Groundwater

Outdoor Water Pump

Photograph of a a girl at an outside water pump

Outdoor Water Pump

Outdoor Water Pump

Photograph of a a girl at an outside water pump

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Some of the rain that falls on Ireland filters through the soil, subsoil and rocks and becomes groundwater.  Much of that water moves slowly underground and remains there for long periods before emerging as base flow in rivers or as springs. Some is extracted for drinking, particularly for single houses in the country, and often receives little or no treatment prior to use.

Groundwater is protected against pollution from the surface if there is sufficient depth of overlying soil and subsoil but, if that depth of cover is small, then groundwater is vulnerable from septic tank effluent and from slurry spreading.  Much of the underlying rock in Ireland is limestone that is easily dissolved by water and this has created cracks and fissures in the rock that allows pollutants from the surface to move quickly down to the underlying water body.  Hence much of Ireland’s groundwater resources are vulnerable to pollution.

The pollutants of most concern to groundwater in Ireland are Nitrates from fertiliser use on land and microbial contamination from septic tanks and slurry spreading.  Septic tank systems are used extensively for sewage treatment in the rural areas of the country and, while the tank itself separates out gross solid material, the real treatment occurs in the soil and subsoil of the percolation area downstream of the tank.  Almost all animal manures are recovered as fertiliser on farm land and this material has the potential to be highly polluting with a very high microbial count.

Microbial Contamination

Faecal Coliforms in groundwater
Courtesy EPA

Chemical Contamination

Nitrates concentrations in groundwater
Courtesy EPA