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River Water Quality indicator for sustainable development - 2008 results

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STATISTICAL RELEASE

Ref: 203/09
Date: 8 September 2009

The river water quality indicator is one of the 68 indicators of the Government’s Sustainable Development Strategy. It separately measures biological and chemical river water quality on an annual basis and the indicator for each represents the proportion of river water, in terms of river length, which is considered to be of “good” quality.

Headline results

In England:
  • 72 per cent of river length was of good biological quality in 2008, the same as in 2007 and 2006.
  • 79 per cent of river length was of good chemical quality in 2008, up from 76 per cent in 2007.
In Wales:
  • 88 per cent of river length was of good biological quality in 2008, up from 87 per cent in 2007.
  • 95 per cent of river length was of good chemical quality in 2008, the same as between 2005 and 2007.
UK monitoring networks and quality assessments

For England, Wales and Northern Ireland, results are based on the General Quality Assessment (GQA) classification, providing separate measures for chemical and biological water quality. Chemical water quality is assessed on dissolved oxygen, ammonia, and biochemical oxygen demand (BOD). In England, BOD ceased to be included from 2007, as it is viewed to have little impact on the chemical quality of English rivers. Biological quality is based on numbers of macro-invertebrates.

Results for Scotland are based on results from the Digitised River Network, and give one overall classification, combining chemical, biological, nutrient and aesthetic quality. Results are presented in the biological and chemical water quality sections below, but direct comparisons with the other countries should be treated with caution due to differences in methodology.

For England from 2007, a reduced GQA network was used to focus attention on monitoring for the Water Framework Directive. Results from previous years have been back-calculated but trends are largely unchanged. For Wales, the full GQA network continued to be used.

Following the introduction of the EU’s Water Framework Directive (WFD), Scotland and Northern Ireland have focused their attention on the changes in monitoring networks and reporting required for compliance with this. Therefore the latest data available for the indicator are for 2006, but it is intended to develop new indicators incorporating the new networks for all countries for publication next year. Historical data are presented here for information. Also for this reason, the UK level estimate presented is not produced this year.

Full results

Biological river water quality
In England:
  • 72 per cent of river length was of good biological quality in 2008, the same as in 2007 and 2006; compared to 69 per cent in 2000 and 55 per cent in 1990.
In Wales:
  • 88 per cent of river length was of good biological quality in 2008, up from 87 per cent in 2007, 78 per cent in 2000 and 79 per cent in 1990.
In Northern Ireland:
  • In 2006, 54 per cent of river length monitored was of good biological quality, compared to 56 per cent in 2005 and 62 per cent in 2000.
  • The length of rivers monitored increased greatly between 1995 and 2000, but there was a fall in river length of good quality over this period in those rivers that were monitored in both years.
In Scotland:
  • 88 per cent of monitored river lengths were of good quality in 2006, up slightly from 87 per cent in 2005, which was the same as for 2004 and 2000.
  • Changes in river length allocations and the extent of monitoring between 1990 and 2005 mean that it is difficult to draw conclusions about longer term Scottish trends.

Figure a - Rivers of good biological quality

Table A:  Biological river water quality

Percentage of total river length that is of ‘good’ quality1

Year

England

Wales

N. Ireland2

Scotland3

1990 4

55.4

78.5

76.1

..

1995

66.2

87.0

75.4

..

2000 2

69.0

78.3

66.1

86.7

2000 2

61.5

2001

..

..

49.9

86.9

2002

69.8

78.5

57.3

86.2

2003

70.5

79.3

56.6

87.5

2004

71.0

79.4

51.1

86.8

2005

71.4

80.0

55.7

87.3

2006

72.1

82.0

53.8

87.6

2007 5

72.3

86.9

..

..

2008 5

72.0

88.0

..

..

Source: Environment Agency, SEPA, NIEA

Notes:

  • 1. See Notes to Editors
  • 2. The river length monitored in Northern Ireland more than doubled between 1995 and 2000.  Results for 2000 are shown on both bases for comparison, with the older network first.
  • 3. Data for Scotland are a combined measure of chemical, biological, nutrient and aesthetic quality (see Notes to Editors).
  • 4. 1991 in Northern Ireland
  • 5. Following the introduction of the EU’s Water Framework Directive (WFD), Scotland and Northern Ireland have focused their attention on the changes in monitoring networks and reporting required for compliance with this. Therefore the latest data available for the indicator are for 2006

Chemical river water quality

In England
  • 79 per cent of river length was of good chemical quality in 2008, up from 76 per cent in 2007, 75 per cent in 2002 and 55 per cent in 1990.
In Wales
  • 95 per cent of river length was of good chemical quality in 2008, the same as between 2005 and 2007, and compared to 93 per cent in 2000 and 86 per cent in 1990.
In Northern Ireland
  • 74 per cent of river length was of good chemical quality in 2006, a considerable increase from 63 per cent in 2005, 55 per cent in 2002 and 44 per cent in 1991.
  • The length of rivers monitored increased greatly between 1995 and 2000, but there was a fall in river length of good quality over this period in those rivers that were monitored in both years.
In Scotland
  • 88 per cent of river length was of good quality in 2006, up slightly from 87 per cent in 2005, which was the same figure as in 2004 and 2000.
  • Changes in river length allocations and the extent of monitoring between 1990 and 2005 mean that it is difficult to draw conclusions about longer term Scottish trends.

Figure b - Rivers of good chemical quality

Table B:  Chemical river water quality

Percentage of total river length that is of ‘good’ quality1

Year

England

Wales

N. Ireland2

Scotland3

1990 4

55.2

86.3

44.3

..

1995

70.5

93.2

44.7

..

2000

75.9

93.4

58.8

86.7

2001

76.4

92.5

58.4

86.9

2002 2

75.3

92.2

58.6

86.2

2002 2

55.4

2003

73.1

92.5

57.6

87.5

2004

72.2

94.4

57.9

86.8

2005

73.4

94.7

63.1

87.3

2006

74.4

95.3

74.3

87.6

2007 5

76.2

95.4

..

..

2008 5

78.5

94.8

..

..

Source: Environment Agency, SEPA, NIEA

Notes:

  • 1. See Notes to Editors
  • 2. The length of rivers chemically classified in Northern Ireland increased by about 40 per cent between 1991 and 1994, and by a further 100 per cent (compared with the 1991 network) between 2001 and 2002.  For 2002 figures are shown for both networks, the older network first.
  • 3. Data for Scotland are a combined measure of chemical, biological, nutrient and aesthetic quality (see Notes to Editors).
  • 4. 1991 in Northern Ireland
  • 5. Following the introduction of the EU’s Water Framework Directive (WFD), Scotland and Northern Ireland have focused their attention on the changes in monitoring networks and reporting required for compliance with this. Therefore the latest data available for the indicator are for 2006

About the indicator

The river water quality indicator updated here is one of the UK’s Government’s Sustainable Development Indicators, and supports both the UK Government Strategy Securing the future and the UK Framework for Sustainable Development One future – different paths, which is shared with the devolved administrations in Scotland, Wales and Northern Ireland.

Water quality monitoring is in a transitional phase in the UK, and this will result in a change to the way in which the indicator is presented.  New monitoring schemes are now in place which will enable the UK, through its separate environmental agencies, to monitor and assess river water quality in accordance with the EU’s Water Framework Directive (WFD), which was adopted by all member states in 2000.

Under this Directive, a “river basin” approach has been introduced to monitoring, in place of the previous regional approach, and greater emphasis has been placed on “ecological” objectives. A target has also been set, with all rivers required to be of “good” quality by 2015, although subject to certain exemptions.  Due to the reporting requirements of the WFD, it is not yet possible to produce a stable indicator for UK river water quality, but it is intended that this will be provided next year. 

An accompanying note explains more about these changes.

Notes to editors

1. The river water quality indicator is one of 68 indicators of the UK Government’s Sustainable Development Strategy, published in March 2005. It is also one of 20 indicators outlined in One Future – different paths: The UK’s shared framework for sustainable development, which is shared by the UK government and the devolved administrations of Scotland, Wales and Northern Ireland.

2. All 68 indicators are published in a pocket-sized booklet Sustainable development indicators in your pocket 2009, available free of charge from: Defra Publications, Admail 6000, London, SW1A 2XX Tel: 08459 556000, Fax: 01709 881673 Email: defra@cambertown.com. Quote publication reference PB13265. A large print A4 version is also available, quote PB13265A.

3. More detailed results and descriptions of the current monitoring methods and river networks are available as follows:

4. Chemical data from rolling three-year sampling windows are presented to reduce the bias which might be caused by unusual weather conditions in any one year. In Scotland, from 1996-2006, an overall classification (Digitised River Network) was used combining chemical, biological, nutrient and aesthetic quality. The Scottish classification system and criteria for determining which river lengths should be monitored are different from the other countries. Comparisons between Scotland and other countries should therefore be treated with caution.

5. Historically in England, Wales and Northern Ireland, three measurements were used for chemical quality classification: biochemical oxygen demand, dissolved oxygen and ammonia. However, biochemical oxygen demand ceased to be monitored in England from 2007, therefore the backdated chemical quality data using the smaller 2007 monitoring network does not consider biochemical oxygen demand.

6. Biological testing provides a fuller picture of the health of rivers and canals. Biological grading is based on monitoring tiny animals (i.e. macro-invertebrates) living in or on the river bed. Species groups recorded at a site are compared with those which would be expected to be present in the absence of pollution, allowing for the different environmental characteristics in different parts of the country.

7. In Scotland, iron and pH were also included in chemical monitoring in addition to the other three measurements. Biological (ecological) grading was similar to that used in the other countries. The final allocation of the quality class assigned to a river stretch is based on the lowest class determined from chemical, biological, aesthetic and toxicity assessments available for the associated monitoring point.

8. For this indicator ‘Good’ in England, Wales and Northern Ireland is taken as corresponding to GQA classes A and B. For Scotland, ‘Good’ is taken as corresponding to Scottish Classes A1 and A2 plus unclassified river stretches. Unclassified river stretches are mostly located in rural upland catchments, and have been increasingly brought within the scope of monitoring since 2000.

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Page published: 8 September 2009