Why a river at a Cornwall nature reserve has turned bright green

The river had been dyed entirely green Credit: Aiden Zralka

A river running through a nature reserve in Cornwall has been turned bright green - because of water testing in the area.

People visiting Swanvale Nature Reserve in Falmouth were left concerned when the stream running through it turned a bright green.

Keyleigh Tree told ITV News she feared it may impact local wildlife - but the Falmouth Green Corridor confirmed it was caused by a dye used to test for water leaks in the area.

"I was shocked to discover the stream showing a luminous green colour," Keyleigh said.

"I couldn't believe my eyes, the stream looked radioactive and polluted. As I walked further on down the stream I noticed it was still green and pouring in the the actual lake.

"I was worried about the wildlife especially the marine life in the stream."

But Jennifer Carter from Falmouth Green Corridor said it is a harmless green dye used by South West Water to test for leaks.

"It can look very alarming but is nothing to worry about," she said.

"Members of the Falmouth Green Corridor are working with West Country rivers trust to regularly monitor the stream with water quality surveys.

"We are also launching the yellow fish campaign next week, which will raise awareness about pollution and educate people about what should and shouldn’t go down surface water drains."