Results of national lake surveys (1995) in Finland, Norway, Sweden, Denmark, Russian Kola, Russian Karelia, Scotland and Wales

Abstract

In the autumn of 1995, national lake surveys were conducted in six Northern European countries on the the initiative of the environmental authorities in Sweden, Finland and Norway. The project was subsequently expanded to include Denmark, Russian Kola, Russian Karelia, Scotland and Wales. This report therefore provides the first united evaluation of lake water chemistry in the whole of northern Europe. The results show that lake water chemistry in this area (except Denmark) are characterized by low ionic stregth (dilute) waters, with low content of nitrogen and phosphorus. In Finland, Norway, Sweden, Russian Kola and Karelia more than 50% of the lakes have low critical load (CL) values for sulphur acidity (S) (CL<60 meq-m²-yr-¹) while Scotland, Wales and Denmark have very few lakes with low CL for S. The highest percentage (27%) of lakes with exeedance of CL for S is found in Norway. In Russian Kola, Sweden and Finland 17,9 and 9% of the lakes respectively hav exceedance of CL for S. In Scotland and Wales, critical loads for sulphur acidity is exceeded in 1% of the total lake population. For Denmark and Russian Karelia the number of sampled lakes is too low to give reliable estimates. In total, this adds up to approximatley 22.000 lakes in Northern Europe were CL for S is exceeded. However, this number of lakes is a minimum value as exceedence of CL for N is not included in the calculation due to lack of catchment data.