River turns ‘bright orange’ in New Zealand. ‘Worst case scenario’ is likely source
The water in a river of New Zealand turned “bright orange,” prompting warnings from officials and an investigation. Photos show the atypical coloring and its source.
The Waikato Regional Council received reports that the Ohinemuri River had turned “bright orange” on the afternoon of Aug. 23, officials said in a Facebook post. A photo shows the pumpkin-colored water.
Officials suspected the discoloration could have been caused by a dam collapse or erosion, but the “worst case scenario is the discoloured water is due to a mine shaft collapse,” Robert Isaac, an officer responding to the incident, said.
Other photos show the edges of the orange coloring. Nearby, the normal-colored water appears dark blue-green.
Following the discoloration, officials located the source: an “old mining asset” with a trail of orange sediment leading to the river, the council said in an Aug. 24 news release. A photo shows this tunnel-like structure.
Officials took samples of the orange water at various points in the river and at the old mine entrance.
“Getting results from our sampling takes time, and it will be days before we know,” Patrick Lynch, a manager with the council, said in the release. “We only know what might be in sediment in an old mine shaft.”
Sediment from mines can include “residual arsenic and heavy metals such as cadmium, chromium and antimony,” the council said. Heavy metals like these are considered toxic, so officials urged the public to remain cautious around the river.
“The colour indicates it will be iron-related, but it is likely to be highly acidic so again we advise people to treat it as contaminated and not touch it,” Lynch said. “We are testing for these heavy metals, and also mercury.”
The council expects to have preliminary sample results by Aug. 27, officials said in a release.
“There is still sediment that has settled in the river in quiet locations or around rocks, but most of it has been flushed through the system,” Lynch said. “The settled sediment may be present and visible for some time, and we still advise caution as we do not know yet what it contains.”
Questions also remain over what caused the sediment to come out of the mine.
“We really want to understand how this event happened and that investigation will take time,” Lynch said. “It’s also one of those situations where we are relying on mother nature — a rain event — to wash the contaminant away. The more water it’s exposed to, the more diluted it will get.”
Ohinemuri River is on New Zealand’s North Island and a roughly 80-mile drive southeast of Auckland.
