There is in the history of Vedic civilisation a pivotal moment, a rupture that would change everything and whose consequences would be felt for millennia: the progressive drying up of the Sarasvati. We have mentioned it in several previous articles as an established fact, a chronological marker that allows us to date the end of the Rig Veda as a living text. But the question of why this river disappeared deserves an article in its own right, because the answer is more complex and more instructive than it might appear at first sight, and because it says something important about the fragility of civilisations in the face of changes in their natural environment.
The Sarasvatî, today called the Ghaggar in India and the Hakra in Pakistan, was at the time of its full power one of the greatest rivers of the Indian subcontinent. Satellite surveys and geological analyses carried out since the 1970s have made it possible to reconstruct its course with remarkable precision. It rose in the foothills of the Himalayas, in the region of present-day Himachal Pradesh, and flowed southwest for more than 1500 kilometres before emptying into what was then the Arabian Sea, across what is now the Thar Desert. Along its course, it received the waters of several important tributaries and irrigated a fertile plain on which developed the greatest concentration of sites of the Indus-Sarasvati civilisation. Bhirrana, Rakhi Garhi, Kalibangan and hundreds of other larger and smaller sites were established on its banks or in its immediate proximity. It was the nourishing river par excellence, the axis around which an entire civilisation had organised itself for centuries.
The first cause of its drying up is tectonic, and it is now well documented by geologists. The Indian plate, which continues to move northward in collision with the Eurasian plate — producing the ongoing uplift of the Himalayas — caused progressive modifications of the terrain that affected the hydrographic network of the entire region. Two major phenomena occurred, probably gradually but also in brutal episodes linked to earthquakes. The first is what geologists call river capture: certain tributaries of the Sarasvati were captured by neighbouring, more powerful rivers. The Sutlej, which was probably one of the main tributaries of the Sarasvati, was diverted toward the Indus. The Yamuna, which also contributed its waters to the Sarasvati, was captured by the Ganges. These two diversions deprived the Sarasvati of a considerable part of its water supply.
The second tectonic phenomenon is the modification of the terrain in the middle and lower course of the river. Local uplifts of the ground, linked to the movements of the Indian plate, created natural barriers that interrupted the river’s flow at certain points, transforming a continuous course into a series of disconnected sections. These barriers also favoured the progressive silting of the riverbed in zones where the flow had slowed, creating conditions that accelerated the drying up. The Thar Desert, which today covers a large part of Rajasthan and Pakistan, is partly the result of this process: a fertile plain deprived of its nourishing river, surrendered to the advance of sand.
The second cause is climatic, and it combined dramatically with the tectonic phenomena to hasten the disappearance of the river. Between 2200 and 2100 BCE, an episode of prolonged drought struck a wide band of the intertropical zone of the planet. This episode, which climatologists sometimes call the 4.2 ka event — that is, the climatic event that occurred 4200 years ago — is one of the best-documented climatic disruptions of recent prehistory. It provoked severe and prolonged droughts across a zone stretching from the eastern Mediterranean to South Asia, simultaneously affecting the Akkadian Empire in Mesopotamia, the Egyptian Old Kingdom, the Indus-Sarasvati civilisation in India, and several other cultures of the region. The temporal coincidence of these civilisational collapses is not a coincidence. They share the same climatic cause.
For the Sarasvati, already weakened by the loss of tributaries due to river capture, this drought was the final blow. Precipitation over the Himalayas, which fed the glaciers whose summer melt swelled the river, diminished significantly. The monsoons, which brought the seasonal rains indispensable for recharging groundwater and maintaining river flow, became less abundant and less regular. The result was a progressive but inexorable fall in the level of the Sarasvati, until it was nothing more than a succession of pools and marshes in the lowest zones of its course, before disappearing entirely into the desert sand.
The combination of these two factors, tectonic and climatic, explains why the drying up was irreversible. In other contexts, a drought, however prolonged, can be followed by a return of precipitation that gradually restores river flow. But in the case of the Sarasvati, the river captures had definitively altered the structure of the hydrographic network. Even when the rains returned, the waters that had once fed the Sarasvati now flowed toward the Indus and the Ganges. The river could no longer reconstitute itself because its sources of supply had been permanently taken from it.
The populations of the civilisation of the 7 Rivers felt these changes progressively, over several generations. The first signs were probably a fall in agricultural yields in the zones most directly dependent on the floods of the Sarasvati, a reduction in the availability of water for irrigation systems, droughts more frequent and more prolonged. Faced with these growing difficulties, the populations began to migrate, first eastward toward the Ganges, whose waters were now swollen by the Yamuna lost to the Sarasvati, then southward. This migratory movement, which unfolded over several centuries, dispersed Vedic civilisation across a much larger territory, provoking the contacts and mixings with new populations that progressively transformed original Vedism.
What is fascinating in this story is that the populations of the civilisation of the 7 Rivers perceived their sacred river as a goddess, and that the disappearance of this goddess was therefore experienced not only as an ecological and economic catastrophe, but as a cosmic rupture, the disappearance of a divine presence on which their entire worldview was founded. The tenth mandala of the Rig Veda bears the traces of this pain, of this awareness that something irreplaceable is in the process of disappearing. And the progressive transformation of Sarasvati from goddess of the waters to goddess of speech and knowledge is perhaps the way in which this civilisation managed the mourning of its sacred river: by interiorising what it could no longer find outside.
The story of the Sarasvati is also, for our own era, a troubling mirror. We ourselves live in a period of climatic disruption that threatens water resources across entire regions of the planet. The Himalayan glaciers that once fed the Sarasvati today feed the Ganges, the Indus and the Brahmaputra, on which hundreds of millions of people depend. These glaciers are melting at an unprecedented rate under the effect of climate change. The question of what will happen when they have diminished sufficiently to no longer feed these rivers in the dry season is not a hypothetical question. It is a question whose answer is already taking shape, in the same regions where the Sarasvati ran dry four thousand years ago.
Le Rig Veda 
Laisser un commentaire