The closure of large mines causes a systematic disturbance to the hydrogeological environment. Pollution arises after flooding of the abandoned workings leads to discharge at the surface. As the general character of mine systems is one of extreme yet orderly heterogeneity, in terms of both permeability and dominant flow regime, standard techniques for modelling groundwater flow and quality are inappropriate. Furthermore, spatially distributed models require a large amount of data, generally not available when considering large mining areas. We adopt a global approach to simulate changes in sulphate concentrations in mine discharge water in the Lorraine iron basin, France, and test this method on the iron mine of Saizerais, abandoned 20 years ago.