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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
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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.
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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
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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.
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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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