Early indications show a welcome reduction in the level of nitrogen pollution in Ireland's rivers last year, the Environmental Protection Agency has said.
The EPA's Early Insights Nitrogen Indicator suggests nitrogen concentrations have fallen to their lowest level in eight years.
High levels of nitrogen in rivers and waterways stimulates the overgrowth of algae and dense vegetation.
This blocks out sunlight and reduces oxygen levels in the water through a process called eutrophication, which harms aquatic ecosystems, threatens other plants and organisms, and degrades the water quality.
EPA Director of Evidence and Assessment Dr Eimear Cotter said: "Agriculture is the primary source of nitrogen in Irish rivers and there is significant action under way within the sector to improve water quality.
"It is therefore very welcome to see these early signs of improvement. It is important that the sector builds on this momentum and continues to implement actions to reduce nutrient losses in a targeted way."
Speaking on RTÉ's Morning Ireland, Dr Cotter said there has been a real focus on improving water quality in the agriculture sector for the last two years, with Teagasc running a water quality campaign and EU funding to encourage farmers to put better measures in place.
"Thing like better enforcement, compliance and enforcement, more inspections from local authorities, identifying what's going wrong on farms, and those issues being tackled by farms," Dr Cotter said.
Despite the reduction last year, nitrogen levels still need to come down further and, in particular, are still too high in the south and southeast of the country, she added.
Wastewater and sewage, industrial discharges, and urban runoff are also significant contributors to nitrate levels in rivers and waterbodies.
However, in Ireland, agriculture is by far the biggest source because of the use of synthetic fertiliser and the spreading of manure by farmers.
The overall improvement in nitrogen levels in 2024 follows a period of little positive change in recent years.
Today's report, however, highlights that nitrogen levels remain too high in rivers in the southeastern half of the country and says further reductions will be needed to bring them to satisfactory levels.
EPA Programme Manager Jenny Deakin added: "Further actions will be necessary to reduce nitrogen and phosphorus losses to levels which will support good ecological health in our water bodies.
"The ecology will not improve until nutrient levels are reduced in the areas where they are elevated. The EPA will be reporting on the ecological health of our waters later in 2025."
The Early Insights Nitrogen Indicator has been developed to provide more timely information on nitrogen levels and is based on monitoring data at 20 major and representative rivers.
