An experimental apparatus and method for mitigating the adverse effects of TDG supersaturation in river water.

Abstract

This invention belongs to the field of water conservancy engineering technology and discloses an experimental device and method for mitigating the adverse effects of TDG supersaturation in river channels. The experimental device includes an experimental flume, a first retaining wall and a vegetated curtain wall disposed within the flume. The first retaining wall is located upstream of the flume's protected area. The vegetated curtain wall is disposed behind the first retaining wall and on the side of the protected area away from the flume's sidewall. It also includes a second retaining wall, located behind the vegetated curtain wall and on the extension line of the long side of the first retaining wall. This invention is the first to propose a method for mitigating the effects of TDG supersaturation in localized areas of reservoir channels using a vegetated curtain wall, thereby reducing the harm of TDG supersaturation to fish. This provides basic data and theoretical basis for research on mitigation measures to address the adverse effects of TDG supersaturation.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering technology, and relates to dissolved gas supersaturation technology, and in particular to an experimental device and method for mitigating the adverse effects of total dissolved gas supersaturation in local areas of river channels. Background Technology

[0002] Hydropower construction has developed rapidly in recent years and achieved tremendous success. While generating significant social and economic benefits, the operation of hydropower stations has also brought widespread attention to environmental issues. The problem of supersaturation of total dissolved gases accompanying flood discharge from hydropower stations has received considerable concern.

[0003] When a high dam releases water, a large amount of air is drawn into the depths of the stilling basin by the water jet and dissolves in the water under high pressure, causing supersaturation of total dissolved gas (TDG). Supersaturated TDG is difficult to release into the air in a short time and will be transported downstream. Simultaneously, the construction of cascade reservoirs transforms the downstream channels of the previous cascade into reservoir areas for the next cascade. Increased water depth and reduced flow velocity in these reservoir areas further delay TDG release, leading to a cumulative effect of TDG supersaturation along the river channels of the cascade power stations. Fish and other aquatic organisms living in TDG-saturated water for extended periods may suffer from gas bubble disease (GBD) or even die.

[0004] Wild fish in rivers can intermittently compensate for TDG oversaturation by altering their swimming depth to a safe level. However, for fish cultured in net cages in reservoirs, the maximum swimming depth is limited to the cage depth. Therefore, when TDG oversaturation occurs, the harmful effects of oversaturated TDG cannot be avoided. This can lead to large-scale gas bubble disease and even death in cage-cultured fish, reducing fishery yields, impacting economic benefits, and harming the aquatic ecosystem of the reservoir. How to mitigate the adverse effects of TDG oversaturation is one of the technical problems that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings and defects of existing technologies by providing an experimental device and method for mitigating the adverse effects of TDG supersaturation in river waters. This device will also be used to conduct research on the mechanisms by which vegetation curtains and retaining walls promote the release of supersaturated TDG. This has significant theoretical and engineering value for studying the adverse effects of supersaturated TDG on fish in cage aquaculture in reservoirs. Furthermore, it can provide important basic data and theoretical basis for research on mitigation measures for the adverse effects of supersaturated TDG.

[0006] The release of supersaturated TDG is closely related to hydraulic properties such as flow velocity, water depth, and turbulent kinetic energy. During the research, it was found that when water flows through vegetation, the vegetation obstructs the flow, increasing the river depth and altering the hydraulic properties and flow structure. Furthermore, experimental studies showed that in TDG-saturated water, solid surfaces adsorb the supersaturated TDG, thus accelerating its release. Therefore, when TDG-saturated water submerges vegetation, the abundant vegetation branches and leaves provide numerous surface boundaries for dissolved gas release, promoting the release of supersaturated TDG to some extent. Developing technologies to mitigate the adverse effects of TDG supersaturation using vegetation in reservoir water bodies would have significant practical application value and real-world implications for the development of cage aquaculture in reservoir areas.

[0007] Based on this, the present invention provides an experimental device for mitigating the adverse effects of TDG supersaturation in river water, which includes an experimental water tank, a first retaining wall and a vegetation curtain wall set inside the experimental water tank; the first retaining wall is located upstream of the experimental water tank protection zone; the vegetation curtain wall is set behind the first retaining wall and is located on the side of the protection zone away from the side wall of the experimental water tank.

[0008] The experimental setup described above, designed to mitigate the adverse effects of TDG supersaturation in river water, prevents the incoming flow from directly entering the protected area downstream. Instead, the flow is directed to slowly enter the protected area along a vegetation curtain. The vegetation curtain alters the hydraulic properties of the water body while adsorbing supersaturated TDG, thereby reducing the TDG saturation level of the water flowing into the protected area.

[0009] The first retaining wall refers to an impermeable retaining wall perpendicular to the direction of water flow in front of the protected area. The first retaining wall is L-shaped, and its length extends along the direction of water flow to the front of the protected area. The width of the first retaining wall covers the width of the protected area and the width of the vegetation curtain wall. The height of the first retaining wall should be higher than the water surface so that the water will not overflow the retaining wall and flow directly into the protected area.

[0010] The size, density, and location of the vegetation curtain wall are related to the width and depth of the river channel; the length of the vegetation curtain wall along the direction of water flow is equal to the length of the protected area; and the height of the vegetation curtain wall is higher than the height of the water area within the protected area. The preferred vegetation species for the vegetation curtain wall are simulated shrubs with abundant branches and leaves and a large contact area, as this type of vegetation curtain wall provides better mitigation.

[0011] The experimental device described above for mitigating the adverse effects of TDG supersaturation in river water also includes a second retaining wall. The second retaining wall is located behind the vegetation curtain wall and on the extension line of the long side of the first retaining wall. The height of the second retaining wall is the same as the height of the first retaining wall, and the length of the second retaining wall can be set to more than 2 meters to prevent the supersaturated TDG flow from flowing back to the protected area. In a preferred embodiment, the length of the second retaining wall can be set to 2-10 meters.

[0012] This invention also provides an experimental method for mitigating the adverse effects of TDG supersaturation in river water, comprising the following steps:

[0013] (1) Prepare several perforated bottom plates and place them on the experimental water tank beach. Insert simulated vegetation on the perforated bottom plates on the outer edge of the protected area on the experimental water tank beach. The simulated vegetation is arranged in an alternating manner.

[0014] (2) Turn on the TDG supersaturated water generating device, inject TDG supersaturated water into the experimental water tank, adjust the flow rate, and wait until the supersaturated TDG water fills the water tank. Adjust the water-blocking device at the end of the water tank so that the water depth on the beach of the experimental water tank reaches more than 10cm. Wait for the water flow to stabilize.

[0015] (3) After the water flow in the experimental tank stabilizes, use a TDG measuring instrument to measure the TDG saturation values ​​of the water in the protected area and outside the protected area of ​​the experimental tank, and record the experimental data.

[0016] By changing different flow rates, different inflow TDG saturation, and different simulated vegetation, (1)-(3) were repeated to obtain the variation law of supersaturated TDG saturation in the protected area with flow rate, inflow TDG saturation, and vegetation type under different working conditions.

[0017] This invention also provides a method for mitigating the adverse effects of TDG supersaturation in river water. The method involves arranging a first retaining wall and a vegetation curtain wall within the river channel. The first retaining wall is located upstream of the river channel protection area. The vegetation curtain wall is located behind the first retaining wall, on the side of the protection area furthest from the riverbank. The first retaining wall is L-shaped, extending along the water flow direction to the front end of the protection area. This prevents supersaturated TDG water from flowing into the protection area from the front end. The width of the first retaining wall covers both the width of the protection area and the width of the vegetation curtain wall. The height of the first retaining wall should be higher than the water surface to prevent water from overflowing the retaining wall and flowing directly into the protection area. The size, density, and location of the vegetation curtain wall are related to the width and depth of the river channel. The length of the vegetation curtain wall along the water flow direction is equal to the length of the protection area. The height of the vegetation curtain wall is higher than the water level of the protection area.

[0018] The aforementioned method for mitigating the adverse effects of TDG supersaturation in river water also includes a second retaining wall. The second retaining wall is located behind the vegetation curtain wall and on the extension line of the long side of the first retaining wall. The height of the second retaining wall is the same as the height of the first retaining wall, and the length of the second retaining wall can be set to more than 2 meters to prevent the supersaturated TDG flow from flowing back to the protected area. In a preferred implementation, the length of the second retaining wall can be set to 2-10 meters.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] (1) This invention is the first to propose a method to mitigate the harm of TDG oversaturation to fish by using vegetation curtain walls to alleviate the impact of TDG oversaturation in local areas of reservoirs and rivers. This provides basic data and theoretical basis for the research on mitigation measures to alleviate the adverse effects of TDG oversaturation.

[0021] (2) The present invention has a good effect on the release of supersaturated TDG in the downstream water of the dam, and has important engineering significance for mitigating the supersaturated TDG generated by the discharge of water from water conservancy projects and the adverse effects of supersaturated TDG on fish in cage aquaculture.

[0022] (3) This invention uses vegetation that is fish-friendly, low-cost, requires few items, and has no special requirements.

[0023] (4) This invention demonstrates that adding a vegetation curtain wall to the experimental water tank can promote the release of TDG; and proves that different vegetation types have different effects on promoting the release of TDG; and that the release of TDG is also different under different inflow conditions. Attached Figure Description

[0024] Figure 1 A schematic diagram of an experimental setup to mitigate the adverse effects of TDG oversaturation in river water; where 1-experimental water tank, 2-first retaining wall, 3-vegetated curtain wall area, 4-second retaining wall, 5-protected area, 6-TGP measuring instrument;

[0025] Figure 2 This is a schematic diagram of the dimensions and structure of the base plate used to place the vegetation;

[0026] Figure 3 A schematic diagram showing the measurement points of oversaturated TDG;

[0027] Figure 4 This is a schematic diagram of the simulated shrub arrangement;

[0028] Figure 5 This is a graph showing the difference in TDG saturation between point ① inside the protected area and point ② outside the protected area in the experimental water tank. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are part of the present invention.

[0030] Example 1

[0031] The experimental apparatus provided in this embodiment for mitigating the adverse effects of TDG supersaturation in river water is as follows: Figures 1 to 3As shown, it includes an experimental water tank 1, a first retaining wall 2, a second retaining wall 4, and a TGP measuring instrument 6.

[0032] In this embodiment, a test tank is used as the experimental tank. The experimental tank 1 is the main body of the entire experimental device. A first retaining wall 2 is located at its uppermost end to prevent the supersaturated TDG water from directly entering the protected area 5. Behind the first retaining wall 2 is a vegetation curtain wall area 3, in which a perforated base plate is laid on the ground to arrange the vegetation curtain wall to mitigate the adverse effects of TDG supersaturation. A second retaining wall 4 is located behind the vegetation curtain wall area 3 and on the extension line of the long side of the first retaining wall. A TGP measuring instrument 6 is used to measure the degree of TDG supersaturation in the water bodies inside and outside the protected area of ​​the experimental tank.

[0033] The TGP (Total Dissolved Gas Pressure) meter is used to measure the degree of TDG supersaturation in water. The Point Four TDG meter, manufactured by Pentair in Minnesota, USA, has a range of 0%-200% and an accuracy of ±1%. The instrument can also measure water temperature simultaneously, with a range of 0℃-40℃ and an accuracy of ±0.2℃.

[0034] according to Figure 1 The experimental setup was arranged and all components and instruments were connected. Experimental water tank 1 is 10m long, 3m wide, and 30cm high, with a slope of 1‰. An electromagnetic flowmeter is installed at the front end of experimental water tank 1 to measure the incoming flow rate. The first retaining wall is L-shaped, 2m long, 1m wide, and 0.11m high, designed to prevent supersaturated TDG water from flowing into the front of the protected area. Figure 2 As shown, the perforated base plates used in the vegetation curtain wall area have a total length of 4m and a width of 0.5m (each base plate is 1m long, and 4 plates are placed). The second retaining wall is 2m long.

[0035] The vegetation curtain wall area uses simulated shrubs and simulated grass, all made of polyvinyl chloride (PVC). The surface area of ​​a single simulated shrub is 0.074 m². 2 The artificial grass consists of approximately 1200 grass blades per square meter, each blade approximately 0.5cm wide and 20cm high. These blades were then sequentially fixed in the vegetation curtain wall area 3 within the experimental water tank 1 under different working conditions. Figure 4 As shown, a staggered arrangement was used, and the simulated shrub density was 116 plants / m². 2 .

[0036] This embodiment conducts experiments under eight operating conditions, including two vegetation types, two saturation levels, and two flow rates. The specific settings for the eight operating conditions are shown in Table 1.

[0037] Table 1 Operating Condition Settings

[0038] Operating condition number vegetation type Initial saturation (%) at the front end of the water tank Flow rate (L / s) 1 artificial shrubs 130 40 2 artificial shrubs 150 40 3 artificial shrubs 130 60 4 artificial shrubs 150 60 5 Artificial grass 130 40 6 Artificial grass 150 40 7 Artificial grass 130 60 8 Artificial grass 150 60

[0039] Using the above experimental setup, conduct the experiment according to the settings of each working condition in Table 1. The specific operating steps of the entire experiment are as follows:

[0040] (1) Before the experiment on the 8 working conditions, vegetation was arranged in the vegetation curtain wall arrangement area, and supersaturated water generated by the TDG supersaturated water generation system was injected into the experimental water tank. Among them, the vegetation in the experimental water tank of working conditions 1-4 was simulated shrubs, and the vegetation in the experimental water tank of working conditions 4-8 was simulated grass.

[0041] (2) Turn on the TDG supersaturated water generating device, inject TDG supersaturated water into the experimental water tank, adjust the flow rate, and wait until the supersaturated TDG water fills the water tank. Adjust the water-blocking device at the end of the water tank so that the water depth on the beach of the experimental water tank reaches more than 10cm. Wait for the water flow to stabilize.

[0042] (3) After the flow of supersaturated water in the experimental tank stabilizes, use the TGP measuring instrument 6 to measure the TDG supersaturation in the experimental tank and record the experimental data.

[0043] After the TDG supersaturation of the water in the experimental water tank 5 is measured in step (3) above, the supersaturated water in the experimental water tank 5 is drained and the vegetation type of the vegetation curtain wall area is adjusted.

[0044] The TDG saturation setting for the incoming stream is as follows:

[0045] The TDG saturation of the incoming flow is 130% under operating conditions 1, 3, 5, and 7.

[0046] The TDG saturation of the incoming flow is 150% under operating conditions 2, 4, 6, and 8.

[0047] The incoming flow settings are as follows:

[0048] The inflow rate for operating conditions 1, 2, 5, and 6 is 40 L / s;

[0049] The inflow rate for operating conditions 3, 4, 7, and 8 is 60 L / s;

[0050] Until the experiment under 8 working conditions is completed.

[0051] The TDG supersaturation of the water bodies inside and outside the experimental water tank protection zone was measured using a TGP meter (measuring point settings are as follows). Figure 3 As shown in Table 2, the experimental results for each working condition are as follows: Figure 5 Show.

[0052] Based on the TDG supersaturation and TDG saturation difference under various working conditions, it can be seen that the vegetation curtain wall has a significant effect on promoting the release of TDG from the water.

[0053] Table 2. Experimental results under various working conditions

[0054]

[0055] Example 2

[0056] This embodiment provides a method to mitigate the adverse effects of TDG supersaturation in river channels. A first retaining wall and a vegetation curtain wall are arranged within the river channel. The first retaining wall is located upstream of the river channel protection area. The vegetation curtain wall is located behind the first retaining wall, on the side of the protection area furthest from the riverbank. The first retaining wall is L-shaped, extending along the water flow direction to the front of the protection area. The width of the first retaining wall covers both the width of the protection area and the width of the vegetation curtain wall. The height of the first retaining wall should be higher than the water surface to prevent water from overflowing the retaining wall and flowing directly into the protection area. The size, density, and location of the vegetation curtain wall are related to the width and depth of the river channel. The length of the vegetation curtain wall along the water flow direction is equal to the length of the protection area. The height of the vegetation curtain wall is higher than the height of the water area within the protection area.

[0057] The aforementioned methods for mitigating the adverse effects of TDG supersaturation in river water also include a second retaining wall. This second retaining wall is located behind the vegetation curtain wall and on the extension of the long side of the first retaining wall. The height of the second retaining wall is the same as the height of the first retaining wall, and its length is 2m-10m, to prevent the supersaturated TDG flow from flowing back to the protected area.

[0058] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An experimental device for mitigating the adverse effects of TDG supersaturation in a riverine water body, characterized in that, The experimental device comprises an experimental flume, a first retaining wall, a second retaining wall and a vegetation curtain wall arranged in the experimental flume; the first retaining wall is located upstream of a protected area of the experimental flume; the vegetation curtain wall is arranged behind the first retaining wall and on a side of the protected area away from a side wall of the experimental flume; the first retaining wall is in an L shape, the length of the first retaining wall extends to a front end of the protected area along a water flow direction, the width of the first retaining wall covers the width of the protected area and the width of the vegetation curtain wall, and the height of the first retaining wall is higher than the water surface, so that the water body cannot flow over the first retaining wall and directly flow into the protected area; the second retaining wall is located behind the vegetation curtain wall and on an extension line of the long side of the first retaining wall, so that the supersaturated TDG water flow cannot flow back to the protected area.

2. The experimental device for mitigating the adverse effects of TDG supersaturation in a riverine water body according to claim 1, wherein, The length of the vegetation curtain wall along the water flow direction is equal to the length of the protected area; and the height of the vegetation curtain wall is higher than the height of the water area of the protected area.

3. The experimental device for mitigating the adverse effects of TDG supersaturation in a riverine water body according to claim 1, wherein, The height of the second retaining wall is the same as that of the first retaining wall, and the length of the second retaining wall is greater than or equal to 2 m.

4. An experimental method for mitigating the adverse effects of TDG supersaturation in riverine waters, characterized in that, The experimental device is used to perform the following steps: (1) a plurality of hole bottom plates are prepared and placed on a beach of the experimental flume, and simulated vegetation is inserted on the hole bottom plates outside the protected area on the beach of the experimental flume, and the simulated vegetation is arranged in an interlaced manner; (2) a TDG supersaturated water generating device is started to inject TDG supersaturated water into the experimental flume; the flow rate is adjusted, the supersaturated TDG water flow fills the experimental flume, the water blocking device at the end of the experimental flume is adjusted to require that the water depth of the beach of the experimental flume is greater than or equal to 10 cm, and the water flow is stable; (3) after the water flow in the experimental flume is stable, a TDG measuring instrument is used to measure the TDG saturation values of the water bodies in and outside the protected area, and the experimental data are recorded; different flow rates, different inflow TDG saturation degrees and different simulated vegetation are changed, and steps (1) to (3) are repeated to obtain the change rule of the TDG saturation degree in the protected area under different conditions with the flow rate, the inflow TDG saturation degree and the type of the vegetation.

5. A method for mitigating the adverse effects of TDG supersaturation in a riverine water body, characterized by, The experimental device is used to perform the following steps:

6. The method of claim 5, wherein the method further comprises, (1) a plurality of hole bottom plates are prepared and placed on a beach of the experimental flume, and simulated vegetation is inserted on the hole bottom plates outside the protected area on the beach of the experimental flume, and the simulated vegetation is arranged in an interlaced manner; 7. The method of claim 5, wherein the method further comprises, (2) a TDG supersaturated water generating device is started to inject TDG supersaturated water into the experimental flume; the flow rate is adjusted, the supersaturated TDG water flow fills the experimental flume, the water blocking device at the end of the experimental flume is adjusted to require that the water depth of the beach of the experimental flume is greater than or equal to 10 cm, and the water flow is stable; (3) after the water flow in the experimental flume is stable, a TDG measuring instrument is used to measure the TDG saturation values of the water bodies in and outside the protected area, and the experimental data are recorded; different flow rates, different inflow TDG saturation degrees and different simulated vegetation are changed, and steps (1) to (3) are repeated to obtain the change rule of the TDG saturation degree in the protected area under different conditions with the flow rate, the inflow TDG saturation degree and the type of the vegetation.

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