A contribution to the knowledge of Fårö’s hydrogeology

Abstract: Fårö, Sweden´s ninth largest island, is suffering from poor groundwater management. A rampant development within tourism on Fårö to uphold its socioeconomic status has led to insufficient water quality and quantity in the municipal water supply. In order to support the progress of Fårö´s water supply, a contribution to the know-ledge of its hydrogeology is presented. Recent evolution in airborne geophysics has culminated in SkyTEM, a helicopter electromagnetic system speci-fically developed for hydrogeological surveys. For the first time after an initial pilot study, the SkyTEM system is used on a large scale in Sweden. Four areas on Gotland were investigated by the Geological Survey of Sweden, SGU, and one of these areas was Fårö. By combining data collected with SkyTEM with previously collected data and also newly acquired field measurements, new light has been shed upon Fårö´s hydrogeology. The results reveal promising potential and two previously unexploited areas on Fårö have been highlighted to have favorable hyd-rogeological conditions. Both areas are currently used only for private water supply and have sizes of 2 and 20 km2 respectively. Additionally, the boundary between fresh and saline groundwater is discussed and an updated inter-pretation following the work of Tullström (1954) is presented.