But all is not as it looks. A new official survey, the most complete ever of Britain's lochs and lakes, shows that pollution in Loch Lomond is rising astonishingly fast. It suggests that the loch is now nearly 10 times dirtier than it was when the retired couples on the boat were young - and that the contamination of its water has increased much faster than in any of the other natural lakes it surveyed in the British Isles.
The survey, carried out for the National Rivers Authority (NRA), now part of the Environment Agency, is a huge embarrassment for ministers who have denied for years that pollution is widespread in Britain's lakes. As reported in last week's Independent on Sunday, it shows that more than 95 per cent of them have been significantly polluted over the past 60 years. More than half of them are twice as dirty as they were in the 1930s, and nearly a third are more than three times so.
The survey shows just how serious the pollution problem has become, despite claims by ministers that they have taken action to clean up Britain's sewage works under a new European directive. It is also likely to lead to further demands for the beleaguered privatised water companies to spend more on implementing the directive properly.
All last week the Environment Agency was seeking to downplay the impact of the survey, originally carried out to find a new way of measuring lake pollution, raising concern among environmentalists that it was proving more susceptible to ministerial pressure than the robust NRA that preceded it. But it confirmed the accuracy of the report's conclusions and acknowledged that it is the most comprehensive survey of its kind ever carried out in Britain.
The fine detail reveals even more embarrassing data. Loch Lomond, it suggests, is 865 per cent more polluted by phosphates and other nutrients than 65 years ago. In Norfolk, Rockland Broad is 761 per cent more polluted, and other lakes ranged from 330 to 550 per cent.
The survey measures the rate at which pollution is increasing, rather than the actual amount of the contamination. Thus Loch Lomond, which until recently was relatively pristine, far out-paces Lake Windermere, which is much dirtier but has been polluted since Victorian times.
"To the casual observer, Loch Lomond looks nice and clean," says Doctor Penny Johnes, one of the authors of the survey and a lecturer at Reading University's new Aquatic Environment Research Centre. "But we don't understand what the pollution is doing to its species. It is rather like cutting down the rainforests and then finding it would have been a good idea to keep them."
Women in the Highland Arts Centre at the loch were worrying last week about children swimming in its waters, because of sewage from the growing navy of pleasure boats. But Doctor Johnes says that these do not pose the main problem. The pollution, she says, mainly comes from agriculture and waste from a local hospital.
The Environment Agency is commissioning the same team to do a study to work out a monitoring system it can use to keep a constant check on pollution in all lakes in England and Wales.Reuse content