Gewässerkennzahl

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 Gewässserkennzahl

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 by 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 are 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:

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
Number Name Length
[km]		 Catchment area
[km²]
1 Danube 2857 817,000
112 Lauchert 60.3 456
114 Iller (including the Breitach - Turabach) 147 2,147
1158 Günz 55 710
116 Mindel 81 962
1172 Brenz 52 880
118 Wörnitz 132 1,686
12 Lech[1] 264 3,926
122 Archbach (river totally in Austria, basin partly in Germany) 10 145
124 Vils 36 198
126 Wertach 150 1,260
128 Lechkanal 14 19
132 Friedberger Ach (with Hagenbach–…–Verlorener Bach) 100 [2] 598 [2]
134 Paar 134 1,632
136 Abens 72 [2] 1020 [2]
138 Altmühl 234 2,251
14 Naab (including the Waldnaab) 165 5,432
142 Haidenaab 60 714
144 Pfreimd 56 595
146 Schwarzach 80 822
148 Vils 78 1,100
152 Left branch of Danube in Regensburg 3,6 2.881 [3]
1522 Regen 103 2,953
154 Pfatter 37 262
156 Große Laber 75 407
158 Kinsach–Ferchenbach 38 317
16 Isar 295 8,370
162 Loisach 113 954
164 Amper (with Ammer, Linder, Fischbach, Rückentalbach) 209 3,248
166 Mittlerer Isarkanal (Middle Isar Canal) 64,7 1,147
168 Plattlinger Mühlbach (with Längenmühlbach) 75 345
172 Hengersberger Ohe (with Ranzlinger Bach) 34 198
174 Vils (including the Großer Vils) 110 1,445
176 Große Ohe (with Geißa–…–Geißleitenbach) 46 176
178 Ilz 62 850
18 Inn 517 26,130
182 Mangfall (including the Weißach) 58 1,099
184 Alz (including the Tiroler Achen) 150 2,197
186 Salzach 225 6,700
188 Rott 109 1,205

2 Rhine
Number Name Length
[km]		 Catchment area
[km²]
2 Rhine 1239 185,300
215 Lake of Constance: Obersee (GKZ: 215 – 217)
5,386
217 Lake of Constance: Untersee
232 Wiese 55 458
234 Kinzig 93 1,406
236 Murg 80 466
238 Neckar 362 13,934
24 Main (including the White Main) 572 27,292
242 Regnitz (including the Rednitz) 162 7,523
244 Franconian Saale 139 2,765
246 Tauber 129 1,810
248 Nidda 90 1,942
252 Selz 61 389
254 Nahe 125 4,067
256 Wisper 30 209
258 Lahn 246 5,925
26 Moselle 544 28,286
262 Sauer 173 4,259
264 Saar 235 7,431
266 Kyll 142 845
268 Alf 52 358
272 Sieg 155 2,857
274 Erft 107 1,838
276 Ruhr 219 4,485
278 Lippe 220 4,888
28 Meuse 874 33,000
282 Rur 165 2,361
284 Schwalm 35 268
286 Niers 118 1,381

3 Ems

Here some three-figure numbers are not listed.

Number Name Length
[km]		 Catchment area
[km²]
3 Ems 371 13,160
316 Hessel 39 213
318 Bever 39,5 217
32 Werse 67 762
332 Münstersche Aa 43 172
34 Große Aa 25 922
36 Hase 170 3,086
38 Leda (with Ohe u. Sagter Ems) 75 1.917
388 Jümme (with Barßeler Tief & Soeste) 94 450
394 Oldersumer Sieltief (with Fehntjer Tief (North) & western Flumm) 26 235
397 Dollard (as a section of Ems estuary)
3974 Dollard (as a bay of Ems estuary)
398 Knockster Tief (with Wiegoldsburer Riede) 31 1351
399 Outer mouth of Ems River

4 Weser
Number Name Length
[km]		 Catchment area
[km²]
4 Weser 451 41,094
41 Werra 300 4,497
412 Hasel 26 331
414 Ulster 57 421
416 Hörsel 55 784
418 Wehre 36 452
42 Fulda 221 6,947
422 Fliede [4] 22 271
424 Schlitz (river) (including Altefeld, own GKZ 4241)[4] 43 315
426 Haune 67 500
428 Eder 176 3,361
432 Schede 13 49
434 Nieme 17 40
436 Schwülme 29 290
438 Reiherbach 10.5 35
44 Diemel 111 1,762
44 Diemel 111 1.762
442 Hoppecke 35 92
444 Twiste 41 447
446 Warme 33 157
448 Esse 28 192
452 Nethe 50 460
454 Lenne 24 125
456 Emmer 62 535
458 Exter 26 109
46 Werre 72 1,485
462 Bega 44 377
464 Aa (including Johannisbach) 44 377
466 Else 35 416
468 Rehmerloh-Mennighüffer Mühlenbach 16 71
472 Bückeburger Aue 39 173
474 Gehle 27 163
478 Steinhuder Meerbach 29 356 [5]
476 Große Aue 85 1,522
48 Aller 260 15,744
482 Oker 128 1,834
484 Fuhse 98 918
486 Örtze (including Aue & Wietze) 70 760
488 Leine 281 6,512
492 Ochtum (including Süstedter Bach) 45 917
494 Wümme 118 1.585
496 Hunte 189 2,785
498 Lune 43 383 [5]

5 Elbe
Number Name Length
[km]		 Catchment area
[km²]
5 Elbe 1094 148,268
5281 Mže 103 1,829
532 Ohře 316 5,614
538 Black Elster 179 5,705
54 Mulde (Zwickau + United Mulde) 314 7,400
541 Zwickau Mulde 167 2,352
542 Freiberg Mulde 124 2,981
549 Vereinigte Mulde (United Mulde) 147 7,400, own 2,067
56 Saale 413 23,719
562 Loquitz 34 364
564 Unstrut 192 6,364
566 White Elster 257 5,154
568 Bode 169 3,229
572 Nuthe 39 509
574 Ehle 40 ?
576 Ohre 103 1.503
578 Tanger 33 480
58 Havel 334 23,858
582 Spree 400 10.100
584 Nuthe 52 1,935
586 Plane 57 639
588 Rhin 129 1,780
592 Elde 208 2,990
5934 Jeetzel 73 1.928
594 Ilmenau 107 2,852
5956 Alster 56 581
5958 Este 62 364
596 Lühe (including Aue) 44 216
5974 Stör 78 1.781
598 Oste 153 1,711

6 Oder
Number Name Length
[km]		 Catchment area
[km²]
6 Oder 866 118,861
674 Lusatian Neiße 254 4,297
696 Western Oder       17 (in Germany)

9 Coastal region
Number Name Length
[km]		 Catchment area
[km²]
928 Issel 82 1,208
934 Western Ems
94 Coastal seas between Borkum and Sahlenburg mudflat
942 Jade Bight
95 Coastal seas between Sahlenburg mudflat and the Danish Border
952 Eider 188 3,275
96 Baltic Sea
962 Trave 114 2,676
964 Warnow 155 3,324
9652 Recknitz 88 669
966 Peene 136 5,110
9664 Tollense 96 1,829
9666 Trebel 87 956
968 Uecker (upper section Ucker) 98 2,200

Literature
  • Landesamt für Wasser und Abfall Nordrhein-Westfalen (publ.): Gebietsbezeichnung und Verzeichnis der Gewässer in Nordrhein-Westfalen
gollark: The main datastructure is... hair forests, somehow?
gollark: Esohairlang, yes.
gollark: So we don't know if they have those properties.
gollark: Well, yes, it could be faked, or of someone else.
gollark: Hmm, so now I know that you have width, height, and also hair.

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

References
  1. LFU Bayern, Gewässerverzeichnisse → Lech (PDF)
  2. LfU Bayern, Gewässerverzeichnisse → Flussgebiet Lech bis Naab
  3. LfU Bayern, Gewässerverzeichnisse → Donau von der Naab bis zur Isar
  4. Staatsanzeiger für das Land Hessen, Nr. 63
  5. Umwelt Niedersachsen – Liste Weser
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