DETECTION OF WATER QUALITY AND AQUATIC MACROPHYTE VEGETATION IN THE SOUTH COASTAL WATERSHED, MASSACHUSETTS USING LANDSAT ETM+ AND IKONOS IMAGERY

During the summer of 2001, water bodies on the south shore of Massachusetts were surveyed to evaluate water quality and identify the presence of specific plant species. Landsat ETM+ was acquired for 5 different overpasses and one IKONOS 4-meter multispectral image was purchased through the NASA ARC Program. A field crew consisting of remote sensing specialists and field geologists collected ground truth data concurrently with the image capture in a roughly 100-km² area equivalent to the IKONOS data set footprint. Field parameters collected during a four-hour window included water and plant visible and near-IR spectra as well as in situ water quality measurements such as turbidity, Secchi disk depth, and dissolved Oxygen. Laboratory analysis of water samples yielded chlorophyll-a and phosphorous content. Vegetation mapping was typically performed in the afternoon or within two days of a flyover.

Results of the field data suggest a possible relationship between Secchi disk transparency and chlorophyll-a concentrations. This relationship might be used as a cost effective solution for future monitoring. Accounting for atmospheric and radiometric distortions, a process was developed to detect the trophic state of the lakes and ponds in a subset of the study area. The process was then applied to all the water bodies in the south coastal watershed.