Eutrophication Evaluation Of Lake Taihu Using Image Data Of HJ-1Satellite

The field experiments were conducted in Lake Taihu to observe many parameters such as remote sensing reflectance and water quality parameters, etc.Then, the water quality factor for evaluating Lake Taihu eutrophication status by remote sensing was confirmed. Based on the HJ-1satellite hyperspectral image data and multispectral image data, we constructed the eutrophication evaluation models of three-band algorithm and regression algorithm for Lake Taihu respectively. The spatial and temporal distribution of Lake Tahi’s eutrophication state was evaluated by using the HJ-1multispectral image data from2009to2011. The results will promote the using of HJ-1satellite image data in inland water eutrophication status monitoring. The results are as follows:(1) The confirmation of water quality factor of Lake Taihu eutrophication status evaluation by remote sensingChlorophyll concentration is the important parameter to connect the water eutrophication evaluation with remote sensing information. On one hand, chlorophyll of Lake Taihu has great influence on the remote sensing reflectance of water surface,, and its influence achieve the maximum especially in the red and near-infrared wavelengths, therefore, its changed information can be more shows on the water surface remote sensing information; on the other hand, when using the chlorophyll concentration as the only eutrophication status evaluation index, we could achieve the acceptable result, i.e., when compared with the comprehensive evaluation consequence, the average relative error is5.97%. So the chlorophyll concentration is determined as eutrophication remote sensing evaluation parameter in Lake Taihu.(2) The eutrophication evaluation model of Lake Taihu using hyperspectral image data of HJ-1SatelliteAccording to three-band algorithm theory and combining with the in situ measured hyperspectral data, we confirmed the bands which can effective response the spectrum characteristics of chlorophyll concentration are680nm,694nm and717nm. And the corresponding bands of HJ-1satellite are B76, B73and B80. Based on the simulative hyperspectral data of HJ-1satellite, we constructured the eutrophication evaluation model for Lake Taihu.The Determination coefficient of this model is0.7868, and the average absolute relative error of model is9.19%.(3) The eutrophication evaluation model of Lake Taihu using multispectral image data of HJ-1SatelliteRefer to the HJ-1satellite band set, we used the in situ measured hyperspectral data to simulate the multispectral image data.After comparing with39methods of band combination scheme, we constructured the eutrophication evaluation model of Lake Taihu using multispectral image data of HJ-1Satellite. TLI(Rrs)=168.03*(HJ4+HJ2)/(HJ1+HJ3)-91.55The average absolute relative error of model is11.77%.(4) The spatial and temporal distribution of eutrophication status in Lake TaihuWe used the eutrophication evaluation model which constructed by HJ-1satellite multispectral image data to monitor the eutrophication status from January2009to December2011of Lake Taihu. The monitoring results founds, at present the eutrophication status of Lake Taihu is still serious, and the main water in the most time are in eutrophication status, for example, the most serious of the months of2009,2010,2011for the area of hyper eutrophication status water occupied79.32%、41.23%and82.93%respectively. For the main bay area of the lake, the nutrition state of Meiliang Bay and Zhushan Bay were eserious, and algal bloom often appeared in these two bays. After comparing the nutrition state of three years, we found the trends of eutrophication status in2009and2011were quite similar, but there was an extremely difference btween2009,2011and2010. In addition, the eutrophication status of2009and2011in Lake Taihu were more serious than2010.