A mathematical approach to groundwater quality and pollution of Adyar sub-basin, Tamil Nadu, India

The quality of drinking water sources in the Adyar river sub-basin of northern Tamil Nadu is assessed in this study. This research uses a combined water quality index (WQI) and pollution index (PI) to assess and characterise groundwater quality. Water samples will be collected from nine locations in the study area for the assessment. The water quality index was calculated based on Total Dissolved Substances (TDS), Nitrogen oxides (NOx), Calcium (Ca), Magnesium (Mg), Sodium (Na), Potassium (K), Chloride (Cl), Sulphate (SO4), Bicarbonate (HCO3), Fluoride (F), Power of Hydrogen (pH) and Electrical Conductivity (EC). These twelve parameters were analysed and characterised according to standard methods and the Indian standard, which were then used in calculating the water quality index. Groundwater quality and pollution status of the Adyar river basin were assessed using the Groundwater quality index and comprehensive pollution index for the years 1990, 2005, and 2020. A result reveals that the groundwater quality has decreased from 1990 to 2020. Around seven parameters exceeded the permissible limits in 1990, nine parameters exceeded the permissible limits in 2005, and around eight parameters exceeded the allowable limits in 2020. The pollution status of the groundwater has considerably reduced from 1990 to 2020. Eastern parts of the study area were highly polluted and had low groundwater quality.