Almost half of Ireland’s rivers have unsatisfactory water quality levels due to high concentrations of polluting nitrogen, according to a new analysis.
The Environmental Protection Agency’s (EPA) latest water indicators report found that overall water quality improved for 345 rivers nationally across 2019 and 2020, but there was a decline across 230 other rivers. These deteriorations are “off-setting the improvements made”, the report notes, and “essential” action must be taken to prevent further harm.
The main threat to water quality is high levels of nitrogen and phosphorus arising from agriculture and waste water discharges. These nutrients affect a water body’s ecosystem, causing algal blooms that displace other flora and fauna. High nitrate levels in drinking water supplies pose a risk to human health.
Nitrogen levels are too high in 47 per cent of Irish rivers, in a quarter of groundwaters, which is a critical source of drinking water, and a fifth of estuarine and coastal water bodies. The nutrient is growing in concentration at 38 per cent of river sites, while volumes of phosphate are increasing at a quarter of them.
Nitrate levels are intensifying in rivers, groundwater and estuaries in the south and southeast, primarily due to agricultural activities through chemical and organic fertilisers. Parts of the east of the country have higher nitrate levels associated with urban waste water discharges. Areas of particular concern include the rivers Bandon, Lee, Barrow, Suir and Liffey.
The EPA’s director of evidence and assessment, Dr Eimear Cotter, noted that nitrogen levels at these rivers have “significant implications” for the marine environments they flow into.
“We urgently need to address nitrogen pollution so that we can protect and restore the water quality in these areas,” she said.
The EPA assessment also shows that 29 per cent of rivers and 30 per cent of lakes have unsatisfactory phosphate levels, including the Liffey, Dublin Bay, Nanny-Devlin and Shannon Estuary South catchment areas.
The majority of lakes in poor or bad condition for phosphorus are situated in the Erne catchment in the northeast, where agriculture is a significant pressure, and measures are needed to reduce these pressures, the report states.
In the period from 2017 to 2020, 57 per cent of river bodies scored high or good for quality. The number of water bodies in bad condition reduced to two (the Maigue Estuary and Deel Estuary in Co Limerick), down from 91 in the late 1980s.
While acknowledging an overall net improvement in the biological quality of rivers monitored in 2019 and 2020, the EPA’s Mary Gurrie said the scale of declines elsewhere is “hampering progress”. Action is “essential” to ensure continued improvements and the prevention of further deterioration, she said.