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Bedrock Aquifers

An aquifer is an underground body of water-bearing rock or unconsolidated materials (gravel or sand) from which groundwater can be extracted in useful amounts.

GSI’s Aquifer classes are divided into three main groups based on their resource potential, and further subdivided based on the type of openings through which groundwater flows. There are nine aquifer categories in total. In the Groundwater Protection Schemes (GWPSs), these are also referred to as ‘Resource Protection Zones’.


1) Regionally Important Aquifers:

Regionally important aquifers are capable of supplying regionally important abstractions (e.g. large public water supplies), or ‘excellent’ yields (>400 m3/d). Bedrock aquifer units generally have a continuous area of >25 km2 and groundwater predominantly flows through fractures, fissures, joints or conduits. Regionally important sand/gravel aquifers are >10 km2, and groundwater flows between the sand and gravel grains.

This group is subdivided into the following types:

•Rk Regionally Important Karstified Bedrock Aquifer
•Rf Regionally Important Fissured Bedrock Aquifer
•Rg Regionally Important Sand/Gravel Aquifer

Regionally important karstified aquifers may be further subdivided based on the whether groundwater flows mainly through conduits (Rkc) or more diffusely through solutionally-enlarged fissures (Rkd).

2) Locally Important Aquifers:

Locally important aquifers are capable of supplying locally important abstractions (e.g. smaller public water supplies, group schemes), or ‘good’ yields (100-400 m3/d). In the bedrock aquifers, groundwater predominantly flows through fractures, fissures, joints or conduits. Locally important sand/gravel aquifers are typically >1 km2, and groundwater flows between the sand and gravel grains.

This group is subdivided into the following types:

•Lm Locally Important Bedrock Aquifer, Generally Moderately Productive
•Ll Locally Important Bedrock Aquifer, Moderately Productive only in Local Zones
•Lk Locally Important Karstified Bedrock Aquifer
•Lg Locally Important Sand/Gravel Aquifer


3) Poor Aquifers:

These bedrock aquifers are capable of supplying small abstractions (e.g. domestic supplies, small group schemes), or ‘moderate’ to ‘low’ yields (<100 m3/d). Groundwater predominantly flows through a limited and poorly-connected network of fractures, fissures and joints.

This group is subdivided into the following types:

•Pl Poor Bedrock Aquifer, Generally Unproductive except in Local Zones
•Pu Poor Bedrock Aquifer, Generally Unproductive

Geological Survey of Ireland

2015-06-23 12:53:57

Geological Survey of Ireland

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