An old, dried-up river has been unearthed by the Union Water Ministry in Prayagraj—earlier, Allahabad—that linked the Ganga and Yamuna rivers, a report has stated in October 2019. The discovery by scientists from the CSIR-NGRI (National Geophysical Research Institute) and the Central Groundwater Board came about in December 2018 during a helicopter-borne geophysical survey over the Prayagraj and Kaushambi region, Uttar Pradesh. The National Mission for Clean Ganga (NMCG), a body under the Union Jal Shakti Ministry that coordinates the cleaning of the Ganga, has stated that it wants to develop it as a potential groundwater recharge source. Knowledge on subsurface connectivity between Ganga and Yamuna rivers is seen as crucial when planning for cleaning of the Ganga river and protecting safe groundwater resources.
The ‘ancient buried river’ is around 4 km wide and 45 km long; it consists of a 15-metre-thick layer buried under soil. It is a buried paleochannel that joins the Yamuna river at Durgapur village, about 26 km south of the current Ganga-Yamuna confluence at Prayagraj. Paleochannels reveal the course of rivers that have ceased to exist.
The finding of the palaeochannel came after a 2016 report of a seven-member committee commissioned by the Water Resources Ministry, which was led by Professor K.S. Valdiya of the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR). The report stated then that evidence from palaeochannels suggested that a mythological Saraswati river did exist in the region. The conclusion relied on reports and maps of palaeochannels in north India and a separate, ongoing project by the Central Groundwater Board to map the aquifers—extremely deep stores of groundwater—of India.
Meanwhile, a report in December 2019 reported that a research by the Physical Research Laboratory (PRL), Ahmedabad, along with IIT, Bombay has come up with “unequivocal evidence” that there existed a perennial river on the plains of north-western India that could be the mythological Saraswati. The researchers have concluded that the river (along the ancient course of the modern seasonal stream, Ghaggar) flowed through Uttarakhand, Haryana, Punjab, Rajasthan before being emptied into the Arabian Sea at the Rann of Kachchh. The river never flowed independently at Allahabad, as is believed, but parts of it united with the Yamuna river in its early stages. As the Yamuna and the Ganga meet at Allahabad, that is how all the three are said to have met.
The river, according to the researchers, flourished along the ancient course of the modern seasonal stream, Ghaggar, in north-western India. The scientists arrived at this by determining the depositional ages of the coarse-grained white sand layers that occurred some 3-10 metres below the modern alluvium of the floodplain of the Ghaggar river. Radiocarbon dating was done and optically stimulated luminescence methods were used at the PRL to determine the date.
The research was published in the journal Scientific Report.
The researchers state that the Saraswati was perennial and had flowed from the Higher Himalayas between 7,000 BC and 2,500 BC. Its flow continued till 20,000 years ago but then diminished due to the extreme aridity of the last glacial period. However, it was revived in its strength about 9,000 years ago and flowed for the next 4,500 years. Then the river later lost its perennial strength again.
The river is said to have originated in Har-ki-dun valley in Garhwal, Utarakhand and been 1500 km in length, 3-15 km in width and about 5 metres in depth.
It is stated that the Harappan civilisation had built its early settlements along the banks of the Saraswati in 3,800-1,900 BC. The claim is that the demise of the river, and not the Aryan invasion, is linked to the disappearance of the Harappan civilisation in north-western India. The duration is believed to coincide with the flourishing of the Pre-Harappan and Early Harappan cultures along the river’s banks—with the beginning of the Meghalayan Stage, i.e., the current dry phase in the global climate that began about 4,200 years ago.
However, an anomaly is in that whereas the Saraswati is said to have had sources in the glaciated regions of the Higher Himalayas, similar to the Ganga, Yamuna and Sutlej, the modern Ghaggar has no direct connection to the Higher Himalayas at all, as it originates from the foothills of the Himalayas—the Siwaliks. The researchers state that then the only likely path for the glacier-melt water for the ancient course of present-day Ghaggar (Saraswati) could have been through the distributaries of the Sutlej. Further, the decline of the ancient Ghaggar course was probably due to the rapid drying up of the Sutlej-fed channels. It has been said that the mythical Saraswati dried up due to tectonic shifts of the earth that cut off the supply to the river and the remaining waters seeped down into the ground.