EFFECTS OF FUTURE N DEPOSITION SCENARIOS ON THE GALLOWAY REGION OF SWSCOTLAND USING A COUPLED SULFUR AND NITROGEN MODEL (MAGIC-WAND)

The Galloway region of Southwest Scotland has been subject to decades of acidic deposition which has resulted in damage to soils, surface wa ters and aquatic biota. A survey of lochs was conducted in 1979, 1988, and 1993, over which time there have been dramatic changes in total s ulphur and nitrogen deposition. The MAGIC model successfully reproduce d the major chemical changes in water chemistry from 1979 to 1988 duri ng which time there was a rapid decline in sulphur deposition. A new c oupled sulphur and nitrogen model (MAGIC-WAND) has been used to evalua te the regional hydrochemical response to changing patterns of N & S d eposition from the period 1988 to 1993. Details of the model structure and parameterisation are discussed. The model under-predicts the resp onse of non-marine sulphate in the region suggesting that there has be en a slight increase in deposition over this period. Future hydrochemi cal responses to different nitrogen deposition scenarios are presented , indicating that the potential increase of nitrogen in surface waters is closely linked to the age and extent of different mosaics of comme rcial afforestation within the individual catchments.