The water quality in the main waterways
Oslo has eight main waterways – Alna, Frognerelva, Akerselva, Hovinbekken, Lysakerelva Mærradalsbekken, Hoffselva and Ljanselva. The water quality in Oslo is assessed based on the ecological status of benthic (i.e living in or on the sediments in the river) organisms. As of 2018, none of these waterways have the classification “very good water quality” and only Lysakerelva has “good” quality. The remainder waterways have either “moderately good”, “poor” or “very poor” water quality.
Benthic quality surveys are expensive and laborious, thus two of the eight main waterways are surveyed annually. This ensures that the water quality of all waterways is Oslo are assessed every fourth year.
The numbers are in EQR which stands for Ecological Quality Ratio which is a quality coefficient for a given waterway. EQR is the coefficient between an observed value for a given parameter, and the value of the natural state for the same parameter. You can read more about EQR at vannportalen.no.
EQR is divided in 5 categories:
- Very good: >0,98 EQR
- Good: 0,86-0,98 EQR
- Moderately good: 0,74-0,86 EQR
- Poor: 0,62-0,74 EQR
- Very Poor: <0,62 EQR.
The quality of potable water in Oslo
Until 2009 the only provider of high quality potable water originated from the Skullerud water treatment facility. The old water treatment facility at Oset in Maridalen occasionally exceeded the limits of humus content and (colour) and acidity (pH).
In 2008/2009 the treatment facility in Oset was upgraded to full treatment plant. As a consequence more or less the entire population in Oslo now had access to water meeting the requirements as described in the potable water regulations.
Until 2012 there were still 48 households in Sørkedalen that received potable water with high levels of humus and/or too low pH. After the Langlia water treatment facility was taken out of service inhabitants in Sørkedalen were supplied with water from the Oset facility. Now, all of Oslo’s inhabitants have high quality potable water that satisfies the regulations governed by the Norwegian Food and Safety Authority.
The graph shows water production and consumption in Oslo municipality. Water production is presented as million m3 (=billion litres). The consumption is based on numbers from January 1 the following year.