Water colour trends in Lake Mälaren

• Main Author: Tilja, Marie
• Format: Others
• Language: English
• Published: Linköpings universitet, Institutionen för tematisk utbildning och forskning 2003
• Subjects: Interdisciplinary studies; Water colour; Absorbance; Discharge; Lake Mälaren; Trend; Trend analysis; TVÄRVETENSKAP; Social Sciences Interdisciplinary; Tvärvetenskapliga studier inom samhällsvetenskap
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2199

The aim of this thesis was to determine whether there has been a trend of increasing or decreasing water colour, absorbance, in Lake Mälaren during the last 35 years and whether it could be correlated with water discharge. The discharge was accounted for using regression analysis. The data material was analyzed for trends using a nonparametric test, the so-called seasonal Mann- Kendall test. The regression model could only account for a small (maximum of 24%) variation due to discharge. Thisindicates that discharge single-handedly can not explain the variation in absorbance. The trend analysis indicated a significant yearly increase in absorbance of 0.93% - 2.43% yr-1 for three out of four investigated sub-basins, namely, Galten, Ekoln and Skarven. This strongly implies that there has been an increase of absorbance and a change in the amount of organic material in Lake Mälaren during the last 35 years.