Improving water quality assessment and supply

Over 90 per cent of avaiable freshwater in the Arusha region of Northern Tanzania is abstracted from groundwater aquifers. The majority of this is from regolithhosted or alluvial hosted groundwater aquifers situated within 30 m of the surface. Historically this weathered mantle was assumed to protect groundwater from contamination and it is only recently that water quality has been monitored (Coster, 1950; Wateraid, 1991). It has been demonstrated that the biogeochemical processes influencing water quality are complex (Lahermo et al., 1991; Mjengera, 1991; Smith et al., 1996; Bowell et al., 1996). The aim of this paper is to describe the relationships between water chemistry and microbiological activity in protolith (collected below 30m, hosted by unweathered bedrock), regolith (above 30m, water hosted in the weathered rocks and soils) and alluvial hosted groundwaters in urban (Arusha district) and rural areas (Hanang, Mbulu and Babati districts) of the Arusha region, Tanzania. An assessment is made of possible advantages and disadvantages in utilising the various groundwaters as supplies of potable water and in potential treatment options.