Ecological restoration method for slow-flowing river channel

Abstract

The application discloses a slow-flowing river ecological restoration method, and relates to the technical field of river restoration.The method comprises the following steps: 1) preparing an ecological restoration carrier; 2) determining the ecological suitability of river bottom sludge; 3) dividing the river into different regions; and 4) restoring the ecology of the river.The present application divides the slow-flowing river with mild pollution into different regions according to the survival rates of aquatic plants, and uses different ecological management schemes accordingly.The survival rate of the seedlings of submerged plants in the slow-flowing river section after management is significantly improved, and about 60% of the riverbed is covered by the submerged plants.

Description

Technical Field

[0001] This invention relates to the field of river restoration technology, and more specifically to a method for ecological restoration of slow-flowing river channels. Background Technology

[0002] River channels are comprehensive and complex ecosystems encompassing land, flora and fauna, and water bodies. They possess crucial functions such as regulating water flow, storing water volume, purifying water quality to remove harmful substances, and providing habitats for aquatic and terrestrial organisms. Their vegetation is significantly distinct from the banks, exhibiting a high degree of biodiversity. Specifically, in slow-flowing river channels, silt pollution primarily originates from the deposition of pollutants in the water. Due to differences in flow velocity, sediment concentration gradually increases from the center of the river channel towards both banks, exhibiting a distribution pattern of low concentration in the center and high concentration at the banks.

[0003] The current engineering dredging methods are not suitable for rivers with moderate to light pollution. They are not only costly, but also seriously interfere with the natural ecological functions of the river, leading to a series of problems such as the river's ecological environment becoming more homogenous, the lack of aquatic vegetation, the breakage of the surrounding ecological chain, the decline in biodiversity, and the weakening of the river's self-purification capacity.

[0004] As a core technology in ecological restoration engineering, the planting and restoration of submerged plants has significant effects on the treatment, regulation, and inhibition of eutrophication of water bodies and sediments. Submerged plants, with their massive biomass, engage in frequent material and energy exchanges with the environment, creating a vast environmental capacity and a powerful natural purification system. These plants live in water throughout their entire life cycle, and their roots, stems, and leaves effectively absorb nutrients from the water; their growth process is essentially a continuous absorption of nutrients from the water. Furthermore, the microorganisms attached to the rhizosphere of submerged plants can degrade organic pollutants, thereby continuously improving water quality and promoting the ecological restoration of sediments.

[0005] Therefore, providing a method for ecological restoration of slow-flowing rivers with moderate to mild pollution using submerged plants is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for ecological restoration of slow-flowing rivers.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for ecological restoration of slow-flowing rivers includes the following steps:

[0009] 1) Preparation of ecological restoration carriers:

[0010] Silt from the bottom of clean water bodies is taken, wrapped in biodegradable non-woven fabric to form a spherical carrier, and holes are evenly punched in the hemisphere to plant submerged plant seedlings, thus preparing an ecological restoration carrier.

[0011] 2) Determination of the ecological suitability of riverbed silt:

[0012] Place the ecological restoration carriers into the river channel, along the vertical direction of the river centerline, at 10m intervals; and count the growth of aquatic plants after 7 days.

[0013] 3) River channel zoning;

[0014] Based on the SR (survival rate) statistics of aquatic plants, the river channel was divided into zones, with the placement point of the ecological restoration carrier as the midpoint of each zone, and a width of 10m.

[0015] S1: Drop-off points with SR ≤ 25% from the riverbank to the side closest to the riverbank;

[0016] S2: 25% < SR ≤ 50% of the application points;

[0017] S3: Placement points where 50% < SR;

[0018] S4: Drop-off points with SR≤25% on the side closest to the river centerline are located to the river centerline;

[0019] 4) River ecological restoration:

[0020] The silt covering material is evenly placed in the S1 area, followed by the placement of the ecological restoration carrier.

[0021] Ecological restoration carriers were deployed within the S2 area;

[0022] Submerged plant seedlings are directly placed in the S3 area.

[0023] Furthermore, the spherical carrier has a diameter of 8-12cm, and the number of submerged plant seedlings planted is 8-10.

[0024] Furthermore, in step 2), the ecological restoration carrier is bound with a fishing line before deployment, and the fishing line is connected to a floating ball for positioning on the water surface.

[0025] Furthermore, the submerged plant seedlings are:

[0026] Vallisneria, or any one or more of the following: Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum.

[0027] Furthermore, the composition of the silt covering material described in step 4), in parts by mass:

[0028] 50 parts activated carbon sludge, 10 parts zeolite, and 5 parts calcium peroxide;

[0029] The thickness of the silt covering material is 10-20cm.

[0030] Furthermore, in step 4), groynes are constructed within the S1 area, and silt covering material is placed between the groynes.

[0031] Furthermore, in step 4), the density of the ecological restoration carriers is 5 carriers / m². 2 ;

[0032] The direct planting density of the submerged plant seedlings is 50-100 plants / m². 2 ;

[0033] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention addresses the varying survival rates of aquatic plants in slow-flowing rivers with moderate to mild pollution by employing different targeted treatment methods.

[0035] Area S1 is close to the riverbank, with shallow water, ample sunlight, and good aquatic plant growth, which can more effectively remove pollutants. The disadvantage is the slow flow rate, which makes pollutants more prone to sedimentation, resulting in excessively high pollutant concentrations in the bottom silt. To address this issue without resorting to engineering dredging, this invention utilizes a silt-covering material. This material also isolates the riverbed silt with excessively high pollutant concentrations, allowing aquatic plants to grow normally and process continuously accumulating new pollutants.

[0036] Constructing groynes within the S1 area can further slow down the water flow, slightly increase the sedimentation rate of pollutants within the groyne area, and facilitate the treatment of pollution by transplanted aquatic plants. Groynes can also constrict water flow, increasing the water flow velocity in the river's centerline area and reducing the pollutant deposition rate in the central river channel.

[0037] The ecological restoration carrier contains unpolluted sludge taken from clean water bodies, ensuring the survival of aquatic plants in areas S1 and S2. In area S3, where light conditions and sludge pollutant concentrations are balanced, the survival rate of aquatic plants exceeds 50%, allowing for the direct introduction of submerged plant seedlings for ecological restoration.

[0038] The survival rate of submerged plant seedlings in the slow-flowing river section treated by this invention was significantly improved, reaching 76.7-80% in area S1, 56.6-70% in area S2, and 83.3-86.7% in area S3. Underwater observation revealed that approximately 60% of the riverbed in the slow-flowing section was covered by submerged plants. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 within the scope of protection of the present invention.

[0040] Example 1

[0041] A method for ecological restoration of slow-flowing rivers includes the following steps:

[0042] 1) Preparation of ecological restoration carriers:

[0043] Take silt from the bottom of clean water bodies, wrap it with biodegradable non-woven fabric to form a spherical carrier with a diameter of 10cm, make 10 holes evenly on the hemisphere, plant aquatic plant seedlings in each hole, and prepare an ecological restoration carrier.

[0044] The aquatic plant seedlings were all selected from submerged plants, including Vallisneria natans, Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum.

[0045] 2) Determination of the ecological suitability of riverbed silt:

[0046] A restoration experiment was conducted on a slow-flowing section of a river in Guangdong Province. The average width of the river in the test section was 146m. Starting from the west bank of the river, ecological restoration carriers were placed into the river. Along the vertical direction of the river centerline, 8 ecological restoration carriers (2 each of Vallisneria natans, Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum) were placed every 10m, for a total of 14 placements. Before placement, the ecological restoration carriers were tied to fishing lines, and the fishing lines were connected to floating balls for water surface positioning (if the water flow was rapid, the fishing lines could also be tied to heavy objects such as bricks to fix the floating balls).

[0047] The experiment was repeated at locations 50m and 100m downstream of the initial placement point;

[0048] Seven days later, the growth of aquatic plants was recorded. Starting from the west bank of the river, the average survival rate of aquatic plants at different distances from the release points was recorded. The results are shown in Table 1.

[0049] Table 1. Average survival rate of submerged plant seedlings at different drop-off points.

[0050]

[0051] Table 1 shows that the survival rate of aquatic plants initially increases and then decreases from the riverbank to the river centerline. Near the riverbank, the water flow is slower, leading to easier sedimentation of pollutants and higher pollutant concentrations in the riverbank silt, thus reducing the survival rate of submerged plant seedlings. As the flow approaches the river centerline, the water flow increases, pollutant deposition decreases, and the survival rate of submerged plant seedlings increases. Near the river centerline, the water flow is highest, pollutant deposition is lowest, and the water is correspondingly deepest, resulting in insufficient light for submerged plant seedlings and a decreased survival rate.

[0052] The river is divided into zones based on the degree of pollution of the silt at the bottom of slow-flowing rivers.

[0053] 3) River channel zoning;

[0054] Based on the SR (survival rate) statistics of aquatic plants, the river channel was divided into zones, with the placement point of the ecological restoration carrier as the midpoint of each zone, and a width of 10m.

[0055] S1: Drop-off points with SR ≤ 25% from the riverbank to the side closest to the riverbank;

[0056] S2: 25% < SR ≤ 50% of the application points;

[0057] S3: Placement points where 50% < SR;

[0058] S4: Drop-off points with SR≤25% on the side closest to the river centerline are located to the river centerline.

[0059] Table 2. Classification of treatment areas at different distances from application points.

[0060]

[0061] Note: The leftmost S1 area extends to the west bank of the river, and the rightmost S1 area extends to the east bank of the river.

[0062] 4) River ecological restoration:

[0063] Construct groynes within area S1, and place silt cover material between the groynes. The silt cover material, by weight, consists of 50 parts activated carbon silt, 10 parts zeolite, and 5 parts calcium peroxide. Mix thoroughly and apply evenly to a thickness of 15 cm. Then, add ecological restoration carriers at a density of 5 carriers / m². 2 (Vallisneria natans, Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum are randomly mixed in equal amounts);

[0064] Ecological restoration carriers were placed in the S2 area at a density of 5 carriers / m². 2 (Vallisneria natans, Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum are randomly mixed in equal amounts);

[0065] Submerged plant seedlings were directly placed in the S3 area at a density of 50 seedlings / m². 2 .

[0066] When directly releasing the seedlings, dig them out of the cultivation mud, keeping the mud around their roots. Gently hold them in place by hand to make them sink quickly after being placed in the water.

[0067] Twelve months after ecological restoration, the ecological suitability of the riverbed silt in the restored river section was determined. Ten ecological carriers were randomly placed in different zones, secured with fishing lines and floating balls for positioning. The carriers were repeatedly placed 50m and 100m downstream of the initial placement location. The average survival rate was calculated after 7 days. The results are shown in Table 3.

[0068] Table 3. Average survival rate of submerged plant seedlings in different zones

[0069] partition S1 S2 S3 S2 S3 S2 S1 Average survival rate (%) 76.7 70.0 83.3 56.6 86.7 66.7 80.0

[0070] Table 3 shows that after 12 months of treatment, the survival rate of submerged plant seedlings in the slow-flowing river section significantly improved, reaching 76.7-80% in area S1, 56.6-70% in area S2, and 83.3-86.7% in area S3. Underwater observation revealed that approximately 60% of the riverbed in the slow-flowing section was covered by submerged plants.

[0071] Water quality testing showed that the pH value of the water in the slow-flowing river restoration area increased from 6.2 to 6.9, changing from slightly acidic to slightly neutral water. The removal rate of organic matter in the water reached 45%, the turbidity decreased significantly, the water transparency increased from 0.9m to 1.3m, the dissolved oxygen concentration increased from 1.41mg / kg to 2.23mg / kg, the total nitrogen removal rate reached 18%, and the total phosphorus removal rate reached 32%, indicating a significant improvement in water pollution.

[0072] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for ecological restoration of slow-flowing rivers, characterized in that, Includes the following steps: 1) Preparation of ecological restoration carriers: Silt from the bottom of clean water bodies is taken, wrapped in biodegradable non-woven fabric to form a spherical carrier, and holes are evenly punched in the hemisphere to plant submerged plant seedlings, thus preparing an ecological restoration carrier. 2) Determination of the ecological suitability of riverbed silt: Place the ecological restoration carriers into the river channel, along the vertical direction of the river centerline, at 10m intervals; and count the growth of aquatic plants after 7 days. 3) River channel zoning; Based on the statistical results of the survival rate (SR) of submerged plant seedlings, the river channel was divided into zones, with the placement point of the ecological restoration carrier as the midpoint of each zone, and a width of 10m. S1: Drop-off points with an SR ≤ 25% from the riverbank to the side closest to the riverbank; S2: 25% < SR ≤ 50% of delivery points; S3: Placement points where 50% < SR; S4: Drop-off points with SR≤25% on the side closest to the river centerline are located to the river centerline; 4) River ecological restoration: Within the S1 area, groynes are constructed, and silt covering material is evenly distributed within the groynes, followed by the distribution of ecological restoration carriers. Ecological restoration carriers were deployed within the S2 area; Submerged plant seedlings were directly placed in the S3 area; Step 4) The composition of the silt covering material, in parts by weight: 50 parts activated carbon sludge, 10 parts zeolite, and 5 parts calcium peroxide; The thickness of the silt covering material is 10-20cm; Step 4) The placement density of the ecological restoration carrier is 5 carriers / m². 2 ; The direct planting density of the submerged plant seedlings is 50-100 plants / m². 2 .

2. The method for ecological restoration of slow-flowing rivers according to claim 1, characterized in that, The spherical carrier has a diameter of 8-12cm, and the number of submerged plant seedlings planted is 8-10.

3. The method for ecological restoration of slow-flowing rivers according to claim 1, characterized in that, Step 2) The ecological restoration carrier is bound with a fishing line before deployment, and the fishing line is connected to a floating ball for positioning on the water surface.

4. The method for ecological restoration of slow-flowing rivers according to claim 1, characterized in that, The submerged plant seedlings are: Any one or more of the following: Vallisneria natans, Ceratophyllum demersum, Hydrilla verticillata, and Myriophyllum spicatum.

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