Terasmaa, J., Raukas, A., Vaasma, T., Tavast, E.
Sedimentation dynamics in the littoral zone of Lake PeipsiAbstract
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.