A novel trophic status index of Lake Taihu based on in situ measured hyperspectral data

Using the hyperspectral data to evaluate the trophic state of inland waters is a more convenient approach for monitoring water quality than traditional methods. In the present study, field experiments were conducted for collecting water quality parameters and reflectance spectra in April, 2009 (48 samples) and May, 2010 (30 samples) in Lake Taihu, respectively. It has been proved that TLI(Chl-a) could replace TLI to evaluate the eutrophic state of Lake Taihu and the three-band model can be used to reflect the eutrophic state of the lake. Thereafter, a new trophic status index, called TLI(Rrs) which was deduced by remote sensing reflectance, was developed. And then the trophic state of Lake Taihu was evaluated by the new trophic status index. The results show that: the new trophic status index has high accuracies with relative error of 20% in evaluating the trophic state of Lake Taihu. In addition, the main area of Lake Taihu was suffuring from mesotrophic status, and only 23.21% and 19.63% areas of the lake belonged to light eutrophic status in April, 2009 and May, 2010, respectively. The most serious eutrophication occurred in Gonghu bay.