GSI Public Supply Source Protection Areas

Téama: Science
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Two Source Protection Areas (SPAs) are delineated. The Inner Protection Area (SI), designed to protect against the effects of human activities that might have an immediate effect on the source and, in particular, against microbial pollution. The Outer Protection Area (SO), encompassing the remainder of the zone of contribution (ZOC) to the groundwater abstraction point (e.g. borehole or spring).Not all groundwater-fed public supply sources have SPAs delineated around them. The majority of studies (more than 125) have been undertaken by Geological Survey Ireland as part of County Groundwater Protection Schemes. Environmental Protection Agency carried out more than 40 studies as part of the national groundwater monitoring network characterisation. Further studies have been undertaken by consultancies for Local Authorities and Irish Water.Public Water Supplies (PWSs) are operated by Irish Water, Ireland's national water utility, since 2013. Prior to this, public water supplies were managed by Local Authorities. More than 70% of public supplies take groundwater from boreholes, springs and infiltration galleries. This accounts for approximately 23% by volume (Irish Water, 2018).Different methods can be used to map the entire Zone of Contribution to a spring, borehole or well, resulting in different degrees of confidence associated with the boundaries of the delineated area. To be able to specify the Inner Protection Zone within the entire Zone of Contribution, knowledge or estimates of groundwater travel time within the aquifer are required (e.g. from site-specific hydrogeological parameters or tracer tests).Source Protection Areas have been delineated by GSI and EPA following the ‘GSI method’(e.g., GSI/EPA/IGI Source Protection Zonation course, 2009; Kelly, 2010; DELG/EPA/GSI, 1999). These SPAs were delineated as part of County Groundwater Protection Schemes or as part of the WFD Groundwater Monitoring network characterisation. Other SPAs have been delineated by consultants for Local Authorities/Irish Water. These have not necessarily been peer-reviewed by GSI. The Zone of Contribution and the Source Protection Area account for the ‘horizontal’ movement of groundwater. Source Protection Zones are obtained by integrating the Source Protection Areas with the groundwater vulnerability categories. The Source Protection Zone includes the complete pathway, both vertical and horizontal, for re-charge and any entrained contaminants to the abstraction point.Whereas the objective of delineating ZOCs is to define approximate areas that contribute water to an abstraction point, the objective of SPZs is to geo-scientifically characterise the pathway and receptor elements of risk to groundwater within the ZOC of a given source (Kelly, 2010). EPA prepared an advice note on “Source Protection and Catchment Management to protect Groundwater Supplies” that outlines the key measures and policies in place in Ireland (EPA, 2011).

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