Mapping of chlorophyll-a concentration of reservoir Dajingshan, Zhuhai, China, from LandSat thematic mapper

Chlorophyll a (Chl-a) is an indicator of water quality, especially of eutrophic state. Remote sensing has been used to mapping Chl-a in lake, large river, estuary and ocean, due to its andvantages such as to provide data logistically and economically. The aim of this paper was to use LandSat TM image and suitable algorithm to estimate and map Chl-a concentration in reservoir Dajingshan, an important source for drinking water supply in Zhuhai city, China. After comparing several simple linear regression algorithms, a most suitable algorithm using brightness value of bands 1 to 4, was adopted. The results showed that the modeled chl-a concentration in November 23^th, 2005 had reasonable accuracy, with a mean absolute error of 0.002 mg/L when compared with the ground truth measurements. The chl-a concetration map showed that the reservior Dajingshan was in eutrophic conditions and the water could not be used as drinking water.