The quality of shallow groundwaters in Northern Ireland

Northern Ireland has a diverse range of rock types and lithologies which create small hydrogeological units, each with its own characteristics. The restricted geometry of these units permits only short and shallow groundwater flowpaths to develop, most with at least partial access to atmospheric oxygen. Each hydrogeological unit has a distinctive distribution of mineralization and major ions. In general, groundwater chemistry is stable with time, except for a few areas of intense agricultural activity where trends in nitrate nitrogen concentration are apparent. The relatively high rainfall in Northern Ireland dilutes surplus nutrients which, combined with year-round moist soils with an active bacterial population, ensures that nitrate nitrogen concentrations are generally low.