River type

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The river type is used to characterize rivers . In view of the variability of the natural waters (from the spring trickle to the large river, from the rapidly shooting mountain stream to the sluggish moorland ) it is difficult to give common characteristics. Typing should help to identify groups with common ecological properties; these are important for renaturation , for example . The typifications are pragmatic and can vary depending on the question. The colloquial designation of a body of water as “brook”, “river”, “trickle”, “lake” etc. is an example of a typification.

Typing

Various formalized typing systems based on defined criteria are in use.

In the German-speaking world, when people talk about types of flowing water today, they usually mean the typification scheme based on the European Union's Water Framework Directive .

River types according to the Water Framework Directive

With the Water Framework Directive , in principle, all European bodies of water are to be brought into "good ecological status". The biocenosis of the water plays a major role in defining this condition . Among other things, the fish fauna , the macrozoobenthos , the higher aquatic plants ( called macrophytes ) and the diatoms are evaluated .

This community is now naturally very different in different rivers. For the definition of “good status”, river types were therefore standardized, for each of which reference conditions and reference communities were determined and established. The same community could therefore be changed in a certain body of water as type-appropriate and therefore “good”, in another body of water that has been assigned to a different type, as anthropogenic and thus classified as “not good”.

The guideline in Annex II prescribes the classification as the basis for the assessment. It provides various options from which the member states can determine a regionally appropriate assessment basis themselves. The classification is based on the following categories (Appendix II, Section 1.2): 1. Altitude. A distinction is made between higher elevations:> 800 m, middle elevations: 200 to 800 m, lowlands: <200 m 2. Size (based on the catchment area ). A distinction is made between: small: 10–100 km², medium-sized:> 100 to 1000 km², large:> 1000 to 10,000 km², very large:> 10,000 km² 3. Geology. A distinction is made between: chalky, silicate, organic.

The scheme on which the German typification is based is based on a (unpublished) report by Schmedtje et al. 2000. Otto + Braukmann (1983), for example, had done important preliminary work. After several revisions, the current classification scheme comes from Pottgiesser + Sommerhäuser (2008). It is laid down in a “working aid” from the LAWA, according to which the experts in the federal and state levels coordinate their approach. At the end of 2018, the Federal Environment Agency published an updated description of the types of water

According to this, twenty-three types are distinguished in Germany; some of them are still broken down into subtypes. The basis of the typification is the biocenotic "ecoregion" (according to Illies). Germany essentially has a share in 3 ecoregions: Alps (region 4), “central low mountain range ” (region 9), “central lowlands ” (region 14). The small shares of Western European regions 8 and 13 (west of the Rhine) are added to the neighboring regions. Typing within the regions is based on hydrological parameters and bed substrate (depending on the geology of the catchment area, for example carbonate or silicate ). A number of very different special types were also added. These are, for example, lake outlets, so-called “organically shaped” streams and rivers (meaning moor waters with peaty bottoms ) or brackish water- influenced waters in the Baltic Sea region . The subdivision of the rivers was made according to the classification in the Water Framework Directive , taking into account the size of the catchment area:

  • Bach = catchment areas between 10 and 100 km²,
  • Small river = catchment areas between 100 and 1,000 km²,
  • Large river = catchment areas between 1,000 and 10,000 km²,
  • Electricity = catchment areas larger than 10,000 km².

It should be noted that this is not an official “redefinition” of the terms stream , river and stream , but a pure classification according to key data. In addition, of course, there are also rivers with a catchment area smaller than 10 km² “streams”. In principle, these waters are also covered by the Water Framework Directive. However, the Federal Republic of Germany has no obligation to notify the European Union. Therefore they were neglected in the typing.

The definition of the river types according to the approach described here takes place “from top to bottom” (or “top down”). This means: bodies of water with recognizable different hydrology and different substrates are classified over a large area (more or less according to the map) without their settlement actually being known in detail. Limnological research that started from the community of carefully examined individual bodies of water (approach “from the bottom up”, or “bottom up”) found e.g. Sometimes different communities in these types of water. In other cases no differentiation was found.

Why are river types needed?

The Sempt in Bavaria, river type: 2.2.

The flowing waters differ significantly in their shape, the runoff behavior and the composition of their communities. The main factors for this are climate, relief and the substrate, which is dependent on the parent rock and its weathering products. The waters also react differently to human impacts. In order to be able to describe the various flowing waters more precisely, a classification into types was made, which is based on the factors geology, geomorphology and the natural spatial order (ecoregion). The knowledge of the different types is important for u. a. significant for the following questions:

  • Renaturation of degraded rivers. In the case of renaturation (sometimes also referred to as "near-natural reconstruction"), bodies of water should be aimed for that come as close as possible to the characteristic natural state of unaffected bodies of water in the flowing water region. Without typing, there is a tendency to neglect natural differences.
  • Assessment of the water status: For assessment, e.g. B. in the context of the Water Framework Directive, the actual condition of the examined stretch of water is to be compared with a reference which would correspond to the optimal condition. This varies depending on the type.
  • Assessment of the saprobial status: The various types of water naturally differ slightly in terms of their organic matter content. Since this, as saprobia, is measured via the composition of the community and used as a parameter for pollution, these differences are important for the assessment. Without typing, waters with naturally higher saprobicity are rated too poorly. On the other hand, water pollution can be underestimated with naturally very low saprobic activity.

What types of rivers are there?

For Germany, the factors mentioned result in 23 types of flowing water. Two of them are subdivided into two or three sub-types, so that a total of 25 types can be distinguished. They can be assigned to four ecoregions. These are the ecoregions:

Also exist

  • Ecoregion independent types.

In principle, these can occur equally in each of the three ecoregions. Here certain key factors shape the community so strongly that the differences between the ecoregions are meaningless in relation to them.

A single river can belong to several types in its longitudinal course if it flows from one river region to another, or if it changes from a "smaller" type (stream) to a "larger" (here, measured as an enlargement of the catchment area) by increasing the runoff River). This occurs very often in practice. The typification therefore does not refer to the body of water as a whole, but only to the characteristic sections. When settling rivers, it is observed in practice that the influence of the type located above is still noticeable for a longer distance in the one below (e.g. increased lime content in a stream flowing from a catchment area characterized by carbon into a siliceous area ). This effect is not taken into account in the typing.

The river types

A distinction is made between the following types:

Types of the Alps and the Alpine Foreland

The Inn , river type 4

The German Alps can be divided into two height levels with different shapes, which have a great influence on the flowing waters: An upper floor of the periglacial frost debris zone, in which a lot of mechanically crushed rock material is made available due to frequent changes in frost. This high level begins at about 1800 m. In the lower fluvial level (Alpine foothills) the rubble, which is often still very coarse, is fed to the larger bodies of water. Very structured, rapidly changing waters are typical for this area.

Overall, the alpine region is characterized by heavy erosion, especially fluvial erosion. In the longitudinal profile of the flowing waters, there are not only different valley shapes, but also very pronounced gradient differences: The type 1 waters are laid out on the slope of the slopes and are highly erosive flowing waters. They have gradient values ​​of 20% to 40% or higher. The waters of type 2 and 3 represent collecting arteries for the waters of type 1. They are laid out in glacial valleys and flow in large notch and notched valley valleys, which have average gradient values ​​between 2% and 8%, but at the transition to hanging valleys the main valleys and breakthroughs achieve far higher values. The larger waters of type 3 and 4 follow the main glacier railways (trough valleys) that break through into the foothills of the Alps. Except for very short breakthroughs, they filled these glacial gullies with coarse gravel. These are waters with predominantly transit and accumulation. The valley slope usually falls below 1%.

  • Type 1: rivers of the Alps
    • Subtype 1.1 .: Brooks and small rivers of the Limestone Alps
    • Subtype 1.2 .: Large rivers of the Limestone Alps
  • Type 2: flowing waters of the Alpine foothills
    • Subtype 2.1 .: streams of the Alpine foothills
    • Subtype 2.2 .: Small rivers of the Alpine foothills
  • Type 3: flowing waters of the young moraine of the Alpine foothills
    • Subtype 3.1 .: Brooks of the young moraine of the Alpine foothills
    • Subtype 3.2 .: Small rivers of the young moraine of the Alpine foothills
  • Type 4: Large rivers of the Alpine foothills

Types of low mountain ranges

Aurach , river type 9.1.

This region is characterized by very varied river landscapes. The low mountain ranges rise from about 150 m to over 1400 m, with only a few reaching a height of over 800 m. The low mountain ranges were glaciated over 900 m in the cold ages. In this high level, the glacial overforming by carving has left a rather alpine, steeper relief, while the low mountain ranges are otherwise characterized by plateaus. Due to the tectonic stress, it is a small-scale mosaic of broken clods that were moved to different altitudes. The waterways are very often graded in their longitudinal profiles: they first flow a stretch in hollow and bottom valleys on the surfaces and then descend with often very steep inclines and notch valleys in harder layers and then flow further in notched valley valleys with narrow floodplains. The low mountain ranges consist of very old, metamorphic and crystalline rocks, the basement, which is overlaid by younger, stratified rocks, the overburden. The basement consists of granites, gneiss and slate, which means that the water-morphologically harder substrates than the overburden. The layer structure of the overburden has rocks of very different hardness.

Types of the North German lowlands

The North German Plain is covered for the largest part by glacial (moraine embankments) and fluvioglacial (sand and other meltwater embankments) deposits from the cold ages.

Lippe , river type 15

Ecoregion-independent types

Wümme , river type 11

Hydromorphological differentiation

Graininess

River types are defined by the granularity of the substrates of river beds and floodplains. Coarse material leads to structural abundance and wide streams, while fine material leads to poorly structured, steep and smooth banks as well as deep waters.

Basically four main types according to the size of the grains to distinguish

  • the stony (63 - 200 mm) and blocky (> 200 mm), or lithal type,
  • the gravel (2 - 63 mm), or acale type,
  • the sandy (0.063 - 2 mm), or psammal type,
  • the silty (0.002-0.063 mm) and clayey (<0.002 mm), or pelal types.

Depending on the petrographic equipment of the catchment areas, this results in a variety of mixed types. However, mostly only very specific grain size mixtures are widespread, which are dependent on the substrates and their size and the gradient of the water, so that only three main abiotic mixed types can be recognized:

  • the stony / blocky of the sloping mountain streams and steep upper reaches,
  • the sandy / gravelly of the larger and larger bodies of water as well as the middle reaches of the mountain streams,
  • the loamy one of the low-slope lowland brooks.

Floodplains

Rheinaue in winter

Almost all flowing waters are accompanied by floodplains as flat parts of the terrain. Only the short erosive headwaters of the channels are not accompanied by them, so they have no fluvial sediments. Meadows form an independent landscape from a width of more than 300 m. Then they are no longer directly influenced by the surrounding terrain. Floodplains are created either by flooding the valley floors or by constant shifting of the waters. Flat and wide bodies of water with a lot of coarse debris are shifting due to local ballast of the channel beds or due to blockage with dead wood and sediment backlog. The associated breakouts are signs of overload. The most common floodplain formation, however, occurs when the valley floors are flooded. Usually fine materials and sand are then transported to the valley floors (alluvial clay formation). Gravelly flood plains can also be observed in larger bodies of water. There are five types of floodplain in nature that create their own landscapes:

  • Fine material meadows with clay / heavy loamy structures (for example in Keuper southern Germany, Altmühl),
  • Floodplains with gravelly, loamy, sandy substrates, a widespread mixed type of the north German lowlands,
  • Floodplains with gravelly / sandy substrates (e.g. the Rhine from Strasbourg),
  • Coarse material meadows with gravel and coarser substrates (e.g. alpine rivers, Inn).

Loess regions

Loess is a stable fine material that weathers into very fertile soils, which are therefore used intensively. Loess is particularly widespread on the edge of the low mountain range, at the transition to the north German lowlands, in the Börden and on the lower areas of southern Germany, the Gäuen. The waters have short, concave headwaters, where they flow in hollow valleys and merge into wide, fine-material floodplains with elongated, flat longitudinal profiles. They have box-shaped, deep cross-sections, only in the Muldental area less strongly curved courses, otherwise meandering lines. These waters are characterized by poor debris and fine material.

Silt-shaped flowing waters of the marshes

Havel , river type 21

The silt-shaped flowing waters of the marshes are naturally subject to the influence of tides and storm surges. The bottom of the river is shaped by sand, near the bank by silt. In the marshes with little relief, the waters run in spacious meanders that have to absorb the incoming tide into the interior. Due to the cohesive marsh sediments and peat they have stable, steep banks. The water is naturally very rich in nutrients and lime. The waters of the marshes are accompanied by salt and brackish water reeds, softwood alluvial forests and local alder forests. The vegetation depends on the salinity of the water. Since the entire coastline and the marsh islands are diked and the natural regime has been changed by sluices and pumping stations, unchanged marsh waters are rarely found.

Individual evidence

  1. ↑ Schmedtje, U., M.Sommerhäuser, U.Braukmann, E.Briem, P.Haase, D. Hering: Basis for the development of the most important biocenotically relevant river types within the meaning of the Water Framework Directive. 2000.
  2. ↑ A. Otto & U. Braukmann: Water typology in rural areas . In: Series of publications by the Federal Minister for Food, Agriculture and Forests , Series A: Applied Science . Issue 288, 1983.
  3. ↑ T. Pottgiesser & M.Sommerhäuser: Description and assessment of the German river types . Profiles and Appendix. 2008.
  4. ↑ Länderarbeitsgemeinschaft Wasser (Ed.): Working aid for the implementation of the EU Water Framework Directive. unpublished Expert opinion, status: April 30, 2003. PDF
  5. ↑ a b c Umweltbundesamt (Ed.): Profiles of the river types, as of December 2018 PDF
  6. ↑ Illies, J. (ed.): A compilation of all the multicellular animal species that inhabit European inland waters with information on their distribution and ecology . In: Limnofauna Europaea . Fischer, Stuttgart.
  7. ↑ a b c d CASSENS, Maike, Water Landscapes of the Federal Republic of Germany, University of Kiel, 2004

literature

  • E. Briem: Water landscapes of the FRG . German Association for Water Management, Waste e. V. Rheinbach, 2003, ISBN 3-924063-33-8
  • Research group rivers: river typology . 1994, ISBN 3-609-65860-6
  • A. Otto: Fundamentals of water development in Rhineland-Palatinate . Booklet 1 atlas of water types. State Office for Water Management Rhineland-Palatinate, Mainz, 1999, ISBN 3-933123-08-9
  • Patt-Jürging-Kraus: Near-natural hydraulic engineering - development and design of flowing waters . Springer-Verlag, Berlin, 2009, ISBN 978-3-540-76979-8
  • University of Essen, Institute for Ecology-Hydrobiology: Guiding principles for small to medium-sized rivers in North Rhine-Westphalia . Essen, 1999

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