Use constraints: The dataset is public domain and may be used for non-commercial purposes provided that approriate reference is made to the data source

This dataset has been modified by HELCOM from an ESRI shapefile produced by GRID Arendal ( http://grida.no/baltic/index.htm). The amendments made by HELCOM include changing of projection to match that used by HELCOM (Lambert Azimuthal Equal Area, ETRS LAEA 1989) and cutting out of the marine sub-basins.

The following is the data description of the original drainage area dataset downloaded from the GRID Arendal website:

The main Baltic Sea drainage basin map was created by M. Falkenmark and Z. Mikulski (HELCOM 1986). Both map projection and scale are unknown. Independent measurements indicate a scale of approximately 1:5,000,000. Two additional maps were used to provide more accurate delineations in the Danish Straits and Kattegat sub-regions. These paper maps were also of unknown scale and projection.

The Digital Chart of the World (DCW) by ESRI was used for spatial positioning when joining all data sets. These map sources identified 81 sub-basins, which can be aggregated to seven major watersheds for the following major water bodies that define the Baltic Sea: Bothnian Bay, Bothnian Sea, Gulf of Finland, Gulf of Riga, the Baltic Proper, Danish Straits, and the Kattegat.

The main Baltic Sea drainage basin map was digitised and transformed in three separate sections using PC ARC/INFO. The Root Mean Square (RMS) error ranged between 0.01 and 0.02. Four sub-basins from the Danish Straits and nine from the Kattegat paper maps were digitised. The RMS errors were 0.01 and 0.06, respectively.

All sections were joined together using the APPEND command. Although some RMS errors were high, the final drainage basin data set lines up well with other coverages in the database. The coverage was edited for dangling arcs and label errors. When the editing process was complete, topology was created using the CLEAN command with a 20 meter fuzzy tolerance and dangle length.

All polygons were assigned unique id's before attribute data was added. An item called SUBID was added to the coverages .PAT file. This value represents the sub-basin or water body for which each polygon belongs. SUBID served as a bridge item to join additional attributes that existed in an EXCEL spreadsheet. Individual SUBIDs were assigned by selecting polygon label points in ARCEDIT and CALCing SUBID to be the correct value. Extensive error checking was

performed before all other attribute data was appended.

In addition to the added item SUBID, 21 other attributes were appended to the cover .PAT file. These attributes originated from (a) and database of monthly loads of land based eutrophying substances (Stalnache, 1994), (b) data extracted from the Land Cover data set, and (c) data extracted from the Population Distribution data set. The final BASINS coverage has a total of 26 attributes, including the four automatically generated by ARC/INFO.

Publication Reference

Langaas, S. 1993. Some Georeferenced Data Sets for use within Sub-project 1; Land Use and Ecological Carrying Capacity, of the Baltic Drainage Basin Project. Technical Note. GRID-Arendal. 10 pages + apps.

Sweitzer, J., Langaas, S., and Folke, C. 1996. Land Cover and Population Density in the Baltic Sea Drainage Basin: A GIS database. AMBIO, 25(3):191-198.

Stalnacke, P. 1994. Documentation of data sources and data quality in the calculation of the land based loads of eutrophying substances to the Baltic Sea, 1970 - 1990. Note, Dept. of Water and Environmental Studies, Linkoping University. 15 pages (in Swedish/English).

HELCOM. 1986. Water balance of the Baltic Sea. Baltic Sea Environment Proceedings No. 16., The Helsinki Commission, Finland. 174 pages.

In April 2009, the outline of the catchment area was slightly modified to remove areas with rivers that are not part of the Baltic Sea catchment area. This was done by manually amending the borders using as reference a European river and lake data set produced by based on the Digital Chart of the World 1999.