Media playback is unsupported on your device Media caption The BBC's Laura Yates says one of the top 10 is London's River Wandle, once classed as a sewer

A list of the 10 most-improved rivers in England and Wales has been released by the Environment Agency (EA).

The list includes the River Wandle in London - which was officially declared a sewer in the 1960s - the River Nar in Norfolk and the River Darent in Kent.

Ian Barker, head of land and water at the agency, said Britain's rivers were "the healthiest for over 20 years".

He said work with farmers, businesses and water companies to reduce pollution and improve water quality had paid off.

River habitats had also benefited from reductions in the volume of water taken by industry and farmers, he said.

'Biologically dead'

Salmon and other wildlife are returning for the first time since the industrial revolution Ian Barker, Head of land and water, Environment Agency

The list also includes the River Thames in London, which was declared "biologically dead" in the 1950s, and the River Taff in south Wales, which the EA says once ran black with coal dust but is now a leading site for fishing competitions.

Others include the River Stour in Worcestershire - previously famed for the rainbow-coloured dyes that flowed into it from carpet manufacturers - and the Mersey Basin, which was once called "an affront to a civilised society" by former government minister Michael Heseltine.

The EA has reviewed thousands of licences which cover the removal of water and is amending those which had resulted in environmental damage.

On the River Darent in Kent, for example, about 35 million fewer litres per day are now being taken than 20 years ago, increasing river flows and helping to support larger populations of wildlife including brown trout and pike, the EA said.

Mr Barker said: "Britain's rivers are the healthiest for over 20 years, and otters, salmon and other wildlife are returning for the first time since the industrial revolution.

'Most-improved' rivers The River Wandle, south-west London

River Thames, London

River Wear, County Durham

River Stour, Worcestershire

The River Darent, Kent

The River Dee, Wales and north-west England

River Nar, Norfolk

River Taff, south Wales

River Stour, Dorset

The Mersey Basin, north-west England Source: Environment Agency

"But there is still more to be done and we have plans to transform a further 9,500 miles of rivers in England and Wales by 2015 - the equivalent of the distance between the UK and Australia."

Geoff Bateman, the EA's head of fisheries and biodiversity, said rivers had benefited naturally from the reduction in heavy industry, but also from a better understanding of how to balance the needs of people with the environment.

"River systems cannot be used for one thing or another, they need to be balanced for multiple uses," he told the BBC.

"We must ensure that now we have improved them - and we still have plenty to do - that we keep them in that state for our children."

The UK must meet tough new European Union (EU) targets on the water quality and ecology of its rivers and lakes by 2015.

The EA - with partners such as Natural England - is targeting £18m of funding from the Department for Environment, Food and Rural Affairs (Defra) to help more rivers meet the new EU targets this year.

Environment Minister Lord Henley said England's rivers were "once home to many iconic species of wildlife".

"With Defra's £110m funding to help clean up England's rivers and the extensive work being done by the Environment Agency, water companies and landowners, we're already seeing fish and mammals, including salmon and otters, thriving once more," he said.