EVALUATION OF WATER QUALITY OF DIYALA RIVER FOR IRRIGATION PURPOSES

The study comprised suitability evaluation water of quality of Diyala river for irrigation uses. Four stations were selected along Diyala river which are Jalawlah station (DI2) before Jalawlah Bridge, Saadiyah station (DI3) before inter to Hamren Dam, Muqdadia station (DI4) after Diyala Dam, and Baqubah station (DI5) at Iron Bridge, besides wand river station in Khanaqin (DIW) Before Dam. Water samples were collected and analyzed for pH, electric conductivity (EC), TDS, Na+, K+, Ca2+, Mg2+, HCO3-, CO32-, SO42-, Cl-, and NO3- one sample monthly were taken from these stations during January to December 2010.  In addition, to classifying water quality and evaluation its suitability for irrigation purposes, Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP) and Residual Sodium Carbonate (RSC) were calculated following standard equations and found experimentally as (0.985), (20.027), (-4.404) respectively. According to the EC and SAR  plotted on the US salinity diagram, it is illustrated that water samples of DIW and DI5 fall in the class of C3-S1 indicating high salinity with low sodium water, which can be used for irrigation on almost all types of soil with only a minimum risk of exchangeable sodium, while water samples of other stations fall in the class of C2-S1 indicating medium salinity with low sodium water, which can be suitable to salt tolerant plants with probability developed permeability problem of soil when Lime is not existing. RSC values are negative at all sampling sites, indicating that there is no complete precipitation of calcium and magnesium. All other parameters were within standard levels. The results of the study revealed that the quality of Diyala river water can be classified as suitable for irrigation with few exceptions.