Which lake in Africa has reduced in size by 90% since the 1960s due to droughts and water diversion?

Lake Chad is the correct answer because it has indeed experienced a dramatic reduction in size, shrinking by approximately 90% since the 1960s. This significant decline is attributed mainly to a combination of severe drought conditions and the diversion of water for agricultural use. The lake, which was once one of the largest in Africa, has seen its surface area diminish considerably, posing challenges for local ecosystems, communities, and water management.

In contrast, Lake Victoria, while facing its own environmental issues, has not seen a decrease in size as extreme as Lake Chad. Lake Tanganyika and Lake Malawi also continue to maintain their sizes relative to historical standards, despite environmental pressures, and do not share the same dramatic reductions in volume that characterize Lake Chad. Hence, Lake Chad stands out as the most significantly affected lake in Africa according to the criteria set in the question.