This map layer shows the classification of bedrock, as mapped at 1:250 000 scale, into aquifer categories. This classification was initially undertaken to support groundwater assessments undertaken for the Water Framework Directive (2000/60/EC). The classification was produced on behalf of Northern Ireland Environment Agency (NIEA) (DoE, Northern Ireland) and is the standard classification currently used for assessing activities which may impact on groundwater resources.
The classification comprises six categories of bedrock aquifer, based upon relative resource productivity and flow type.
| Aquifer category | Symbol | Description |
| Bedrock | ||
| High potential productivity fracture flow |
Bh (f) | High to moderate yields probable, however dependence on fracture flow makes poorer yields possible. Generally includes element of regional flow (kms). |
| High potential productivity fracture/intergranular flow |
Bh (l-f) | High to moderate yields probable, however part dependence on fracture flow makes poorer yields possible. Dual porosity. Generally includes element of regional flow. |
| High potential productivity fracture flow with karstic element |
Bh (f-k) | High to moderate yields probable, however dependence on fracture flow makes poorer yields possible. Evidence of karstic flow. Generally includes element of regional flow. |
| Moderate potential productivity fracture flow |
Bm (f) | High to moderate yields possible in places however dependence on fracture flow makes poorer yields possible. Potential element of regional flow, but local flow significant. |
| Limited potential productivity fracture flow |
Bl (f) | Moderate yields unusual. Low yields more common. Regional flow limited. Mainly shallow, local flow. |
| Poor potential productivity fracture flow | Bp (f) | Small supplies may be possible but strata rarely exploited. Negligible regional flow. Limited local flow |
Table 1 Bedrock aquifer classification categories and overview description
The classification is intended to represent general regional differences in resource potential and dominant groundwater flow mechanisms in bedrock units as mapped at 1:250 000 scale across Northern Ireland. The classification is not intended to identify, for bedrock at a specific site location, what the aquifer properties are or what the yield will be in a borehole drilled into the bedrock strata at that location. Due to natural geological variability and data availability, this map cannot and is not intended to represent actual conditions on a site-specific scale. For site specific investigations more detailed geological and hydrogeological information is available from GSNI.
A more detailed description of the aquifer classification methodology can be found in McConvey P J 2005. Water Framework Directive – An aquifer classification scheme for Northern Ireland, Geological Survey of Northern Ireland, Belfast. Commissioned Report – pdf document.
Advice on groundwater management and protection matters is available from the GSNI hydrogeologist or by contacting the Groundwater Team at NIEA.
Further information on the hydrogeology of Northern Ireland is available in Hydrogeology of Northern Ireland, Robins N S (1997) and Hydrogeological Map of Northern Ireland, BGS 1994 – both available from the BGS bookshop or from the GSNI office (note: the aquifer classification used on the 1994 hydrogeological published map differs from the classification shown on the GeoIndex layer).
NOTE: When considering the distribution of aquifers within a certain area, reference should also be made to the superficials ‘aquifer’ layer, available on this website.