Entropy-weighted water quality index and TOPSIS for irrigation suitability assessment in eastern Odisha, India

Groundwater irrigation is increasingly practised in the eastern districts of Odisha, India, highlighting the need for systematic evaluation of irrigation water quality. Groundwater quality data (pH, EC, TDS, total hardness, major cations, and anions) were obtained from the Central Water Commission (CWC) and India-WRIS (2023) databases. The dataset includes 43 villages across eastern Odisha, mainly from the coastal districts of Balasore, Bhadrak, and Puri, with additional sites in Jajpur, Dhenkanal, and Mayurbhanj, representing both coastal and inland hydrogeological conditions. High values of sodium adsorption ratio (SAR), residual sodium carbonate (RSC), Kelly’s ratio (KR), permeability index (PI), magnesium ratio (MAR), and per cent sodium (Na%) were observed in several locations, which may adversely affect soil permeability and crop productivity if irrigation practices are not properly managed. Entropy analysis further identified chloride, Kelly’s ratio, and potential salinity as the most influential parameters controlling groundwater quality variability. An integrated approach combining the entropy-weighted water quality index (EWQI) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was applied to evaluate irrigation water quality and rank sampling locations. The EWQI results indicate that most groundwater samples fall within the excellent to good quality categories, suggesting that the overall hydrochemical composition is generally suitable for irrigation. However, the TOPSIS ranking reveals spatial variability, with approximately 94% of samples classified as moderate quality, 4% as poor quality, and only 2% as good quality, indicating localised salinity and sodicity risks. The TOPSIS analysis indicated that Bimbalabar and Ramchandrapur villages in Bhandaripokhari block exhibited the lowest closeness coefficient values, representing relatively better water quality, while other locations showed higher closeness coefficients, indicating moderate irrigation suitability. Most of the readings are ≤ 0.5, as estimated by TOPSIS for most stations. The integrated EWQI–TOPSIS framework provides a robust decision-support approach for identifying priority areas for groundwater management and supporting sustainable irrigation planning in the eastern districts of Odisha.