A Christchurch heritage advocate is describing continued vandalism as 'disheartening'.

Otakaro is undergoing maintenance on Victoria Square's Bowker Fountain, after the square re-opened this year following a $7.5 million upgrade.

But Newstalk ZB has been receiving calls from worried residents, seeing skate boarders riding through the empty water fountain.

Christchurch Heritage Trust chair Anna Crighton says it's appalling.

"It might be fun for them, but every time they go into places where they obviously shouldn't be, they're causing damage, and in this case, they'll cause damage to the paintwork and lighting systems."

Crighton says prevention is much easier than remediating any damage skate boarders will be causing.

"They should fence it off if they are going to empty it off, to protect the lips of the fountain and the inner parts. Quite simple."

She says there's always a few spoiling beautiful projects within the city - and it's pointless vandalism.

"They don't care, they don't see the beauty of it or think or anybody else. They just think of themselves and having a good time."

Otakaro says the maintenance is just a regular cleaning, and the fountain bowl should be filled again by early next week.

They are encouraging people to treat the heritage items of Victoria Square - with care, and say they'll consider temporarily limiting access to the fountain if necessary.