POSTER Session 3

GENERATING WATER QUALITY PRODUCTS FOR INLAND WATERS AT A COUNTRY SCALE: A HYBRID APPROACH FOR A FUTURE SURVEILLANCE SERVICE OF FRENCH TERRITORIES

Water quality evaluation is a keystone to achieve United Nations Sustainable Development Goal No.6 to “ensure availability and sustainable management of water and sanitation for all”. Our efforts were focused on the reliability of generating water quality products at a country scale, namely: clarity, chlorophyll-a (Chl-a), sediment or CDOM concentrations, aiming that the largest number of end-users adopt such data. We performed the first extensive matchups exercise on inland waters of France (>700 over >100 water bodies) and combined spectral classification (Optical Water Types) with quantitative assessment of bio-geo-chemical (BGC) parameters. Inland waters represent a challenge as they are optically complex, and our results demonstrate the improvement of adopting a hybrid approach. First we better apprehend the performances of empirical, analytical and deep learning methods for quantitative retrieval of BGC parameters in each type of water. Our data-driven approach validated the broad applicability of generic algorithms for the retrieval of clarity and Chl-a with less than 50% error overall. We also criticize the discrepancies observed thanks to OWT classification, allowing to constrain uncertainties estimation in each spectrally analog environment. We also highlight the need to improve atmospheric corrections (displaying up to 30% error) and to better correct adjacency effects that affect ~20% of the scenes investigated. Finally, in the aim of using satellite data for the Water FrameWork Directive implementation, our results are encouraging since the state classes of water bodies investigated are identical to those assessed using in situ data in 76% of cases.

Guillaume Morin, National Research Institute for Agriculture, Food, and Environment (INRAE), France, [email protected], https://orcid.org/0000-0002-1288-0127

Tristan Harmel, Magellium, France, [email protected]

Nathalie Reynaud, National Research Institute for Agriculture, Food, and Environment (INRAE), France, [email protected]

Thierry Tormos, Office français de la biodiversité (OFB), France, [email protected]

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