干旱区生态环境知识资源中心

Harvested roof rainwater plays a vital role in supplying water in the scarce semi-arid areas. Prior knowledge of rainwater quality helps to understand the relative pollutant contributions of location- and time-associated factors. The present work is aimed to explore source and time factors affecting rainwater quality and associated public health risk in the city of Mekelle, a semi-arid area in Ethiopia. Roof rainwater samples (n=21) were collected from May to August 2014 from residential, commercial, bus station, and industrial areas. The samples were analyzed for major ions, physical parameters, and coliforms. The order of concentrations of major ions was observed to be K+. The average pH of rainwater at these stations was 8.26 and ranging from 6.84 to 10.59, indicating alkaline nature. The observed alkalinity is attributed to the nature of soil and geological formation of the area and a significant influence of the cement factory. No definite trends were found in most of the ionic components at all the locations and time of sampling with p-value>0.05. However, concentrations of physical parameters (total dissolved solids, electrical conductivity, total suspended solids, and turbidity) were statistically significant with time of sampling (p-value<0.01). Bacteriologically, 76% of the samples were positive for total coliforms. Moreover, 19% of the samples were positive for fecal coliform. These signify the importance of appropriate treatment measures before using rainwater for domestic water supply so as to prevent potential adverse health effects.