The Iskar Reservoir is the largest reservoir in Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

. It is situated on the Iskar River and provides 2/3 of the water for the capital Sofia

Sofia

Sofia is the capital and largest city of Bulgaria and the 12th largest city in the European Union with a population of 1.27 million people. It is located in western Bulgaria, at the foot of Mount Vitosha and approximately at the centre of the Balkan Peninsula.Prehistoric settlements were excavated...

, also being used for producing hydroelectricity

Hydroelectricity

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

.

The reservoir has a total volume of 673 million m³, of which 580 million are in use and the rest is reserve. The reservoir has a drainage basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 of 1,046 km² and is 25 km long. It is situated at 820 m above sea level, its dam being 204 m long and 76 m high.

History

The initial plans for the construction of a dam on the Iskar date to as early as 1900-1901, immediately after the building of the Pancharevo Hydroelectric Power Plant. In 1921, the idea was once again brought up, but its accomplishment failed due to the municipality's inability to indemnify the residents of the neighbouring villages of Gorni Pasarel, Shishmanovo and Kalkovo. Topographic photographs and a geological assessment regarding the dam were made and observations of the Iskar's water level at Pasarel were conducted in 1932-1941 in order to build what was initially called the St Peter's Reservoir (named after the monastery in Dolni Pasarel which was supposed to be near the reservoir).

New geological research related to the reservoir's construction began in 1947 at four places between Gorni Pasarel and Pancharevo

Pancharevo

Pancharevo is a suburban district located in the south-eastern parts of the Capital Municipality. it has 26,000 inhabitants. It is the largest region in Sofia with total area of 364,7 km²...

. The place at the Iskar's 37th kilometre was chosen as the most suitable in terms of geology, topography and economics. The waters of the river were further studied between 1947 and 1948.

Work on the projects for an Iskar water power system commenced in early 1948 in the newly-established Energohidroproekt. The design and the first draft were created by a team under the engineer Moiseev with the assistance of Soviet

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

specialists. The project was approved by the expert council of the Ministry of Electrification and Melioration, and it was planned that the reservoir had a working volume of 520 million m³ and a reserve volume of 60 million m³.

The preparative works began in 1949, the main construction was carried out in the end of 1950, the water power system being officially opened on 6 September 1954.