| Summary: | Netherlands: Environmental sciences at Van Hall Larenstein University of Applied Sciences, the Netherlands Norway: GE 491 Lake Hafslovatnet is part of a water system which lies in the county Sogn og Fjordane in Western Norway. At the base of this system lies the glacier Austerdalsbreen. Its meltwater passes, combined with normal precipitation, one river, one large lake and two small lakes before it passes Lake Hafslovatnet. This oligotrophic lake is the last location before the water flows into the fjords. Since the 1980s users of this lake noticed excessive growth of water plants in the lake, which began to interfere with recreational activities. There have been previous studies investigating the plant growth problem. Nonetheless the problem is still occurring to some extend nowadays. The purpose of this study was to analyse possible effects that could have caused the excessive plant growth that has been observed in Lake Hafslovatnet after the regulation of this lake and Lake Veitastrondvatnet in 1983. Therefore the following research question was formulated: Can human interference in the watershed and climate change (temperature) be the cause of the noticed increase of water plants in Lake Hafslovatnet, western Norway, since 1984? The research was realized by gathering relevant information from literature combined with the analysis of hydrological, hydrographical and own data. The focus was laid on better understanding the role of the hydrology in the plant growth problem. With the literature research data was combined into a large dataset of hydrological and chemical parameters, which has not been done before. The data was statistically analysed with a Change point analysis and a (non) seasonal Mann-Kendall trend test. With CTD measurements a better basic understanding of the present and recent hydrographic and hydrological structure of the lakes has been acquired. It shows that Lake Hafslovatnet has a two layered epilimnion when the lake is stratified. Furthermore it receives colder water at its inlet than ...
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