The Environmental Protection Agency (EPA) has said that although there has been a reduction in levels of excess phosphorous and nitrogen in Ireland's rivers and lakes, the overall water quality of surface water is continuing to decline.
Its latest three-yearly assessment says almost half of Ireland’s surface waters are in an unsatisfactory ecological condition.
Excess nutrients from agriculture, urban wastewater and other human activities, and physical changes to habitats continue to drive the decline.
The report is based on information, collected over the six years to 2024, about water quality and pollution in almost 3,200 rivers, over 800 lakes, 160 estuaries, almost 100 coastal waters, 512 groundwater bodies, and 16 canals.
It says just over half, 52%, of all these water bodies are in satisfactory ecological health. This is down from 54% three years ago.
Estuaries and coastal lagoons were worst, with 70% deemed unsatisfactory.
Underground water sources and canals fare best with about 90% satisfying water quality standards.
However, only 1,523 out of 3,189 rivers passed the quality test as set out in the Water Framework Directive.

This means more than half of Ireland’s rivers failed.
Damage from activities such as land and river drainage, forestry and urban development are partly to blame.
There have been improvements in the level of phosphorus pollution from agriculture and urban wastewater in areas prioritised for targeted interventions, and nitrogen levels in many river sites have declined.
Nevertheless, levels of both nutrients are still too high and further reductions are needed according to the report.
Rivers, lakes and estuaries 'struggling'
Dr Eimear Cotter, Director of the EPA’s Office of Evidence and Assessment, said: "Our rivers, lakes and estuaries are the lifeblood of our landscape and support our ecosystems, and our health and wellbeing.
"But they are struggling. They do not have the resilience to cope with the challenges they face, now and in the future."
"It is very disappointing to report that water quality is not improving despite the many actions that are underway, across all sectors. It’s clear the scale and pace of implementation needs to be increased and sustained," she added
The Sustainable Water Network, SWAN, a coalition of twenty-five environmental organisations focussed on water, said it is deeply concerned by the findings.
It is calling for more robust and urgent policies to address the ongoing and persistent deterioration in water quality.
SWAN said this is a crisis that threatens aquatic habitats and species, including the iconic salmon populations and the endangered freshwater pearl mussel, whose survival depends on clean, thriving waters.
Advocacy and Communications Manager, Antóin McDermott, said: "Despite government rhetoric, the real improvements needed to restore our rivers, lakes, and seas to good health just aren’t happening after over fifteen years of decline. When will the government finally treat this as the crisis it is?"
"Rather than focusing on getting pollution derogations from the European Commission, they need to prioritise far stronger measures, delivered with the full urgency it requires", he said.