Remote sensing of inland waters: Challenges, progress and future directions

Monitoring and understanding the physical, chemical and biological status of global inland waters are immensely
important to scientists and policy makers alike.Whereas conventional monitoring approaches tend to be limited
in terms of spatial coverage and temporal frequency, remote sensing has the potential to provide an invaluable
complementary source of data at local to global scales. Furthermore, as sensors,methodologies, data availability
and the network of researchers and engaged stakeholders in this field develop, increasingly widespread use of
remote sensing for operational monitoring of inland waters can be envisaged. This special issue on Remote Sensing
of Inland Waters comprises 16 articles on freshwater ecosystems around the world ranging from lakes and
reservoirs to river systems using optical data from a range of in situ instruments as well as airborne and satellite
platforms. The papers variably focus on the retrieval of in-water optical and biogeochemical parameters as well as
information on the biophysical properties of shoreline and benthic vegetation.Methodological advances include
refined approaches to adjacency correction, inversion-based retrieval models and in situ inherent optical property
measurements in highly turbid waters. Remote sensing data are used to evaluate models and theories of environmental
drivers of change in a number of different aquatic ecosystems. The range of contributions to the special
issue highlights not only the sophistication of methods and the diversity of applications currently being developed,
but also the growing international community active in this field. In this introductory paper we briefly
highlight the progress that the community has made over recent decades as well as the challenges that remain.
It is argued that the operational use of remote sensing for inland water monitoring is a realistic ambition if we can
continue to build on these recent achievements.