S1E29 : The Roaming Lake

Searching for the Dragon Balls, Goku comes to a desert region where he hears the legend of the moving lake. There, Goku rescues Namu as he is attacked by monsters. Namu has gone upstream to investigate why the river has dried up! After discovering that Giran and his tribe had damned up the river, Goku breaks the dam with a Kamehameha, but this time a sandstorm buries the river!! The villagers despair, but after the sandstorm leaves, it leaves behind the legendary lake.