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4.2 Biological assessment of river quality
Almost all aquatic plant or animal communities, be it micro- or macroscopic, may provide information on the quality of its environment. The community most commonly used in river quality investigations is that of the larger readily visible invertebrate animals colonizing the substrata of all rivers; such animals are collectively referred to as macroinvertebrates of which the main constituents are young aquatic stages of insects. Within this bottom dwelling community the sensitivity and tolerance to pollution of the various constituents vary considerably from species to species. Some species are, for example, very sensitive to reductions in dissolved oxygen and will not be found in areas where oxygen levels are not consistently high. A characteristic feature of polluted environments is a reduction in overall community diversity and an increase in the density of tolerant species. The composition of a macroinvertebrate community at any point in a river therefore reflects the average water quality at that particular point. For this reason macroinvertebrates are widely used in the assessment of river quality.
In the European countries there is a long tradition for assessment of river quality on the basis of macroinvertebrate studies. However, these assessments have primarily been made by local organizations responsible for managing and monitoring specific rivers. In some countries these activities have developed into national surveys of the biological quality of the main rivers (Table 4.2.1). These national surveys are generally based on the results collected by local authorities in accordance with harmonized and standardized procedures (eg. sampling methods, criteria for site selection, classification schemes, etc.). Most of the other countries do not have separate national monitoring programmes for biological assessment of river quality (Table 4.2.1). In some countries macroinvertebrate studies are, included in the general chemical river monitoring programme, macroinvertebrate investigations being, however, restricted to relatively few sampling sites.
Table 4.2.1: Biological assessment of river water quality
No national macroinvertebrate assessment programme (or no information) | Macroinvertebrate assessment based on sampling sites included in the national chemical river monitoring programmes | Special national surveys to assess the biological quality of rivers |
Finland Greece Iceland |
Austria AU-R1 Denmark DK-R1 France FR-R1 Ireland IE-R2 The Netherlands NL-R1 Norway NO-R2 Sweden SE-R2/SE-R3 |
Austria Belgium BE-R2/R8 Germany DE-R2 Luxembourg LU-R2 (Portugal) Spain ES-R2 United Kingdom UK-R3 |
National surveys to assess the biological quality of rivers
The specific biological monitoring surveys are usually made in connection with national classification of river quality. Austria, Germany, Luxembourg, Ireland and the United Kingdom have assessed rivers quality at two to five year intervals since the 1970s, while Belgium and Spain initiated similar activities in the 1980s. In 1992, the Netherlands added a biological subprogramme to their inland water monitoring programme MWTL and since 1989 Denmark has annually been collecting all the biological classification grades from the Danish counties. In Portugal, biological assessment (Saprobic system) is undertaken in a number of separate investigations.
Table 4.2.2: National river monitoring programmes based on assessment of biological river quality.
Code | Name | Variables | Period | Sampling frequency in year of survey | Geographical coverage | Reporting |
AU- | Austria Gewässergüte der Fliessgewässer Österreichs |
Saprobic
system MINVERT |
Since
1968 Every two years |
Nation-wide | Report & maps every 2 year | |
BE- R2 |
Belgium Biological assessment of the quality of rivers in the Flanders region of Belgium |
MINVERT Belgium Biotic Index
|
Since
1989 Not every year |
1/yr | Flanders
part of Belgium 900 sites |
Report
annually |
BE- R8 |
Belgium Biological assessment of the quality of rivers in the Walloon region of Belgium |
MINVERT Belgium Biotic Index, Phytoplankton, Macrophytes |
Since
1980 Every three years |
1/yr | Walloon
region of Belgium 200+150 sites |
Report
& maps every 3 years |
DK - R4 |
Denmark Inventory of biological assessment of river quality |
MINVERT The method and classification schemes used by Danish counties are not fully comparable |
Since
1989 Annual collection of the results of biological classification of rivers |
1-2/yr | No
standard network Totally 10,000 sampling sites per year |
Reports annually |
DE - R2 |
Germany Water quality maps of the quality of flowing waters |
Saprobic
system MINVERT MiFLORA MIFAUNA |
Since
1976 Every 5 years 1976, 1980, 1985 & 1990 |
National all main flowing waters | Maps | |
IE - R2 |
Ireland Biological assessment of river quality |
MINVERT MAPHYT ALGAE siltation |
Since
1971 -1993 : every 4 years 1994- : every 3 years |
1/yr in June-September | National
expanding from 2,000 km in 1971 to 7,000 km in 1981 and 12,700 km in 1990 approx. 3000 sites in 1200 rivers |
Tables maps every 3 years |
LU - R2 |
Luxembourg Biological assessment of river quality |
Belgium
Biotic Index MINVERT and occasionally plankton and macrophytes |
Since
1972 Every 3 to 5 years Heavily polluted rivers are controlled every year |
National Sampling are taken in the main rivers and their principal affluent especially those with fishery interests |
||
ES - R2 |
Spain Biological assessment of river quality |
BMWP Modified biotic index |
Since
1980 Every 3 to 5 years |
4/yr | Nation-wide 847 sampling sites |
Reports and maps |
UK - R3 |
United
Kingdom Biological classification of rivers and canals |
MINVERT | Since
the early 1970s Every 5 years |
Two or three annual samples | England
& Wales 40,000 km of rivers and canals, approx. 7,000 sites Scotland 11,000 km of rivers, 976 sampling sites Northern Ireland 2,500 km of rivers approx. 290 sites |
Reports |
MINVERT: studies of macroinvertebrate community; MiFAUNA: microfauna; MiFLORA: microflora; MAPHYT: macrophyte
The established monitoring networks generally include numerous sampling sites. The UK network and the Irish network, for instance, include around 10,000 and 3,000 sampling sites, respectively. Sites are generally located in all main rivers and reflect the full range of quality conditions of each particular river. The sampling methods used differ and sampling frequency varies among the countries (Table 4.2.2). Additional information on the various methods used for river quality classification can be found in Newman (1988), who made a more comprehensive evaluation of the different classification schemes used in the EU Member States.
In the UK and Germany local authorities, ie. the National River Authority regions and River Purification Boards in the UK, and the Länder in Germany, do the actual sampling and analysis, and special, organised task forces collect the summary results from the local organizations for national evaluation and reporting. In Ireland, by contrast, the biological assessment monitoring programme is carried out by one institution, namely the Environmental Protection Agency. The results are generally published in the form of reports including tables listing the length of rivers assigned to the various grades and river quality maps.
Biological assessment in connection with general national river monitoring programmes
The biological assessment in connection with general river monitoring programmes (eg. AU-R1, DK-R1, FR-R1, and SE-R2/R3) includes one or two annual investigations of macroinvertebrate communities at fixed sampling sites (Table 4.2.3). Additionally, some monitoring programmes include studies of periphyton, macrophytes and fish.
Table 4.2.3: Biological assessment of river quality in connection with general national river monitoring programmes.
Code | Name | Variables | Period of operation and sampling frequency (SF) | Geographical coverage |
AU-R1 | Austria Ordinance on Water Quality Monitoring (rivers) |
Saprobic
index Macroinvertebrates, Phytobenthos, |
Since 1991 | Nation-wide 244 sampling sites |
DK-R1 | Denmark Nation-wide monitoring programme Monitoring of streams |
Macroinvertebrates Phytobenthos |
since
1989 SF: 2/yr |
Nation-wide 261 sampling sites |
FR-R1 | France National basin network |
Invertebrates
Fish |
Since SF: |
Nation-wide 1082 sampling sites |
NL-R1 | The
Netherlands National surface water monitoring programme (MWTL), biological part |
Macroinvertebrates, Fish, Phytoplankton, zooplankton, macrophytes | Since
1992 SF: 1-13/yr, annually or in a four year cycle |
Nation-wide 15 routine sampling sites |
SE- R2 |
Sweden National time series reference streams |
Macroinvertebrates Periphyton |
Since
1993 SF: 1/yr |
35 streams |
SE- R3 | National intensive time series reference streams | Macroinvertebrates Periphyton Fish Macrophytes |
Since
1994 SF: 1/yr except macrophytes every 3 year |
15 streams |
For references, please go to https://www.eea.europa.eu/publications/92-9167-001-4/page021.html or scan the QR code.
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