New satellite instruments to monitor condition of coastal and inland waters
Finnish scientists have demonstrated, for the first time ever, the use of satellite data for the simultaneous monitoring of water quality – such as algal blooms - in large lake and coastal regions.
The project was carried out by researchers at the Laboratory of Space Technology of the Helsinki University of Technology in co-operation with the Finnish Environment Institute, and uses data from NASA’s MODIS spectrometer and the European Space Agency’s (ESA) Envisat MERIS spectrometer. The two satellites have almost daily global coverage, say the researchers.
Envisat – short for Environmental Satellite – was developed by the British National Space Centre and the UK space industry in partnership with the ESA, and was launched on 1 March (see related story).
The sensors measure the sunlight reflected from the water, Jouni Pullianen, Professor at the Laboratory of Space Technology, explained to edie. “This reflected radiation includes a contribution reflected from the impurities inside the water – below the actual water surface,” said Pulliainen. “These impurities may include phytoplankton and suspended solids that are directly related to overall quality of water. Hence, the radiation detected at the satellite sensor includes information on water quality.”
Pulliainen points out that although the human eye detects the same reflected sunlight, it is not absolutely calibrated and cannot distinguish between narrow wavelength bands.
The ability to cover a large area in a single sweep is the most important improvement that can be obtained from using satellite data, say the researchers, and the system can obtain information on regions that would normally not be monitored at all. This is particularly important in boreal regions where the number of lakes is large and the quality of lake water is highly variable, being sensitive to external pollution and climate change. In Finland, for example, there are around 60,000 lakes that exceed 0.01 square kilometres.
The system has also revealed interesting information about the quality of the water in the Gulf of Finland. Turbidity maps have demonstrated the strong influence of the St. Petersburg region on the overall water quality.