The Zambezi River is the fourth-largest waterway in Africa and the largest river system flowing into the Indian Ocean. Although the Cahora Bassa Dam and reservoir are entirely inside Mozambique, the vast bulk of its drainage basin lies outside the country. “Rising in Angola it has a catchment area of 1,570,000 [square kilometers], drains the southern borders of the Democratic Republic of Congo (DRC) and traverses Botswana, Zambia, Zimbabwe, Tanzania, Malawi and Moçambique.”2Because Mozambique is furthest downstream, it depends on its neighbors for access to the Zambezi’s waters.

      Before the Zambezi or any of its tributaries were dammed by the Europeans in the twentieth century, the rate of the river’s flow varied considerably in the catchment area. In much of the basin, located on the Central African plateau (termed the upper Zambezi by hydrologists), the water moved slowly through low plains and swamps. The undulating topography changed radically at Victoria Falls, where the river plunged more than one hundred meters and became the middle Zambezi. It was on this stretch, downstream from Victoria Falls, that the British built Kariba Dam in 1958. Approximately one hundred kilometers further downstream, at the Cahora Bassa gorge, the river plunged once again, down a long succession of rapids and cascades, turning into a powerful and volatile force. The gorge marked the beginning of the lower Zambezi, which extended 650 kilometers to the Indian Ocean. Drawing from the British experience at Kariba, colonial planners decided that Cahora Bassa would be an ideal location for Portugal’s hydroelectric project.3

      When built, in the early 1970s, during the final years of Portuguese colonial rule, Cahora Bassa attracted considerable international attention. Engineers and hydrologists praised its technical complexity and the skill required to construct what was then the world’s fifth-largest dam. For them, Cahora Bassa confirmed that nature could be conquered and biophysical systems transformed to serve the needs of humankind. Portuguese colonial officials recited a litany of benefits they expected from the $515 million megadam and the managed environment it would produce—expansion of irrigated farming, European settlement, and mineral output; improved communication and transportation throughout the Zambezi River valley; reduced flooding in this zone of unpredictable and sometimes excessive rainfall. In slick brochures and public pronouncements, they claimed that Cahora Bassa would “foster human progress through an improved standard of living for thousands of Africans who live and work there.”4Above all, Cahora Bassa would generate a substantial influx of hard currency, since 82 percent of its electricity would go to South Africa—making it the largest dam in the world producing energy mainly for export. As a follow-up to this technological triumph, Portuguese planners envisioned building a second dam, sixty kilometers south of Cahora Bassa, at Mphanda Nkuwa (see map 1.3).