shows five reflectance spectra from four different lakes representative
of differentwater quality conditions, ranging fromlowto very
high CHL concentrations. Reflectance was measured above the water
surface with an ASD FieldSpec spectrometer. Table 2 summarizes the
characteristics of the lakes and the CHL concentrationmeasured concurrent
with the reflectance spectra. Chlorophyll-a has a distinct absorption
feature near 660–690 nm, evident in reflectance spectra from the
meso- and eutrophic lakes, Lake Idro, LakeMantua and Lake Trasimeno
(Fig. 3). The influence of phycocyanin on absorption at 620 nm can also
be seen in these lakes' spectra. High total suspended matter concentration
in Lake Trasimeno increases the scattering and thus increases the
overall reflectance, as well as creating a reflectance peak in the nearinfrared.
The spectra in Fig. 4 provide an example of some typical
water quality conditions, however, the ranges of freshwater systems