The Use of Water Quality Index Models for the Evaluation of Surface Water Quality: A Case Study for Kirmir Basin, Ankara, Turkey

Water quality is an important factor for health and safety issues associated with public health and also for aquatic life. More and more water quality issues are becoming a significant concern due to the growth of population, urban expansion and development. Thus, assessment of surface water quality has become an important issue. Water Quality Index (WQI) is a single number which can be calculated easily and used for overall description of the quality of water bodies used for different purposes. In this study, the water quality data obtained from 10 sampling stations during one year monitoring period at Kirmir basin was evaluated. Kirmir basin is one of the important drinking water sources of the capital city of Turkey, Ankara. The analyses of 44 water quality parameters were done for all water samples at the General Directorate of State Hydraulic Works (DSI), Department of Chemistry, Water Analysis Laboratory. It was found that DO, BOD, phosphate, color, turbidity, T. coli, E. coli, Enterococci, iron, manganese, arsenic, aluminum, boron, and barium values which exceed the limit values given in the water quality standards are the major pollutants that affect the water quality in this basin. For easy interpretation of the data, five different WQI models were applied for the selected parameters. The suitability of these WQI models is discussed with respect to their applicability in similar studies. For this study it is concluded that the Canadian WQI (CWQI) and Oregon WQI (OWQI) would provide the best results.