The Iskar Reservoir (язовир „Искър“) is the largest

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

Bulgaria Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is situated on the eastern portion of the Balkans directly south of the Danube river and west of the Black Sea. Bulgaria is bordered by Greece and Turkey t ...

. Situated on the Iskar River, it provides two-third of the water for the capital

Sofia Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

, and also produces

hydroelectricity Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

. 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 A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

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 Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

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 survey related to the reservoir's construction began in 1947 at four places between Gorni Pasarel and Pancharevo. 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 The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

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. Preparatory 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. When it was under construction, its name was changed to "Giant-Reservoir Stalin" (Гигант язовир Сталин), but later its name was returned to "Iskar Reservoir". There is also the Beli Iskar Reservoir, which is another smaller dam and is located in the upper reaches of the Iskar River.For Iskar - the largest dam in Bulgaria
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References

* *{{cite web, url=https://www.moew.government.bg/static/media/ups/tiny/filebase/Water/Povarhnostnivodi/Mesechen_grafik/2020/graf_1_20.pdf , title=MOEW government: Ministry of Environment and Water, language=Bulgarian, date=January 2020 Reservoirs in Bulgaria Landforms of Sofia City Province Samokov Municipality