It's hard to believe but this is the colour of the Waiwhakaiho River as it tumbles down Mt Taranaki.
Regional council officer Bruce Pope says he has never seen anything like it in his life - and he says he has "been in this business a long time".
Many residents would echo his sentiments.
The Daily News was tipped off to this amazing event by Oakura man Ian Scott, who travels throughout Taranaki buying cattle for the meatworks.
Yesterday afternoon he was crossing the bridge in Alfred Rd when he looked down and spotted the orange river.
"I thought what on earth is going on?" He called the regional council and the Daily News.
Mr Scott said he had never seen anything like it.
He put his hand in the water and there was no smell, so Mr Scott thought it might have been red scoria being washed down from Mt Taranaki.
"I can't think of anything else.
"I've seen rivers in flood, but it is nothing like this. It's nature at its best."
The regional council was reassuring people yesterday it was caused by a natural event, not pollution.
Mr Pope believed there was a combination of sediment and oxides from iron ore in the water, which was what made it orange.
"The mountain is full of iron, as is the region.
"We have naturally occurring iron oxide throughout the region."
He said samples were being taken for further testing.
The river is the source of New Plymouth's drinking water, but the district council's water boss, Mark Hall, said we should not worry. Trustpower had isolated the water supply reservoir at Lake Mangamahoe.
There was a tunnel from the river into the lake and Trustpower, which controls the lake, had stopped water flowing into the tunnel.
"We've switched from the water take near the tunnel to our lake intake," Mr Hall said.
The situation would be reviewed when there was more information about what was happening with the river, he said.
"In the meantime we will continue to produce water using the lake source."
However, the orange water should not hurt cows.
As of last night the orange water had not made it as far as Egmont Village. Mr Pope said the discolouration appeared to be dissipating as other rivers entered the Waiwhakaiho and diluted it.
The orange water was coming out of the side of a stream further up Mt Taranaki, just below Boomerang Slip.
A helicopter flew over the area about 4.30pm yesterday and the orange-coloured water was still coming out of the mountain.
"We might send a ground party up there tomorrow. We'll continue to investigate and monitor it," Mr Pope said.
- Taranaki Daily News
What's your expectation of former tropical cyclone Pam?Related story: Cyclone Pam hits New Zealand
Get Taranaki's frequent news and sport updates
Get your mid week news fix
Get your South Taranaki news online