Evaluating seasonal variability of hydrogeochemistry, qualitative and corrosion-scaling effects of groundwater in southern region of NCT of Delhi, India

Groundwater is the most relied source of freshwater in the unplanned areas of southern region of NCT of Delhi. The present study envisions to evaluate the seasonal variability of the hydrogeochemical and qualitative nature of the groundwater, where its suitability was further checked through groundwater quality index (GWQI) and water stability indices for corrosion-scaling effects. About 12 physiochemical parameters were analysed with a total number of 102 samples in pre-monsoon (PRM) and post-monsoon (POM) seasons. Spatially, higher ranges of the quality parameters viz., EC, TDS, HCO3- , Cl- , NO3- , F-, Ca2+, and Mg2+ were observed in both the seasons particularly in north, northeastern, and southeastern parts and has nearest dumping or industrial units such as printing, trade and textile effluent, food, and fruit processing industry etc. The hydrogeochemical characteristics of the groundwater showed that regulating processes is predominant by carbonate weathering process followed by silicate weathering under alluvial plains of the study area. Strong correlations and positive loadings (>0.8) among EC, TDS, HCO3- , Cl-, Na+, and moderate loadings of F-, potassium (K+) and Mg2+ were attributed to mixed pollution factors released from geogenic and anthropogenic inputs. GWQI based classification showed that more than 50% of the sampling sites showed poor to unsuitable groundwater quality at sites like Malviya Nagar, Okhla, Jasola, Shaheen Bagh, Badarpur and Greater Kailash for potability. The entire area is prone to groundwater contamination, particularly northeastern, and southeastern region, falls under Yamuna flood and alluvial plains with shallower groundwater table. Water stability indices (LSI, RSI, PSI, LS, and AI) based corrosionscaling effects have revealed that groundwater samples in PRM showed low to insignificant scaling and corrosive potential compared to POM season. Therefore, the findings of the study highlight the key areas that needs to formulate the strategies to sustain the quality of groundwater within the region.