The Environment Agency has opened a category 1 major pollution incident after a 12-mile stretch of the River Nidd turned chocolate brown.
Experts are still trying to assess the extent of the damage to fish and other river life between Gouthwaite reservoir and Hampsthwaite after huge quantities of silt flowed downstream on Saturday.
Anglers and ecologists are calling for action against whoever is responsible and urging the Environment Agency and Yorkshire Water, which was carrying out safety work at Gouthwaite, to come up with a recovery plan.
An Environment Agency spokesman said today it “continued to investigate” the Yorkshire Water works, which is is thought may have stirred up the silt that flowed downstream on Saturday.
The spokesman added:
“Large quantities of silt in a river can harm fish and smother aquatic plants and invertebrates, starving them of light and oxygen.
“Whilst there is no longer any silt entering the river system, it may still be visible as it moves downstream. The Environment Agency continue to monitor the situation and assess the impacts to determine what further action may be necessary.”
With the water still discoloured, it remains difficult to assess the impact on river life.
Dr. John Shillcock, president of Nidderdale Angling Club and a former ecology officer in the area, said:
“In my past experiences, quantities of sediment of this type block out light and can reduce oxygen levels in the river, harming or even killing river life including invertebrates and other organisms on which fish and other river life depend.
“We are awaiting reliable data on the level of sedimentation before we can assess what damage has been done to an extremely precious river system.
“We would like Yorkshire Water to work closely with the Environment Agency to collect as much data and samples as to work out the best course of action to minimise the immediate danger to river life, and to build a deliverable long-term strategy to enable the river to recover from this avoidable incident as quickly as possible.”
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The affected stretch of the Nidd is known for grayling and trout.
One angler, who asked not to be named, said the amount of silt would harm oxygen levels on which fish depend. He added:
“There should be some sort of action against whoever is responsible for this. It is an environmental disaster.”
‘Heartbreaking to see’
Alastair Ferneley, vicar of Holy Trinity Church, Dacre Banks, said:
“It’s just heartbreaking to see at the moment — it makes me feel sick in the pit of the stomach.
“As I understand it the slit could choke all the bottom dwelling invertebrates and take out the entire food chain — all the things I watch for: dippers, kingfishers, otters, most of the flying insects that spawn in the rivers, the birds and bats that feed on them.
“I’m hoping it won’t be as bad as a I fear it could be. What we need is a good flood to two to clear the silt out and quickly, but not sure that’s very likely.
“It’s a taste of how fragile the environment and everything that depends on it is.”
A Yorkshire Water spokeswoman said it had nothing to add to its statement yesterday, which said it was working with the Environment Agency to investigate what had caused the sediment in the River Nidd to be disturbed. The statement added:
“We’ve temporarily suspended some work our capital partners Mott MacDonald Bentley were doing upstream at Gouthwaite reservoir while we investigate.”