Irish waterways damaged by nitrates, phosphates and algae, survey finds

An extensive survey of Irish rivers, lakes and canals has found a third of locations were littered, while significant pollution was being caused by nitrates, phosphates and algae.

A total of 30 Irish catchments were surveyed and 273 water samples taken by citizen scientists over four days in September under the direction of Dublin City University's Water Institute and the environmental group Earthwatch.

The WaterBlitz survey was an attempt to obtain a snapshot of the health of Ireland's waterways – similar surveys were conducted in Europe.

Almost a fifth of Irish rivers tested had high levels of nitrates caused mainly by fertilisers washed off land, according to preliminary results. When they are present in high concentrations they enrich the water, a process known as eutrophication, which leads to previously healthy lakes or rivers becoming choked with algae, severely depleting water-dissolved oxygen and eliminating aquatic life.

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Domestic sewage

Phosphates arising from fertilisers, detergents and domestic sewage also encourage growth of algae and can cause pollution. These were often present but at lower levels.

Dublin had the lowest levels of pollutants of the four European cities separately surveyed. The other cities were Paris, London and Luxembourg.

Among the most sampled water bodies in the capital were the Dodder river (79 sample points), the Liffey (67 points) and the Tolka (24 points).

"Many of our rivers, ponds, lakes and other water bodies across Europe are suffering from the effects of pollution and other human impacts. Many of these are not regularly monitored as there simply aren't enough scientists to carry out the level of monitoring needed," said project lead Dr Susan Hegarty.

Boil notice

"We've seen in the last week how fragile our water ecosystem is, with over 600,000 people in Dublin, Meath and Kildare having to boil their water due to a plant malfunction," she added.

“In addition to pollutants such as nitrates and phosphates, litter is a big problem in our water bodies . . . plastic in particular is incredibly problematic as it breaks down into microplastics that enter the food chain.”

Dr Hegarty is delighted with the level of participation in the first WaterBlitz survey. It is intended to build year on year on the work to establish a more complete picture of the health of Ireland’s water bodies.