An extensive database from eight Triassic (Bunter) sandstone catchments in the Black Forest, SW Germany, was used to apply the MAGIC model and simulate long-term acidification trends. Using the ion ratio (Ca+Mg)/(SO₄+NO₃) as criterium (values< 1.5="" indicate="" an="" acidified="" state),="" hindcast="" simulations="" showed="" that="" the="" brooks="" of="" three="" catchments="" have="" reached="" values=""><1.5, three="" catchments="" are="" approaching="" 1.5,="" and="" two="" catchments="" (carbonate="" bearing="" upper="" bunter)="" are="" still="" well="" above="" this="" limit.="" the="" different="" acidification="" state="" of="" the="" catchments="" is="" mainly="" caused="" by="" the="" amount="" of="" acidic="" deposition="" and="" bedrock="" geology.="" other="" differences="" (shallow="" or="" deep="" groundwater="" circulation,="" sulphate="" sorption="" and="" soil="" parameters)="" are="" less="" significant.="" to="" simulate="" the="" future="" evolution,="" three="" scenarios="" were="" tested:="" a="" pessimistic,="" an="" optimistic="" and="" a="" most="" probable="" case.="" the="" latter="" leads="" to="" a="" still="" progressing="" but="" decelerated="" acidifcation="" in="" the="" next="" 100="" years.="" in="" the="" pessimistic="" case,="" acidification="" rates="" will="" be="" accelerated="" in="" two="" of="" the="" catchments.="" even="" in="" the="" optimistic="" case,="" the="" initial="" state,="" prior="" to="" acidification,="" cannot="" be="" restored="" up="" to="" the="" year="" 2130.="" however,="" the="" forecasting="" of="" the="" future="" evolution="" is="" still="" markedly="" hampered="" by="" the="" significant="" uncertainty="" in="" the="" evaluation="" of="" nitrogen-driven="" acidification,="" a="" process="" which="" today="" already="" predominates="" in="" parts="" of="" the="" black="">