Irrigation water quality (IWQ) index is an integrated method that is based on the linear combination of the five different groups of irrigation water quality parameters that have potential negative impacts or hazards on soil quality and crop yield.
The IWQ index uses EC to represent the salinity hazard; EC and SAR are assessed together to represent the infiltration and permeability hazard; chloride and sodium (SAR) to represent the specific ion toxicity; linear combination of trace metals to represent the trace metals toxicity; and linear combination of bicarbonate and pH to represent miscellaneous effects to sensitive crops.
Table-2: Classification for irrigation water quality (IWQ) index parameters.
IWQ (less then) 22, indicates low suitability of water; IWQ = 22-37, demonstrates medium suitability of water; and IWQ (greater then) 37, shows high suitability of water for irrigation.
Finally, areas with IWQ index values of less than 22 are considered to be poor quality irrigation water and are not suitable for irrigating agricultural fields.
The IWQ index is believed to be a suitable tool for agricultural management plans and in determining the most suitable site for assessing the overall water quality.
The IWQ index evidenced that the water was of medium level suitability for the agricultural use.