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…….