Water monitoring stations used by the EPA and Local Authorities are registered on EDEN Monitoring Data System by an application called the Feature Coding Tool (FCT). This tool applies a unique code to river, lake, transitional, coastal or groundwater stations registered on it.
https://data.gov.ie/dataset/water-monitoring-stations?package_type=dataset
https://gis.epa.ie/geonetwork/srv/eng/catalog.search#/metadata/e3c1266f-3cf4-4c8f-8c23-c90b5b9f6e9f