Fabian's paper on the thermal use of groundwater provides a method to quantitativley and spatially assess the potential of the ressource. The procedure can be adapted to local regulatory and operational limits, thus estimating legally and technically achievable flow rates and subsequently, the thermal power that can be exchanged with the aquifer through a well doublet. Thus, the technical potential, e.g. for groundwater heat pumps, can be integrated in urban energy planning for the first time.