Groundwater source protection terminology

Groundwater source protection terminology

​The most widely used terms are described as follows:

Zone of Contribution (ZOC) is the land area that contributes water to the well or spring. It is a simple, intuitive, basic hydrogeological definition that is considered to be the best term for general use.

Catchment is the land area that contributes water to the well or spring. 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.

Capture Zone is a common term present in the literature and is equivalent to the ZOC.

Safeguard Zone is a specific Water Framework Directive term that encompasses the same area as the ZOC.

Source Protection Areas (SPAs): Geological Survey Ireland developed this terminology and the methodology for delineating the areas (DELG, EPA, GSI, 1999). Two Source Protection Areas (SPAs) are delineated which, when combined, are equivalent in area, shape and orientation to the Zone of Contribution:

  • ​Inner Protection Area (SI), designed to give protection from microbial pollution.
                        • Outer Protection Area (SO), encompassing the remainder of the zone of contribution (ZOC).

The ZOC and the SPA account for the 'horizontal' movement of groundwater.  Source Protection Zones are obtained by integrating the Source Protection Areas with the groundwater vulnerability categories. The SPZ includes the complete pathway, both vertical and horizontal, for recharge and any entrained contaminants to the abstraction point. 

It is recommended that for general usage the simplest, most basic hydrogeological term "ZOC" is used.  "SPA" and "SPZ" are appropriate when considering protection of groundwater sources and a sufficiently detailed study has been undertaken in order to delineate the areas and zones. The term "Safeguard zones" is only used with reference to implementation of the WFD. 

Drinking Water Protected Areas are a specific Water Framework Directive term and they encompass the same areas as Groundwater Bodies. 

Groundwater Body is a specific Water Framework Directive term used to subdivide aquifers into effective management units. 

Drinking Water Safety Plan is a risk assessment and risk management approach to ensure the 'safety' and 'security' of a water supply. In this context 'security' refers to the catchment to the supply and 'safety' refers to the quality of the treated water meeting drinking water standards. 

Setback Distances, Exclusion Areas/Zones are specific terms used to regulate the spreading of organic fertilisers and other farmyard activities around drinking water sources. Regulations (S.I. No 31, 2014) provide a range of setback distances from a water source depending on the daily abstraction or the number of people served. The regulations provide for alternate distances and/or zones to be proposed by a local authority or Irish Water subject to EPA approval for abstractions supplying 10m3 or more of water per day, or serving 50 or more persons.