Abstract
Arusha aquifers have been exploited intensively serving as the main source of domestic water supply in the city. But the quality of groundwater is not clearly documented for future planning and management. Hydrogeochemical assessment was carried out to establish groundwater quality and its spatial distribution with the aid of geostatistical techniques. Groundwater samples were collected and analyzed for major cations and anions using conventional methods of water analysis. Well lithology and geological map were considered for hydrogeological interpretation of the area. The results of piper diagram revealed Na–K–HCO3 water type with sodium and bicarbonate ions dominating in all samples. High fluoride concentrations and general groundwater chemistry are mainly controlled by aquifer lithology than anthropogenic activities. The levels of anthropogenic pollution indicators such as nitrate, chloride and sulfate in deep wells are generally low and most likely coming from natural sources. The geological sections indicate two potential aquifers (volcanic sediment and weathered/fractured formation) both yield water containing significant concentration of fluoride. Fluoride concentrations were higher than WHO guidelines (1.5 mg/l) and Tanzanian standards (4.0 mg/l) by 82 and 36% of the analyzed groundwater samples, respectively. The southern part of the study area yields groundwater of better quality for human consumption than northern zones which is at high elevation on the foot of Mt. Meru. With exception of fluoride, the quality of groundwater in the study area is generally suitable for drinking purpose and other socioeconomic uses.
Highlights
Water is the most important natural resource for continued existence of any community or ecosystem (Gleeson et al 2016; Jha et al 2007; Kløve et al 2014)
This study focused on geostatistical methods for establishing groundwater quality spatial distribution in the study area
The hydrogeochemical assessment results and distribution of groundwater major cations (Na+, Ca2+, K+, Mg2+) and anions (HCO3−, Cl−, SO42−, F−) in the study area indicate that groundwater chemistry is mainly influenced by aquifer lithology than anthropogenic activities
Summary
Water is the most important natural resource for continued existence of any community or ecosystem (Gleeson et al 2016; Jha et al 2007; Kløve et al 2014). The quality of groundwater is mainly governed by local geology and highly influenced by environmental factors (Fitts 2002). Factors such as rainfall, temperature and pH conditions facilitate different subsurface physical chemical processes such as weathering, dissolution and ion exchange (Gizaw 1996). Temperature and pH conditions facilitate different subsurface physical chemical processes such as weathering, dissolution and ion exchange (Gizaw 1996) Under ideal conditions, these processes are the ones that determine groundwater chemistry and its quality as it moves across different geological formations (Kump et al 2000; Olobaniyi and Owoyemi 2006). Apart from natural and anthropogenic pollution sources, overabstraction has been reported worldwide as a threat to both groundwater quality and quantity
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