To assess long-term acidification trends models are required that can characterize the principal mechanisms operating, account for the changing levels of deposition inputs and provide good estimates of past, present and future soil and water chemistry. At the same time the model should be transferable so that it can be readily applied to a wide range of catchments in differing pollution climates with differing land-use regimes and differing soils and parent geology. In this paper the application of MAGIC (model of acidification of groundwaters in catchments) is described for moorland and afforested catchment sites in Scotland and Wales. In addition, MAGIC has been applied in a regional analysis to predict distributions of water quality across Wales and the Galloway region of Scotland. The sensitivity of the model to parameter variations between sites is explored and the model used in a predictive mode to assess effects of land-use change such as afforestation and the likely changes in future atmospheric pollutant deposition levels.

The model results support the findings of palaeoecological studies that acidification has occurred in many U.K. catchments and demonstrates a clear link between deposition of atmospheric pollutants and acidification.

Introduction

Acidification may be regarded as essentially a problem over two very different timescales.