Water Quality Assessment Parameters Using Frequency Analysis and Environmental Techniques at the Euphrates River Basin in Al-Nasiriyah, Iraq

The Euphrates river basin that passes through the ThiQar province, has recently been considered for research studies to estimate the probabilities water qualities depending on the main directing factors on the quality variations over the basin. Seven sampling stations were chosen in the Upper Euphrates River system. A set of water samples from three different days was used for the determination of physicochemical parameters. Pearson correlation analysis was second-ordered for water quality parameters. Results indicate that salinity, electrical conductivity, and dissolved solids are highly related. So, SO₄²⁻, Cl⁻, HCO₃⁻, TDS, TH, SAR, EC, Mg²⁺, Ca²⁺, K⁺, and Na⁺ were analyzed at the seven sites. The EASYFIT program was employed to determine the best fit of each parameter to a statistical distribution by test fitting the parameter with nine different kinds of distribution models. The best-fitting distribution was then decided by using the Kolmogorov-Smirnov test. In the following step, parameters were estimated using return periods of 100 years. Based on the results of the analysis, it was shown that Wakeby distribution was the most suitable distribution (in most of the cases) in 69 (Sonmez and Durdu, 2006), as well as GEV (along with Generalized Logistic (GL)) as second-generation distribution (in 69 and 70 by Cigizoglu and Froehlich, 1998) and third-generation distribution, respectively. Return periods were compared between the seven sites by charting, and the slope of the charts for SO₄²⁻ was the greatest as in the cases of SAR and Cl⁻. The work could provide valuable references to explain the spatial heterogeneity of surface water quality, for further studies. It would be interesting to study the variations in water quality over the entire basin on a temporal basis.