Application of the First-order Acidity Balance (FAB) model to Norwegian surface waters

Abstract

We have applied the First-order Acidity Balance (FAB) model and the Steady State Water Chemistry (SSWC) model to data from the Norwegian lake survey carried out in 1995, the Norwegian Critical Load database, the calibrated catchments and the rivers monitored through the national programme for long-range transported air pollutants and to seven lakes monitored through the REFISH-project. Today, with present N-leaching, 29% (11.000 lakes) of the lakes in Norway are exceeded, while 44% (16.700 lakes) will be exeeded at maximum N- leaching. In year 2010 the number of exceeded lakes will be reduced to 6.800 lakes (18%) at present N-leaching, while 13.000 laks (35%) will be exeeded at maximum N-leaching. Most rivers and calibrated catchments will still be exceeded at present N leaching when the Second Sulphur Protocol has been implemented, but only N-reduction will then be required to reach non-exceedance. At present N-leaching, however, they will reach non-exceedance at the Second Sulphur Protocol scenario. The future acidification situations estimated by means of the two models clearly indicate that nitrogen will be the critical factor in the future. The crucial questions are whether the situation predicted by the FAB-model ever will occur for lakes and rivers and whether the present leaching will increase with present N-loading.