Plenary Session 2

A journey through inland water remote sensing from the Nineties to the present

Claudia Giardino, National Research Council of Italy

Inland water ecosystems are crucial environments because they provide vital resources for drinking, irrigation, sanitation, industry and recreation. Many regions of the world are now facing serious challenges to their freshwater resources including reduced water quality and increasing damage to dependent ecosystems. In the past decades the quality of inland waters has been severely endangered and often dramatically degraded. To understand and model this process in order to mitigate the deterioration of inland water quality, the monitoring of bio-physical variables depicting water conditions is essential. For more than three decades, remote sensing has been recognized as an essential technique for water quality monitoring. We have entered an unprecedented era of massive remote sensing data acquisition, including time-series records and real-time data acquired by satellites, aircraft, and other remote sensing instruments with different spectral-spatio-temporal resolutions. Information technology solutions are increasingly applied for transforming data to knowledge, with a variety of public and private services accordingly developed for the water sector.

This contribution aims to describe how this happened by recalling how, almost three decades ago, most of imaging data were not freely available and most of the challenges of inland water remote sensing were still to be tackled. The journey described is based on the experience my team and I have gained over rather a long time, however, thanks to the priceless cooperation with the aquatic remote sensing community, the lessons learned might offer more general conclusions to be drawn. The presentation aims to describe the processing and application of multispectral imagery that we have been acquired by Landsat, MERIS and later on by Sentinel-2 MSI and Sentinel-3 OLCI; next, the advantage of using imaging spectroscopy is presented in parallel with experience with airborne data back in the Nineties, followed by Hyperion and recently by PRISMA. The development steps are mostly presented using Lake Garda as a reference use case. The methods which have been applied to transform satellite data into user-ready products are discussed in view of the typical challenges faced (e.g., atmospheric correction) and a review of remote sensing techniques for mapping and retrieving bio-physical parameters is presented for both optically-deep and optically-shallow waters, as well as for mapping floating materials. A series of uses cases on integration of satellite-derived products to field measurements and modelling for supporting end-user needs is presented, highlighting the most significant results produced by the team (e.g. chlorophyll-a responses to heatwave, exploiting PRISMA for aquatic applications).