1. 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

2. OVERVIEW OF THE TALK Evolution of Indus River System
Aquifers and Groundwater
Recharge and Discharge
Groundwater Quantity and Quality
Case Studies: Lahore Aquifer

3. 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

4. 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

5. 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 km3

6. 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 non-renewable 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

7. 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

8. 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

9. 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

10. 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)

11. Tools for Investigation
Isotopes
Chemical analyses
Mathematical
Geophysical (resistivity, seismic etc)

12. Case Studies: Lahore Aquifer
IDENTIFICATION OF RECHARGE MECHANISM

13. Identification of Recharge Mechanism of Lahore Aquifer using 18O Isotope Information
Frequency histogram of 18O (‰)
18O (‰)

14. Identification of recharge mechanism in deep groundwater of Lahore aquifer by 18O concentrations in 2006
River Recharge
Mixed Recharge
Rain Recharge

15. 3D view of 18O concentration of deep groundwater of Lahore in 2006

16. 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

18. 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

19. 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

20. 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 1m / year

21. In 1998, Water table further lowered to 185 m from 191m in 1989
i.e. lowered 6 m further in 9 years

22. In 2003, maximum water table depths are at Mozang and Ichhra
i.e, 36 m below surface which was 5 m in 1960

23. 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.

24. EC (S/cm at 25 0C)
EC contours of deep groundwater in 2006, Lahore area

25. EC (S/cm at 25 0C)
3D view of EC parameter

26. Cl (ppm)
Contours of chloride measured in deep groundwater of Lahore aquifer in 2006

27. 3D view of chloride concentration

28. water table contours
Chloride contours

29. 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)

30. 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

31. 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

32. A TRILINEAR GEOCHEMICAL MODEL REPRESENTING DIFFERENT GROUNDWATER TYPES IN THE LAHORE AREA. THE METHODOLOGY OF THE TRILINEAR MODEL WAS DEVELOPED BY PIPER (1944)

33. 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)

34. INNOVATIVE MULTI-RECTANGULAR DIAGRAMS (MRDs) DEVELOPED AT PINSTECH

35. Classification of water types using innovative Multi-Rectangular Diagram Model

36. 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

37. Water types differentiated with MRDs and plotted on the sample collection locations in the area

38. History of movement of groundwater interpreted with chemical ions I. e
History of movement of groundwater interpreted with chemical ions I.e. Sodium-calcium relationship in Lahore

39. 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

40. Location of pumping wells infected by fecal coliform

41. GROUNDWATER FLOW AND CONTAMINANT TRANSPORT MODELING
CASE STUDIES of LAHORE

42. USE OF MODELING TOOLS IN GROUNDWATER AQUIFERS
Modeling tools helps for ASSESSMENT & MANAGEMENT OF AQUIFERS

43. 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

44. A model is not a replica of reality
Rather, a structured environment for thinking through a problem

45. WHY MODELS ?
Groundwater Hydrologists are often called upon to predict the behavior of groundwater systems by answering questions like:

46. 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

47. 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

48. FLOW MODELS
Are used to estimate the spatial and temporal variation of quantity of water in the aquifers

49. TRANSPORT MODELS
Are used to assess the contaminant transport behavior in groundwater regime leaked from
Landfill sites
radioactive repositories
other sources

50. Advection-Dispersion Equation solved by MT3D
 Dij C  -  (vi C ) + qs Cs -  [C + b S] = R  C 
xi xj xi    t
Dispersion Advection Sink/Source Reactions Retardation

52. Aquifer Main Features
400+ m thick Quaternary Alluvial Deposits (Sands with clay lenses)
High K = 26 to 158 m/d
Sy =
Recharge Rates = mm/yr
Irrigation canals and influent river Ravi
Over-pumping in Lahore

54. FLOW MODEL OF LAHORE AQUIFER
A Model was developed, which is digital equivalent to actual Lahore aquifer

55. Map of Lahore on UTM Coordinates

56. Aquifer layers constructed from bore hole lithologic logs

57. Cross-sectional view of model layers in Visual Modflow

58. Plan view of the model area showing:
River boundaries
Constant Head Boundary(NE)
General Head Boundary(NW)
Inactive Cells
Grid Mesh

59. Pumping Wells in the Visual Modflow
Ravi River
Lahore Canal
BRBD Canal

60. Steady State calculation before pumping

61. Groundwater Flow Conditions
Pre-pumping
beginning of pumping

62. 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

64. Calculated Water Table Contours in 1998

66. 3D view of transient flow model
Depression cone is visible
Water is crossing underneath the River Ravi and Lahore Canal

67. Predicted water table contours in 2018 by Visual Modflow

68. DELINEATION OF WELL HEAD PROTECTION ZONE

69. Transient transport simulation:
Particles introduced at one of the waste disposal site are captured by the screens of pumping wells

71. 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

72. 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.

73. 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

74. 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.

75. 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.

76. THANKS