Datasets of hydro energy potential are downloadable as GIS shapefiles. Two spatial reference systems are applied to the downloadable shapefiles: Irish Transverse Mercator (ITM) and WGS 84 (EPSG:3857).

A 1985 study provided the raw data and technical terms in its glossary (link). Important terms are:
Head: The level difference between the water surface at intake and trailrace of a turbine.
Tailrace: The discharge channel from a turbine or waterwheel before rejoining the main river channel.

The Sustainable Energy Authority of Ireland (SEAI) offers the same data in its Hydro Mapping System, a digital map of Ireland's hydro energy connections and potential resources (http://gis.seai.ie/hydro).

References

Small-scale Hydro-electric Potential of Ireland, Department of Energy, 1985.
https://seaiopendata.blob.core.windows.net/hydro/DOE_1985_Small%20Scale%20Hydro-Electric%20Potential%20of%20Ireland.pdf