In 2006, almost all of the region's rivers were of good or fair quality - 97.14% being of good or fair chemical quality and 98.91% being of good or fair biological quality. This was higher than the national average (just under 92% for chemical quality and 94.45% for biological quality).

What is river water quality?

The Environment Agency assess river quality annually using a survey called the General Quality Assessment (GQA) scheme. This measures four aspects of river quality – biology, chemistry, nutrients and aesthetic quality.

Around 7,000 sites representing about 40,000km of rivers and canals in England and Wales are monitored by the Environment Agency.

Click here for more information on how river water quality is measured or find out what influences river water quality.

Click here for more information on the Water Framework Directive and an example of the River Tamar (Cornwall)

Rivers in the South West

There are around 6060 km of monitored rivers within the Environment Agency South West (6490km in the Government Office regional boundary). These rivers are well distributed throughout the region, although just over one-third can be found in Devon.

River length in South West counties monitored by the environment agency

County	Length of river monitored for chemical quality (km)	Length of river monitored for biological quality (km)	% of regional total
Cornwall and Isles of Scilly	947.12	942.41	16%
Devon	2,131	2,041.80	35%
Dorset	551.99	540.70	9%
Gloucestershire	675.56	667.97	11%
Somerset	1,038.99	996.44	17%
Wiltshire	723.61	665.96	12%
Total	6,068.27	5,855.28	100%

Distribution of rivers and floodplains in the South West

Source: Environment Agency (2004)

River water quality in 2006

An assessment of river water quality in England and Wales in 2006 was published in August 2007 by the Environment Agency.

River water quality in the South West 2006

In 2006, almost all of the Region's rivers were of good or fair quality - 97.14% in terms of chemical water quality and 98.91% in terms of biological quality. In addition, 21.8% of monitored rivers in the region had high or very high nitrate levels and 42.8% had high or very high phosphate levels.

The following section provides a summary of both regional and county level data for both chemical and biological water quality.

Chemical river water quality 1990 - 2006

In 2006, 97.14% of all monitored rivers in the South West had good or fair water quality, this was considerably higher than the mean of 91.96% for England and Wales.

The proportion of rivers with good or fair chemical water quality in 2006 was highest in Wales (98.8%), followed by the North East (97.86%) and then the South West. Overall, 44% of rivers improved (net) between 1990 and 2006. After a few years of slight decline, quality is now close to the best ever standards of 2001.

With 81.04%, the vast majority of the region's river water was classified as being of good chemical quality in 2006, whilst 16.10% was of fair quality. A very small proportion did not meet these standards, with just 2.81% deemed as being poor quality and 0.04% bad quality.

There has been a significant improvement in chemical water quality in the region since 1990, when 93.11% were of good or fair quality. There was also a small improvement of 0.05 percentage points on 2005.

South West rivers: chemical water quality 1990 - 2006

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Source: Environment Agency (2007)

Regional Chemical water quality in 2006

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Source: Environment Agency (2007)

Biological river quality 1990 - 2006

In 2006, 98.91% of all monitored rivers in the South West has good or fair water quality, this was considerably higher than the mean of 94.45% for England and Wales.

The South West had the highest proportion of rivers with good or fair biological water quality in England during 2006, behind only Wales (99.22%). Between 1990 and 2006, 28% of rivers (net1 improved in biological quality. Most of this improvement occurred in the first five years and the improvement since then has now levelled off. In some places, for example in Wales, biological quality has deteriorated since 1995.

With 88.77%, the vast majority of the region's river water was classified as being of good biological quality in 2006, whilst 10.14% was of fair quality. A very small proportion did not meet these standards, with 0.68% deemed as being poor quality and 0.41% bad quality.

There has been a significant improvement on biological water quality in the region since 1990, when 96.88% were of good or fair quality. There was also a small improvement of 0.05 percentage points on 2005.

South West rivers: biological water quality 1990 - 2006

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Source: Environment Agency (2007)

Regional river water quality 2006

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Source: Environment Agency (2007)

River water quality in the South West counties 2006

The following section provides a summary of county level data for both chemical and biological water quality.

Chemical river water quality

In 2006, river water of good or fair quality were above the average for England and Wales of 91.96% and the English average of 93.3%.

Cornwall and Dorset had the highest proportion of rivers with good or fair quality (100%), whilst Cornwall had the highest proportion of good quality water (94.8%). Only Somerset recorded water of bad chemical quality water, although this was an extremely small proportion of those rivers monitored in the county (0.3%).

Chemical river water quality in South West counties 2006

	Good %	Fair %	Good & fair %	Poor %	Bad %
Cornwall	94.8	5.2	100	0.0	0.0
Devon	90.1	8.3	98.4	1.6	0.0
Somerset	63.1	30.0	93.1	6.6	0.3
Dorset	81.8	18.2	100	0.0	0.0
Wiltshire	75.1	19.1	94.2	5.8	0.0
Gloucestershire	74.7	23.3	98	2.0	0.0

Environment Agency (2007)

Cornwall & the Isle of Scilly

Chemical river water quality is consistently excellent in Cornwall and the Isles of Scilly, with 100% of rivers falling under the good or fair category in 2006. This reveals an increase of just over 1% on 1990.

94.78% of all rivers monitored in the county had good chemical quality in 2006, the highest proportion yet recorded.

Chemical river water quality in Cornwall & the Isles of Scilly: 1990 - 2006

Source: Environment Agency (2007)

Devon

Chemical river water quality is consistently excellent in Devon, with almost 98.4% of rivers falling in the good or fair category in 2006, an increase of almost 3% on 1990.

90.07% of all rivers monitored in the county had good chemical quality in 2006, a very slight decline on 2005 (91.57%) but still higher than previous years.

No rivers recorded bad chemical water quality, whilst just 1.6% were of poor quality. This reveals an improvement of 2.68 percentage points on 1990 when 4.28% of rivers were of poor or bad quality.

Chemical river water quality in Devon: 1990 - 2006

Source: Environment Agency (2007)

Somerset

Chemical river water quality is consistently excellent in Somerset, with over 93.09% of rivers recording good or fair water quality in 2006, an increase of over 3% on 1990.

63.09% of all rivers monitored within the county in 2006 were of good water quality. This proportion has declined since it's peak at 69.7% in 2000, however, it marks an improvement of 6% on 2005.

6.91% of all rivers monitored had poor or bad chemical water quality in 2006, 6.64% of which were poor quality and just 0.27% were of bad quality. This marks an improvement of 3 percentage points on 1990.

Chemical river water quality in Somerset: 1990 - 2006

Source: Environment Agency (2007)

Dorset

Chemical river water quality is consistently excellent in Dorset, with 100% of rivers falling in the good or fair category in 2006, a general increase of almost 3% on 1990 and just under 1% on 2005.

81.85% of all rivers monitored within the county in 2006 were of good water quality, the highest proportion yet recorded.

Dorset has recorded no rivers falling into the bad category since 1990, whilst the percentage of poor quality rivers has varied (averaging around 1.8% between 1990 and 2005). No rivers had poor water quality in 2006, an improvement on 0.91% in 2005.

Chemical river water quality in Dorset: 1990 - 2006

Source: Environment Agency (2007)

Gloucestershire

Chemical river water quality is consistently excellent in Gloucestershire, with 97.98% of rivers falling in the good or fair category in 2006, a increase of over 9 percentage points on 1990 and 0.8 percentage points on 2005.

74.72% of all rivers monitored within the county in 2006 were of good water quality in 2006. Although this was 15.7 percentage points lower than the peak of between 2001 and 2004, it was 5 percentage points higher than in 2005.

There have been no incidences of bad water quality in the county since 2003. Just 2.02% of all rivers in 2006 were of poor quality, an improvement of 7.7 percentage points on 1990 and 4.28 percentage points on 2005.

Chemical river water quality in Gloucestershire: 1990 - 2006

Source: Environment Agency (2007)

Wiltshire

Chemical river water quality is consistently excellent in Wiltshire, with 94.18% of rivers falling in the good or fair category in 2006. Although this was an increase of 6.7 percentage points on 1990, there has been a decline of 1.49 percentage points on 2005.

75.12% of all rivers monitored in the county were of good water quality in 2006. This was on a par with the peak in 2000 to 2002 and a 4.67 percentage points higher than in 2005.

There has been no incidence of bad water quality in Wiltshire since 2003. However, there was a slight increase of 1.49 percentage points in those rivers with poor water quality, from 4.33% in 2005 to 5.82% in 2006.

Chemical river water quality in Wiltshire: 1990 - 2006

Source: Environment Agency (2007)

Biological river water quality in South West counties 2006

In 2006, all of the South West's counties recorded river water of good or fair biological quality higher than the average for England and Wales of 94.45% and the English average of 95%.

Somerset, Dorset and Wiltshire had the highest proportion of rivers with good biological quality in the region (100%), whilst Dorset had the highest proportion with good quality (97.23%). Only Cornwall recorded water of bad biological quality, although this was an extremely small proportion of those rivers monitored in the county (2.71%).

Biological river quality in South West counties 2006

	Good %	Fair %	Good & fair %	Poor %	Bad %
Cornwall	75.54	19.16	94.7	2.59	2.71
Devon	95.38	4.38	99.76	0.24	0.00
Somerset	93.96	6.04	100	0.00	0.00
Dorset	97.23	2.77	100	0.00	0.00
Wiltshire	89.86	10.14	100	0.00	0.00
Gloucestershire	73.89	24.56	98.45	1.54	0.00

Source: Environment Agency (2007)

Cornwall & Isles of Scilly

Biological river water quality is consistently excellent in Cornwall & the Isles of Scilly, with 94.7% of rivers falling in the good or fair category in 2006. However, this was 0.5 percentage points lower than in 2005 and 0.32 percentage points lower than in 1990.

75.54% of all rivers monitored in the county were of good water quality in 2006. Although still high, this was the lowest percentage yet recorded and marks a continued small decline since 2002 when 80.42% or waters were of good quality.

The percentage of rivers with poor or bad water quality have declined from 7.97% in 1990 to 5.3% in 2006. However, there was a slight increase of 0.5 percentage points between 2005 and 2006.

Biological river water quality in Cornwall & Isles of Scilly 1990 - 2006

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Source: Environment Agency (2007)