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Physical Characteristic of Srebarna Reserve

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The lake of Srebarna, situated in North-Eastern Bulgaria on the right bank of the Danube (440 05’’ n.l. and 270 07’’ e.l.) between the river kilometres 393 and 391, is located in a karstic depletion surrounded by three hills. The total territory of the Srebarna Biosphere Reserve is 902.1 ha including the shallow holo-polymictic Srebarna Lake with slightly alkaline to neutral waters and the Danubian island Devnia. The watershed basin covers area of 1,070 km2 and is formed of the basins of the rivulets Srebrenska, Babukska and Kalnezha (MODEV, 1994).

A hyper-eutrophic lake, the Nature Reserve, is exclusive state property, and the adjoining land tracts are private property or municipal property. Commercial fishing and mowing of Reed, Reedmace and Bulrush in the Reserve was discontinued in 1975. Since then, the natural resources have not been exploited.

The lake bowl lies in the Pliocene clays over a substratum of Barremian and Aptian limestones. In 1949 the lake was disconnected from the Danube by a dyke, and since then ground water sources and surface run-off from the neighbouring hills have remained the only source recharging the lake with fresh water. The connection with the Danube was partially re-established in 1978, but river waters do not flood the lake every year. The lack of an adequate connection with the Danube for long periods of time creates conditions for accretion of bottom sediments (organic and inorganic sludge), reducing the water depth to only 1 m (measured in 1993). A canal connecting the Danube with the lake, built in 1994 with the financial support of international organizations, has improved substantially the ecological conditions in the lake. The abundance and diversity of bird species typical of the region is increasing.

Water level of Srebarna Lake

The climate in the region is continental with a temperature varying between -15 0C (in January) and 39 0C (in July). The average annual number of days with temperature >25 0C is 25 and for the days with temperature <0 0C it is 20. Annual precipitation average is 159 mm. The relative air humidity is highest in January (84%) and lowest in July and in August (66%). The average annual humidity is 75%. The evaporation from the lake surface has not been studied, and the count-speculative data, which appeared in the hydrological works varied significantly from 700 to 1000 mm. The predominant winds are with northern and north-eastern direction with average monthly speed ranging between 1.7 and 5.8 m s-1. The annual average number of days with strong wind (V .> 14 m s-1) is 10.4 and 5.4 of them are during the winter months (MODEV, 1994). The number of days with snow and ice cover vary between 40 and 60.

Created by nevena
Last modified 04.03.2008 16:55
 

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