A £1m fund to investigate the sources of pollution in the River Wye has been jointly announced by the Welsh and UK governments.
Labour ministers in Westminster and Cardiff said the cash would allow for a “comprehensive cross-border research programme”.
Local farmers, environmental groups and citizen scientists would “play a crucial role” in the work, they added.
The Wye and Usk Foundation welcomed the announcement but said there was “an awful lot to do” to help the river recover.
It follows a decision by the UK government not to continue with a £35m action plan for the river announced by the Conservatives before the election, but to develop its own proposals.
The river, which flows from mid Wales to the Severn Estuary, is protected by sites of special scientific interest and is also a designated special area of conservation.
In recent years it has become symbolic of widespread concerns over the state of the UK’s rivers, having been downgraded to “unfavourable – declining” status by Natural England.
Campaigners warn that agricultural and sewage pollution combined with the impacts of climate change have led to algal blooms, starving wildlife of oxygen.
More than 2,000 local people and businesses have joined a class action lawsuit against firms involved in large-scale poultry farming locally along with Welsh Water.
About 24 million chickens, a quarter of the UK’s poultry production, are raised in the river’s catchment area.
Meanwhile, pressure for action from both the UK and Welsh governments continues – with Herefordshire MPs recently proposing a new law to mandate a clean up of the river.
Simon Evans, chief executive officer of the Wye and Usk Foundation said the river suffered from a complex set of problems.
“We’re having too many high flows, too many low flows, we’ve got too many nutrients, pesticides and soil in the river,” he said.
There was “very little money” for monitoring and investigation work at the moment so “if this £1m is coming in there it will be incredibly well-spent,” he added.
“If you can start to understand your problem and quantify it then you can start to take bite-sized chunks out of it with your activities in the catchment.”
But there was “an awful lot to do” and the work of restoring the river could take years, he warned.
Both governments are to contribute £500,000 each to the new research fund.
The Welsh deputy first minister Huw Irranca-Davies MS, and the UK government’s water minister Emma Hardy MP, will make the announcement on a visit to the river to meet local groups and politicians on Tuesday.
The research programme will investigate pollution sources and pressures affecting the river, the ministers said.
It will also study the impacts of changing farming practices, develop and test new ways to improve water quality and examine drivers of wildlife decline and water flow.
Irranca-Davies branded it “an important step to protect the River Wye”.
“By bringing together expertise from both sides of the border and working closely with local groups, we can better understand the challenges facing the river and find the solutions that will make a difference,” he added.
Hardy said the River Wye had suffered from “extreme pollution” for too long, with “devastating effects on wildlife and impacting all those who live along its banks”.
The new initiative built on other work including an ongoing £20m project addressing phosphorus levels in soil through the Land Use for Net Zero, People and Nature programme, she added.
Welsh Conservative shadow climate change secretary Janet Finch-Saunders, called the £1m set aside for the fund a “very, very small drop”.
She argued it “would be better spent on upgrading water treatment plants beside watercourse in Wales”.
