WATER QUALITY - THE WORLD ISLANDS
GSD used satellite Earth Observation to analyse freely available satellite imagery to contribute to our client’s understanding of patterns in water quality both in the local area and in the region. This was to enable a more informed assessment of the risk of algal blooms occurring in close proximity. The work was split into three main areas, that which considered MODIS satellite data for the region, that which used Landsat imagery to investigate turbidity and chlorophyll concentrations and that which used Sentinel 2 satellite imagery to model the spatial variations of chlorophyll-a and turbidity.
The main remote sensing instruments that have been designed to measure chl-a are SeaWiFS and MODIS. SeaWiFS was designed to primarily quantify chlorophyll produced by marine phytoplankton; however, this stopped collecting data in December 2010. MODIS has been providing many ocean water quality products since 2002 including: total suspended sediments (TSS), sea surface temperature (SST), and Chlorophyll-a (chl-a). Both satellites are used for regional-to-global monitoring of chl-a and thus have a coarse spatial resolution (1-4 km). Data from these missions are freely available from the USGS. GSD’s work on this project utilised the Normalised Difference Chlorophyll Index (NDCI) applying this to Sentinel-2 imagery.