Cahora Bassa

Cahora Bassa is a massive artificial lake located in Mozambique. It sits within the Tete Province on the Zambezi River. This lake is the fourth-largest man-made lake in Africa by surface water. Only Lake Volta in Ghana, Lake Kariba on the Zambezi, and Lake Nasser in Egypt are larger.

The lake was created by a large dam designed for hydroelectricity. This means the moving water turns turbines to generate electrical power.

The primary purpose of the Cahora Bassa system is power generation. Most of the electricity produced is sold to South Africa. To move this power, engineers use a high-voltage direct current (HVDC) transmission system. HVDC is a method of sending electricity over very long distances with less loss. In 1994, hydroelectricity provided 91% of Mozambique's total 2,400 MW of installed capacity. In 2006, the system transmitted about 1,920 megawatts of power. The infrastructure was designed to potentially double this output.

The history of the project began in the late 1960s. At that time, Portugal controlled Mozambique as an overseas province. The project involved complex agreements between Portugal and Southern African governments. South Africa agreed to build the Apollo converter station near Pretoria. This station helped manage the electricity arriving from the Mozambican border. During the struggle for independence, Frelimo guerrillas attacked construction materials. They did this to stop the dam's completion. A larger lake would make the river too wide to cross in canoes.

Ownership of the dam changed significantly over many decades. Until November 2007, the company Hidroeléctrica de Cahora Bassa (HCB) was mostly Portuguese-owned. Portugal held an 82% stake, while Mozambique held 18%. A long dispute existed between the two nations regarding US$2.2 billion in debt. In 2007, Mozambique assumed control after Portugal sold most of its stake. This sale brought Portugal approximately US$950 million. Prime Minister José Sócrates signed the agreement during a visit to Maputo.

The dam and its power lines have faced many physical challenges. During the Mozambican Civil War, guerrillas sabotaged the transmission lines. Workers had to replace 1,895 towers and refurbish 2,311 others over 893 km. This work was difficult because the terrain was filled with landmines. In 1978, a massive flood caused 45 deaths and displaced 100,000 people. This event proved that the dam could not fully control all natural flooding. Later, in February 2000, heavy rains in the Limpopo River valley collapsed 10 towers.

The lake has also created unique environments for wildlife. Since 2005, the area has been recognized as a Lion Conservation Unit. The water supports a large fishery for a fish called kapenta. It is believed these fish originally came from Lake Tanganyika via Lake Kariba. In 2003, the annual catch of kapenta exceeded 10,000 tonnes. There are also local reports of bull sharks living in the reservoir. Bull sharks are ocean-dwelling species that can live in fresh water for their entire lives.

Cahora Bassa remains a vital part of the region's energy and ecology. It connects the natural power of the Zambezi River to the needs of modern industry. The system links the geography of Mozambique directly to the energy demands of South Africa. While it provides power, it also requires constant management of the river's flow. The dam stands as a major example of how humans reshape the Earth to harness energy.