Morphometry and Hydrology of the Four Large Lakes of Sweden

Abstract

The four largest Swedish lakes Vänern, Vättern, Mälaren and Hjälmaren all have a tectonic origin with multidirectional fault fissures, which influence the topography of the bottoms and the creation of subbasins. All the four lakes have been subject to several glacials, the latest of which started to recede from central Sweden c. 10,000 years ago. The many differences between the four lakes can be explained by their shapes, sizes and the relation between the sizes of the drainage basins and the size of the lakes. This paper focuses on processes considered relevant to aquatic organisms of the lakes: water balance, water residence time, water temperature, water exchange between subbasins within the lakes, and other internal water movements. Links between pollution, water exchange and retention of nutrients are discussed with an example from Lake Vänern.

Overwintering dormancy behaviour of the European eel (Anguilla anguilla L.) in a large lake

“…The geography of the lake is complex, Fig. , with subbasins and numerous smaller bays (Kvarnäs ). There are more than 7000 islands larger than 1 ha.…”

“…The depth of the thermocline increases from approximately 5 m in May to 12–15 m in June–August. The lake is dimictic, but the temperature difference between the surface and bottom water is usually <1 degree after the autumn overturning and during the winter period (Kvarnäs ; Sonesten ). The oxygen content in the bottom water has a minimum in August before the autumn overturning and varies between basins and years.…”

Characterization of algal and microbial community growth in a wastewater treating batch photo-bioreactor inoculated with lake water

“…Wastewater for the experimental system was collected from the WWTP 127 inflow (from the top layer of the centre of the mixed basin). 128 Lake water for algae inoculation was taken from Lake Mälaren, which has an area of 129 1096 km², a mean depth of 12.8 m and a maximum depth of 64 m. It is the third largest 130 lake in Sweden, with a water volume of 14 km 3 (Kvarnäs, 2001). Mälaren lake water was 131 collected from a yacht harbour next to the WWTP from the upper layer (0.5 m) of the 132 lake.…”

Geothermal evidence for groundwater flow through Quaternary sediments overlying bedrock aquifers below Lake Vättern, Sweden

“…Lake Vättern is the second largest lake in Sweden and the sixth largest in Europe in terms of area (1,856 km 2 ) and volume (74 km 3 ; Kvärnas 2001) (Fig. 1).…”

“…1B). Kvärnas (2001) summarized the water balance for the lake, with 612 mm/yr (or 1.14 km 3 /yr) of freshwater input, of which 510 mm/yr (0.95 km 3 / yr) is in the form of precipitation. Annual output amounts to 680 mm/yr (1.26 km 3 /yr), with 442 mm/yr (0.82 km 3 /yr) of evaporation.…”