An algal bloom, similar to those which struck Lough Neagh and the Blessington Lakes in Co Wicklow in recent weeks has been observed in the Vartry Reservoir, near Roundwood, also in Co Wicklow.
The Vartry water supply scheme provides drinking water for homes and businesses from Roundwood, through north Co Wicklow and south Co Dublin, serving more than 200,000 people.
Uisce Éireann has said there is no danger to its customers as water is treated before distribution.
However the bloom which appears as luminous green / blue slick can poison fish, birds and dogs and toxins given off by the blooms of blue green algae can cause sickness, itching and skin rashes in humans.
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Algal bloom at the lakes in Blessington and Lough Neagh resulted in the loss of fish and bird life, and in some cases dogs that swam in the water died. Earlier this year an algal bloom in Lough Melvin which straddles the border between Co Leitrim and Co Fermanagh was blamed for the death of up to six dogs.
Similar blooms have been discovered across the island for more than two decades. As far back as 2000 beaches on Lough Derg in Co Tipperary were closed due to the discovery of algal blooms. The growths are sparked by warm weather and by exaggerated levels of phosphates and nitrates entering the lake from agricultural, industrial and domestic sources.
Wicklow TD Jennifer Whitmore, who drew attention to the bloom in the Vartry reservoir, told The Irish Times: “It is clear we have a serious problem with the enrichment of our waters”.
She said the problem was now “impacting our lakes and drinking waters and this problem is getting worse”.
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“Government must immediately outline measures it is taking to prevent any more important water supplies, recreational waters and important biodiversity systems being impacted by what is a man-made problem”, she said.
Dr Elaine McGoff, head of advocacy with An Taisce, said the appearance of the algal bloom at Vartry was “a further indication of the decline of the water quality in our lakes and rivers”. She said warning signs of the damage being done to Lough Neagh were visible for a decade. “These are our warning signs, if we do not take notice of them we are facing into serious, Lough Neagh-style pollution across our lakes and rivers”.
