Proceedings 8 th EC – GI & GIS Workshop, 03 – 05 July 2002, Dublin Ireland Development of a pan-European Database of Rivers, Lakes and Catchments, in support to the needs of Environmental Policies. Jürgen Vogt, Roberto Colombo, Maria Luisa Paracchini, Pierre Soille, Alfred de Jager Institute for Environment and Sustainability EC – Joint Research Centre (JRC) 21020 Ispra (Varese), Italy juergen.vogt@jrc.it Abstract The availability of digital data on river networks, lakes and associated catchments and their characteristics is important for the analysis of environmental pressures and their impact on our water resources. Recent policies, such as the Water Framework Directive require the implementation of river and catchment databases for both the development of River Basin Management Plans and for the reporting to the Commission. GIS tools allow for the combined analysis of digital elevation data and terrain parameters in order to derive part of the required information over extended areas. This article presents a new approach making use of medium resolution digital elevation data (250 m grid cell size) and information on climate, vegetation cover, terrain morphology, soils and lithology to derive river networks and catchments for the European continent. Methods to extract channel networks at continental scale normally use a constant threshold for the critical contributing area, independently of widely varying landscape conditions. As a consequence, the resulting drainage network does not reflect the natural variability in drainage density. To overcome this limitation a landscape characterisation is proposed, resulting in a limited number of landscape types reflecting drainage density. For each landscape type the slope-area relationship is then derived from the digital elevation data and the critical contributing area is determined. In the subsequent channel extraction a dedicated critical contributing area threshold is used for each landscape type. In order to comply with the needs of environmental monitoring, lakes and transitional waters are considered during river and catchment mapping. In addition, monitoring stations are accurately positioned on the river reaches and a dedicated algorithm has been developed to overcome problems of automatic river mapping in flat terrain. The described methodology has been developed and tested for the territory of Italy and is now implemented for the pan-European area. Results are validated comparing the derived data with river and catchment data sets from other sources and at varying scales. Good agreement both in terms of river positioning and drainage density could be demonstrated.