Urgent measures are needed to protect lakes in England and Wales from pollution and climate change, according to the Environment Agency.
The call for action comes as experts gather at Windermere in Cumbria to discuss ways to safeguard England's largest lake.
Windermere faces threats including invasive species and farming pollution.
The Agency said it planned to assess about 730 lakes to ensure they meet new European water standards.
The EU's Water Framework Directive will impose exacting requirements on lakes and rivers, to be met, in some cases, by 2015.
At Tuesday's meeting, Environment Agency chairman Lord Chris Smith will stress the important role lakes play in the natural environment and the difficulties they face.
These include global warming, which is expected to cause more flooding and wash pollution into lakes.
At Windermere, pesticides and fertilisers from farming are contributing to regular blue-green algal blooms which prevent people from going into the water.
The lake is also threatened by invasive New Zealand Pigmyweed, which is smothering other plants.
The Agency's director of environment and business, Tricia Henton, said: "While water quality in our rivers has improved dramatically over the past 20 years, lakes have faced different, more complex environmental challenges.
"They are an important part of our environment and every bit as important as our rivers. They are invaluable to tourism.
"That's why the Environment Agency and its partners are setting out a blueprint to bring life back to our lakes, creating a better environment for people and wildlife."
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