|The organisation says plans are in place to cope with the strike|
Several hundred workers with Scottish Water are taking part in a 24-hour walk-out in a dispute over pay.
Union leaders say the industrial action, which started at noon on Thursday, will affect Scottish Water operations across the country.
Employees are protesting a pay increase which they claim is unfair.
Dougie Black, a negotiator with Unison, said: "Clearly it is an issue which our members feel very strongly about.
"I would invite Scottish Water and the Scottish Government, even at this late stage, to come back to the negotiating table.
"We are always ready to talk about a way to settle this dispute."