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Securing the supply   of drinking water for Tallinn

Lake Ülemiste is a shallow eutrophic lake which has been   the main reservoir of drinking water for Tallinn since the 14th century. The   water level is controlled by a Water Treatment Plant which supplies over 90%   of the inhabitants of Tallinn with drinking water (the rest of the population   is supplied from bore wells (Tallinn Environmental Strategy to 2030). The   catchment area of the lake has been enlarged from 70 km² to 1865 km² and a   complex interlinkage of reservoirs and canals has been built on the Pirita,   Jägala and Soodla rivers in order to direct water into the lake (Panksep et   al. 2009).

Lake Ülemiste is affected by water quality problems, the   main of which include its high phytoplankton biomass, which results in costly   treatment for human consumption, an accumulation of thick sediment at the   bottom of the lake that can release particulate matter during windy periods;   and contamination from the city’s airport which is located on the eastern   shore of the lake.  

The main measures taken so far by the city to protect   Tallinn’s drinking water reservoir and improve water quality have included:

•   The renewal and expansion of a sanitary   protection zone of Lake Ülemiste, completed in 2009. Considering the   importance of the surface water intake of the lake as a source of drinking   water, expanding the sanitary protection zone by more than was required under   the Water Act (i.e. 90 metres) was deemed as necessary. The sanitary   protection zone covers Lake Ülemiste, its water intake facilities, its shore   protection facilities and the close surroundings of the lake, which must be   preserved in their natural status and where the movement of people must be   restricted. The sanitary protection zone is surrounded with a fence and is   not in public use.
•   The reconstruction and extension of the shore   protection dam of Lake Ülemiste, completed between 2011 and 2012. Its goal   was to increase the adjustable volume of the shallow lake, reduce the   eutrophication of the water, stop the shore erosion caused by waves and   guarantee a service path for the management and inspection of the lake.
•   A biomanipulation project in order to control   phytoplankton biomass and therefore improve the water quality in the lake (see   detailed description in section 3.2.2).