Interdisciplinary studies for the knowledge of the groundwater fluoride contamination in the eastern African rift: Meru district - North Tanzania

This research was aimed at finding fresh and safe groundwater easily deliverable to an area, located in Northern Tanzania. The study area suffers water shortage, due to widespread alkaline volcanism, high fluoride contents (F- up to 70 mg/l) affects the groundwater. The achievement of this goal has been pursued through a multidisciplinary approach research. The study area stretches over 440 km2 and lies in the northern part of the Arumeru District. Climate is semi-arid, with dry and relatively rainy seasonal alternance. Four principal hydrogeological complexes have been identified within different lithologies. They occur within volcanic formations, singularly or superimposed each other. Subordinate perched aquifers are present in sedimentary formations with local occurrence. The groundwater flow system has been interpreted on the base of springs spatial distribution joined with lithological and geometrical reconstruction of the aquifers. The dominant pattern consisting of multidirectional flow from the higher elevation area in the south, towards the lower area in the north is complicated by the occurrence of structures such as graben, faults, lava dome and tholoids. After the identification of the main fluoride source, an interference pattern among groundwater and high F surface water was drown. Finally, an aquifer to be individuated within a structural high where the fluoride input is prevented and in which a well was drilled, able to supply at least 3.8 l/s of low fluoride.