Chlorophyll-a concentrations were derived from the complete archive of Sentinel-2 imagery available over the Oder River using a retrieval algorithm based on Case 2 Regional CoastColour (C2RCC) processing. For each valid Sentinel-2 observation, estimates were spatially aggregated to hydrographic polygons derived from OpenStreetMap, including approximately 1-km-long river-network segments and individual water-body polygons representing lakes, ponds, reservoirs, and other lateral water bodies. The dataset includes summary statistics of chlorophyll-a concentration and the number of valid water pixels contributing to each spatial aggregation.
Satellite observations are irregular because their availability depends on the Sentinel-2 acquisition schedule, cloud cover, atmospheric conditions, and the identification of valid water pixels. Two additional gap-filling approaches, a moving-average interpolation and a 17th-order polynomial fit, were applied to individual spatial-unit time series to represent daily chlorophyll-a dynamics between valid satellite observations.
Users should refer to the accompanying README and data dictionary files for further information on spatial-unit identifiers, data processing, variable definitions, known limitations, and intended uses.
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