Abstract
One hundred and eighty drinking water samples were collected from five zones of Riyadh governorate including Riyadh main zone, Ulia, Nassim, Shifa, and Badiah zones. The water was collected from the main water network and underground and upper household tanks in each zone. The water quality was found to be acceptable for drinking with respect to chemical characteristics; however, analyses exhibited some microbial contamination. The water quality index (WQI) is a mathematical method used to facilitate water quality explanation. The WQI was calculated using several physico-chemical and microbial parameters. The results showed that more than 88% of Riyadh main zone, 91% of Ulia, 97% of Nassim, 88% of Shifa, and 100% of Badiah waters zones were considered excellent for drinking (class I). The remaining waters were considered unsuitable for drinking (class V) due to microbial contamination.