A GIS and remote sensing based screening tool for assessing the potential for groundwater discharge to lakes in Ireland

Abstract

Groundwater discharge is a major pathway for the delivery of freshwater and nutrients to surface water bodies. In recognition of the significance of groundwater as a potential pollution pathway and the challenges of localising and assessing inputs that are diffuse and highly variable, robust and effective GIS and remote sensing methodologies to facilitate national and water-body-scale assessments of the potential for groundwater discharge are presented. Firstly, lake water bodies were classified according to ‘likelihood’ to receive groundwater discharge, defined within a GIS relative to a number of simple criteria including underlying aquifer type and presence of geologic faults, springs and other karst features. The approach facilitated a time- and cost-effective screening of over 800 lakes, which was completed to prioritise subsequent analyses of potential groundwater— lake interactions using remotely sensed imagery. Surface water temperature and temperature anomaly maps generated using satellite imagery revealed thermal signals potentially indicative of groundwater—lake interactions. Furthermore, the results showed that larger (more negative) thermal anomaly values were associated with the higher likelihood classes. This research helps to set the foundation from which key knowledge gaps on the interaction between groundwater and lakes in Ireland can begin to be addressed.