Ms Jeffrey is a National Capital Authority project officer who looks after the water-quality testing in Lake Burley Griffin, which will resume next week for the summer months.

She says Canberrans need to keep an eye on what goes down the capital's drains, lest they pump excess nutrients into the lakes.

''It should be a year-round thing, it should become a habit for you, just to know that whatever goes down the drains can end up in our waterways and it's not good for our waterways,'' she said.

''So just simple things like that - stopping the leaf litter or the lawn clippings going down the drain or things like washing your cars on the lawn so the phosphates of the soaps don't go down the drain, walking your dog, collect your dog faeces.''

On Sunday, Ms Jeffrey, along with a number of volunteers and Greening Australia members, were planting aquatic macrophytes - water plants, reeds, rushes, sedges - along Yarralumla Beach as part of a continuing program aimed at improving the lake's water quality.

The plants act as filters for sediment and draw excess nutrients out of the water, reducing the risk of major algal blooms, which occasionally close parts of the lake in summer.

There are two more community planting days on the next two Sundays, and Greening Australia's Haydn Burgess said more than 40 people had already registered for next Sunday's event at Lotus Bay. He said it was a chance for ordinary Canberrans to look after one of the city's main assets. No experience is necessary and a barbecue lunch will be provided.

French students Cecile Brun and Camille Brillion, both 21, are doing an internship with Greening Australia.

They said the beautiful location and excellent weather made for a great morning.

Ms Brillion said the 500 plants put in on Sunday was a ''good start'' for helping the water quality.

''If it can make people conscious of what there is to do to improve the quality of the lake, then it's a good thing to do,'' she said.

To find out more or to register for a planting day, head to the National Capital Authority website nationalcapital.gov.au.