Water Supply and Drainage Company - Sofia

“Water Supply and Drainage Company-Sofia” specialises in exploitation, maintenance thorough repair and reconstruction of the water supply and drainage systems, improvement of river beds and their necessary equipment, all these being situated within the territory of Sofia. It also deals with the water catchments, Beli Iskar reservoir and the systems leading to Sofia.

The company provides:

• Normal water supply with drinking water and water for the needs of industry;
• Drainage of the city territory;
• Protection of waters of the Iskar river against pollution.

Water Supply System

The construction of the water supply system started at the end of the last century. The year of 1884 is considered to have marked the beginning, when a project for the water supply of Sofia with waters from Vitosha Mountain was worked out.

The water supply of Sofia is conducted through three main water sources:

• Controlled waters in the Beli Iskar reservoir and river catchments of the Iskar river and its tributaries – 9 in number. The average capacity is 1500 litres/sec;
• Controlled waters from the Iskar reservoir – 6500 litres/sec;
• River catchments, coming from Vitosha Mountain – 5 in number. The average annual capacity varies from 130 to 300 litre/sec.

The water catchments carry water into the Rila water main, and the water from the other two catchments are brought to the city by another water main.

The Beli Iskar reservoir was built to meet the needs of water supply with a volume of 15.3 million cubic metres.

The Iskar reservoir was also built to satisfy the complex needs of water supply, irrigation and energetics. The total volume of the Iskar reservoir is 655.3 million cubic metres, and the useful volume – 558.1 million cubic metres.

The rivers of the Iskar river and pancharevo bent are used to meet the industrial demands for water. Kokalyane bent has a capacity of 2.7 million cubic metres, while Pancharevo bent has 6.4 million cubic metres.

The technical characteristics of the water supply network and equipment:

• Water mains brought along from outside sources – 80 km;
• Water mains – 256 km;
• Street water supply network – 2400 km
• 14 tanks for central water supply – 331,700 cubic metres;
• 37 tanks for local water supply – 7600 cubic metres;
• 20 pumping stations with a capacity of 4170 litres/sec

Drainage

The construction of the drainage system in Sofia started at the end of the last century. The configuration of the city territory, with its 5 flowing rivers, provides the opportunity for the construction of a mixed drainage system.

The major drainage collectors follow roadbed parallel to the rivers and collect and lead the gravitational residue waters away from the city drainage network. Two leading collectors to “Kubratovo” Wastewater Treatment plant direct the doubly diluted waters.

Technical characteristics of the drainage network:

• total length of the drainage network – 1370 km;
• drainage deviations – 33,000 in number;
• street effluents – 80,000 in number
• corrected river sections – 28,323 km.