Freak storms on May 10 caused large banks of silt from Logan Reservoir to run down a pipe and into the river.

This left a stinking cocktail of sludge and dead brown trout, minnows and beardies — covering 1.5km of water.

The pollution has completely devastated local fishermen like Nethan Valley Angling Club chairman Kemp Meikle.

"This is a disaster on a large scale," Kemp (62) said."I've been a fisherman for 57 years and this is the worst crisis I've ever seen.

"From the Logan Reservoir downstream to Craighead in Lesmahagow, there is evidence of silt in every pool in the water.

"Our remit is to look after the river but seven years of hard work by our volunteers has been ruined.

"We have put 10,000 young fish into the river this year and most of them have been wiped out."

Kemp has blamed the pollution on land owners Scottish Water. He branded the firm as ''amateur'' for recent reservoir repair works.

He added: "Scottish Water had a major problem trying to repair Logan Reservoir, an old reservoir which is no longer in service.

"Common sense simply went out the window.

"When you are draining down a reservoir that has never been drained down before, you should be monitoring it daily.

"That clearly wasn't happening, which beggars belief.

"Scottish Water didn't even tell us that it had started the work. It should have contacted us with a method statement."

Kemp also revealed that Nethan Valley Angling Association member Jim Delaney had suffered vomiting, diarrhoea, itching and burning sensations since touching the silt with his bare hands during a visit last week.

He is worried that the sludge could even contain radioactive
particles; fallout from the Chernobyl Nuclear Power Plant disaster of 1986.

Helen Lennox, head of corporate affairs at Scottish Water, said: "The draining of the reservoir was important maintenance work. We have a legal obligation to keep reservoirs in good working order.

"Scottish Water takes its environmental obligations seriously and we apologise to the community for the effects of this work. We will work to mitigate the impact of the silt in the water."

And a spokesman told the Gazette: "On Thursday, May 8, Scottish Water drained the Logan Reservoir as part of necessary remedial works. As this facility had not been drained before, there was no knowledge of the volume of silt in the water.

"Scottish Water, in direct consultation with SEPA, took action to control this spill. Three straw dams were erected in the watercourse with a further dam placed to capture smaller particles.

"No further silt should enter the water. An ecologist report has been commissioned by Scottish Water to do a habitats survey of the 2km of the Logan Water downstream.

"Scottish Water has also engaged its environmental team to work on this issue, and a clean up operation will be undertaken by Scottish Water in conjunction with SEPA.

"At every stage the local Angling Club has been consulted and
compensation has been discussed with regards to its stock.

"Apart from some fish in the reservoir, no wildlife appears to have suffered. Scottish Water expects more details following the ecologist survey."

The spokesman added that no traces of radiation had ever been found at Logan Reservoir.

But Jimmy remains worried. He said: "Mammals will be forced to move or starve to death.

"And what about all the bird life that feed their young on insects?

"Many carcasses have been scavenged, so are the scavengers at risk of being poisoned?

"The whole river eco-system has been wrecked and will suffer for a long time to come."