The Indian campaign of Alexander the Great began in 326 BC; Alexander was born September 20, 356 B.C. in Pella, in the Kingdom of Macedonia. During his leadership, he united the Greek city-states and led the Corinthian League. He also became the king of Persia, Babylon and Asia, and created Macedonian colonies in Iran. After conquering the Achaemenid Empire of Persia, the Macedonian king (and now high king of the Persian Empire) Alexander launched a campaign in North West India (what is now Pakistan.)
The rationale for this campaign is usually said to be Alexander's desire to conquer the entire known world, which the Greeks thought ended in north-western India, and he did by traveling the vast distances from Asia Minor to India by a fleet of 100 boast. However, now these rivers either do not exist or are far too small for his fleet of boats to sail upon.
So what happened to all the water?