Experts say green water in reservoir poses no risk

Jersey Water reassures public after green hue spotted at reservoir

Concerns over bright green water at Queen’s Valley Reservoir have been addressed by Jersey Water, which confirmed the unusual colour was caused by a natural process and posed no risk to public health.

A photograph shared on social media showing the discoloured water prompted questions from Islanders, with one user commenting that it “did not look good to drink.”

Jeanette Sheldon, the company’s head of water quality, explained that the colour change was the result of an algae bloom triggered by warm summer conditions.

“Algal blooms are a natural occurrence. While they may look worrying, they are not harmful, and all water drawn from the reservoir goes through full treatment before it reaches taps,” she said.

Ms Sheldon outlined the treatment process, which begins with small doses of chemicals to clump together algae, silt and sediment. The water is then passed through sand filters to remove particles, followed by disinfection to eliminate any remaining bacteria before distribution.

Queen’s Valley, owned by Jersey Water, remains open to walkers. Earlier this year, parts of the site were closed due to a rat infestation, which the company linked to visitors feeding wildlife. The reservoir fully reopened in July.

Holding up to 1,193 megalitres of untreated water, Queen’s Valley is the Island’s largest reservoir—enough to supply Jersey for around 48 days.