Vorotan Cascade

The Vorotan Cascade, or the ContourGlobal Hydro Cascade, is a cascade on the Vorotan River in Syunik Province, Armenia. It was built to produce hydroelectric power and provide irrigation water. The Vorotan Cascade consists of three hydroelectric power plants and five reservoirs with a combined installed capacity of 404.2 MW. It is one of the main power generation complexes in Armenia.

History
The planning process of the Cascade began just after the Conference of the State Planning Commission held in 1951. In 1954, it was highlighted that with proper infrastructure and careful planning, Armenia's energetic hydro resources might allow it to become an electricity exporter to neighbouring energy deficit areas like Azerbaijan and Iran. It was anticipated that the activation of the Cascade would cut the import of oil products to the country by half. The design work of the Complex began in 1954 and it was constructed between 1961 and 1989. The Tatev hydroelectric power plant (HPP) was completed in December 1970, the Shamb HPP in 1978, and the Spandaryan HPP] in 1989. Despite the plans, Azerbaijan was against the import of electricity from Armenia, thus hindering the scheduled renovation and capacity expansion to take place at the end of the 1970s. The Vorotan Cascade continued to supply electricity mainly to non-ferrous metallurgy industry in nearby Agarak.

After Armenia gained independence, the Voratan Cascade belonged to the state-owned energy company Armenergo. In 1997, the Vorotan cascade was separated from Armenergo into a separate state owned company.

Modernization of the cascade started in 2003 by help of the €2.7 million grant of the European Union which was used for rehabilitation of the Tatev HPP of the Vorotan Cascade, and the Argel HPP. Rehabilitation works were conducted by Voith Siemens Hydro Power Generation. Next rehabilitation project was launched in 2010, financed by the €51 million credit from the German development bank KfW. Rehabilitation works started in 2012.

In 2015, ContourGlobal purchased the Vorotan Cascade operating company for US$180 million. ContourGlobal has started a six-year refurbishment program to modernize the plants and improve their operational performance, as well as safety, reliability, and efficiency, with the total investment of $70 million. This is the biggest investment US investment in Armenia. The International Finance Corporation, a member of the World Bank Group, did 20% of the total investment.

Specifications
The Vorotan River has length of 178 km, the fall of 1223 m, and the natural annual flow of 18.6 m3/s for the link of Tatev. The source of the river is on 3045 m of the height and starts like a stream, accepting numerous ponds and streams.

The Vorotan Cascade includes a system of three power plants which are Spandaryan, Shamb and Tatev, and five reservoirs which are Spandaryan, Angeghakot, Tolors, Tatev and a daily regulation reservoir. The Spandaryan Reservoir in the vicinity of Tsghuk and Gorhayq villages, is the starting point of the complex. From there water flows through a pressurized tunnel to the Spandaryan HPP. From the Spandaryan HPP water flows to the Angeghakot Reservoir and continues its journey to the Tolors Reservoir which is located in the area of Sisian and Ayri. From that reservoir the water flows to the Shamb HPP. From Shamb reservoir that was constructed beyond the Shamb HPP water reaches the regulation pool, from where it proceeds to the Tatev HPP via a turbine pipe.

The Vorotan Cascade is one of the main power generation complexes in Armenia. It provides both peak and base load power. It is used also for the grid stabilization. The Tatev HPP has installed capacity of 157.2 MW, the Shamb HPP has installed capacity of 171 MW, and the Spandaryan HPP has installed capacity of 76 MW. Total installed capacity of Vorotan Cascade is 404.2 MW and it generates 1.16 GWh of electricity annually.

The water stores of the Vorotan Complex are also used for irrigation in nearby village and town areas.

Tatev HPP
The Tatev HPP is located near the Vorotan village on the left bank of the Vorotan River at the altitude of 730 m. It is one of Armenia's largest hydroelectric power plants, with installed capacity of 157.2 MW and annual generation of 670 GWh. Power is generated by three Pelton turbines of 52.4 MW each. The plant is unique has it is the highest-head hydroelectric power plant in the territory of the former Soviet Union and by using Pelton turbines.

The plant includes the Tatev Dam which is a 41 m high and 107 m embankment type dam of sandy gravel. It includes also the daily regulation reservoir. The dam creates the Tatev Reservoir.

The water intake on the left bank of the Vorotan River has capacity of 25 m3/s and the spillway has total capacity of 312 m3/s. Water runs from the water intake through the 18 km long free-flow diversion tunnel to the delivery chamber. The 139.4 m long and 4 m high tail-water canal is connected with an irrigation water outlet. The pressure chamber has a diameter of 20 m and the threshold level of 1293.05 m. It is connected to the plant by a 1855 m pressure conduit, and to the 80000 m3 daily regulation reservoir by the sluice-feeder. The rated head of the plant is 568.8 m.

Shamb HPP
The Shamb HPP is located near the village of Shamb on the right bank of the Vorotan River at the altitude of 1328 m. It is one of the largest hydroelectric power plant having an installed capacity of 171 MW and annual generation of 320 GWh.

Shamb HPP includes the Angeghakot and Tolors dams which create the Angeghakot and Tolors reservoirs. The Angeghakot Dam is a 23.4 m high concrete spillway dam. The Tolors Dam is a 69 m high and 188 m long embankment type dam of sandy gravel and soil. The Angeghakot and Tolors reservoirs are connected by a 10.5 km free-flow tunnel which has throughput capacity of 23 m3/s. Water runs from the Tolors Reservoir to the plant through a 6.9 km diversion pressure tunnel which turns into a 1260 m single-lane penstock.

Spandaryan HPP
The Spandaryan HPP is located near Shaghat at the altitude of 1694 m. It is the upper hydroelectric power plant on the cascade commissioned in 1989. The plant has an installed capacity of 76 MW and a projected annual electricity generation of 210 GWh.

The Spandaryan Dam creates the cascade's upper reservoir, the Spandaryan Reservoir. The 83 m high and 315 m long Spandaryan dam is an embankment type, mixed rockfill and earthfill with clayey soiled bottom.

Its water intake infrastructures includes a pressure tunnel, a spillway culvert, and the Vorotan–Arpa tunnel for releasing water into Lake Sevan. The structures have 30.5 m3/s, 80 m3/s and 15 m3/s water outlays respectively. The last, the fourth structure is a surface spillway with a 160 m3/s installed capacity and inclining drop. The pressure tunnel is 8.2 km long and it ends with a surge tank with capacity of 1900 m3. The surge tank is connected to plant by 2168 m penstock.

Spandaryan Reservoir


Spandaryan Reservoir is located southeast of Gorayk, in Spandaryan in the Vorotan River basin. It is connected to Arpa River and Arpa River basin by a 9 mi long tunnel. It reportedly has a breeding colony of lesser kestrels, the only known in Armenia.

The reservoir's length is 7 km, its width varies from 2.5 to 3 km, and its depth is 73 m.  The surface area of the reservoir is 10.8 km2. It has 218000000 m3 active and 257000000 m3 total capacities. The normal elevation of water level is 2060 m while 2030 m is the absolute minimum.

Angeghakot Reservoir
The Angeghakot Reservoir has 3400000 m3 of total capacity. The reservoir has throughput capacity of 500000 m3/s and the spillway has capacity of 198 m3/s.

Tolors reservoir
The Tolors Reservoir has a total capacity of 96000000 m3 and active capacity of 80000000 m3. The normal elevation of water level is 1651.1 m while 1625.5 m is the minimum.

Tatev Reservoir
The Tatev Reservoir has total capacity of 13600000 m3 and active capacity of 1800000 m3. The normal elevation of water level is 1335.4 m while 1333.8 m is the minimum.