Epsilon Archive for Student Projects

Abstract

Forestry is one of the main economical activities in Sweden, but it can seriously affect the dynamic of the water cycle by altering several hydrological factors such as timing and amount of snow melt and meltwater contributions from the snowpack to the soil.

This thesis, performed during the spring 2010 within the “Balsjö Catchment Study” in Northern Sweden, was carried out in order to understand how forest cover can influence the hydrology of snow-dominated boreal catchments. The experiment was setup in two different sub-watersheds, one forested and one open (harvested by clear-cutting in 2006), within the same watershed.
Snow accumulation was found to increase 5% in the clearcut than under forest cover. Moreover, a dataset collected from different surveys carried out from 2005 to 2009 showed that snow accumulation was 20% higher in average in the open areas than forests, so that the difference between both areas in 2010 was comparably low. Snowpack reduction was faster and more constant in the clearcut, whereas the snowpack followed a more stable development in the forest, where the reduction was mostly concentrated in the last two weeks before total disappearance of snow. Meltwater contributions from the snowpack to the soil were 43% higher in the forest than the clearcut. However, calculations showed that evaporative loss from the snowpack was 44% higher in clearcut than the forested area. Therefore, the amount of meltwater released was higher (34%) than evaporative loss under canopy. The clearcut showed an opposing behavior; evaporative loss played a more important role (50% higher) than the amount of meltwater which was released.
According to the results obtained in this study, snowpack reduction and snowmelt were delayed by approximately one week in the forested area relative to the clearcut as a result of the influence of the canopy. Forest cover also increased meltwater contributions from the snowpack to the soil and decreased evaporative loss from the snowpack, playing a crucial role at controlling the water balance.