Groundwater pollution

Groundwater pollution

​Groundwater is a major natural resource in Ireland providing between 20-25% of the drinking water supplies. In some counties this percentage can be much higher and in rural areas groundwater is the only source of drink water due to lack of access to public or group water schemes. This groundwater is accessed by wells and springs with over 100,000 of them in use. With so many people relying on groundwater it is vital that this natural resource is protected.


Groundwater pollution occurs when harmful substances enter the groundwater. These pollutants are practically limitless but can range from motor oil to chemicals from agriculture to untreated waste. Unlike surface water pollution groundwater pollution is harder to detect and control which may cause the problem to persist for long periods of time.


For more on groundwater resrouces in Ireland please go to our Groundwater programme pages

Untreated waste from septic tanks or sewerage systems may leak into the surrounding soils and enter aquifers where they mix with the groundwater that serve local wells. 

This untreated waste carries bacteria along with nitrates and organic chemicals into the groundwater which could be very harmful if consumed.


Landfills contain many sources of pollution, after heavy rain these pollutants seep into the soil below them.

These leached pollutants then enter aquifers contaminating the groundwater with harmful chemicals and heavy metals such as lead and cadmium. These pose serious health risks to humans and animals.


Agriculture can also adversely affect groundwater quality. The spreading of slurry, fertilisers and animal waste on the land can result in pollutants such as nitrates and bacteria seeping into underground water sources. These pollutants can have serious adverse effects on the plants, animals and people who rely on these water sources.


Mining and Quarrying can release pollutants previously trapped in the rock into surrounding underground water sources. Chemicals such as iron, aluminium and sulphates can seep into the groundwater and make it dangerous for consumption.


By studying aquifers and the flow of water in them, known as hydrogeology, we can make better decisions in where to locate these industrial sites.


It is also important to study the underlying structures of an area to understand that these pollutants can travel long distances underground. In karst regions the groundwater can travel many kilometres in underground channels in the limestone before surfacing.