The first water order from Victoria's controversial Wonthaggi desalination plant has been placed by the Andrews government in a bid to combat declining water storages across the state.

Premier Daniel Andrews and Water Minister Lisa Neville made the announcement at Cardinia reservoir on Sunday morning for 50 billion litres (50 gigalitres) – the Target 155 water saving campaign will also be reactivated.

As first reported by The Age last week, an order for water had been imminent with a deadline for an order on April 1.

The order will push up water bills by $12 a year for households. Even with no order placed, Victorians pay $1.8 million every day to keep the desal plant open and ready for an order.