The need to ramp up Adelaide’s desalination plant or enforce water restrictions in the looming dry, hot summer has been “ruled out” by surprising rainfalls that have South Australia’s reservoirs at their highest winter level in 20 years.

The state’s biggest reservoir, Mount Bold near Kangarilla in the Adelaide Hills, is at 95 per cent capacity – up from 55 per cent at the same time last year.

South Para reservoir, near Williamstown north-east of Adelaide, is at 76 per cent this week compared to 45 per cent last year.

And Myponga on the Fleurieu Peninsula is at 87 per cent – a huge jump from last year’s 59 per cent. In just 24 hours to 8am on Tuesday, Myponga captured a whopping 2.3 billion litres.

Overall, the combined total for the state’s reservoirs is 85 per cent, up from 55 per cent at the same time last year. The last time it was at 85 per cent was in the spring of 2023. It has been 20 years since winter levels reached that peak.

The figures are a “very good surprise”, according to SA Water’s senior manager of water futures and security Ashley Kingsborough.

“We’d been anticipating a dry end to winter flowing through into a dry spring period. It rules out any potential need for water restrictions or to even contemplate restrictions for the summer ahead,” Dr Kingsborough said.

“We’re very pleasantly surprised by the additional water coming into the reservoirs … it’s good news.

“We’ve obviously been quite concerned with the forecasts of El Niño coming, and we still anticipate higher levels of water demand in the summer ahead when it does turn. But with this much water in storage … there’s absolutely no need for water restrictions in Adelaide in the summer ahead, we’ve got multiple years of resilience built in before we need to contemplate anything like that.”

Adelaide’s 10 reservoirs, spread across the Western Mount Lofty Ranges, have collected 100 billion litres of water this winter – the biggest volume in the past 20 years. In just 24 hours to 8am on Wednesday, more than 7.5 billion litres had gushed into the reservoirs.

Dr Kingsborough said the levels would continue to “edge upwards” over the next few days as water flowed into reservoirs.

He said the desal plant would be run in maintenance mode over summer, producing about 5.3 billion litres in the 2026/27 season – about five per cent of total water demand.

“If something really does go wrong, we can turn it up,” he said.

“We are always wanting to encourage customers to be as efficient with their water use as possible because it is a finite resource and it’s not something that we want people to be just frivolous with. But we’re feeling very, very comfortable for the summer ahead.”