Dynamic Modelling of Surface Waters: Impact of emission reduction - possibilities and limitations (ICP Waters report 70/2002)

Dynamic models provide an extension to critical loads by predicting the timescale of chemical recovery to emission reductions. They can also be used to determine the deposition levels required to achieve a prescribed target chemistry within a given timescale and so have direct utility in the formulation of further emission reductions. The MAGIC model has been tested extensively against long-term diatom reconstructions, experimental manipulation experiments and long-term chemistry observations and has in all cases been found to successfully capture the dynamics of chemical change. This also provides confidence in the predictions from the model. Methods for summarising regional model predictions are summarised and a methodology for the derivation of 'target' loads is proposed for use within the Convention. Requirements for further research, including model uncertainty and the link between surface water chemistry and biological receptors, are outlined