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The purpose of the study was to assess the water quality parameters of Elala River found in Mekelle, Tigray, Ethiopia. Four sampling sites were chosen spatially along the water course to reflect a consideration of all possible activities that are capable of affecting the quality of the river water. The water samples were collected monthly for three consecutive months (March to May, 2014) at the four sampling sites. In order to understand the characteristics of Elala River, principal component analysis (PCA) was utilized using 22 water quality parameters: water temperature, electrical conductivity, turbidity, pH, total solids, total suspended solids, total dissolved solids, total alkalinity, total hardness, calcium, magnesium, chloride, sulfate, nitratenitrogen, nitrite-nitrogen, ammonium-nitrogen, total nitrogen, dissolved oxygen, biological oxygen demand, chemical oxygen demand, orthophosphate and total phosphorus. Among the 22 studied water quality parameters: electrical conductivity (904.11 to 2156.11 μS/cm), turbidity (21.07 to 34.99 NTU), total dissolved solids (700.22 to 1328.22 mg/L), total alkalinity (131.85 to 267.26 mg/L), total hardness (198.67 to 478.67 mg/L), chloride (47.32 to 259.43 mg/L), calcium (65.13 to 146.99 mg/L), chemical oxygen demand (16.02 to 32.53 mg/L), sulphate (271.82 to 384.07 mg/L), nitrate-nitrogen (6.82 to 62.38 mg/L), orthophosphate (0.03 to 0.14 mg/L) and total phosphorus (0.04 to 0.19 mg/L) were above the prescribed limit of WHO guidelines for drinking purposes, while all analyzed water quality parameters fall within the FAO standard limit for irrigation purposes. The water is thus not potable for domestic purposes without some forms of physical and chemical treatment while it is useful for agricultural purposes.

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ABSTRACT. Water pollution with heavy metals due to discharge of untreated domestic wastes and surface runoff to the rivers is a major threat for human health that consumes vegetables grown with the polluted river. The present study aimed to examine the contamination of heavy metals through the health risk assessment via the consumption of spinach vegetable grown by the irrigation of Elalla River. Water from Elalla River, soil and spinach were analyzed for Fe, Zn, Cu, Pb, Cr and Cd using FAAS. Based on the elements analyzed, TF, DIM and HRI were calculated. The elements Cr (0.18-0.60) and Cd (0.021-0.023) in water samples (mg/L), Zn (316.10-517.86) and Cd (16.00-16.80) in soil samples(mg/kg); and Fe (483.38-612.24), Zn (109.86-219.72), Pb (2.56-3.97), ) and Cd (1.62-1.91) in spinach (mg/kg) were exceeded the permissible limits set by FAO and Ewers and Weigert. The TF calculated were lower for all metals except for Pb (2.832). Although the HRI values of all studied heavy metals were found to be < 1, the values for Cd and Pb were higher indicating alarming condition for the long term use of spinach in the studied area. Therefore, regular monitoring of heavy metals is essential to prevent excessive build up in the food chain and prevent serious health risk of population.