Hydrochemical exploration and assessment of groundwater quality in part of the Ganga-Gomti fluvial plain in northern India

Abstract

Groundwater quality in the Ganga-Gomti fluvial plain is influenced by geogenic and various anthropogenic factors like human interventions, urbanization, mineral dissolution, and ion-exchangeability. This study provides in-depth information about the groundwater quality and its suitability for drinking and irrigation use in Lucknow district of Uttar Pradesh state, India. The results based on pH, electrical conductivity, total dissolved solids, total hardness, Ca2+, Mg2+, Na+, K+, HCO3−, SO42−, Cl− and F− suggest that most of the groundwater is appropriate for drinking usage. In contrast, elevated NO3− concentration was found in about 6% of the samples, which is much higher than the no-relaxation limit of 45 mg L−1 set by the Bureau of Indian Standards. Based on the water quality index (WQI), the study reveals that 34% of the samples have good water quality for drinking usage, while 55% of the samples are of the fair type and about 11% of the samples indicate poor quality water. The Gibbs plot suggests that rock weathering or rock-water interaction processes are dominant in the investigated area controlling groundwater chemistry, particularly silicate weathering mostly due to the forward ion-exchange. The Piper plot indicates that Ca2+-HCO3- is the major hydrochemical facies, along with the dominant presence of Na+-HCO3- resulting in mixed Ca2+-Na+-HCO3- type water. Groundwater quality for irrigation purposes was evaluated using suitable indices and ratios such as sodium absorption ratio, residual sodium carbonate, sodium soluble percentage, magnesium hazard ratio, Kelly's ratio, percent sodium, permeability index and potential salinity. The overall values of these indices and ratios show that most of the groundwater is suitable for irrigation use, except for the MHR which indicates that 87% of the samples are unsuitable for irrigation usage.