Abstract
An evaluation of the suitability of surface water for different uses from the mainstream running through Riyadh, Saudi Arabia, was conducted using three indices namely: water quality index (WQI), percentage of sodium (%Na) and Nemerow’s pollution index (NPI). The water samples were collected on monthly basis from June 2009 to March 2010 from 10 sites. The WQI was calculated based on different water standards for different uses. Excellent water has WQI value of 50–100, where WQI is calculated based on 29 parameters. The permissible range of %Na in water used for irrigation purpose should be between 40% and 60%. On the other hand, if 0<NPI<1.0, then the water is regarded as being in a good condition. In this study, WQI ranged from 34 to 513 with an average of 282, thereby indicating mild pollution at some sites. The %Na value ranged between 19 and 66, with an average value of 46 indicating that the water is suitable for irrigation at most of the sites. The NPI ranged between 1 and 11 with an average value of 5, which indicates that water in most of the sites is in a good condition. It is recommended that surface water from these sites should not be used for human activities. The formulas used to calculate the water quality indices are easy to use thus providing a valuable tool for the accurate monitoring of water pollution.