Freshmon-Establishing Downstream Services for Inland Waters based on ENVISAT, Sentinel 2+3 and Third Party Mission Data
Stelzer, Kerstin1; Schenk, Karin2; Koponen, Sampsa3; Poser, Kathrin4; Geissler, Jasmin1; Block, Thomas1; Kleih, Christoph2; Heege, Thomas5; Brockmann, Carsten1

National and European authorities responsible for inland water quality in rivers and lakes are faced with problems that can be mitigated by remote sensing. In the framework of the Water Framework Directive, lakes larger than 50ha have to be monitored for assessing their ecological status. Referring to literature, lakes should have a minimum size of approximately 150 ha, also depending on the shape, to retrieve a water signal with good quality from 300m MERIS Full Resolution or future OLCI pixels. For the application within smaller lakes, rivers and small-scale applications, high resolution sensors such as Landsat (E)TM or WorldView are used and we expect excellent applicability from the future Sentinel-2 data. Products from high resolution data focus on water depth and turbidity while medium resolution data are utilized for large archive processing including time series extraction for chlorophyll concentration, suspended matter, CDOM and turbidity.
Retrieval of water quality parameters of optically complex waters from spaceborne measurements is challenging. It requires a good knowledge of the bio-optical model of the water body in order to obtain a good inversion of the water leaving reflectance, and beforehand it requires an accurate pre-processing to invert of the top-of-atmosphere measurements into water leaving reflectances. This is especially true for inland waters.
FRESHMON, an EU collaborative project, provides products for Freshwater Monitoring and Services. The main objectives are continuous and well accepted downstream services for inland water monitoring at European level. The Service Portfolio consists of Water Quality Products such as Total Suspended Matter, Turbidity, Chlorophyll, Yellow Substances, and further water depth and lake bottom classification. Thus, a new service-line for the continuous provision of Earth Observation based products, integrated with in situ and hydrodynamic modeling components, for water quality monitoring is developed.
A service infrastructure with harmonized metadata and service provider specific processing chains has been established. Improved preprocessing leads to reliable products and enhanced the automatisation and operationalisation of the services, however, final quality control remains important. Valdiation is performed using in situ data and performing intercomparison of different products. Extraction of time series enable an assessment of the quality of products and in combination with in situ data provides a valuable product for users.
FRESHMON is a FP7 GMES Downstream project that has started on 2010-12-01 with duration of 36 months. FRESHMON is part of the FP7 Call SPA.2010.1.1.01. The project is led by EOMAP, Germany, the consortium is built by Brockmann Consult, Water Insight, SYKE and EAWAG.