WATER QUALITY ASSESSMENT USING THE POLLUTION INDEX MODEL (PIJ) FOR IRRIGATION PURPOSES. A CASE STUDY: DOHUK VALLEY WATER IN NORTHERN IRAQ

A field survey was conducted for Duhok valley, fields and orchards in northern Iraq, where water is used for irrigation. Six sites were identified for collecting water samples starting from February 2021 until January 2022 to estimate both (pH, Electrical conductivity (EC25), chloride ions (Cl- ), bicarbonate (HCO3 - ) as well as irrigation parameters such as sodium adsorption ratio (SAR), residual sodium carbonate (RSC), sodium percentage (% Na), permeability index (P.I), kelly ratio (K.R), Magnesium hazard (M.H) and potential salinity (P.S). The pollution index (PIJ) model was used to assess water quality for irrigation. The results of the current study indicated that the water quality index (PIj) values ranged between (0.9691 to 1.4559) and that 66.7% of the water samples were from the Lightly polluted water category, and the rest were from the good quality category for irrigation purposes. The relative deterioration of most of the irrigation water samples is attributed to the high concentration of bicarbonate ions (HCO3 - ) and the magnesium hazard (M.H), which reached (7.80) meq. l-1 and (84.0), respectively.