Geology influence on the water quality upstreams of the Nyumba ya Mungu reservoir

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University of Dar es Salaam
Availability of potable drinking water supply has been a major source of concern in some regions in the northern parts of Tanzania, where excessive fluoride contamination compared to the other parameters investigated in this report has been identified. These include Arusha, Kilimanjaro and Tanga regions. The objective of this research work is to carry out the characterisation of Water quality parameters, which cover both physical and chemical parameters in the Arusha geological formations, and the relationship between the occurrences of these quality parameters and the local geology over which the water courses, streams, springs, lakes, ponds and swamps originate and traverse. However, the occurrence of fluoride has been given a broader analysis since its effects are more devastating than the other substances existing in the region's water system. In this regard, there has been a general review of the background geology of the study area, with the view to noting and identifying the compositions of the rock minerals to establish their weather ability and relative contribution to the water quality process. The respective formation types making up the entire region have demonstrated marked variations in their solubilities. Rock minerals in some formations are more leachable and carried into solution, with a stronger tendency to raise the concentrations of their dissolved species in the water in which they are present and sometimes, building up to an abnormally high or toxic level as in the case of fluoride ladened waters of Arusha that poses tremendous risk to users of such water. The plots of calcium and fluoride activities showed that in some of the formations, the fluoride concentrations in solution are still below the saturated limit, most especially samples obtained from springs, while in others the saturated or equilibrium limits have been exceeded. This is the case around the Momella Lakes group. Other parameters such as sulphate, phosphate, chloride, nitrate, calcium and magnesium have low values in all the springs. However, sulphate, phosphate, nitrate and chloride concentrations have been found to be very high in the lahar formations rising above the W.H.O standards.
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Hydrogeology, Nyumba ya Mungu reservoir, Tanzania
Ekeh, R. V. (1999) Geology influence on the water quality upstreams of the Nyumba ya Mungu reservoir, Masters’ dissertation, University of Dar es Salaam. Available at (