Belmeken junction The highest section of the cascade includes three gathering derivations covering a total area of 219 km2 that catch waters from the drainage basins of the Maritsa (45%), the Mesta (32%) and the Struma (23%). These are the
Granchar derivation that gathers water from the upper courses of Mesta's right tributaries — the Cherna Mesta, the Bela Mesta and the Belishka reka, as well as from left tributaries of the Struma, including the
Blagoevgradska Bistritsa, the
Rilska River; the
Dzaferitsa derivation that gathers water from left tributaries of the Mesta and the Chairska reka; and the
Maritsa 1900 derivation that catches water from the Maritsa drainage. The
Granchar derivation is connected via a 2.8 m reverse tunnel to the Iskar cascade that includes the
Iskar Reservoir, which is the main water supplier of the capital
Sofia. Between 1983 and 2000 via that tunnel water from the Belmeken–Sestrimo–Chaira Cascade was diverted to ensure additional supply for Sofia. The system of derivations feeds the
Belmeken Reservoir situated at an altitude of 1,923 m on the upper course of Kriva reka, a right tributary of the Maritsa. It was constructed in 1964–1974 and serves as the main accumulating and regulating facility of the cascade. The reservoir is linked to the
Belmeken Pumping Storage Hydro Power Plant via a pressure derivation with a length of 5.2 km. It was completed in 1975 and is powered by water falling from a height of 737 m. The power station is equipped with five
Pelton turbines, two of which may also pump water, with a total installed capacity of 375 MW and an average annual production of 321 GWh. The
Chaira Pumped Storage Hydro Power Plant has an electricity generation capacity of 864 MW and a pumping capacity of 788 MW, making it the largest pumped storage plant in Southeastern Europe. The upper leveler of the plant is the Belmeken Reservoir, to which it is connected via two 1.7 km pressure pipelines. The geodetic drop to the lower leveler, the Chaira Reservoir, is 689 m. The machine and transformer rooms are located 350 m underground in specially constructed caverns. The plant has four reversible units with
Francis turbines with a capacity of 216 MW each, generating an average of 422 GWh annually.
Chaira–Stankovi Baraki junction The second level of gathering derivations is situated at an altitude of 1,200 m and encompasses a total territory of 238 km2. Part of the accumulated water is pumped upstream to the Belmeken Reservoir and the rest is utilized at the power stations downstream. There are three derivations — the
Maritsa 1200 derivation that catches water from the Maritsa drainage, the
Chairska derivation that gathers water from the Chairska reka; and the
Yadenitsa derivation that gathers water from the river
Yadenitsa, a right tributary of the Maritsa. A third reservoir, Yadenitsa, is planned to be linked with the Chaira and Stankovi Baraki Reservoirs, in order to increase the leveling and cumulative capacity of the Chaira and Belmeken PSHPPs. Its dam is planned to reach a height of 109.2 m and a length of 315 m and will form a lake with a volume of 14.2 million m3. It will be connected with the Chaira Reservoir via a 6.8 km reverse tunnel. Construction began in 1997 but stalled in 2005 due to lack of funds. The
Sestrimo Hydro Power Plant is situated near the village of
Sestrimo and was inaugurated in 1973. It is a derivation power plant, linked with the Stankovi Baraki Reservoir via a pressure derivation with a length of 4.9 km and an average water fall of 534 m. The plant has two Pelton turbines with a total installed capacity of 240 MW, generating an average of 291 GWh annually.
Momina Klisura junction The lowest junction includes the
Momina Klisura Hydro Power Plant and its related facilities. The power plant was put into operation in 1975. It has two Francis turbines with a total installed capacity of 120 MW, generating an average of 136 GWh annually and using water discharge of 56.6million m3/s. The power plant is driven by the processed water from the Sestrimo HPP. The open channel for the outflow water empties into a leveler with a volume of 200 thousand m3 From there, the water reaches the Momina Klisura HPP through a 1.2 km pressure pipeline with a diameter between 4.0 and 3.1 m. The processed water is transferred to a small lower leveler and then diverted through a 75 m non-pressurized derivation to the
Pyasachnik Reservoir to be utilized for irrigation in the
Upper Thracian Plain. == See also ==