LU503178B1

LU503178B1 - Method for ecological restoration of lakeside zone of shallow lake

Info

Publication number: LU503178B1
Application number: LU503178A
Authority: LU
Inventors: Beibei Jing; Juan Jiang; Liya Wei; Zhihua Lv; An Du; Xiaodan Ju; Wenji Wang
Original assignee: Shanghai Landscape Architecture Design & Res Institute Co Ltd
Priority date: 2022-12-12
Filing date: 2022-12-12
Publication date: 2023-06-12

Abstract

Described is a method for ecological restoration of lakeside zones, in particular to a method for ecological restoration of a lakeside zone of a shallow lake, which comprises the following steps: a, selecting an area: selecting an area with eutrophic water, rich nutritive salt in bottom mud and serious water pollution as a to-be-restored area; b, arranging a wave-proof layer; c, arranging a wave-dissipating layer; and d, carrying out seasonal ecological restoration. According to the present invention, submerged plants are seasonally alternated, and pioneer species are planted in each season, thereby improving and stabilizing a water environment; well-proportioned aquatic plant communities combined by emergent aquatic plant, floating plant, floating-leaved plant and submerged plant communities are formed.

Description

METHOD FOR ECOLOGICAL RESTORATION OF LAKESIDE ZONE OF SHALLOW LAKE

LU5S03178

TECHNICAL FIELD

The present invention relates to a method for ecological restoration of lakeside zones, and particularly relates to a method for ecological restoration of a lakeside zone of a shallow lake.

BACKGROUND ART

Eutrophication refers to a phenomenon that inorganic nutrients such as nitrogen (N) and phosphorus (P) which are required by organisms enter relatively closed or slowly flowing water bodies such as lakes, river mouths and bays in a large amount, and consequently, algae and other plankton are quickly propagated under the comprehensive factor action of a proper external environment (physical and chemical environments of a water area) to cause the outbreak of water bloom (red tide). In some cases, it might cause the reduction of dissolved oxygen content of water bodies, deterioration of the water quality, and even the death of a large amount of fishes and other aquatic organisms.

There are many lakes in China. There are more than 2,300 natural lakes larger than 1 km? the total area of the lakes reaches 70,988 km? and accounts for 0.8% of the total land area of

China, and the total water storage of the lakes is more than 707.7 billion m*. However, the lake environment in China is not good. Nutrients in the lakes come from a wide range of sources and have abnormally high background concentration. The lakes are subjected to rapid eutrophication, and many lakes are in an eutrophic state, such as East Lake in Wuhan City,

Dian Lake in Yunnan Province, Xuanwu Lake in Nanjing City, and Taihu Lake in Jiangsu

Province. The lakes which have been in the eutrophic state or have a serious eutrophication trend account for 56% of the total quantity. The eutrophication of the lakes not only enables the water bodies to lose their due functions, but also makes the aquatic ecological environment of the lakes evolve towards the direction which is not beneficial to the survival and development of human beings, which seriously affects the sustainable development of social economy.

Therefore, controlling the eutrophication progress of the lakes and performing effective treatment and restoration are a great work that benefits the present age and contributes to the future.

The eutrophication occurs due to social and historical reasons, and it is caused by multiple related factors. In light of long-term environmental protection practice, the prevention and control of water eutrophication is a complex system engineering, it involves multiple disciplines such as society, economy, humanity, geography, weather, environment, biology, physics and chemistry, and it is the most difficult and expensive problem in water pollution control. On one hand, N and P nutrient substances causing the water eutrophication are very complex in sources, including natural sources, artificial sources, exogenesis, endogenesis, point sources and non-point sources, which brings great difficulty to pollution source control. On the other LU503178 hand, the treatment process is outdated and is slowly developed, it is difficult to remove the nutrient substances, and there were no single biological, ecological, chemical and physical measures for thoroughly removing the N and P nutrient substances in wastewater so far. At present, the prevention and control of lake eutrophication mainly focuses on controlling of nutritive salts, and a technical route of “high-strength pollution control— natural ecological restoration” is mostly adopted, that is, the control of N and P pollution load is combined with ecological restoration measure. However, few of them really work.

The research on the eutrophication of the lakes in China can be traced back to 1950s- 1960s. Although the eutrophication of the lakes in China was not widespread or serious at that time, Mr. Rao Qinzhi, a famous limnologist in China, has introduced the concept of carrying out nutritional division on the lakes by international limnology to China, which has provided an important theoretical basis for the research on the eutrophication of the lakes in China.

The large-scale investigation and research on the eutrophication of the lakes were started in China in the late 1980s. These early researches focused on the evaluation of the eutrophication degree of the lakes, and the adopted indexes mainly included the water quality (such as TN, TP, SD and chlorophyll a) of the lakes and the aquatic biological indexes (such as dominant species of phytoplankton, and biodiversity indexes). Carlson trophic state index (or

Aizaki modified trophic state index method) is widely used in China to evaluate the eutrophication degree of the lakes. At present, there are many kinds of methods for evaluating the eutrophication of the lakes, more indexes are adopted, and the main evaluation methods include a fuzzy evaluation method, a principal component evaluation method, and evaluation by utilizing various mathematical models.

In a lake eutrophication formation mechanism, the input of N and P (including non-point source and point source pollution) is basically taken as the main cause of eutrophication.

However, that the change of a water body ecological system, especially the change of a food web structure, can promote the lake eutrophication formation is not widely accepted. The relation between the lake eutrophication and the outbreak of harmful algal bloom (HAB) is mostly taken as a causal and inevitable relation, that is, the outbreak of the algal bloom is taken as a representation of water eutrophication.

However, the research in Qiandao Lake, Zhejiang Province shows that water blooms mostly occur in eutrophic water bodies, but there is a certain difference between the outbreak of the water blooms and the lake eutrophication. There are also some differences in control methods. The water blooms can occur not only in eutrophic water bodies, but also in water bodies that have not yet reached eutrophication state. Biological manipulation can effectively control the water blooms, but the control of the eutrophication is more complicated.

Early treatment mainly focused on the control of various pollution sources, such as withdrawing polluted enterprises from lakesides, and discharging domestic sewage and industrial wastewater. These methods have been proved to be insufficient to effectively treat LU503178 eutrophic lakes. Therefore, the current treatment methods for lake eutrophication also include direct control of the algal blooms, control of endogenous pollution and various ecological restoration of the lakes. The main measures include: 1. Physical methods

A physical or mechanical method is mainly adopted to reduce the concentration of nutrients in the water body so as to achieve the purpose of reducing the eutrophication degree of the water body. The method includes: 1) dredging of bottom mud: the bottom mud is often considered as one of the main sources of endogenous pollution. Long-term eutrophication causes a large number of nutrients to be deposited at the bottom of the lake, so that dredging the bottom mud is an important means for controlling the release of the endogenous nutrients. The method has been adopted in the treatment of lakes such as West Lake, Taihu Lake and Dian Lake in China. 2) water introducing for dilution or water changing: clean river water is directly introduced to dilute or even a part of lake water is changed to achieve the purpose of diluting the concentration of the nutrients and controlling the eutrophication of the lake. E.g., the water of the Qiantang River is introduced into West Lake, Hangzhou Province, thus the water quality is well improved in a short time. This method is also widely adopted in China (such as the treatment of the Suzhou River in Shanghai City, the Taihu Lake in Jiangsu Province) at present, and has the main advantage of quick response, but this method cannot completely solve the problem. The method cannot be adopted in places without large ideal water sources (such as the Dian Lake). 3) silt covering method: this method is mainly to control the water blooms, rather than treating eutrophication. That is, a large amount of muddy water is sprayed on the water body with the water bloom, the nutrients are absorbed by using silt, and algae is settled and covered to achieve the purpose of clarifying water. And 4) shading method: some research unit in China also provides a method for covering the water body to reduce the illumination on the water body so as to achieve the purpose of controlling the water bloom. The method has low applicability to lake. 2. Chemical methods

The chemical methods are mainly used for controlling the algal bloom in the eutrophic lake rather than controlling eutrophication. These methods are mainly to eliminate algae with various chemical medicaments, and the common chemical reagent is copper sulfate. These method are not suitable for large-scale use, are easy to cause new ecological problems, and are not suitable for popularization. 3. Biological or ecological methods

The methods mainly include: 1) algae controlling by zooplanktons (Cladocera). This method is called as a biological manipulation method abroad and is also adopted in China. The utilized Cladocera mainly LU503178 includes daphnia magna, other C/adocera such as Diaphanosoma and Bosmina are also used. 2) algae controlling by the silver carps and the bighead carps. This method is called as a non-classical biological manipulation method in China. The silver carps and the bighead carps are special fishes in China, so this method is a main method in China. Practices prove that this method has obvious effect on controlling the algal bloom and even reduces the eutrophication degree of the lake to a certain degree. 3) restoration of aquatic vegetation. The aquatic vegetation in the shallow lake is restored.

This method is also a method widely used in China at present. Various emergent aquatic plants, — floating-leaved plants and submerged plants are mainly planted along banks of the lake. The eutrophication degree of the lake is reduced by using the absorption of the plants to nutritive salt. This method mainly has the following limitations: the eutrophic lake has a poor substrate and is extremely unfavourable for the growth of the plants; and in winter, the plants grow slowly and even stop growing due to low water temperature so as to lose the sewage treatment capacity.

In addition, the aquatic plants are also planted on floating materials to form a so-called biological floating island. But the effectiveness of this technology is to be proved. Because the restoration technology is based on the aquatic plants, if there is no vegetation with a certain area, the effect is generally difficult to achieve. And 4) microbial method. It includes two methods: (1) various micro-ecological preparations are utilized to accelerate the decomposition of various organic matters so as to achieve the purpose of improving the substrate of the lake, and this method is widely applied to aquaculture water bodies, but is also not widely applied to lake treatment; and (2) algal viruses are adopted to eliminate the algae subjected to the algal bloom, and this method is still in a laboratory research stage at present. Because the release of the algal viruses may cause new ecological risks, its ecological safety is to be proved.

Although the treatment of lake eutrophication in China already attracts the attention of related parties, and a large amount of manpower and material resources have been invested or were prepared to be invested in various places to carry out the treatment of lake environment, there are still some problems in the treatment of the lake eutrophication in China in view of the current situation, which are mainly shown as follows: 1. Insufficient ecological restoration of the lake area.

Although the ecological restoration of the lake is considered as a main means for controlling the lake eutrophication, there are still no enough restoration measures adopted due to various reasons when implementing ecological restoration project in the lake. For example, a so-called biological floating island technology is adopted, but there are no biological measures with enough strength or quantity, consequently, the absorption to the pollution sources is extremely limited, and the process of the lake eutrophication cannot be fundamentally stopped.

2. Lack of understanding on lake eutrophication mechanism and improper ecological LU503178 restoration method.

A single factor is mainly focused in the research and engineering practice of the lake eutrophication control technology, and the exertion of overall function of the ecological system is 5 ignored. Inappropriate technology selection, lack of research on coupling and integration of various technologies, and insufficient research on the applicability of engineering measures, the integrated application of different technology combinations and the influence of engineering measures on the overall function of the ecological system of the lake lead to the lack of systematic and long-term consideration on the technology application and engineering practice.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to treat the eutrophication of a shallow lake. The present invention provides a method for ecological restoration of a lakeside zone of a shallow lake, which adopts comprehensive technical measures of ecological restoration through microorganisms, fishes, shellfishes, aquatic plants and the like; well- proportioned aquatic plant communities combined by emergent aquatic plant, floating plant, floating-leaved plant and submerged plant communities are formed; submerged plants are seasonally alternated, and pioneer species are planted in each season, thereby improving and stabilizing a water environment; and the ecological restoration period of the method is short, less investment is needed, the treatment effect is significant, and the social, ecological and economic benefits are obvious.

The technical solution adopted to solve the technical problem in the present invention is that a method for ecological restoration of a lakeside zone of a shallow lake comprises the following steps: a, selecting an area: selecting an area which has water depth of 1 to 4 m, is originally an enclosure aquaculture water area, and has eutrophic water, rich nutrient salt in bottom mud, deposited sludge of 20 to 40 cm and serious water pollution influenced by river sewage as a to- be-restored area; b, arranging a wave-proof layer: planting emergent aquatic plants and hygrophytes along edges of the to-be-restored area as a biological dam; c, arranging a wave-dissipating layer: dividing the water area into a plurality of north-south ribbon areas by using Moso Bamboos and meshes, wherein the Moso Bamboos and the meshes are arranged in two rows, and the water area in which floating plants and floating- leaved plants are planted in each ribbon area accounts for 30% to 50% of the total water area of the to-be-restored area; and d, carrying out seasonal ecological restoration: breeding silver carps and bighead carps in a free-ranging way in winter; breeding fishes which ingest algae and organic impurities on a bottom layer outside the area with the floating plants and the floating-leaved plants in a free-

ranging mode, and breeding mussels and snails in a free-ranging mode; splashing 0.02 to 0.03 5034 78 ppm of concentrated bacillus for improving the water quality and improving the transparency of a water body into the water body in the to-be-restored area in spring; planting waterweed in a shallow water area with water depth of 0.5 to 0.8 m in autumn and winter; spreading bottom mud with dormant seeds of water caltrop and eel grass in winter; and planting hornwort and

Potamogeton malachii in spring.

Planting emergent aquatic plants and hygrophytes as a biological dam, dividing a to-be- restored water area into a plurality of ribbon areas by using Moso Bamboos and meshes, and planting floating-leaved plants and floating plants to achieve effects of preventing waves, dissipating waves, and limiting river mouth sewage to enter and absorb water body nutrition; splashing photosynthetic bacteria in spring to improve the water quality and improve the transparency of a water body; breeding silver carps and bighead carps in a free-ranging way in winter to ingest zooplankton and plants in the water body; breeding fishes which ingest algae and organic impurities on a bottom layer in a free-ranging mode, and breeding mussels and snails in a free-ranging mode to ingest the algae and the inorganic impurities on the bottom layer to reduce the eutrophication of the water body; planting waterweed in a shallow water area with water depth of 0.5 to 0.8 m in autumn and winter; spreading bottom mud with dormant seeds of water caltrop and eel grass in winter as submerged plant pioneer species of spring and early summer; and planting hornwort and Potamogeton malachii in spring to form submerged plant pioneer species with eel grass of summer and autumn. The submerged plants are seasonally alternated, and pioneer species are planted in each season, thereby improving and stabilizing a water environment. The well-proportioned aquatic plant communities combined by emergent aquatic plant, floating plant, floating-leaved plant and submerged plant communities are formed. Comprehensive technical measures of ecological restoration through microorganisms, fishes, shellfishes, aquatic plants and the like are adopted, thereby avoiding secondary pollution. The ecological restoration period is short, less investment is needed, the treatment effect is significant, and the social, ecological and economic benefits are obvious. The ecological landscape of the lakeside zone is improved, and the biological diversity of birds, plants, aquatic organisms and the like is restored.

In order to achieve good wave-proofing and wave-dissipating effects, the width of the ribbon areas is 6 - 10 m, the height of the meshes is 0.8 - 1 m, and the underwater penetration of the meshes can be manually adjusted according to the size of water waves in the lake.

In order to achieve a good ecological restoration effect, avoid secondary pollution and moderately develop fishery production, the free-ranging density of the silver carps and the bighead carps in the to-be-restored area is that 10 - 15 g of silver carps and bighead carps are bred in the water body per m°, and the number of the silver carps and the bighead carps is equal to each other; the free-ranging density of the mussels and the snails is that 2 - 5 mussels and 20 - 50 g of snails are bred in the water body per m?; and the fishes which ingest the algae and the organic impurities on the bottom layer are Plagiognathops microlepis fishes, and the LU503178 free-ranging density is that 0.5 - 1 Plagiognathops microlepis fish is bred in the water body per m°.

In order to achieve a good ecological restoration effect and increase the economic benefits while realizing ecological restoration, the floating-leaved plants are lotus roots and/or water chestnuts; the emergent aquatic plants are reeds and/or cattail; the floating plants are

Eichhornia crassipes and/or Alternanthera philoxeroides; and the hygrophytes are wormwood and/or willow.

The method for ecological restoration of the lakeside zone of the shallow lake in the present invention has the beneficial effects that the submerged plants are seasonally alternated, and pioneer species are planted in each season, thereby improving and stabilizing the water environment. The well-proportioned aquatic plant communities combined by the emergent aquatic plant, floating plant, floating-leaved plant and submerged plant communities are formed.

Comprehensive technical measures of ecological restoration through microorganisms, fishes, shellfishes, aquatic plants and the like are adopted, thereby avoiding secondary pollution. The ecological restoration period is short, less investment is needed, the treatment effect is significant, and the social, ecological and economic benefits are obvious. The ecological landscape of the lakeside zone is improved, and the biological diversity of birds, plants, aquatic organisms and the like is restored. The water environment quality is improved, and the lakeside zone can serve as a domestic drinking water source after large-area ecological restoration. The fishery function can be developed moderately, and green products such as crabs and shrimps can be bred to promote local rural economic development.

DETAILED DESCRIPTION OF THE INVENTION

As the best embodiment of the present invention, a method for ecological restoration of a lakeside zone of a shallow lake comprises the following steps: a, selecting an area: selecting an area which has water depth of 1 to 4 m, is originally an enclosure aquaculture water area, and has eutrophic water, rich nutrient salt in bottom mud, deposited sludge of 20 to 40 cm and serious water pollution influenced by river sewage as a to- be-restored area; b, arranging a wave-proof layer: planting emergent aquatic plants that are reeds and cattail and hygrophytes that area are wormwood and willow along edges of the to-be-restored area as a biological dam; c, arranging a wave-dissipating layer: dividing the water area into a plurality of north-south ribbon areas by using Moso Bamboos and meshes, wherein the Moso Bamboos and the meshes are arranged in two rows; the width of the ribbon areas is 8 m, the height of the meshes is 0.8 m, and the underwater penetration of the meshes can be manually adjusted according to the size of water waves in the lake; and floating plants that are Eichhornia crassipes and

Alternanthera philoxeroides and floating-leaved plants that are lotus roots and water chestnuts 5031 78 are planted in each ribbon area, and the water area in which the floating-leaved plants and the floating plants are planted accounts for 30% to 50% of the total water area of the to-be-restored area; and d, carrying out seasonal ecological restoration: breeding silver carps and bighead carps in a free-ranging way in winter, wherein the free-ranging density of the silver carps and the bighead carps is that 10-15 g of silver carps and bighead carps are bred in the water body per m°, and the number of the silver carps and the bighead carps is equal to each other; breeding Plagiognathops microlepis fishes which ingest algae and organic impurities on a bottom layer outside the area with the floating plants and the floating-leaved plants in a free-ranging mode, wherein the free- ranging density is that 0.5 - 1 Plagiognathops microlepis fish is bred in the water body per m?; and breeding mussels and snails in a free-ranging mode, wherein the free-ranging density is that 2 - 5 mussels and 20 - 50 g of snails are bred in the water body per m?; splashing 0.02 ppm of concentrated bacillus for improving the water quality and improving the transparency of the water body into the water in the to-be-restored area in spring; planting waterweed in a shallow water area with water depth of 0.5 to 0.8 m in autumn and winter; spreading bottom mud with dormant seeds of water caltrop and eel grass in winter; and planting hornwort and Potamogeton malachii in spring.

Claims

LU5S03178 CLAIMS

1. A method for ecological restoration of a lakeside zone of a shallow lake, comprising the following steps:

a. selecting an area: selecting an area which has water depth of 1 to 4 m, is originally an enclosure aquaculture water area, and has eutrophic water, rich nutrient salt in bottom mud, deposited sludge of 20 to 40 cm and serious water pollution influenced by river sewage as a to-be-restored area;

b. arranging a wave-proof layer: planting emergent aquatic plants and hygrophytes along edges of the to-be-restored area as a biological dam;

c. arranging a wave-dissipating layer: dividing the water area into a plurality of north-south ribbon areas by using Moso Bamboos and meshes, wherein the Moso Bamboos and the meshes are arranged in two rows, and the water area in which floating plants and floating-leaved plants are planted in each ribbon area accounts for 30% to 50% of the total water area of the to-be-restored area; and d. carrying out seasonal ecological restoration: breeding silver carps and bighead carps in a free-ranging way in winter; breeding fishes which ingest algae and organic impurities on a bottom layer outside the area with the floating plants and the floating-leaved plants in a free-ranging mode, and breeding mussels and snails in a free-ranging mode; splashing 0.02 to 0.03 ppm of concentrated bacillus for improving the water quality and improving the transparency of a water body into the water body in the to-be-restored area in spring; planting waterweed in a shallow water area with water depth of 0.5 to 0.8 m in autumn and winter; spreading bottom mud with dormant seeds of water caltrop and eel grass in winter; and planting hornwort and Potamogeton malachii in spring.

2. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the width of the ribbon areas is 6 - 10 m, the height of the meshes is 0.8 - 1 m, and the underwater penetration of the meshes can be manually adjusted according to the size of water waves in the lake.

3. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the free-ranging density of the silver carps and the bighead carps in the to- be-restored area is that 10 -1 5 g of silver carps and bighead carps are bred in the water body per m°, and the number of the silver carps and the bighead carps is equal to each LU503178 other; the free-ranging density of the mussels and the snails is that 2-5 mussels and 20-50 g of snails are bred in the water body per m?; and the fishes which ingest the algae and the organic impurities on the bottom layer are Plagiognathops microlepis fishes, and the free- ranging density is that 0.5 - 1 Plagiognathops microlepis fish is bred in the water body per m°.

4. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the floating-leaved plants are lotus roots and/or water chestnuts.

5. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the emergent aquatic plants are reeds and/or cattail.

6. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the floating plants are Eichhornia crassipes and/or Alternanthera philoxeroides.

7. The method for ecological restoration of the lakeside zone of the shallow lake according to claim 1, wherein the hygrophytes are wormwood and/or willow.