The reservoir was put into service in 1965, but did not reach its optimal water level until 1971. Due to the great area of the reservoir, villages home to approximately 5,000 people had to be abandoned. The largest of these, the village of Ganzee, had approximately 1,200 residents. Most displaced residents were moved to new villages (Dutch: transmigratiedorpen) downstream from the dam, in many cases with the same names as the previously abandoned hamlets. The most important being Klaaskreek, Nieuw Ganzee, and Marshallkreek. A separate government operation, "Operation Gwamba," was conducted to save animals from the soon-to-be lake bed.