Broad typology for rivers and lakes in Europe for large scale analysis

Typology of waters is defined as a group of water bodies having common natural ecological conditions in terms of geo-morphological, hydrological, physico-chemical, and biological characteristics. The type descriptors are permanent characteristics that do not respond to human activities and represent the fixed abiotic conditions that explain natural variability. For the need of large-scale analysis of ecological status, multiple pressures on rivers and lakes, linkages of water body types to habitat types and for comparison of type-specific limit values for nutrients and other quality elements across countries in Europe, a broad river and lake typology was developed. Descriptors categories are dominant geology, region, river catchment, river altitude, river flow, lake size and mean lake depth. The ranges of descriptors largely follow the system A of Water Framework Directive (WFD) (EC, 2000) and are described in Lyche Solheim et al. (2019).

Various European data sources were used for spatial allocation of rivers and lakes broad types. The starting point was the European Catchments and Rivers Network System (Ecrins) (EEA, 2012), which is organised into sets of spatial thematic layers: lake polygons, river segments (drains), nodes representing intersection of river and catchments and almost 180,000 “Functional Elementary Catchments (FECs)”. Catchments include “main drains” (connecting together the FECs) and “secondary drains” (internal within a FEC). We assigned one broad type to all segments belonging to “main drain” of each FEC and named them “river segment".

The catchment size of river segments in each FEC is defined as the sum of the upstream drainage area and FEC surface area. The upstream drainage area has been derived using data in “Code Arbo” in Ecrins database (Globevnik et al., 2017). The altitude of the lower end points of river segments in each FEC is available in Ecrins river database. Lake surface area is obtained from Ecrins lake area attribute “Area”. Data on mean lake depth were obtained from Waterbase – Water Quality database (EEA, 2016) or estimated from terrain data. The basic map of five geological (geochemical) categories was produced from two thematic maps: bedrock map “International Hydrogeological Map of Europe (IHME 1500_v11)” (Dutcher et al, 2015) and the soil map of the European Union “SGDBE4” (JRC, 2016). The dominant geology for lakes was derived from this map with the overlay procedure. For each FEC we then defined dominant catchment geology (geochemistry) and assigned this geology type to all river segments forming the FEC's main drain. Spatial extent of the Mediterranean region is obtained from spatial layer 'Biogeographical regions of Europe» (EEA, 2019). More details on methodology are in Lyche Solheim et al. (2019).