Monitoring of six mountain lakes in the county of Oppland, S Norway 2014

Summary

The report presents results from an investigation of water quality and environmental state of three lakes in mountain areas on both sides of the valley Gudbrandsdalen and three lakes in the mountain area east of Lillehammer in 2014. The main focus for the monitoring has been eutrophication. The lakes are all situated at an altitude of 850-920 m above sea level, and they vary in size from 0.26 km² to 5.27 km². All six lakes have low concentrations of calcium (1.4-3.6 mg Ca/l) and low concentrations of humic acids (12-27 mg Pt/l). Based on data on algal amount (chlorophyll-a) and concentrations of nutrients from 2013 (Aulie 2014) and 2014 we concluded that the ecological state of Lake Furusjøen and Lake Øyangen was good. The ecological state of Lake Skjervungen was also classified as good. However, this conclusion is more uncertain as it is based on only one year of monitoring data. Besides, the algal amount and the tot-P content seemed slightly more elevated in Lake Skjervungen compared to the lakes Furusjøen and Øyangen. The three lakes in the Mesna water course (Reinsvatnet, Nevelvatnet and Mellsjøen) all seemed to be significantly affected by anthropogenic inputs of nutrients. The amounts of planktonic algae were high, especially in Lake Nevelvatnet, and the concentrations of total phosphorus were markedly higher than what is assumed to be reference levels in this type of lakes. Based on water quality data from 2013 (Aulie 2014) and 2014 the ecological state of Lake Reinsvatnet and Lake Mellsjøen was classified as moderate while the ecological state of Lake Nevelvatnet was classified as bad. A comparison of monitoring data from 1992-1994 (Rognerud et al. 1995) with data from 2013-2014, indicated improvement of the environmental conditions of Lake Mellsjøen during the last two decades. Also in Lake Reinsvatnet concentrations of nutrients seem two have declined slightly. However, in this lake we found no indications of changes in the amount of algae during the same period of time.