Acidification in Norway - Status and trends - Surface and ground water

Surface and ground water monitoring in Norway is designed to give a regional coverage with most of the stations in areas with acidification and some stations in unpolluted areas that give background values. Surface water (weekly sampling) and precipitation (daily measurement) are monitored at 6 calibrated catchments, 5 located in southern Norway and 1 in northernmost Norway close to the Russian border. Ground water (weekly sampling) is monitored in 4 reservoirs in Southern Norway. 73 lakes located all over Norway are surveyed each fall. Nineteen rivers in western and southern Norway are monitored by monthly sampling. All sites are considered sensitive to acidification and are chosen to minimise the effects of anthropogenic catchment based impacts. Results from the monitoring over the period 1980-1994 show that there is a reduction of sulphate of about 25-35% in surface waters which is related to a 30-45% reduction in sulphate concentration in precipitation. An improvement in water quality as measured as increase in ANC has only been apparent since 1990. Due to heavy seasalt episodes in the most coastal catchments like Birkenes and the dyers in western Norway, there has been no improvement of ANC since 1980. Deposition of nitrogen has not changed over the last 10 years, and there is no change in the levels of nitrate in the monitored surface waters.