The Influence Of Hydrogeological Setting On Nitrate Fate And Transport In Irish And British Aquifers And The Implications For Catchment Management

Excess nitrate (NO3) in groundwater is a significant problem in both Ireland and Britain. This paper presents findings from an Irish study and a British study which both investigate fate and transport of nitrate in groundwater.The British study, carried out for a water company, quantified the sources and investigated the transport of nitrate in three catchments in rural and semi-urban settings underlain by chalk or sandstone bedrock. The Irish study investigated the influence of hydrogeological setting on nitrate fate in agricultural catchments underlain by bedrock aquifers with contrasting hydrogeological properties.Both the British and Irish studies highlighted the importance of considering the hydrogeological setting for groundwater quality monitoring and the implementation of contamination mitigation measures. The study in the British catchments highlighted the dominance of agricultural sources of nitrate in both rural and semi-urban settings, the signficiant lag time for nitrate to reach the abstraction points once applied to the surface, and the implications this has on catchment management interventions. Investigations in the Irish catchments showed that in karstified aquifers nitrate management strategies should focus on the deep groundwater pathways, whereas in catchments underlain by lower permeability aquifers, the focus should be on shallower pathways. Significantly, the study also showed enitrification is occuring in the lower permeability bedrock aquifer. Incorporating these considerations when developing catchment management plans can assist in addressing the impact of agricultural practices on the groundwater quality, reduce long-term costs associated with water treatment and contribute towards achieving the aims of the WaterFramework Directive.