Hydrogeological and Geophysical Studies ; Exploratory Well Drilling & Aquifer

Parameter Characterization ; Aquifer Maps Studies

byK.MANIKANDABHARATH

ANNA UNIVERSITY,CHENNAI

INTRODUCTION:

•Groundwater is water that exists in the pore spaces and fractures in rocks and sediments beneath the Earth’s surface.

•It originates as rainfall or snow, and then moves through the soil and rock into the groundwater system, where it eventually makes its way back to the surface streams, lakes, or oceans.

Double ring Infiltrometer

Field Infiltration test :

• Hammered and poured water.

• Infiltration Rate depends on:

• 1. Soil texture ( size of the solid particles) .

• 2. Soil Structure ( arrangement of the solid particle) .

• • 3. Infiltration rate of

soil groups with respect to soils from an irrigation point of view.

Name of the site: CLRI campus, opp to IIT, Guindy.District: ChennaiWell no:1802PZ Gunidy (CLRI)Lithology: Silty clay, Charnockite Weathered, Quartzite Weathered

Well Lithology:(No:1802PZ)Top SoilCharnockite WeatheredQuartzite WeartheredCharnockite WeatheredCharnockiteCharnockite FracturedCharnockite

• To identify the rate of infiltration in that place. And we dig a 5 inch from the top soil, and we placed a “Double Ring Infiltrometer” and hammered it, and pour water in to it and started taking reading, and we took the reading in the following manner:

• 1 min interval - 10 reading (10 mins)• 2 min intervals - 10 reading (20 mins) • 10 min intervals - 10 reading (1 hour )• Soil type Basic infiltration rate (mm/hour) :• sand less than 30 • sandy loam 20 – 30 • loam 10 – 20 • clay loam 5 – 10 • clay 1 - 5

Time in Minute Head Before Filling in CM

Fall in head in CM Cum.Fall in head in CM Infiltration rate cm/hr Infiltration Rate cm/hr Indiviciate

0 25 0 0 0 301 24.5 0.5 0.5 30 302 24 0.5 1 30 303 23.7 0.3 1.3 26 184 23.5 0.2 1.5 22.5 125 23.3 0.2 1.7 20.4 126 23.1 0.2 1.9 19 127 23 0.1 2 17.142 68 22.8 0.2 2.2 16.5 129 22.6 0.2 2.4 16 1210 22.5 0.1 2.5 15 612 22.3 0.2 2.7 13.5 614 22.1 0.2 2.9 12.42 616 21.9 0.2 3.1 11.62 618 21.7 0.2 3.3 11 620 21.6 0.1 3.4 10.2 325 21.2 0.4 3.8 9.1 4.830 20.9 0.3 4.1 8.2 3.635 20.6 0.3 4.4 7.5 3.640 20.3 0.3 4.7 7.1 3.645 20 0.3 5 6.6 3.650 19.7 0.3 5.3 6.4 3.660 19.3 0.4 5.7 5.7 2.470 18.8 0.5 6.2 5.3 380 18.4 0.4 6.6 4.95 2.490 18 0.4 7 4.6 2.4100 17.6 0.4 7.4 4.4 2.4120 16.8 0.8 8.2 4.1 2.4140 16 0.8 9 3.85 2.4160 15.4 0.8 9.6 3.6 1.8180 14.7 0.6 10.3 3.4 1.8200 14 0.6 11 3.3 2.1220 13.3 0.7 11.7 3.2 2.1240 12.6 0.7 12.4 3.1 2.1260 11.6 0.7 13.4 3.1 2.1280 10.7 0.7 14.3 3.1 2.1300 20 1 15.4 3.1 3.3320 19 1.1 16.4 3.1 3340 18 1 17.4 3.0706 3360 17.1 0.9 18.3 3.052 2.7380 16.1 1 19.3 3.05 3400 15.1 1 20.3 3.04 3

• Geophysical Studies:

• The Role of geophysics in groundwater exploration is vital to understand subsurface conditions accurately and adequately.

• Geophysical investigations help assess the presence of aquifers in geologic formations, estimate weathered zone thickness or bed rock topography and fractures, and assess quality (in terms of salinity) of groundwater.

• Geophysical, it is possible to precise the three-dimensional geometry and disposition of aquifers.

Vertical electrical sounding (VES), also known as ‘electrical drilling’ or ‘expanding probe’, is used mainly in the study of horizontal or near-horizontal interfaces. The current and potential electrodes are maintained at the same relative spacing and the whole spread is progressively expanded about a fixed central point. Consequently, readings are taken as the current reaches progressively greater depths. The technique is extensively used in geotechnical surveys to determine overburden thickness and also in hydrogeology to define horizontal zones of porous strata.Methods used in Resistivity survey:Many configurations of electrodes have been designed. Although several methods are occasionally employed in specialized survey, the main methods used in resistivity are following.1. Wenner Configuration.2. Schlumberger Configuration.3. Dipole-Dipole Configuration. In this methods most common methods are Wenner and Schlumberger while in Hydrological survey commonly we will use Vertical electrical sounding with Schlumberger configuration of electrodes.

VES DATA: Village – Rajampalayam : Block – Anagram Block : Taluk – Panrutti District – Cuddalore Spread Direction - E-W Date – 14.06.14 Latitude- 11048’ 48” Longitude – 79039’50”

The Lower Vellar watershed in Cuddalore District, Tamil Nadu, is characterized by coastal Tertiary Sedimentary rocks overlain by Quaternary Alluvium. The freshwater occurs in the Quaternary Alluvium and underlying Cuddalore Sandstones of Tertiary Era, Mio-Pliocene Age, which are being tapped up to the depth of 250 to 300 m.

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Schlumber configuration

S.No. AB/2 in m MN/2 in m K (geometric factor) R(resistance)Ohm

Resistivity in Ohm m

1 1.5 0.5 6.28 13.3 83.5

2 2 0.5 11.78 8.28 97.5

3 3 0.5 27.5 4.25 116.87

4 4.5 0.5 62.8 2.57 161.39

5 6 0.5 112.36 1.73 194.38

6 8 0.5 200.3 1.091 218.52

7 0.5 313.4 0.696 218.12

8 10 2 75.4 2.89 217.9

9 15 2 173.59 1.28 222.19

10 15 0.5 706.16 - -

11 20 2 311.06 0.638 198.45

12 25 2 487.79 0.305 148.77

13 25 5 188.5 0.778 146.46

14 30 5 274.9 0.483 132.77

15 30 2 703.8 - -

16 40 5 494.86 0.199 98.47

17 50 5 777.64 0.08 62.21

18 50 10 377.04 0.192 72.39

19 60 10 549.85 0.07 38.48

20 60 5 1123.26 0.031 34.82

21 70 10 754.08 0.032 24..13

22 80 10 989.73 0.015 14.84

23 90 10 1256.8 - -

24 100 10 1559.29 0.006 9.35

25 100 20 754.08 0.013 9.80

26 120 20 1099.7 0.006 6.59

27 120 10 2246.53 - -

28 140 20 1508.16 - -

29 150 20 1735.95 0.002 3.47

ITERATIVE- COMPUTER TECHNIQUESITERIIJFGNJFNNVMS-DOS based, FRES soft ware & Window based IPI2WIN, where inputs of the layer parameters should be given and modified till the best match is obtained & layer parameters are obtained.

SUBSURFACE GEOPHYSICAL LOGGINGBOREHOLE LOGGING• Spontaneous Potential (SP) • Point Resistance (PR) • Short Normal (N16”) resistivity • Long Normal (N64”) resistivity • Lateral (6’) resistivity • Natural Gamma • Calliper logs Geophysical logging has been used to delineate:•Identification of aquifers / granular zones •Quality variation in granular zones •Delineation of potential aquifers for tapping •Deciphering saline and fresh water aquifers

•Zones to be sealed to prevent mixing of good potable water with poor quality water.

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DRILLING:•Drilling is the process where by rigs or hand operated tools are used to make holes to intercept an ore body. •Drilling is the ultimate stage in exploration.Purpose:The purpose of drilling is;•To define ore body at depth•To access ground stability (geotechnical)•To estimate the tonnage and grade of a discovered mineral deposit •To determine absence or presence of ore bodies, veins or other type of mineral deposit Types:Drilling is generally categorized into 2 types:•Percussion Drilling: This type of drilling is whereby a hammer beats the surface of the rock, breaks it into chips.

-Reverse Circulation Drilling (RC)

•Rotary Drilling:This is the type of drilling where samples are recovered by rotation of the drill rod without percussion of a hammer.

- Diamond Drilling - Rotary Air Blast (RAB)- Auger Drilling

REVERSE ROTARY RIG:

DRILL BIT USING

DTH drilling rig machines

SLOTTED PIPES:

“SLOTTED PIPES” using in the formation which contains gravels, in the gravel formation, after the drilling is over bore well started caving, and also in the gravel formation act as an aquifer, in this case the slotted pipes are used.

DRILL BIT:

Samples Plate :

STREAM ORDER DRAW

What is Aquifer Mapping?

Aquifer Mapping

Aquifer mapping is a multi-disciplinary holistic scientific approach for aquifer characterization. It leads to aquifer-based groundwater management.

Mapping of aquifers helps determine the quantity and the quality of groundwater in a particular area, including:

Vertical and lateral extent of aquifers

Depth to water level/ piezometric surface in the aquifers

Productivity of the aquifers

Concentration of various chemical constituents in groundwater in different aquifers

Current stage of groundwater development in various aquifers

Identification of recharge and discharge areas of the aquifer

Delineation of vulnerable areas with regard to exploitation and contamination

Aquifer Mapping Draw • We are used in the

different topposheet• 57 K/16• 57 L/9• 57 O/3• 57 L/13• 58 J/2• 57 K/11• 57K/12 and etc…

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