Groundwater modelling with Modflow 6 to support heat recovery from a shallow urban aquifer

• If we are to achieve targets to reduce greenhouse gas emissions then lowenthalpy ground source heating may provide a secure and low carbon form of space heating. • The measured shallow groundwater temperatures under the City of Cardiff were found to be 2°C warmer than predicted, attributed to the subsurface urban heat island effect. • For geothermal resource mapping and regulation, heat advection and the urban groundwater flow system need to be understood. • Here, we develop a groundwater and recharge model of the shallow aquifer in Cardiff.