EPA’s assessments of water quality and agriculture
Learn more about the EPA's assessments of water quality and agriculture.
The EPA's role in water quality
Understanding water quality improvements in agricultural areas
EPA's roles and responsibilities
The EPA's role in water quality
The EPA's purpose is to protect, improve and restore the environment through regulation, scientific knowledge and working with others. For water quality, the EPA's responsibilities include:
- monitoring the quality of Ireland's rivers, lakes, estuaries, coastal waters and groundwater
- Assessing the impact of human activities and pressures on water quality
- provide scientific advice and evidence to support environmental policy
- regulation of wastewater, industrial and waste activities and oversight of local authority performance of their statutory environmental functions
- reporting to the Commission under a range of directives including the Water Framework Directive, Nitrates Directive and the Bathing Water Directive
The EPA oversees and implements the national water quality monitoring programme. The programme is designed to assess the overall condition of our rivers, lakes, canals, estuaries, coastal waters and groundwaters and to meet the requirements of the Water Framework Directive and Nitrates Directive. Full details of the monitoring programme is available on our website Water Quality Monitoring Programme for the period 2022-2027.
Water quality objectives?
The overall aim for water quality is for all rivers, lakes, estuaries, coastal waters and groundwater to achieve good or high ecological status.
Water bodies with good or high ecological status are close to their natural condition and need to be protected. Water bodies with moderate, poor or bad status have been affected by pollution or habitat damage and require action to improve their condition.
See our Factsheet - How we assess water quality for further information.
How many waterbodies are there and how many get monitored?
There are over 4810 surface and groundwater bodies in Ireland. This includes over 500 groundwater bodies, 3200 rivers, 800 lakes, 200 transitional waters, and 110 coastal waters.
Approximately 2900 (60%) of these waterbodies are monitored including 121 groundwater bodies, 2429 rivers, 224 lakes, 80 transitional waters and 45 coastal waters. There are also 16 canal waterbodies on the monitoring network.
Where monitoring data are not available, we assign ecological status using other methods. Explore further information on assigning status to unmonitored waters.
What does EPA monitor?
The EPA monitors the condition of Ireland's waters, including rivers, lakes, estuaries, coastal waters, groundwater, canals and heavily modified water bodies.
Monitoring data is used to assess the ecological and chemical status of surface waters, and the chemical and quantitative status of groundwater.
For surface waters, the programme includes:
- biological elements such as invertebrates, fish, algae and aquatic plants
- physio-chemical quality elements, e.g. nutrients, dissolved oxygen, pH and temperature
- chemical substances such as pesticides and metals
- physical habitat condition (hydromorphological) of water bodies.
Factsheets on different elements of the monitoring programme are available here:
EPA's water quality findings
How is water quality in Ireland overall?
The EPA publishes a full assessment of the condition of our waters every three years. The latest Water Quality in Ireland assessment is for the period 2019-2024. This assessment shows that over half (52%) of our surface waters are in good or high ecological status which means that nearly half (48%) are in unsatisfactory condition. Overall, our water quality has been declining since the 2010-2012 assessment.
The Water Indicators report for 2025 reported no major change in water quality in 2025. Nutrient levels remain too high in a large proportion of water bodies. Levels fluctuate year on year but are not improving overall over the long term. The biological health of our rivers and lakes has shown little change with slightly more than half (54%) in good or better biological quality.
What are the main pressures on water quality?
Our water quality is impacted by:
- excess nutrients (nitrogen and phosphorus) coming mainly from agriculture and urban waste water discharges, and
- the damage that various activities such as land drainage and urban development do to the physical condition of our water habitats.
Excess nutrients from agriculture, urban wastewater and other human activities remains the biggest challenge, followed by changes to physical habitat conditions.
How does the EPA assess what activities are impacting on water quality?
The EPA uses monitoring data and other environmental information to identify the activities that are affecting water quality.
We examine water quality results alongside information on factors such as agriculture, wastewater discharges, forestry, industry, land use and population. This helps us identify the most significant pressures on individual water bodies and catchments.
Our assessments are informed by scientific evidence and are supported by information from organisations with local knowledge, including local authorities, the Local Authority Waters Programme and Inland Fisheries Ireland.
What is the impact of too much nitrate and phosphorus in our waters?
Nitrate and phosphorus help plants grow. Too much of these nutrients in water can cause over growth of aquatic plants and algae which leads to eutrophication. The excessive growth out-competes other plants, uses up dissolved oxygen, and blocks light to deeper waters, leading to imbalances in the ecosystem.
Both phosphorous and nitrogen play a role in eutrophication. The general rule is that phosphorus is of most concern in our freshwaters, and nitrogen is of most concern in estuaries and coastal waters.
What are the standards for nitrate?
Different nitrate standards that apply in different circumstances, depending on what is being protected.
Ecological standards in rivers
To support good ecological water quality, nitrate concentrations in rivers should remain below levels that can harm aquatic ecosystems. EPA assessments indicate that nitrate levels should be less than 8 mg/l NO3 (or 1.8 mg/l as N) to support good water quality in our rivers.
Ecological standards in marine waters
Nitrate standards are also used to protect the ecological health of estuarine and coastal waters. The standard to protect the ecological health of marine waters is 11.5 mg/l as NO3 (or 2.6 mg/l as N).
Drinking water standards
A separate drinking water standard is used to protect public health. This standard sets a maximum allowable nitrate concentration of 50 mg/l NO₃ in drinking water supplies. The threshold level of 37.5 mg/l as NO3 as an average concentration is set to minimise the risk that the maximum concentrations will exceed 50 mg/l as NO3.
Why are there different standards?
The nitrate levels needed to protect aquatic ecosystems are generally lower than those required to protect drinking water supplies. As a result, a water body may meet drinking water standards while still experiencing ecological impacts from elevated nitrate levels.
What nitrogen reductions are needed to improve water quality?
Each catchment has a limit to the amount of nitrogen it can absorb while maintaining good water quality. Where this limit is exceeded, nitrogen concentrations can increase and affect rivers, lakes, estuaries and coastal waters.
The amount of nitrogen entering water varies between catchments and from year to year. It is influenced by factors such as land use, weather conditions, soil characteristics and rainfall patterns.
As a result, the level of nitrogen reduction needed to achieve water quality objectives can vary across different catchments. EPA assessments help identify areas where nitrogen levels are elevated and where measures may be needed to reduce pressures on water quality.
For more detailed information on catchment assessments and water quality, visit Catchments.ie
Find water quality information
Catchments.ie provides information on Ireland's catchments, the pressures affecting water quality and actions to protect and improve local waters.
Beaches.ie provides information on bathing water quality, beach locations and monitoring results for designated bathing waters across Ireland.
Understanding water quality improvements in agricultural areas
What is the EPA's Farm and Landscape measures for Agriculture map?
The EPA's Farm and Landscape measures for Agriculture map has been developed to help address the specific water quality issues arising from agricultural run-off in waterbodies that are not meeting their water quality objectives.
- nitrogen losses
- phosphorus losses
- sediment run-off
- farmyard and other point source pressures
How long does it take for water quality to improve?
The time it takes for water quality to improve depends on several factors, including farming practices, soil type, weather conditions and local catchment characteristics.
Research from the Teagasc Agricultural Catchments Programme (McAleer, 2022) demonstrates the importance of long-term action to improve water quality. While some improvements can be seen within a relatively short period, the recovery of aquatic habitats and ecosystems may take longer. Measures to reduce nitrogen losses are most effective when targeted to areas where the risk to water quality is greatest.