This European Standard is applicable to lakes, which are water bodies occupying one or more basins with surface areas greater than 1 ha (0,01 km2) and maximum depths (at mean water level) greater than 1 m. All types of permanent lakes, including natural, modified and artificial, fresh water and brackish, except for those systems which regularly connect to the sea, are included in this European Standard, though canals are excluded. Based on these criteria it can be estimated that there are at least 500000 natural lakes across Europe, most of which are located in the glaciated landscapes in northern and western provinces and in Scandinavia. Lakeland districts also occur locally in areas such as the Danubian plain and around the Alps. Elsewhere naturally occurring lakes are relatively sparse and in such areas reservoirs or pits are more common. This European Standard is designed to: a) support environmental and conservation agencies in meeting the monitoring requirements of the WFD (Article 8, Annex II and Annex V); b) generate data sets appropriate for monitoring and reporting of Natura 2000 sites designated under the Habitats Directive and the Birds Directive; c) provide information supporting other environmental reporting requirements (e. g. in relation to biodiversity or environmental impact assessment); d) support lake management and restoration initiatives. This European Standard: e) defines the key term of `hydromorphology' and other terms relating to the physical characteristics of lakes and their hydrological regimes; f) details essential features and processes of lakes that should be characterised as part of a hydromorphological survey and for determining the hydromorphological condition of a lake; g) identifies and defines the key pressures affecting European lakes; h) provides guidance on strategies for collecting hydromorphological data depending on resources available and the anticipated use of the assessment; a hierarchy of approaches is recognised from the `overview method' utilising existing databases, maps and remote sensing data through to recognised field-based survey techniques such as Lake Habitat Survey (LHS); i) offers guidance on data presentation; j) establishes guidance on data quality assurance issues. This European Standard does not deal with biological assessments in lakes such as the presence or absence of individual species or community composition, nor does it attempt to link specific hydromorphological features with their associated biological communities or to create a classification based on such links. However, it is relevant where plants or other organisms form significant structural elements of the habitat (e. g. a gradation from riparian to littoral vegetation). With respect to the WFD, the hydromorphological condition of a lake only contributes to its status classification at high ecological status (HES). Hydromorphological conditions are not defined for good and moderate status but shall be sufficient to support the biological elements.