River network type water system ecological system restoration method

Abstract

The embodiment of the invention relates to a method for restoring a river network type water system ecosystem, which comprises the following steps of: introducing aquatic plant varieties for improving a water environment into nodes and areas which have great influence on water quality in a river network type water system to be restored, so as to form a water quality control type plant framework which stably grows and propagates within 1-3 months; sediment is collected in the river network type water system to be repaired, and species with potential germination ability and density of the species in the propagule bank of the water system are evaluated; supplementing a propagule library: supplementing species lacking propagule resources in the river network type water system to be repaired according to an evaluation result; in the repaired water area with the aquatic plant community growing stably and the water body penetration depth ratio stably kept to be larger than or equal to 0.5, associated plants beneficial to water quality improvement and aquatic plant community stability continue to be introduced. The ecological system has the advantages of being low in construction cost, high in anti-interference performance and excellent in self-maintaining capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological restoration, and in particular to a method for restoring a river network type water system ecosystem. Background Art

[0002] Due to the natural flow of water bodies, frequent water level fluctuations, and severe eutrophication, river network water systems usually show low water transparency, prone to blue algae blooms, and fewer aquatic plants and benthic populations. Common river water ecological restoration technologies usually include a large number of engineering measures, such as external pollution interception, internal dredging, artificial oxygenation, damming at both ends to intercept water flow, and planting a large number of aquatic plant seedlings inside.

[0003] The above-mentioned river network water system ecological restoration technologies have the following problems: measures such as damming cut off the natural connectivity of the river; large-scale transplantation of plants with fewer species forms a simple plant community, and the restored ecosystem has poor stability, and sometimes even requires the use of chemical agents to adjust water to maintain the system, which makes overall operation and maintenance difficult and costly; in large-scale river network water system ecological restoration, it is even more impossible to achieve the goals of natural and sustainable restoration. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for repairing a river network type water system ecosystem, which solves the technical problems existing in the restoration of the existing river network type water system ecosystem, such as poor system stability, great difficulty in operation and maintenance, high operation and maintenance costs, and inability to achieve natural and sustainable recovery of the river network type water system ecosystem.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, an embodiment of the present invention provides a method for repairing a river network water system ecosystem, comprising the following steps:

[0009] S1. Construct a water quality control plant framework: Introduce aquatic plant species that improve the water environment into the nodes and areas with greater impact on water quality in the river network to be restored, so as to form a water quality control plant framework with stable growth and expansion within 1-3 months. The nodes and areas with greater impact on water quality include river mouths, places where pollution is concentrated, water confluences, water areas with bottom redox potential <80mV, and water areas with water penetration-depth ratio less than 0.5;

[0010] S2. Assessment of propagule pool activity: Collect sediments in the river network to be restored and assess the species with potential germination capacity and their density in the propagule pool of the water system;

[0011] S3. Replenishment of propagule pool: Based on the evaluation results of S2, species lacking propagule resources in the river network to be restored are supplemented to enable them to germinate and grow to form supplementary communities; species lacking propagule resources are species with a potential germination density of less than 20 plants / m 2 of plant species;

[0012] S4. Improve biodiversity: In restored waters where the growth of aquatic plant communities is stable and the water depth ratio is kept stable at ≥ 0.5, continue to introduce companion plants that help improve water quality and stabilize aquatic plant communities.

[0013] As a preferred embodiment of the present invention, in the river network water system ecosystem restoration method, in S1, the water quality control plant framework also includes introducing submerged plants with strong water purification function in the water area where aquatic plants cannot be directly colonized and survived in the river network water system to be restored through an ecological hanging bed;

[0014] Water areas where aquatic plants cannot directly colonize and survive are areas that meet at least one of the following conditions: the water penetration-depth ratio is less than 0.5, the water flow velocity is greater than or equal to 0.1m / s, and the bottom sediment redox potential is less than 80mV.

[0015] As a preferred embodiment of the present invention, in the river network water system restoration method, in S3, the introduced propagules are disinfected, screened and pre-treated with 0.1-5mmol / L salicylic acid solution before being submerged; propagules of different species are mixed and sown. This part of the propagules includes seeds and propagules with buds, or one of the two.

[0016] As a preferred embodiment of the present invention, the river network type water system ecosystem restoration method, in S1, selects the water area outside the water quality control type plant framework water area in the river network type water system to be restored, and the water body depth ratio is stably maintained at ≥0.5 and the bottom sediment redox potential is ≥80mV to build a water area framework prior plant community.

[0017] Among them, the pioneer plant community can be constructed in the waters with a depth of ≤2m near the shore of the river network water system to be restored. The pioneer plant community includes the nearshore area community and the middle river area community. The nearshore area community is a perennial species with stable biomass, and the middle river area community is a pollution-tolerant species;

[0018] As a preferred embodiment of the present invention, the river network type water system ecosystem restoration method adopts a patch-like arrangement to supplement the introduction of companion plants and leading plant communities.

[0019] Among them, the leading plant community adopts discontinuous patch layout, with a patch area of ​​300-500m 2The distance between patches is 150-500m. The area of ​​each patch of companion plants is 30m 2 More than one plant species is set in each patch, and the distance between patches is 10m.

[0020] As a preferred embodiment of the present invention, the river network water system ecosystem restoration method described above reduces the herbivorous and omnivorous fish populations before introducing aquatic plants into the river network water system to be restored;

[0021] After step S1, introduce benthic animals: After the water quality control plant framework community is stabilized, conduct a resource survey and assessment of the benthic animal community within the water system restoration area, and set biomass targets for different groups: Among them, the biomass targets for snails and shellfish are 15-20g / m 2 Shrimp will be supplemented according to the biomass target of 0.2-0.3kg / mu to guide the healthy and stable recovery of the population.

[0022] As a preferred embodiment of the present invention, the river network type water system ecosystem restoration method further includes S5, harvesting management: before the aquatic plant community in the river network type water system to be restored reaches stability, branches of dominant species are manually harvested, and high-intensity harvesting is avoided during the flowering and fruiting period and the winter bud period.

[0023] As a preferred embodiment of the present invention, in the river network type water system ecosystem restoration method, in S1, the submerged plants with strong water purification function include one or more of duckweed, black algae, spike foxtail algae, Vallisneria and giant hydrilla.

[0024] (III) Beneficial effects

[0025] The beneficial effects of the present invention are as follows: a method for repairing a river network-type water system ecosystem of the present invention, in the early stage of repair, gives priority to introducing aquatic plant varieties with strong ability to improve the water environment at nodes and areas that have a greater impact on the water quality of the repair area, including river mouths, places where pollution is concentrated, water flow intersections, water areas with heavy bottom pollution and low water penetration ratio, so as to quickly form a community that can grow and multiply stably, thereby reducing the input of external pollution, and also playing a role in slowing down the flow of river water, playing the role of the first barrier for the subsequent construction of the ecosystem.

[0026] At the same time, through the evaluation of the activity of the propagule pool, plants with low propagule density are supplemented in a targeted manner to restore and improve the propagule pool of the river network water system and form a supplementary plant community. After the growth of the aquatic plant community in the repaired water area is stable and the transparency of the water body is significantly improved and stabilized, companion plants that contribute to the stability of water quality and community are continuously introduced to improve the species diversity and stability of the system. The construction of water quality control plants, the supplementation of propagules and the introduction of companion plants are coordinated to eventually form an aquatic ecosystem with high species diversity and strong system stability in the river network water system to be repaired. Compared with the existing technology, this restoration method constructs a multi-level ecological niche aquatic plant framework to improve the transparency of the river network water body, and at the same time promotes the self-recovery process of the river network water system with the help of natural recovery ability. The ecosystem has the characteristics of low construction cost, strong anti-interference and excellent self-sustaining ability, providing a more efficient and sustainable solution for the ecological restoration of the river network water system.

[0027] In the construction of the water quality control plant framework, when the water depth ratio of the river network type water system to be repaired is poor, the water flow intensity is strong, the bottom environment is harsh and / or the water area is affected by pollution sources and is not sufficient for direct colonization and survival, ecological suspended beds are used to plant submerged plants. These submerged plants are planted in underwater suspended beds to extend their growth to the lower layer of the water body, promoting the submerged plants to absorb suspended matter and dissolved nutrients in the water, while improving the photosynthesis efficiency of the plants.

[0028] In the river network water system to be restored, except for the water quality control plant framework water area, the water body penetration depth ratio and bottom physical and chemical conditions that meet the requirements for direct planting and survival, that is, the area with relatively good water environment, are selected to build the advance plant community. The construction of the advance plant community further supplements the vegetation coverage of the water area and improves the water environment on the basis of the water quality control plant framework.

[0029] The advance plant community adopts an intermittent patch arrangement, which reduces the cost of restoration; the areas between patches are reserved for subsequent propagule banks, forming a multi-level ecological pattern to cope with sudden changes in water conditions and improve the natural adaptability of water bodies.

[0030] Supplement the propagules of submerged plants with good propagation performance suitable for artificial introduction, including winter buds of Hydrillaverticillata, seeds of Vallisneria natans and seeds of Najas marina. According to the evaluation results, for plants with low propagule resource quantity and potential germination rate, corresponding propagules are introduced. Before the introduction of the propagules, they are disinfected, screened and pre-treated with 0.1-5mmol / L salicylic acid solution to improve their survival rate and germination ability. Different propagules are mixed and sown to improve the efficiency of interspecific competition, thereby achieving an increase in the species diversity of the community.

[0031] The patch layout is used to introduce companion plants. Due to the high spatial heterogeneity, the patch layout community can cope with environmental fluctuations and disturbances (such as water level fluctuations, changes in nutrient concentrations, etc.). Different plants have different adaptability to the environment, and the patch structure can improve the overall community's resistance to adverse environmental conditions.

[0032] More than one plant species, generally 3-5 species, is set in each patch of functional plants; the spacing between patches is determined according to the existing plant distribution pattern, with the principle of fully promoting the interaction and material exchange between communities. Different plant combinations can be configured for different water depth areas, which is flexible and versatile.

[0033] Before introducing aquatic plants into the river network to be restored, reduce the herbivorous and omnivorous fish populations to ensure the coverage of aquatic plants.

[0034] After the water quality control plant framework is constructed, benthic animals are introduced: After the water quality control plant framework community is stabilized, a resource survey and assessment of the benthic animal community within the water system restoration area is conducted, and biomass targets are set for different groups: Among them, the biomass targets for snails and shellfish are 15-20g / m 2 Shrimp are supplemented according to the biomass target of 0.2-0.3kg / mu to guide the healthy and stable recovery of the population. The activities of benthic animals can enhance the oxidation of the bottom of the water, prevent the deposition of organic matter, and reduce the formation of anaerobic environment, thereby effectively improving the bottom environment and providing better basic conditions for subsequent ecological restoration.

[0035] Harvest management: Before the plant community in the river network to be restored reaches stability, manually harvest the branches of dominant species to interfere with the dominant species and improve the species diversity of the community. Avoid high-intensity harvesting during the flowering and fruiting period and winter bud period to facilitate the subsequent generation of seeds and propagules. DETAILED DESCRIPTION

[0036] In order to better explain the present invention and facilitate understanding, the present invention is described in detail through specific implementation methods.

[0037] A method for repairing a river network water system ecosystem proposed in an embodiment of the present invention is aimed at the technical problems of poor system stability, great difficulty in operation and maintenance, high operation and maintenance costs, and inability to achieve natural and sustainable restoration of river network water system ecosystems in the existing river network water system ecosystem repair. In the early stage of repair, priority is given to introducing aquatic plants with strong ability to improve the water environment in the nodes and areas that have a greater impact on the water quality of the repair area in the river network water system to be repaired, including river mouths, places where pollution is concentrated, water confluences, water bodies with heavy bottom pollution, and waters with low water penetration depth ratio, to construct a water quality control plant framework, quickly form a stable plant community, reduce the input of external pollution, and slow down the flow of river water, playing the role of the first barrier for the subsequent construction of the ecosystem.

[0038] At the same time, the propagule pool activity assessment is used to supplement the propagules of species with insufficient propagule resources, restore and improve the propagule pool of the river network water system, and form a supplementary plant community. Then, by introducing companion plants, the species diversity and system stability of the aquatic plant community can be further improved. The supplementation of propagules and the supplementation and expansion of companion plants are coordinated to eventually form a stable aquatic plant community in the river network water system to be repaired. Compared with the existing technology, this restoration method constructs a multi-level ecological niche aquatic plant framework, realizes the improvement of the transparency of river network water bodies, and at the same time promotes the self-recovery of the river network water system with the help of natural recovery ability. The ecosystem has the characteristics of low cost of construction, strong anti-interference and excellent self-sustaining ability, providing a more efficient and sustainable solution for the ecological restoration of river network water systems.

[0039] In order to better understand the above technical scheme, exemplary embodiments of the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a clearer and more thorough understanding of the present invention, and to be able to fully convey the scope of the present invention to those skilled in the art.

[0040] Example 1

[0041] This embodiment provides a method for repairing a river network water system ecosystem. The repair object is a river network water system in Wujin District, Changzhou City, Jiangsu Province. The specific method is as follows:

[0042] (1) June-August 2022: Evaluation of propagule reservoir activity. Sediment samples were obtained from the bottom of the water body. The sampling section spacing was set at 50-100 m to ensure the representativeness of the samples. The bottom was concentrated on site using a 200-mesh (φ0.075 mm) standard sieve. Each sample was evenly spread over an area of ​​0.0452 m 2In a pot filled with sterilized sand, add tap water that has been exposed to the sun for 1-2 days to a water depth of 5-10 cm. All pots are placed in a constant temperature and light incubator at 20-25°C, and the light intensity is adjusted to 3000-3500lx. The pots are watered and moisturized every day. After germination begins, the species category and number of individuals in each pot are recorded. In addition, for the above-mentioned propagule storage pots, the plant growth hormone gibberellin (50-200ppm soaking treatment for 12-24h), biochar (added by volume ratio 3-10%) or mineral nutrient solution (5-10% potassium dihydrogen phosphate solution, soaking for 12-24h) is used to promote the dormant propagules to start the germination process, and accurately evaluate the potential germination ability of various plant propagules.

[0043] (2) From September to October 2022 and February 2023, seeds or seedlings of Potamogeton crispus, Nymphoides peltata, and Trapa natans will be introduced into the estuary and deep water areas (areas with more serious pollution) to initially build a water quality control plant framework to control suspended particulate matter and organic matter.

[0044] (3) From February to March 2023, plant evergreen dwarf Vallisneria in shallow coastal waters (within 1.5 m) to construct a pilot community. The total area of ​​the pilot plant community should account for 10% of the total area of ​​the river network to be restored.

[0045] At the same time, winter buds (propagules) of Hydrilla verticillata and Vallisneria natans seeds, which had been soaked in potassium dihydrogen phosphate solution (concentration 5%) and wrapped in yellow loam mud balls containing biochar (content 1%), were sown at a density of 10 kg / mu to enrich the propagule pool resources and promote the germination of the propagules.

[0046] In addition, in areas with poor water quality or severe bottom conditions, improving the bottom quality, increasing the organic matter content, and proper water level management (maintaining a stable water level or slightly lowering the water level to improve water light conditions) can help promote the germination of submerged plant propagules.

[0047] (4) In April and May 2023, introduce Hydrilla and Ceratophyllum demersum seedlings (submerged plants) in the main waters of the river sections with more serious bottom pollution. The planting density of Hydrilla and Ceratophyllum demersum is 800-1200g / m 2 The planting time is from April to June to improve water pollution. Combined with (2), the water quality control plant framework is further improved.

[0048] In the main water area of ​​the river section, where the water flow speed is fast (above 0.1m / s) and the water depth is greater than 2m and the water penetration ratio is ≤1 / 2, submerged plants are planted in ecological suspended beds. The area of ​​ecological suspended beds is 1000-3000m per hectare of water. 2 , the plant planting density is 100-200 plants / m 2 .

[0049] Among them, species with strong adaptability and rapid growth, such as waterweed, black algae, water chestnut and water hyacinth (Nymphoides peltata), have good environmental adaptability and can quickly form a stable plant community. Introducing submerged plants with strong water purification functions, such as black algae and duckweed, can effectively absorb excess nutrients (such as nitrogen and phosphorus) in the water, reducing the possibility of algae outbreaks.

[0050] (5) Based on the plant communities of the ecologically excellent rivers in the region, companion plants are introduced into the main waters of the river sections: Malaysian Potamogeton, Spike Foxtail Algae and Evergreen Dwarf Vallisneria are introduced in May-June 2023. The water quality control plant framework in step (4) provides a good water environment for functional plants. The introduction of the above companion plants further improves the water purification efficiency, and together with the water quality control plant framework and the propagule supplementary plants and predecessor plants in step (3), an ecosystem with high plant population diversity is formed.

[0051] Companion plants were introduced in a patch-like arrangement, with each patch covering an area of ​​30m 2 Three kinds of plants are set in each patch, and the distance between patches is 10m.

[0052] Companion plants ensure that plant communities complement each other in function and enhance the stability and resilience of the ecosystem. In the restoration process, submerged plants should account for 50-60% of all plant communities to improve water quality and inhibit algae reproduction; floating plants and emergent plants should each account for 20-25%, eventually forming a multi-layered plant structure, with floating plants including water chestnuts, water hyacinths, lotus, etc.

[0053] Since June 2023, after the above restoration measures, the aquatic plant coverage of this river network water system has increased from less than 3% to 77%, the average water transparency has increased from 0.35m to 0.89m, and various nitrogen and phosphorus indicators of the water body have decreased to varying degrees. The water quality has stabilized at the Class II level of river water body, and the number of species in the aquatic plant community has increased to 7 species and the coverage has remained stable.

[0054] (5) From August to November 2023, harvest and manage various plants in the river waters that are in the fruit maturity period: manually harvest the branches of dominant species, adjust the density, maintain interspecies balance, and be vigilant against the spread of alien invasive species (such as water hyacinth). At the same time, retain the propagules in a targeted manner, so that their seeds and buds mature and fall into the bottom mud before daily harvesting and cleaning work is carried out. Specifically, retain the seeds of Myriophyllum spicate and Potamogeton truncatum in August and September, and retain the seeds of Vallisneria serrata, winter buds of Hydrilla verticillata and water chestnut in October and November. The retention of propagules also takes into account the density adjustment of different plants. For example, when the population density of Myriophyllum spicate is large, the retention of its propagule bank can be reduced accordingly.

[0055] A survey of the propagule pool in the restoration area from February to April 2024 showed that the number of propagules with potential germination activity of aquatic plants per square meter exceeded 200. During March to June 2024, without the artificial introduction of propagules, the aquatic plant community recovered well naturally, and the coverage remained above 50%. During July and August, it increased to more than 80%, forming a self-sustaining complex community structure. The water environment is good and stable above the river Class II level.

[0056] (6) After the ecosystem is running stably, daily management of the ecosystem is implemented at the same time: water flow control, by moderately regulating the river flow, to prevent the water flow from washing away the submerged plants too fast, to ensure that the plants can grow stably and play a role in purifying water quality; blue algae bloom control, by combining physical barriers and biological inhibition to limit the spread of blue algae; sewage outlet pollution control, by setting up a pollution interception pool near the sewage outlet to reduce the spread of pollution and increase the pollution residence time, by using physical and microbial agents inside the interception pool for initial treatment, and by setting up an ecological buffer zone after the interception pool, using plants to help filter pollutants and reduce the impact of sewage on the water ecosystem; vegetation construction in shallow coastal waters, with evergreen species as the main species in shallow coastal waters, to build a long-term and stable submerged plant system. Evergreen species have strong stress resistance and can survive for a long time under different hydrological conditions, forming a stable plant zone, effectively improving water transparency and maintaining the stability of the water ecosystem.

[0057] It should be noted that in this embodiment, the aquatic organisms do not need to be adjusted.

[0058] Example 2

[0059] This embodiment provides a method for repairing a river network water system ecosystem. The repair object is a river network water system in Qingpu District, Shanghai. The specific method is as follows:

[0060] (1) Evaluation of propagule pool activity: For specific methods, see Example 1;

[0061] (2) Based on the investigation of the propagule pool of the water system, from February to March 2024, seeds of Vallisneria sinensis, winter buds of Hydrilla verticillata and seeds of Cycas revoluta were introduced into the main waters of the river network. The three were mixed and sown intermittently. Each section was about 10 m long, and the sowing densities were 10 kg / mu, 15 kg / mu and 3 kg / mu respectively to supplement the propagules of aquatic plants.

[0062] (3) From March to April 2024, winter buds of Hydrilla, water chestnut seeds and Nymphoides seedlings were planted in sequence at the three estuary intersections in the project area to construct a water quality control plant framework. At the same time, evergreen dwarf Vallisneria was planted in the waters within 1 m of the nearshore water depth to construct a pilot community. The total area of ​​the pilot plant community accounts for 15% of the total area of ​​the river network to be restored.

[0063] (4) According to the plant communities of the ecologically sound rivers in the region, supplement the introduction of companion plants in the main waters of the river section: introduce Malayan Potamogeton, Spike Myriophyllum and Evergreen Dwarf Vallisneria in May-June 2023. Supplement the introduction of companion plants in a patch-like arrangement, with each patch covering an area of ​​10m 2 Three kinds of plants are set in each patch, and the distance between patches is 20m.

[0064] In July 2024, a dense plant belt was formed in the planting area, increasing the water transparency in the restoration area from 0.3m to 0.6m. In August 2024, the coverage of aquatic plant communities exceeded 85%, and the average water transparency exceeded 1.2m.

[0065] (4) From August to September 2024, the fruits of various aquatic plants in the water system were preserved until they dropped, further enriching the aquatic plant propagule pool.

[0066] Under the above restoration measures, the average transparency of the water body will exceed 1.1m during June-September 2024, and the reduction rates of total nitrogen and total phosphorus concentrations in the water body will exceed 50%, stably reaching Class II water quality for river water bodies.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for repairing a river network water system ecosystem, characterized in that: The following steps are involved: S1. Construct a water quality control plant framework: Introduce aquatic plant species that improve the water environment at the nodes and areas with greater impact on water quality in the river network to be restored, so as to form a water quality control plant framework with stable growth and expansion within 1-3 months. The nodes and areas with greater impact on water quality include river mouths, concentrated pollution input points, and water areas where water flows meet; S2. Assessment of propagule pool activity: Collect sediments in the river network to be restored and assess the species with potential germination capacity and their density in the propagule pool of the water system; S3. Propaganda pool supplementation: Based on the assessment results of S2, species lacking propagule resources in the river network to be restored are supplemented to enable them to germinate and grow to form supplementary communities; species lacking propagule resources are species with a potential germination density of less than 20 plants / m 2 of plant species; S4. Improve biodiversity: In restored waters where the growth of aquatic plant communities is stable and the water depth ratio is kept stable at ≥ 0.5, continue to introduce companion plants that help improve water quality and stabilize aquatic plant communities.

2. The method for repairing a river network water system ecosystem according to claim 1, characterized in that: In S1, the water quality control plant framework also includes the introduction of submerged plants with strong water purification functions through ecological hanging beds in waters where aquatic plants cannot directly colonize and survive in the river network water system to be restored; Water areas where aquatic plants cannot directly colonize and survive are areas that meet at least one of the following conditions: the water penetration-depth ratio is less than 0.5, the water flow velocity is greater than or equal to 0.1m / s, and the bottom sediment redox potential is less than 80mV.

3. The method for repairing a river network water system ecosystem according to claim 1, characterized in that: In S3, the introduced propagules were disinfected, screened, and pretreated with 0.1-5 mmol / L salicylic acid solution before being submerged; Propaganda of different species are sown together.

4. The method for repairing a river network water system ecosystem according to claim 1, characterized in that: In S1, the water areas outside the water quality control plant framework water areas in the river network type water system to be restored, and the water depth ratio is stably maintained at ≥0.5 and the bottom sediment redox potential is ≥80mV to construct the prior plant community.

5. The method for repairing a river network water system ecosystem according to claim 4, characterized in that: A patchy arrangement is used to supplement the introduction of companion plants and pioneer plant communities.

6. The method for repairing a river network water system ecosystem according to claim 1, characterized in that: Reducing herbivorous and omnivorous fish populations before introducing aquatic plants into the river system to be restored; After step S1, introduce benthic animals: After the water quality control plant framework community is stabilized, conduct a resource survey and assessment of the benthic animal community within the water system restoration area, and set biomass targets for different groups: Among them, the biomass targets for snails and shellfish are 15-20g / m 2 Shrimp will be supplemented according to the biomass target of 0.2-0.3kg / mu to guide the healthy and stable recovery of the population.

7. The method for repairing a river network water system ecosystem according to claim 1, characterized in that: It also includes S5, harvesting management: before the aquatic plant community in the river network to be restored reaches stability, the branches of dominant species are harvested manually, and high-intensity harvesting is avoided during the flowering and fruiting period and the winter bud period.

8. The method for repairing a river network water system ecosystem according to claim 2, characterized in that: In S1, the submerged plants with strong water purification function include one or more of duckweed, black algae, spike foxtail algae, Vallisneria and giant ferns.