Sustainable water resources and sustainable energy supply are two of the main challenges we face in today’s society. Shallow groundwater temperatures play a crucial role in both of these areas, especially within densely populated regions. Still, there is a lack in understanding the influence modern humanity has on the thermal regime of the shallow subsurface. Human activity directly influences ambient air, surface and groundwater temperatures. The most prominent phenomenon is the urban heat island effect, which has been investigated particularly in large and densely populated cities. Urban heat islands in the subsurface contain large quantities of energy in the form of elevated groundwater temperatures caused by anthropogenic heat fluxes into the subsurface. One of the main heat sources are elevated ground surface temperatures - urban heat islands at surface and subsurface are coupled through conductive heat transport. However, the link between them is not yet sufficiently understood.

Here I will present an overview of my PhD thesis, which combines above and below ground temperatures to better understand the human impact on the thermal regime of the shallow subsurface.