ASSESSMENT OF GROUNDWATER POTENTIAL USING ISOTOPIC, GEOCHEMICAL AND NUMERICAL MODELING TECHNIQUES (a case study of Lahore aquifer) - PowerPoint PPT Presentation

Loading...

PPT – ASSESSMENT OF GROUNDWATER POTENTIAL USING ISOTOPIC, GEOCHEMICAL AND NUMERICAL MODELING TECHNIQUES (a case study of Lahore aquifer) PowerPoint presentation | free to download - id: 44550c-MDFmZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

ASSESSMENT OF GROUNDWATER POTENTIAL USING ISOTOPIC, GEOCHEMICAL AND NUMERICAL MODELING TECHNIQUES (a case study of Lahore aquifer)

Description:

Allama Iqbal Road Canal. Habib Ullah Road. Children Park Ghari Shahu Ghazi Mohalla. Baja Line. Mian Mir Pind New. Habib Ullah Road Old (12) ALLAMA IQBAL TOWN SUB DIVISION – PowerPoint PPT presentation

Number of Views:689
Avg rating:3.0/5.0
Slides: 77
Provided by: MUBA8
Learn more at: http://ranjha.tintash.com
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: ASSESSMENT OF GROUNDWATER POTENTIAL USING ISOTOPIC, GEOCHEMICAL AND NUMERICAL MODELING TECHNIQUES (a case study of Lahore aquifer)


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 25000
    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 10s,
    100s and even 1000s 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 GroundwaterBefore
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
? D ()
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

17
(No Transcript)
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 1960 _at_ 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. 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

51
(No Transcript)
52
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

53
(No Transcript)
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
1960 - beginning of pumping
1910 - Pre-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
63
(No Transcript)
64
Calculated Water Table Contours in 1998
65
(No Transcript)
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
70
(No Transcript)
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
About PowerShow.com