Assessment of Groundwater Suitability for Drinking and Irrigation Purposes Using Water Quality Index, Seawater Mixing Index, Human Health Risk Assessment, and Irrigation Suitability Indices

Groundwater has been depleted much faster in recent decades due to anthropogenic activities. Many pollutants enter water bodies through domestic sewage and industrial wastewater, lowering water quality. The health risks associated with water quality are critical for long-term water management in coastal regions of India. This study analyzed groundwater quality, seawater intrusion, hydrogeochemical processes (Piper trilinear graph and Gibbs plot), and statistical data in Tiruvallur district, Tamil Nadu, India. Water quality data were collected at 58 sampling stations. The water quality index (WQI) results showed that water in 12 stations was unsuitable for drinking. 20 stations exhibited poor water quality, while 20 were very poor. The extent of seawater intrusion into the study area was calculated using the seawater mixing index (SMI), and the results indicated that only one station had an SMI value of >1. A human health risk assessment (HHRA) was performed based on the nitrate and fluoride concentrations. The results showed that 39.65% of stations posed nitrate risks to children, while 20.68% posed risks to adults. By comparison, fluoride-related risks affect 34.48% of the stations in children, but only one station in adults.