Žuvintas Biosphere Reserve is situated in the South of the middle Lithuania lowlands, on the border of Nemunas middle-reaches and Neris lower-reaches plain, on the borderline of the south-eastern physical-geographic district. It comprises a complex of Žuvintas and Amalvas wetlands, wet Bukta forest and Žaltytis Lake together with its marshy coastal territories, situated to the west of Žuvintas Lake.
Žuvintas mire complex is composed of a shallow overgrown Žuvintas Lake and a marshland stretching to the west, southwest and north from it, which was formed from 5,5 times larger waterlogged lake a long time ago. The entire site is located in a depression of the oval limnoglacial swampy plain, formed during the Glacial period, which is surrounded by the flat downy ridges and stretched relief from all sides round. Žuvintas mire complex is the largest in Lithuania, composed of two raised bogs, transitional mires, sedge fens, wet overgrown meadows and forests along with a shallow lake comprise a general area of 6850 ha. The thickest peat layer of Žuvintas raised bog reach up to 8,1 meters. The northern part of this mire complex (fens) was drained and transformed into the meadows. Considerable areas of these sedge fens cover around 1125 ha.
To the north of Žuvintas Lake lies analogous, but smaller in size Amalvas wetland , which is composed of Amalvas Lake with adjacent fens. Amalvas mire complex covers 3400 ha area, and has suffered greatly from the anthropogenic activities, i.e. intensive drainage of entire fen and part of the raised bog, introduced water level regulation. The medium thickness of the peat in the raised bog reach up to 5,6 meters depth.
WATER BODIES. Almost all territory of Biosphere Reserve lies in the Dovinė River catchment area (the right side of Šešupė river influent). There are 3 lakes situated in the territory of Žuvintas biosphere reserve: Žuvintas, Žaltytis and Amalvas, as well as several smaller marshy lakes within Žuvintas mire.
Area of Žuvintas Lake is 965 ha, average depth – 0,6 m, the maximum seat - 3 m. Žuvintas is a typical overgrown and quite shallow lake – the medium thickness of the peat layer reach up to 4 meters.
Area of Amalvas Lake - approximately 190 ha, average depth – 1 m, the maximum seat - 2,9 m. It is surrounded from all sides by mire Amalvas, except the eastern side. Šlavanta stream falls into the Lake and Amalvė stream (tributary of Dovinė) outflows from it.
Area of Žaltytis lake - 289 ha, from which open water - 225 ha, the deepest site - 4,1 m, average depth - 1,7 m.
CLIMATE. Žuvintas Biosphere Reserve lays in the Middle Lowlands climate region, sub-region of Nemunas lower-reaches. It is characterized as one of the warmest site of Lithuania: the average annual temperature exceeds +17,5oC in July, - 4,7oC in January. Annual precipitation is relatively low – up to 600 mm, ¾ of which–during the warm season. The average snow layer (around 15 cm) last approximately 70 days.
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