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A new review, published a few days ago, of water quality in Scottish rivers and lochs shows 146 rivers and 17 lochs are at risk from pollution. The research, carried out by the Scottish Environment Protection Agency (SEPA), identified waters which show evidence of being damaged by harmful nutrients from sewage effluent, agriculture, forestry, fish farming and urban drainage. SEPA is now responsible for making sure that steps are taken to remove the risks faces by these waters.

Colin Bayes, SEPA's Director for Environmental Protection and Improvement commented: "The "at risk" waters have been grouped and are now designated by SEPA and the Scottish Executive as "sensitive areas". They extend across the country, but are concentrated mostly in urban and agricultural areas in central, southern and eastern Scotland. They include parts of Scotland's best known rivers, such as the Clyde and Tweed and lochs such as Loch Lomond and Loch Leven. In total, eighty-two sensitive areas were identified.

"The designation of sensitive areas means that steps must be taken to reduce the levels of nutrients reaching the waters concerned. It may seem surprising but nutrients pose a major threat to the quality of Scotland's waters. Many Scottish waters are naturally low in nutrients and are therefore particularly sensitive to the effects of enrichment with additional nutrients. These effects are difficult to reverse, so it's important to take action early to limit the damage.

"Where waste water treatment works discharge to these areas, Scottish Water is charged with providing additional treatment to reduce the level of nutrients in the effluent before it is discharged. Where nutrients are not discharged from a pipe, as in the case of drainage from agricultural land, nutrient levels are more difficult to control. We will need to work with the agricultural industry in tackling the problem and hope to do so co-operatively rather than rely on the new powers granted to SEPA under European legislation.

"We will also be working with the Scottish Executive, Scottish Natural Heritage and other partner organisations to ensure that water quality targets are met."

Nutrients such as phosphates and nitrates are essential to sustain plant and animal life, but when present in high concentrations they can cause excessive growth of certain plants. These dense growths can choke rivers, blanket coastal mudflats and form unsightly scums on lochs. In severe cases, oxygen in the water is reduced, causing the death of fish and other aquatic life. The water may become unsuitable for drinking, industrial use or recreational purposes.

The only estuary or coastal water which showed evidence of damage was the Ythan estuary in north-east Scotland. The Ythan was designated as a sensitive area following a previous review in 2001.

The full report can be found on the SEPA website: http://www.sepa.org.uk/publications/index.htm#technical

Reviews of the quality of Scottish waters in relation to the effects of nutrient enrichment ("eutrophication") are required at least every four years under European legislation (the Urban Waste Water Treatment Directive and the Nitrates Directive).

The main sources of nutrients in Scottish waters are sewage effluent and drainage from agricultural land.

Coastal Waters
None of the coastal areas surveyed showed signs of eutrophication. Nutrient concentrations in the Firths of Forth and Clyde were enhanced relative to background concentrations, but this was not observed to result in excessive algal growth. A review of the current OSPAR RID programme in Scotland is required to ensure that relevant discharges are being monitored. Data was not available for a number of the smaller qualifying discharges (e.g. Lerwick, North Berwick) and some larger industrial discharges (e.g. DEFCO and Dounreay).
The report does not make mention of the reason why data is not available from DEFCO Dounreay.