science

Gewässerkennzahl

Gewässerkennzahl is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gewässerkennzahl rather than just read about it. In short: The Gewässerkennzahl (GKZ, rarely GWK or GEWKZ) or "waterbody index number/waterbody number" is an identifier with which all watercourses in Germany are numbered, together with their catchments and precipitation areas. It is also referred to as a Gebietskennzahl or "basin number".

Key takeaways

Gewässerkennzahl belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gewässerkennzahl to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gewässerkennzahl from memory before moving on to harder problems.

Reference excerpt

The Gewässerkennzahl (GKZ, rarely GWK or GEWKZ) or "waterbody index number/waterbody number" is an identifier with which all watercourses in Germany are numbered, together with their catchments and precipitation areas. It is also referred to as a Gebietskennzahl or "basin number". A Gewässerkennzahl may have up to 13 figures (theoretically even 19). Basins normally are only defined up to seven figures. For a more detailed subdivision, the Gewässerkennzahl may be enlarged by ten more figures. Only that enlarged version is called Fließgewässerkennziffer. The Gewässerkennzahlen are defined by the environment offices of the states.

History In order to have comparable values and usable data across the state of Germany, the Federal and State Water Authorities agreed in December 1970 to create a unified system for hydrological work on certain important rivers and their above-ground catchment areas and to issue them with index numbers. Linked to that was the establishment of the size and boundaries of their catchment areas.

Principle Every waterbody (streams, rivers, canals and ditches, but also lakes and even some bays) and its catchment area was given a waterbody number in such a way that it could be clearly identified. The waterbody numbers are built in hierarchical fashion so that, based on the number, the next river system of the waterbody can be deduced.

Scheme At first the course of water has to be defined from source to mouth. Then the four major tributaries (or 'affluents') are identified. They are marked by even figures in downstream sequence, "-2, -4, -6, -8". This way, the (main) course is divided into five sections, which are marked by odd figures, "-1, -3, -5, -7, -9". A number with an even end-digit is the number of a whole watercourse, while a number with an odd end-digit is the number of a section. Lowest sections are always given a nine, even if not all figures between one and nine have been used. In the next step of numbering, each section defined by the first step is dealt in the same way, selecting four major tributaries and marking five sections.

Lakes Lakes are integrated as a part of the watercourse formed by their main tributary and their outlet.

Coastal regions For coastal regions, the scheme of numbering was altered in different ways by different states:

Lower Saxony left the rule of using only odd numbers for sections. Nevertheless, bay as dependent waterbodies got even numbers. Mecklenburg-Vorpommern stuck to using even numbers for important rivers and odd numbers for – here coastal – sections in between. But the course of the coast was defined in a way, that in two straits different third figures were used for their two banks.

Waterbodies without a Gewässerkennzahl Some waterbodies indexed under this classification system have un-indexed headstreams or lateral tributaries in the form of very small streams or ditches. If such an unclassified waterbody is relevant for the water management of the region, it may be given a number within the local classification system of the regional Wasser- und Bodenverband (association for water and ground management).

Catchment areas The numbers for a watercourse and its catchment area are thus identical. If a river has subsidiary watercourses, an additional figure is allocated to its index number for each further branch. So in theory even a rivulet could be allocated its own catchment. In practice, catchment numbering for water sources below the level of streams is not used. Catchment areas are thus distinguished by a number with up to a maximum of seven digits. Watercourse index numbers, by contrast, may have up to 13 digits in order to be able to classify all their tributaries and headstreams; although in practice only 10 digits are used.

Main river systems The first digit of the number indicates which major river basin the waterbody belongs to, as follows:

1 Danube 2 Rhine 3 Ems 4 Weser 5 Elbe 6 Oder 9 Coastal region The second and subsequent digits of the index number represent further subdivisions of the river and its catchment area.

Example The Heusiepen stream in Remscheid has waterbody number 27366462. This can be decoded as follows:

Main stem system / catchment area Rhine (2) → River system / catchment area Wupper (2-736) → River system / catchment area Morsbach (2-736-6) → River system / catchment area Gelpe (2-736-6-4) → River system / catchment area Saalbach (2-736-6-4-6) → Stream without defined catchment area Heusiepen (2-736-6-4-6-2)

Waterbody index numbers Listed below are all the rivers with up to a three-figure index number, and some rivers with four-figure numbers above a length of 50 km.

1 Danube

2 Rhine

3 Ems Here some three-figure numbers are not listed.

4 Weser

5 Elbe

6 Oder

9 Coastal region

Literature Landesamt für Wasser und Abfall Nordrhein-Westfalen (publ.): Gebietsbezeichnung und Verzeichnis der Gewässer in Nordrhein-Westfalen

See also Waterbody index number – an overview Stream order, hydrological hierarchy of rivers and streams

References

External links Bund-Länder Arbeitsgemeinschaft Wasser (LAWA) Erläuterung der Gewässerkennzahl im Bayerischen Landesamt für Umwelt Archived 2014-01-10 at the Wayback Machine

Worked examples

Example 1 — a first encounter with Gewässerkennzahl

Start with the simplest possible case. Write down what Gewässerkennzahl claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gewässerkennzahl before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gewässerkennzahl ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gewässerkennzahl

In research: Gewässerkennzahl appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gewässerkennzahl in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gewässerkennzahl is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bodies of water of Germany, Hydrology, Identifiers, so understanding it makes those chapters shorter.
In everyday life: Look for Gewässerkennzahl outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gewässerkennzahl in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gewässerkennzahl means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Gewässerkennzahl out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gewässerkennzahl in simple terms?

Why does Gewässerkennzahl matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gewässerkennzahl?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gewässerkennzahl.