Terasmaa, J., Raukas, A., Vaasma, T., Tavast, E.
Sedimentation dynamics in the littoral zone of Lake Peipsi
Bottom sediments of Lake Peipsi proper were mapped in the
1970s’ from the research vessel but for technical reasons near shore areas were
not investigated. The present work is the first attempt to fill this gap. Based
on the surface sediment mapping of the whole lake basin, we identified 11 key
areas of the littoral zone and provided a detailed survey of the sediments. By
the grain-size, the surface sediment samples can be separated into three
groups: coarse-grained (predominantly sands in the near shore areas and in the
southern part of the lake), fine-grained (mainly silts) and clayey sands, both
in the central deeper part of the lake within the 8 m depth contour. Because of
a complicated system of currents, the granulometry of deposits shows distinct
spatial distribution. Long-term observations have shown that the water level in
Lake Peipsi changes cyclically, i.e. years with a low water level alternate
with years with a high water level. This phenomenon causes fast erosion in some
years and exuberant growth of reed and bulrush and accumulation of fine
material in the coastal zone in other years. Water-level fluctuations affect
the sediment characteristics and aquatic vegetation assemblages and have
influence on the land use, fishery and recreation.