Source apportionment, hydro-geochemistry, drinking and irrigation suitability of groundwater in arid state of Rajasthan, India: a multivariate statistical perspective

In semi-arid and arid parts of the globe, groundwater is the most vital natural resource meeting the needs of the agricultural, drinking, domestic and industrial sectors, owing to the inadequate availability of surface water and scant rainfall. The present study is focused on irrigation and drinking suitability, hydro-geochemistry, and source distribution of groundwater in the arid area of Rajasthan, India, where groundwater is utilized to meet the demands of the irrigation and drinking sectors. Fifty-six groundwater samples from tubewells installed at various rural locations of Ratangarh tehsil of Rajasthan were investigated for 15 parameters following standard procedures. Average dominance of ions followed the order : Cl− > HCO3− > SO42− > NO3− > CO32− > F− for anions, and Na+ > Mg2+ > Ca2+ > K+ for cations. The NO3− levels varied from 10.99 to 154.41 mg L− 1. High nitrate levels might have originated from the application of nitrogenous fertilizers in this agriculture dominating area, and animal and human waste. Water Quality Index revealed that 98% groundwater samples are poor to unsuitable for human consumption. Multivariate statistical analysis suggests that the origin of F− can be ascribed predominantly to lithogenic (geogenic) processes and that of nitrate to technogenic activities. Irrigation indices like %Na, Kelly’s Index, Residual Sodium Bicarbonate and Residual Sodium Carbonate indicate the unsuitability of groundwater for use in agriculture. Continual irrigation with such water may reduce the permeability of the soil, as the water has excessive sodium. Also, excessive bicarbonate may lead to alkalinity hazard and precipitation and deposition of sodium carbonate in soil. Na-HCO3-Cl hydro-geochemical facies followed by Na-Cl-HCO3 are the prevailing facies. Various bivariate ionic scatter plots, in addition to Chadha’s, and Gibbs plots, reveal that silicate or non-carbonate weathering, accompanied by ion-exchange and evaporite dissolution processes, are the major mechanisms governing the hydrogeochemistry of groundwater in Ratangarh area. Multivariate statistical analysis, along with diverse bivariate ionic crossplots, facilitated to unravel the hidden ionic relationships in the groundwater of Ratangarh area.