| In recent years,the East Dongting Lake Basin has a trend of increasing pollution and eutrophication of water bodies,and its ecological safety has hidden dangers.Therefore,it is necessary to protect the ecology of the East Dongting Lake and effectively monitor changes in water composition.The concentration of chlorophyll a can effectively reflect the eutrophication of water bodies.The degree of chemistry.It poses hidden dangers to the ecological safety of the East Dongting Lake.Therefore,it is urgent to monitor the ecology of the East Dongting Lake and effectively monitor changes in water composition.Therefore,the water quality status of the lake area and the research and early warning of water eutrophication provide effective technical support.Therefore,in this paper,the East Dongting Lake is used as the research area.Firstly,three chlorophyll a concentration inversion models are constructed,and the most accurate model is obtained.The remote sensing inversion of chlorophyll a concentration in the East Dongting Lake watershed was carried out to analyze the water quality status of the lake area and the degree of eutrophication of the water.The main research results are as follows:(?)Construction of three chlorophyll a concentration inversion models1)Pre-processing the Landsat8 remote sensing image data,finding a band with the highest correlation coefficient of chlorophyll a,and finally comparing the result of the inversion with the measured value to obtain a single-band inversion with an accuracy of 75.67%.model.2)Correlate the effect of each band of Landsat8 and its wavelength range,and find a set of bands with the highest correlation coefficient for inversion,and obtain a multi-band inversion model with accuracy of 78.32%.3)Using the 8 sample point data in 2015 as the parameter range and initial value of the LIBSVM model,predict the chlorophyll a concentration in the East Dongting Lake,and use the SVMcgForRegress.m code file to iteratively calculate the optimal selection of the model parameters.In order to establish the dataset of the chlorophyll inversion model,15 sets of B1,B2,B3,B4,B5,B6 and chlorophyll a concentrations were selected during the chlorophyll a estimation process,and the remaining five sets of data were used as test model accuracy.The data obtained an SVM inversion model with an accuracy of 84.2%.4)Compared with the three models,the SVM inversion model has the highest accuracy.(?)Evaluation of eutrophication status using TIS water1)From July 2016 to December 2017,the water nutrition index of Dongting Lake is between 20 and 70.The East Dongting Lake is above the middle eutrophication state,and the trophic state of the water near Yueyang City is serious.2)In July 2016,the East Dongting Lake had a higher nutrient index,which was moderately eutrophic.In December,the East Dongting Lake had a lower comprehensive nutrient index and was mildly eutrophic.3)The eutrophication status in June and December of 2017 was lower than that in June and December of 2016,indicating that the water quality in 2017 was better than that in 2016.4)The distribution of eutrophication index in East Dongting Lake in July 2016 and July 2017 showed a clear east-west phenomenon,indicating that the eutrophication of the waters in the east is higher than that in the west,which may be the cause of this phenomenon.It is close to Yueyang City in the east,and there are many factors such as urban sewage,industrial wastewater,aquaculture,and fishery bait,which leads to serious eutrophication.5)The distribution of eutrophication index in East Dongting Lake in December 2016 and December 2017 showed the phenomenon of the coastal side>the center of the basin,indicating that the eutrophication of the coastal side is higher than that of the center of the basin.The reason for this phenomenon may be In December,the temperature was lower,the water flow was smaller,and the water velocity in the edge zone was slower,so chlorophyll was deposited on the river bank.Therefore,using the nutritional status index TSL model to calculate the nutritional status of the East Dongting Lake during the study period is consistent with the results of the nutritional status of the East Dongting Lake during the identification study using remote sensing images.However,the calculation of the nutritional status index does not reflect the local nutritional status of the water body,and the identification of remote sensing images can reflect the overall trend of the water body and the local situation.Through the remote sensing inversion technology,the Landsat8 satellite remote sensing image data was used to evaluate the eutrophication status of the East Dongting Lake.The nutrient status of the East Dongting Lake watershed at the same time in different years was obtained.It is expected that the decision-making basis of the body will be unified,and it will also provide a more important theoretical basis for the ecological environment protection of the East Dongting Lake. |
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