Large dams |


Despite these challenges, the dam began filling its reservoir in late July 2019. By April 2020, it had stored 5 billion cubic meters of water, with water levels reaching 498.2m above the river bed. The first of six generators was commissioned on May 19, 2020, marking a significant milestone in the project’s completion. The Ilısu Dam represents a major investment in


Ilisu Dam aims to develop the country’s southeastern


provinces. The dam’s structure has a height of 135m and a crest length of 1820 m. Its embankment volume is a staggering 43.8 million cubic meters, creating a reservoir with a capacity of 10.4 billion cubic meters at maximum storage. This vast reservoir covers an area of approximately 313 square kilometers when at its normal elevation of 525m above sea level. At the heart of the Ilısu project is its powerhouse, equipped with six vertical Francis turbines, each with a capacity of 200MW. These turbines, coupled with generators rated at 223 MVA, give the dam a total installed capacity of 1200MW. The power plant is designed to generate an impressive 3,833GWh of hydroelectric energy annually, operating at a gross hydraulic head of 122.6m. The dam’s spillway, crucial for flood control and water management, is located on the right bank and is controlled by eight radial gates. These gates direct water into four chutes before it reaches a plunge pool, ensuring controlled water release when necessary. To facilitate construction and river diversion,


the project included three circular diversion tunnels, each with an inner diameter of 12m and lengths varying from 897 to 1,099m. The tailrace tunnel, approximately 1,100m long with a maximum width of 143m, channels water away from the turbines. Power transmission from the Ilısu Dam is accomplished through a sophisticated system. The transformer unit includes 18 single-phase step-up transformers and one spare, converting the energy from the turbines to 380 kV. This high-voltage electricity is then transmitted to the switchyard via a 900-meter overhead transmission line. The 380kV switchyard feeds electricity to both a 380kV grid and a 154kV grid through two coupling transformers. The project incorporates modern control and monitoring systems which enables remote monitoring and predictive maintenance capabilities. This advanced technology enhances the dam’s operational efficiency and potentially extends maintenance intervals. Construction of the Ilısu Dam faced numerous challenges and controversies, particularly regarding its environmental and cultural impacts. The project necessitated the relocation of the ancient town of Hasankeyf and its historical artifacts, sparking international debate and opposition.


Lower Sesan 2 Dam, Cambodia


The Lower Sesan 2 Dam is a significant hydroelectric project located in northeastern Cambodia, situated on the Sesan River in Stung Treng Province. Commissioned in stages between 2017 and 2018, the project represents a key component of Cambodia’s energy development strategy. The dam has a length of 6.5km, making it one of the longest dams in Asia. It stands 75m high and has a crest width of 8m. The main dam is primarily an earthen structure, with a reinforced concrete section facing the river. This design allows the dam to create a vast reservoir with a storage capacity of 2.72 billion cubic meters, covering an area of approximately 33,560 hectares when at full capacity. At the heart of the Lower Sesan 2 project is its powerhouse, equipped with eight turbines, each with a capacity of 50MW, giving the dam a total installed capacity of 400MW. These turbines are designed to generate about 1,998 GWh of electricity annually, contributing nearly 20% of Cambodia’s total domestic electricity generation as of 2020. The project includes several key components


beyond the main dam structure. A rectangular span structure with dimensions of 15m x 16m and 12 gates manages water flow according to hydrological analysis. The power plant, situated on the left bank, houses the turbines and associated equipment. Additional infrastructure includes water inlets, shutter valves, a 220kV switchyard, tailrace drains, and administrative buildings.


Construction of the Lower Sesan 2 Dam


required extensive earthworks and resource extraction. The project utilized land and rock excavation sites within the reservoir area. Sand extraction occurred at two locations: one 500m


Turkey’s energy infrastructure, with a total project cost estimated at approximately €1.2 billion.


behind the dam and another on the Srepok River, more than 3km in front of the dam. The project also incorporated comprehensive waste management systems, including landfills, sewage treatment facilities, and water purification systems for worker accommodation. The dam’s development and operation are managed by Hydro Power Lower Sesan 2 Company Limited, a joint venture comprising Hydro Lancang International Energy (a subsidiary of China Huaneng Group) with a 51% stake, Royal Group of Cambodia with 39%, and Electricity Vietnam International holding the remaining 10%.


Financially, the Lower Sesan 2 project


represented a significant investment, with total costs estimated at $781 million to $978 million. This funding was secured through a combination of equity investment from the developers and financing from Chinese banks, including the Industrial and Commercial Bank of China, Bank of China, China Development Bank, and Export–Import Bank of China. The project operates under a 45-year build-


operate-transfer (BOT) agreement, which includes the initial five-year construction period. After 40 years of commercial operation, ownership will be transferred to the Cambodian government.


Alto Tâmega Dam, Portugal


The Alto Tâmega Dam is a significant hydroelectric project located on the Tâmega River in northern Portugal, forming part of the larger Tâmega Electricity-Generating Group. This impressive infrastructure is situated in the municipalities of Ribeira de Pena and Vila Pouca de Aguiar, within the Vila Real District. The dam’s structure is a marvel of engineering, classified as a concrete double curvature arch dam. It stands at a height of 106.5m and stretches 334m in length across the river valley. This design allows for efficient water retention while minimizing the amount of concrete required, making it both economical and structurally sound. The reservoir created by the Alto Tâmega Dam covers a substantial surface area of 7.4km2


This large body of water not only serves as a source for power generation but also has the potential to impact local ecosystems and provide opportunities for water management in the region.


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Lower Sesan 2 Dam 46 | September 2024 | www.waterpowermagazine.com


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