Quantification of pollutant migration in the groundwater regime through mathematical modelling

The process of groundwater pollution is a complicated one and quite different from that of surface water pollution. In the case of surface water, the pollution is rapid and involves only short-term process. In contrast, the pollutant in the case of groundwater, may take a very long time to reach the saturated zone and get mixed with native water. It is, generally, accepted that groundwater pollution is irreversible, i.e. once it is polluted, it is difficult to restore the original water quality in a short span of time. It is, therefore, necessary to quantify the pollutant migration in the groundwater regime and take appropriate remedial measures to restore the aquifer system. Mass transport modelling technique has been proved to be a potential tool to study the pollutant migration. Finite difference technique coupled with the method of characteristics has been widely applied for quantification of pollutant migration. Besides outlining the salient principles of mass transport modelling, the use of this technique has been illustrated in the upper Palar river basin (Tamil Nadu) where groundwater has been polluted in about 200 km(2) due to discharge of untreated tannery effluents. The study has explicitly brought out that if tannery effluents continue to be discharged at the present level, the groundwater pollution will continue to increase both in volume and concentration.