Evaluation of Groundwater Quality for Irrigation in Central Plain of Fars Province, Iran

Total soluble salt is the most important index for assessing irrigation water quality. High concentrations of anions or cations affect quality of irrigation water either directly or indirectly. In order to assess water chemistry and type, sixty groundwater samples were collected from different wells in Fars Province. Anionic and cationic concentrations of water samples were measured and saturation indices were calculated. The chemical composition of water samples was plotted in piper diagram. This diagram revealed that Cl- and Na+ were the dominant ions in the water samples studied. Seven out of 60 water samples fell in the nonrestrictive class. The higher value of SAR coincided with the high values of EC, therefore, 95 percent of the samples could be used for irrigation with little danger of infiltration problems. Sixty three percent of the groundwater samples had magnesium ratios more than 50%, showing an imbalanced concentration of Mg compared to Ca. Saturation indices of the studied waters showed that water samples were saturated with respect to calcite, aragonite and dolomite, while a small number of water samples (1.6 %) contained high concentrations of SO42-, which, upon further concentration, could precipitate in the soil.