Water code (Finland)
The water body identification number (GKZ) is an identifier that is used to number all bodies of water in Finland .
There are 74 large catchment areas in Finland with a size of at least 200 km². These are numbered from 1 to 74, starting with the river systems in the south-east that flow into Lake Ladoga and continuing clockwise. Smaller catchment areas that are located on the coast between the larger river systems or extend along the Finnish national border are numbered 81 to 86. Other catchment areas in marine areas are numbered 91 to 99. The main catchment areas or river systems are also subdivided accordingly.