THE RIVER Mersey could almost run dry in just 40 years as hot summers trigger climate change, says a new report.

According to a study by the Environment Agency’s new Water Resource Strategy, river flows in the Mersey are likely to drastically drop by a massive 50 -80 per cent by 2050.

The Mersey was chosen among seven other major rivers in the UK as part of a study on the effects of climate change, due to be published early next year.

Should the predictions be correct, it says, wildlife would be endangered and household water bills would soar.

It had been hoped that as climate change leads to more extreme seasons, summer droughts would be offset by an increase in winter rainfall.

But the researchers say that the wetter winters will not sufficiently compensate for the lack of rain in the longer and drier summers.

Research shows that during late summer and early autumn the river flow could drop by as much as 80 per cent, but will only be offset by rises of up to 15 per cent in the winter months.

This would also mean that discharges that enter the river would not be properly diluted, which would put wildlife at risk from less and poorer water quality.

The Environment Agency will use the new research to look at the extent of the impact of falling river flows on wildlife and water quality while also planning what actions they and others should be taking.

Dr Paul Leinster, chief executive of the Environment Agency, said: ”To be sure we can cope with the kind of changes expected, we must act now.

“The demand for water is also forecast to increase which will only add to the increased pressure on the environment.

“We will publish a new Water Resources Strategy early in 2009 setting out the actions which we and others will need to take to make sure there is enough water for the people and the environment.”

Dr Neil MacDonald, a lecturer in geography at the University of Liverpool, said: “It is important to remember that there is year on year variability within river flows and an 80% reduction by 2050 is the worse case scenario.

“The models that are used to predict future temperature variations are fairly accurate, but the ability to predict water precipitation - for example the amount of rainfall - is poor and it is certainly even more challenging to predict long term regional variations.

“The general rule is that there will be a reduction in river flows throughout the summer months but there is considerable uncertainty as to the actual amount.”

“I certainly wouldn’t be worrying too much that we are going to wake up and find our river gone.”