The translators of Alexander’s India invasion accounts comment that Indus is the greatest of all the rivers in Asia, except the Ganges, which is itself an Indian river ; that its sources lie on this side of the Paropamisos or Kaukasos; Ktesias, whose authority sometimes has been questioned, states that where the Indus is narrowest it banks  are 40 stadia apart, and where broadest 100 stadia; Patali province existed between the eastern and western branches of the mouth of the Indus.

When the Hydraotes fell into the Akesines Alexander continued his voyage down the latter river (which in preference to the Hydraotes gives its name to the united stream) until he reached the junction of the Akesines with the Indus. For these four vast rivers which are navigable yield up their waters to the river Indus, but not each of them under their special name. For the Hydaspes discharges into the Akesines and the single stream then forms what is called the Akesines. But this Akesines again unites with the Hydraotes and after absorbing this river is still the Akesines. The Akesines after this receive the Hyphasis, and still keeping its own name falls into the Indus, but after the junction it resigns its name to that river.

Alexander had fixed the confluence of the Akesines and the Indus as the boundary of the Satrapy of Philippos. Alexander bestowed the satrapy of the Parapamisadai to Baktrian Oxyartes, father of his wife Roxana.

He then appointed Oxyartes and Peithon satraps of the country which extended from the confluence of the Indus and the Akesines to the sea, together with the whole sea-board of India.  

Thus before we say that Indus valley civilization has disappeared, it is necessary to identify the region where Akesines was flowing. It is not that these rivers which watered the ancient India have all dried up.