| Summary: | The monitoring programme for the water quality of Norwegian rivers «Elveserien» was started in 1965/66 with rivers located in the acidified areas in the southernmost part of Norway. The number of locations has varied over time and in 2011 the monitoring program included 20 locations distributed from Åna in southernmost Norway to Skallelva in Northern Norway. Samples are analysed for turbidity, colour, conductivity, pH and alkalinity. Some samples are also analysed for calcium, manganese, sodium, potassium, sulphur, chlorine, silicon, aluminium concentrations and nitrate. Acid neutralizing capacity (ANC) was calculated where possible. During the last six years also total phosphorous (Tot-P), total nitrogen (Tot-N) and total organic carbon (TOC) have been analysed in one yearly autumn sample (September-November). In several rivers, especially in the southernmost part of Norway, the water is characterized by low pH, alkalinity and calcium concentrations. These localities are situated within areas which are affected by acid precipitation, and the water quality may have negative effects upon fish and other freshwater organisms living in these rivers. The water quality of the rivers Rondvatn, Store Ula, Åna, Otra and Haugsdalselva in 2011 indicates an ecological status of “moderate” or worse based on the criteria suggested for the implementation of the Water Framework Directive in Norway. However, the acidification situation in these rivers has shown a clear improvement in the 1990ies with an increase in pH and ANC and a decrease in inorganic (toxic) aluminium. Most localities in middle and northern parts of Norway have a high content of calcium and high alkalinity and pH levels. For most rivers nutrient levels are generally low, or even very low. Rivers Imsa and Vefsna dis-play the highest levels of phosphorous, but the concentrations indicate no signs of deviation from reference conditions. However, the levels of nitrogen in the River Imsa indicate an ecological sta-tus of poor based on the criteria suggested for ...
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