Development of an Integrated Irrigation Water Quality Index (IIWQIndex) model

Abstract

There are many irrigation water quality indices used to assess water suitability, despite having limitations. It is therefore imperative to develop a water quality index to evaluate irrigation water more accurately. This study highlights an Integrated Irrigation Water Quality Index (IIWQIndex) using the sub-index and aggregated equations. This proposed index model was improved and updated across four characteristics: the verified desirable and permissible value of parameters, maximum hazard class, and modified rating system of diversified parameters. The proposed IIWQIndex model classified irrigation water into five categories: rejection, poor, moderate, good, and excellent. This model assessed two types of water to justify the model by categorizing the irrigation waters. The calculated results showed that the index values were 75.77 and 36.51, and the water category was ‘good’ and ‘rejected’ for the calcite (Ca–HCO3) and sodic (Na–Cl) water, respectively. This index model also satisfactorily evaluated different types of water datasets of eight geographic locations in the world. The study illustrated that the IIWQIndex evaluated values and water categories were rational and comprehensive at predicting the suitability of irrigation water. HIGHLIGHTS Critically reviewed the previous irrigation water quality (IWQ) indices.; Proposed a water quality index model (IIWQIndex) considering the maximum water quality parameters and hazard classes.; Modified the rating value and acceptable limit of parameters.; Evaluated the suitability and rationality of the index model for irrigation purposes.;

Keywords

• hazard class
• irrigation water quality indices
• soil structure
• water quality parameter
• water suitability
• water type