Wales' water watchdog is to carry out a review of the River Wye in an effort to understand the causes of algal blooms which campaigners say are harming the river.

Natural Resources Wales says it is to is carrying out a detailed review of data to better understand the causes of the increased blooms, and to inform a plan to improve the Wye's health.

Concern has mounted recently, including from Afonydd Cymru – the Welsh Rivers Trust – which pointed to the absence of swans and cygnets on the river, claiming that the blooms had affected the ranunculus weed on which they feed.

Earlier this summer, the Wye and Usk Foundation claimed that increased chicken farming along the course of the river was causing the blooms, which in turn was harming plant and animal life.

But local farmers reacted angrily, with the union saying its members felt "scarred and hurt" by the "reckless" claims. Natural Resources Wales also pointed to the impact of the warm spring weather as one of the key factors influencing the river's condition.

Water sampling data from the last 12 years is to be used in the new review to better understand the cause of the greater than usual blooms.

Ann Weedy, Mid Wales operations manager for Natural Resources Wales said: “People throughout the Wye catchment care deeply about the river, and rightly so.

“We are carrying out a detailed piece of work to better understand which combination of factors are causing the increased algal blooms.

“The review will look at all factors that can cause algal blooms including nutrient levels in the river from the last 12 years as well as looking at how changes in land use and agricultural practices may have affected the river.

“We will consider these findings alongside other factors that contribute to causing algal blooms including water temperature and river flow.

“This is a complex issue which has no single solution, but we are committed to protecting and improving the health of rivers across Wales including the Wye.”

NRW will publish a plan to improve the health of the river based on the review.

Last week the foundation released a new statement in which it said that the planning and regulation systems governing the river had impacted farmers as much as they had impacted the river.