Eutrophication evaluation of three lakes and one reservoir using CCD images from the HJ-1 satellite

The Chinese domestic satellite HJ-1 was launched in 2008. Because of its 2-day temporal resolution,it has become a significant resource for environment and disaster monitoring. Based on the in situ measured data,which are spectral reflectance and water quality parameters in Lake Taihu,Lake Chaohu,Lake Dianchi and the Three Gorges Reservoir,eutrophication evaluation models were developed. The models were based on the band settings of the HI-1 CCD images,and were used to quantify the nutritional status of these waters in 2009. The models have high accuracies with maximum mean relative error of 23.2%,and a minimum value of 6.8%. At the beginning of 2009,81.09% of the water area in Lake Taihu was mesotrophic,while the whole water area exhibited eutrophic status in April,May,June,September and November. And 85.75% of the whole water area was moderately eutrophic. Lake Chaohu and Lake Dianchi were eutrophic throughout the whole year. 66.67% and 89.75% of mean area of Lake Chaohu and Lake Dianchi were hypertrophic in most of 2009. During the year,the eutrophication of Lake Taihu and Lake Chaohu increased firstly,and then decreased. Conversely,the eutrophic status of Lake Dianchi decreased from May to September and the nutrition status of the Three Gorges reservoir was between oligotrophic and mesotrophic. And we also found that there was a significant negative correlation between water levels and the areas with alga blooms,with an r of-0.818. This indicates that the nutrition status of the reservoir is closely related to the impoundage.