Groundwater is water located beneath the ground surface in pore spaces and fractures of geologic formations. If the geologic formation can yield enough water for a significant water supply then the term aquifer is often used. The study of groundwater distribution and movement is commonly termed hydrogeology.

In contrast with most other EU countries, the bedrock aquifers in the Republic of Ireland have fissure permeability only. Most of the bedrock aquifers are unconfined. The majority of the "Regionally Important" aquifers are karstified limestones, with a high proportion of conduit flow.

The sand & gravel aquifers that underlie approximately 2% of the country are the only aquifers with intergranular permeability. These aquifers are usually unconfined and generally are relatively thin, typically between 5 - 15m saturated thickness.

Water is usually abstracted from these aquifers by pumping from wells or boreholes, although water may also seep to the surface via springs. Well depths in the bedrock aquifers typically range between 30 - 100m below the surface. The water from well or borehole abstractions is generally a composite of water from all fractures and/or conduits throughout the total length of bedrock in the borehole.

Anthropogenic Impacts on Groundwater

Conceptual understanding of the hydrogeological system and the impact of pressures on groundwater in the Republic of Ireland was used to prepare the Article 5 Characterisation and Risk Assessment Report for the Water Framework Directive (WFD). This report identified groundwater bodies that potentially have groundwater quality or over-abstraction problems, and monitoring data are required to verify the risk assessment in this report and help determine the status of each groundwater body.

The Environmental Protection Agency have published Guidance on the Authorisation of Discharges to Groundwater. This document provides guidance on the technical assessments that are needed to authorise discharges to groundwater, as a means of satisfying the requirements of the European Communities Environmental Objectives (Groundwater) Regulations, 2010 (S.I. No. 9 of 2010).

Groundwater Monitoring

Historically groundwater monitoring in the Republic of Ireland focused on the protection of drinking water supplies and investigating the impacts of point source pollution. However, the WFD and the EU Directive on "the Protection of Groundwater Against Pollution and Deterioration" (Groundwater Directive) adopt a more holistic view of water resources, establishing links between groundwater and associated surface water and ecological receptors. Therefore, groundwater monitoring networks have been developed to improve knowledge of, and the links between, groundwater and the ecological health of associated receptors.

The National WFD Groundwater Monitoring Programme is implemented by the Environmental Protection Agency. The monitoring is used to assess the general state of groundwater quality and groundwater levels / flows in the Republic of Ireland. Thereafter, groundwater monitoring data are used to help determine the status of groundwater in the Republic of Ireland. In turn this information is used to help protect groundwater used for public and private drinking water supplies and is also used to help protect associated surface water and ecological receptors.

The local authorities, academic research institutions, private consultants and the Geological Survey of Ireland are a few of the organisations who also carry out additional groundwater monitoring in the Republic of Ireland. Information on aquifers and the hydrogeology of the Republic of Ireland can be obtained from the Geological Survey of Ireland.

Learn more

Read about the work carried out by the Geological Survey of Ireland
Learn more about the WFD Groundwater Monitoring Programme
Download the Article 5 Characterisation and Risk Assessment Report