A man hailed as a "colossus" for his work to protect rivers and wildlife has died, aged 69.
Environmentalist Dr Stephen Marsh-Smith led efforts to establish a network of rivers trusts across the UK, having created one of the first - the Wye and Usk Foundation, based in Powys.
He also co-founded the Angling Trust and was awarded an OBE for services to conservation.
Dr Marsh-Smith, born in Warrington, died on Saturday after a short illness.
Wye and Usk Foundation chief executive Simon Evans said the Welsh environment sector had lost a "force of nature", calling him a "colossus of the environmental movement".
"He was instrumental in the formation of the rivers trust movement and this idea of normal people getting involved in trying to look after their rivers in a way that statutory bodies were unable to do so," he said.
"Over time the government has seen us as a key delivery partner is trying to make things better. And we now have a say in how the environment is managed - that's a lasting legacy."
Dr Marsh-Smith, who lived in Erwood, Powys, set up the Wye and Usk Foundation - a charity that protects the ecology and fisheries of the two rivers - in 1996.
He was its chief executive until 2016, when he took on the same role with Afonydd Cymru - the umbrella body set up to represent Wales' six river trusts.
Chief executive of the Rivers Trust Mark Lloyd called him "a great man who achieved wonderful things".
Among his achievements were negotiating the use of reservoirs to top up river levels in the summer and creating new bankside habitats to allow salmon populations to recover from an all-time low level.
Dr Marsh-Smith also played a leading role in bringing fishing groups from across Wales and England together to form the Angling Trust.
He campaigned for tougher regulations to prevent pollution incidents and submitted a formal complaint to the EU Commission in 2018 about the Welsh Government's handling of agricultural pollution, describing it as "absolutely useless".
Born in Warrington, Stephen Marsh-Smith won a choral scholarship at the Llandaff Cathedral School in Cardiff.
It was in the Welsh capital that his interest in fishing started at Lisvane Reservoir, competing internationally as an angler.
In 2011 he was awarded an OBE for services to the environment and conservation of the rivers Wye and Usk.