Geografie 2004, 109, 129-144

Influence of Hydrological Conditions on the Ecological State of Shallow Lake Vörtsjärv

Arvo Järvet

University of Tartu, Department of Geography, Vanemuise 46, 51014 Tartu, Estonia

Lake Vörtsjärv as a very shallow (mean depth 2.8 m) water-body and considerable water level fluctuations cause changes in both the surface area and volume of the lake. Due to the shallowness of the lake, low level periods are accompanied by several phenomena detrimental to its ecosystem, like cyanophyte blooms, overgrowing with macrophytes, resuspension of phosphorous compounds, restricted spawning places for pike and winter fish kills. In the years of low water level the perspectives to catch in established fishing sites using particular gear as well as access to harbours are hindered. Causal relations between the water regime and ecological state of the lake Vörtsjärv have been discussed in this paper.