Zambezi the overflow of the Zambezi in the rainy season. The delta of the Zambezi is today about half as broad as it was before the construction of the Kariba and Cahora Bassa dams controlled the seasonal variations in the flow rate of the river. Before the dams were built seasonal flooding of the Zambezi had quite a different impact on the ecosystems of the delta from today as it brought nutritious fresh water down to the Indian Ocean coastal wetlands. The lower Zambezi experienced a small flood surge early in the dry season as rain in the Gwembe catchment and
Zambezi sourced from the same great internal lake. The Portuguese were also told that the Mozambican Espirito Santo "river" (actually an estuary formed by the Umbeluzi, Matola and Tembe rivers) was sourced from a lake (hence its outlet became known as Delagoa Bay). As a result, several old maps depict the Zambezi and the "Espirito Santo" rivers converging deep in the interior, at the same lake. However, the Bisa-derived etymology is not without dispute. In 1845, W.D. Cooley, examining Pereira's notes, concluded the term "Zambezi" derives not from the Bisa people, but rather from the Bantu term "mbege"/"mbeze" ("fish"), and consequently