Groundwater chemistry evaluation and a GIS-based approach for determining groundwater potential in Mörbylånga, Sweden

Abstract: Recently, several regions in southern Sweden suffered extremely low groundwater levels following a long-term infrequency in rainfall. In response, irrigation was banned in many of the affected municipalities during 2016–2017, amongst which Mörbylånga municipality was one. Because nearly half of the nation’s drinking water is extracted from groundwater, protecting and managing this vital resource in a sustainable manner is essential. The public sector, spearheaded by the Geological Survey of Sweden (SGU), is now increasing their efforts in the search for additional groundwater resources, as well as in the management of existing ones. The aim of this thesis, which is written in collaboration with SGU, is to evaluate the groundwater quality of Mörbylånga municipality. The evaluation is based on more than 1400 groundwater analyses, sampled from private and municipal wells over the last 8–10 year period. The samples, analyzed for physiochemical and microbiological content, are compared to guideline values elaborated by SGU and the National Food Agency (Livsmedelsverket). In addition, 26 maps were created based on georeferenced data from private wells, showing the spatial distribution of the analyzed parameters. Furthermore, an estimation of the groundwater potential in the municipality was per-formed, using a GIS-based approach. By integrating spatial geodata in a multi-criteria analysis, three additional maps were created, which, together with other material, can be used as a base for future groundwater exploration. Results of the evaluation show, for the studied period, a better groundwater quality in municipal wells, compared to private wells. Significant concentrations of nutrients and microorganisms were detected in private wells, especially in the northern and eastern parts of the municipality. High concentrations of lead were in a few occasions encoun-tered in both municipal and private wells and a cyclical variation in concentrations of sodium, sulfate and calcium in one of the municipal wells could possibly be linked to saltwater intrusion. The source for these observations, and suggested measures, are discussed. Furthermore, the GIS-analyses undertaken in this study reveal an area of ap-proximately 2.5 km2 with higher than average groundwater potential. The area is conveniently located with regards to users and infrastructure. Suggestions for how to proceed the work with the GIS results are discussed as well.