Groundwater investigation at Storsudret, Gotland

Sammanfattning: Sweden have faced decreasing groundwater storage with critical low groundwater levels for several years. Gotland is one example with issues of providing freshwater due to the low groundwater levels. These circumstances can be related to impacts caused by early agriculture development, an increased demand of freshwater and climate change. There is a need in this region to increase the groundwater storage to ensure enough freshwater. The aim of the study is to increase freshwater storage. Digital geographical information system (GIS) was chosen as a tool in this study in order to cover large geographical areas.  The study was divided into two parts, with focus to determine hydrological and hydrogeological conditions and to identify suitable areas where groundwater storage could be increased. The first part studied: specific capacity, groundwater storage, groundwater balance and topographic wetness index. The second part locked at four methods to increase freshwater storage: Lakes, controlled drainage, wetland and subsurface dam. The result tells us that lakes have the potential to provide freshwater for the municipal distribution network. The controlled drainage method has the ability reduce the outflow of surface water and to increase the groundwater infiltration. Earlier drained wetland areas was identified which could serve as freshwater storage. Suitable areas for subsurface dams were identified. They could work as a large groundwater storage as a decentralized system with the ability to provide groundwater for wells that are spread out. However the identified areas for each methods needs further investigations in more detail to determine the accuracy of the results.