Method for evaluating conditions for recovery of submerged plants and construction thereof

Abstract

The application discloses a kind of submerged plant recovery condition evaluation and its construction method, belong to environmental engineering technical field, steps are as follows: measure or estimate water surface illumination intensity and measure water transparency;Based on underwater light field calculation method obtains underwater light field information in recovery area;Whether it has recovery condition is evaluated in combination with plant population and community light compensation point data;For the area without condition, wind wave influence is evaluated using wind wave influence evaluation method on sediment, and combined with ecological enclosure, fish removal, bottom comprehensive improvement aid and microbial compound microbial agent measures, improve water transparency and other water quality conditions, complete submerged plant recovery.The application is simple, efficient, and the construction measures are scientific, reasonable, economical and convenient, which can effectively improve the survival rate of submerged plants.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental engineering, and particularly relates to a submerged plant recovery condition evaluation and a construction method thereof. BACKGROUND

[0002] Ecological restoration is an effective means to improve eutrophication and black odor problems and to improve the self-purification capacity of water bodies, and the restoration of submerged plant communities is a key link of ecological restoration. Submerged plants can reduce nutrient factors, control algae outbreaks, improve water transparency, optimize biological community structure, and provide living space for other organisms. Due to the problems of water body black odor, eutrophication, and siltation, the habitat is imbalanced, and the submerged plant community is seriously degraded. Therefore, in the comprehensive treatment of water environment and ecological restoration engineering, the restoration of submerged plant community is an important part.

[0003] At present, in the process of engineering practice, the restoration technology of submerged plants is relatively simple, and it is often simply regarded as crop planting. Through simple water depth control, it is estimated that the transparency is not less than 0.5 times the water depth, and then planting construction is carried out. A few construction processes consider the improvement measures of the substrate or are made into vegetation blankets to improve the survival rate of vegetation. However, in the actual construction process, the survival rate of vegetation is still low. The restoration engineering technology of submerged plants needs to be more scientific and meticulous in management and implementation.

[0004] Although the existing technology fully considers the survival conditions required by submerged plants, and selects suitable restoration areas, restoration species or makes more accurate water quality threshold determination, there are still limitations such as difficulty in on-site implementation, poor timeliness of data collection, complicated processing method, and some conditions are vague and have no actual guiding significance. For example, it is necessary to measure, fit and analyze the underwater light intensity and the transparency observation data. The suitable light intensity for submerged plants is not considered, and for the areas not suitable for restoration, the measures to construct suitable restoration conditions are not systematic and the cost is high. SUMMARY

[0005] The present application discloses a submerged plant recovery condition evaluation and construction method, which improves the success rate of submerged plant recovery by evaluating and constructing the underwater light conditions in the restoration area. The method includes an underwater light intensity calculation method, a submerged plant recovery critical condition evaluation, and a multi-factor water transparency comprehensive improvement method.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a submerged plant recovery condition evaluation and construction method, comprising the following steps:

[0007] S1, measuring or estimating the water surface light intensity;

[0008] S2, measuring the water transparency SD and calculating the underwater light intensity distribution:

[0009] LnI R = -2.25RSDe -0.335RSD

[0010] RSD is the relative transparency, i.e. the ratio of water depth to transparency; I R is the relative light intensity, i.e. the ratio of light intensity at depth h to the light intensity at the water surface. The relative light intensity is denoted as I.

[0011] S3, evaluate the submerged plant restoration condition, by comparing the light compensation point of the species and the light intensity of the water depth of the restoration area, evaluate whether the current meets the plant restoration condition: when Ih≥Ec, the submerged plant restoration condition of the species is met; when Ec≥Ih≥Ep, the restoration effect of the species is not good; when Ih≤Ep, the restoration area does not meet the restoration condition of the species;

[0012] S4, construct the submerged plant restoration condition, preferably restore the pioneer species with better light adaptation, and further improve the water transparency.

[0013] In the preferred scheme, in view of the problem of poor water transparency condition caused by wind wave factors, the influence of wind wave on the restoration area is evaluated through the wind wave shear stress formula and the sediment critical incipient stress formula, and the wind wave shear stress calculation formula is:

[0014]

[0015] Wherein, τ w is the wind wave shear stress; F is the fetch; h is the water depth; U is the wind speed. P1, P2, P3, P4 are coefficients;

[0016] The sediment critical incipient stress calculation formula is:

[0017]

[0018] Wherein, τ c is the critical shear stress of sediment; k is the incipient state coefficient; ρ, ρ s are the densities of water and sediment respectively; d is the median diameter of sediment; β w is the particle loosening coefficient under wave action; γ0 is the dry bulk density of bed surface sediment, γ0* is the stable dry bulk density of sediment particles; d' is the reference particle size; δ is the film water thickness parameter, which has the dimension of length. When τ w > τ c , the sediment is resuspended under the influence of wind wave; when τ w ≤ τ c , the sediment is not affected by the wind wave;

[0019] The fetch is changed by the above formula to optimize the layout of ecological enclosure, and then the disturbance of wind wave to sediment is weakened.

[0020] In the preferred scheme, the poor water transparency condition caused by fish factors is reduced by dense net driving, fishing or zoned rearing to reduce the influence of fish factors on the restoration of submerged plants.

[0021] In the preferred scheme, the water quality is improved by throwing bottom improvement agents and composite microbial agents in the shore shallow water area which is easily affected by wind and waves to improve water transparency, promote nutrient transformation and inhibit the release of phosphorus.

[0022] In the preferred scheme, the survival environment of vegetation can be further improved by optimizing the construction date during planting construction.

[0023] In the preferred scheme, the pioneer species with better adaptability to light conditions are selected for restoration.

[0024] In the preferred scheme, in order to characterize the light threshold of submerged plant restoration, by comparing the light compensation point of the species and the light intensity at the water depth of the restoration area, it can be evaluated whether the current meets the plant restoration conditions. When the light intensity at the water depth h of the restoration area is not less than the community light compensation point, the submerged plant restoration condition of the species is met; when the light intensity at the water depth h of the restoration area is not greater than the community light compensation point and not less than the light compensation point of the species, the species can survive but the restoration effect is poor; when the light intensity at the water depth h of the restoration area is not less than the light compensation point of the species, the restoration area does not meet the restoration condition of the species.

[0025] In the preferred scheme, the water surface light intensity of the restoration area is measured by a light intensity measuring instrument or estimated according to the current season and weather;

[0026] The water transparency is generally measured by a Secchi disc.

[0027] The present application has the following beneficial effects:

[0028] (1) The requirements of different submerged plant populations and communities for light conditions during the restoration process are fully considered, and an underwater light field calculation method is proposed, which does not require long sequence multi-point monitoring of underwater light field, long sequence field observation and complex data processing;

[0029] (2) A construction method of submerged plant restoration conditions under different factors is proposed, which comprehensively considers the influence of wind and wave, fish activity and water quality and other factors on the restoration of submerged plants, and proposes a simplified calculation method for evaluating the influence of wind and wave resuspension, which does not require wave instrument and ADCP flow meter, and is economical, simple, efficient. And a quantitative calculation method for inhibiting the influence of ecological enclosure on wind and wave is proposed, which can provide theoretical decision basis for the layout of ecological enclosure;

[0030] (3) The method proposed in the present application comprehensively uses ecological enclosure, comprehensive substrate modifier and composite microbial inoculant combination measures to improve water transparency and other water quality conditions, greatly reduces the range of pesticide application, reduces the potential environmental risk of pesticide use and reduces the cost of pesticide use, and significantly inhibits the effect of sediment resuspension caused by wind and wave, which can quickly achieve lake transparency and water quality improvement, and is conducive to the purpose of lake ecological restoration;

[0031] (4) The method can provide a reference for ecological restoration engineering and provide a theoretical decision basis for the design of lake in-situ pollution treatment (in-situ remediation or dredging) engineering. BRIEF DESCRIPTION OF DRAWINGS

[0032] The present application will be further described below in combination with the drawings and examples.

[0033] Figure 1 A step flow chart is provided for the method in the present application.

[0034] Figure 2 A verification diagram is provided for the underwater light intensity calculation method in the present application.

[0035] Figure 3 A verification diagram is provided for the wind wave shear stress simplified calculation method in the present application. DETAILED DESCRIPTION

[0036] In order to make the technical solutions of the present application clearer, the present application will be further described below in combination with the examples. The present application is specifically implemented according to the following steps:

[0037] Case area basic description: The water area of a certain lake in Wuhan is 222.58 hm2, the lake volume is 6.937 million m 3 , the average width is 535 m, the average water depth is 1.2 m, the maximum water depth is 2.2 m, and the minimum water depth is 0.47 m. The lake is not blocked by buildings on the windward side, so it is affected by wind and wave for a long time. The water level in the construction area is difficult to be lowered due to reasons such as flood control, drainage and landscape, and it is difficult to carry out precipitation construction. The water quality and sediment detection results show that the lake is a poor five-class water body, the main over-standard factor is total phosphorus, the degree of eutrophication is gradually deepening, the depth of polluted sediment is small, and the degree is relatively light, so the in-situ remediation technology is adopted to restore the water ecology of the lake area.

[0038] First step, design the light intensity evaluation of the restoration area:

[0039] (1) Measure or estimate the water surface light intensity I0.

[0040] The water surface light intensity is measured by light intensity meter or estimated according to the current season and weather. In this case, the water surface light intensity and underwater light intensity are measured by light meter, and the water surface light intensity in sunny, cloudy and rainy days is measured. The water surface light intensity is significantly affected by weather, and the measured data range is 5000-80000 Lux.

[0041] (2) Water transparency SD measurement

[0042] The water transparency is generally measured by Sechi disk. In this case, Sechi disk is used for transparency measurement. Before the implementation of the restoration measures, the water area with transparency less than 30 cm reached 100 hm2, close to half of the entire lake area.

[0043] (3) Calculation of underwater light intensity distribution

[0044] LnI R = -2.25RSDe -0.335RSD

[0045] Where h is the water depth, and Ih is the light intensity at water depth h. The formula is verified by using multiple measured data and previous research data, and the effect is good, see Figure (2).

[0046] The SD and water surface light intensity values are brought into the above formula to calculate the underwater light intensity at 2 times SD water depth, which is 500-8000 Lux.

[0047] Second step, evaluate whether the plant restoration conditions are met:

[0048] Design area plant light compensation point acquisition:

[0049] Different submerged plant species have different light compensation points (Ep), and the light compensation point will also change under different temperature conditions. The light compensation point reflects the adaptability of the species to the underwater light environment. When the light intensity reaches the light compensation point, the species can only survive and is difficult to form a community. Therefore, in order to characterize the light threshold of submerged plant restoration, the community light compensation point (Ec) of the species when it can form a stable community also needs to be considered. Through literature research, the light compensation point data of different plants under different temperatures are obtained. In the construction process of this case, the selected submerged plants are Vallisneria and Hydrilla verticillata. The light compensation point of Vallisneria is 100-400 Lux, and the light compensation point of Hydrilla verticillata is 900-1500 Lux.

[0050] Plant restoration condition evaluation:

[0051] By comparing the light compensation point of the species and the light intensity of the water depth of the recovery area, it can be evaluated whether the current plant recovery conditions are met. When Ih≥Ec, the submersed plant recovery conditions of the species are met; when Ec≥Ih≥Ep, the species can survive but the recovery effect is poor; when Ih≤Ep, the recovery area does not meet the recovery conditions of the species.

[0052] In this case, the Ec and Ep values of Vallisneria denseserrata are 100 Lux and 400 Lux respectively; the Ec and Ep values of Hydrilla verticillata are 900 Lux and 1500 Lux respectively. The SD before repair is 0.3 m, and the average water depth of the recovery area is 1.2 m, which does not meet the submersed plant recovery conditions. Calculation shows that when the transparency is restored to 0.5 times the water depth, i.e. 0.6 m, the underwater light intensity meets the 1500 Lux recovery threshold, and the water surface light intensity needs to reach 15000 Lux, which can only be achieved on sunny days.

[0053] Third step, construction of submersed plant recovery conditions

[0054] Preferred pioneer plants:

[0055] Different species have different adaptability to light, and the design of recovery plants can be adjusted according to the current water area light conditions. The pioneer species with better adaptability to light conditions are preferred for recovery, which can further improve water quality and thus improve transparency and improve the underwater light environment to meet the planting conditions of other species to be recovered.

[0056] In this case, under different water depth and transparency conditions, Potamogeton pusillus (60000 m2) and Potamogeton crispus (24000 m2) that can tolerate weak light conditions are added. Studies have shown that the allelopathy between different populations that adapt to weak light conditions can further reduce the light compensation point of the community, further improving the survival rate.

[0057] Preferred construction date:

[0058] In the current submersed plant recovery process, only the best planting season of plants or avoiding windy and rainy weather is considered, but for the underwater light environment, there is a significant difference between sunny and cloudy days, and the water surface light intensity can differ by more than 10 times. Therefore, the construction date can be optimized to further improve the plant survival environment.

[0059] Field measurements and experience in this case show that the water surface light intensity on sunny days ranges from 30000 to 80000 Lux, and the water surface light intensity on cloudy days ranges from 5000 to 8000 Lux. Therefore, during the critical period of submersed plant planting, it is necessary to avoid continuous rainy weather to avoid the underwater light intensity not meeting the plant survival threshold and causing the plant to be difficult to survive.

[0060] Improve water transparency:

[0061] The preferred pioneer plants and construction dates can improve the plant survival environment to a certain extent, but the improvement effect is limited. For the construction of submerged plant restoration conditions under general conditions, the underwater light intensity can be significantly improved by improving water transparency. Different measures need to be taken to improve transparency for different factors affecting transparency. The main factors affecting transparency include resuspension of sediment caused by wind and wave flow, disturbance of sediment by fish activity and other factors. Therefore, wind and wave factor improvement measures, fish factor improvement measures and other factor improvement measures are proposed respectively.

[0062] In this embodiment, the restoration area is long-term affected by wind and wave, fish activity and excessive total phosphorus, causing sediment resuspension and high concentration of blue-green algae, poor transparency conditions. Therefore, before the construction of submerged plants, engineering measures need to be taken to improve water transparency to meet the restoration conditions of submerged plants.

[0063] ①Wind and wave factor improvement measures:

[0064] The influence of sediment resuspension caused by wind and wave in shallow lakes on water transparency can reach more than 80%, and the disturbance of sediment by wind and wave also promotes the release of sediment nutrients, the upward germination of blue-green algae seeds and other negative effects. Therefore, when restoring submerged plants in shallow water, the influence of wind and wave on the restoration area needs to be considered. The following formula can be used for evaluation:

[0065] Wind and wave shear stress calculation formula:

[0066]

[0067] Where: τw is the wind and wave shear stress; F is the blowing range; h is the water depth; U is the wind speed. P1, P2, P3, P4 are coefficients, which are -1.48, 2.48*10-5, 3.84*10-1, 3.78*10-3 respectively. The fitting effect is shown in the attached figure (3).

[0068] Sediment critical incipient shear stress calculation formula:

[0069]

[0070] Where: τc is the critical shear stress of sediment; k is the incipient state coefficient, 0.128; ρ, ρs are the densities of water and sediment respectively; d is the median diameter of sediment; βw is the particle loosening coefficient under wave action; γ0 is the dry bulk density of bed sediment, γ0* is the stable dry bulk density of sediment particles; d, is the reference particle size, when d<0.5mm, take 0.5mm, when 0.5mm

[0071] When τw>τc, the sediment is resuspended by wind wave; when τw≤τc, the sediment is not affected by wind wave.

[0072] Therefore, the layout of ecological enclosure can be optimized by changing the fetch according to the above formula, so as to weaken the disturbance of wind wave to the sediment.

[0073] In order to evaluate the influence of wind on sediment in the restoration area, the wind field conditions near the lake area in recent years were counted. The results showed that the wind meteorological conditions in the lake area were mainly 3-4 levels, and the main wind direction was north. Specifically, the number of days of 3-level wind accounted for 70%, the number of days of 4-level wind accounted for 23%, and the number of days of 5-level and above accounted for 6%. And the number of days of the maximum fetch wind direction was more than half.

[0074] The sediment sampling and testing results in the restoration area showed that the sediment particle size distribution of different sampling points was consistent, which also proved that the wave action almost covered the restoration area. According to the international particle size classification standard: the proportion of clay particles (<0.002 mm) was 1.5%; the proportion of silt particles (0.002-0.02 mm) was 80.3%; the proportion of sand particles (0.02-2 mm) was 18.2%. Therefore, the lake sediment in the study area was mainly silt. The average median particle size d was about 0.008 mm.

[0075] The typical fetch of the lake area, the characteristics of the sediment, and the water depth of the restoration area were brought into the calculation to obtain the critical wind speed of the restoration area, which was about 5 m / s, while the typical wind speed of the lake area was 6.5 m / s, so the wind wave effect was significant. The research showed that the setting of ecological enclosure inhibited the wave absorption of wind energy and the continuous growth of wave, and the wave transmission rate reduction coefficient reached 80-90%, so the fetch of the wind area could be changed by the layout of ecological enclosure, and then the influence of wind wave on sediment could be reduced. The calculation and measurement showed that the fetch of the ecological enclosure area after division was reduced to 500 m, which could significantly improve the resuspension of sediment caused by wind wave. Considering the flexibility of ecological enclosure and the boundary shape of the lake area, the effective fetch of the actual ecological enclosure division area was set to 400 m.

[0076] Table 1 Calculation results of critical incipient shear stress and critical wind speed of a certain lake

[0077] Table 1 Calculation results of critical incipient shear stress and critical wind speed of a certain lake

[0078]

[0079] ② Fish factor improvement measures:

[0080] Fish grazing and activity can affect plant germination and root growth, and disturb sediment, thereby reducing the survival rate of vegetation. The influence of fish factors on submersed plant restoration can be reduced by means of dense net driving, fishing, and zoned enclosure, etc.

[0081] In this case, fish in the recovery area are removed by fish attractors and gill nets, and ecological enclosures are laid out in different zones. After zoning, silk nets are used to further remove fish. Ground cages are set up to monitor and control the population and quantity of fish in the recovery period.

[0082] ③ Other factors for improvement measures.

[0083] ① The impact of wind and waves on sediments, especially in the coastal shallow water area, is introduced. The resuspension of sediments in this area will exacerbate the release of internal source pollution and spread with the flow, affecting water transparency and promoting the aggregation and outbreak of blue-green algae. By throwing bottom modifier and composite microbial agent in the coastal shallow water area susceptible to wind and waves, the water transparency is improved, the nutrient transformation is promoted, and the release of phosphorus is inhibited, thus improving water quality and increasing the survival rate of vegetation in the recovery area.

[0084] In this implementation case, the coastal zone is significantly affected by wind and waves, and it is difficult to further reduce the impact of wind and waves through enclosure measures. In addition, the total phosphorus concentration in the sediment and water in this area is high, and the concentration of blue-green algae reaches moderate eutrophication. The main area affected by wind and waves in the recovery area is calculated by formula (2) after the implementation of the enclosure, and bottom modifier and composite microbial agent are thrown in this area to reduce the release of phosphorus in the sediment and promote the adsorption and degradation of total phosphorus in the water, while reducing the concentration of blue-green algae and suspended solids, and improving water transparency. After the measures, the water transparency is significantly improved, reaching 60-80 cm, and the total phosphorus concentration and blue-green algae concentration in the water continue to decrease, forming a virtuous cycle of lake water ecological restoration, restoring more than 1.5 million m2 of submerged plants, and the recovery area reaching 70% of the lake area. The following table shows the parameters of the lake shore sediment improvement aid and microbial agent

[0085] Table 2 Parameters of Lake Shore Sediment Improvement Aid and Microbial Agent

[0086]

[0087] Fourth step, submerged plant community construction

[0088] After the implementation of the transparency improvement combination measures, the water transparency and water quality conditions are significantly improved, meeting the requirements for submerged plant restoration, and submerged plant community construction can be implemented. After artificial submerged plant community construction, the lake water quality is further improved, and the restored submerged plants can also play an important role in wind wave suppression, forming a virtuous cycle of lake water quality restoration.

[0089] Implementation effect:

[0090] Through the combination of ecological enclosure, complex microbial inoculants and comprehensive substrate amendment, the influence of sediment wind and wave disturbance on the water quality and water ecological restoration project implementation in the case lake area was effectively reduced, the lake health status indexes such as water transparency and dissolved oxygen were improved, and the nutrient salt indexes such as total phosphorus and ammonia nitrogen in the lake were also effectively reduced. For example, before the implementation of the measures, under normal wind and wave conditions, the water area with transparency less than 30 cm reached 1 million m2. After the implementation of the comprehensive measures, the water transparency was significantly improved to 60-80 cm, basically meeting the conditions for the survival of SD≥h / 2 vegetation. More than 1.5 million m2 of submerged plant planting area was successfully restored, accounting for 70% of the lake area. With the restoration of the lake water ecology, the overall improvement of the lake water body was further promoted, laying a good foundation for achieving the Class IV water standard of the lake.

[0091] The above embodiments are only preferred technical solutions of the present application, and should not be regarded as a limitation of the present application. The protection scope of the present application should be based on the technical solutions recited in the claims, including equivalent replacement solutions of the technical features recited in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present application.

Claims

1. An assessment method for the restoration conditions of submerged plants and its construction method, characterized in that... Includes the following steps: S1. Measure or estimate the light intensity on the water surface; S2. Measurement of water transparency (SD) and calculation of underwater light intensity distribution: RSD stands for Relative Transparency, which is the ratio of water depth to transparency. R Relative light intensity is the ratio of the light intensity at depth h to the light intensity at the water surface. S3. Assess the conditions for submerged plant recovery by comparing the light compensation point of the species with the light intensity at the water depth of the recovery area to determine whether the current conditions for plant recovery are met: When Ih≥Ec, the submerged plant recovery condition of the species is met; When Ec≥Ih≥Ep, the species recovery effect is poor; When Ih≤Ep, the recovery zone does not meet the species recovery condition; Where Ep is the species light compensation point, Ec is the community light compensation point, and Ih is the light intensity at a water depth of h. S4. Construct conditions for the restoration of submerged plants, restore pioneer species that are better adapted to light conditions, and further improve water transparency; To address the issue of poor water transparency caused by wind and waves, the impact of wind and waves on the recovery zone is assessed using the wind and wave shear stress formula and the sediment critical initiation stress formula. The wind and wave shear stress calculation formula is as follows: Where, τ w For wind and wave shear stress; F is the wind direction; h is the water depth; U is the wind speed; P1, P2, P3, and P4 are coefficients. Formula for calculating critical initiation stress in sediments: Where, τ c ρ is the critical shear stress of the sediment; k is the initiation state coefficient; ρ, ρ s These represent the densities of water and sediment, respectively; d is the median grain size of the sediment; β w The particle loosening coefficient under wave action; γ0 is the dry bulk density of the bed surface sediment, γ0* is the stable dry bulk density of the sediment particles; d` is the reference particle size; δ is the film water thickness parameter, which has the dimension of length, when τ w >τ c At that time, sediments are resuspended due to the influence of wind and waves; when τ w ≤τ c At that time, the sediments were unaffected by wind and waves; By changing the blowing path using the above formula, the layout of ecological barriers can be optimized, thereby reducing the disturbance effect of wind and waves on sediments.

2. The method for assessing and constructing conditions for the restoration of submerged plants according to claim 1, characterized in that: To address the issue of poor water transparency caused by fish, methods such as dense netting, fishing, or enclosed rearing can be used to reduce the impact of fish on the recovery of submerged plants.

3. The method for assessing and constructing conditions for the restoration of submerged plants according to claim 1, characterized in that: Water quality is improved by applying bottom sediment improvers and compound microbial agents to shallow coastal waters that are susceptible to wind and waves, thereby enhancing water transparency, promoting nutrient conversion, and inhibiting phosphorus release.

4. The method for assessing and constructing conditions for the restoration of submerged plants according to claim 1, characterized in that: By optimizing the planting schedule, the living environment of vegetation can be further improved.

5. The method for assessing and constructing conditions for the restoration of submerged plants according to claim 1, characterized in that: To characterize the light threshold for submerged plants to recover, the light intensity at the light compensation point of a species and the water depth of the recovery zone was compared to assess whether the current conditions for plant recovery were met. When the light intensity at a water depth of h in the restoration area is not less than the community light compensation point, the restoration conditions for this submerged plant species are met. When the light intensity at a water depth of h in the restoration area is not greater than the community light compensation point and not less than the species light compensation point, the species can survive but the restoration effect is poor. When the light intensity at a water depth of h in the restoration zone is not less than the species' light compensation point, the restoration zone does not meet the restoration conditions for that species.

6. The method for assessing and constructing conditions for the restoration of submerged plants according to claim 1, characterized in that: The light intensity of the water surface in the restoration area is measured using a light intensity meter or estimated based on the current season and weather. Water transparency was measured using a Sechs disk.

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