Evaluation of geochemical and bacteriological groundwater qu ality in line with water demand and supply system: a case of arsi robe district, oromia, Ethiopia

Abstract

For the existence of life, water is indispensible natural resource, which is essential and is a basic human entity. Groundwater is one of the major sources of drinking water all over the world. This work was done in an area called Robe district, with the objective of the evaluation of groundwater quality in line with water demand and supply and its suitability for domestic uses. Groundwater samples were recollected from Eight (8) ground water samples site and chemically analyzed for major physicochemical parameter. Physical and chemical parameters of groundwater were determined. These parameters were used to assess the suitability of groundwater for domestic purpose by comparing with the WHO and Ethiopian standard guideline. Water type of the study area was determined by using Aquachem2012.1modaelsoftware which develops piper diagram. The result of the finding indicated that; all water samples had pH value less than eight which is in WHO standard guide line except in two sample site. The Electric Conductivity of sampled water was below WHO standard guide line value (250 μS /cm).TDS of water was below WHO the guide line value (<500 mg/L) which is fine while Temperature of all sampled water is above WHO guide line value. only two water samples had Iron concentration above WHO guide line value (0.3 mg/L) with maximum concentration of (o.78mg/L) in hand dug well of Abo Ali kebele. Two water samples exhibited high concentration of Manganese above Ethiopian guideline value (0.5 mg/L). The hydrogeological facies of water in the study area is dominated by alkaline earth metals. Generally water type of area is Na-Ca-HCO3 in two kebeles (Ataba Robe and HabeDangasela) and the others are different in water type. All samples were had total coli forms and fecal coli forms beyond WHO guide line and dangerous for domestic use. The result also showed that, water demand and supply of the household is not comparable, in which the demand was greater than the proposed supply. Aquachem and Microsoft excel software was used to analyze and present the groundwater data. In general, to complete this study, it requires five months starting from May, 2017to the end of September.