Over the past five years, the state of Ireland’s rivers, lakes and estuaries has declined. A recent Environmental Protection Agency (EPA) report paints a worrying picture: 48 per cent of Irish water bodies now fail to meet Environmental Quality Standards (EQS). In other words, nearly half of Irish aquatic ecosystems are not as healthy and resilient as they should be.
Across the country, two thirds of estuaries, half of rivers and one-thirds of lakes fall short of “good” or “high” ecological status. Compared with the previous assessment made between 2016 and 2021, water quality has deteriorated by two per cent. The trend is not uniform, however: some water bodies became healthier and cleaner, marking a 14 per cent national improvement, but this progress was offset by a 16 per cent decline elsewhere. Coastal waters and groundwaters showed the greatest recovery, while rivers, lakes, estuaries and canals experienced the steepest deterioration. Estuaries suffered the most: their water quality dropped by five per cent, mainly in the south and southwest.
Regional differences are striking. Co Mayo and Co Wicklow stand out, with over 70 per cent of rivers in satisfactory condition. In contrast, Co Kildare, Louth and Meath demonstrate the poorest results – fewer than 20 per cent of rivers meet acceptable standards, and none are rated as high quality. Dublin performs only slightly better, with just two of its 34 rivers achieving high ecological status. When it comes to lakes, the cleanest are mostly found in the southwest, west and northwest, while the northeast records the lowest scores.
Behind these statistics lie wastewater discharges and nutrient runoff as the dominant pressures on water quality, followed by physical alterations. These factors drive oxygen depletion, habitat loss and toxic contamination, undermining aquatic habitats. “Our rivers, lakes and estuaries are the lifeblood of our landscape and support our ecosystems, and our health and wellbeing”, said Dr. Eimear Cotter, Director of the EPA’s Office of Evidence & Assessment. “But they are struggling. They do not have the resilience to cope with the challenges they face, now and in the future.”
Chemical pollution
Not a single Irish site achieved good chemical status. Most failures stem from mercury and poly brominated diphenyl ethers (PBDEs) – long-lasting ubiquitous substances found almost everywhere in the environment. Without them, 82 per cent of Irish waters would pass the chemistry quality benchmark.
PBDEs are synthetic flame retardants once widely used in products ranging from furniture, paints and textiles to cables and the plastic casings of computers, televisions and remote controls. As endocrine disruptors, PBDEs have been linked to thyroid disorders, reproductive dysfunction, type II diabetes, obesity, metabolic syndrome and certain cancers. Although banned in the EU, Australia and the US several years ago, older or imported products may still contain them. Once discarded, these items release PBDEs into the environment, posing risks to both human health and wildlife.
In Ireland, the issue is compounded by a decline in e-waste recycling rates. Only 43 per cent of electronic waste was recycled in 2023, dropping by one-third in just two years. This figure falls well below the EU target of 65 per cent, raising concerns about PBDEs leakage from improperly discarded electronics.
Mercury, another ubiquitous substance, is a toxic metal contained in some batteries, fluorescent light bulbs, thermometers and thermostats. It is emitted during the burning of coal, oil, wood and waste, as naturally occurring mercury vaporises into an invisible, odourless gas. Other sources releasing mercury include historic mining places, factories and wastewater plants with inadequate filtration. Mercury exposure poses serious risks, particularly for children, as it can impair their abilities to think and learn. In wildlife, it can hamper reproduction, growth and development, threatening population stability.
Despite mercury EQS exceedances, EPA assures that most Irish fish is safe for human consumption provided food safety guidelines are followed. As for PBDEs, no equivalent food regulatory standards are developed yet.
Nutrient runoff
While nutrients boost farm yields, they are a disaster underwater. Runoff containing nitrogen and phosphorus overfertilizes water, stimulating algae or algae-like bacteria growth. When decomposing, these organisms use up oxygen, leading to mass fish deaths and the formation of “dead zones”. To make things worse, “algae green blankets” also block the sunlight, halting photosynthesis and further depriving the water of oxygen. In some cases, blooms consist of toxic cyanobacteria mimicking algae, which make fish from polluted sites unsafe for human and animal consumption.
Over the past five years, more than one third of rivers have shown reduced nitrate concentration, indicating a promising sign of improvement. However, the progress has been fragile: nitrogen losses to waters dropped in 2024, only to rise again by 16 per cent in early 2025. Dr. Eimear Cotter described this setback as “very disappointing”. Nitrogen loadings are particularly high in the south, east and southeast – regions with intensive dairy farming and the majority of derogation farms.
Phosphate concentrations remain elevated in over a quarter of rivers and a third of lakes, especially in the northeast. Although levels have fallen since 2021, they remain above ecological targets. Moreover, progress in lakes and rivers has been outshadowed by a strong increasing trend elsewhere, most notably in the east and southeast.
The way forward
Under EU law, Ireland is required to restore all water bodies to satisfactory ecological condition by 2027. Yet, EPA considers this goal unrealistic. Despite the introduction of mercury limits, nutrient controls and bans on PBDEs, the measures have not been sufficient to reverse the decline.
EPA Programme Manager Dr. Jenny Deakin warns that the ecological health of Irish waters will not improve until nutrient levels are reduced. Agriculture remains the main driver of nutrient pollution, accounting for 85 per cent of nitrogen loadings in rural catchments. Its role will be central to any meaningful recovery, and Dr. Eimear Cotter stresses the importance of the farming sector taking action to curb nutrient losses.
One of the greatest challenges is applying the right measures in the right place. While significant phosphorus reductions have been achieved in some priority areas, nitrate progress remains uneven. Dr. Elaine McGoff, Head of Advocacy with An Taisce, notes that certain strategies working well for phosphorus and silt have proven ineffective for nitrogen, underscoring the need for nutrient-specific approaches. Professor Frank O’Mara, Director of Teagasc, adds that Ireland’s diverse landscape rules out a one-size-fits-all solution. He explains that local variations in weather, soil type and river structure all affect nutrient losses to water, making regionally tailored measures essential. For instance, phosphorus levels are highest in places such as Co Limerick, Co Monaghan and the areas northwest of Co Dublin and Co Wexford, where poorly draining soils exacerbate nutrient buildup.
Dr. Deakin mentions another major weakness – the lack of detailed information on where and when actions are implemented. “It is essential that all stakeholders collect data on measures taken on the ground,” she said, “to provide better information on how the progress can be accelerated.” The EPA stresses that improved data sharing between implementing bodies, water quality programmes and state agencies is vital for the effective monitoring of measures and activities.
Ultimately, Dr. Cotter believes that both the scale and pace of implementation must be increased and sustained, while Dr. McGoff calls for a fundamental change in approach. “We now need a step change in how we manage our waters and how we manage our land and wastewater”, she said. “We can’t keep doing largely the same thing and expecting a different outcome.”
