Micro-level Aquifer mapping & Aquifer management Plan for

Cuddalore Coastal Aquifer system, Tamilnadu

Central Ground Water BoardSouth Eastern Coastal Region, ChennaiMinistry of Water Resources, River Development and Ganga RejuvenationGovernment of India

Dr. D.Gnanasundar, Dr. M.Senthilkumar & Sh. N. Rameshkumar

Regional & Micro-level aquifer mapping

Aquifer Mapping

is a scientific process wherein a

combination of Geologic, Geophysical,

hydrogeological & Chemical studies

(Field & Laboratory studies) – applied to

characterize

• the quantity,• quality &

• sustainability of groundwater.

Objectives:

1. To decipher the vertical & lateral extent of the

Aquifer Disposition – (2D & 3D) along with their

characterization.

2. To formulate Aquifer Management Plans

3. To facilitate sustainable management of GW

resources at regional & local level through

Participatory Groundwater Management.

Tamilnadu & UT of Puducherry

Aquifer management Plan through Numerical Modelling

Regional Aquifer Mapping

Micro-level aquifer mapping

Decipher Aquifer Units within Principal Aquifers

Conceptualization of the aquifer system

Information on aquifers to farmers, State Govt. stakeholders for sustainable GW management

Approach

Regional Aquifer System, Tamilnadu

Regional &Micro-level aquifer mapping

Sandstone

Pondicherry coastal aquifer

Cuddalore coastal aquifer

Jayankondam aquifer

Micro-level aquifer mapping

Regional aquifer mapping

Specific Issues

1. Coastal aquifer – forms a part of Cauvery Basin.

2. Intensively irrigated area by Groundwater

3. Depressurization of the aquifer for mining activity.

4. Groundwater is pumped for drinking water supply to Chennai city

during lean periods.

5. Extension of the aquifers into the sea.

sandstone

Alluvium sand

Alluvium sand

Bay of

Bengalsandstone

Alluvium sand

Alluvium sand

Bay of Bengal

Cuddalore coastal Aquifer

Strike : North East – South westDip : South EastGW flow : South East (along the dip direction)

Aquifer Mapping Location : 200 km south of Chennai.(Cuddalore dt, TN)

Regional Aquifer Mapping & Aquifer management Plan : 1948 sq.km

Micro-level Aq.mapping : 428 sq. km

Sandstone

Alluvium

Sandstone

Vellar river

Recharge zone

Perumal Eri

Recent alluvium Sand/sandstones

Mio-pliocene sandstones

Eocene sandstones

Eocene sandstones

(Aquifer 4/Confined)

(Aquifer 3/Confined)

(Aquifer 2/Confined)

(Aquifer 1/unconfined)

clay

clay

clay

clay

lignite

lignite

ligniteclay

clay

claymsl

40 m

40 m

80 m

100 m

120 m

B

B’

A”A

? Inf. required

Inference : Multi-layered aquifer system

Outcome by data gap analysis 2 – D Aquifer Disposition

Pebble

Cuddalore Sandstone –potential aquifer

• Ferruginous,• Friable• Medium to coarse

grained with• continuous or

discontinuous clay intercalations.

Open cast mine – Neyveli

Lignite at 80 m bgl

north south

west

East

Kudikadu PZ

Period in months

Piezometric

head (m)

Long term Piezometirc head behaviour of aquifer – II

1. Exploratory Drilling were carried out at 18 locations &

2. Additional 22 Piezometers were constructed to micro-monitor the behavior of Groundwater Heads of Different Aquifer Units.

Zone wells (Pz) tapping aquifer unit –III & IV

Outcome by data Gap analysis

Exploration carried upto 400 bgl.

Hydrogeological studies

clay

Sst.

Sst.

Sst.

Sst.

clay

clay

Aquifer Disposition inferred from E-Log

Aquifer – I (Sand/Sandstone)

Aquifer – II(Sandstone)

Aquifer – III(Sandstone)

Aquifer – IV(Sandstone)

Sst.

clay Mio-pliocene

Eocene

Lignite (marker bed)

sangolikuppam

Principal Aquifer : Sandstone

Aquifer Units : 4 nos

Inference :

Multi-layered aquifer system (down to explored depth of 400 m)

Age:

Outcome from geophysical study

Aquifer Units

Formation

Aquifer I (unconfined)

Recent -Alluvium

Mio-pliocene - Cuddalore

sst.

Clay Clay

Aquifer -II (confined)

Mio-pliocene - Cuddalore

sst.

lignite/CLay

Eocene -Lignite/clay

Aquifer - I

Aquifer – II(107 – 122 m bgl)

Aquifer - III (Confined)

Eocene -Sandstone

s

Clay Clay

Aquifer -IV (Confined)

Eocene -Sandstones

Aquifer - III

Aquifer - IV

(122 – 126 mbgl)

(126 – 244 mbgl)

(Gl – 73m bgl)

(263 – 364 mbgl)

Aquifer disposition inferred from Litholog

(exploratory drilling at Pachacharapalayam site)

Eocene

sandstone

Mio-pliocene

sandstone

Principal aquifer(Sandstone)

(Cuddalore

formation)

(Neyveli

formation)

Marker bed

Inference :

Multi-layered aquifer system (down to explored depth of 364 m)

18 nos of additional

exploratory wells were

drilled.

Outcome from exploratory drilling

CGWB Rig

Litholog at drilling site

Pacharapalayam

40 Laterite

Aquifer -I

Ayekuppam

SST

Kothandarajapuram

20

Aquifer -I

Aquifer -I

0 SST msl

Bay of Bengal-20 SST

Clay Clay-40

SSTAquifer -II

SSTAquifer -II-60

Clay

-80 Lignite/clay Lignite

SSTAquifer -III

SST Clay

-100 SST

Lignite ?? Clay

-120 SST Lignite

Aquifer -III

-140 Lignite

Aquifer –III

SST

-160 SST

-180

-200Clay

-220

SST Aquifer -IV

Clay

-240

-260

-280

-300

-320

-340

Piezometric Heads of Aquifer - III

Inference:

1. The variation of Piezometic heads reaffirms the presence of 4 aquifer

units & its nature (unconfined/confined) within the principal aquifer. (Aq-1 –

unconfined, II, III & IV – Confined)

2. The Pz head (long tern hydrograph) infers distinct recharge & discharge

mechanisms in all 4 aquifer units.

3. Individual aquifer management plan for each aquifer unit is required.

Q = 29 lps

Q= 48 lps

Q = 14 lps

Q= 10 lps

Clay discontinuous

Outcome from Pz head analysis

Pz

he

ad in

msl

Aquifer – I (Unconfined)

Aquifer – III (confined)

Aquifer –IV I (confined)

Aquifer – I (Unconfined)

Aquifer – I (Unconfined)

Aquifer – I (Unconfined)

Aquifer – I (Unconfined)

Aquifer – II (confined)

Domestic &

irrigation

irrigation

Industrial &

irrigation

Drinking water

supply to

chennai city

Micro-level aquifer mapping (Aquifer Information System) Less

potential

zones

Less potential

zones

Less potential

zons

Outcome

To be shared to farmers, local administration for participatory GW management.

0 km 10 km

0 m

300 m

scale

Bay of Bengal

Aquifer Unit – I

(unconfined)

Aquifer Unit – I

(unconfined)

Aquifer Unit – III

(unconfined)

Aquifer Unit – IV

(confined)

Aquifer Unit – II

(unconfined)

3 D Aquifer Disposition (Kurinjipadi Block), Cuddalore District, Tamilnadu

Mio-pliocene sandstone

Mio-pliocene sandstone

Eocene sandstone

Eocene sandstone

Outcome

west east

Pacharapalayam

40 Laterite

Aquifer -I

Ayekuppam

SST

Kothandarajapuram

20

Aquifer -I

Aquifer -I

0 SST msl

Bay of Bengal-20 SST

Clay Clay-40

SSTAquifer -II

SST

Aquifer -II-60

Clay

-80 Lignite/clay Lignite

SSTAquifer -III

SST Clay

-100 SST

Lignite ?? Clay

-120 SST Lignite

Aquifer -III

-140 Lignite

Aquifer –III

SST

-160 SST

-180

-200Clay

-220

SST Aquifer -IV

Clay

-240

-260

-280

-300

-320

-340

Groundwater quality of all four aquifer units

Inference:

1. Again re-confirms the presence of four distinct

aquifer units

2. All the 4 aquifer units have potable GW (insitu

Brackish GW exists as pockets near coasts)

EC : 550 µS/cm

EC : 1000 µS/cm

EC : 120 µS/cm

EC : 250 µS/cm

unconfined

confined

confined

Outcome from hydrochemical studies

Regional Conceptualization Cuddalore Coastal Aquifer.

Mio-pliocene

sandstone

Recent alluvium

and sst...

20 – 120 m

20 - 180 m

40 – 240 m

40 – > 400 m

Depth of

Occurrence

Multi-layered aquifer system(Seven Layer model)

Layer – 1 (sand/sandstone)

Layer – 2 (clay- discontinuous)Layer- 3 (Sandstone)Layer – 4 (Clay/lignite – discontinuous)Layer – 5 (Sandstone)Layer – 6 (Clay – discontinuous)Layer – 7 (Sandstone)

Depressurization for mining activity

User aquifer for Irrigation.

Abstraction for

Domestic &

Irrigation

Abstraction for drinking water supply to chennai city

Explored depth : 400 m

Q (10 – 45 lps)

Q (8 – 40 lps)

Q (10 – 40 lps)

Q (5 – 15 lps)

0 km 72 km31 km

Outcome of the Study

River flows during rainy season only

- River (Ponnaiyar, Gadilam & Vellar)

flows for 40 days in a year

- No significant base flow to the river.

Perumal eri/tank (10 km width & 3 Km

wide) taken as General Head boundary

(water in tank remains almost same throughout).

Numerical Modelling for Aquifer Management Plan: Model Grid, Boundary conditions & input parameters.

Total model area : 1948 sq. km.

Total Cells : 34629 nos

Columns and Rows : 51 and 97

Layers : 07 nos

Coarser grid : 1000 x 1000 m

Finer grid : 500 x 500 m

(Grid pattern is based on the data availability & objective of

the model)

Con

sta

nt H

ea

d B

ou

ndary

(S

ea

)

Variable head boundary (Vellar River)

Finer gird(250 m x 25 m)

(10

00

m x

10

00

m )

Co

arse

r G

rid

Variable head boundary (Ponnaiyar River)

Recharge rate: 12 - 14 % of the

annual recharge (1290 mm/yr).

Method : Finite Difference Method (FDM)

GW Flow equation

7 layer model

Hydraulic conductivity (Kx) values as input : K = 30 – 40 m/day

Specific Yield : 12 – 14 % (unconfined, Aquifer – I)

Storativity : 0.003 to 0.000093 ( confined aquifer II, III & IV)

Mining activity

Pre-pumping For Irrigation

Cumulative effect of groundwater withdrawal for irrigation, mining activity, drinking water supply & domestic purpose

1950 2000 20101970 1990

Total Pumpage(MCM/yr)

1960 1980

200

400

600

800

1000

Period in years

Aquifer Hydrogeologic Unit Irrigation Industrial Domestic

(GW withdrawal in mcm/yr)

----------------------------------------------------------------------------------------------------------------------------------------------

Sand/sandstone Upper Cuddalore (Aq-I) 393.0 0.8 30.0

Sandstone Lower Cuddalore (Aq-II) 611.65 1.2

Sandstone Upper Neyveli (Aq-III) 31.0 133.10

Sandstone Middle Neyveli (Aq-IV) 12.79*

Sandstone Lower Neyveli (no groundwater withdrawal)

------------------------------------------------------------------------------------------------------------------------------------------------

Total 1035.69 135.10 42.79

---------------------------------------------------------------------------------------------------------------------------------------------------*Groundwater withdrawal for drinking water supply to Chennai city during lean periods.

Groundwater withdrawalfrom aquifer units (I,II,III & IV) from Cuddalore coastal aquifer system

Total annual Groundwater withdrawal from all Aquifer

Units : 1213.58 mcm

Total annual pumping from Neyveli mine : 133.10 mcm

Outcome from numerical modelling studies

S. No Management Options

Groundwater

withdrawal as

on Dec 2013

mcm/year

Impact on Aquifer Units

Aquifer

Unit –I

Aquifer

Unit –II

Aquifer

Unit -III

Aquifer

Unit-IV

All Aquifer Units1. Future projection upto

year 2025 with present

rate of groundwater

pumping.

1213.58 No significant

change

Head decline 0.10 to 0.20 m /yr

Head Decline0.10 to 0.15 m/yr

No significant

change

2. Drought Occurrence once

in four years with present

rate of pumping.

1213.58 No significant

change

No significant

change

No significant

change

No significant

change

Aquifer I & II3. 350 mcm/year increase in

irrigation pumping from

AQ-I & II (1213.58 + 350

mcm)

1213.58 Head decline 0.10 to 0.20m /yr

Head decline 0.20to 0.30 m /yr

No significant

change

No significant

change

4. Increase in groundwater

pumping for industrial activity

along the coastal tract by 100

mcm from aquifer-II (proposal

for SEZ zone and textile sipcot)

1213.58 No impact Head decline 0.10

to 0.20 m/yr

(impact 0 – 5 km

along the coastal

tract)

No Impact No Impact

Aquifer Management Plan (Cuddalore coastal aquifer) Outcome from numerical modelling

S. No Management Options

Groundwater

withdrawal as

on Dec 2013

Mcm/year

Impact on Aquifer Units

(Aquifer Unit –I) (Aquifer Unit –II) (Aquifer Unit -III) (Aquifer Unit-IV)

Aquifer Unit III5 Increase in annual groundwater

pumping for mining activity by 60

mcm from Aquifer-III

(133 + 60 mcm) (proposal for

expansion of mine (mine III)

1213.58

(Neyveli

pumping :

133.10 mcm/yr)

No impact Cone of depression

increased by 200 m.

(impact around 10

km radius)

Cone of depression

increased by 200 m.

(impact around 10 km

radius)

No Impact

6 Increase in annual groundwater

pumping for mining activity by 130

mcm from Aquifer-III

(133 + 130 mcm) (proposal for

expansion of mine (mine III & IIIA)

1213.58

(Neyveli

pumping :

133.10 mcm/yr)

No impact Cone of depression

increased by 400 m.

(impact around 10

km radius)

Cone of depression

increased by 400 m.

(impact around 10 km

radius)

No Impact

Aquifer IV7 Increase in annual groundwater

withdrawal by 6 mcm from

Aquifer – IV (12.79 + 6 mcm/yr)

During drought period in chennai

1213.58

(Drinking water

supply : 12.79

mcm/yr)

No impact No impact No Impact No Impact

Aquifer Management Plan – (Cuddalore Coastal Aquifer)

• With the present prevailing scenario (1213.58 mcm/year), the aquifer is safe and

no threat of seawater intrusion exists.

• Aquifer – I & II are vulnerable to seawater intrusion (0 – 5 km from coast) if the

annual GW withdrawal increases by 350 mcm.

Outcome from numerical modelling

Pre-pumping condition ( - 2 m)

Present Pz head (-10 m)

Safe Pz head (- 50 m)

Unsafe Pz head (- 80 m)

Piezometer

Pumping well

35 km 17.5 km 0 km

Aquifer Management Plan (for Aquifer – III)

• for monitoring the threat of sea water intrusion

• 0 – 10 km inland coast : The safe Pz head is to be

maintained as - 40 m to - 50 m w.r.to msl.

• Pz head below - 80 m bmsl shall invite sea

water intrusion.

Major issues : Pumping for safe mining of lignite (depressuration) & pumping for irrigation by farmers at pockets.

Present Pz head

Aquifer - III

First

Aquifer - I

(Sandstone)

Aq – IV(Sandstone)

Sixth layer (Clay)

Aquifer - III (Sandstone)

•Rainfall

Recharge

Aquifer -I (Sandstone)

Aquifer - IV (Sandstone)

Aquifer -II (Sandstone)

Aquifer -III (Sandstone)

Probable Basement (4500 m)

(Granitic Gneiss)

Groundwater Flow {vertical & Lateral Flow}

Neyveli Lignite Mine

Groundwater flow simulation ( Groundwater Model) – Cuddalore Coastal Aquifer

(Vertically exaggerated)

• With the present prevailing scenario (1213.58mcm/year), the aquifer is safe and no threat ofseawater intrusion exists.

• Aquifer – I & II are vulnerable to seawaterintrusion (0 – 5 km from coast) if the annual GWwithdrawal increases by 350 mcm.

Aquifer management plan

Aquifer - II

(Sandstone)

Bay of Bengal

Aquifer - IV

clay

clay

Lignite

clay

clay

clay

clay

clay

unconfined

confined

confined

Reversal in hydraulic gradient (sea water intrusion) may take

place if annual groundwater withdrawal exceeds by 700 mcm for

Aquifer – I & 900 mcm for Aquifer – II.

As annual estimation of GW withdrawal from the aquifer is a

voluminous exercise, sustainable management of the Cuddalore

coastal aquifer can be done by monitoring the GW head

(Piezometers) fitted with high frequency Automatic WL

Management strategy

for Aq-1 & II

• Thanks…….