Common Implementation Strategy for the Water Framework Directive

WFD CIS Guidance Document No.9
Implementing the Geographical Information Systems (GIS) of the Water Framework Directive
automatically forming unique European identification codes. Examples are provided here in
order to clarify this point.
There may be a number of authorities, such as counties, regions or Länders, responsible for
the establishment of monitoring stations. Each may have sub-authorities such as urban district
councils with similar responsibilities. In such a case, it is useful if coding authorities are first
assigned unique identifiers at Member State level. For example the initial two digits of a four
digit authority code ‘AAAA’ might be used, e.g., ‘4000’, ‘1700’ or ‘2300’. The last two digits
might be used to identify sub-authorities or regional offices. For example ‘1710’, ‘1714’, etc.
These authorities can then easily generate locally unique codes. A local code becomes
nationally unique by the addition of the AAAA code as a header, and internationally unique
by the further addition of the MS code. For example, if a monitoring station is locally given
the unique identifier of ‘12345’ by coding authority 1700 in Denmark, then that station would
be uniquely identified as DK170012345 when reporting to Europe.
This approach is strongly recommended where multiple agencies are, or will be, involved in
the ongoing identification of features. Exact coding structures to be used will be a matter for
individual Member States to decide upon and these are likely to vary by feature type.
3.4.3.2 Unique Identification Coding at Operational Levels
The above technique can be taken further within coding authorities, where appropriate. For
example, if drinking water abstraction monitoring is managed at drinking water scheme level,
then a coding authority may first assign unique identifiers to drinking water schemes. The
scheme managers can then easily assign unique identifiers to monitoring stations at a local
level.
3.4.3.3 Using the River Network for Unique Code Assignments
Once the river network has been uniquely coded, it can be used to assign unique codes to
features that are connected to it. This provides another mechanism for assignment of unique
codes at a local level without having to cross check against national assignments.
River segment identification codes can be used locally to assign unique codes to:
�� river water bodies;
�� lakes;
�� lake water bodies;
�� transitional water bodies; and
�� the monitoring stations for all of these.
As explained later, the outlet river segment code should generally be used for hydrologically
connected features that are associated with multiple river segments.
For example, monitoring stations can be identified with codes that are an extension of river
codes. The first two digits of a 4-digit monitoring station code ‘MMMM’ might be used. The
last two digits could be used at a later stage to allow further stations to be inserted, while
maintaining a sequence to the order of stations. Such a sequence would be important for the
purpose of visual confirmation of uniqueness.
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