The UK government's Environment Agency has won the International Theiss River Prize - which marks outstanding achievement in river management and restoration - for its work on the River Thames.

The river took the award - presented at the International Riversymposium in Perth, Australia - thanks to its recovery from a biologically dead river in the 1950's to a waterway which is today teeming with fish, and with returning salmon, otter and sea trout populations. The chemical quality of the rivers within the Thames catchment classed as 'Very Good' or 'Good' has improved from 53 per cent in 1990 to 80 per cent in 2008, while the estuary supports viable shellfisheries and is a nursery ground for commercial sole and bass stocks.

Since April 2005, 393 habitat enhancement projects have been completed and nearly 43.5 miles (70km) of river has been restored or improved. Alastair Driver, national conservation manager at the Environment Agency, said: "In the last 150 years the Thames has been to hell and back, and it has taken thousands of people many decades to restore it to this point.

"Tighter regulation of polluting industries and our work with farmers, businesses and water companies to reduce pollution and improve water quality, have all helped to make the Thames a living river once again." Boris Johnson, mayor of London, said: "The Thames is one of our most precious assets, so I am thrilled to see that efforts to improve and preserve its good health are being lauded on the world stage."

The Agency has pledged that the AU$350,000 (£217,400) prize money will go to the Thames River Restoration Trust, with part of it being used to establish a twinning project to help restore a river in the developing world. Finalists in the award - in addition to the River Thames - were Hattah Lakes, Victoria, Australia; the Yellow River, China; and the Smirnykh Rivers Partnership in Sakhalin, Russia.