Abstract
For 40 years MAGIC has been used to simulate the acidification of soils
and waters due to acid deposition. The original model has now been
updated and re-implemented in the C++ Mobius platform and is available
as open source. New features include multipoint calibration, forest
growth, and a soil carbon module. The Mobius platform facilitates
automatic optimisation of calibrated parameters and
multiple-calibrations using Monte-Carlo routines. The usefulness of
MAGIC is demonstrated by application to the 50-year data series for
deposition and runoff at Birkenes, a small, calibrated catchment in
southern Norway. Acid deposition has declined dramatically at Birkenes
since the peak in the 1970s. Sulphate is 90% lower. Stream water has
recovered strongly. Decreased concentrations of sulphate have led to
increased acid neutralising capacity, pH and reduced concentrations of
toxic aluminium. These changes are well-simulated by MAGIC. The new
features added as part of Mobius improve the simulations. The
MAGIC-Mobius modelling tool is now available for applications to
scenarios of land-use and climate change.