ICOLD 76th Annual Meeting: Focus on Dam Operations

By Dimiter N. Toshev and Christo B. Abadjiev

Members of the International Commission on Large Dams meet in June in Sofia, Bulgaria, for the organization’s annual event. In addition to its business meeting, ICOLD will focus on the topic of dam operations during five days of meetings, a symposium, and visits to dam sites.

On June 2-6, 2008, members of the International Commission on Large Dams (ICOLD) convene in Sofia, Bulgaria, to exchange information about dam operations.

In Bulgaria, the host country for the ICOLD 76th Annual Meeting, 216 large dams (higher than 15 meters) and more than 2,200 small dams impound water for irrigation, electricity generation, and water supply.

Exchanging technicalinformation

Opportunities to exchange and disseminate technical information at the ICOLD 76th annual meeting include:

  • Exhibition of dam-related services and products;
  • Meetings of ICOLD’s 24 technical committees;
  • Symposium on “Operation, Rehabilitation and Upgrading of Dams;”
  • One-day tour of the Tsankov Kamak, Vacha, and Krichim dams;
  • 76th ICOLD Executive Meeting; and
  • Technical tours of several dams and hydro facilities.



The exhibition of products and services is open Monday, June 2, through Wednesday, June 4. The exhibition is an opportunity to network with engineers, professionals, organizations, and companies connected with the design, maintenance, and management of dams. Products and services to be showcased during the technical exhibition include water resources management, construction, maintenance, engineering, power plant design, and project finance.

Technical committee meetings

ICOLD’s 24 technical committees meet Tuesday, June 3. At these meetings, dam professionals discuss various topics that could lead to the publication of future specialized technical bulletins. (See page 14.)


Wednesday, June 4, features a symposium on operations. The theme is “Operation, Rehabilitation, and Upgrading of Dams — Problems with Dams Emerged during Operation.” More than 200 papers submitted for the symposium focus on ten areas:

  • Case histories detailing experiences with dam operation;
  • Problems with dam operation (floods, earthquakes, foundations, seepage, internal erosion, aging, deterioration of materials);
  • The role of dams in water resources and hydropower management for sustainable development;
  • The role of dams in flood mitigation;
  • Dam monitoring;
  • New trends and technologies in dam surveillance and monitoring;
  • Safety analysis;
  • Rehabilitation of dams;
  • Upgrading of dams, including new safety requirements; and
  • Adapting dam operating procedures to meet new social, economic, and environmental requirements.


One-day technical tour

Thursday, June 5, features a technical tour of the Tsankov Kamak, Vacha, and Krichim dams on the Vacha River. Tsankov Kamak, a 130.5-meter-high double curvature arch dam, is currently under construction. The dam will impound water for an 80-mw hydro plant. The 145-meter-high concrete Vacha Dam, the tallest dam in the country, impounds water for the 160-mw Orphey pumped-storage plant. And Krichim, the final dam on the tour, is a 105-meter-high concrete dam with an 80-mw power plant.

Executive meeting

Friday, June 6, is the 76th ICOLD Executive Meeting, at which the 88 member countries of ICOLD develop the policies and processes to be implemented over the next few years.

Multi-day technical tours

Beginning Saturday, June 7, delegates can take part in multi-day technical tours.

There are more than 100 hydroelectric power plants in Bulgaria, with total installed capacity of 2,870 mw.
Click here to enlarge image

Tour 1, June 7-8, starts with Diakovo Dam, a 57-meter-high earthfill dam with upstream slope protection of concrete plates with artificial roughness. Next on the tour are three dams in the Belmeken-Sestrimo cascade. The first is a 98-meter-high rockfill dam with a clay core that impounds the highest reservoir of the cascade. The reservoir, at almost 2,000 meters elevation, impounds water for the 375-mw Belmeken pumped-storage plant. This reservoir also is the upper reservoir for the 864-mw Chaira pumped-storage plant. With a head of 701 meters and a flow rate of 7.5 cubic meters per second per unit in the pumping mode, this plant features the second largest turbine-generating units in the world. The 85-meter-high concrete Chaira dam impounds the lower reservoir for the Chaira pumped-storage plant.

The next dam is Stankovi Baraki, a rockfill dam that impounds the lower reservoir for the Belmeken pumped-storage plant, as well as the reservoir for the 240-mw Sestrimo plant. The tour, through the beautiful Rila and Rodope mountains, includes the famous Rila monastery.

Tour 2, June 7-8, begins with the upper part of the three-plant 17.6-mw Petrohan hydropower cascade. The next dam visited is Srechenska Bara, a 51-meter-high earthen dam. The final dam is Ogosta, which sits on a karst foundation that caused serious problems and complicated the cross section of the dam. The tour crosses the Balkan mountains twice and includes Magura, a cave containing 12,000-year-old paintings.

Tour 3, June 7-11, starts with the 44-meter-high rockfill dam Koprinka, which impounds water for a 7-mw hydro plant. The next dams on the visit include Jrebchevo, a 53-meter-high earthfill dam that impounds water for a 14.4-mw hydro plant, and Kamchia, an 80-meter-high rockfill dam with clay core. This tour, through the Valley of Roses, includes a visit to a royal Thracian tomb with wonderful murals. From there, attendees visit two resorts on the Black Sea. Attendees can choose to spend more time at these resorts or travel back to Sofia through the ancient capital Veliko Tarnovo. Those returning to Sofia will visit Alexander Stamboliiski Dam.

Water resources in Bulgaria

Bulgaria, in southeastern Europe on the Balkan Peninsula, is relatively small at 11,000 square kilometers and a population of 8 million. The country’s water resources are concentrated in the mountainous regions. To more efficiently use and better manage the limited resources, significant construction of hydraulic structures took place in Bulgaria in the second half of the 20th century. The country has more 216 large dams, more than 2,200 small dams, and 42 large tailings dams. The majority of these large dams (45 percent) were built in the 1960s. However, only one third of Bulgaria’s technically feasible hydropower potential has been developed so far.


Hydro project construction in the country began with the 6-mw Pancharevo plant, which was completed in 1896. Bulgaria now has nine large hydropower cascades, with more than 100 conventional hydroelectric power plants and four pumped-storage power stations. Total installed capacity of the hydro plants is 2,870 mw.

Hydro construction in Bulgaria slowed in the 1990s because of a change in the country’s economic system. Owing to financial difficulties in the 1990s, construction of 14 large dams was halted. Work will resume on three of these dams in 2008.

Mr. Toshev may be reached at University of Architecture and Civil Engineering, Mladost 2 Complex, B1. 235, Apt. 36, Sofia 1799 Bulgaria; (359) 2-8668287; E-mail: d_toshev_ fhe@uacg.bg. Mr. Abadjiev may be reached at University of Architecture and Civil Engineering, 3 Dospat Street, Sofia 1606 Bulgaria; (359) 2-547764; E-mail: cbabadjiev@pc-link.net.

Dimiter Toshev is chairman of the Bulgarian National Committee on Large Dams (BUNCOLD), which is organizing the 76th annual meeting of the International Commission on Large Dams. Christo Abadjiev is coordinator of the meeting.

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