Glacial Saraswati?: New Data On An Old Question

Did a perennial glacial fed river flow through the Indus Civilization region of what is now Haryana and Rajasthan? Previous work on the fluvial history of this region had indicated that a distributary of the glacially sourced Sutlej was flowing through a network of paleo-channels buried under the river now known as the Ghaggar until around 8,000 years ago. The Sutlej distributary system then died out, turning that river course into a smaller monsoon fed channel system.

For a more detailed history of research on this topic you can follow this link - Ghaggar /Saraswati Posts.

Recently, in November 2019, Anirban Chatterjee and colleagues published new data on deposits of grey sand in the subsurface of the Ghaggar channel and adjacent floodplains. The youngest of these deposits are 4, 500 years old. Geochemical fingerprinting points to High Himalayan granites and gneisses as their source. This likely extends the glacial phase of the Ghaggar to more recent times, until about the beginning of the urbanization of the Indus Valley Civilization (IVC).

Here is the abstract:

The legendary river Saraswati of Indian mythology has often been hypothesized to be an ancient perennial channel of the seasonal river Ghaggar that flowed through the heartland of the Bronze Age Harappan civilization in north-western India. Despite the discovery of abundant settlements along a major paleo-channel of the Ghaggar, many believed that the Harappans depended solely on monsoonal rains, because no proof existed for the river’s uninterrupted flow during the zenith of the civilization. Here, we present unequivocal evidence for the Ghaggar’s perennial past by studying temporal changes of sediment provenance along a 300 km stretch of the river basin. This is achieved using 40Ar/39Ar ages of detrital muscovite and Sr-Nd isotopic ratios of siliciclastic sediment in fluvial sequences, dated by radiocarbon and luminescence methods. We establish that during 80-20 ka and 9-4.5 ka the river was perennial and was receiving sediments from the Higher and Lesser Himalayas. The latter phase can be attributed to the reactivation of the river by the distributaries of the Sutlej. This revived perennial condition of the Ghaggar, which can be correlated with the Saraswati, likely facilitated development of the early Harappan settlements along its banks. The timing of the eventual decline of the river, which led to the collapse of the civilization, approximately coincides with the commencement of the Meghalayan Stage.

The geological work looks to be sound. The data on sediment fingerprinting overlaps with what we know about High Himalayan geochemical signatures and present day Sutlej sand composition.

I do want to comment on another sentence from the abstract (emphasis mine)-

"This revived perennial condition of the Ghaggar, which can be correlated with the Saraswati, likely facilitated development of the early Harappan settlements along its banks"

Saraswati is the name given to this river by the Vedic people. Correlation of the river's perennial phase between 9,000-4,500 years ago with Saraswati is valid only if  you can demonstrate that the Vedic people were inhabitants of this region from before 4,500 yrs ago. Geological studies cannot establish this. A combination of archeology, linguistics (cracking the Indus script would be nice!) and genetics will eventually answer that. The other scenario is that the Vedic people could have migrated into this region much later and began venerating a smaller monsoonal Ghaggar as Saraswati. Work by Liviu Giosan and colleagues suggests that stronger monsoons over the Siwaliks sustained sufficient flow in the old channels of the Ghaggar until the late IVC period (~1800-1600 B.C).

When did this river come to be called the Saraswati is still an open question.

Two recent genetics papers using ancient DNA recovered from the IVC site of Rakhigarhi and from Central Asia argue that people from the Pontic-Caspian steppes migrated into South Asia between 2000 -1500 B.C. bringing with them the Indo-Iranian branch of the Indo-European language family. These would presumably be the Vedic people.

Read these papers. They are interesting.

1) On the existence of a perennial river in the Harappan heartland.
2) The formation of human populations in South and Central Asia.
3) An Ancient Harappan Genome Lacks Ancestry from Steppe Pastoralists or Iranian Farmers.

The Lost Rivers Of The Harappan Civilization- Remote Sensing Analysis

A lot of ink has been spent of this topic, both in the scientific literature as well as in popular books about the Harappan Civilization. The focus of many of these efforts has been on locating the "Vedic Saraswati", a river mentioned in the Rig -Ved. It is described as occupying the region between the Yamuna and the Sutlej and has been identified by many workers as the present day Ghaggar-Hakra.

Settlements of the Harappan Civilization were spread out over quite a large area in northwest India. Hence, it is necessary to map in detail the broader once existing hydrologic networks to assess the relationship between settlements and patterns of water availability and water use. This study uses remote sensing data and image processing techniques to unearth some of the buried paleo-river networks of this region of northwest India.

Twenty eight years of Landsat 5 imagery totaling 1711 multi-spectral images was bulk processed. This use of data covering multiple dates in a year allowed the investigators to reduce visibility issues related to shifting land use and cultivation, changing moisture patterns and variable cloud cover. 8000 km of paleo-river channels were mapped, some identified in previous studies, but many recognized anew.

The paper describes the various image processing techniques used to tease out the spectral signatures of the buried rivers. Don't be alarmed by words like Normalized Difference Vegetation Seasonality Index (NDVSI), Principal Component Analysis and the Tasselled Cap Transform.  One can understand the final interpretations without getting into the details of these techniques. Let me give a brief idea though.

These are techniques has increase the contrast between vegetation, soils with different moisture levels and bare terrain. For example, due to stronger water flow the river channel itself and the levees it builds contain coarser sediment as compared with the adjoining floodplains. These coarser sediment contain less organic matter and are less fertile. Less vegetation grows on the buried channels and levees than on the more fertile fine grained floodplain sediment. This contrast shows up well on data processed using NDVSI which essentially maps the vigor of vegetation. This technique was useful in delineating channels in the northern part of the study area.

The southeast part of the study area is more arid and has less changes in vegetation across the landscape. Here, the Tasselled Cap Transform was more useful in identifying river channels. This techniques organizes the spectral information into several (usually three) main axis or bands of information. One axis contains data variability of reflectance of bare terrain (mineral mixtures). The second contains variability in greeness (vegetation), and the third contains variability of wetness (water and soil moisture). Again, to give an example, this southeast region is fed by rivers draining Aravalli limestones. The calcium carbonate leached away from the rock is precipitated along river channels as a chalky mineral deposit. Buried channels show up as ribbons of  bright reflectance in  the Tasseled Cap Transform brightness band. Imagery of the dry months shows these channels more clearly, since in the wet months, increased soil moisture reduces the contrast of calcium carbonate rich sediment.

A judicious use of such techniques thus enabled the researchers to identify buried networks with different vegetation, soil moisture and mineral brightness properties. 

A map of the interpreted buried rivers is posted below.

Source: Hector A. Orengo and Cameron A. Petrie 2017

Of importance is a critique of some previous studies which attempted to highlight the spatial relationship between river channels and archaeological sites (emphasis mine):

The data provided by these analyses are also important in contextualising previous studies in which palaeo-rivers have been dated using the distribution of known archaeological sites. Notwithstanding the positional accuracy of these locations (see [10,63,64]), which would severely hamper their use for validation purposes, the results for the northern sector of the study area (Figure 3) suggest that proximity to the river might not be a good indication of contemporaneity as the fields close to the river channel might not have been the most productive in agricultural terms. Sites with an agricultural orientation might have preferred to occupy elevations above flooding level in the finer sediment accumulation area. Flooding events and changing river courses could also have had an important effect in the preservation of archaeological sites eroding and burying those that were locatedin the path of new courses or in their sediment accumulation areas.

In addition to these factors, the scale at which these correlations between specific palaeo-channels and settlement locations have usually been published (e.g., [30] (pp. 359–387), [31] (Figure 4.2)]) do not allow the accurate correlation between the two elements. The use of large area (small scale in a geographic sense) site distribution maps for these correlations results in a visual association between the shape of the palaeo-river and the line formed by the grouping of sites, but at these scales the sites could be aligned to a number of palaeo-channels given the number of rivers and the parallel morphology of the drainage in the Sutlej-Yamuna interfluve revealed here. This analysis thus suggests that at these scales it is not possible to co-relate lineal distribution of archaeological sites to any particular palaeo-river that we have documented. The results from previous studies reconstructing the chronology of the hydrological system using the position of archaeological sites and vice versa(e.g., [24,25], [30] (pp. 359–384), and [31]) are, therefore, considered unreliable.

..and

Given the complexity of the hydrological system, the variety in the climatic and weather system of this region, and the diversity of ways that ancient populations are likely to have obtained water, it is unwise to use the date of occupation at specific settlements to date when specific channels carried water. It is essential to date the different palaeo-courses independently to properly reconstruct the evolution of hydrological networks over long periods. The chronologically consistent reconstruction of this palaeo-river network would allow the testing of different hypothetical scenarios of water availability through the use of network analysis in combination to hydrological analysis.

Interesting work. Open Access.

The Theory Of The Glacial Sarasvati Has Been Given A Quiet Burial

Something significant went unnoticed and unreported amongst all the hoopla surrounding the recent paper on Harappan civilization and its link to climate change. The theory of the glacial Sarasvati got dumped. The paper does not even mention it as a possible reason for the reduced water flow in the Ghaggar. Based on its geographic description in the Rig Ved the Ghaggar has been equated with the Vedic Sarasvati river.

The glacial river theory proposed that the river Yamuna and the river Sutlej, both glacially sourced from the high Himalaya,  earlier flowed into the Ghaggar. They changed course around 2000 B.C or so to their present day channels. This switch starved the Ghaggar of water and it became a smaller ephemeral river. This theory also accepts that climate change did occur, but the main reason for the apparently sudden water shortage was the changing of course of the glacial rivers.

Until a few years ago, there just wasn't enough detailed work done on the sediment provenance (comparing characteristics of old channel sands of Ghaggar with those of present day Yamuna and Sutlej) and channel chronology of the Ghaggar system to say whether this theory was correct. But work  published in 2012 on river sediment provenance tied to a chronology and analysis of fluvial landforms have shown that the Yamuna and Sutlej did once flow into the Ghaggar but changed course to their present locations by late Pleistocene-earliest Holocene, thousands of years before the Harappan civilization. Since this work, no new data challenging these results has appeared. Scientists as evidenced by this paper appear to now accept that the Ghaggar was a monsoonal river right through the Holocene.

This result has annoyed not only geologists who had proposed the glacial river theory but also supporters of the indigenous Aryan theory. They had used the glacial river theory to time the presence of the Vedic people in the plains of Haryana and Punjab before 2000 B.C. The reasoning was that the Rig Ved describes a mighty Sarasvati flowing down from the mountains. Hence, it must have been glacially sourced and must have been the present day Ghaggar. The Aryans would have had to have been present in northwest India before the river became less mighty i.e. before 2000 B.C. This according to them destroyed the Aryan Invasion /Migration theory which proposed that the Aryans, who were a Central Asian people, entered India after the Harappan civilization disintegrated.

Where do we stand now in terms of the Aryan question in the light of the new results on the Ghaggar river?

Well, in exactly the same place as before! It was always futile to try to link the condition of the river, whether glacial or monsoonal to the question of the origin of the Aryans. The Rig Ved describes a big river. It doesn't really say that it was glacial in origin. If the Aryans had been present in the Punjab and Haryana before around 2000-1800 B.C. they would have seen a larger Ghaggar (due to a wetter climate).

At the same time, this supposed earlier presence of the Aryans in the Harappan realm does not automatically answer the question of their origins. They just as well could have represented an earlier wave of Central Asian migrants who settled in northwest India during the latter stages of the Harappan civilization. For this same reason, the indigenous Aryan theory would not have been strengthened even if the river had turned out to be glacial during Harappan times.

The geological history of the river cannot solve this riddle. A combination of archaeology, deciphering the script and genetics will be required. We await with anticipation the results of the DNA recovered from Harappa age skeletons.

In the meantime, people who tend to read too much into Rig Vedic hymns should accept that the Vedic poets who wrote (source) -

"This (Sarasvati river) has shattered mountain peaks with her fast and powerful waves, just (as easily) as one uproots the lotus-stems, let us invoke her,who strikes what is far and near, with holy hymns and prayers"..

and ..

"Whose boundless, impetuous and swift-moving flood gushes forth with a tempestuous roar"

may have been really looking at a brown colored muddy, silty, sluggish river originating in the Siwalik hills.

Put that down to poetic license!

Giosan Et Al Reply To Valdiya's Article On The Sarasvati River

You may recall this controversy which I detailed in an earlier blog post. A quick recap. A paper in PNAS by Giosan et al in May 2012 presented the results of geomorphological analysis of the Haryana and Punjab plains and concluded that there was no glacially fed rivers flowing through this region during the Holocene. This meant that the Harappan civilization in this region was being sustained by a monsoonal river system, the remnants of which is known today as the Ghaggar, identified by some as the river Sarasvati described in the Rig Ved.

Prof. K.S. Valdiya a very senior Indian geologist did not like this conclusion. Moreover, he felt that Giosan et al have not paid due respect to the work of Indian geologists working on the problem of ancient river systems of this region. He wrote a highly emotional article in Current Science in which he misattributed sentences which I had penned on my blog to Giosan et al and also misrepresented (in my opinion) the work of Giosan et al and other workers.

Both Giosan et al and I complained about the misattribution to Current Science to which Valdiya gave brief unsatisfactory replies.

Now Giosan et al have published a second reply in which they clarify the scientific queries that Valdiya had raised.

Here it is - Open Access.

I find it puzzling that the original paper came out in PNAS, but Valdiya chose to comment and complain - not as tradition expects in PNAS - but in Current Science.

He also has not replied to Giosan et al's second clarification.

Geochemical Data Supports Yamuna Became Tributary Of Ganga In The Pleistocene

How long has the Yamuna been flowing along its present course in the Indian plains i.e. flowing eastwards as a tributary of the Ganga?

Exploring the temporal change in provenance encoded in the late Quaternary deposits of the Ganga Plain - Shailesh Agrawala, Prasanta Sanyal, Srinivasan Balakrishnan, Jitendra K. Dash - Sedimentary Geology April 2013

Temporal analysis of Sr isotopes in soil carbonates and Sr and Nd isotopes in silicate fractions has been carried out in a sedimentary core (Kalpi core; 50 m long) raised from the southern bank of the Yamuna river, Ganga Plain, India. The aim of the study is to constrain sediment provenance through comparison with the modern Himalayan and peninsular river systems' water and bank sediments. Sr isotopic data in soil carbonates (0.71874 to 0.71410) and Sr\Nd isotopic data in silicate (0.72865 to 0.74544 and−13.9 to−17.2, respectively) vary significantly with depth and are indicative of both Himalayan and peninsular sources for sediments in the southern Ganga Plain. The positive correlation between 87Sr/86Sr ratio and 1/Sr in soil carbonate and the negative correlation between 87Sr/86Sr and εNd in silicate confirm mixing of sediments from these sources. Variations of 87Sr/86Sr ratios in soil carbonates show that at ~80 and 45 ka the Himalaya acted as the major source of sediments in the southern part of the Ganga Plain. The gradual decrease in 87Sr/86Sr ratios after 80 and 45 ka indicates change in source to peninsular India which is also supported by limited Sr and Nd isotope data in silicates. The change in sediment provenance corresponds well with the available climatic record and is suggestive of strong climatic control in sediment supply with high supply from the Himalaya during the interglacial period and peninsular sediments during glacial period.

Background:

My Criticism Of K.S Valdiya's Paper Published In Current Science

and Valdiya's reply was not satisfactory at all..

To those unfamiliar with the sequence of events:

1) Giosan et al publish a paper in the May 2012 issue of PNAS on fluvial geomorphology of rivers around the Harappan civilization and conclude amongst other things that the Sutlej and Yamuna rivers got diverted from the channels now occupied by the river Ghaggar (Haryana Punjab plains) to their present day course by Late Pleistocene. This meant that the Harappan civilization along the river named Ghaggar -also identified as the Vedic Saraswati by many- was watered by a monsoonal river and not a glacially connected river.,

2) I write a blog post of this paper on June 15 2012. I comment that some Indian geologists working on this problem accepted the scenario of a glacial Ghaggar /Saraswati during Harappan times without critically assessing the evidence.

3) My blog post appears on the Indo-Archaeology forum.  In the confusion due to many cross links my comments about the role of Indian geologists are misattributed to Giosan et al.  Giosan tries to set the record straight. K.S. Valdiya based on his correspondence with S. Kalyanaraman also confuses the source of those comments and misattributes them to Giosan et al in his article in Current Science. Valdiya accuses Giosan et al of diminishing the research of  Indian geologists partly because he misidentifies Giosan et al as the authors of those comments and partly because of Giosan's comment on the Indo Archaeology forum  that they have only referred to 'papers and authors presenting reliable data and facts’. S. Kalyanaraman forwarded this comment to Valdiya who then regarded it as a slight on the work of Indian geologists.
 
These below are my words that got misattributed to Giosan et al:

A geological narrative constructed without rigorous evidence has been promoted to support a theory of cultural evolution in northwest India.

and

..  now be revised or at the very least these geologists  need to admit that their theory has been seriously challenged.


4) I write a blog post on the geological problems in Valdiya's Current Science article.

5) Giosan et al protest the misattribution in the Correspondence section of February 10 issue of Current Science.

6) My comments and Valdiya's reply to Giosan et al and my comment published in the April 25 issue of  Current Science.

phew... I didn't know writing a nerdy geology blog will land me in such a controversy! :)

Moving on to Valdiya's reply to my comment I want to elaborate on Valdiya's denial that he misrepresented the work of other authors.

K.S Valdiya On The Glacial Saraswati In Current Science

In the latest issue of Current Science, geologist K.S. Valdiya has written a long response to a paper   by  Giosan et.al 2012 which concluded that the Yamuna and Sutlej rivers of northwest India stopped flowing into the Ghaggar river by early Holocene. There is a companion paper by Clift et al 2012 on this topic which Valdiya does not elaborate on.

The Ghaggar floodplains formed the agricultural heartland of the Harappan civilization. This finding by Giosan et al and Clift et al if true, meant that during the Harappan civilization the Ghaggar was not a glacial fed river but a monsoon fed river, but likely a perennial one due to a wetter climatic regime in the Ghaggar catchment areas of the Siwaliks. That in turn had implications for Harappan water use and agriculture methods. This question has also fed the controversy about the origin of the Aryans and the relationship between Aryans and the Harrappan civilization, since some say that a glacial Ghaggar was the Vedic Saraswati mentioned in the Rig Ved, an ancient collection of hymns in the Sanskrit language composed perhaps around 1500 B.C. or so.

K.S. Valdiya strongly disagrees with Giosan et al's findings that Holocene climate imparted a characteristic geomorphology to large glacial rivers of this region and that their finding suggests that there was no glacial river flowing on the plains of Haryana and Punjab during mid late Holocene. Goisan et al in due course may provide a detailed reply to Valdiya's arguments. I do have several comments on the way in which K.S. Valdiya has presented his evidence.

Fluvial History And The Fortunes Of The Harappan Civilization

 

In a recent issue of PNAS Liviu Giosan et.al. use a combination of high resolution topographic data, geomorphologic analysis and sediment dating to establish a chronology of the evolution of fluvial landforms of the Indus and its tributaries.

The Harappan civilization over a 600 year period from around 4500 B.P (before present) to about 3900 B.P flourished in this region and then went into decline with urban centers abandoned and populations moving eastwards towards the Himalayan foothills and the Gangetic plains. Goisan et.al's work - and there is also independent evidence for this -  shows that this 600 year period was a kind of a Goldilocks period. The region became arid, but not too arid.

Indus and its tributaries get water from two climatic regimes, the summer monsoons from the Arabian sea and winter rains from the northwesterly winter disturbances bringing moisture from the Mediterranian, Caspian and Black sea region. Most of the sediment load of these rivers is generated during the heavy erosion that takes place in the Himalayas during the summer monsoons. When rivers carry and deposit sediment along their course they are said to be in an aggradational mode i.e. the stream bed and the surrounding floodplains get raised as more and more sediment is deposited.

Over much of the earliest part of the Holocene, the Indus and its tributaries were aggradational. Then the monsoons weakened and the sediment load reduced. Winter rains falling as snow though kept river discharge active. Rivers without sediment or less sediment incise or cut into their own deposits. So, by mid Holocene all these rivers had developed a characterized profile of incised valleys and river terraces marking the original river bed and broad surrounding plains that because of  reduced rainfall were less prone to severe flooding.

Giosan et.al suggest that the Harappan people took advantage and adapted to these circumstances. There are Harappan and even pre-Harappan sites within these incised valleys of the Indus and its tributaries like the Beas and the Sutlej. This suggests that incision had occurred in the early Holocene and agriculture evolved to take advantage of manageable floods and a perennial water supply within the valleys and adjoining plains. 

After around 3900 B.P. the aridification intensified. The agricultural heartland of this civilization was along the  Ghaggar/Hakra river, located between the Sutlej and the Yamuna. This river was monsoonal fed and would have been perennial until then. As it slowly dried up, urban population centers could not be sustained and the Harappan civilization went into decline. There was a movement of people to the east towards the wetter Himalayan foothills.

This eastward civilizational shift is captured well in the figure to the left (Source Giosan et.al.). Red dots are Harappan sites. White dots are  Painted Grey Ware sites. Painted Grey Ware is a cultural phase that overlaps with the late Harappan.

This study also lends additional support that the Ghaggar river which has been identified as the mythical Saraswati river mentioned in the Rig Veda was not a glacial river in the Holocene. It has been proposed that the Sutlej and the Yamuna flowed into the Ghaggar and changed course around 4000 B.P to 3900 BP, triggering a water crisis. This study points out that the landforms of incised valleys typical of these glacial rivers are not present across the Ghaggar Hakra region. Sediment dates of river terraces along the Sutlej also indicate that the Sutlej had incised and was flowing along its present course by late Pleistocene.

Work by Clift et.al, using zircon dating to fingerprint sediment and Himalayan catchment areas of these rivers, which I reviewed in an earlier post  indicates that although the Sutlej and Yamuna likely did flow into the Ghaggar in the Pleistocene they changed course towards the Indus and the Ganges by late Pleistocene, thousands of years before civilization was established in this region. And there is some independent isotope studies on ancient water in buried channels along the Ghaggar that also suggests that there were no glacial rivers flowing into the Ghaggar during the Holocene.

Sometime back I got involved in a debate with indologist Michel Danino on my blog. I had pointed out that glacier rivers like Sutlej and the Yamuna have developed a characteristic morphology of a relatively narrow belt of incised valley and terraces. As has been suggested, if such large perennial rivers were flowing across the plains of Punjab in the upper reaches near the Siwaliks and joining the Ghaggar they would have prevented the formation of the alluvial fans systems that have developed in the upper reaches of the interfluve areas around Ghaggar.

Michel though was convinced that the Sutlej had flowed into the Ghaggar until in fact medieval times. I bring this debate up because Michel, who is not a geologist, ultimately came to this conclusion based on his reading of the geological literature. And here, I think, that Indian geologists working on this problem have a lot to answer to.

That the Sutlej or Yamuna may have flowed into the Ghaggar in the past is a perfectly reasonable geological hypothesis. But until these recent studies by Clift et.al and Giosan et. al. there was no convincing evidence for it. Earlier, geological evidence of a glacial Ghaggar/Saraswati has been based primarily on the satellite mapping of dried up channels near the Ghaggar river which indicated that in the past the Ghaggar was a bigger river. But, these channels were never shown to be connected to the present day glacially connected Sutlej and Yamuna basins. They could just as well be interpreted as belonging to a monsoon fed river originating in the lower Himalayan ranges. Nor was there any firm sediment provenance that could identify a specific Himalayan source for these channels or a sediment chronology to establish the long term fluvial history of this region.

Paleobotanical and sedimentological criteria had always indicated that increasing aridification and reduction in monsoon strength better explained the drying of the Ghaggar around 3900 B.P.  Despite all this, the Sutlej or the Yamuna changing course at around 3900 B.P  became the favored explanation for the drying of the Ghaggar. This scenario of a once large Ghaggar neatly fitted the description in the Rig Veda of a mighty Saraswati, a holy river that just like the Ganges was thought to have its source in the high glacial Himalayas. I suspect that the glacial river theory had more emotional appeal and gained acceptance among some geologists.

The strong assertions by geologists that the diversion of glacial rivers from the Ghaggar coincided with the decline of the Harappan civilization was used by archaeologists like Prof. B.B. Lal to place the composers of the Rig Veda on the plains of the Punjab before the Ghaggar dried up, apparently bolstering the theory that the Harappan people and the Vedic people were one and the same. A geological narrative constructed without rigorous evidence has been promoted to support a theory of cultural evolution in northwest India.

Unfortunately, this glacial past of the Saraswati timed to the demise of the Harappan civilization is now enshrined in textbooks written by senior geologists like K.S. Valdiya. They should now be revised or at the very least these geologists  need to admit that their theory has been seriously challenged. If geologists working on this problem still want to stick to the theory of a glacial Saraswati, they will need to come up with a more convincing data driven rebuttal to the work of Clift et.al. and Giosan et. al.

Giosan, L., Clift, P., Macklin, M., Fuller, D., Constantinescu, S., Durcan, J., Stevens, T., Duller, G., Tabrez, A., Gangal, K., Adhikari, R., Alizai, A., Filip, F., VanLaningham, S., & Syvitski, J. (2012). PNAS Plus: Fluvial landscapes of the Harappan civilization Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1112743109

Additional Posts: K.S.Valdiya on the glacial Saraswati in Current Science

Yamuna And Sutlej Stopped Flowing Into Ghaggar / Sarasvati By Early Holocene

The Yamuna stopped flowing into the Ghaggar / Sarasvati and shifted course eastwards into the Ganga as early as around fifty thousand years ago. The Beas and the Sutlej stopped flowing into the Ghaggar / Sarasvati and joined the Indus before ten thousand years ago, several thousand years before the beginnings of the Harappan civilization.

That is the conclusion reached in a paper in Geology  (behind paywall) by Peter Clift and colleagues using U-Pb (Uranium - Lead) dating of zircon crystals from ancient channels and alluvium of the Ghaggar / Hakra river.

I had earlier suggested that the Ghaggar likely never had any glacial connection. That statement now needs to be modified to read that there is a strong possibility that the Yamuna flowed into the Ghaggar in the Pleistocene and the Sutlej until the early Holocene.

Detailed mapping of the region between the Indus and the Yamuna where the present day Ghaggar / Hakra flows  has revealed the presence of many dried up channels suggesting that a much larger Ghaggar river existed in the past. The Harappan urban civilization declined and was abandoned by around 2000 B.C to 1800 B.C. One of the main reasons given is a prolonged drying of the region which made agriculture unsustainable. Monsoonal strength over this region has fluctuated for the last ten's of thousands of years and evidence from many different sources indicates that this region began experiencing aridity by mid Holocene and this arid phase moved eastwards over time slowing making urban centers and agriculture unsustainable. The larger dried up channels point to this climate change.

Another explanation of many of these dried up channels is the hypothesis that large glacially fed rivers like the Yamuna and Sutlej once flowed into the Ghaggar. They shifted course away from the Ghaggar  in the late Holocene, dramatically reducing water supply to the Harappan urban centers and contributing along with climate change to their decline and eventual collapse.

How does one figure out whether ancient channels represent glacially fed rivers and match them to known rivers? Clift and colleagues use a conceptually simple yet technologically challenging geochemical technique to make this match between ancient channels, present day rivers and their source in the Himalayas.

The Himalayan mountains are made up of several geological terrains of different ages. The Karakorum and Kohistan terrain (Trans -Himalayas) are younger than 300 million years old, the Tethyan Himalayas are 300 -750 million years old, the Greater Himalayas are 750 - 1250 million years old and the Lesser Himalayas are 1500 -2300 million years old. The ages of these terrains have been well characterized over the decades using a number of different radioactive clocks.

For this study the U-Pb clock contained within zircon crystals was selected. Zircon (zirconium silicate) is a hard mineral which occurs in granites and metamorphic rocks which make up large portions of these terrains. It can survive physical attrition during long transport by streams. It is also chemically quite stable and there is less chance of chemical weathering leaching out U or Pb from the crystal. Another advantage is that there are two clocks inside zircon. One through the decay of U-235 to lead-207 and another through the decay of U-238 to lead-206. So there is an inbuilt crosscheck on your results.

Why not just use the types of minerals to fingerprint the source rocks? That method does work is certain contexts but geological terrains of different ages can contain similar suite of minerals making discrimination based on a unique signal difficult.

Below is a map of the study area.

Source: Clift et.al. 2012

Black dots represent trenches. Stars represent drill sites and white squares represent samples from modern rivers. Dotted lines are proposed courses of ancient Yamuna and Sutlej. U-Pb dates were calculated from zircons sampled from the Indus, Ghaggar,  Beas, Sutlej and the Yamuna. The idea is that the headwaters of each of these rivers would be eroding sediment predominantly from different geological  terrains and therefore if enough zircon crystals were analyzed it would be possible to identify a geological age signal that is unique to each river. For that though large number of crystals need to be dated for a statistically robust result.

For this study more than hundred grains per sample were analyzed using a scary sounding instrument- the Laser Ablation Inductively Coupled Plasma Mass Spectrometer.  It was found that individual rivers do cluster at different ages i.e. they contain a population of grains within a distinct age range and could be discriminated from each other. For example the Beas showed a major population of zircon grains of age 300 -750 million years ago implying that its headwaters drained mostly the Tethyan Himalayas. Similarly the  the Yamuna sample contained a major population which clustered around 1875 million years. The Sutlej has two populations clusters, one at 750 -1000 million years ago and another at around 1830 million years or so.

The next step was to find out whether ancient sediments from dried up channels associated with the Ghaggar river contained zircon populations with age clusters that could be matched to modern rivers. If they did, then that would mean that that particular river was flowing in that channel in the past. And carbon-14  or Optical Stimulated Luminesence (OSL) dating of the sediment could tell when. So there are two kinds of dating techniques used here. The U-Pb technique dates the geological age of the rocks in the Himalayan headwaters of the rivers. The carbon-14 and OSL techniques date the timing of deposition of sediments in the various channels.

Channel and overbank sediments close to Harappan archaeological sites along the northern edge of the Thar desert were sampled. The sediments were dated using a combination of 14C which dates organic matter and OSL, a technique that is used to calculate the time since the sediment was last exposed to sunlight.

Analysis showed that ancient sediments did contain populations of zircons of distinct age ranges that could be matched to the Yamuna, Sutlej and the Beas implying that these rivers were flowing through these channels sometime in the past. Constrained by carbon-14 and OSL dates of the sediment, the patterns indicate that the Yamuna signal was lost around fifty thousand years ago implying a change of course of the Yamuna eastwards towards the Ganga at that time. The Beas and Sutlej signal was lost prior to ten thousand years ago, these two rivers migrating north-northwestwards and joining the Indus.

All this sampling is in Cholistan, the portion of the Ghaggar/Hakra in Pakistan. Some studies has mentioned ancient channels interpreted as the Sutlej joining the Ghaggar in Haryana in India, upstream of these sites. These channels were not sampled in this study. However, the site at Fort Abbas samples the main Ghaggar channel. Any signal of the Yamuna or Sutlej  joining upstream would have shown up here. The results indicate no signal from these rivers in the oldest sediments which are five thousand seven hundred years old or so.

If possible, these analysis could be extended in the future to sample more extensively the dried up large channels upstream in India too for a more expansive analysis. Over the last year some more studies (preliminary results presented at last year's AGU meeting) have shown an earlier episode of the Ghaggar drying up in the latest Pleistocene that coincides with a regional climate shift towards drier conditions. Did tectonically driven avulsion coincide with this climate change?

On the other hand, a paper in the GSA Bulletin by Sinha et. al. 2009. suggest a younger Yamuna, meaning that the Yamuna has been flowing in its present course for only the last 2-3 thousand years and may have been flowing westwards towards the Ghaggar before that. This study was based on detrital grains provenance studies and OSL dating of the Yamuna and Chambal sediments. I found the provenance analysis itself to be sound but the young Yamuna interpretation questionable, due to lack of sampling upstream of the cratonic rivers confluence and just one OSL date from the present day Yamuna channel.

So,  there are still answers to be found regarding the interplay of tectonics, climate and the Pleistocene and Holocene geography of these rivers.

Having said that, this is one of the more convincing studies of Ghaggar sediment and water provenance that I have come across so far.  Many earlier studies have suggested a much later river avulsion scenario wherein the Yamuna and the Sutlej change course as late as 2000 B.C. My impression was that these studies lacked the kind of hard evidence needed to pinpoint the dates of the deposition and the origin of the sediments. They relied mainly on the size of the channels without demonstrating physical continuity with the large glacial rivers,  or the presence of certain metamorphic grains and pebbles. Both these parameters are open to multiple interpretations and are not convincing of a high Himalayan source by themselves.

This study by Clift and colleagues along with some earlier isotope dating and provenance work on Indus and Ghaggar sediments by some of the authors and independent work on oxygen isotopes of ancient Ghaggar /Hakra channel water are strong results in favor of the Yamuna and Sutlej leaving the Ghaggar river thousands of years before the beginnings of the Harappan civilization.

The results also imply that these two rivers most likely stopped flowing into the Ghaggar thousands of years before the presence of Aryans in this region.

This is a touchy topic and it deals with whether the Aryans migrated into northwest India from central Asia around 1500 B.C. or so, bringing with them cultural habits and religious ideas that evolved into the Vedic Culture, or whether the Aryans were indigenous to this part since times immemorial. The Ghaggar has been equated with the river Sarasvati mentioned in the Rig-Veda by supporters of the indigenous Aryan theory.

It is described as a mighty river flowing from the high Himalayas. This in turn has been interpreted to mean that the Sarasvati would have been flowing out of glaciers for it to be mighty, and therefore the Aryans must have been present in northwest India before 2500 - 3000 B.C., because there is evidence that since then the Ghaggar became a smaller river.  This argument is then taken further to claim that the Aryans built the Harappan civilization. In this scenario the glacial rivers change course only after 2500 - 2000 B.C or so and the resulting water crisis forces the "Vedic" Harappans to disperse eastwards towards the Gangetic basin.

I have stressed that this attempt to link a hypothesis of a mighty Sarasvati to the presence of Aryans is misguided and one that has caused harm to the public understanding of the topic and to what constitutes good science. Many geologists and archaeologists accepted the validity of a glacial Sarasvati without critically weighing the evidence. Taking their cue, in web forums and books, supporters of a glacial Sarasvati have popularized the hypothesis of a late river avulsion and often presented it as irrefutable evidence favoring the indigenous Aryan theory.

I have commented on this earlier in Pragati and on my blog (here and here ) and suggested that evidence at that time did not support a late avulsion and further that this issue of the timing of Aryan presence in this region doesn't really depend on  glacial rivers flowing into the Ghaggar. Rivers can be mythologized and worshiped whether they are big or small. The Aryans could just as well have considered holy a Siwalik fed river and exaggerated its size in their hymns.

Linguistics, cultural evidence, archaeology and perhaps in the future higher resolution genetic data are better placed to answer the question of Aryan origins. Unfortunately, during this saga of the search for the glacial Sarasvati some very questionable geological scenarios have been put forth as being definitive. Perhaps the time has come for supporters of that theory to at the very least start being more cautious when promoting the late river avulsion theory.

Meanwhile, whether there were glacial rivers connecting the Ghaggar during Harappan times is not just an interesting geological question but has implications in understanding  Harappan water use and agriculture patterns. Head over to Dorian Fuller's (one of the authors of this study) blog The Archaeobotanist for some comments.

Clift, P., Carter, A., Giosan, L., Durcan, J., Duller, G., Macklin, M., Alizai, A., Tabrez, A., Danish, M., VanLaningham, S., & Fuller, D. (2012). U-Pb zircon dating evidence for a Pleistocene Sarasvati River and capture of the Yamuna River Geology DOI: 10.1130/G32840.1

Also see additional posts on this topic - 1) New Geomorphological Work on Ghaggar
2) K.S. Valdiya on the glacial Saraswati in Current Science

 

Geological Update On River Ghaggar / Saraswati

The river Ghaggar which flows through the Indian states of Haryana, Punjab and Rajasthan and onwards into Pakistan had dried up in the latest Pleistocene. Therefore it may not have been the main water source for the later mid-Holocene Harappan settlements in that region and also likely was not the river Saraswati described in Rig-Ved.

That's the gist from three separate studies  (pages 23, 24, 103) on the Ghaggar river basin presented at a meeting of the American Geophysical Union and summarized in Science.

The finding that the river Ghaggar likely dried up or had a drastically reduced flow in the latest Pleistocene is not that surprising from the perspective of the broader climatic regime existing from Late Pleistocene to Holocene. However, it is a surprising finding if you consider another theory of Ghaggar water flow - the glacially fed Ghaggar -  which I will come to later.

First, the climate change perspective.

After the Last Glacial Maximum, monsoonal strength over the Indian subcontinent has fluctuated over a millennial scale resulting in dry and wet phases lasting a few thousand years each.

A late Pleistocene arid phase affecting north west India is well documented by various studies on sediments and landscapes in Rajasthan, Gujarat and western Maharashtra. See this paper by Mishra and Rajguru and references therein. The studies by Gupta et al and Maemoku et al which suggest that between 15,000 years and 10,000 years ago the Ghaggar basin shows signs of drying up, likely reflect this phase of aridity.

This late Pleistocene arid phase was followed by an early Holocene wet phase reflecting a stronger Indian monsoon. Then by mid Holocene another episode of aridity set in which coincided with the ultimate demise of the Harappan civilization.

I don't want to comment here on the implications of these studies regarding water dependency of the Harappan civilization or the Vedic Saraswati problem.

Instead I want to point out that these new geological findings by Gupta et al and Maemoku et al do hint at an answer to another interesting geological question.. whether the Ghaggar was a glacially fed river in the past.

It has been hypothesized that the Sutlej and the Yamuna, both glacially fed rivers, flowed into the Ghaggar during the Holocene and by late Holocene around 2500 B.C to 1800 B.C avulsed or shifted course to their present positions. So along with climate change, rivers changing courses is another explanation given for the reduced water flow of the Ghaggar by late Holocene.

I think the time frame over which this problem has been thought out has a bearing on the choice between the climate change and river avulsion theories. If you only consider the Holocene and one episode of a river drying up (a larger Ghaggar drying up by 1800 B.C) then a Late Holocene river avulsion event  seems as plausible an explanation as a climate change one.

But if more studies confirm Gupta's and Moemuko's finding that the Ghaggar had indeed dried up in the late Pleistocene then that would weaken the theory that the Yamuna and Sutlej flowed into the Ghaggar until the late Holocene.

A glacially fed Ghaggar would likely not have dried up even during the late Pleistocene arid phase. Summer melting of the large Himalayan glaciers built up through the Last Glacial Maximum would have maintained enough water flow in the Ghaggar throughout the year.

The simplest explanation of these alternating phases of river drying and rejuvenation through the late Pleistocene into the Holocene is that the Sutlej and the Yamuna never flowed into the Ghaggar. The Ghaggar was not glacially fed, but by streams originating in the lower and sub Himalayas, and its fortunes always depended on the strength of the Indian monsoons.

One scenario of rivers shifting courses that does fit this extended late Pleistocene-Holocene time frame depends on the Sutlej and / or the Yamuna getting diverted away from the Ghaggar much earlier, around 14,000 years ago or so. The drying of the Ghaggar brought out by these two studies then reflect a combination of river avulsion and climate change.

Either way, these new findings make it cumbersome to support the theory of a glacially fed Ghaggar river.

Tip: Varnam

[Update 2012): New geochemical and geomorphological studies strongly suggest that Yamuna and Sutlej stopped flowing in to the Ghaggar /Saraswati thousands of years before the Harappan civilization. See these posts for more on this topic - 


1) New Geochemical and Sedimentological Work On Ghaggar
2) New Geomorphological Work on Ghaggar
3) K.S. Valdiya on the glacial Saraswati in Current Science 

River Ghaggar / Saraswati Did Not Have A Glacial Source In Historical Times

[Update : New geochemical and geomorphological studies strongly suggest that Yamuna and Sutlej stopped flowing in to the Ghaggar /Saraswati thousands of years before the Harappan civilization. See these posts for more on this topic - 

1) Geological Update On the River Ghaggar
2) New Geochemical and Sedimentological Work On Ghaggar
3) New Geomorphological Work on Ghaggar
4) K.S Valdiya On The Glacial Saraswati Published in Current Science 
-------------------

A number of recent studies have bolstered the case that the River Ghaggar  -  which has been equated with the River Saraswati described in the Rigveda - did not have a glacial source in historical times and was likely always fed from the sub Himalayas (Siwaliks).

Why is this of any interest?

The background is the controversial question of the origin of the Aryans.

The more widely accepted theory is that proto-Sanskrit speakers entered the northwestern parts of India after or during the latter stages of the demise of the Harappan city states beginning around 1800 -1500 B.C. The ancestors of these proto-Sanskrit  speakers can be traced according to this theory to the central Asia steppes. In terms of the local ecology, geological evidence shows that by this time the River Ghaggar which was once a river with substantial water flow and was perhaps perennial had transformed into a smaller ephemeral stream.

The competing theory is that the Aryans are indigenous to India - indigenous in the sense that they were present on the northwestern plains at least since the advent of agriculture. In this scenario the Harappan city states was an Aryan civilization. To support this more ancient presence of the Aryans on the plains of Haryana, Punjab and Rajasthan, one line of argument is to point to the Rigveda which mentions a mighty Saraswati river located between the rivers Sutlej and the Yamuna. The argument is that the composers of the Rigveda must have been living on the plains of Haryana when the Ghaggar = Saraswati was perennial which means before 1800 B.C which in one way supports the theory that they and the Harappan people were one and the same.

The Rigveda describes the Saraswati as originating high in the Himalayas. It is described as a mighty river and so has been thought to have been perennial and having a glacial source. But today the Ghaggar / Saraswati is no doubt fed from only the Siwaliks, nowhere near the high glaciers. To account for this, supporters say that earlier the glacially fed Sutlej  and /or Yamuna flowed into the Saraswati. Later around 1800 B.C or so the channels shifted and the Ghaggar was stranded as a small ephemeral Siwalik fed river. Image below shows the Ghaggar basin flanked by the Sutlej and Yamuna.

A virtual industry dedicated to creating geological scenarios as to how this must have happened and to collecting "evidence" has proliferated on the internet, in various articles and in popular books.

A review of the peer reviewed geological literature shows that these scenarios are wrong and are based on exaggerations of the size of the Ghaggar and misunderstandings of geological processes. I have written an explanation of much of the list below in an article for the magazine Pragati. A short list is given here.

1) Use of isotopes in search of Lost River - Journal of Radioanalytical and Nuclear Chemistry: Data on stable isotopes of water in buried channels of ancient Ghaggar in Rajasthan shows a composition compatible with water from Siwaliks and not glacial high Himalayas.

2) Is River Ghaggar, Saraswati? Geochemical constraints - Current Science: Shows based on sediment geochemistry and composition and geomorphologic and paleo-climatic constraints that the River Ghaggar was likely always Siwalik fed.

3) Late quaternary geomorphic evolution of Yamuna-Sutlej interfluve: Significance of terminal fan - Journal of the Indian Society of Remote Sensing : Studies the stratigraphy and geomorphology of Yamuna channels and concludes that the Yamuna has been flowing within its channel and has not been part of the Indus system i.e. could not have flowed into the Saraswati.

4) Saraswati Nadi in Haryana and its Linkage with the Vedic Saraswati River – Integrated Study Based on Satellite Images and Ground Based Information - Journal Geological Society of India: Collected data shows that metamorphic pebbles in the upper reaches of the River Ghaggar can be derived from Siwalik source rocks and does not indicate a high glacial Himalayan source. Also shows based on geomorphology that the Yamuna did not flow into the Saraswati.

5) Reconstruction of buried channel-floodplain systems of the northwestern Haryana Plains and their relation to the ‘Vedic’ Saraswati - Current Science: Demonstrates based on stratigraphic, sedimentologic and geomorphologic data that the River Ghaggar in historical times had a smaller flow regime than in the earlier Quaternary period and derived its sediments likely from the Siwaliks.

I say it is time to abandon the theory that Ghaggar/Saraswati had a glacial source in historical times.

That does not mean abandoning the broader theory that the Aryan /Vedic people were present on the Haryana plains before the collapse of the Harappan civilization. Archaeology and linguistics and perhaps genetics are a more powerful tool to address that question. Let me add here that most archaeologists and linguists support the theory that the Aryans were late arrivals to the northwestern part of India.

The funny thing is, in my opinion the theory of a glacial source of Saraswati is not necessary in this debate. The Ghaggar was a wetter river before 1800 B.C. because of a generally more wetter climate. Strong summer monsoons over the Siwaliks and then spring flow would have made human settlements along its banks sustainable. A life sustaining river would have been holy to the people depending on it, regardless of whether it had a glacial origin or not.

The insistence that there was a past glacial source derives from a belief that the Rigveda is accurate in every aspect of its recording of geography and physical events. Descriptions of Saraswati in Rigvedic hymns as originating from Heaven...High Mountains..boundless....impetuous...fast flowing.. arising from a slowly moving serpent Ahi (source here) has led to a conviction that the Saraswati arose from glaciers. This reading of the Rigveda has led to the theory being proposed initially and for sustaining it.

Unhappily for science and for those who are looking for a scientifically accurate account, this has frustratingly meant a popularization and easy availability through the internet of an increasingly untenable and unsupported geological narrative which is creeping into the public consciousness as the correct story. People who are supporting the glacial origin theory assert that they are approaching the problem as a scientific question and with a scientific temperament. I would like to take them at face value.

However, that does come with a condition and this is the willingness to give up on your pet theory if the evidence piles up against it. This is one of the critical tests of the scientific temperament. There is plenty to show now that the Ghaggar / Saraswati was always a Siwalik fed river. Persisting with the glacial theory in light of this gathering evidence and pointing to scripture as a back-up will diminish the scientific credibility of the "early Aryan presence" supporters and perpetuate misinformation about the subject. I hope one of them stands up and admits that geological data does not support this particular theory.

Is the Saraswati Still Flowing Underground

[ Update: Please refer to these posts for the latest results on the river Ghaggar

1) Yamuna and Sutlej stopped flowing into the Ghaggar by Early Holocene
2) Fluvial History and the Fortunes of the Harappan Civilization   ]
3) K.S. Valdiya on the glacial Saraswati in Current Science

 *********************

I have been working on this on and off for the past few days. The Times of India (March 31 2008, couldn't find it online) carried a big new report on how the governments of Haryana and Rajasthan are trying to revive the ancient lost river Saraswati which Indologists have identified as the ephemeral river Ghaggar which flows through Haryana and Rajasthan. The news reports had lots of stuff about ancient channels under the Thar desert and as expected lots of misconceptions about geological terms and concepts. I thought I will clarify some of the geological understanding regarding the river Ghaggar /Saraswati.

1) Where is the river Saraswati?

There are many Saraswati's. The one of interest is the Ghaggar river system. The Rig-Ved describes the Saraswati as flowing between the Sutlej and the Yamuna. This has led Indologists to identify the Vedic Saraswati with the present day Ghaggar. The present day Ghaggar system originates in the Siwalik sub Himalayan region. There is also a small tributary in the Ghaggar river system named Saraswati. It originates in the Siwalik hills near Ambala and joins the Ghaggar river system in the plains of Haryana. I looked around for a good annotated map of this river system and could not find any. Most maps depict the entire north Indian plains and claim that as the Saraswati river basin. This is misleading. Below is an annotated map of the Ghaggar -Saraswati basin that I've prepared. Click on image for larger map.



2) In the past the Ghaggar-Saraswati system contained a lot more water than it does today.

This is true. Today the Ghaggar is an ephemeral river flowing only in the monsoons. Near Sirsa it dries up. Across the border in Pakistan it is called the Hakra. Remote Sensing studies have shown the Hakra to continue southward through the Thar desert terminating in the Rann of Kutch. Several channels have been identified below the Thar sands in western Rajasthan and are believed to represent the ancient channel system associated with the Ghaggar -Hakra drainage. There are hundreds of Harappan age sites along the Hakra and Ghaggar indicating that few thousand years ago, these rivers flowed year round. Paleochannels are also present in Haryana and likely represent abandoned channels of the Ghaggar river system. See image below. Arrows point to paleochannel.

3) In the past, glacially fed tributaries of the Sutlej and the Yamuna flowed into the Ghaggar river system. Tectonically induced stream piracy resulted in a diversion of these streams away from the Ghaggar system causing it to become seasonal.

This argument has been supported by geomorphological and petrological lines of evidence. Near Roopnagar (see map above) the Sutlej make an abrupt westward turn and eventually joins the Indus. Indologists have claimed that this westward turn is a relatively recent phenomenon induced by tectonic uplift in the Siwalik area. Before the Sutlej or major tributaries of it flowed into the Ghaggar. To support this they point to a widening of the Ghaggar channel where the paleo-Sutlej would have joined the Ghaggar. Literature on the web has maps showing the paleo-Sutlej joining the Ghaggar, but no such channel has been found in Haryana.

The hypothesis that the Yamuna or channels of the Yamuna systems flowed into the Ghaggar system is based on petrology. The Marakand river is one of the tributaries of the Ghaggar. It originates in the Siwalik hills (Sub Himalaya) in the western part of the Paonta Valley. This river has a series of abandoned terraces at different elevations which indicate continued down-cutting of the river. Think of these terraces as where the river channel used to be. The topmost terraces are the oldest dated to around 5000 year before present. These older terraces have been found to contain pebbles of quartzite and other metamorphic rocks (V.K.M Puri and B.C Verma, 1998; Glaciological and Geological Source of the Vedic Saraswati in the Himalayas, Itihas Darpan Vol IV, No 2: 7-36). The present drainage of the Marakand flows through only the lesser and sub Himalayas which is mostly a sedimentary terrain along with very low grade metamorphic rocks and the present channel does not contain metamorphic clasts of the type found in the older terraces. This has been taken to indicate that around 5000 years ago the Marakand was receiving sediments from streams draining metamorphic terrain and this source was cut off sometime later. Map below shows this scenario. The only way for the Marakand to have received sediments from metamorphic terrains was for the tributaries of the Yamuna - which have their source in the high Himalayas composed of metamorphic rocks - to have flowed west-north west through the Paonta Valley and joined the Marakand. Later the Yamuna captured these tributaries and this sediment supply stopped. I have not read the original paper and cannot assess the details of the sediment petrology, but taken on face value this finding supports the hypothesis that the Ghaggar was once supplied by glacial streams from the high Himalayas. Map below shows the Paonta Valley. T refers to river terraces.


Another study using geochemistry of the Ghaggar sediments has refuted this interpretation. This study uses strontium (Sr) and neodymium (Nd) isotope composition of sediments to track down the sources of sediment. This is how it works. Radiogenic Sr is enriched in crustal components which are highly differentiated from their original mantle sources. So rocks like granites, sediments derived from their weathering and their metamorphosed equivalents tend to be enriched in radiogenic Sr. The high Himalayas where all the glacial streams originate are composed of such rocks. Crustal components such as oceanic basalts, deep sea sediments and their weathered and metamorphosed equivalents are enriched in Nd isotopes reflecting less differentiation from the original mantle sources. The Indus Tsangpo suture zone, the Tibetian sedimentary series and sub-Himalayan terrains such as the Subathu formation have such high Nd signatures. So a plot of Sr vs Nd isotope composition of sediment works well to discriminate sources of sediment. Such an analysis has shown that Ghaggar sediments for the past 20 thousand years are much less Sr and more Nd than sediments of the Yamuna, Ganga and Sutlej. The inference is that the Ghaggar did not receive sediments from high Himalayan Sr rich terrain. It was never glacially fed and the drying of the Ghaggar was a result of aridification in Rajasthan beginning around 3500 B.C. and not due to tectonic controls on drainage patterns. This paper does mention the clast hypothesis favoring a glacial origin but besides presenting geochemical data does not give an alternative explanation for the metamorphic clasts.

Isotope composition of fresh water in buried channels of Jaisalmer district, Rajasthan interpreted as part of the Ghaggar system, using isotopes ²H, ¹⁸O, ³H and ¹⁴C appears to indicate that this water is ancient on the order of several thousand years old, was replenished when the river was flowing, but the d¹⁸O (ratio of ¹⁸O to ¹⁶O) composition does not show any signatures of glacial origin. The oxygen isotope composition of rainfall in affected by altitude. More than 99% of oxygen is ¹⁶O and 1% is ¹⁸O. As water vapor condenses at a particular altitude ¹⁸O is preferentially removed in rainwater leaving rising clouds depleted in ¹⁸O. This is really a temperature effect on oxygen isotope fractionation. At lower altitudes and therefore higher temperatures the lighter isotope ¹⁶O will fractionate preferentially in the vapor phase. This effect is reduced at low temperatures. So rainfall falling on the Siwaliks at lower altitudes will have a higher d¹⁸O value compared with rainfall/snow falling in the low temperature glacial region of the high Himalaya. The composition of ancient fresh water in the paleo-channels of Rajasthan has higher d¹⁸O value compared with Himalayan glacial standard indicating that glacial water did not contribute to this ancient river. This further supports the hypothesis that the Ghaggar system never had any glacial connections and always drained only the Siwalik- Sub Himalayan region.

So the petrology of the clasts in Markand terraces support a past glacial contribution to the Ghaggar while the geochemistry of sediments and ancient water does not. I would really like to take a look at those metamorphic clasts.

There is another line of evidence which seems not to have been explored in this context and that is paleo-current analysis of the older terraces along the Paonta valley. Paleocurrents and therefore the direction of stream flow can be found out by analyzing the orientation of sedimentary structures such as channel bedding surfaces, imbricate patterns of pebbles in conglomerates, ripple marks in finer sands etc. This type of analysis can tell us if at any point in the past streams flowed west-north west along the Paonta valley which would support the glacial origin hypothesis.

Update: I just had to write this update seeing this post has generated a lot of traffic. Saying that metamorphic clasts are present in the river terrace sediments of Marakand river is not enough evidence that there was a source from the high Himalayas. The lesser Himalayas in which the Marakand originates contain some low grade metamorphic rocks. The high Himalayas contain medium to high grade metamorphic rocks. So specifying the grade of metamorphism is important and at least in the literature available I did not see any specific description. Even if high grade metamorphic fragments were present in the Marakand terrace sediments it does not necessarily mean that the present day Marakand had a source in the high Himalayas. It is important to understand what type of component do the high grade metamorphic fragments form within the terrace pebbles. Are the pebbles entirely composed of the high grade metamorphic minerals? That would indicate that the pebbles are broken off pieces of high grade metamorphic rocks indicating a primary source. Or are the pebbles composed of older sedimentary rocks (lithoclasts) which contain high grade metamorphic minerals as detrital grains. That would indicate that the high grade metamorphic minerals have been recycled into the Marakand terraces by the weathering of an earlier sedimentary sequence, which in turn were made up of detritus eroded from older high grade metamorphic terrains. Simply put rocks of higher Himalayas and lesser Himalayan sequences eroding to form the Siwaliks, which in turn eroding to shed detritus in the present day Marakand. Metamorphic minerals recycling as detrital grains through earlier sedimentary sequences into the present day river terraces without the Marakand river being connected to streams draining high grade metamorphic terrains. Sediment provenance studies can be complicated in terrains like the Himalayas which has seen successive orogenic episodes and recycling of the sediments, and I want to find the original paper on these clasts to write a more detailed post.

4) The Saraswati is still flowing underground

A river system has several flow regimes associated with it. The most common is the surface flow. At present the Ghaggar has surface flow only during the monsoons. River channels have sometimes hundreds of feet of sand and sediment deposits. There is groundwater in these sands and this groundwater flows through this sand or even through subsurface bedrocks. Such a flow must exist below the present channels of the Ghaggar river system at least in Haryana where the river still flow during monsoons. Another type of underground flow is when there is a subterranean cave system. Surface waters can disappear underground and flow through such caves. This type of terrain is not present along the Ghaggar-Hakra. So the underground flow of the Ghaggar-Saraswati river is really groundwater flowing along the present and abandoned channels replenished by monsoon water from the channels and the surrounding plains. At places this groundwater appears at the surface as springs. There are temples with holding ponds to tap these spring water at several places in Haryana such as Kapil Muni. These springs are taken as evidence that the river is flowing underground. Rates of groundwater flow vary depending on permeability of the aquifer and hydraulic gradient, usually averaging to 10's of meters per day. Such rates are possible for groundwater flowing under the Ghaggar channels in the Siwalik region and the upper parts of the stream in Haryana and may explain reports of "waves" coming out of springs, the "waves" being groundwater flowing out as a spring at a fair rate. Downstream towards Rajasthan is a different story. Radioactive tracer studies have shown that at least in Rajasthan the flow in buried channels is measured in few tens of cm per year, suggesting near stagnation of groundwater and no replenishment from the Himalayan headwaters of the Ghaggar system. This water is likely to be old water which recharged the aquifer when Rajasthan was wetter. This has been borne out by isotope studies carried out by India's Bhabha Atomic Research Centre. Isotope data also indicates no glacial contribution to this old water. So the groundwater system associated with the Ghaggar drainage is likely to be a series of disconnected aquifers being recharged primarily through monsoon discharge of the river and through surrounding plains in Haryana and possibly not being replenished much in Rajasthan.

5) Targeted drilling in these paleochannels will yield a lot of water.

It is likely that these paleochannels will yield a lot of water. In Punjab and Haryana there are already thousands of bore wells extracting groundwater. Many of them no doubt have been unknowingly sunk in buried channels. Groundwater levels are falling in both these states through over-exploitation. Exploitation of these buried aquifers by targeted drilling has the potential to benefit Rajasthan more, though I feel that claims that these buried channels may contain as much water as the Sutlej canals are exaggerated. Preliminary drilling in Rajasthan along interpreted buried channel has yielded fresh water. These fresh water zones are linear and roughly trend N-S, coinciding with the direction of the ancient drainage. But more work needs to be done to understand the quantity and quality of these water resources in Rajasthan.

6) In Libya an ancient river channel has been discovered and rejuvenated into a man made river. The Saraswati can similarly be rejuvenated.

In Libya groundwater is being extracted from the Nubian sandstone aquifer which is made up of marine sedimentary sequences ranging in age from lower Paleozoic to the Cretaceous. The aquifer was last replenished several thousand years ago when north Africa was wetter. Water extracted from this aquifer is being distributed through a connected system of underground pipelines which is called the man made river.

Plans to rejuvenate the Saraswati are really linked to projects like the National Water Grid. The idea is to use excess water from the Indira Gandhi Nahar Project (IGNP) and the floodwaters from the Ghaggar river to recharge the aquifers in the Thar desert, some of them coinciding with buried channels of the Ghaggar and Hakra system. Bombastic claims have been made that a sustainable system of a million tube wells can be developed. Sustainability depends not on the original water stored in these aquifer but upon recharge of groundwater from surface water brought by the Rajasthan canal which is being extended into Gujarat. I have to say that geo-engineering projects may become necessary as climate change will affect the water resources in the Gangetic river system. Say Himalayan glaciers decline and monsoon becomes concentrated in short bursts, how do we deal with an overall decline in water but also an excess during very short periods. Is storing water in underground aquifers like to one's identified in Rajasthan a viable option? What are the engineering hurdles and environmental problems likely to crop up?