Definition: Estuaries, river mouths

Category: Regional statistics

Estuaries are normally regarded as part of the sea. The exact delimitation of river mouths (where the river ends and the estuary begins) will be left to member states. Since land area is proposed as the surface area concept, it does not matter so much how estuaries are classified. If, nevertheless, total area is used by a country, or rivers are not excluded from land area, the definition of estuaries is of some importance for the calculation of surface area. Metadata regarding the handling of estuaries should be provided.
If rivers are included in total surface area and the sea is not, a boundary has to be drawn where the rivers meet the sea. At estuaries there may be quite large areas which could be defined either as river or as sea, but in other cases the areas affected are comparatively small. The definitions of estuaries are left to the countries. For example, there could be width thresholds (at both ends) or there could be definitions taking the mixture of fresh and salt/brackish water into account. Descriptions on how estuaries are defined and classified should be submitted together with the data.