Maridalsvannet

Drinking water reservoir for Oslo

Maridalsvannet the largest lake in Oslo in Maridalen and lies between Nordmarka and Lillomarka. The lake has an area of 3.83 km ² and is located 149 meters above the sea level. Maridalsvannet is part of the Nordmarksvassdraget and supplies its water from the south by the Akerselva.

The lake is Oslo's drinking water reservoir and covers about 90 % of Oslo's water consumption. The water is treated in the Näne in the Oset water treatment plant.

One of the major tributaries that flow into the Maridalsvannet, comes from the Skjærsjøen in the northwest and passes through the power plant Hammeren, the oldest hydroelectric plant in Norway.

October 2007: Contaminated drinking water in Oslo

On 17 October 2007 there was a warning for drinking water from the Maridalsvannet. It had been discovered at three locations Giardia intestinalis - parasites in drinking water that had come through the Oset water treatment plant.

On October 21, the drinking water was again fit for human consumption in Oslo.