ASSESSMENT OF THE STREAM NETWORK POLLUTION IN THE E？IRDIR LAKE BASIN (TURKEY) USING WATER QUALITY INDEX AND MULTIVARIATE ANALYSIS

E？irdir Lake which is one of the sources of the drinking water of Isparta (Turkey) is the second largest fresh water lake of Turkey. The most important surface waters in the study area are Pupa, Hoyran, Yalva？ and ？ay Streams. Pollutants from point and nonpoint sources are transported into the lake via these four main streams. In this study, stream water quality, seasonal variations and its suitability for drinking usage were evaluated. Parameters which are controlled to chemical variations of stream water, were analyzed with R-mode factor and correlation analysis. According to R-mode factor analysis, EC, NO3, NO2, NH3, BOD, COD in dry season and K, HCO3, Cl, NH3, NH4, orthophosphate, total phosphorus, BOD, COD in wet season are the most important parameters. In addition, Water Quality Index (WQI) was applied to suitability for drinking purpose and evaluation of stream water quality. According to the WQI in dry season, 46.66% of stream water samples exhibited ‘‘good water’’, 20% exhibited ‘‘poor water’’, and 33.33% exhibited “very poor water”. In wet season 46.66% of stream water samples exhibited ‘‘excellent water’’, 13.33% exhibited ‘‘good water’’, 26.66% indicated ‘‘poor water’’ and 13.33% showed “very poor water”