Groundwater Ecology Ireland
Importance of groundwater
The pictured stream (Burren, Co. Clare) is summer-dry, because the groundwater table is too low for maintaining sufficient streamflow in low rainfall periods.
Groundwater is that part of rain, snow and mist that infiltrates through the soil and rock to the water table.
The unsaturated soil and rock material above the water table contains air and water in the spaces between its particles and supports vegetation.
In the saturated zone below the water table, ground water fills in the spaces between particles and within bedrock fractures. And makes up a large part of the freshwater resources on this planet.
The space occupied by groundwater is not only vast, but also of a very heterogeneous nature, because it has been shaped by the continents’ long geological history.
This is especially relevant for Ireland with its eventful geological past. Groundwater supplies 20-25% of Ireland’s drinking water, with large variations between different counties. Often groundwater does not require big efforts in purification, because filtering happens naturally in soils and rocks, which it passes through. Therefore unlike water from lakes or streams groundwater usually does not contain a lot of algae or pathogenic microbes.
Hence groundwater is considered to be a cheap and reliable resource. It is however only safe, as long as we protect it well enough to stay clean. When pollution from sewage or animal waste does enter groundwater, many people, who use it as drinking water, do indeed get sick. One cause is a resilient pathogenic microbe called cryptosporidium, which causes diarrhoea. In Ireland such cases have made a lot of headlines in recent years.