use of isotopes in search of lost river, journal of radioanalytical and nuclear chemistry, vol. 257,...

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Journal of Radioanalytical and Nuclear Chemistry, Vol. 257, No. 1 2003 5-9

Use of isotopes in search of Lost River

S M Rao

15, Sarovar, Sector 9A, Vashi , Navi Mumbai 400 703, India

(Received November 6, 2002)

Ample evidence exists from ancient lndian texts, geomorphology and sedimentology that a mighty river that once originated in the Himalayas

flowed in the North-west lndia dur ing 7000-3000 BP and disappeared in the sands of the Rajasthan deser t. Remote sensing combined with ground

search identified part of the buried channel of the ancient river in the Jaisalmer region of Rajasthan. Isotope study showed that the fresh

groundwater in that region was indeed ancient and slowly moving southwest and probably had headwater connection in the lower ranges of

Himalayas, but not to any glacier. The isotope data CZH,180, 3H and 14C) compare weil with the data in a similar study on another bral1ch of the

buried channel in the Cholistan par t of the Thar Desert in Pakistan.

Introduction

The 'Lost River' of Northwest India generally

considered as the legendary Sarasvati River of Vedic

times has been discussed in large detail in a recent

publication . The subject evokes strong feelings of

reverence, curiosity and scientific enthusiasm in people

of different pursuits. Scholars and students of the Vedas

consider it as their spiritual enquiry, historians and

archeologists like to investigate the Lost River as the

cradle of a civilization preceding the Indus Valley and

finally water resources specialists would like to locate

the buried channel of the river and develop it as a

groundwater sanctuary. It is not then surprising that

there is tremendous active interest today to search for a

river, which disappeared thousands of years back.

Background

Rigveda describes the birth and glory of the

Sarasvati River. God Indra was praised by the Rigvedic

sages for killing the serpent demon Ahi with his

Thunderbolt and releasing the waters held by the demon.

They say Oh Indra On your being born and with fear

of your rage, heavens trembled. Huge mountains were

fearful and river waters started flowing moistening the

desert. Oh Indra You struck down barriers and broke

open mountains.

In fact, Rigveda mentions release of seven rivers:

Sarasvati, Sutlej, Chenab, Ravi, Jhelum and Indus, but

gives pride of place to Sarasvati as the biggest and most

majestic of all. Whereas all the others are still major

rivers in Northwest India and Pakistan, Sarasvati

dwindled down to a small monsoon rivulet and is a mere

tributary to a small river Ghaggar that disappears into

the sands of the Thar Desert.

The question is whether it was the melting of the

glaciers at the end of the last ice age ten thousand years

back or whether it was the tectonics that was responsible

E-mail: [email protected]

0236-573112003/USD 20.00

2003 Akadémiai Kiad6, Budapest

for the release of the seven rivers. The Rigvedic descrip

tion of the sudden appearance of the rivers following the

breaking up of mountains distinctly points out tectonics

being responsible for the birth of Sarasvati and other

rivers. Glacier melting would have taken thousands of

years for the river to attain the Rigvedic description of

its majesty and its tempestuous roar while cascading

down the Himalayan slopes and reaching the ocean.

Let's look at a brief chronology of events in

Northwest India2 during the Holocene (extracted from

cited reference) given in Table 1.

The birth of Sarasvati probably occurred around

6000-7000 BP.

The flow in the river started dwindling by about

4000-3000 BP. The epic Mahabharata refers to it as a

sluggish river, meandering and migrating. The Puranas

give its place of birth as Plaksa Prasravana (lower

Himalayas) and disappearance as Vinasana (Rajasthan).

These are similar to the source and place of

disappearance of the present day Ghaggar River. They

also refer to its flow through a series of lakes towards

the end of its life.

How did Sarasvati disappear

Though the wet c1irnate ended around 4000 BP in

large parts of Northwest India, it does not fully explain

the disappearance of the Himalayan River Sarasvati.

Something catac1ysmic happened around 3000 BP. It

could be tectonics and rise of the Aravali hill range. This

drastically changed river drainage pattern of Northwest

India. Desertification must have preceded the tectonic

disturbance. Ancient texts refer to the river as flowing

into the desert.

Tectonics3 must have cut off the main tributaries

Jamuna and Sutlej from Sarasvati. Sutlej migrated west

and joined Indus whereas Jamuna migrated east and

joined Ganges near Allahabad.

A combination of tectonics and onset of aridity

might have caused the disappearance of Vedic Sarasvati.

Akadémiai Kiad6, Budapest

Khnver Academie Publishers, Dordrecht



S. M RAo:USEOFISOTOPESNSEARCHFLOSTRIvER

ble 1 . Br ie f c hr on olog y o f e ve nts in Nor th we st I nd ia

Period

HP

10,000

8,000

7,000

6,000

5,000

4,000

3,000

2000

Events

End oflast ice age/ Advent ofwet phase

E nd of a ridity

W et s pe ll-b re ak u p o fHimalay as tec to nics )- re le as e o f s ev en r iv er s Sa ra sv ati + )

R iv er s in M l f lo w- ag ricu ltur e c omme nc ed

Sa ra sv ati v alle y c iv iliz atio n a t its h eigh t a rc he olog ic al s ites )

E nd of we t c 1ima te

Tect onics - uplif t of the Aravali hill range - Sarasvat i f low di srupted before being l os t

Ar idit y i n I ndus val ley- tectoni c act ivity i n ll th/13th cent ury

Search

Search for the location of the buried channel of the

Lost River has been going on for more than a hundred

years. Max MUELLER S translation of the Rigveda

appears to have set the trend. Two geologists,

R

D.

OLDHAM 1886)4 and C. F. OLDHAM 1893)5 of the

Geological Survey of India were probably the first to

independently look for the buried channel in the Thar

Desert in late nineteenth century. They were not sure .

whether they had located the Sutlej, the Jamuna or the

Sarasvati. They supported the view that the

disappearance of the river was more related to tectonics

rather than reduction in rainfall.

More than 1000 pre- Harappan and Harappan

archeological sites located along the dry Ghaggar and

Hakra riverbeds is further evidence of the existence of a

mighty river in the pasto

With the availability of new technological tools like

remote sensing and isotope geochemistry, there is

resurgence of enthusiasm to search for the Lost River

Sarasvati) in the recent decades.

Remote sensing

There is an obvious advantage of looking at any

terrain from a height. Higher one goes up and looks

down and has tools of high resolution, better is the

chance to identify discontinuities. Aerial photography

was used in the sixties. LANDSAT and IRS satellite

imageries were made available from the seventies.

Palaeochannels are usually associated with dense

vegetation and are detectable with multispectral optical

sensors. Mineral deposits on the surface interfere with

this procedure. Also large palaeochannels of interest are

buried quite deep and for detection of these microwave

remote sensing is a better option. Even here fainter the

signal, greater attention need to be paid for interpretation

of data.

6

Advanced facilities in remote sensing satellites

enabled the Indian Space Research Organisation and

other agencies detect a number of palaeochannels,

undetected earlier.5 The Rajasthan desert is seen strewn

with buried channels. Which one is that of the Lost

River/Sarasvati?

The Ghaggar - Hakra - Nara dry riverbed extending

from Ganganagar district in Rajasthan, entering Pakistan

and reentering India at Tanot in the Jaisalmer district

attracted special attention. Remote sensing detected two

courses6 in the Ganganagar district; one westward

towards Fort Abbas in Pakistan and the other in

Southwest direction towards Khangarh in Pakistan. The

SW course enters India at Tanot in the Jaisalmer district

of Rajasthan along the Indo-Pakistan border. Here again

it has two branches, one north of Tanot and the other

14 km south of Tanot. It is the latter, which generated

maximum interest. In the Kishangarh - Ghantiyali

Ghotaru region Fig. 1 through which it passes, fresh

groundwater occurs at a depth of 30 m and below, dug

wells do not dry up in sunnner and the water level in the

tube wells does not go down even after good pumping

activity. This region was thus selected for isotope study.

The hydrogeological formation comprises

Quatemary alluvium covered with thick sand dunes. The

water table, as mentioned earlier, is very deep. The sand

dunes are predominantly transverse oriented in the NW

SE direction. There is no conspicuous drainage system.

The interdunal depressions and fiats are the sites for

scattered settlement, vegetation and used as routes for

travel through the region.

Isotope stndy

A brief description of the basis for the use of isotope

techniques in groundwater studies, with special

reference to the present study, is as follows.

Water H20) occurs in several isotopic forms, the

important ones being 1HlH160 most common),

lH2H160 DIH 150 ppm), lH2l80 -2000 ppm) and

lH3H160 in the range of 10-16 to 10-18). The

superscript refers to the mass number of the atom.



S.M RAo: USE OF ISOTOPES IN SEAReR OF LOST RIvER

JO •

STUDY AREA

sru v AREA

JAISA~MER

N

.AS.UlAR

~

8 5

015

3 0 K m • •

ig

1. Location map of the studyarea6

ble

2. Results of analyses of sorne representative groundwater samples from Jaisalmer

Location

*DW/TWIHP

E c

IlS/cm

180,0/00

H.,TU

4e age in years

uncorrected)

DW

330

7-5800

TW

500

5.6

0.5000

DW

1005.7

0.5

500

DW000

6.30.5000

TW

7006.60.5

500DW800

6.00.5000W

900

6.20.5

000

TW

600

3.40.52000 DW0606.0 TW740

6.20.5

9000TW300

6.9

0.53000

DW

700

6.4

000

TW

6006.30.5

3000

W

400

<0.5P4005.00.5000DW

380

6.0500

DW400

6.5000

7



s

M RAo: USE OF ISOTOPES IN SEARCH OF LOST RIVER

The isotopic composition of the groundwater

depends on its origin and any evaporation it had

undergone before entering the ground. 2H and 180 are

stable isotopes like IH and 160 and their concentrations

are indicated as per mille 0) deviations from Standard

Mean Ocean Water SMOW) and represented as 82H

and

8180.

3H tritium) is a radioactive isotope produced

in the upper atmosphere by cosmic radiation. 1ts

concentration is given in tritium UllÎts TU). 1 TU

1

atom of tritium in 1018 atoms of hydrogen). Since it is

relatively short lived T I2

12.3 y), its absence indicates

that the water is not of recent origÎll. ln addition

carbonates and bicarbonates dissolved Îll water have

radioactive 14C, also produced naturally in the upper

atrnosphere by cosmic radiation. Carbon-14 values are

given as percentage Modem Carbon pMC).

Groundwater ages are then calculated using the half-life

of 14C T I2

5730 y). Since carbon in water may

exchange with carbon in the aquifer matrix, 14C ages

need to be corrected suitably. Uncorrected ages are still

valuable to identify palaeowaters, which are thousands

ofyears old.

The objective of the isotope investigation of the

selected portion of the buried channel Fig. lb),

supposed to be oflhe Lost River, was to characterize the

shallow and deep ground waters, determÎlle their ages,

identify their sources of recharge and confinn headwater

connection, if any in the Himalayas.

Results

A large number of samples from dug wells and tube

wells have been analyzed7 for their isotopic and

chemical composition. The reduced water levels vary

from 62 m in the north to about 40 m in the south

showing the flow in the NE-SW direction. The tube

wells have screens at varying depths normally in the

range of 73 to 150 m below the surface. Both the dug

wells and the tube wells are in the same hydrogeological

regime except that the tube wells represent deeper

horizons with the consequent effect of stratification.

Chemically, both dug weIl and tube weIl waters are

similar and evolve towards Na-CI type. Table 2 gives the

data for sorne representative samples.

It is seen that the shallow and deep waters have

similar EC and stable isotope composition. The

8180

values cluster around -6 0 and the tube well samples

fall on an evaporation line, which intersects the Meteoric

Water Line MWL) at the 8180value of about -9 0. We

may recall that the river was reported to have formed

into a series of lakes towards its last stages. This

explains the evaporation seen in the stable isotope

composition. The source value of 180 is enriched

compared to the 8180 values of other Hirnalayan rivers

of glacial origin like Chenab8 -12 0) and Ganges

Ganga)9 -10 0).

8

The tube wells as well as most of the dug wells have

negligible tritium indicating absence of modem

recharge. Sorne dug wells, however, have traces of

measurable tritium showing sorne component of recent

recharge.

Carbon-14 data indicate that waters are several

thousands of years old. The dug well waters have 14C

uncorrected ages of 5000 to1800 years. The youngest

waters at Dharmi kua are weIl outside the buried channel

and have more depleteci180 and measurable tritium. The

tube well waters, on the other hand, have 14C

uncorrected ages of 22000 to 6000 years. Here again, the

oldest waters at Sadewal, which is weIl outside the

buried channel, have enriched 180and are highly saline.

The isotope data thus agrees reasonably well with the

course of the buried channel identified by remote

sensing. There is a trend of increase in the apparent 14C

age of groundwater from Kishangarh to Ghotaru

indicating that the ground waters are slow moving with a

speed ofless than 5 rn/y.

From the above observations, it may be concluded

that the isotope data when interpreted along with the

available ground data and remote sensing information

and the descriptions in ancient lndian texts supports the

view that the buried channel in the Kishangarh

Ghantiyali - Ghotaru sector could be part of the Lost

River. The buried channel waters are thousands of years

old and appear to move slowly in the aquifer system.

The aquifer appears to have been recharged when the

river was flowing. No modem recharge is apparent. But,

the fact that the groundwater levels remain steady after

copious exploitation indicates continued headwater

connection. The stable isotope composition indicates

that the Lost River originated at an altitude; probably in

the lower Himalayas Shivaliks) and the water had

undergone sorne evaporation before recharging the

aquifer.

sotope study on the branch entering akistan

It may be recalled that the remote sensing detected

two courses of ancient channel of Ghaggar-Hakra-Nara

riverbed entering Pakistan from Ganganagar: one

towards Fort Abbas and the other towards Khangarh.

The latter one reenters lndia at Tanot and the isotope

study on that branch is described above.

GEYHand PLOETHNER10carried out an isotope study

on the Fort Abbas-Fort Mojgarh sector in the Cholistan

part of the Thar Desert along the old bed of the Hakra

another name for Ghaggar) River. The observations and

their interpretation are briefly as follows: Fresh

groundwater ~1000 mg/l) occurs at a depth of 50 m

with an aquifer thickness of 100 m embedded on either

side by brackish to saline water.



S.M RAo: USE OFISOTOPESIN SEARCHOFLOSTRIvER

o

24

----;. ..

2H= 6.44

0180

-

4 4

t=

0.75, n

=

7)

2

0

ugwell

• Tubewell

. Precipitation

•

and pump

MWL

TW samples

2

<0

cF-

NI

t<:>

4

6

8

1

8

6

ig 2. (52H--8 180 plot of Jaisalmer samples

Groundwater; fresh, brackish or saline has no

measurable tritium (as in Jaisalmer study).

Stable comp< l sition (8180=-5.7 to -4.20/00 and

82H=-44 to -37 0) is enrlched compared to Jaisalmer

samples. The stable isotope values faH on an evaporation

line with a slope of 4.8 and the line intercepts the

Meteoric Water Line at 8180=-7.4 0 (Fig. 2).

Interpretation is that the fossil groundwater was

recharged as seepage from the ancient river under

similar climatic conditions as today.

The groundwater ages, their stable isotopic

composition including the evaporation signature are

broadly similar to those found in the Jaisalmer branch of

the buried channel.

onclusions

The broad conclusion drawn from the remote sensing

and isotope studies and from the references in the

ancient texts is that the Kishangarh - Ghantiyali

Ghotaru section of the palaeochannel in the Jaisalmer

district of Rajasthan could be part of the Lost River

(legendary Sarasvati River?). So also is the Fort Abbas

Fort Mojgarh sector of the ancient Hakra bed in

Pakistan. More needs to be done to cover the entire dry

bed of the Ghaggar - Hakra - Nara system since the

search for the Lost River is far from complete.

eferences

L B. P. RADHAKRISHNA, S. S. MERH (Eds), Vedic Sarasvati,

Evo1utionary History of a Lost River in Northwestem lndia,

Memoir Geo1ogical Society oflndia, Vol. 42, 1999.

2. V. SRIDHAR, S. S. MERH, J. N. MALIK, Vedic Sarasvati,

Evolutionary History of a Lost River in Northwestem lndia,

Memoir Geo1ogical Society oflndia, Vol. 42,1999, p. 187

3.

K.

S. VALDIYA,Resonance, 1 (1996) No. 5, 19.

4. R. D. OLDHAM,J. As iatic Soc. Bengal , 55 (1886) 322.

5. C. F. OLDHAM,J. Royal Asiatic Soc. (N.S), 34 (1893) 49.

6. A S. RAJAWAT,C. V. S. SASTRY,A NARAIN, Mem. Geol. Soc.

lndia,42 (1999) 259.

7. A. R. NAIR, S. V. NAVADA, S.

M

RAo, Mem. Geol. Soc. lndia,

42 (1999) 316.

8. S. M RAo, S. K. JAIN, S. V. NAVADA,A. R. NAIR, K. SHIVANNA,

Proc. lntern. Symp. on the Use of Isotope Techniques in Water

Resources Development, IAEA, Vienna, 1987, p. 403.

9. S. V. NAVADA,S .M RAo, Isotopenpraxis , 27 (1991) 380. _

10. M. A GEYH, D. PWETHNER, Applications of Tracers in Arid

Zone hydrology (proc. of the Vienna Symp.), IAHS Publ. No.

232, 1995, p. 119.

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use of isotopes in search of lost river, journal of radioanalytical and nuclear chemistry, vol. 257,...

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