Hydrochemical monitoring of groundwater quality for drinking and irrigation use in Rapti Basin

Abstract

In the present study, groundwater of Siddhartha Nagar district was investigated to ascertain its quality for drinking and irrigation purposes based on Groundwater Quality Index (GWQI) and irrigation indices. Inverse Distance-Weighted (IDW) application was also used to prepare the spatial distribution maps of each groundwater quality parameter. It is observed that Total Dissolved Solid (TDS) in 41.6% of samples and Total Hardness (TH) concentrations in 75% (BIS)/100% (WHO) of samples were much higher than the permissible limit. GWQI values reveal that none of the samples has an excellent quality of water and 16.7% samples having good water quality. Similarly, 33.3%, 41.7% and 8.3% of samples has a fair, poor and very poor water quality respectively. Results from the Piper plot showed that Ca–HCO3 is the dominant hydrochemical facies. All samples were found in the rock dominance zone in Gibbs plots. Based on residual sodium carbonate (RSC) and soluble sodium percentage (SSP), 8.33% and 33.33% of the samples were found to be in the poor category and according to Kelly’s ratio (KR) 8.33% of the samples were found in unsuitable category. Permeability Index (PI) indicates that 50% of the groundwater samples were found in Class I (suitable) and 50% in Class II (marginally suitable) category for irrigation purpose.