Experiences from a case study of multi-model application to assess the behaviour of pollutants in the Dnieper–Bug Estuary

The present paper describes the results of the application of four state-of-the-art models to predict the concentrations of pollutants in the abiotic components of the Dnieper–Bug Estuary (Ukraine). The estuary was contaminated by the radioactive substances introduced in the environment following the Chernobyl accident. The scope, the methodological approaches and the theoretical foundations underpinning the examined models are presented and compared. The model performances were assessed by comparison with available empirical data of water contamination. The main factors influencing the inherent uncertainty of the models were examined: incomplete knowledge, paucity of extensive data sets relevant to some environmental quantities, the vagueness and the ambiguity of certain information about environmental processes that can be hardly parameterised in quantitative way, etc. Model performances reflect the intrinsic uncertainty of knowledge concerning the quantitative behaviour of the involved environmental process, the ambiguity of interpretation and parameterisation of such processes, the inherent variability of environmental quantities, etc. The difficulties in selecting the “best performance” model and the benefits arising from a multi-model approach to afford complex environmental problems are presented and discussed. Multi-model approach helps to get an insight into complex problems of environmental management, to promote co-operation among modellers and to profit by the different perspectives of the models.