Glacier hydrology describes water movement around, on, in and under glaciers. It plays an important role for glacier flow and thus ice transport into the sea and the associated sea level rise. It is further relevant for nutrient transport and release into ecosystems, for hydropower, and for drinking water supply in glaciated regions. Glacier related flood events are additionally a frequent geohazard, emphasizing the importance of accurate knowledge of glacier hydrology. This knowledge is, however, very limited due to general inaccessibility of glacial subsurface flows and thus lack of direct observations and technologies that could provide them. The present thesis therefore develops novel technologies, allowing to observe and study water flow inside glacial channels in detail, and applies them on Svalbard glaciers. For this, sensing drifters are proposed and their statistical repeatability tested. The instruments are then used to study water flow over glacier surfaces. Further, a method to reconstruct flow paths from drifter data is proposed and showcased with the example of a channel within a glacier. Additional speleological investigations provide permafrost temperatures under Svalbard glaciers and highlight the importance of meteorological glacier surface conditions for temperature and erosion of the glacier bed.