Abstract

A groundwater recharge map has been created for the Republic of Ireland. This provides important baseline information for multiple purposes: aquifer water balance assessments using simple lumped models or distributed numerical groundwater models; assessment of the impact of groundwater abstractions as required under the European Water Framework Directive; and delineation of source protection zones. The groundwater recharge map is derived from existing hydrogeological and meteorological spatial datasets. The main hydrogeological controls on groundwater recharge include the permeability and thickness of superficial deposits (mainly tills in Ireland), the presence of saturated soils, and the ability of the underlying aquifer to accept percolating waters. Combinations of these factors are assessed, and a ‘recharge coefficient’ is established for different hydrogeological scenarios. To produce the groundwater recharge map, the geographic information system layer containing the recharge coefficients is multiplied by the effective rainfall. The recharge map is finally modified to take into account areas where the natural recharge capacity of the underlying aquifer is less than the estimated groundwater recharge potential. Originally drafted in 2005, the present map includes refined recharge coefficient estimates, improved representation of wet soils over gravel aquifers, and a full national coverage of full subsoil permeability and groundwater vulnerability mapping. There are a number of assumptions made in creating the groundwater recharge map (notably, only direct (diffuse) recharge is taken into account) and there are limitations of precision associated with the input datasets. For reasons of scale and generalization to a national coverage, the map is useful for giving regional estimates of recharge but these, in many cases, will need to be refined by site-specific studies.

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