The Use of Multiple Techniques for Conceptualisation of Lowland Karst, a case study from County Roscommon, Ireland

Abstract

This paper summarises researchcarried out in county Roscom­mon, Ireland to characterise the workings of low-lying karst, of whichlittle is known. The researchemployed a combination of five main investigative techniques, in conjunction: geomor­phological mapping, spring chemistry and discharge analyses, dye-tracing, microgravity geophysical investigations and bed­rock core drilling. The results enabled the production of a de­tailed conceptual model for the area. Surface and subsurface karst landform mapping revealed a highlevel of karstification. Clustering and alignment of recharge landforms is found to be a significant aspect of the karst. Analyses of spring chemistry and discharge data revealed characteristics of the aquifer sys­tems in operation. It was found that a significant percentage of flow is via enlarged conduits but that the smaller fractures are important for providing base flow. Water tracing experi­ments proved that water moved from highly karstified, el­evated recharge zones to springs at the periphery. Microgravity geophysical investigations, detected and located solutionally enlarged voids in the bedrock and demonstrated the impor­tance of the shallow epikarst system as well as a deeper con­duit network. Bedrock core drilling detailed the nature of the bedrock underneathkarst landforms and showed the successes and failings of the geophysical investigations. Spring catchment boundaries were then delineated using water balance equations and a combination of the information retrieved from the other methods. Using these results in combination large amounts of information were gathered leading to the production of the first conceptual model for the karst of Roscommon, whichcan be adapted and applied to IrishLowlands in general. The use of multiple, complimentary, investigative techniques in conjunc­tion greatly enhanced the accuracy and success of this project. The aim of this paper, therefore is to highlight the benefits of using many analytical techniques together.