Estimation of groundwater recharge in a major sand and gravel aquifer in Ireland using multiple approachesApproches multiples pour l’estimation de la recharge d’un aquifère de sable et gravier en IrelandEstimación de la recarga de agua subterránea en un acuífero de arena y grava en Irlanda utilizando múltiples criterios应用多种方法估算爱尔兰某主要砂砾含水层的地下水补给Estimação da recarga subterrânea num importante aquífero de areias e cascalho na Irlanda, usando diversas metodologias

Groundwater recharge was investigated in the most extensive sand and gravel aquifer (area of approximately 200 km2) in the Republic of Ireland as part of a wider study seeking to derive recharge estimates using aquifer vulnerability mapping. The proportion of effective rainfall (total rainfall minus actual evapotranspiration) that leads to recharge is known as the recharge coefficient. The recharge investigation involved a variety of approaches, including soil moisture budgeting, well hydrograph analysis, numerical modelling and a catchment water balance. The adoption of multiple techniques provided insights on recharge and also on aquifer properties. Comparison of two soil moisture budgeting approaches (FAO Penman-Monteith with Penman-Grindley) showed how variations in the effective rainfall values from these methods influence groundwater levels simulated in a numerical groundwater model. The catchment water balance estimated the recharge coefficient to be between 81 and 85%, which is considered a reasonable range for this aquifer, where overland flow is rarely observed. The well hydrograph analysis, using a previous estimate of specific yield (0.13), gave recharge coefficients in the range of 40–80%, considered low for this aquifer: a revised specific yield of 0.19 resulted in a more reasonable range of recharge coefficients of between 70 and 100%.