Assessment of groundwater quality and its controlling processes in Bemetara District of Chhattisgarh State, India

Groundwater withdrawal at very fast rate poses threat on existing groundwater resources in different parts of the world. This reduction in groundwater levels significantly disturbed the natural aquifer flow rate and thereby different hydrogeochemical processes, which may further impair the groundwater quality. The groundwater quality in rural area of Chhattisgarh State is degraded, and the problem of saline water poses health risk to people. In this research investigation, suitability of groundwater of Bemetara District, Chhattisgarh, India, has been evaluated for drinking purpose through water quality index (WQI) method and principal component analysis (PCA). Total 116 groundwater samples were collected during the pre-monsoon (June 2019) and post-monsoon season (December 2019) and analyzed for physicochemical parameters. Total dissolved solids ranged from 250 to 10,440 mg/L and 289 to 3583 mg/L during pre-monsoon and post-monsoon, respectively, and 55% of the total samples exceeded acceptable BIS limit in pre-monsoon, while about 66% samples exceeded in post-monsoon season. SO42- concentrations varied from 3 to 5734 mg/L during pre-monsoon and 4.5 to 2002 mg/L during post-monsoon, respectively. Total 28% samples in pre-monsoon and 18% samples in post-monsoon season exceeded the maximum permissible BIS limit (400 mg/L) of SO42- ion in the study area. On the basis of WQI, the quality of groundwater varies from "Excellent water" to "Good water" category. The groundwater of northeastern part of the district is not suitable for drinking, and therefore, it is recommended to treat this groundwater before human consumption with special reference to SO42- contamination. PCA inferred that four components are sufficient to explain the variance in chemistry of groundwater that is mainly governed by dissolution of gypsum mineral, other rock-water interaction and anthropogenic activities. Further, water quality was improved in the direction of groundwater flow in the study area, establishing a direct relationship between groundwater flow and water quality of the Bemetara District. This study provides very useful database to design sustainable groundwater management plan for the district.