ASSESSMENT OF GROUNDWATER POTENTIAL USING
ISOTOPIC, GEOCHEMICAL AND NUMERICAL MODELING
TECHNIQUES (a case study of Lahore aquifer)
BY
DR. NIAZ AHMAD
Principal Scientist (Geology)
Isotope Application Division
PAKISTAN INSTITUTE OF NUCLEAR SCIENCE AND TECHNOLOGY
OVERVIEW OF THE TALK
•
•
•
•
•
Evolution of Indus River System
Aquifers and Groundwater
Recharge and Discharge
Groundwater Quantity and Quality
Case Studies: Lahore Aquifer
EVOLUTION OF INDUS RIVER
SYSTEM
• As the Himalayas gained their maximum height, the
present watershed system of Indus, Brahma-Putra and
Ganges emerged and attained the present geographical
position
• The course of the rivers Indus, Brahma-Putra, Ganges and
their tributaries is constantly changing, as the slope of the
land is changing due to tectonic stresses
• The Himalayas are still rising but due to erosion, they have
attained a steady height
• The river systems are responsible for the development of
thick pile of sediments (~2 KM thick) to the south from
Himalayan foothills to the Arabian Sea Delta
• The alluvial sediments constitute aquifers which store huge
amount of fresh water which is termed as groundwater
IMPORTANT FEATURES OF GROUNDWATER
• Upper part of Lithosphere (approximately 1 KM) supports fresh
groundwater aquifers
• To the depth of approximately 800 meters below the water table,
about
4 million cubic kilometers of water is present (Singh, 1992)
• In the upper 800 meters of the continental crust, the groundwater
volume is 3000 times greater than that of all the rivers at any one
time and about 20 times greater than the combined volume of
water in all the rivers and lakes together.
• Surface water bodies (Rivers & Lakes) respond rapidly to rain
events but;
• Groundwater has a much longer natural accumulation and
discharge time
Total Amount of Groundwater
Available in Pakistan
• Fresh groundwater is present along the
rivers about 10 km to each side to the depth
of 1 km
• Total amount of fresh groundwater is about
25000 km3
•
IMPORTANT FEATURES OF GROUNDWATER
• Groundwater is buffered against short-term weather and climate processes
• The huge reserves of fresh groundwater are not being renewed wholly every
year when compared to exploitation rate by pumping
• Large scale tapping of aquifers is virtually equivalent to a process of nonrenewable mining for water
• It moves through the geological materials at a slower rate and residence times
in the 10’s, 100’s and even 1000’s of years are not uncommon (Freeze and
Cherry, 1979)
• Because of its long residence time in aquifers, groundwater is highly vulnerable
for pollution and overexploitation by pumping
• overexploitation leads to salinization
• Knowledge of the recharge rate is essential for managing the sustainable
extraction of potable water
Composition of Aquifers
• The Indus Basin alluvium consists of alternating
layers of clay, silt, sand and gravels deposited by
meandering rivers in different proportions
• The source materials originate from the erosion of
rising Himalayan rocks
• Groundwater quantity in an aquifer depends on the
transmission and storage properties of that aquifer
• Chemistry of the rocks plays vital role in the
evolution of groundwater quality
Composition of Aquifers
---------cont
• The aquifers are constantly recharging from the
watershed areas and the resulting groundwater is
flowing towards the sea
• In the way groundwater is interacting with the
surrounding rocks and dissolving the chemical content
• Due to its high dielectric constant, water is the excellent
solvent
• With dissolving salts its hunger for dissolving more
salts increases, its salinity increases with time
• Due to mixing of fresh water in the way, groundwater
maintains its quality
• Due to global warming if the precipitation patterns
change and the drought periods extend, the
groundwater quality will also be affected as a result of
less fresh water recharge
EXPLOITATION OF GROUNDWATER
• With the dawn of scientific era and development in petroleum
industry, it is now possible to drill a well even more than 1
kilometer depth
• Since 1960, a large number of tube wells were installed to extract
groundwater for agriculture and drinking purposes
• Recharge is an important component of groundwater, if recharge
and discharge do not match overexploitation starts
• Over-exploitation gives way to problems of pollution, salinization,
increased cost of water extraction and resource depletion
Important Diagnostics of Groundwater
Before Exploitation
•
•
•
•
•
Identification of recharge mechanism
Surface water/ Groundwater interaction
Transmission/storage properties of aquifers
Residence time of water within the aquifer
Water quality (physical, chemical &
biological)
Tools for Investigation
•
•
•
•
Isotopes
Chemical analyses
Mathematical
Geophysical (resistivity, seismic etc)
Case Studies: Lahore Aquifer
• IDENTIFICATION OF RECHARGE
MECHANISM
Identification of Recharge Mechanism of Lahore Aquifer using
18O Isotope Information
GMWL
-20
-30
60
Rain
50
-40
D
(‰)
40
DR
30
-50
20
Ravi
-60
10
GMWL
LCW
-70
0
BRBDC
-9
-80
-12
-11
-10
-9
-8
18O (‰)
-7
-6
-5
-4
-8
-7
-6
-5
Frequency histogram of 18O (‰)
-4
Identification of recharge mechanism in deep groundwater of
Lahore aquifer by 18O concentrations in 2006
Bund Road
-6.5
g
zan
o
M
-7.5
0
ad
pur Ro
Feroze
Rai
lwa
y Li
ne
Model Town
5 km
Scale
-8.5
3D view of 18O concentration of deep groundwater of Lahore
in 2006
AN INNOVATIVE FINDING OF A
GEOLOGIC FAULT
An innovative finding is reached based on the temperatures in the
wells
Temperatures above normal are found in a linear belt in NE-SW
direction
The anomalous increase in temperatures is interpreted as the
presence of active geologic fault in the Lahore area
Due to sliding of the fault, frictional heat is generated, which is
increasing the temperatures of the groundwater in contact with the fault
area
3500000
SH-3
SH-4
SH-1
192
Temperature Variation 0C
3495000
123
24 - 27.9
28 - 31.9
32 - 33.9
34 - 35
149 191
55 148
57 194
180
38
77
74
68
152
75
168
167
Geo
logi
cF
ault
Line
206
3470000
425000
195
196
200
202
162
117
110
163
3475000
217
161
106
205
112
N
160
201
157
3480000
214
212
159
104
187
213
158
169
80
156
70
3485000
186
184 210 208209 188
182
189
207
211
151
66
174
137
185
76
63
173
172
175
128
153
60
61
147
150
14
176
154
62
155
190
178
179 40
59
16
170
7
146
53
3490000
169-A
147
54
181
44
171
198 197
216
215
199
183
165 204
118
203
27
164
430000
435000
166
440000
445000
Water Supply from Lahore Aquifer
•Whole supply to the public and industry is from groundwater reservoir
•About 400 tube wells (each ~2.5cusecs) are in operation under the
jurisdiction of WASA, LDA -About three fourth of WASA is extracted
by private stakeholders
•Total abstraction is about 800 million gallons per day
•We can say a canal of the size of Lahore Canal is operating from the
aquifer to the surface
•Water table is lowering at the rate of 2.5 feet per year
•Aquifer capacity is depleting every year
•A large depression cone is producing surrounding the Mozang area
•As a result more saline water is intruding the aquifer from the south
Water Table Conditions of Lahore Aquifer
In 1960 before pumping, water table was at 210 m above
mean sea level, about 5 to 6 meter below surface
In 1989, a depression cone is visible at Mozang area as a result of
pumping, Water table lowered to 191 m from 210 m amsl, i.e.
Water table lowered 19 m from 1960 @ 1m / year
N
Mozang
0
2 km
Scale
In 1998, Water table further lowered to 185 m from 191m in 1989
R av
i Ri
v er
i.e. lowered 6 m further in 9 years
Mozang
N
0
2 km
Scale
Industrial Area
Military Engineering
Services
Green Town
Township
Shahdara
Mozang
Data Nagar
Garden Town
Allama Iqbal Town
Mustafabad
Mughal Pura
Shimla Hill
Ravi Road
City
Baghbaan Pura
Misri Shah
Gulberg Sub Div
Ichhra Sub Div
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
Samanabad Sub Div
Islam Pura Sub Div
Depth to Water Table (m)
In 2003, maximum water table depths are at Mozang and Ichhra
i.e, 36 m below surface which was 5 m in 1960
Maximum Water T able Depth
Average Water T able Depth
Minimum Water T able Depth
Salinization Problem of Lahore Aquifer
• EC and Cl can be used to determine the salinity condition
of Lahore aquifer
• Chloride is more reliable as it is considered a conservative
anion due to its less participation in chemical reactions
• Spatio-temporal measurements of chloride could be
reasonably used to determine the increase of salinity in an
area
• Once the water enters the geologic formations, its salinity
goes on increasing with the passage of time. It changes
from fresh water to brackish water and then to brine.
Salinity of water could only be decreased by mixing of
fresh water in the way.
EC (S/cm at 25 0C)
av
R
r
ve
i
R
i
Bund Road
840
790
M
oz
an
g
nal
re Ca
o
h
a
L
740
690
640
590
540
To
del
Mo
wn
490
u
ze P
Fero
5 km
440
Scale
ad
r Ro
Ra
ilwa
yL
ine
0
EC contours of deep groundwater in 2006, Lahore area
390
340
EC (S/cm at 25 0C)
3D view of EC parameter
Cl (ppm)
47
45
43
41
Mozang
39
37
o ze
Fer
Pur
35
d
Roa
Mod
el To
wn
33
31
5 km
Ra
ilw
ay
Lin
e
0
29
Scale
27
Contours of chloride measured in deep groundwater of Lahore aquifer in 2006
3D view of chloride concentration
water table contours
Chloride contours
43
41
Mozang
R av
i Ri
45
v er
47
Mozang
N
39
37
o ze
Fer
Pur
35
d
Roa
Mod
el To
wn
33
31
0
5 km
Ra
ilw
ay
Lin
e
0
29
Scale
27
2 km
Scale
Reasons of Salinization
•
•
•
•
•
Lahore has a large network of unlined sewerage drains
Water is leaking from these drains to shallow aquifer
Salinity of shallow aquifer is increasing
A large depression cone has developed in the Mozang area
As the aquifer is unconfined, Shallow saline groundwater
is making its way to the deep aquifer , where it is mixing
with the deep relatively fresh groundwater
• As a result, the salinity of deep aquifer is increasing in the
central city area (Mozang, Ichhra, Gawal Mandi, Assembly
Hall)
Water Types of Lahore Aquifer
• Major chemical ions dissolved in groundwater are Ca, Mg,
Na, K, CO3, HCO3, SO4 and Cl
• Concentrations of these ions should be determined before
use at homes, industry and agriculture
• There are different graphical methods for classification of
groundwater types in an area
HYDROCHEMICAL
EVIDENCE OF LAHORE
AQUIFER
About 175 samples were collected from Shallow and Deep aquifer,
Canals, Drains and River Ravi
EC, pH and Temperature were measured in the field
Major Cations (Na, K, Ca, Mg) and Anions (carbonates,
bicarbonates, sulfate, chloride) were analyzed in the
laboratory
For interpretation cations and anions were lumped into
three variables respectively
Their milli-equivalent/L percentages were calculated
80
Water Types
Shallow
Deep
Sewerage
Canal
River
60
A TRILINEAR GEOCHEMICAL
MODEL REPRESENTING
DIFFERENT GROUNDWATER
TYPES IN THE LAHORE AREA.
THE METHODOLOGY OF THE
TRILINEAR MODEL WAS
DEVELOPED BY PIPER (1944)
80
60
40
40
20
20
Mg
SO4
80
80
60
60
40
40
20
20
80
Ca
60
40
20
20
Na+K
HCO3+CO3
40
60
80
Cl
SO4
Water Types
80
Shallow
Deep
Sewerage
Canal
River
60
40
20
HCO3
Na+K
80
60
40
20
Mg
80
60
40
20
Ca
20
40
60
80
Cl
A DUROV
GEOCHEMICAL MODEL
REPRESENTING
DIFFERENT
GROUNDWATER TYPES
IN THE LAHORE AREA.
THE METHODOLOGY OF
THE MODEL WAS
DEVELOPED BY A
RUSSIAN SCIENTIST
DUROV (1948)
INNOVATIVE MULTI-RECTANGULAR DIAGRAMS
(MRDs) DEVELOPED AT PINSTECH
Classification of water types using innovative MultiRectangular Diagram Model
HCO3 ( meq / l % )
SO4 ( meq / l % )
Cl ( meq / L % )
100
50
7
calcium bicarbonate
100 0
magnesium bicarbonate
50
sodium bicarbonate
0100
sodium chloride
49
69
50
0
0
18
0
100
100
50
0
Ca ( meq / L % ) Mg ( meq / L % )
50
50
100
Na ( meq / L % )
Important benefit of MRDs classification of
groundwater are;
•Groundwater types are clearly singled out, which
is not possible by previous diagrams
•It also helps to mark the zones with different
groundwater quality by plotting a representative
symbol on the location from where the sample is
collected.
•i.e, Hydro-chemical facies maps can be prepared
Water types differentiated with MRDs and plotted on the
sample collection locations in the area
Calcium Bicarbonate
Magnesium Bicarbonate
Sodium Bicarbonate
Sodium Sulfate
Sodium Chloride
SH-2
SH-5
SH-3
SH-4
SH-1
192
123
149 191
55 148
57 194
146
180
54
38
178
181
61
150
190
77
152
75
213
158
151
217
159
104
160
168
167
106
196
195
201
157
calcium bicarbonate type
214
80
70
sodium bicarbonate type
212
169
156
177
137
186 187
208
184 210
209 188
182
189
207
211
76
74
66
68
174
176
185
153
147
173
172
128
154
60
155
14
7
179 40
59
63
16
170
175
53
62
44
171
169-A
126
161
200
198 197
216
215
199
202
183
205
206
163
112
162
117
110
165 204
118
0
10 km
203
27
Scale
164
166
History of movement of groundwater
interpreted with chemical ions I.e. Sodiumcalcium relationship in Lahore
90
80
350
70
300
60
250
50
200
R-Ravi-1
40
150
30
100
20
R-Ravi-2
BRBD
LH-Canal
50
10
0
0
0
20
40
60
80
100
0
10
20
30
40
50
60
70
80
Sewerage Contamination of Lahore Aquifer
• Groundwater from all the sampled wells (111) was tested
for Coliform bacteria to observe the sewerage
contamination
• It appears in 15 wells
• Five wells were tested in Shahdara Area, coliform
appeared in all these wells
• Water seepage from sewerage drains is polluting the deep
good quality groundwater
• On the other hand, Sewerage water from all the city is
disposed of to the river Ravi without any treatment. As the
river Ravi is recharging the underground aquifer, sewerage
water is also seeping to the deep aquifer thereby polluting
it
Legend
coliform count
well No.
11
3
SH-5
38
SH-4
High SH-2
High
SH-3
SH-1
2
154
5
3
150
2
74
151
1
1
2
169
156
70
9
0
10 km
165
2
3
Scale
27
164
Location of pumping wells infected by fecal coliform
GROUNDWATER FLOW AND CONTAMINANT
TRANSPORT MODELING
• CASE STUDIES of LAHORE
USE OF MODELING TOOLS IN
GROUNDWATER AQUIFERS
• Modeling tools helps for ASSESSMENT &
MANAGEMENT OF AQUIFERS
WHAT IS A MODEL
• A model is any device that represents an
approximation of a field situation
• Physical models (sand tanks; simulate
groundwater flow directly)
• Mathematical models simulate groundwater
flow indirectly by means of a governing
equation thought to represent the physical
processes that occur in the system
• A model is not a replica
of reality
• Rather, a structured
environment for thinking
through a problem
WHY MODELS ?
Groundwater Hydrologists are often called
upon to predict the behavior of groundwater
systems by answering questions like:
WHY MODELS ?
• What changes can be expected in groundwater
levels in the aquifer beneath Lahore in the year
2020
• How will a change in stream stage (River Ravi)
affect the water table in an adjacent alluvial
aquifer
WHY MODELS ?
• What is the capture area for a well field that
furnishes municipal water supplies to the city
• What is the most likely pathway of contaminants
if the toxic materials enter the groundwater
environment
FLOW MODELS
Are used to estimate the spatial and temporal
variation of quantity of water in the
aquifers
TRANSPORT MODELS
• Are used to assess the contaminant transport
behavior in groundwater regime leaked
from
• Landfill sites
• radioactive repositories
• other sources
AdvectionDispersion
Equation solved by
MT3D
 D C 
ij
x
x
i
j
Dispersion
-

x
(vi C ) +
i
Advection
q
s Cs

-  [C + b S] = R  C 
Sink/Source

Reactions
t
Retardation
Aquifer Main Features
• 400+ m thick Quaternary Alluvial Deposits
(Sands with clay lenses)
• High K = 26 to 158 m/d
• Sy = 0.07 - 0.25
• Recharge Rates = 40 - 100 mm/yr
• Irrigation canals and influent river Ravi
• Over-pumping in Lahore
Countours of water level observations in Nov. 1989
N
0
2 km
Scale
FLOW MODEL OF LAHORE
AQUIFER
A Model was developed, which is digital
equivalent to actual Lahore aquifer
DATA NAGAR
ASSEM BL Y HAL L
M UGHAL PURA
SADAR BAZAR
LAHORE CITY
CITY
CANTONM ENT
GUL SHAN_ E_ IQBAL PARK
M ODEL
TO WN
BR BD CANAL
RA
VI
RI
VE
R
N
UPPER C HE
NAB C AN AL
Ymax= 3531000 m
74 E
Ymin = 3439000 m
31 15 N
Xmin = 391000 m
Distance= 79 Km
Xmax = 470000 m
Map of Lahore on UTM Coordinates
Aquifer layers constructed from bore hole lithologic logs
Cross-sectional view of model layers in Visual Modflow
Plan view of the model area showing:
River boundaries
Constant Head Boundary(NE)
General Head Boundary(NW)
Inactive Cells
Grid Mesh
Pumping Wells in the Visual Modflow
Ravi River
Lahore Canal
Steady State calculation before pumping
Groundwater Flow Conditions
1910 - Pre-pumping
1960 - beginning of pumping
Contours of calculated heads with steady state model in 1989.
Model also shows two depression cones as shown in observed head contours.
These heads were used as initial heads in transient simulations
Countours of water level observations in Nov. 1989
N
0
2 km
Scale
Calculated Water Table Contours in 1998
Mozang
N
0
2 km
Scale
Water table contours above mean sea level (meters) in Nov. 1998
3D view of transient flow model
Depression cone is visible
Water is crossing underneath the River Ravi and Lahore Canal
Predicted water table contours in 2018 by Visual Modflow
DELINEATION OF WELL HEAD
PROTECTION ZONE
Transient transport simulation:
Particles introduced at one of the waste disposal
site are captured by the screens of pumping wells
CONCLUSIONS
• Water table of Lahore aquifer is lowering down at a
rate of about 3 feet per year
• A depression in the water table has produced
• Generally, deep aquifer (≥ 200 m) has less salinity as
compared to shallow aquifer (≤ 50 m). Sewerage drains
are adding salinity to shallow aquifer. Deep aquifer is
getting saline in the areas where water table has
maximum depth. This salinity increase is due to mixing
of more saline shallow water with deeper fresh water
under the action of high hydraulic gradient.
• Groundwater of Lahore Aquifer consists of calcium
bicarbonate, magnesium bicarbonate and sodium
bicarbonate types
CONCLUSIONS
------continued
• chloride is found Dominant underneath the central city
area (Assembly Hall, Mozang, Nisbat Road etc.) in both
shallow (motor pumps/hand pumps) and deep (WASA
wells) aquifer. This is the area where highest decline in
water table exists as a result of pumping.
 There are strong indications that waters of shallow and
deep aquifer are mixing together in the area of
dominance of chloride. If the leachates from industrial
waste enters into shallow aquifer, then there is strong
chance that the deeper fresh aquifer will get polluted
also. Pumping from this central area needs a great care.
CONCLUSIONS
------continued
 There are strong indications that waters of shallow and
deep aquifer are mixing together in the area of
dominance of chloride. If the leachates from industrial
waste enters into shallow aquifer, then there is strong
probability that the deeper fresh aquifer will get
polluted also. Pumping from this central area needs a
great care.
 Biological quality in some areas is not good as
Sewerage contamination is detected in some areas
 It is obvious from these findings that Aquifer is
vulnerable for pollution more in the central city area
Recommendations
• Formulation of a rational water supply policy is needed through
which Lahore aquifer should be managed by coordination of all
the stake holders including Government of Punjab, WASA
Lahore, Cantonment Boards, private societies, industrialists and
public.
• During modeling exercise, it has been observed that wells are
not placed at optimized distances. At least well to well distance
should be kept 1.5 kilometer. If the wells are installed shorter
than this distance, their depression cones will overlap with the
result of increased lowering in water table.
• In the depression cone area some of the wells must be shutdown
observing the well to well distance as proposed above.
• New wells should be installed near BRBD Canal and installing
wells within the city should be discouraged.
•
Recommendations ---cont
• Quality of sewerage water should be improved in treatment
plants before disposing it of in the river Ravi.
• There is a strong need to install a peizometer network to gather
data on water table fluctuation. At present this data is acquired
directly from the pumping wells. It is not representative
hydraulic head data, as the pumping wells induce perturbation in
the system. An automatic telemetric system is suggested.
• Periodic monitoring of chemical and biological quality of water
is suggested.
• Supervision of Total Quality Management (TQM) is
recommended through national scientific organizations such as
PINSTECH, PCRWR, PCSIR, EPA etc., other than WASA
Lahore and Cantonment Boards.
THANKS