A system for modelling groundwater contamination in water supply areas: chloride contamination from road de-icing as an example

A system for modelling groundwater contamination in water supply areas is presented, consisting of the flow and transport models, MACRO for the unsaturated zone and MOC for the groundwater zone, coupled to the geographical information system, IDRISI. A graphical user interface links the different parts of the system. The system was applied to a water supply area located close to a major road south of Stockholm. Chloride was used as an indicator in determining the risk for groundwater contamination from the road. The future chloride concentration in the aquifer was predicted and the effects of different pumping rates on the chemistry of the water supply well were tested. Modelling results showed that the chloride concentration in the aquifer will increase substantially due to road de-icing and that it will take decades to lower the chloride concentration down to the original background values after an end to the use of de-icing salt. The system may serve as a valuable tool in a planning context. Potential groundwater contamination scenarios can be simulated, and alternative groundwater management strategies can be evaluated.