Assessment of Hydrochemical Facies and Drinking Water Quality of North-Eastern State of India, Tripura

ABSTRACT Groundwater is the most precious natural resource on this planet, and at the same time, it is also vulnerable to contamination with each passing day. The present study attempts to comprehensively understand groundwater quality in the Tripura state of India using the water quality and heavy metal evaluation indexes. The study also attempts to forecast the Water Quality Index (WQI) for the next two years from the study period. In this study, twelve key parameters viz., pH turbidity, total dissolved solids, bicarbonate, chloride, sulfate, nitrate, fluoride, calcium, magnesium, total hardness, and iron were considered for calculating the WQI and six heavy metals viz., iron, arsenic, uranium, manganese, zinc and copper for HEI. A total of 970 groundwater samples were collected from all the districts of Tripura over a decade, from 2013–14 to 2022–23. The findings reveal that high iron concentration in Tripura consistently surpasses the recommended limits set by both the Bureau of Indian Standards (BIS) and the World Health Organisation (WHO) standards, with some areas also experiencing elevated total dissolved solid concentrations. The South Tripura District reported the highest concentration of 28 ppm of iron. The output from WQI confirms that in most districts, water quality falls in the excellent to good category. However, a few locations from the West Tripura District exhibit poor to very poor water quality for drinking. Almost 80% of the water samples from the study area have been marked as excellent to good for drinking purposes, and none fall under the unsuitable category. Iron and WQI distribution graphs, along with the Piper diagram, were studied to explain the results of the study. The evaluation of the Heavy Metal Evaluation Index (HEI) shows that more than 97% of groundwater samples are at low risk for drinking. Piper diagram infers that the Groundwater in Tripura is mostly enriched with calcium cation and bicarbonate anion. Considering all the points, it may be assumed that the water quality in Tripura is good enough, and no significant major concern has been noted regarding groundwater quality for the last ten years. Predicted WQI considering all the same parameters for the next two years indicates that all the districts will fall within the “Excellent” category, highlighting overall enhancement in water quality.