In this study, the seasonal variation on drainage water quality of Çarşamba Plain, Turkey has been evaluated from June 2012 to January 2013 and determined the suitability of water for irrigation purpose. Water samples collected from 21 drainage canals during July and January were analysed for 12 water quality parameters including physico-chemical analyses. Piper diagram and United States Salinity Laboratory (USSL) diagram were prepared to investigate water quality. Sodium Adsorption Ratio (SAR), Percent Sodium (Na%), Residual Sodium Carbonate (RSC), Kelly Index (KI), Magnesium Ratio (MR), Langelier Saturation Index (LSI), Permeability Index (PI) and Potential Salinity (PS) were also used to assess suitability of waters for irrigation.
In July 2012, EC values varied between 0.45-4.23 dS/m. Waters of 7 drainage canals were found to be unsuitable for irrigation with regard to KI, 3 canals with regard to RSC and 13 canals with regard to MR. According to USSL diagram, 24% of drainage waters were classified in C2S1, 62% in C3S1, 4% in C4S2 and 10% in C4S4 class. In January 2013, EC values varied between 0.16-1.44 dS/m. Waters of one canal was found to be unsuitable for irrigation with regard to KI and 8 canals with regard to MR values.
The result obtained from paired sample t-test revealed that the drainage canal water quality varies significantly between June 2012 and January 2013 except for Ca, Mg and SO4. According to analysed parameters, some of the drainage canals were considered unsuitable for irrigation in june 2012. The water properties of all canals were observed as unsuitable to be used for drip irrigation in accordance to the LSI index. Classification of drainage water by USSL diagrams indicates a low sodium and high salinity hazard.