A regional application of the MAGIC model in Wales: calibration and assessment of future recovery using a Monte-Carlo approach

摘要

A survey and resurvey of 77 headwater streams in Walesprovides an opportunity for assessing changes in streamwater chemistry in the region. TheModel of Acidification of Groundwater In Catchment (MAGIC) has been calibrated to thesecond of two surveys, taken in 1994-1995, using a Monte-Carlo methodology. The firstsurvey, 1983-1984, provides a basis for model validation. The model simulates asignificant decline of water quality across the region since industrialisation. Agreedreductions in sulphur (S) emissions in Europe in accordance with the Second S Protocolwill result in a 49% reduction of S deposition across Wales from 1996 to 2010. In responseto these reductions, the proportion of streams in the region with mean annual acidneutralising capacity (ANC) > 0 is predicted to increase from 81% in 1995 to 90% by2030. The greatest recovery between 1984 and 1995 and into the future is at those streamswith low ANC. In order to ensure that streams in the most heavily acidified areas of Walesrecover to ANC zero by 2030, a reduction of S deposition of 80-85% will be required.