Research On Ecological Dynamics Model Of Qingcaosha Reservoir Eutrophication

There are many lakes and reservoirs in our country.With the rapid development of economy and the extensive style of environment management,the ecological environment of the lakes and reservoirs has been fragile,and the eutrophication has been distinct.Shanghai is situated in the lowest reaches of the Yangtze River,where there are the main estuarine water resources(Chenhang,Dongfengxisha and Qingcaosha reservoir).The reservoirs are faced inevitably the risk of algae bloom induced by eutrophication due to the input of high nitrogen and phosphorus nutrients from the watershed water and coast load.This study is aimed to develop an ecological dynamic model to simulate temporal and spatial variation of the nutrients and main alga in lakes and reservoirs for their eutrophication risk.The achievement can offer an effective technology for the early warning of algae bloom and prevention of eutrophication in the water resources.It has important scientific meaning in the study area of ecological environment in lakes and reservoirs,and also has important application significance in safety of drinking water supply,environmental protection and municipal administration in Shanghai.The research contents and achievements of the paper are as follows:(1)With the historical hydrological,water quality and ecological data of the Qingcaosha reservoir,the hydrological and ecological characteristics were analyzed.The temporal and spatial variations of the main water quality and ecological indexes during the construction and operation periods of the reservoir were studied.The indexes included water temperature,secchi depth,dissolved oxygen,nutrients and chlorophyll-a.The variation processes of the trophic state in the reservoir in different hydrodynamic operations were evaluated comprehensively.(2)Based on the collected data of bathymetry,hydrology,meteorology and reservoir operation rules,a three-dimensional hydrodynamic model was constructed.This model can provide the hydrodynamic data to the eutrophication ecological dynamics model for mass transport and diffusion simulation.(3)Considering the characteristics of water quality and alga in the Qingcaosha reservoir,and referencing the achievements of international ecological model studies for lakes and reservoirs,an ecological dynamics model for shallow lakes and reservoirs was developed based on the open source water quality model RCA(Row-Column AESOP).This model can simulate the temporal and spatial variations of the main alga species(Cyanophyta,Chlorophyta and Bacillariophyta)under the varying conditions of water temperature,sunlight and nutrients.The alga competition mechanisms of nutrients uptake and grazing were induced in the model.It successfully simulated the variations of water quality indexes,dissolved oxygen,nutrients and chlorophyll-a,and the main algal species in the Qingcaosha reservoir.Based on this achievement,a module to simulate the taste and odor(T&O)compound was added in the ecological model.Following the historical T&O bloom data in the Qingcaosha reservoir and the international studies of T&O production mechanisms,this module was developed to simulate the process of T&O bloom,and to verify the reliability and practicability of the ecological model.The achievement of this study can provide technical support for the operational early warning of algae bloom and the intelligent management in the Qingcaosha reservoir.It can also be applied the study and management to the similar lakes and reservoirs.