SOME of Scotland's best loved lochs and rivers are being slowly poisoned by agricultural chemicals used by farmers to boost crop growth.
One in 10 freshwater lochs and more than 1,000 miles of rivers and burns are showing signs of damage, according to environmental watchdogs.
The Scottish Environment Protection Agency is now warning that official measures taken since 2000 to stop
the onslaught of fertilisers and pesticides by setting up special anti-pollution zones are failing.
Among the best-known lochs under threat from toxic blooms, caused mainly by agricultural pollution, are Loch Lomond and Loch Leven in Fife. Rivers undergoing the "eutrophication" process - in which excess amounts of fertilisers and pesticides encourage waterway-choking weed and algae growth - include parts of the Clyde, the Don, the Esk, the Almond, the Ythan and the Ayr. In some cases a lack of oxygen is making it difficult for fish to survive.
Sepa is now urging landowners and farmers in vulnerable areas to cut down on the use of agricultural chemicals or face prosecution under new European water-protection laws.
The scale of loch and river pollution is revealed in a report by officials to the main Sepa board last month, reviewing the state of Scotland's environment.
A spokeswoman for Sepa said: "The loch [Lomond] is large and beautiful, but we cannot continue to use it as a sink and expect it to stay that way. The ecosystem is surprisingly fragile and susceptible to nutrient enrichment, which disturbs the balance of wildlife in the water and effects water quality."
The Sepa report says phosphates and nitrates have been pouring into Loch Lomond - from surrounding fields, homes and sewage works - for most of the past half-century as agriculture around the banks intensified.
Nutrient enrichment is also a significant problem at Loch Leven, a large, shallow inland body of water east of Kinross and an officially designated national nature reserve for its bird and aquatic life.
Studies have shown that nutrient enrichment began in the 19th century but accelerated dramatically in the mid-20th century.
Friends of the Earth Scotland's head of research, Stuart Hay, said: "Tackling diffuse pollution is possible, but requires a different approach to normal pollution control.
"It requires behaviour change by agriculture, forestry and industry."
The National Farmers' Union Scotland said there was "a whole host of factors" influencing the quality of Scotland's water and farming activity was just one.
