For months, ITV News has been investigating the problem of river pollution - and the Wye, which runs from its source in mid-Wales through Herefordshire and Gloucestershire, is among the worst.
A special investigation from ITV News journalists in the Central, Wales and West Country regions examines what is going wrong - and what needs to be done.
In the first part of our series, ITV Central Environment Correspondent Charlotte Cross reveals the scale of the crisis affecting the River Wye.
A stream of filth floats along the top of the water, while beneath the surface, plant and fish life is dying off - both clear signs that something is terribly wrong on the River Wye.
Anglers in Ross operate a five-mile stretch of the waterway near the Wales-England border, and have been monitoring levels of damaging phosphates for the last 15 months.
Of 86 readings, only eight have come in under the safe limit of 0.05 parts per million.
"It makes me want to cry, frankly," said Trevor Hyde, who has taken on the unhappy task of carrying out the weekly phosphate tests.
"It makes you angry to come down here and find that every week, with few exceptions, that you're going to find a reading from the river that's going to be two, three, four, five times what it should be."
Mr Hyde said: "When I started, I had no idea what I was getting myself into. I can’t believe it’s been allowed to get to this point."
There are a number of possible causes - but two which stand out.
One of them is farming - specifically, the number of poultry farms which have sprung up in the Wye catchment area.
Chicken faeces are notorious for being high in phosphates, and in some cases is actually used as fertiliser as the chemical aids plant growth.
But while that may be of benefit on land, if it washes into the rivers it becomes a nutrient source for algae, and large algal blooms - such as those seen along the Wye in recent years - choke off other plant life, robbing fish of both food and places to lay eggs.
The knock-on effect goes right up the food chain.
“It has a devastating effect,” says Stuart Smith from the Wye Salmon Association.
It was this group which first asked the anglers in Ross to start measuring phosphate levels, after noticing significant drops in salmon populations all along the river.
"There are lower fish stocks due to lower foods being provided for young fish to feed and grow and migrate and come back to populate the river," he said.
"Bird species are either dying or not laying their eggs because there’s insufficient food for them."
"So that whole ecological food chain is simply dying and falling away."
On Wednesday, ITV Wales’ Rural Affairs Correspondent Hannah Thomas looks at the issues surrounding poultry farming in more detail.
The second culprit is the amount of raw sewage being dumped in the country’s waterways.
Water firms are, by law, allowed to open the gates to allow untreated human and industrial waste, and anything else in the sewers, to gush into the nearest waterway.
The system was designed to only be used in emergencies, for instance when heavy rainfall means the system is too full and risks flooding.
But a growing population combined with an increasing number of extreme weather events has meant this ‘emergency’ measure is being used more and more.
An ITV News analysis of data from Dŵr Cymru Welsh Water, the water company responsible for the areas through which the Wye flows, reveals in 2020 alone, the Combined Storm Overflows in areas linked to the Wye were open for more than 17.4 million minutes - that amounts to 33 years’ worth of sewage entering brooks, streams and rivers in just 12 months.
"You see sanitary towels, toilet paper, human waste and often this white grey cloud of water with all the associated foam just sort of streaming down the river," said Rob Leather, the chairman of the Ross Angling Club.
He no longer takes his children swimming in the Wye because of what he has seen coming out of the overflows.
On Thursday, ITV West Country Presenter Jonty Messer looks at the problems of sewage outflows in more detail.
A ‘nutrient management board’ made up of Natural England, Natural Resources Wales and the Environment Agency has long been in place to try to work out a plan.
And at the start of the year, the Environment Agency in England told us it was working with Cardiff University to recruit ‘Citizen Scientists’ to help monitor pollution in the Wye.
Jenny Hewitt, from campaign group 3 Wyes Women, said some of her own phosphate measurements along one of the Wye’s tributaries had been 28 times what they ought to be.
She said it has been tough to get anyone to take responsibility for what’s ending up in the water.
"My background is a primary school teacher, and you have to deal all the time with behavioural gambits from children pointing to each other in the playground and saying ‘it wasn’t me it was him, miss’, ‘it wasn’t me it was him, miss’," she said.
Ms Hewitt added: "And to be honest watching the Nutrient Management Board meetings has been very similar."
Campaigners like her have been demanding action for years now.
And say whatever action has been taken by those charged with protecting the river so far, hasn’t made enough of a difference.
And the river is suffering as a result.
A spokesperson for the Environment Agency said: "We take our responsibility to protect the environment very seriously and are taking robust steps to reduce pollution in the River Wye.
"We’ve recently secured a share of £50 million in national Government funding which willenable us to achieve a step change in the regulation of agriculture in the Wye catchment."
"This funding means there will be a four-fold increase in the regulatory activity on the Wye.
They added: "Our teams will increase farm inspections and audits, focusing on high-risk locations and previously non-compliant businesses. We will also be able to carry out a detailed investigation into the management of poultry manure across the catchment and enhance monitoring at high risk locations."
Natural Resources Wales have been approached for comment.