Mystery surrounds purple river

Officials from The Environment Agency have responded to reports that the River Mimram turned purple earlier in the week.

Reports of the discolouration surfaced on Monday, with MP Oliver Heald and rivers champion Feargal Sharkey tweeting the following day.

There were also reports that the River Lee turned a darker purple as if flowed through the Castle Grounds. The Mimram is a tributary of the Lee, with the rivers merging close to Hertford Football Club.

An Environment Agency spokesperson said on Wednesday: "We visited the River Mimram on Monday 18th October to investigate reports that a stretch of water had been polluted and turned purple. The water was no longer discoloured, and we took water meter readings which indicated no negative impact on water quality or the environment, and we found no evidence of harm to any fish.

"We took further samples of the river on Tuesday 19th October, will visit again today and will continue to monitor to ensure the good health of this chalk stream is maintained."

Chalk streams are a globally rare habitat, with more than 85% of all such streams found in England. They are important habitats for wildlife and support a massive range of plants and animals. There are a number of chalk streams in Hertfordshire including the Beane, Mimram and Lea. They are formed when rain falls in the Chiltern Hills before permeating layers of chalk aquifers and emerging through fissures as springs. The water is a stable temperature, mineral rich, crystal clear & pH neutral. These rare conditions create unique habitats for wildlife and support a huge range of plants and animals.

The government have recently launched a new strategy to protect chalk streams, with recommendations that include helping reduce pollution and eliminating over abstraction, as well as restoring physical habitat and biodiversity.