The Eutrophication Assessment Of Dongting Lake Water Quality Based On Blind Theory And Remote Sensing Technology

Eutrophication has become a global environmental problem in aquaticecosystems at present. Evaluation of eutrophication is not only a priority forenvironmental studies, but also an important basic work of water pr otection andpollution control. Dongting Lake is the second largest fresh water lake in China,which plays a very important role in regulating the middle reaches of the YangtzeRiver floods, maintaining the ecosystem balance and protecting the economic andsocial development. In recent years, the hydrological conditions of Dongting Lakehave been changed. The reduction of water volume from the Yangtze River results in asignificant decline in water dilution capacity and the growth of pollutants retentiontime. Then water quality of Dongting Lake presents the gradual decrement trend, andsome regions of Dongting Lake have mild eutrophication phenomenon. Therefore, inthis paper the eutrophication assessment method of Dongting Lake was studied anddiscussed, which was significance to protect Dongting Lake. Meanwhile, there will becertain references for the Dongting Lake managers.In this paper, the water of Dongting Lake was selected as research object and11representative sampling points were set. The eutrophication of Dongting Lake wasevaluated by uncertainty theory and using remote sensing technology.Firstly, taking consideration of uncertainty of parameters in the frequently-usedeutrophication assessment model, an improved comprehensive trophic level index wasdeveloped based on blind theory and dynamic cluster analysis, and the assessmentresults provided not only interval number of comprehensive trophic state index butalso their corresponding confidence level. Through the improved comprehensivetrophic state index, eutrophication state of water environment from the Dongting Lakein2009was evaluated as a case, and the corresponding results were spatiallyexpressed employing the kriging interpolation. The results show that the eastDongting Lake, Bianshan and Lujiao are at relatively serious eutrophication degreewith confidence level of eutrophication at0.5444,0.5318and0.5260, respectively.Secondly, due to Environmental Satellite1CCD data’s short revisiting periodand high spatial resolution, the objectives of this paper were to build the model ofretrieving chlorophyll-a concentration in Dongting Lake through the experiment ofsatellite-ground synchronization．The given water environment evaluation methodwas adopted to study the research on the spatial distribution of the Dongting lake eutrophication. The results show that the chlorophyll-a concentration in DongtingLake is different in different areas using the Environmental Satellite1CCD data.Some areas of the east Dongting Lake are of light-middle eutrophication, which isaccorded with the monitoring results of uncertainty theory assessment mothod. Fromthe two methods it can be seen tha the eutrophication of the east Dongting lake area isrelatively serious, and we should focus on prevention and protection this area in thefuture.