Aryan Invasion Theory v/s Aryan Migration theory is a controversial issue that has been fiercely discussed among Indologists. Both the theories find strong supporters utilizing almost the same data available to them, using it conveniently, thus making the issue more complicated.
However, there can not be a dispute over a fact that Ghaggar-hakra is not a new-found lost river. It finds mention in the several records from last 200 years. It still seasonally flows, disappears in Thar desert and reappears in present Pakistan. Also, there is no dispute over the satellite images and the various maps of the river changing courses in the past and its ancient tributaries those have taken independent course because of the tectonic shifts.
The similar fact is about all the rivers in the north-west region. It is well established fact that Ghaggar as compared to present pitiable condition, once upon a time was rich with the flowing waters. The only point is disputed by Rajesh Kochhar raising a serious question on the amount of the water that would have been flowing through the paleochannel of Ghaggar in the remote past and whether Vedic descriptions of Saraswati and present Ghaggar are of the one and the same river? As per his research, Mr. Kochhar suggests that Vedic Saraswati and Ghaggar cannot be the same rivers and he is right in his assessment.
In Rig Veda Saraswati is abundantly praised with its mighty flow, through the cliffs. It is called as the mother of all rivers. (7.36.6 RV) It surpasses might of the all other rivers (7.95.2 RV) According to Kochhar, Saraswati mentioned in tenth Mandala of Rig Veda is not identical with the Saraswati mentioned in the previous Mandala’s of Rig Veda. The mention of various rivers in the tenth Mandala goes like this;
“5 Favour ye this my laud, O Gangā, Yamunā, O Sutudri, Paruṣṇī and Sarasvatī: With Asikni, Vitasta, O Marudvrdha, O Ārjīkīya with Susoma hear my call.
6 First with Trstama thou art eager to flow forth, with Rasā, and Susartu, and with Svetya here, With Kubha; and with these, Sindhu and Mehatnu, thou seekest in thy course Krumu and Gomati.
7 Flashing and whitely-gleaming in her mightiness, she moves along her ample volumes through the realms.” (Trans. By Griffith HYMN LXXV.)
The Ghaggar-Hakra hypothesis stresses that Yamuna and Satlej rivers used to be tributaries of Ghaggar River, thus adding huge water supply in the Ghaggar system. Both the rivers ceased to be tributaries to Ghaggar as they changed their course because of tectonic shifts.
But from Rig Veda itself, it clearly appears that Yamuna and Satlej (Satudri) were, in fact, the independent rivers of each other, not tributaries to the Vedic Saraswati, then how can it be claimed that the Sarasvati was a large river in Vedic times because she received ample of water from Yamuna and Satlej?
This only does prove that the River Vedic seers were referring to was not the Ghaggar, but the River located somewhere else! And it is none but Afghanistan as Rigveda itself has evidenced it!
The investigations on the bed of Ghaggar river has yielded interesting results. Extensive drilling done near Kalibangan by a team led by Mr. Sanjeev Gupta (Imperial College London) showed that the river sediment deposits ceased in this tract after approximately 14000 BCE. Mr. Gupta suggests that there was no big river here in Indus times. Japanese team too did research in Paleocene channel of Ghaggar system, headed by Hideaky Maemoku, have proved that the sand dunes surrounding Hakra are older than 10000 years.
Noteworthy to mention here is, Ghaggar had never been perennial (Glacier fed river ) as no proof of mineral deposits of Himalayan glaciers are traced in Ghaggar system so far.
Giosan et al in PNAS (Fluvial landscapes of the Harappan Civilization; 2012; June 26; 109 (26): e1688-94) have also proved that “The much touted Ghaggar-Hakra was a monsoon-fed river, not the Vedic Saraswati fed by the melting snows of high mountains.”
The general consensus among the scholars is Ghaggar was a seasonal river, fed by the monsoon, with water enough to irrigate farms, but not a mighty or Himalayan glacier fed river as described in Rig Veda. Satlej, Yamuna used to feed water to Ghaggar system, but in Pleistocene period, pre-10,000 BC, not later than that. Satlej and Yamuna had changed their course in very remote past. If this is the case it raises serious problems over Vedic period and its geography itself. In any case Harappan settlements in Ghaggar-Hakra basin are dated from 3300 to 1800 BC. Over 1000 Harappan settlements are found across the banks of the Ghaggar river. As explained in another article I have shown that Indus culture do not reflect any way the presence of Vedic elements in either settlement. If Ghaggar is somehow identified with Saraswati, Vedic period has to be far stretched back, which at any rate cannot be the case, for simply there are no satisfactory explanations available on either Vedic or geographical grounds.
This make it very difficult or almost impossible to relate Ghaggar with the Vedic Saraswati, as geographical proofs rather go contrary to the Vedic myths. Hence it becomes necessary to relocate the existence of Vedic Saraswati elsewhere. We, unfortunately cannot be in the agreement with the scholars those want to establish progenitors of the Indus culture were Vedic’s. As it is rightly stated by Dr. Francesco Brighenti, "It seems that a new scientific consensus is emerging which neutralizes the pseudo-scientific argument about the "Mighty Saraswati", used by Hindutva folks & their sympathizers to identify the Vedic Age with the period of the Indus Valley civilization.”