Group Water Schemes (GWSs) are community-run water supply schemes. About 70% of GWSs take their water from a privately-sourced supply. The rest take their water from an Irish Water connection (DHPLG, 2017). 81% of the privately-sourced supplies affiliated to the National Federation of Group Water Schemes (NFGWS) take groundwater from boreholes, springs and dug wells. This is around 54% by volume (NFGWS, 2018).

The NFGWS is the representative for community-owned rural water services in Ireland. The NFGWS assists schemes in meeting the challenges of water quality legislation and promotes a ‘multi-barrier approach’ to source protection. The ‘multi-barrier approach’ includes delineation of the Zone of Contribution to a supply source.

A Zone of Contribution (ZOC) is the land area that contributes water to a well or spring (Misstear et al., 2006). It can be considered as the ‘catchment’ to the supply source. Like surface water bodies, springs have natural catchment areas, whereas catchment areas to boreholes depend on a number of hydrogeological and meteorological factors plus the abstraction rate. A ZOC accounts for the ‘horizontal’ movement of groundwater and any entrained contamination once it has reached the water table and is moving towards the abstraction point.

The aim of delineating ZOCs is to define the area that contributes water to an abstraction point. Knowledge of where the water is coming from is critical when trying to interpret water quality data at the groundwater source. The ZOC also provides an area in which to focus further investigation and is an area where protective measures can be introduced to maintain or improve the quality of groundwater.

Different methods can be used to map the ZOC to a spring, borehole or dug well, resulting in different degrees of confidence associated with the boundaries of the de-lineated area. The ZOCs and accompanying reports should be considered as preliminary source protection studies. The work was undertaken by consultants under supervision and review by GSI, and represents a partnership between the GWSs, the NFGWS and GSI. The work was funded through the Rural Water Programme funding initiative of grants towards specific source protection works on GWSs (DECLG Circular L5/13 and Explanatory Memorandum).

The ZOCs were delineated in the period 2011 to 2019. The maps produced are based largely on the readily available information in the area, a field walkover survey, and on mapping techniques which use inferences and judgements based on experience at other sites. As such, the maps cannot claim to be definitively accurate across the whole area covered and should not be used as the sole basis for site-specific decisions, which will usually require the collection of additional site-specific data.

This map shows the location of ZOCs which have been mapped around GWS supplies of groundwater in Ireland.

This map is to the scale 1:20,000. This means it should be viewed at that scale. When printed at that scale 1cm on the map relates to a distance of 200m.

It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas).

The data is shown as polygons. Each polygon holds information on name, year and consultant.