Assessment of water suitability for irrigation and drinking purposes in Western Nepal using an index-based and nexus approach
Samiksha Pokhrel, Mahesh Prasad Awasthi, Samichhya Paudel, Puja Puri, Aashish Chapagain, Rejina Maskey Byanju, Pramod N. Kamble, Motee Lal Sharma, Ramesh Raj PantABSTRACT
Drinking and irrigation water quality is essential for sustainable agriculture, soil health, ecosystem balance, and human well-being. This study evaluated the drinking and irrigation suitability of the Banganga Irrigation Canal, Kapilvastu, Nepal, using an index-based and nexus approach. Fifteen water samples were analyzed for hydrochemical parameters, i.e., pH, EC, TDS, total hardness, alkalinity, major cations, and major anions. Drinking water quality was evaluated using the Water Quality Index (WQI), while irrigation suitability was determined through the Sodium Adsorption Ratio, Sodium Percentage, Magnesium Adsorption Ratio, Kelly’s Ratio, Permeability Index, Cation Ratio of Soil Structural Stability, Residual Sodium Bicarbonate, and Potential Salinity. Results showed that the water was slightly alkaline and hydrochemical composition followed the order Ca2+>Mg2+>Na+>K+>Fe³+>NH4+ for cations and HCO3−>Cl−>SO4²−>NO3−>PO43− for anions. The WQI classified all samples as ‘Excellent’ for drinking and irrigation indices confirmed the suitability of water for same purposes. The Wilcox diagram classified most samples as C2–S1, indicating low sodium hazard and moderate salinity water suitable for irrigation. However, elevated MAR and PI values at some sites suggest localized risks of magnesium hazard and reduced soil permeability. The results emphasize the water–soil–agriculture nexus and provide scientific evidence to support integrated water resource management, climate-resilient agriculture, and the achievement of SDGs 6, 13, and 15.