Assessment of water quality parameters and eutrophication potential in the Berdan river system (Mersin-Tarsus)

Studies on the water quality in rivers are of critical importance for the monitoring and controlling water pollution, as well as taking measures to address the sources of pollution. Considering the significance of rivers for aquatic organisms in the ecosystems, they flow through and the decreasing availability of usable water resources, continuous monitoring and implementation of measures to protect the water quality of freshwater sources like rivers are of great importance. In this regard, this study was conducted on the Berdan River, which is one of the important rivers in Mersin province, between September 2021 and August 2022. The measured water quality parameters were as follows: Temperature (T) ranged from 9.80 to 30.20 °C, Salinity (S) ranged from 0.20 to 0.80 ppt, pH ranged from 7.13 to 9.48, Electrical Conductivity (EC) ranged from 364.00 to 1602.00 µS/cm, Dissolved Oxygen (DO) ranged from 5.91 to 13.11 mg/L, Dissolved Oxygen Saturation (DO % sat.) ranged from 69.96 to 171.54%, Chlorophyll-a (Chl-a) ranged from 5.12 to 159.12 µg/L, Nitrate (NO3-N) ranged from 0.27 to 14.66 mg/L, Orto-Phosphate (o-PO4-P) ranged from 0.03 to 1.70 mg/L, Total Nitrogen (TN) ranged from 0.70 to 18.10 mg/L, and Total Phosphorus (TP) ranged from 0.04 to 1.71 mg/L. According to the Surface Water Quality Regulation (YSKY), pH, DO, and NO3-N values exhibited Class I quality and EC displayed Class II quality at all stations. While TN showed Class I quality at Station 1 and Station 2, it showed Class II quality at Station 3. On the other hand, o-PO4-P and TP showed Class II quality at Station 1 and Station 2, and Class III quality at Station 3, respectively. According to trophic status assessment, all stations were eutrophic based on TN and TP levels. Station 2 was classified as mesotrophic based on the Chl-a parameter while Station 1 and Station 3 exhibited eutrophic water quality characteristics. All stations were classified as eutrophic according to the TRIX index. Based on the results, the Berdan River displayed eutrophic water quality characteristics, and it is clearly evident from YSKY and trophic classification that this was due to phosphate sources. The main sources of pollution in the Berdan River Basin include urban wastewater extending along the basin, solid waste leakage, industrial wastewater discharges as well as agricultural and livestock activities.