Positive matrix factorization in distinguishing water pollution sources in upper Awash river basin, Ethiopia

Recently, the decline in water quality in the Upper Awash River Basin, Ethiopia, has been exacerbated by increasing industrialization, urbanization and agricultural activities. The aim of this study was to identify the major pollutants and their sources. To achieve the main objectives, the physicochemical qualities of 197 groundwater, 60 surface water (collected from ten different rivers), and 60 drinking water samples were analyzed using standard procedures. Also, sanitary data associated with the different drinking water supply systems were collected. Principal component analysis (PCA) and positive matrix factorization (PMF) modeling were used for data analysis. The present results showed that the most dominant hydrochemical water types were Na-HCO3 (65.0%) and Ca-HCO3 (32.5%) for groundwater, while Na-CO3 (35.0%), Na-HCO3 (13.3%) and Ca-CO3 (11.7%) were observed within the surface water. The results from sanitary assessment indicated that the drinking water supply systems were exposed to contamination with 66.7% from animal grazing, 61.7% from agricultural farming, and 40.0% from domestic waste. About 64% of surface water pollutants came from natural geological sources, with 29% from agriculture and 7% from other human activities. For groundwater, the contaminants were 63% from geological structure, 17% from agriculture, and 20% from other anthropogenic sources. Since agricultural and other anthropogenic activities contributed significantly toward water pollution in the study area, it needs to be addressed through appropriate domestic waste disposal and fertilizer management systems such as applying fertilizers in precise amounts to reduce runoff and leaching as well as establish vegetated buffer zones near water bodies to absorb excess nutrients.