anti-seepage plate and the mid-flow water collection tank and the bottom-flow water collection tank from being blocked.

[0019] The present invention is further configured as follows: the surface flow water collecting tank, the mid-soil flow water collecting tank and the bottom flow water collecting tank are all provided with water level monitoring boxes which are connected thereto and have an open upper end at the positions corresponding to the water level monitoring holes; the upper end of each water level monitoring box extends to the upper end of the surface flow water collecting tank and is located at the same horizontal height therewith; and the open end of each water level monitoring box is detachably connected to a box cover which matches therewith.

[0020] By adopting the above technical scheme, it is not only convenient for observers to read the buoyancy scale through the buoyancy scale and accurately measure the water collection volume of the surface flow water collection tank, the mid-soil flow water collection tank and the bottom flow water collection tank, but also the runoff samples in each water collection tank can be obtained by using a water level monitoring box in conjunction with a pumping device.

[0021] The present invention is further configured as follows: each water level monitoring hole is connected to a connecting pipe extending into a corresponding water level monitoring box.

[0022] The present invention is further configured as follows: the surface flow water collection tank, the mid-soil flow water collection tank, and the bottom-soil flow water collection tank are all tilted backwards by 1° along with the observation unit.

[0023] By adopting the above technical solution, the water in the surface flow water collection tank, the mid-soil flow water collection tank and the bottom flow water collection tank can be more conveniently extracted and cleaned, which is convenient for the next observation.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] First, the invention is easy to construct and has little disturbance on the soil. It will not cause the inflow in the soil to be mixed with the surface flow due to the impermeable partition wall. It can also classify and collect the surface flow, the sediment carried by the surface flow, the inflow in the soil, and the bottom flow, thereby improving the accuracy of measuring the amount of soil and water loss.

[0026] Second, the present invention does not require hard infrastructure construction on the slope, which facilitates the collection and measurement of runoff surface source pollutants on the slope;

[0027] Thirdly, the present invention is not only easy to construct and can be used twice, but also can observe and accurately measure the loss of surface flow, mid-soil flow, bottom flow and surface flow erosion sediment of the observation unit in real time during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 It is mainly used to show the position and connection relationship of each component;

[0030] Figure 3 It is mainly used to show the structural schematic diagram of the filter box and the water collection box of the present invention;

[0031] Figure 4 It is mainly used to display the water level monitoring box and water level monitoring hole;

[0032] Figure 5 It is mainly used to display the water collection pipe, fixing hole, diversion pipe and filter screen;

[0033] Figure 6 It is a structural schematic diagram of the surface flow grate of the present invention.

[0034] In the figure: 1. Observation unit; 11. Upper partition; 12. Filter box; 13. Box body; 14. Filter area; 15. Filter cushion layer; 16. Anti-seepage plate; 17. Surface flow water collection tank; 18. Mid-flow water collection tank; 19. Bottom flow water collection tank; 2. Water inlet; 21. Sponge block; 22. Water level monitoring hole; 23. Water collection pipe; 24. Notch; 25. Surface flow grate; 26. Baffle; 27. Fixing hole; 28. Guide pipe; 29. ​​Filter net; 3. Connecting pipe; 31. Water level monitoring box; 32. Box cover; 33. Side partition. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0036] Example, see Figure 1-6A soil runoff observation cell structure comprises an observation unit 1 in a slope shape, an upper partition 11 with a total length of 80 cm and a lower end thereof extending 60 cm into the soil of the observation unit 1 and 20 cm out of the soil of the observation unit 1 is detachably connected to the upstream of the observation unit 1, a filter box 12 is arranged at the lower end of the observation unit 1, the filter box 12 comprises a box body 13 with holes at both ends, four filter areas 14 filled with crushed stone with a diameter of 2-5 cm, gravel with a diameter of 1-2 cm, coarse sand with a diameter of 0.1-1 cm, and fine sand with a diameter of less than 0.1 mm from front to back, and a filter pad layer 15 arranged at the front end of each filter area 14 and composed of a permeable fabric and a sponge pad layer.

[0037] The rear end of the filter box 12 is provided with a surface flow water collection box 17, a soil mid-flow water collection box 18, and a soil bottom flow water collection box 19 in sequence from top to bottom. The volumes of the surface flow water collection box 17, the soil mid-flow water collection box 18, and the soil bottom flow water collection box 19 decrease in sequence from top to bottom and are all tilted backward by 1° along the slope of the observation unit 1. A water inlet 2 is provided inwardly along the length direction at the top of the front end of the outer wall of the soil mid-flow water collection box 18 and the soil bottom flow water collection box 19. An anti-seepage plate 16 is provided above each water inlet 2 in the filter box 12. The distance between the water inlet 2 of the water tank 18 and the upper end of the inner wall of the box body 13 corresponding to the anti-seepage plate 16 is 30 cm, and the mid-flow water collecting tank 18 collects runoff with a soil depth of 0-30 cm. The distance between the water inlet 2 of the soil bottom flow water collecting tank 19 and the upper end of the inner wall of the box body 13 corresponding to the anti-seepage plate 16 is 60 cm, and the soil bottom flow water collecting tank 19 collects runoff with a soil depth of 30-60 cm. A sponge block 21 is left and filled between each anti-seepage plate 16 and the front end of the outer wall of the mid-flow water collecting tank 18 and the soil bottom flow water collecting tank 19.

[0038] A hollow water collection pipe 23 is sunken at the rear end of the upper end of the filter box 12. A slot 24 that is one-quarter the size of the water collection pipe 23 is opened inwardly along its length on the front end of the outer wall of the water collection pipe 23. The lower end of the slot 24 is flush with the lower end of the observation unit 1. A surface flow grate 25 with a hole diameter of 1 cm is detachably connected to the upper end of the water collection pipe 23 at the position of the slot 24. A baffle 26 that matches the water collection pipe 23 is set on both sides of the left and right sides. A plurality of fixed holes 27 distributed at equal intervals are opened inwardly along its length on the rear end of the inner wall of the water collection pipe 23. Each fixed hole 27 is connected to a guide pipe 28 extending into the surface flow water collection box 17. A filter screen 29 connected to the upper end of each guide pipe 28 is set.

[0039] A water level monitoring hole 22 is opened inward on one side below the rear end of the outer wall of the surface flow water collecting tank 17, the soil mid-flow water collecting tank 18 and the soil bottom flow water collecting tank 19. The surface flow water collecting tank 17, the soil mid-flow water collecting tank 18 and the soil bottom flow water collecting tank 19 are provided with a water level monitoring box 31 connected with them and opened at the upper end at the position corresponding to the water level monitoring hole 22. Each water level monitoring hole 22 is connected with a connecting pipe 3 extending into the corresponding water level monitoring box 31. The upper end of each water level monitoring box 31 extends to the upper end of the surface flow water collecting tank 17 and is located at the same horizontal height. The open end of each water level monitoring box 31 is detachably connected to a box cover 32 that matches it. A side partition 33 is provided on the left and right sides of the upper partition 11 upstream of the observation unit 1, which is set along the slope of the observation unit 1 and has a height of 80 cm. The lower end of the side partition 33 is buried 60 cm in the soil of the observation unit 1 and the upper end extends 20 cm out of the soil of the observation unit 1.

[0040] Method of use: When using, first dig a foundation pit downstream of the observation unit 1, then place the filter box 12 at the front end of the foundation pit and fix it, so that the front end of the filter box 12 is close to the front end of the foundation pit, and then install the soil bottom flow water collection box 19, soil mid-flow water collection box 18, and surface flow water collection box 17 at the rear end of the filter box 12 from bottom to top and tilt it backward 1° along the slope of the observation unit 1, and let the water inlet 2 of the soil mid-flow water collection box 18 and the soil bottom flow water collection box 19 be close to the corresponding anti-seepage plate 16 respectively, and then install the water collection pipe 23 in the filter box 1 2, and make the notch 24 flush with the slope of the observation unit 1, then let the guide pipe 28 in the fixing hole 27 extend into the surface flow water collection box 17, then install the surface flow grate 25 on the notch 24 and fix it, then connect the connecting pipe 3 with the water level monitoring hole 22 and fix it, then connect the corresponding water level monitoring box 31 with the corresponding connecting pipe 3 and fix it, cover the corresponding water level monitoring box 31 with the box cover 32, and finally fill the soil to fix the filter box 12, the surface flow water collection box 17, the mid-soil flow water collection box 18, the bottom flow water collection box 19 and the water collection pipe 23 in sequence.

[0041] Then bury the upper partition 11 in an appropriate position upstream of the observation unit 1, with its lower end penetrating 60 cm into the soil of the observation unit 1 and its upper end protruding 20 cm from the soil of the observation unit 1. Then bury two side partitions 33 on the left and right sides of the upper partition 11 of the observation unit 1, respectively, and let their lower ends extend 60 cm into the soil and their upper ends extend 20 cm from the soil. When it rains, the rainwater in the space enclosed by the upper partition 11 and the side partition 33 upstream of the observation unit 1 scours and erodes the surface soil. As the rainwater penetrates, the rainwater gradually The surface flow gradually enters the soil mesostream layer and the soil bottom flow layer, while the surface flow flows downward along the observation unit 1 and enters the water collection pipe 23 after being filtered by the surface flow grate 25 on the notch 24. The soil is blocked by the baffle 26 and settles in the water collection pipe 23. As the surface flow gradually increases, the water volume in the water collection pipe 23 increases and the water body is drained into the surface flow water collection box 17 by the guide pipe 28 in the fixed hole 27. When the guide pipe 28 is draining, the filter net 29 can further filter the water body and leave the sediment carried by the surface flow in the water collection pipe 23.

[0042] The mid-soil flow and the bottom-soil flow continue to infiltrate and flow down the slope under the action of gravity and are filtered by the filter box 12. Due to the obstruction of the anti-seepage plate 16, the mid-soil flow will not infiltrate into the bottom-soil flow, and the water at the corresponding depth will be filtered respectively and sequentially through the filter cushion layer 15, crushed stone, gravel, coarse sand and fine sand in the box body 13, and then blocked and filtered again by the corresponding sponge blocks 21, and then flow into the corresponding mid-soil flow water collection box 18 and the bottom-soil flow water collection box 19 through their respective water inlets 2. The water entering the surface flow water collection box 17, the mid-soil flow water collection box 18 and the bottom-soil flow water collection box 19 will also flow into the corresponding water level monitoring box 31 through the connecting pipe 3 in the water level monitoring hole 22.

[0043] When it is necessary to check the water volume of a certain water collection box, it is only necessary to open the box cover 32, and then use the buoyancy scale to measure the water level height in the corresponding water level monitoring box 31, and finally remove the surface flow grate 25 and collect the mud and sand at the bottom of the water collection pipe 23 with a scraper to measure the soil loss of the observation unit 1. If necessary, the box cover 32 can be opened, and the water in each water collection tank can be pumped out through the water level monitoring box 31 using a pumping device.

[0044] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A soil runoff observation plot structure, comprising a slope-shaped observation unit (1), characterized in that: The upper partition (11) extending into the soil is detachably connected to the upstream of the observation unit (1), and the lower end of the observation unit (1) is provided with a filter box (12). The rear end of the filter box (12) is provided with a surface flow water collection box (17), a mid-soil flow water collection box (18), and a bottom-soil flow water collection box (19) in sequence from top to bottom. The volumes of the surface flow water collection box (17), the mid-soil flow water collection box (18), and the bottom-soil flow water collection box (19) decrease in sequence from top to bottom. A water inlet (2) is provided inwardly above the front end of the outer wall of the mid-soil flow water collection box (18) and the bottom-soil flow water collection box (19). An anti-seepage plate (16) is provided above each water inlet (2) in the filter box (12), and a gap is left between each anti-seepage plate (16) and the front end of the outer wall of the mid-soil flow water collection box (18) and the bottom-soil flow water collection box (19); The rear end of the upper end of the filter box (12) is sunken and provided with an internally hollow water collection pipe (23). The front end of the outer wall of the water collection pipe (23) is provided with a notch (24) of one quarter of the size of the water collection pipe (23) inwardly along its length direction. The lower end of the notch (24) is flush with the lower end of the observation unit (1). The upper end of the water collection pipe (23) is detachably connected to a surface flow grate (25) cooperating with the notch (24). The left and right sides of the water collection pipe (23) are provided with baffles (26) cooperating with the water collection pipe (23). The rear end of the inner wall of the water collection pipe (23) is provided with a notch (24) of one quarter of the size of the water collection pipe (23) inwardly along its length direction. A plurality of fixed holes (27) are provided inwardly and are distributed at equal intervals. Each fixed hole (27) is connected to a guide pipe (28) extending into the surface flow water collection box (17). A filter screen (29) is provided at the upper end of each guide pipe (28) and is connected thereto. A water level monitoring hole (22) is provided inwardly on one side below the rear end of the outer wall of the surface flow water collection box (17), the mid-flow water collection box (18) and the bottom flow water collection box (19). Side baffles (33) extending to the downstream are provided on the left and right sides of the upper baffle (11) upstream of the observation unit (1).

2. A soil runoff observation plot structure according to claim 1, characterized in that: The total length of the upper partition (11) is 80 cm, of which 60 cm is buried in the observation unit (1) and 20 cm is extended out of the observation unit (1). The side partition (33) is arranged along the slope of the observation unit (1) and has a height of 80 cm, of which 60 cm is buried in the observation unit (1) and 20 cm is extended out of the observation unit (1).

3. A soil runoff observation plot structure according to claim 1, characterized in that: The aperture of the surface flow grate (25) is 1 cm.

4. A soil runoff observation plot structure according to claim 1, characterized in that: The filter box (12) comprises a box body (13) with holes at both the front and rear ends, four filter areas (14) filled with crushed stone, gravel, coarse sand and fine sand in sequence from front to back, and a filter pad layer (15) arranged at the front end of each filter area (14) and composed of a permeable fabric and a sponge pad layer.

5. A soil runoff observation plot structure according to claim 4, characterized in that: The diameter of the crushed stone is 2-5 cm, the diameter of the gravel is 1-2 cm, the diameter of the coarse sand is 0.1-1 cm, and the diameter of the fine sand is less than 0.1 mm.

6. A soil runoff observation plot structure according to claim 4, characterized in that: The distance between the anti-seepage plate (16) corresponding to the mid-soil flow water collection box (18) and the upper end of the inner wall of the box body (13) is 30 cm, and the mid-soil flow water collection box (18) collects runoff at a soil depth of 0-30 cm. The distance between the anti-seepage plate (16) corresponding to the bottom-soil flow water collection box (19) and the upper end of the inner wall of the box body (13) is 60 cm, and the bottom-soil flow water collection box (19) collects runoff at a soil depth of 30-60 cm.

7. The soil runoff observation plot structure according to claim 1 is characterized by: The gaps between each anti-seepage plate (16) and the mid-flow water collection box (18) and the bottom-flow water collection box (19) are filled with sponge blocks (21).

8. The soil runoff observation plot structure according to claim 1 is characterized by: The surface flow water collecting tank (17), the mid-soil flow water collecting tank (18) and the bottom-soil flow water collecting tank (19) are all provided with water level monitoring boxes (31) at positions corresponding to the water level monitoring holes (22) which are connected thereto and have an open upper end. The upper end of each water level monitoring box (31) extends to the upper end of the surface flow water collecting tank (17) and is located at the same horizontal height therewith. The open end of each water level monitoring box (31) is detachably connected with a box cover (32) which matches therewith.

9. A soil runoff observation plot structure according to claim 8, characterized in that: Each water level monitoring hole (22) is connected to a connecting pipe (3) extending into a corresponding water level monitoring box (31).

10. The soil runoff observation plot structure according to claim 1, characterized in that: The surface flow water collection tank (17), the mid-soil flow water collection tank (18), and the bottom-soil flow water collection tank (19) are all tilted backwards by 1° along the slope of the observation unit (1).

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