Mapping the quality of Europe's inland waters
Regular monitoring of lakes and rivers is essential for both good water quality and a healthy ecology. An EU-funded project has used satellite imagery to create high-resolution mapping services to help countries better manage their inland waters.
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Water supplies are under threat from agriculture (e.g. fertiliser overuse), economic development (e.g. increased pressure on scarce resources) and climate change (e.g. drought). In Europe, the EU’s water framework directive sets out principles for the monitoring of inland and coastal waters with the aim of protecting and improving both their quality and ecological status.
The EU-funded FRESHMON project has now made this job easier by offering satellite mapping services to authorities responsible for monitoring lakes and rivers. With more than half a million natural lakes larger than one hectare, and countless smaller ones, EU countries cannot otherwise maintain surveillance of all their inland waters all of the time.
The project has led to the launch of online subscription services offering high-resolution maps of lakes and rivers showing several indicators of water quality and ecological health. Unlike conventional spot measurements, the maps show how quality varies in time across the area of a lake or along the course of a river.
Measured quantities include chlorophyll – an indicator of algal blooms – suspended material, dissolved organic matter, surface temperature and water depth. Observations are taken from a variety of European and US Earth-observation satellites (notably Envisat/MERIS, Landsat, Spot, MODIS Aqua and Terra), including historical data going back 30 years.
“Countries like Finland or Sweden have a huge number of lakes and water bodies to be monitored and it’s not possible to do this only in situ,” explains project coordinator Thomas Heege, CEO of EOMAP, a German SME specialising in Earth observation services. In such cases, remote sensing can supplement conventional monitoring stations on lakes and rivers.
Although satellite data has been used before, FRESHMON was the first large-scale project to combine remote sensing with local water sampling and mathematical modelling to establish a continuous service for inland waters. Much of the work in the three-year project focused on methods of merging many sources of data to produce results in the form of colour-coded maps.
Field campaigns were run in Finland, Germany, Switzerland and the Netherlands to validate satellite data with local measurements of lakes and rivers. “We coupled satellite imagery with the ‘ground truth’ to build confidence,” says Karin Schenk who heads the water quality section at EOMAP.
The services are provided commercially by FRESHMON partners EOMAP and Brockmann Consult in Germany and Water Insight in the Netherlands. Samples of products are available on the eoApp website.
Although FRESHMON was initially designed for European states and water authorities, the products can be used anywhere in the world. “We have customers in Australia, the US, the Caribbean, the Arabian Gulf and Asia,” Schenk says.
With water supplies under stress in many parts of the globe, comprehensive monitoring of water quality is becoming urgent. “Recent enquiries from water suppliers, dam operators, water agencies and intergovernmental bodies such as the World Bank are evidence of the expected socio-economic impact of our work,” adds Schenk.
Four of the partners are now collaborating in GLaSS, a follow-on project working with richer data from Europe’s expanding Sentinel satellite installation (a collection of satellites equipped for land, ocean and atmospheric monitoring) to further develop remote monitoring of inland waters.