Nitrogen levels in rivers increased by 10% in 2025 according to a new report published today (Thursday, March 19) by the Environmental Protection Agency (EPA).

Based on data from 20 monitoring sites across the country the EPA found that nitrogen levels in the south‑eastern half of the country are "too high to support good ecological health" in water bodies.

According to the agency the primary source of nitrogen in Irish rivers is agriculture and said this is from "excess losses of nitrogen in chemical and organic fertilisers".

The latest Early Insights Nitrogen Indicators report published by the EPA sets out the latest assessment of nitrogen levels in Ireland’s major rivers for the period January to December 2025.

The agency also carries out a full assessment of the overall quality and ecological status of Ireland’s waters every three years.

According to Pat Byrne, director of the EPA’s Office of Radiation Protection and Environmental Monitoring, its latest report highlights "the continued pressure on water quality".

He also warned that the latest assessment of nitrogen levels in major rivers from January to December last year "underlines the need for sustained, targeted action to reduce losses of nitrogen used in agriculture, particularly in higher‑risk catchments in the southeastern half of the country. "

EPA

The agency said that nitrogen levels can fluctuate due to a combination of factors including weather patterns, agricultural land management and inputs of nitrogen to the environment.

Different factors may be also be dominant in different catchments, depending on its physical characteristics.

But specifically in relation to 2024 and 2025 the EPA identified a number of key factors which it said had influenced nitrogen concentrations.

One of these was fertiliser sales because although sales do not directly correlate with losses of nitrogen to the environment according to the EPA they are "a factor in increases in nitrogen concentrations in waters".

Statistics from the Department of Agriculture, Food and the Marine (DAFM) show fertiliser nitrogen sales increased by 10.6% in 2024 compared with 2023, followed by a further 12.5% increase in 2025.

But another factor identified by the EPA in relation to nitrogen concentrations was that overall 2025 was wetter than 2024.

"The weather patterns in 2024 and 2025 were mixed, with relatively normal nutrient transport conditions in 2024 and the potential for increased nutrient transport in the latter part of 2025, which may increase nutrient levels in 2026 and beyond," the EPA outlined.

The EPA has published a map (see below) which shows the nitrogen levels in the catchements which require or have previously required "nitrogen load reductions" to achieve water quality objectives (areas in purple below).

According to the agency these are "primarily located in the east, south and south-east of the country".

The map also identifies catchments where nitrogen concentrations are "consistently below levels that impact on ecological health" (areas in cream).

According to the EPA these are primarily located in the west and northwest of the country.

The agency also said that in both groups of catchments, nitrogen levels have increased in 2025, relative to 2024.

"This highlights the role of nationally applicable factors influencing nitrogen levels, such as climate and fertiliser price for example, as well as more locally relevant factors such as farmpractice," the EPA stated.