Reported by the BBC

High visitor numbers are turning one of Britain’s most scenic lakes green, researchers say.

A report funded by the UK space agency suggests a link between peak tourist periods and algal blooming at Windermere in the Lake District.

Algal blooming is caused by warm temperatures and nutrients, and can make the water green and toxic.

Campaigners are linking the blooms to discharges of sewage, which although mostly treated, are nutrient-rich.

United Utilities, the local water company, insists its wastewater plants can cope with peak tourist periods.

Windermere is England’s largest lake and one of the country’s most popular natural attractions.

But in recent years, the normally clear water has been turning green due to algal blooming, particularly during the summer. Blooming is the rapid growth of algae and can lead to reduced oxygen levels in the water, killing fish and aquatic life.

Richard Flemmings from the environmental data company Map Impact, has been trying to work out why. He wanted to study whether the blooms are just the inevitable consequence of climate change and hotter, drier summers, or whether human discharges are also playing a role.

Both treated and untreated sewage discharges contain heightened levels of the key blooming nutrient phosphorus, from both human excrement and detergents.

“There is a significant correlation between visitor numbers and chlorophyll content,” Mr Flemmings says.

Chlorophyll is the compound present in plants that gives them their green colour and so an indicator of algal concentration. With funding from the UK space agency, Map Impact used infrared analysis of satellite images to measure chlorophyll levels over the last five years in Lake Windermere.

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