Sammendrag
The report presents the results from investigations of water quality and environmental status of four lakes
and 7 brooks and rivers in the municipality of Ringsaker in 2013. The main topic has been water quality
effects from anthropogenic inputs of nutrients (eutrophication). An assessment of the water quality of the
lake Nord-Mesna as a potential water source for a new waterworks has also been an important part of the
project.
Based on amounts and composition of phytoplankton, composition of zooplankton and concentrations of
nutrients in 2013, the environmental status of the lakes was characterized as follows:
Lake Ljøsvatnet: bad
Lake Kroksjøen: moderate
Lake Sjusjøen: moderate
Lake Nord-Mesna: high – good
To achieve drinking water quality from Nord-Mesna, measures must be taken to remove humic matter,
remove bacteria, virus etc. (disinfection) and to alkalize the water.
Nevla, Bustokkelva and Tyria (outlet from a hydro power plant) are supposed to be the most important
inlet rivers to Lake Nord-Mesna. The rivers were slightly or moderately influenced by faecal indicator
bacteria. However, a locality in the lower part of Tyria (original water course), showed high concentrations
of tot-P and E. coli. This was probably an effect of the outlet from the Mesnali wastewater treatment plant.
The small streams Dælibekken, Sløebekken, Fossumbekken and Mælumsbekken were markedly influenced
by runoff from agricultural areas. Besides, a part of Dælibekken, showed clear signs of pollution from the
outlet of the municipal wastewater treatment plant at Brøttum.
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