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PALAEOCHANNELS AND THEIR RECHARGE AS DROUGHT PROOFING MEASURE

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					  PALAEOCHANNELS AND THEIR RECHARGE AS DROUGHT
  PROOFING MEASURE : STUDY AND EXPERIENCES FROM
           RAJASTHAN, WESTERN INDIA .

          A.K.Sinha * , K.S. Raghav # and Anoop Sharma*
  *Environmental geology Lab, Department of Geology, University of
                     Rajasthan, Jaipur 302004.
    Email: sinhaaa@sancharnet.in and sinha_1415@hotmail.com
        # Geological Survey of India, Western region, Jaipur
ABSTRACT

Rajasthan is India’s largest state. Major part of this country fall in arid to semi arid
hydroclimatic zone and suffers due to drought frequently fastly eroding the coping
capacity and economic potential of the people and severely impacting the bare survival
needs of the people including food availability , safe drinking water and adequate
nutrition .

As the every cloud has silver lining so the findings of the of Palaeochannel provides an
array of hope for the survival of the humanity and livestock in this part of the world in
view of the recurring onslaught of the drought menace. Palaeochannels belong to past
riverine environment which are today found in form of the geomorphic signature in a
location representing drainage, streams , rivers which were flowing either ephemeral or
perennial during the past time and now stand , either buried or lost and shifted due to
tectonic , geomorphic as well as anthropogenic activities and climatic vicissitudes .
Numerous Impression of such palaeochannels are present in this part of the world .

In the present paper water prospect of palaeochannel as well its recharge prospects by
means of rainfall –runoff water as well as canal water has been discussed. The study shows
that the palaeochannel are not only having potable quality of ground resource which is
manifested in the comparative yield of the wells as well as chemical study of the water
samples but their favorable hydrological conditions revealed by the Resistivity survey points
toward their being good rechargeable aquifer

 The remote sensing study supplemented by ground checks and Resistivity Survey has
identified Palaeochannels in the semiarid to arid regions of Rajasthan, India which have
very favorable geohydrological conditions and are amenable to recharge by rain water
harvesting techniques as well as imported water through canal quite economically and
environmental friendly way..The recharge would not only further augment the ground
water availability in the region which may be used to mitigate the adverse impacts of the
drought but may also rejuvenate the lost river and ephemeral river system leading to
regeneration of the deranged ecological system.

Further , India receives a rainfall of 4000 billion cubic meter every year out of which 1869
billion cubic meter appears as surface run off in the various river basin of the country and
about 432 billion cubic meter goes to the replenishment of the Groundwater resources and
the remaining are lost to sea as run off. Even if part of the run off lost to sea is conserved
on land in identified natural storage such as Palaeochannel as well as in ephemeral river
basin it would considerably ease the problem of arid region and would act as effective
drought proofing measures in arid to semi arid regions.


INTRODUCTION

There is growing concern for the depleting water resources and increasing frequencies of
drought all over the globe . The SCOPE- an international body survey reveals that water
scarcity is the second most (Table-1) important environmental issues next to Climate


Table –1: Major Global Environmental Issues


Change threatening humanity .According to IWMI Indicator of relative water Scarcity ,
by 2025 , 44 percent of the world’s population will leave in countries with physical water
scarcity and 26 percent will leave in countries with economic scarcity ( Fig-1). There has
been reduction of about water user sector to grab the maximum share and benefit out of the
depleting and deteriorating water regime.

40 percent decline in per capita water availability on global basis taking 1970 as baseline.
Various agencies and individuals at local , national , regional and global level have
forewarned us of worsening water scenario at local, national, regional and Global level
mainly due to population explosion as well as imbalanced and unhealthy competitions
among various

               Fig-1: IWMI indicator showing Relative water Scarcity by 2025

Notwithstanding the prediction of the many agencies , the Water Scarcity in fact has started
unfolding up in arid regions of India ( Sinha 2001) even now . There is considerable
decline in per capita availability of water ( Table- 2) . The worst affected regions( Fig-2) are

                       Table-2: Per Capita Water Availability


YEAR           POPULATION                          PER CAPITA WATER AVAILABILITY
               (In Millions)                       ( In Cubic Meters)
1951           361                                 5177
1955           395                                 4732
1991           846                                 2209
2000           1002                                1865
2025           1393 ( Projected )                  1342
1.   East Flowing rivers basin area between Mahanadi and Pennar
2.   East Flowing rivers between Pennar and Kanyakumari
3.   Sabarmati basin and
4.   Inland drainage basin in Rajasthan ( Western India )

The present paper deals with the possibility of the augmenting water resources through
exploiting and recharging the palaeochannels in the Rajasthan

RAJASTHAN SCENARION

Rajasthan is the largest state of India having geographical area of 342239 sq km . It is
situated in the western part of India . It is driest state having only 1.15 % of the total water
resources . The state enjoys semiarid to arid climate conditions ; the aridity increases
westward and is witnessed as development of Thar desert and also salt lakes /depressions .
The state occupies a wide spectrum of geomorphological features such as Aravalli hill
ranges , Eastern plains , Vindhyan –Deccan plateau and western sandy dunal landscapes (


                         Fig-2: Present Water Scarcity regions of India



Thar desert ). The average annual rain fall has been 416.15 mm during the last 30 years .
The depth to water ranges from 1.7 to 27.87 mbgl( Jan 2000). The region lack perennial
source of water and more than 70 % people depend upon ground water and remaining on
canal and impounded water.

The thirty one out of thirty two districts of the state has been under the drought which has
drastically affected this part of the world both ecologically and economically so much so
that food and drinking water availability has reached to its lowest ebb. Ground water table
has shown widespread decline through out the state at the rate of 10 to 40 cm per year.. As
the deleterious effects of water resource depletion and pollution and its consequences are
surfacing out, a variety of responses are being forged to mitigate or even reverse these . One
such response gaining popularity in the region is Rainwater Harvesting. Despite large
number of dams and reservoir in India 1150Km3 of its rainwater precipitation still run off to
the seas annually in the form of rejected recharge. If a fraction of this can be stored
underground in an appropriate reservoir / storage system ,groundwater availability could be
enhanced significantly which may provide great succor to semiarid and arid regions of
western India which are highly water deficit .The growing incidence o f surface water
pollution and enhanced dependence on ground water warrant the need for the search and
development of aquifer to enhance the storativity of the rain fall – run off and imported
water through canal which may serve as source for the artificial recharge .
PALAEOCHANNELS

 Every cloud has silver lining and so the finding of the palaleochannels by various workers
((Ghosh et al 1979, Bakliwal et al 1983,Yashpal et al 1983, ,Ramasamy et al 1991 ,
Rakshit & Sinha1997,Raghav& Sinha1998 ,Raghav 1999, Raghav & Sinha 1999) ) have
unfolded new vistas and provide a new array of hope for the survival of the humanity and
livestock in this part of the country in view of the recurring onslaught of drought
menace.

Palaeochannels /Palaeodrainage / Lost River / Burried River are typical geomorphic
features in a location representing drainage streams , streams , Rivers, rivuletes which were
flowing either during the past time and now stands either burried or lost or shifted due
(Fig-3) to tectonic , geomorphological , anthropogenic process / activities as well as
climatic vicissitudes . They appear in plan as linier / curvilinear signature and shape
on Remote Sensing data products. However various definition of Palaeochannel has
emerged . Some of which are as follows:

1.Palaeochannles are the drainage/rivers / streams which were flowing either ephemeral or
perennial during past but now these are lost due to tectonic activities, climatic changes and
geomorphic activities.
2. Palaeochannles are the drainage/rivers / streams which were flowing either ephemeral or
perennial during past time but at present time these are lost due to internal ( tectonic
activities ) and external activities ( climatic , geomorphic and anthropogenic )

3. Palaeochannels are the older river courses which were buried due to sedimentation .

5. Palaeochannels are the remnant scars of the shifting of the rivers such as Yamuna ,
   Sutluz rivers.


                       Fig-3: Palaeochannels due to Shifting of Rivers



EVIDENCES IN FAVOUR OF PALAEOCHANNEL


Initially for long time the inscriptions in mythological and historical literature provided clue
about the existence of such past river system. However with the evolution in the thought
processes and technological innovation many new evidences have emerged supporting the
existence of river system in the past. There are many Mythological , Archeological ,
Geomorphological , Geological , Geophysical and Remote sensing evidences which points
toward presence of well integrated drainage network in the Thar desert in recent past.
However the evidences derived from geological ,Geophysical and Remote sensing methods
have proved beyond doubt the existence of number of palaeochannels .
Geological Evidences

Geological record indicates that during Late Pleistocene glaciating waters of the Himalayas
were frozen and that in place of rivers there were only glaciers , masses of solid ice . At the
outset of Holocene as climate became warmer the glaciers began to melt and break up and
the frozen water held by them surged forth in great floods , inundating the alluvial plains in
front of the mountain. The release of pent up water gave rise number of rivers flowing
through the plains in front of Himalayas.

The river deposits are identified and characterized on the basis of their typical geological
and physical character. Following is one of the cross section( Roberts 1994) showing a
typical river deposit ( Table-2) from Palaeochannel (unit 4-6)

Table-2: A typical litholog of Palaeochannel
(Pre-palaeochannel)

Unit 1: light grey-yellow lake marl (maximum thickness >150 cm)
Unit 2: Dark (?organic) marl (max. 20 cm)
Unit 3: Backswamp clay (max. 160 cm)
(Channel fill)
Unit 4: Grey clay with manganese staining (max. 30 cm)
Unit 5: Matrix supported gravel, locally part-cemented (max. 30cm)
Unit 6: Fluviatile silts, sands and gravels, coarsening from west to east (max. 220 cm)
Sub-unit 6a: Red-brown silts
Sub-unit 6b: Buff silts
Sub-unit 6c : Grey to orange fluviatile sands containing large freshwater bivalve shells
Sub-unit 6d: Fluviatile gravels
(Post-palaeochannel)
Unit 7: Alluvial clay with manganese staining (max. 230 cm). This upper alluvium caps all
the underlying units.

Geophysical Evidences

The geophysical sounding carried out in one of the inferred palaeochannel has also revealed the
presence of typical coarse sand gravel bed which are alluvial in nature which has characteristic of
being a good aquifer .

Hydrogeological evidences :

Lunkaransar, Didwana and Sambhar, the Ranns of Jaisalmer, Pachpadra, etc. are a few of
the notable lakes, formed as a result of the changes; some of them are highly saline
today,the only proof to their freshwater descent being occurrences of gastropod shells in
those lake beds. Mr. Oldham accepted that there have been great changes in the
hydrography of Punjab and Sind within the recent period of geology. Wilson has mentioned
about the Sotar valley where “the soil is all rich alluvial clay such as is now being annually
deposited in the depressions Freshwater pools are normally found encircled by saline water
in palaeochannel zones.
Remote Sensing Evidences

The Advent of Remote Sensing technology could throw much light on the subject. With this
technology it has now become possible to discover , delineate and understand the
palaeochannel in regional context and in integrated manner.

A remote sensing study of the Indian Thar desert reveals numerous signatures of
palaeochannels in the form of curvilinear and meandering courses, which is identified by the
tonal variations ( Bakliwal et al 1988). Its initial course flowed close to the Aravalli ranges
and the successive six stages took west and northwesterly shifts till it coincides with the dry
bed of the Ghaggar River.

Yash Pal et al.(1980) found that the course of the river Saraswati in the states of Punjab,
Haryana and Rajasthan is clearly highlighted in the LANDSAT imagery by the vegetation
cover thriving on the rich residual loamy soil along its earlier course. Digital enhancement
studies of IRS-1C data ,combined with RADAR imagery from European Remote Sensing
satellites ERS 1/2, identified subsurface features and recognized the palaeochannels beneath
the sands of the Thar Desert. A study of NRSA, based on satellite derived data, has revealed
no palaeochannel link between the Indus and the Saraswati, confirming that the two were
independent rivers; also, the three palaeochannels, south of Ambala, seen to swerve
westwards to join the ancient bed of the Ghaggar, are inferred to be the tributaries of
Saraswati/Ghaggar, and one among them, probably Drishadvati. Digital enhancement
techniques using high resolution LISS-III data of IRS-1C satellite, together with pyramidal
processing, identified two palaeochannels trending NE-SW in Jaisalmer districts.


WATER RESOURCE POTENTIALITY OF PALAEOCHANNELS

The palaeochannels considered as lost drainage are still having under flow of ground water
evidenced by abnormally high pumpage discharge,fresh to low saline quality in comparison
to water occurring in adjoining nonriverine environment and are also comparatively older
in character ( Nair et al 1997) .This is a premise on the basis of which efforts are being made
to trace the coarse of the Saraswati river- one of the very famous long river lost in the Thar
Desert. Such palaeochannels are being looked upon as possible reservoir of ground water. If
such basins are further identified and integrated, it is possible to rejuvenate it through
recharge by Rainwater harvesting as well as by canal system. Such measures may initiate a
blue revolution in the Thar desert. It is obvious that palaeochannels have comparatively
better prospects of water storage in comparison to adjoining non-fluvial zone. The isopach
map in case of other ephemeral basin( Sinha et al 2001) has revealed a comparatively
thicker unconsolidated sedimentary pile which has potentiality of holding greater volume of
water and as such on the basis of similar analogy palaeochannels may also be looked upon
as comparatively thicker sedimentary pile having potentiality of holding larger volume of
water to meet the demand during the drought situation. However there is need to identify ,
delineate and estimate the sedimentary thickness of all such paleochannels for precise
planning of the water resources development and utilization program to effectively counter
the menace of the drought.
The palaeochannels of Quaternary may become major source of ground water in this
region. Quality and semi-quantitative data of availability of ground water from few
paleochannels of the region are tabulated herewith ( Table-3 )


                              Table 3: Distribution of sub surface water.

       Source         Occurrence              Aquifer            Reservoir         Depth        Quality
       Ground   i      Sand dune sand   Palaeochannel F1          Good          35 m to 50m     Sweet
        water          sheet
                ii     Abandoned        Palaeochannel F2      Moderately good   15m to 30 m      Sweet
                       playas and                                 Good          30 m to 40 m    Brackish
                       lakes
                i      Sand             Palaeochannel F1      Moderately good   10 m to 15 m      -do-
                       dune/sand                                  Poor          2 m to 5 m       Sweet
                       sheet
                ii     Playas and       Silty sand and Clay      Very poor      1.5 m to 2.5m   Brackish
                       lakes
                iii    Rivers           Channel deposits           -do-                          Sweet


Quality of Water in Palaeochannel


Further ,in order to assess the quality of the ground water in the palaeochannels a total of 37
water samples were collected from dug wells confined to different lithological units. The
geochemical analyses of water samples are carried out and TDS, Ph, CO3, HCO3,
Cl, SO4, NO3, F’ were calculated. Total hardness as CaCO3 and Ca++, Mg++, Na+, K’, SiO2
and B were determined. The epm % values and atomic ratio values of Na+ / K+ Cl+/HcO3+,
01-/F’ Cl-/So2-; Na+/Mg+; Mg+/Ca+ and total alkalinity of these samples were calculated .The
percentage values of all these sample were plotted on the piper diagram which reveals that
most of the water confined in abandoned playas and rocky pediplain areas is NaCl type. The
water of the sand dune field areas is NaHCO3, type.

The quality of water is potable and fit for irrigation purposes as well. No doubt it holds much hope
for future as huge untapped reservoir of fresh water resources


PALAEOCHANNEL- PROSPECTS


In view of the adverse prediction of the various international and national agencies about the
availability of the water resources during 2025 to 2050 and the surfacing water scarcity
conditions in semi to arid region of the world including India , the delineation and
identification of palaeochannel may be highly useful from the following point of view:

i)         source of the ground water , in general of good quality
ii)        possible locales for rainwater harvesting
iii)       possible locales for artificial recharge using excess of canal water etc
SUMMARY AND CONCLUSION


There are overwhelming evidences from various sources mainly from Satellite Imagery
interpretations as well from archeological , geological , and Geophysical evidences that the rivers
with well integrated drainage once flowed through Thar Desert , the remnants of which are found
today as palaeochannels . These Palaeochannels are not only the abode of potable water but alos
posses high volume of storativity which if utilized by recharging them by catching each and every
droplets of the rainfall-runoff component and imported water through existing canal , may provide as
relieve to drought affected people and livestock. Such measures may be adopted towards drought
proofing in this state . These palaeochannels are not merely the imprints of the lost channels but are
the riverine monument which need to to be understood in greater details and possibly stands out to
provide not only needed water resource to the society but lesson too to modern humanity for
taking proper care of their existing riverine environment and to take suitable measures to prevent
them from turning into palaeochannels.


REFERENCE

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Bakliwal, P.C. and Grover, A.K. 1988. Signature and migration of Sarasvati River in the
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Ghose, B., Kar. A and Hussun, Z., (1979); The lost course of the Sarasvati river in great
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Nair A.R,Navada S.Vand Rao S.M (1997) Isotope Study to Investigate the Origin and
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Raghav, K.S. (1999): Evolution of Drainage Basins in parts of Northern and
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