Natural Resources Wales (NRW) has found no direct link between poultry units and high phosphate levels in the River Wye.
Stringent new targets introduced to safeguard the river environment and counter the impacts of climate change saw over 60 per cent of the River Wye and its catchments fail against water quality standards.
Conservationists had blamed chicken excrement from free-range poultry farms near the bank of the river for algal blooms in the water, with a number of national news reports published on the claims earlier this year.
But the regulator found no evidence to support the allegations.
Gavin Bown, head of Mid Wales operations for NRW said: “NRW knows how passionate people are about safeguarding the health of the River Wye.
“We share that passion and strength of feeling and we are committed to working with stakeholders along the course of the river to do all we can to improve the river’s health.
“There were concerns that phosphate levels were associated with poultry units, but we have not found a direct connection between the two elements.
“The reasons for failure on the river Wye and its tributaries are likely to be from a diverse range of sources, including mains sewerage and septic tanks, misconnections and agricultural practices.”
NRW is now working with planning authorities in the Wye catchment – Powys, Brecon Beacons Natural Park Authority and Monmouthshire – to help them understand what the findings mean for their processes.
Each and every project, plan or permit in the area will now have to demonstrate it has a neutral or better impact on reducing phosphate levels in the Wye and its tributaries.
Ruth Jenkins, NRW’s head of natural resource management policy said: “We all have a part to play to make sure Wales’ rivers are healthy for future generations and we want to work with others to find innovative solutions.
“Each river and section of rivers may need different approaches and we will work with people locally to create local solutions.”