The Groundwater Vulnerability map shows land areas across Ireland where groundwater can be easily polluted. It also shows areas where it is well protected by the subsoil layers.

The vulnerability category given to a site or an area is based on how easy it is for water which may contain pollutants to reach the groundwater.

Geologists map and record information on the subsoils above the bedrock. They find out how deep the subsoil is and how permeable it is (how easy water can pass through it).

They use information from quarries, deep pits and from boreholes (a deep narrow round hole drilled in the ground).

Subsoil depth, type and permeability maps are combined to work out the groundwater vulnerability at that location.

Landforms found in the Irish landscape like sinkholes and sinking streams (‘karst’ landforms) are categorised as extremely vulnerable as water can pass straight through.

Where the water table is close to the surface in sand and gravel aquifers, groundwater vulnerability is also extremely vulnerable.

This Groundwater Vulnerability map is to the scale 1:40,000. This means it should be viewed at that scale. When printed at that scale 1cm on the map relates to a distance of 400m.

It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas). The groundwater vulnerability data are shown as polygons. Each polygon holds information on the vulnerability category (X, E, H, M or L), a description explaining this (‘Extreme – rock at or near surface/karst’, ‘Extreme’, ‘High’, ‘Moderate’ or ‘Low’) and a unique id.