Study On The Suitable Biomass Of Aquatic Plants In The Confluence Area Between Lake And River Based On The PCLake Model

As a city lake seriously polluted by humans,Lihu Lake has carried out a large number of aquatic plant restoration projects,and the water quality has been significantly improved.At the same time,there are some side effects,such as the unreasonable density of aquatic plants,the explosion of some plants in summer and the secondary pollution caused by the decomposition and decomposition of a large number of plants in winter.Therefore,scientific management of aquatic plant biomass has become an urgent problem to be solved.In this study,a typical estuarine Lihu-Ludianqiaohama was selected as the research object.The winter and spring aquatic plant decay experiments were carried out.The PCLake model was used to complete the construction of the estuary model of the estuary and the estuary of the lake,The research results are as follows:(1)Through the investigation of the aquatic ecosystem in the study area,some important estuarine habitat factors,such as water quality,aquatic plants,plankton,benthic organisms,birds,and external nutrient input,are obtained.(2)In terms of experimental research on decay and decomposition of aquatic plants in the estuary,6 gradients of 0%,20%,40%,60%,80%,and 100%were set according to the estuary aquatic plant biomass.The experimental results showed that in the plant system,the plant is the main source of nutrient release and is mainly released into the water column,and a small amount migrates to the sediment.By comparing the content of nitrogen and phosphorus in the final water body,it is shown that when 80%of the biomass is removed and the remaining 20%of the biomass is harvested in winter,it has the best effect on maintaining the estuary water quality.(3)Based on the investigation and decay experiment results of the estuary ecosystem,a preliminary estuarine ecological model was constructed.Carry out parameter sensitivity analysis and calibration in sequence,run the model 800 times,determine the fitting degree of the measured and simulated values by the RMSE value,and finally determine the calibration values of 19 sensitivity parameters.The data of water quality,aquatic plant biomass and physical and chemical properties of water monitored from 2018 to 2019 are used to verify and analyze the model.In terms of model prediction,the results show that the existing submerged plant biomass is lower than the simulated value,and the emerging plant biomass is highly fitted to the simulated value.Therefore,the submerged plant biomass will increase to about 215g/m~2 in the next 3 years,The biomass of aquatic plants should be controlled below1930 g/m~2.In addition,the distribution space of aquatic plants also needs to be optimized to rationally plan the plant growth range.Regarding the prediction of estuary water quality,the restoration of aquatic plants is beneficial to reduce the nutrient content of the water body.If the study area is above Class III water,the direct input of external nutrients should also be controlled to strengthen the restoration of the river habitat.