Pollution evaluation in streams using water quality indices: A case study from Turkeyʹs Sapanca Lake Basin

The stream water quality in Sapanca Lake Basin (Turkey) was investigated in terms of Canadian Council of Ministers of the Environment Water Quality Index (CCME – WQI), Oregon Water Quality Index (OWQI) and National Sanitation Foundation Water Quality Index (NSF – WQI). The main reason is to see the current pollution status in streams and also to compare leading three international water quality indices using domestic data. Also, a modified model that is adopted particularly from National Sanitation Foundation Water Quality Index (NSF-WQI) was prepared. Modified WQI incorporates the impact of temperature, pH, electrical conductivity, dissolved oxygen, total dissolved solids, total suspended solids, calcium (Ca), magnesium (Mg), chloride (Cl), sulfate (SO4), orthophosphate-phosphorus (o-PO4-P), nitrate (NO3-N), nitrite (NO2-N), 5-day biological oxygen demand (BOD5), and the formation of chemical oxygen demand (COD). Developing modified indices in order to get sufficient results using limited amount of parameters is particularly useful for conserving the money required to measure huge number of parameters. Hence the aim of this research is to decrease the number of pollution parameters. For this aim, WQImin (minimum)—which take into account temperature, pH, dissolved oxygen (DO), total suspended solid (TSS), and electrical conductivity (EC)—was generated. The same methodology was repeated using eutrophication parameters. An alternative index, named WQIeut (eutrophication), was developed using DO, o-PO4-P, NO3-N, NO2-N, BOD5, and COD parameters. A good relationship was found between the developed indices and fifteen-parameter WQI. Finally, the research uncovered a threat of eutrophication for Sapanca Lake and streams feeding it.