Effects of clear-cutting of forest on the chemistry of a shallow groundwater aquifer in southern Norway

International audienceAs part of the national monitoring programme for long-range transported air pollutants, four groundwater aquifers in southern Norway were monitored for acidification trends during the period 1980 ? 1995. For the monitoring station, Langvasslia in south eastern Norway, sampling continued until the end of 1999. This groundwater aquifer is about 3 km north east of the calibrated catchment Lake Langtjern. The catchment of the groundwater aquifer, covered completely by Norway spruce, was clear-cut in September 1986 and was treated with glyphosate in the summer, 1991. The chemical effects on the chemistry of the groundwater are generally similar to those observed in stream-water from clear-cut areas: increases in water runoff, water temperature, concentrations of K, NO3, and organic carbon (TOC), and decrease in SO4 concentration. In the groundwater aquifer, inorganic Al and ANC increased more than would have been expected without clear-cutting. By 1999 NO3 concentrations were nearly the same as prior to clear-cutting, whereas K still was elevated. Keywords: Groundwater; clear-cutting; water chemistry; monitoring.