Britain's rivers could run dry

Flows in Severn and Mersey might drop by up to 80 per cent by 2050, experts warn
David Smith
The Observer,
Sunday October 5 2008

Britain's rivers could nearly run dry because long hot summers caused by climate change will not be sufficiently compensated by wetter winters, researchers predict. It is a scenario that would endanger wildlife and send household water bills soaring.
Flows in the Mersey and Severn are likely to be reduced in summer by up to 80 per cent by 2050, according to a study by the Environment Agency. The Thames's flow is likely to decline by up to 50 per cent during the same period.
It had been hoped that, as global warming leads to more extreme seasons, summer droughts would be offset by an increase in winter rainfall. However, while wetter winters are expected, they will not be damp enough to make up for the lack of rain during the hotter summers.
The news might come as a surprise to people in towns such as Tewkesbury in Gloucestershire, who have suffered flooding due to extraordinary downpours during the past two summers. But the agency claims that, while such extremes are a hallmark of climate change and wet summers will still occur, the overall average trend is towards drastically reduced river flows across the country.
Ian Barker, head of water resources at the Environment Agency, said yesterday: 'For a long time, we've known climate change would result in wetter winters, which would increase winter flows in rivers, and that it would also result in drier summers.
'The received wisdom was that the two would balance each other out and overall we'd end up with the same amount of water, just distributed differently throughout the year.
'But we wanted to understand how much extra rainfall we might get in winter, and how much less rainfall we might get in summer. The net effect is that overall, although winter rainfall might increase by 10 per cent, the period of higher river flows is reduced, so it's perhaps only December, January, February, maybe into March. The period when you'd see lower river flows because the rainfall is significantly less would extend from April right through to November in some parts of the country.' Barker warned: 'Overall, it means that, by the 2050s, there's a net reduction in the amount of water resources available for water companies to pump out of rivers, farmers to use for irrigation and also to support wildlife in rivers.
'If you get reduced flows, in summer the temperature of the water will increase, there's less water to dilute pollution, and that will also affect what is in our rivers.'
The research used climate projections from the UK Climate Impacts Programme and shows that by 2050 river flows in winter may rise by 10 to 15 per cent in England and Wales. But river flows in late summer and early autumn could fall by as much as 80 per cent in some places. These patterns would result in a drop in total annual river flow of up to 15 per cent.
But Professor Stuart Lane, executive director of the Institute of Hazard and Risk Research at Durham University, issued two caveats. 'First, something that's quite clear in the IPCC [Intergovernmental Panel on Climate Change] report issued last year is that our ability to forecast rainfall precipitation is particularly poor when compared with our ability to predict temperature,' he said.
'Second, these kind of average figures often overlook what most people will experience - indeed, a lot of people find it very difficult to relate to predictions like these because we will always have both wet summers and dry summers, and wet summers are actually quite normal.
'What that means is these are average changes and it's quite possible that the kind of drought scenarios that are being talked about here could be much worse or not as bad on a year-to-year basis.'