Evaluation of Water Quality of Coastal and Groundwater of the Eastern Black Sea Basin, Turkey, Using Multivariate Statistical Analysis and Water Quality Index

The eastern Black Sea Basin, which receives the most rainfall in Turkey and is rich in water resources, is covered with a dense forest cover. The basin is the most mountainous and elevated part of the Black Sea Region, stretching from the Terme Stream in the east of Samsun to the Georgian border. The basin, with a total area of 24,077 km², provides 8% of Turkey’s potential with an average of 14.90 km³ surface water potential per year. Due to the height of the slope and the impermeable or semi-permeable layer of the subsurface, a significant part of the falling rain passes into the surface runoff. In the basin, where many small streams, large and small, emptied into the Black Sea independently of each other, the sub-basin boundaries were determined as water collection basins limited to the water section lines of these rivers. The data used in this study were measured results of well and spring water samples taken from 150 points by the State Hydraulic Works (DSI). Study data were obtained from the Eastern Black Sea Basin Hydrogeological Study Final Report. Measurements were made seasonally in 2020 and 2021. Measured parameters were electrical conductivity, dissolved oxygen, pH, temperature, salinity, NO₃-N, NO₃, NO₂, NO₂-N NH₄, NH₄-N, total phosphorus, total organic carbon, chloride, sulfate, bicarbonate, carbonate, fluoride, bromide, Ca, Mg, Na, K, cyanide, Cd, Pb, Hg, As, Cu, Zn, Ni, Se, Fe, Mo, Co, Ag, Mn, Sn, Cr. In order to evaluate the results, factor analysis and cluster analysis methods, which are multivariate statistical analysis methods, were used. At the same time, the evaluation was made using the water quality index method. In order to determine groundwater quality, sampling was carried out at 151 water points (92 wells, 59 springs) for four periods; anion-cation, heavy metals, aldehydes, phthalates, polyaromatic hydrocarbons, nitrogen compounds, pesticides, ketones, and phenols were analyzed. According to the chemical analysis results, the dominant cation in all sub-basins is Ca, and the dominant anion is HCO₃. In terms of irrigation water, groundwater is generally in the “low salt, low sodium” water class. As a result of the analysis, the main parameters affecting the basin were determined. The most important parameters and factors affecting the basin were determined by factor analysis. Factors were grouped by cluster analysis. The Canadian Water Quality Index method was used for the calculation of the water quality index. The reason why it is preferred to use this index is that it can be applied to the regulations of the countries. By using the water quality index, the pollution level of water can be evaluated as poor, medium, bad, and very poor quality water. Indices are preferred in the evaluation of water pollution because they are understandable, especially for decision makers in the water field.