Almost half of rivers across Ireland have unsatisfactory nitrates levels, with 43% of river sites showing elevated concentrations.

According to the Environmental Protection Agency’s (EPA) report on water quality in 2025, a three-year assessment from 2023 to 2025 of nitrates concentrations at 1,239 sites showed that levels remained largely unchanged.

A large proportion of these rivers are located in the east, southeast and south of the country.

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Over one-fifth (22%) of groundwater monitoring sites had exceedingly high nitrates levels, with no change in average nitrates concentrations between 2024 and 2025.

Since 2010, nitrates concentrations in groundwater in the southeast, midlands and east and southwest regions have been consistently above levels that are needed to protect surface water ecology.

One in five estuaries and coastal water bodies were found to be in an unsatisfactory condition for dissolved inorganic nitrogen, with all exceedances occurring in estuaries along the eastern and southern coasts.

The largest contributions of nitrogen to the marine environment came from catchments in the southeast of the country, with 2025 levels higher than recent years.

Phosphorus

Almost one-third of lakes and rivers have too much phosphorus, according to assessments from 2023 to 2025.

In rivers, 27% had phosphate levels that were too high from 2023 to 2025, with little overall change in three-year average levels, despite some annual fluctuation.

Some 31% of lakes continue to have unsatisfactory total phosphorus levels, with the majority located in the border region.

Nearly all estuaries and coastal waters met phosphate standards standing at 97%, with only three estuaries in the southwest remaining in unsatisfactory condition, representing no change since the previous assessment.

Phosphorus loadings to the marine environment have remained mostly stable in recent years, despite a slight increase in 2025.

Key findings

Overall, 46% of rivers in Ireland ranked moderate, poor or bad in biological quality, while 54% rated high or good.

Three water bodies were in bad condition, including stretches of the Folies stream within the River Laune catchment in Kerry, the Ahavarraga stream in Limerick and the Clareen, a tributary of the Nenagh River in Tipperary.

Overall, 717 river water bodies were assessed in 2025 - of these, 90 improved in quality, 109 declined in quality, while 515 remained unchanged.

As in recent years, any localised improvements in biological quality have been offset by declines elsewhere.

More than half (54%) of monitored lakes were in high or good biological condition in 2023 to 2025, a 2% increase on 2022 to 2024.

Lake biological quality has remained relatively stable since 2007. Eleven lakes were in bad biological quality.

A positive improvement was observed in the Ballyteigue Bannow catchment in Wexford, where six of the 16 rivers assessed in 2025 improved in biological quality.

Bigger picture

Overall, there has been little change in water quality indicators in 2025, with water quality remaining unsatisfactory in many areas, according to the EPA.

It said that excess nutrients from agriculture and wastewater remain the greatest challenge to water quality improvements, as phosphorous and nitrates levels are still too high in many waterbodies.

Some areas showed promising improvements. However, these are being offset by declines elsewhere. The scale and implementation of actions to improve water quality needs to be increased, the EPA has said.

“Ireland’s water quality is not improving overall and that should concern all of us. The decline in high-status water bodies is a serious warning sign,” director of the EPA’s office of evidence and assessment Roni Hawe commented.

“Clean water underpins healthy ecosystems, safe drinking water, recreation and local economies.

“Targeted action and measures tailored to the specific challenges affecting each water body must be accelerated to shift the overall trend towards improving water quality.”