Study On The Water Ecological Construction Of Slow Flow Zone Of Artificial Lake

As the largest artificial recharge lake in Guangzhou,Baiyun Lake is a key project for the people's livelihood of the government.According to the water quality monitoring,the water quality of Baiyun Lake is rated as inferior V category all the year round.The main items exceeding the standard are TN,TP and NH3-N,and the water transparency is less than 20-45 cm.The problem of water quality has been restricting the improvement of the image of Baiyun Lake scenic area.Baiyun Lake,covering the water area of 1.06 square kilometers,is designed to recharge 800000-900000 m3 per day during the non-flood season and 400000 m3 per day during the flood season.It is in the dynamic process of water recharge and effluent all the year round that brings difficulties to water quality improvement.Taking Baiyun Lake as the research object,this study intends to construct a water ecosystem with a benign function of material circulation,energy flow and information transmission by adopting technical measures such as water enclosure,sediment in-situ remediation technology,and rational allocation of aquatic plants,aquatic animals,and fish and by introducing aquatic plant and animal seedlings of various native species into the water body to optimize the configuration of the food chain(web)structure.Through the above methods,a clear-water grass-type aquatic ecosystem demonstration area including “submerged water—emergent water—floating-leaved plant—fish—snails” is formed.The water body is clear and bottomless,and the main water quality indicators are better than the surface water category V standards.The main research conclusions are as follows.1.Through the rubber enclosure device,a 5000 square meter water ecological construction demonstration area is successfully established in Baiyun Lake,effectively dividing the water area,and reducing the exchange of water bodies and the release of internal load,which provide a good foundation for implementing corresponding water ecological construction measures;2.The sediment in-situ remediation technology is implemented to improve the sediment of the demonstration area,which can reduce the secondary pollution of the sediment to the water body of the demonstration area;3.The construction of submerged plant communities is the key to the construction of the aquatic ecological demonstration area.The submerged plants suitable for growing in artificial lake—Baiyun Lake are eel grass and watermifoil;4.Biomanipulation is adopted to build aquatic animal communities.The main aquatic animals include filtering-feeding fishes like silver carps and bighead carps,carnivorous fisheslike snakehead and mandarin fish,and benthonic animal like snail and shellfish.5.Through the construction of aquatic ecosystems,the demonstration area eliminates water quality of inferior V category,with declining phytoplankton biomass,increasingly optimized aquatic advanced plants,fishes and benthic species,increasingly complex food web structure,and increasingly healthy and stable aquatic ecosystem.