CHAPTER 6 GEOPHYSICAL PROSPECTING - …shodhganga.inflibnet.ac.in/bitstream/10603/61723/13/13_chapter 6.pdf · CHAPTER 6 GEOPHYSICAL PROSPECTING 6.1 IMPORTANCE Geophysics, ... (Fig

CHAPTER 6

GEOPHYSICAL PROSPECTING

6.1 IMPORTANCE

Geophysics, in recent times, has reached a place of vital importance to thescientific development and protection of the World's precious natural resources includinggroundwater Very accurate and practically useful results can be obtained when geophysicalmethods are applied with an-additional understanding of the geological and hydrologicalconditions of any area. The main geophysical methods which have been used to solvesome of the problems of hydrogeology are the electrical, seismic, gravity and magneticmethods. Among these, electrical resistivity methods are widely used for both regionaland detailed surveys because of their greatest resolving power, low expense and widerange of field applicability. Hence, electrical resistivity method has been used in the presentstudy.

6.2 ELECTRICAL RESISTIVITY METHODSElectrical resistivity survey provides many basic information to the hydrogeologist,

like depth to water table, depth to the basement topography - in hard rocks and incoastal terrains, thickness of weathered layers, detection of fissures, fractures and faultzones; depth, thickness and lateral extent of aquifers in sedimentary terrain; structuraland stratigraphical conditions, formation characterstics, quality of groundwater in termsof dissolved salt content, location of the zones of saltwater encroachment in coastalareas or locations of freshwater pockets in saline and or brackish water environments.

Electrical resistivity techniques have been used in this work in order to

I. determine the hydrogeological, lithological and structuralcharacteristics of the area,

2. to determine the nature and extent of promising potential

124

FIG- 6.1

BASIC PRINCIPLES OF ELECTRICALRESISTIVITY SURVEYS :WENNER CONFIGURATION

Table 6.1.Application of electrical methods in solving hydrogeological problems 125

(After Balasubramanian, 1986).

No Groundwater problems Prospecting techniques

1. Determination of subsurface structure of basins

2. Determination of horizontal and vertical distribution ofaquifers and their regional boundaries and correlation

3. Tracing saltwater-freshwater interface in coastal zones

4. Tracing the zones of tectonic deformation affectinggroundwater movement

5. Estimating groundwater salinity

6. Detailed investigation of areas of artificial recharge

7. Tracing groundwater movement

8. Mapping valley fills

9. Mapping permeable zones in unconsolidated formation

10. Mapping thick sediments lying over impermeable substratum

11. Determination of groundwater potential zones in hard rocks

12. Correlation of geophysical and hydrogeological parameters

13. Depth to the groundwater table

yES, DES, FEMS, RIS

yES, DES, FEMS,RIS

yES, FEMS, RIS, 19 EP

yES, E9 RES, RP

yES, FEMS, RIS, IP

yES, E19 RES, RP

SP

yES. FEMS

yES, DES, IP IPVES, EP

yES, RIS, IPVES

yES, EP, RIS, FEMS, 19 RS

VES, IPVES, AS

yES, IPVES, RIS, FEMS

EP : Electrical profiling;

FEMS: Frequency EM sounding;

SP : Spontaneous polarization:

IPVES: Induced polarization;

AP : Radiowave profiling;

DES: Dipole electrical sounding

IP : Induced polarization

RVES: Radial VES

RIS : Radio interference sounding

VES : Vertical electrical sounding

126

aquifers of groundwater,

3. to find out the thickness of saturated zones, depth to the

basement topography and

4. to delineate the saltwater - freshwater interlace along the

coast.

Fig. 6.1 shows the basis of electrical resistivity technique. A known current (I) is

passed into the ground through two metal electrodes (c 1 and c2).The potential difference

(AV) is measured between two more electrodes called potential electrodes (P 1 and P2).

The ratio'/1 gives the resistance (R) and multiplying R with the geometrical factor (K) of

the electrode separation, the apparent resistivity 'pa' which is inverse of conductivity, of

the ground,can be determined.

The value of'pa' corresponds to the true resistivity of the formation if the ground

is homogeneous and isotropic.When it is obtained from the measurements over a layered

or heterogenous ground, it is only an apparent resistivity and is denoted as 'pa', the

quantity being used in the interpretation of electrical methods.

6.3 BASIC PRINCIPLES

Many types of electrical methods are employed to solve different geological

problems (Bhimashankaran, 1977 ; Patangay, 1977) which are listed in Table 6. I. It

could be seen that most of the groundwater problems can be solved using the Vertical

Electrical sounding (VES) method. VES data has been used to study the nature and extent

of the promising potential aquifers and to find out the thickness of saturated zone, depth

to the basement topography, and delineate the saltwater - freshwater interlace in the

coastal belt of the basin.

Vertical electrical sounding is called by various names such as 'electrical drilling,

'depth sounding or 'depth probing', in which the measurements of resistivity are made

about a fixed point by increasing the electrode separation in successive steps. With the

expansion of electrical array, the depth of penetration of electrical current is increased

and hence a detailed information on the vertical succession of various conductive zones,

their individual true resistivities and thickness can be obtained.

127

128

6.3.1 Electrode configurations

A few varieties of electrode spread methods are being employed in resistivitymeasurements. The two widely used configurations are (I) the Wenner and (2) theSchiumberger configurations. In the present work, Wenner configuration has beenfollowed. Vertical electrical soundings have been conducted over 335 locations of thisbasin using an AC resistivity meter (Fig. 6.2). The Location index is given in the form ofcolumn numbers and row characters.

The Wenner array is one of the most commonly used electrode arrays fordetermining resistivity. In this layout, four electrodes are equally spaced along a straightline as shown in Fig 6.1 and the surveys are conducted. The distance between twoadjacent electrodes is called the array spacing'a'.The geometric factor (K) for the Wennerconfiguration can be obtained using (Keller and Frischknecht,l 966).

2K= 27ta

1 1 1 1- -+-2a 2a a

6.4 RESISTIVITY OF GEOLOGICAL FORMATIONS

The resistivity of a geological formation varies very widely not only from formationto formation but also within one lithologic unit and is dependent on the

I. density, porosity, pore size and shape of aquifer materials,

2.quality of water encountered in the aquife5

3.distribution of water in the rocks due to the structural andtextural characteristics and

4.the temperature of subsurface environment.

Kollert (1969), Vingoe (1972), Sharma (1976), Telford, et. al., (1976),Bhimashankaram, (1977), Patangay and Murali (1984) have given many comprehensivelists of resistivity ranges for various rock types, minerals and soils. Balasubramanian(1980) tabulated the range of resistivities of common hardrocks and their water bearing

Table 6.2 Hydrogeologic significance of bulk resistivity values.

129

Bulkresistivity

- p.1

<20

50-70

20-30

30-70<10<1

15-600<5

<10

10-20

20-160

0.2-0.8

0.6-5

0.3-0.8

3-6

<19

64-81

57-111

<10

10-2020-60

Aquifer characteristics or significance

Indicates a chloride ion concentration of 250

ppm (aquifer fine sand and limestones)Porosity is the principal determinant of

resistivityPore fluid conductivity dominates/affected

by both water quality and lithology

Affected by both water quality and lithologyDelineates sediments enriched with saltwater

Clay/sand saturated with saltwaterSand and gravel saturated with freshwater

Saltwater or clay with saltwater

Brackish aquifer

Moderately fresh

Freshwater

Clay

Dry sand contaminated

Brine bearing sand

Red clay-

Clay/clay mixed with kankar

Weathered sandstone -

Weathered graniteSaline coastal zone sand (sedimentary)

Clay with or without diffused water-

Freshwater zones

Source

Stewart, etal. 1983.





Zohdy et al. 1974

Zohdy et al. 1974

Arora and Bose 1981

Melanchton et al., 1988

Melanchton et al., 1988

Melanchton etal., 1988

Sathyamoorthy and

Banerjee 1985Sathyamoorthy and

Banerjee 1985Sathyamoorthy and

Banerjee 1985SathyamoorthY and

Banerjee 1985

Singhal 1984

Singhal 1984

Singhal 1984Balasubramaflian etal. 1985

Balasubramanian etal. 1985

Balasubramanian etal. 1985

130

decomposed products of the Peninsular shield. The resistivities of highly weathered,saturated gneisses of Archaean age range from 27 to 120 ohm-mts and of hard, massivecrystalline complex ranges from 200 to 2000 ohm-mts. Dry rocks whether non-porousor porous are practically non-conductors,but the resistivity decreases with increasingamount of pore-water. Unsaturated geologic material will show a higher resistivity thanthe same material saturated with water. Massive rocks with little interconnectedporespaces will have a high resistivity. Clayey sands and gravel deposits that are saturatedwith groundwater of low ionic strength will show a high resistivity. Porus geologicalformations that are unsaturated with groundwater of high ionic strength will have a verylow resistivity. Gilkeson and Cartwright (l983),Sakthimurugan, et. al., (1993) listed theresistivities of geological formations saturated with fresh water and salt water and havebeen updated and shown aslable.6.2.

6.5 METHODS OF INTERPRETATION

An important aspect of any geophysical exploration is the interpretation of data in

terms of subsurface geology. A majority of geophysical problems do not have uniquesolutions since different combinations of geological conditions may give rise to identicalgeophysical anomalies introducing thereby a certain degree of ambiguity in theinterpretation. A more realistic solution of the problem is arrived at, where geological

conditions of the area under investigation are also made use of, while interpreting thedata. This observation is true for electrical resistivity methods as well.

The primary objectives of conducting soundings are to transform the field datainto subsurface geology or hydrogeology and this can be achieved by adopting suitableinterpretation techniques. Depending upon the details required the field data could beinterpreted by (I) qualitative and (2) quantitative methods. Zhody et al (1974) and Patangay

et at (1984) have described the various techniques of qualitative and quantitative

interpretations.

6.5.1 Qualitative interpretation

Qualitative methods help in learning the general information about the geologicalstructure and the changes in the geoelectric sections of an area. Interpretations are doneby preparing isoresistivity maps and sections, transverse resistance maps and specific

a a

Type AP1< P2< P3

Type QP1>1)2> P3

a

131

Type

Type KP1> P2< P3 Pi<P2> P3

Fig 6.3 Types of sounding curves

132conductance maps.

6.5.2 Quantitative interpretations

Methods belonging to this category of interpreting the sounding curves be classifiedas analytical and empirical or semi empirical methods. Analytical methods are basedupon the computation of apparent resistivity values for various electrode separations fora given set of subsurface conditions. The two geoelectrical parameters used in thiscomputation are resistivities and thickness of layers present. Theoretical apparentresistivities have been computed for various combinations of these parameters and albumsof master curves were prepared by Mooney and Wetzel forWenner, Corn paigne GeneraledeGeophysiques, Rijikwaterstat., Dapperman and Orellona and Mooney for Schlumbergerarrays. The usual method of sounding curve interpretation is to match the field curvewith the standard curves and once a match is obtained the layer thickness and resistivitiesare easily determined. This method is known as curve matching technique.

The simplest sounding curves are the ascending and descending type of two layercases. Ascending type curves are obtained where the ground has a two layered structure,with a top soil or weathered layer and a hard and compact basement. Descending typecurves are obtained where there is a top layer overlying a thick clay layer or a saline wateraquifer.

In case of three layered ground structure, four types of sounding curves are possible.(Fig 6.3). If p 1 , p2 and p 3 are resistivities of the three successive layers, the sounding curvewith central low (p 1 > p2 < p3) is denoted as "H" type curve. This type of soundingcurves are obtained generally in hard rock terrains consisting of dry top soil of highresistivity as the first layer; a water-saturated weathered layer of low resistivity as thesecond layer; and a compact, hard rock of very high resistivity as the last layer.

"A" type curves are also obtained in the hard rocks with a conductive top soil. Inthis case, the resistivities of the layers will be continuously increasing as (p 1 < p2 < p3).

Sounding curves showing a maximum peak and flanked by low resistivity values

(p, < p2 > p) are called "K"-type curves. Such curves result from various situations. Inbasaltic areas, where compact and massive traps exist between a top black cotton soiland a lower vesicular basalt. This type of curve is very common. In coastal areas also,

E

10

Ef

133

10 10 100

E

1

10 0 10ELECTRODE SPACING

'a'(m)

ELECTRODE SPACINGa' (M)

FIG. 6 . 4a . VES CURVES OF VAIGAI RIVER BASIN

1OC

10

134

Location: OKKARAPATTIh1 1.7 rnh2 85 rn

)

/at

11011-fl--rn112-fl-rn

100IOfl: NAGARKKUOI

h2m /45-fl-rnh2 0 m

3.6-J'-m

2 144-1'--mt O 1100

Location: PALLAPATTI Location: MEENAKSHIPURAMh1 1.6m h1 2.4mh2 16m 12mP 65-fl-rn 26 .ft_ mi° 4225-fl-rn 260 flrnP3267-rl-m 3437

+

- -10

10

10ELECTRODE SPACING

a' (m)

FIG . 6.4b. VES CURVES OF VAIGAI RIVER BASIN

100

135

10

E

L9100

10

Locat ion: iOfl. KILAVI KULAM

^ h1 1.2m + 2.9m

h2 = 18mh28.7rn

6.5-fl-rn6.5-fl-rn

65 rrnP216.25fl_m

A 9 155-fl-rn I P370-fl-m

t

Location: ANOAMAN

h1 2.4 mAMAGUDI

24 m •1.7 m-fl_rn h2 25.5rn

165-t1m /1 _130rn

/02 6.5-ft-rn

p 161-fl-rn p323fl.m

10 100 10 100

FIG.6.4CVES

ELECTRODE SPACING%Q(m)

CURVES OF VAIGA RIVER BASIN

(I):9 LU0)N

ZwL aJ>()

0

z ©

136

CL N

LL U .—. .

.11

—F—()

LLI

-'-;: ------ £/ =

LU . -i_ 4::• 4T' LnC1

LU 4. • w0

•/;4:4: S,_/ • ,, .,- (I)

:

L.7 • 4.&/

• i\

CL

( (44./:x

o :f•_•'4

• —J C-)•444(

a. w W

4\

El E]r144 ((x. 4.)4 1T4•.1-..-L. .•4\4 '.I \

Lv LLLL

co

• • 4 \ Z \

4 4 '-\

--3

cDIb

0

N

NN

-QC,)coN

0

c0t-

0C,)

N

137

these curves will be encountered due to freshwater aquifer underlying a clayey layer and

overlying a saline zone.

A sounding curve with continuously decreasing resistivity (p 1 > p2 > p3) is called

a"Q" type curve. In coastal areas,where saline water is present, these curves are obtained.

TheVES data of all 335 locations ofVaigai basin have been interpreted and a few of

the sounding curves obtained are shown in Figures 6.4 a through 6.4c.

6.5.3 VIES curve types

The nature oIVES curve depends on the geological and hydrogeological situation

and the maximum electrode spread employed. Qualitative interpretations are also

attempted by preparing a spatial variation map showing the types of curves encountered.

Such maps can clearly indicate the disposition of different resistivity zones with depth.

In this area, four different types of sounding curves have been obtained. Figure 6.5

shows the distributions of curve-types seen over Vaigai river basin.The following points

have been inferred:

I. H - type sounding curves are seen in the form of patches

over the basin. The presence of a highly resistive top soil and

a saturated aquifer zone with a resistive substratum is indicated

by this type of curves.

2. A - type curves are seen in almost all the places of the

basin. This indicates that there is no appreciable aquifer.

media inVaigai Basin,The resistive formation itself is existing

from the surface.

3. Sounding curves showing a resistive intermediate layer

covered by low resistivity beds above and below (p, < p2>

P3) are called as "k" type. This type of curves are seen in a

few places of this area, especially along the river courses, and

boundary between crystallines and sedimentaries. This may

SITE LOCATION CURVE

CODE NAME TYPE

A0801 BodikkamanvadiA0901 PalalyankottalA0902 PachchalmalalYaflkOttalA0903 KendichhamPattlAlOOl Swamlyarpatti80501 ArapaditheVanPattiB0601 KamakkapattlBOTOl GanguvarPattiB0702 KanavaypattiB0801 VadipattiB0802 Pangalappatti80803 ChI nnamanayakkaflkOttalB0901 KodanglnayakkaflPatti

B0902 KotturB0903 NilakkottaiB0904 KattinayakkaflPattiB0905 ManjoothUB0906 OrutattuCO501 KailasaPattiCO502 PeriakulamCO503 VaidyanathapuramCO504 TamaraikulafliCO505 VadugappattiC0601 AlaglriflaYakkaflPattiC0602 KilmangalamC0603 SilvarpattiC0604 ErumalalflaYakkaflPattl

C0605 Bommi nayakkampattiC0606 Devadanappatti

C0701 RanganathaPUramC0702 EluvarpattiC0703 Kil VadippattiC0704 KottarpattiC0705 VeriyappanayakkaflPattl

C0706 PuvampattiC0707 ViralipattiC0708 Sandal yurC0709 PannaipattiC0801 SivaghanapUramC0802 KullichettiPatti

C0803 MuthalaPUramC0804 VI rinayakkaflPattiC0901 MusuvanuthUC0902 PillalyarnattamC0903 KoovanUttUC0904 NakkalUtteC0905 VilampattiC0906 EttliodUC0907 MeenakShiPUramC0908 RamanathaPuramCoga g MalaiyakkavundanPatti

HAHAAAHHHHKHAHKAAAAAAAAAAAHHAHAAAHAAAHAAAAAAAAHHAAA

TABLE 6.3

138

GEOELECTRIC PARAMETERS OF SUBSURFACE ZONES IN VAIGAI RIVER BASIN

THICKNESS(M) RESISTIVITY(ohm-m)

(LAYER - WISE)

1 9 63 270 148 320 490

1 30 7 105 218

1 35 230 150 307

2 11 20 400 573

2 15 20 50 422

2 33 34 238 308

1 12 50 25 201

1 4 40 8217

2 8 58 23 376

2 6 15 5 77

2 45 7 98 160

5 20 79 234 842

2 18 32 64.274

1 3 110 17 568

2 40 90 450 523

2 6 65 24 113 71 130

4 42 46 115 335

1 13 17 43 127

2 48 21 210 292

2 26 12 24 114

2 16 90 225 239

1 13 13 33 257

1 20 90 315 785

1 35 19 48 149

2 45 75 1500 151

3 75 14 280 242

1 7 70 28 535

1 20 260 78 371

2 12 26 91 294

2 15 120 78 371

3 16 24 168 397

2 30 8 320 303

3 75 24 480 451

2 5 240 48 660

2 24 70 175 438

2 60 40 600 478

2 16 21 105 565

2 22 21 48 160 100 352

2 30 54 108 327

3 34 25 175 262

2 50 65 2600 579

2 17 43 430 924

4 18 130 455 724

2 9 25 38 169

2 10 14 49 262

2 3516 240 342

1 14300 150 472

1 7 102 31 533

2 1226 260 437

2 17 50 63 427

2 4518 360 322

TABLE 6.3 contd.


SITE LOCATION CURVE THICKNESS(M) RESISTIVITY(ohm-m)CODE NAME TYPE ( L A V E R - W I S E )

C09 10C091 1Cl 001C1002C1003Cl 101Cl 102C1103C1201C1202C1203C1204C1205C1206C1207C1208C1209C1210C1211C1212C121300201D0301003020030300304D040100402D0403D040400501D050200503005040050500506005070060100602006030060400605D06060060700608006090061000901009020100101002

Kuttel kundu

APallapatti

HAl uguvarpatti

HKalladipatti

AKachchaikatti

HTettur

ARamakkavundanpattl

AValyasippatti

AKonappatti

A

Sembatti

ASukkampatti

AKri shnapuram

H

Palamedu

AChattravel lalapatti

AValalyapatti

A

Mettuppatt I

AMani kkampattl

AVellalyampatti

HParal ppattl

H

Kodangipatti

H

Sarantangl

HMundal (Ikkaralkalam)

H

Karattupatti

AKulasekharapattanam

HBodi nayakkanur

HAnna ikkaralppatti

H

Bodipuram

A

Vazhaiyattupattl

A

Ten I

H

Sukkuvadanpattl

A

Unjarnpatti AMadurapuri VadapuduppattlH

Kunnur A

Kamakshlpuram A

Sallipatti KMelakannakapatti AKadi rayakkavundanpatti A

Kurumbappatti K

Jambulaputtur A

Jakkampattl

H

Sankaramurtipatti

K

AyyannattevaflPattl

A

KovI ipatti

A

Gulapuram

A

RajagopalanPatti

A

Subbulapuram

A

Ambattanpatt i

A

Sitharkalanattam

K

Axyamkenvl thu

A

Mannadimangalam

A

Karuooatti

H

2

23

8 160 291

2

16

65

43 267

1

4

80

40 473

2

10

44 308 508

2

8

50

40 175

1

14

32 112 301

2

7

40 600 110

2

21

50 100 247

3

17

14

70 150

1

12

28

42 224

3

30

16 112 152

4

36

160

80 132

2

18

20 140 299

3

41

8

40 103

1

33

26 260 285

4

22

22 880 370

2

45

18 360 326

24

48

2

1 183

3

32

28 280 342

2

10

75

49 218

3

8

30

15 189

1

1

42

6 308

1

30

7

65 194

1

13

200

14 197

2

18

120

12 105

1

7

30

15 264

1

9

45

20

34 270 221

1

14

16

56 127

1

7

95

38 312

2

26

go 135 360

1

33

25 250 440

2

8

40

16

83

2

38

25 375 379

2

40

120 600 1000

2

5

14

150 158 3600 4000

2

19

54 108 315

1

18

15

75 275

2

20

72

130 415 2700 4500

3

25

17 680 724

1

14

60

30 157

3

39

110 770 600

2

8

26 130 806

1

35

40 280 491

3

9

34 119 380

I

20

25 250 396

2

21

50 250 523

2

58

62 434 591

4

40

120 840 348

50

8 320 179

68

11 440 222

7

19

10

112

TABLE 6.3 contd.


SITE LOCATION CURVE THICKNESS(M) RESISTIVITY(ohm-rn)

CODE NAME TYPE ( L A V E R - W I S E )

01003 Irunibadi H 2 6 26 13 160

01004 Nachchikulam H 1 4 13 2 49

01005 MullIpallam A 4 57 7 102 78

D1006 Sholavandan A 2 9 25 38 169

01007 Tenkaral A 1 21 5 54 220

01008 Pettal H 1 12 20 13 88

01009 Solalkkurlchl H 1 7 15 8 84

01010 Kottakulam (Vadugapattl) A 3 33 9 180 136

01011 Nedungulam A 3 9 7 49 105

01101 Puchampatti A 2 23 20 100 238

01102 Thlruvalavayanallur A 3 42 2 46 35

D1103 Tanlchchlyam H 1 13 42 27 213

01104 Nagarl A 3 2 30 1200 1058

D1105 chittalangudi A 2 24 18 180 341

01106 Kondalyampatti A 3 16 40 140 233D1107 Melachlnnampattl A 2 20 25 175 312

01108 Sanibakkulam A 3 15 17 255 309

01109 Perlya Ilandalkulam A 2 45 27 135 195

01110 Amaraddakl A 2 1 4 168 198

Dliii Alagapurl A 3 27 12 180 258

01112 Kovilpattl A 2 35 33 660 630

01113 Pandi A 2 20 4 152 148

01201 Kallanal A 2 27 4 176 14301202 Errarnpattl A 2 19 7 105 150

01203 Alanganallur H 2 5 39 8 78

01204 Kil Chlnnanampattl A 2 58 12 120 142

01205 Kumaram A 2 23 8 300 232

01206 Manlyanjl A 2 18 7 68 117

01207 Tandalai H 2 3 21 17 149

D1208 Ilavankulam A 4 22 5 200 81

01209 Adanur A 3 27 19 133 206

01210 Muduvarpattl A 2 16 27 54 167

D121i '4avldamarudur A 2 11 15 105 225

01212 Mandlkulam A 2 24 9 135 128

01213 Andaman A 2 24 ii 165 161

01301 Paralkulam A 2 43 11 110 181

01302 Mattur A 2 19 9 90 184

01303 KallandirI A 3 39 11 220 202

01304 Valalyapattl A 1 33 26 260 285

01401 Kidirlpatti A 3 41 24 240 304

D1402 Terkutteru A 2 8 36 180 57

01403 Vallapattl A 2 11 14 98 219

01404 Pudusukkampattl A 2 21 32 48 158

D1501 KarathapullYamPatti A 4 110 26 520 215

01502 Melur A 3 33 16 80 116

D1503 Attukkulam H 1 13 85 26 250

01504 Navinlpatti H 2 8 52 26 268

01505 Vannamparaipattl A 2 8 9 340 372

01506 Sattamangalam H 1 14 42 21 164

01507 Tanlyamangalam H 2 23 8 4 132

01508 Vadakku Valalyappatti A 2 19 28 140 312

140

TABLE 6.3 contd.


SITE LOCATION CURVE THICKNESS(M) RESISTIVITY(ohrn-m)

CODE NAME TYPE (LAYER - WISE)

-E0201 E.Pudukkottal A 2 24 65 163 481 -

E0301 Silamalai H 1 33 85 17 51

E0401 Virapandi K 1 4 23 85 93 580 475

E0501 Sangukonampatti H 1 30 90 27 50

E0502 Ammatelipuram A 2 5 48 21 774

E0503 Ramalingapuram H 5 13 50 15 73

E0504 Okkaraipatti H 2 9 110 11 112

E0505 Chittarpatti H 2 10 36 11 118

E0601 Karisalpatti A 2 21 5 184 233

E0602 Kadir Narasinghapuram A 1 30 10 48 92

E0603 Bodidasampatti A 2 55 46 230 438

E0604 Mekkalarpattl A 2 8 11 440 648

E0701 TlmmarasanayakkanLir A 2 23 140 175 442

ElOOl KachchiraylruppU A 3 25 29 145 328

E1002 Melakkal A 1 14 30 38 201

E1003 Tirumalnattam A 3 32 7 105 87

El101 Paravai H 1 12 32 10 55

E1201 Kochchadl H 2 8 50 10 96

E1202 Vilangudi H 2 15 38 11 26

E1203 Madural H 4 11 38 11 66

E1204 Chlkkandrachavadl A 3 25 2 42 35

E1301 Udaikulam A 2 8 14 21 183

E1302 Mangalakkudi A 2 15 11 165 245

E1303 Ulaganeri A 2 17 9 180 247

E1304 Tatankulam A 2 16 31 39 141

E1305 Sengulam A 2 27 42 84 262

E1306 Sirupullyendal A 2 33 17 170 274

E1307 Pudupatti A 2 29 38 76 236

E1308 Tadankulam A 3 48 17 170 194

E1309 Parayankulam A 2 9 15 53 275

E1310 Podsepatti A 2 58 7 268 151

E1311 Tirumugur H 2 7 28 14 122

E1312 Kodikulam H 2 17 40 20 129

E1313 Mundanayagam A 3 80 10 400 137

E1314 Sivalingam A 1 14 30 60 169

E1315 Perakkur A 2 23 3 132 109

E1316 Pulampatti A 1 14 38 57 216

E1317 Vellaralpatti A 2 32 13 65 138

E1401 Unkalpullyangulam H 1 12 39 6 64

E1402 Vellakkuppam H 2 17 19 12 61

E1403 Karuppukkal A 2 18 14 28 91

E1404 Perungalakkudl A 2 26 9 170 178

E1405 Kllavlkkulam A 3 9 7 16 70

E1406 Marudur A 2 6 2 36 75

E1407 Sorukilipatti H 2 17 85 26 135

E1408 Idaiyapattl H 2 2 95 5 144

E1409 Mukkampattl H 2 27 580 41 148

E1410 Vellalappatti A 2 26 7 102 132

E1411 Manikkampattl A 2 15 40 80 214

E1412 Tiruvadur A 1 13 21 26 138

E1413 Kovilpatti A 1 18 7 65 155 -

CURVE THICKNESS(M) RESISTIVITY(Ohnl-m)

TYPE (LAYER - WISE)

157

238

14

806512332068381738237

26

717

5

24

3050135535162053181649

151120162350195

54

27132315122

154 105

238354

2013

38

95110162775

150200383007074

340

24107

756530195

1209

34102184

173

14

27501885

12124

52137

15542040376

12

950178018482310302111

1408034

4813

13015

32513876010012go

136024

1328

1178243422841202375806

266334261019

2643251639

76170

3481537413613

2354

6641

1632415211345

2281121461187026

9

82100771025362512613975596910749

1261011725155200 2761331775813

11845 180

50

62584725

184

81

5

60

AHAHHHHHHHAAHAAAHAKAAHAAAAAAAAAAAHAAAHAAHAAAHHHAAAK

215223112322221212222321212231222222221212212222121

TABLE 6..3COfltd.

EOELECTRIC PARAMETERS OF SUBSURFACE ZONES IN VAIGAI RIVER BASIN142

;ITE LOCATIONODE NAME

':1 501 PadinettamkudlE1502 NallukulamE1503 AmbalakkaraflpattlE1504 Vellalur:0201 Tevaram:0202 RenganathaPUram:0203 Kombal

70401 SipalakottalF0501 GovincianagarmF0601 Palakkombal1301 KaruthapUllYefldal71302 SeegankulamF1303 SakkimangalamF1304 KannikulamF1305 KondpethaflF1306 PapakudiF1307 IlamanurF1308 EdangunduF1309 VanalurF1310 PottappanaiYUrF1311 KolkkudlF1312 KarserlF1313 SakkudlF1314 AthikulamF1315 AnanjiyurF1316 OvalurF1317 KalimangalamF1401 KunnaturF1402 VarlchchlyUrF1403 ParayankulamF1404 AlavandarF1405 IsalaniF1406 PuvandiF1407 VeepadappuF1408 PunjuttiF1409 KiranurF1410 EnadiF1501 ArasanurF1502 MudikandamF1601 ponnakulamF1602 Kottakudi00301 Muthu KrishnapUramG1501 Malavarayaflefldal

01601 KavanurHO101 Mel GudalurH0201 KambamH0202 UttamapuramH1401 AlavadalYanH1501 Killukudi

H1502 VakudiU1c(V Muttnendal

TABLE 6.3 contd.

GEOELECTRIC PARAMETERS OF SUBSURFACE ZONES IN VAIGAI RIVER BASIN 143

SITE LOCATION CURVE THICKNESS(M) RESISTIVITY(ohm-m)

CODE NAME TYPE (LAYER - WISE)

H1504 Mel P4elkudi H 1 21 80 8 101

H1505 Kirungakottai K 1 5 24 28 31 135 102

H1506 Pudur A 3 15 26 260 114

H1601 Manambakki H 2 24 67 20 172

H1602 Kurundangulam A 2 21 42 1680 195

H1603 Manamadurai H 1 4 10 5 76

H1604 Navattavu H 1 4 80 4 89

H1605 Pillaruttan H 1 35 80 16 44

H1606 Manakkulam H 3 9 44 7 66

H1607 Kombukkaranendal H 1 18 38 11 95

H1701 Seyyalur K 3 10 1 8 6

10101 Lower Camp (Uttama) K 1 14 8 16 78

11601 Melpasall A 2 45 75 750 110

11602 Valllkkudl A 3 13 3 11 51

11603 Arasanandaflur H 2 7 8 2 264

11604 AlagapachCheri A 2 11 45 3 49 22 18

11605 Nedungulam H 2 9 130 26 285

11606 Sudlyur A 4 90 4 160 92

11701 K11 Nettur A 1 7 3 4 38

J1601 Vaduganathapuram A 2 40 3 27 68

J1602 Mel perungaral H 1 4 6 4 120

J1603 Urakkudi H 1 33 2 5 20

J1701 Vilattur A 5 113 1 4 4

J1702 Kutchatanallur A 2 43 3 31 51

J1801 Paramagudi H 2 26 130 7 23

J1802 Emaneswaram A 4 63 4 40 48

J1803 KomarakurlChChl A 2 58 3 50 43

J1804 Nagarkudi K 2 50 4 144 45

J1805 Yellamanur A 3 63 5 46 58

J1901 Vallamkudl K 3 75 1 6 3

J1902 TalaiyadlkOttal K 4 8 4 76 6

J1903 Akkiramesl A 3 44 1 6 15

J1904 Anjamadal K 3 38 2 7 5

J1905 Chittanendal H 2 27 2 4 6

J1906 Tavalalkulam Q 2 15 22 14 6

J1907 perlyanendal H 2 20 23 2 5 4 5

J2001 Pandappanendal H 3 28 2 36 61

J2002 Koluvur A 2 50 2 3 5

J2003 Tanlyappuli H 1 13 4 2 27

1(1801 t4anjur K 2 27 6 9 7

K1901 Manjarkollal A 2 43 10 13 15

K1902 Kil Kottal H 1 5 15 9 18 4 26

K1903 Pulattur K 2 50 2 15 19

1(1904 Sirakikottal A 4 95 1 12 14

K1905 Kakkandal H 2 40 7 4 6

1(1906 Kamankottal H 1 33 9 5 20

1(1907 Mennandi A 4 54 1 4 5

1(1908 Kenkondafl K 3 75 2 9 6

1(1909 Sevvar A 4 54 1 3 6

1(1910 NagachChl H 2 50 18 7 8

K2001 Chaturvedamangalam A 2 60 1 8 16

TABLE 6.3

EOELECTRIC PARAMETERS OF SUBSURFACE ZONES IN VAIGAI RIVER BASIN 144

ITE LOCATION CURVE THICKNESS(M) RESISTIVITY(ohm-m)

ODE NAME TYPE ( L A V E R - W I S E )

:2002 Tlyagavanseri A 1 13 3 8 20

:2003 Mudalur Q 4 100 200 5 4

2004 Kiliyur A 2 38 2 2 5

:2005 Tetangal H 2 60 4 3 6

:2006 Pondiyur H 1 10 158 10 2 10 11

:2007 Perungalur A 1 33 3 16 6

:2008 Kavanur H 3 26 13 5 30

:2009 Toruvalur A 2 10 4 7 6

:2010 Karendal A 3 50 2 16 21

:2101 Pullangudl A 3 65 2 80 50

2102 Peruvayal A 2 1 2 19 76

:2103 Chlttarkottal H 1 35 24 15 35

.1901 Kodlkulam A 2 55 1 2 3

.1902 Bogalur H 2 40 32 5 7

..1903 Seyyalur K 2 15 3 8 5

.2001 Vannlvayal A 3 47 5 108 97

.2002 Uchandanavayal A 2 30 35 44 23

.2003 Kurlyur A 3 44 1 18 19

.2004 Surankottal K 2 38 6 9 7

.2101 Remnad A 1 33 7 280 330

.2102 Palangulam A 2 40 3 16 33

.2103 Katturadl 0 3 10 625 16 4

.2104 Kusavankudi A 3 68 4 76 70

.2105 Attiyuttu A 2 60 2 84 64

.2106 Valantaraval H 1 4 370 9 6

.2201 Terbogl H 1 18 600 15 53

.2202 Puttakulam Q 2 35 3400 85 83

L2203 Perunkulam A 2 48 2 42 271

L2204 Alagankulam A 2 5 68 25 37 420 38

145

146

be due to the presence of some good structures below the

rocks.

4.The "Q" type curve, which comes due to a continuouslydecreasing resistivity (p 1 > p2 > p3) is seen along the coast

line. This is indicative of the presence of saline water and clay

horizons.

6.6 GEO ELECTRIC LAYERSThe VIES data of the basin have been interpreted through curve matching

techniques. The layer-wise aquifer thickness and resistivites obtained are listed in Table6.3. lnVaigai River Basin, a three-layered aquifer structure is noticed from the soundingdata. Contour maps are prepared to denote the low or high resistivity horizons. Figure6.6 shows the isoresistivity contours of second layer. The area has been conveniently

divided into four horizons;

(i) < 40 ohm-rn

(ii) 40 - 80 ohm-rn

80 - 100 ohm-rn &

(iv) > 100 ohm-rn.

Low resistivity horizons exist only along the upstream catchment and along thedownstream end, almost in the entire discharge zone. The central portion of the basin is

poor in aquifer resistivitieS.

6.7 DEPTHWISEISO-APPARENT RESISTIVITIESQualitative methods help in learning the general information about the geological

structure and vertical changes in the subsurface environments. Interpretations are alsodone by preparing thematic maps using the spatial variation of Isoappareflt resistivity.

In the earlier investigations made in different parts of the globe, it has been specifiedthat the horizons saturated with saltwater normally show a very low value of resistivity.

Iso-apparent resistivity maps have been prepared ? with reference to 20 rn and 40 m

147

148

149

depth, despite the limitations involved in the concept of depth of penetration. TheseFigures,6.7 and 6.8,are much useful,

I. for a better understanding, planning and management ofthe wastelands having horizons with low resistivities and

2. to locate the zones of potable water.

Promising potential zones ( < 40 ohm-rn ) are restricted to a few patches only.Depending upon these, the sub basins concerned could be taken into consideration forartificial recharge and for establishing the other water harvesting structures.

6.8 GEOELECTRIC PARAMETERS

A geologic section differs from a geoelectric section when the boundaries betweengeologic layers do not coincide with the boundaries between layers characterised bydifferent resistivities. Thus, the electric boundaries separating layers of different resistivitiesmay or may not coincide with boundaries separating layers of different geologic age ordifferent lithologic composition. For example, when the salinity of groundwater in agiven type of rock vanes with depth, several geoelectric layers may be distinguishedwithin a lithologically homogeneous rock. In the opposite situation,layers of differentlithologies or ages or both may have the same resistivity and thus form a single geoelectriclayer.

A geoetectric layer is described by two fundamental parameters, its resistivity 'P'and its thickness 'h'. The other geoelectric parameters which can be derived from thesetwo are

(i) total longitudinal unit conductance (S)

(ii) total transverse unit resistance (T) and

(iii) aquifer anisotropy (X ).

(i) The total longitudinal unit conductance (S) of a place canbe determined by using the equation

n hihi h

I 2 ns= = + +

i=IP• P P P

I I 2 n

—4.2

150

where h and P are the thickness (m) and resistivities (ohm-m) of the 1th layer upto nthlayer.

Variations in a s, from one YES to the other have been used in a qualitative sense toindicate changes in the total thickness of low resistivity materials (Zohdy, 1969; Henriet,I 975.;Worthington, 1977; Galin, 1979). Large 'S' values are indicative of deeper basementand small 's' values are indicative of shallow basement. It has also been reported (HenrietOp. Cit Galin Op. Cit) that high 'S' values are characteristic of low aquifer transmissivities.Empirical relationship between longitudinal conductance of weathered layer andgroundwater yields has been observed particularly for winter months during resistivityinvestigations for groundwater in metamorphic areas near Dhanbad , in India, byVerma etal. (1980).

(ii) The total transverse unit resistance (T) of a location canbe obtained by using the formula

nT = I hP1 =h 1 *P 1 + h 2

* P 2 ++ h*P -4.3i=l

where h 1 and P 1 are the thickness (m) and resistivities (ohm-rn) of the ith layer, upto th

layer.

The total transverse resistance has generally been interpreted in both quantitativeor qualitative manner. The quantitative interpretation attempts to develop a correlationbetween T and average borehole test yield (Worthington Op. Cit) or between T andaquifer transmissivity values (Scarascia, 1976).

This property has been used to indicate the varying thickness of high resistivitymaterials and/or variations in their transverse resistance (Zohdy et al. 1974). IncreasingT values are accompanied by an increase in the thickness of the high resistivity materials.It has been noticed (Matzner, 1983) that increasing 'T' have coincided with high

transmissivities of aquifers.

(iii) The coefficients of anisotropy ()) of a formation can beobtained using the equation

ITS

H

Bodi kkamanvadiPalai yankottaiPachcha i mal al yankotta IKend i chhampatt iSwami yarpattiArapadi thevanpattiKamakkapatt IGanguvarpattiKanavaypattiVadipattiPangal appattiChi nnamanayakkankottajKodangi nayakkanpattiKotturNi lakkotta-iKatti nayakkanpattiManjoothuOrutattuKai lasapattiPen akul amVal dyanathapuramTamara I kulamVadugappattiAlagi rinayakkanpattiKi imangalamSi ivarpattiErumalal nayakkanpattjBommi nayakkampattjDevadanappatt IRanganathapuramEluvarpattiKil VadippattiKottarpattiVeri yappanayakkanpattiPuvampattiViral ipattiSandai yurPannaipattiSi vaghanapuramKul 1 ichettipattiMuthal apuramVi ri nayakkanpattiMusuvanuthuP11 lai yarnattamKoovanuttuNakkal utteVi lampattiEtti loduMeenaksh I puramRamanathapu ramMalal yakkavundanpatti

21762.003157.005480.004440.00790.00

7922.00350.0072.00

300.0060.00

4423.005074.751216.00159.50

18180.005341 .005014.00576.00

10122.00648.00

3780.00442.00

6390.001699.00

67650.0021042.00

266.001820.001 144.001410.002760.009616.00

36072.00720.00

4340.0036080.001722.005716.003348.006025.00

130130.007396.008710.00392.00518.00

8432.002400.00319.00

3172.0011 7 1 .00

16236.00

0.260.430.240.130.400.200.500.530.381 .330.770.150.340.190.111 .050.450.360.321.250.090.470.070.780.060.480.260.260.210.210.220.340.280.110.170.150.250.390.310.310.050.090.070.320.350.270.100.240.120.310.24

1.031.191.001 .831 .051.131 .021 .231.071.121 .241.101.021 .381.071 .031 .041 .031.151 .021 .041 .031 .041.011 .321.291.051 .041.101.011 .301.801 .291 .291 .031.191.151.051 .011.181 .551 .331.131.011.121.291 .021 .081.411 .001 .32

TABLE 6.4151

AQUIFER GEOELECTRIC PROPERTIES FROM VAIGAI RIVER BASIN

SITE LOCATION AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERCODE NAME RESISTANCE CONDUCTANCE ANISOTROPY

ohm-msq. mhos

A0801AO9O1A0902A0903A1001B0501B0601B0701B0702B0801B0802B0803B0901B0902B0903B0904B0905B0906CO501CO502CO503CO504CO505C0601C0602C0603C0604CO605CO606C0701C0702C0703CO704C0705C0706CO707C0708C0709CO8O1C08O2C08O3CO8O4CO9O100902CO9O3CO9O4CO9OSCO9O6C0907CO9O8C09O9

TABLE 6.4 Contd. 152


SITE LOCATION

AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFER

CODE NAME

RESISTANCE CONDUCTANCE ANISOTROPY

ohm-msq. mhos

C0910C0911CloolC1002C1003C 101C 102Cl 103Cl 201C1202C1203C1204Cl 205C1206Cl 207C1208C1209C12 10C1211Cl 212C1213D0201D0301D0302D0303D0304D040100402D04O3D040400501D0502D0503D0504DO5O5D0506D0507DO6O1DO6O2D060300604DO605DO6O6D060700608D0609D061 0D0901D09020100101002

Kuttel kunduPal lapattiAl uguvarpattiKal lad 1 pattiKachchai kattiTetturRamakkavundanpattiVai yasi ppattiKonappattiSembatt ISukkampattiKri shnapuramPal ameduChattravel lalapattiValal yapattiMettuppattiMani kkampattiVel laiyampattiParai ppattiKodangi pattiSarantang IMundal (Ikkaraikalam)Karattupatt IKul asekharapattanamBodi nayakkanurAnnai kkarai ppattiBodi puramVazhai yattupattiTeniSukkuvadanpattiUnjampattiMadurapuri VadapuduppattiKunnurKamakshi puramSail ipattiMeiakannakapattiKadi rayakkavundanpattiKu rumbappatt IJambul aputturJakkampattiSankaramurti pattiAyyannattevaflPattlkovi ipattiGui apu ramRajagopalanpattiSubbulapuramAmbattanpattSitharkalaflattamAxyamkenvi thuMannad I mangai amKaruonatt 1

3696.00818.00240.00

3168.00420.001600.004280.002200.001232.00532.00

3408.003520.002560.001664.008606.00

19448 .0016236.00

96.009044.00640.00210.0048.00

1957.00382.00456.00135.00

12476.00800.00361 .00

3690.008275.00208.00

14300.0024240.0051490.002160-001365.00

202960.0017051 .00480.00

30360.001092.009840.001173.005025.005350.00

25296.0034080-0016016.0029953.00

89.00

0.390.400.110.080.240.160.060.250.460.320.460.480.231 .400.170.210.24

60.000.220.230.630.190.600.931 .520.500.480.310.190.210.170.550.180.080.050.210.310.090.210.480.080.140.150.160.120.120.170.080.410.430.75

1.531.011 .041.311 .001.051 .811 .021.191.011 .191 .021.211.101.112.441.321 .051 .281.011 .051.511.111 .351.311 .031 .411 .051 .051.011.111 .071 .271 .072.391 .021 .081 .442.151 .021.161 .231 .071.161.171.12• 08

1.191.551 .591.02



SITE LOCATION

AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERCODE NAME

RESISTANCE CONDUCTANCE ANISOTROPYohm-msq. mhos

D1003D10040100501006D100701008D1009DiOl 0DiOl 1Dl 101Dl 102Dl 103Dl 10401105Dl 10601107011080110901110Dlii 10111201113D120101202D1203Dl 20401205D1206012070120801209D12 10D1211D1212D1213D13010130201303013040140101402D140301404D1501D1502015030150401505D1506D150701508

I rumbad iNachch I kul amMull ipallamShol avandanTenkaraiPettalSolai kkurichiKottakulam (VadugapattiNedungu lamPuchampatt IThiruvalavayanallurTan i chch I yamNagarlChittalangudiKondal yampattiMelachi nnampatttSambakku lamPeriya IlandaikulamAmaraddak IAlagapuriKovi ipattiPandiKal lanaiEr rampatt 1Alanganal lurKi 1 ChinnanampattiKumaramMan i yanj ITandalaiI 1 avankul amAdanurMuduvarpatt IVavi damarudurMand I kul amAndamanParai kulamMatturKallandi riValal yapattiKidi ripattiTerkutteruVal lapattiPudusukkampattiKarathapul lyampattiMelurAttukku lamNaY I ni pattiVannamparal pattiSattamangal amTan i yamangal amVadakku Valaiyappatti

130.0021 .00

5842.00392.001139.00176.0071 .00

5967.00462.00

2340.001938.00393.00

2490.004356.002360.003550.003876.006129.00176.00

4896.0023-3166.003048.004760.002009.00118.00

6984.006916.001238.0093.00

4420.003648.00918.001185.003258.003982.004752.001728.008613.008606.009912.001512.001106.001072.00

57304.002688.00423.00312.00

2738.00336.00108.00

2716.00

0.542.081.130.320.590.970.940.520.610.332.410.510.100.240.190.190.240.410.510.400.110.630.650.470.680.650.330.550.270.910.360.370.240.400.330.570.430.450.170.300.100.260.500.370.600.510.350.250.696.000.21

1 .051.32.33

1 .011.181.011 .021 .541.401.111 .521.013.18.26

1.111.191.681 .063.151.481 .391.991 .921 .461 .281.12• 90

1.311.012.441.211 .021 .291 .391 .391.161 .301 .481.111.231 .231 .291.011.271.121 .051 .042.591.021 .021.13



SITE LOCATIONAQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERCODE NAME RESISTANCE CONDUCTANCE ANISOTROPYohm-msq. mhos

E0201 E.Pudukkottai 4042.00 0.18 1.03E0301 Silamalai 646.00 1.95 1.04E0401 Virapandi 13797.00 0.09 1.29E0501 Sangukonampaj 900.00 1.12 1.03E0502 Ammateljpuram 201.00 0.28 1.07E0503 Ramalingapuram 445.00 0.97 1.15E0504 Okkaraipatti 319.00 0.84 1.48E0505 Chittarpatti 182.00 0.96 1.10E0601 Karisalpatti 3874.00 0.51 1.94E0602 Kad-ir Narasinghapuram 1450.00 0.73 1.05E0603 Bodidasampatti 12742.00 0.28 1.05E0604 Mekkalarpatti 3542.00 0.20 2.66E0701 Timmarasanayakkanur 4305.00 0.15 1.00ElOOl kachchirayiruppu 3712.00 0.28 1.14E1002 Melakkal 562.00 0.40 1.00E1003 Tirumalnattam 3381.00 0.73 1.42El101 Paraval 152.00 1.23 1.05E1201 Kochchadj 180.00 0.84 1.23E1202 Vilangudi 241.00 1.42 1.09E1203 Maduraj 273.00 1.11 1.16E1204 Chikkandrachavadi 1056.00 2.10 1.68E1301 Udaikulam 196.00 0.52 1.01E1302 Mangalakkudj 2497.00 0.27 1.54E1303 Ulaganeri 3078.00 0.32 1.64E1304 Tatankulam 686.00 0.47 1.00E1305 Sengulam 2352.00 0.37 1.02E1306 Sirupuliyendal 5644.00 0.31 1.20E1307 Pudupatt-j 2280.00 0.43 1.01E1308 Tadankulam 8211.00 0.46 1.20E1309 Parayankulam 507.00 0.30 1.13E1310 Podsepatti 15558.00 0.50 1.47E1311 Tirumugur 154.00 0.57 1.04E1312 Kodikulam 420.00 0.90 1.02E1313 Mundanayagam 32030.00 0.50 1.52E1314 Sivalingam 870.00 0.27 1.02E1315 Perakkur 3042.00 0.84 2.02E1316 Pulampattj 836.00 0.27 1.01E1317 Vellaraipatti 2106.00 0.65 1.08E1401 Unkalpullyangulam 111.00 2.03 1.15E1402 Vellakkuppam 242.00 1.52 1.01E1403 Karuppukkal 532.00 0.79 1.02E1404 Perungalakkudj 4438.00 0.38 1.46E1405 Kilavikkulam 165.00 0.99 1.07E1406 Marudur 220.00 1.17 2.00E1407 Sorukiuipatti 612.00 0.68 1.07E1408 Idaiyapat,tj 200.00 0.42 2.29E1409 Mukkampatti 2267.00 0.66 1.34EldlO Vellalappatt-i 2666.00 0.54 1.36E1411 Manikkarnpattj 1280.00 0.24 1.03E1412 Tiruvadur 359.00 0.55 1.00E1413 Kovilpatti 1177.00 0.42 1.17



SITE LOCATION

AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERCODE NAME

RESISTANCE CONDUCTANCE ANISOTROPYohm-msq. mhos

Pad I nettamkudiNal lukulamAmbal akkaranpattiVel lalurTevaramRenganathapuramKombalSipalakottaiGov I ndanagarmPalakkombaiKaruthapul iyendalSeegankul amSakk I manga lamKann I ku lamKondpethanPapakud IIi amanurEdangunduVanalurPottappanal yurKol kkudiKarserSakkudiAth I kul amAnanj yurOval urKal imangalamK u n n at u rVarichchl yurPar ay an ku lamAl avandarIsalaniPuvand IVeepadappuPunjuttiK I ranurEnadiA rasanurMud I kandamPonnakul amKottakudiMuthu KrishnapuramMal avarayanendalKavanurMel GudalurKambamUttamapu ramAl avada I yanKi 1 lukudiVakud IMuttanendal

14440 .00229.001920.00198.00

1862.001945.00320.001028.001020.00958.00

5334.001368.001972.001152.00101 .00

3394.00180.00

5655.001374.00

22838.005010.00516.00

4968.0047634.00

404.00262.001486.002122.001324.00187.00384.00448.00505.00500.00404.001741 .004010.00138.00

10942.001709.00494.00624.00164.00243.001258.206590.00448.0030.00

322.003996.002412.00

0.040.420.600.526.472.851.211.130.966.220.560.711.120.560.640.490.480.081 .030.140.901.110.830.060.872.043.890.400.950.150.880.680.341 .040.810.561 .033.330.550.930.401 .041 .790.700.382.211 .493.334.030.497.76

1 .361.231.211.011.141 .091.511 .001 .421.091 .361 .641.181 .021 .001 .451 .161.141.211 .801 .291 .491.131.421 .041.101 .381 .461 .861.071 .671.031.011 .041 .001 .251.231.021 .291 .371.011.021.011 .001 .161 .091 .031 .001 .001.712.63



SITE LOCATION AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERCODE NAME RESISTANCE CONDUCTANCE ANISOTROPY

ohm-msg. mhos

H1504H1505H1506H1601H1602H1603H1604H1605H1606H1607H 170110101116011160211603116041160511606Ii 701J1601J1602J1603J 701J 1702J1801J1802J1803J1804J1805J1901J1902J1903J1904J1905J1906J1907J2001J2002J2003K1801K1901K1902K1903K1904K1905K1906K1907K1908K1909K1910K2001

Mel MelkudjKi rungakottaiPudurManambakkjKurundangul amManamadu ra INavattavuPi 1 laruttanManakku lamKombuk ka ranenda 1SeyyalurLower Camp (Uttama)MelpasalVal li kkudiArasanandanurAlagapachcherjNedungul amSudiyurKil NetturVaduganathapuramMel PerungaraiUrakkudiVi latturKutchatanal lurParamagud iEmaneswaramKomarakur I chch INagarkud IYel lamanurVal lamkudiTalajyadikottalAkki ramesiAnj amada iCh i ttanendalTavalaj kul amPen yanendalPandappanendalKol uvurTan i yappu 1 iManj urManjarkollajKil KottalPulatturSi rak I kotta 1KakkandalKamankottaiMennand iKen kondanSevvarNag a c h c hiChatu rvedamanga lam

248.003423.003978.00614.00

35364.0030.0096.00

640.00195.00236.0083.00

232.0033900.00

152.00")0.00

1535.00494.00

14416.0031.00

1086.0022.00167.00457.001339.00442.00

2536.002906.007208.002913.00453.00624.00267.00272.00112.00254.00196.00

1014.00154.0030.00

255.00579.00159.00754.00

1144.00174.00174.00220.00681 .00166.00386.00482.00

2.640.370.17.23

0.060.901.012.201 .35.66

4.251 .000.092.183.752.940.361.562.082.151.177.10

33.252.053.732.581 .830.851.97

15.501.11

10.336.937.751.16

10.752.28

17.676.753. 333.514.144.33

ii .9210.296.71

1 7 . 509.8322.007.259.50

1.161.191 .46• 06

2.001 .041.971 .041 .351 .04• 44

1 .021.151.141.181.161.211 .601 .001.151.011.011 .041.171.451.211.211 .501.151 .072.191. 121 .061 .021.011.021 .55• 00

1.021.01• 00

1 .221.10.18

1.011.011 .071 .051 .041 .021.09



SITE LOCATIONCODE NAME

AQUIFER TRANSVERSE UNIT SPECIFIC AQUIFERRESISTANCE CONDUCTANCE ANISOTROPYohm-msq. mhos

K2002K2003K2004K2005K2006K2007K2008K2009K2010K21 01K2102K2103L1901L1902L1903L2001L2002L2003L2004L2101L2102L21 03L21 04L2105L2106L2201L2202L2203L2204

Ti yagavanseriMudal urKi 1 iyurTetangalPond I yu rPerungalurKavanurToruval urKarencla 1Pul langudiPeruvayalCh I ttarkottaiKodiku lamBogalurSeyyalurVann I vayalUchandanavayalKuri yurSurankottalRemnadPal angu lamKatturad IKusavankud IAtti yfJttUVa 1 antaravaTerbogiPuttaku lamPerunkul amAlaganku lam

107.001300.0080.00188.00

1610.00531.00169.0078.00

806.005206.00

23.00549.00112.00264.00126.00

5091 .001390.00795.00354.00

9247.00646.00

2035.005180.005044.00406.00870.00

9775.002020.00

28795.00

1 .9620.0220.0020.5020.902.405.431 .934.632.311 .052.38

29.508.062.541 .040.745.444.560.263.170.631.641.710.45

• 200.412.140.38

1 .03.55• 00

1 .001 .091 .051 .041 .021.151.611 .641 .001.011.101 .051 .451 .001.401 .001.441 .082.751 .301 .502.69

70• 72

1 .321 .39

158

-oJ-oC)

.a. ZN -

U) .(f)<LiicDcrzc 110

toW F-< zE?J).- 1±::

— ZZ

LO o I/- > 0 CL ..

tn

tn

N •

•/•=7:(

I •. • ••1 • ••••V/• •..• ; :j.i•Il

N>• eI •I ••. ..•_&/

_ U)u,) •

// • •:.O (

—

0II0.

N

11 cr•u_•

XU)-x ••1..2 .E(f)w o

clC

cN

E

\

•'4•N

•/

159C.'

Ln

w—j

C-)U,

0

160

whereT is the total transverse resistance (ohm -mts 2), S is the total longitudinal conductance(mhos) and H is the total thickness of the formation (Mts).

This coefficient is usually greater than 1.00 but does not often exceed 2.00 (Zohdyet. al., 1974). It can be used as a measure of finding out the extent of anisotropismprevailing in an area of interest. It accounts 1.02 - 1.10 for alluvium, 1.05 - 1.15 forsandstones and shales, 1.40 - 2.25 for slates and 2.00 - 2.8 for graphite slates. As thehardness and compaction of rocks increase the coefficients of anisotropy also increases(Keller et. al., Op. Cit). These parameters are listed in Table 6.4

6.9 GROUNDWATER POTENTIAL ZONES

Numerous investigations have been done in various locations over the globe todemarcate the potential zones of groundwater. However, studies on hard rock terrainare also many and varied. In the analysis ofVES curves of hardrock areas, the resistivity of

the second layer is considered7 on the basis that the well sites are selected mostly forsinking borewells and they receive water from the weathered or fractured zones. Since

' P i corresponds to the top soil cover, it has not been taken into consideration. Fordetermining the depth to the basement topography, the thickness of the first and second

layers (h 1 + h2) have been considered depending upon their resistivities Thick and lowresistivity horizons are taken for demarcating the groundwater potential zones over thishard rock terrain. Balakrishna et. al (1979,J9.3);Verma et. al, (1980), Sharma (1982),

Patangay et. al (Op. Cit) 1 Krishnaraju (1983), Prasad (1984), Balasubramanian et. al, (1985)are a few notable works published on this line, in India.

The depth to the basement topography of the basin has been shown in Fig. 6.9.This can help the hydrogeologists to have an idea of the total depth to be drilled, thelength of casing pipes to be installed,while drilling and the direction of groundwater flowabove the basement topography. The basin has been divided into 4 zones as (i) <20 m,(ii) 20 - 40 m (iii) 40 - 60 m (iv)> 60 m thickness of the aquifers. It is very clear that thedepth to the basement is maximum along the coast line.

The groundwater potential zones are shown in the Fig.6. 10.

It could be seen from this Figure that there are only a few promising groundwaterpotential zones inVaigai Basin.This indicates the poor state of the aquifer for groundwater

Ib—

-Q

; z— 0(I)

U w/ c a0.

00.

ucrd z)o.00000/O.00.

? LU j ..-6? 0•O 0

0 0 ,, . • .0

I0 0 b 0• 0 0

Z 0 0 0 0 0 0 0 /0.

LU 0(10 0 0 0 0 0

0 0 0 0•o 0 o)

OIL /000-- •_/000 C.,

• 0 0 0 0 0 0 —c'J-.a,.00 > C •

0 0 0 0 0 0 0o n ., -. 0. ( 0

0 00''o:'o - 0 cVuj

00 0 0 0 cfOIooQ 000

0 0 o-

(I)0 • 0 0 0. • 00. E0 o/ a,0 • U

0 0 0. C0 / ci00 0 -.

0•

0 0000 o.. O C

00j od 0 a

0000>'a

D c t-.0 CO .4

000

0I2

•

CI"(•J C'l .46.

c

— U) a) 0 0a w .cT V A

0—

NONm 10

0.QO 0 0 00 00 o 0 o N cn0

>. od. '• NI.- a) 0 N0 0 0 . 0

0 0000

0 N0 0 0 ci

0 0 0000-'fr 0

.0 00

0 o0 0'/i3O Eo

oci 0

IL. 0

o: 0 0 0 0 0

• 0jo•, 0

•°-I•

161

•c1C-

0C.,

NC--.

162

163

164

development calling for an increased use of available surface water and go for much water

harvesting methods.

Figures 6.11 through 6.13 show the Specific conductance, Aquifer transverse

resistance and aquifer anisotropy maps of the basin, respectively. Conductance is more

along the upstream and downstream ends, and along the river course. The other two

figures suggest the heterogenous nature of the aquifer media.

This geophysical study has given the probable potential zones for groundwater

development, which is very limited in areal extent.

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