Chapter One

INTRODUCTION

1.1 Importance of the Study

With the increase of the population, the demand of water is

increasing throughout the world. Ground water is the reliable

source of water supply for any climate condition of the any

region. While, surface water is generally easy and economical,

its availability is uncertain with season. Thus, the effective

management of ground water system is essential for a region to

meet the increasing demand of water supply. Ground water provides

clear, safe water at almost constant temperature and is preferred

to compare to surface water for domestic water supply. As an

assured supply of water, it can be obtained from the underground

source even in the desert area if the system is properly designed

and maintained.

Narayanganj city lies between latitudes 23°37′N 90°30′E and

covers an area of about 759.57 km2 having the altitude of 6.5 to

9m above mean sea level. Water supply in Narayanganj organized

since 100 years ago (Chowdhury and Faruqui, 1991) where

systematic groundwater development started since 1949 (Ahmed et

al., 1998). Considering the total population over 14.543 million

(Bangladesh Bureau of Statics, 2011), presently more than 2.1Mm3

(DWASA, 2011) of water is required every day to fulfill the

1

municipal demand in Narayanganj city. Groundwater is the first

choice for the city dwellers as it is superior in quality and

easy to develop. Unchecked surface water pollution has also

prompted people to depend on groundwater that leads rapid

expansion of tube-well numbers. Narayanganj is dependent mainly

on groundwater resources from fluvio-deltaic Pliocene DupiTila

aquifer that provides about 82% of total water supply (DWASA,

2006). Amongst the demand about 2.1Mm3 is withdrawn by about more

than 500 DWASA (Dhaka Water Supply and Sewerage Authority) tube-

wells with 2500km long pipeline network, where system loss is

assumed more than 25% (DWASA, 1999). It is estimated that the

volume extracted by more than 900 private deep tube-wells may be

more than 50% of the DWASA figure (DWASA, 1999). Compare to the

over exploitation of groundwater, the renewable recharge to

aquifer is very negligible though the average annual rainfall in

the city area is about 2000mm. The rechargeable surface area is

decreasing day by day due to construction ofbuildings, roads and

concrete pavements i.e. unplanned urbanization. Natural water

recharge to aquifer cannot keep pace with the water withdrawal

since more than three decades, causing declination ofwater table.

The average annual rate of declination in different parts of

Narayanganj city was 0.17 to 0.6m from 1970 to 1980, 0.15 to

0.69m from 1980 to 1990, 0.56 to 1.3m from 1990 to 2000 and 1.24

to maximum of 2.2m inChasara area since 2000. The rivers

Buriganga and Meghnasurround the city to the south and west and

Lakhya and Balu to the east. Differences of the river water and

2

groundwater levels support the scope of horizontal inflow but the

siltation of river beds are not favorable for the inflow. Hence

the contribution to the aquifer from the adjoining rivers is

negligible.

Figure 1.1 Location Map of the Study Area, Narayanganj (Source:BWDB)

1.2 Factors of ground water level depletion

3

CHASARA

FATULLA

PAGLA

Ground water of any area mainly depends on the geology,

hydrologic parameters, soil properties, recharge, discharge and

hydraulic characteristics of the aquifer. The main factor of

ground water depletion is the abstraction of the water and it

depends on the population, irrigation, rainfall, river water and

surface water depth.

Figure 1.2 Flow chart of causes of ground water level depletion

4

Our study of water level is related to three factors, such as

population, irrigation and abstraction of water. These three

factors are inter-related among each other. The relation of these

factors is mentioned in the above flow chart. Later on the trends

of population increase, increase in irrigation area and equipment

are described. And also the trend of the withdrawal of ground

water is mentioned

1.3 Trend Analysis for Irrigation

To meet the demand of food and drinking water of increasing

population the dependence on ground water is obligatory. In dry

season hence the scarcity of surface water the farmer need to

irrigate the field by ground water in Narayanganj.

Proportion of Demanded Water For Irrigation in Narayanganj

Ground ...Ground Water75%

Surface Water25%

Figure 1.3 Use of water for irrigation (Source: WorldUrbanization)

5

This graph shows that Figure 1.3, 25% of surface water and 75% of

ground water generally are use for Irrigation purpose but

increasing the irrigated area and decreasing the surface water in

river and canal, this reason, to be sure, increase the use of

ground water in every year. After that the remaining portion of

irrigated area in Narayanganj are fully depended on ground water,

as a result the ground water level depletes in every year.

1.3.1 Trends in Irrigated Area by Different Irrigation Technology

from 1982/83 to 2009/10

The figure shown below represents that the use of different

irrigation technology. It shows the use of traditional technology

is decreasing since 1999 and now the area under traditional

irrigation is very low. The use of DTW and STW is increasing very

fast. After few years the STW will not work. So the number of DTW

will take place of STW.

1.4 Declining Trend of Groundwater Level

The recharge to the upper (1st) aquifer occurs mainly by the

horizontal inflow from the surrounding areas and a portion from

the vertical percolation of rain and flood water. Under the

present conditions, the peripheral rivers act as sources of

recharge where the DupiTila sands are exposed along the riverbeds

(Ahmed et al, 1998). The maximum depth to water table in the

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central part of the city i.e. Chasara and Fatulla areas, observed

from BWDB pyrometers, is about 67 to 57m below ground surface

that is about 55m at and 20 to 34m at Pagla areas close to the

river periphery. This continuous decline of water table with

little or even no fluctuation is typical of overexploited

aquifers. In the neighboring areas of the city, seasonal

fluctuation of water table is very distinct that regains static

water level in monsoon .The cone shaped depression observed from

groundwater contour map creates an Opportunity of horizontal flow

from surrounding areas.

Figure 1.4 Groundwater Levels Contour Map (2007) Showing Cone ofDepression towards the Central Part of the Dhaka and Narayanganj

City (Source: Zahid et al, 2007).

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Degradation of groundwater quality due to overexploitation can

also take place. Discharge of solid wastes and liquid effluent

without proper treatment from industrial activities is a big

threat to groundwater environment of Narayanganj city. Use of

large amounts of salt, dissolved lime, and acids in different

stages of the tanning process leads to an effluent with very high

concentrations of Cl, SO4 and heavy metals, e.g. Cr, Pb, S, Zn,

etc. Groundwater flow gradient towards the central part may allow

polluted surface water from the peripheral rivers to the aquifer.

Study (Zahid et al, 2009) shows that ionic concentrations are

acceptable in both the upper and deep aquifers but Mn and Fe

level exceeds WHO (1993) and Bangladesh (DOE, 1991) limits in few

samples. However, concentrations of some ions, e.g. Na, Mg, NH4,

Cl, SO4 and Ca as well as trace elements e.g. Cr, Cu, Pb, Al, S

were observed higher than the background concentrations.

Restricted groundwater circulation favors mineralization and

increases the total dissolved solids (Ahmed et. al., 1998).

Concentration of Fe, Mn and Cr in shallow water (<30m) were found

above the allowable limit of DoE and WHO (Saha, 2001). The deep

groundwater has not yet been influenced significantly by

effluent. The very deep water table and aquitard in general acts

as the purification pathway of the percolating water and is

likely to be favorable for groundwater environment.

1.5 Objective

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To study the yearly variation of ground water table of

Narayanganj City.

To estimate the yearly variation rate of increased pavement

area in Narayanganj City.

1.6 Scope of the StudyIn order to achieve the above objectives, the scope has been set

as below:

Review of previous studies.

An extensive literature review has done through relevant books,

journals, pervious thesis papers etc.

Depletion of ground water level for the study Area:

Graphical and mapping representation of ground water level in

study area of Narayanganj city to understand the variation

condition of ground water table level.

Compares of ground water level and variation depth along with

Narayanganj city and Bangladesh Compares of ground water level

situation of some different categories like divisional

compares and Dhaka to other area.

1.7 Outline of the StudyThe whole activities of our study are organized in a

chronological order which is a great assistance to the reader to

understand without showing any difficulties. In addition,

references of publications have also been presented.

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.

Chapter Two

LITERATURE REVIEW

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2.1 Ground Water

Groundwater is water that exists in the soil pore spaces and

fractures in rock and sediment beneath the Earth's surface. A

unit of rock or an unconsolidated deposit is called an aquifer

when it can yield a usable quantity of water. The depth at which

soil pore spaces or fractures and voids in rock become completely

saturated with water is called the water table.

Groundwater is recharged form, and eventually flows to, the

surface naturally; natural discharge often occurs at springs and

seeps, and can form oasis or wetlands. Groundwater is also often

withdrawn for agricultural, municipal and industrial use by

constructing and operating extraction wells.

Groundwater makes up about 1% of the water on Earth (most

water is in oceans).

But, groundwater makes up about 35 times the amount of water

in lakes and streams.

Groundwater occurs everywhere beneath the Earth's surface, but is

usually restricted to depths less that about 750 meters.

The volume of groundwater is a equivalent to a 55 meter

thick layer spread out over the entire surface of the Earth.

The surface below which all rocks are saturated with

groundwater is the water table

Rechargeable water must filter down through the vadose zone to

reach the zone of saturation, where groundwater flow occurs. The

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rate of infiltration is a function of soil type, rock type,

antecedent water, and time.

The vadose zone includes all the material between the Earth’s

surface and the zone of saturation. Near the upper boundary of

the zone of saturation where water pressure equals atmospheric

pressure, is the water table. The capillary fringe is a layer of

variable thickness that directly overlies the water table. Water

is drawn up into this layer by capillary action. The vadose zone

has an important environmental role in groundwater systems. As

with water, surface pollutants must filter through the vadose

zone before entering the zone of saturation.

Figure 2.1Ground water and different zone (Source: EnvironmentCanada)

2.2 The Water Table/Level

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Rain that falls on the surface seeps down through the soil and

into a zone called the zone of aeration or unsaturated zone where

most of the pore spaces are filled with air. As it penetrates

deeper it eventually enters a zone where all pore spaces and

fractures are filled with water.

This zone is called the saturated zone. The surface below which

all openings in the rock are filled with water (the top of the

saturated zone) is called the water table

.

2.3. Aquifers

An aquifer is a large body of permeable material where

groundwater is present in the saturated zone. Good aquifers are

those with high permeability such as poorly cemented sands,

gravels, and sandstones or highly fractured rock. Large aquifers

can be excellent sources of water for human usage such as the

High Plains Aquifer (in sands and gravels) or the Floridian

Aquifer (in porous limestone).

2.3.1 Unconfined Aquifers - the most common type of aquifer,

where the water table is exposed to the Earth's atmosphere

through the zone of aeration. Most of the aquifers depicted in

the drawings so far have been unconfined aquifers.

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Figure 2.2 Aquifer and Wells (Source: Environment Canada)

2.3.2 Confined Aquifers

These are less common, but occur when an aquifer is confined

between layers of impermeable strata. A special kind of confined

aquifer is an artesian system, shown above. Artesian systems are

desirable because they result in free flowing artesian springs

and artesian wells.

2.4 Rainfall

In meteorology, precipitation is any product of the condensation

of atmospheric water vapor that falls under gravity. Rain is

liquid precipitation, as opposed to non-liquid kinds of

precipitation such as snow, hail and sleet. Rain requires the

presence of a thick layer of the atmosphere to have temperatures

above the melting point of water near and above the Earth's

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surface. On Earth, it is the condensation of atmospheric water

vapor into drops of water heavy enough to fall, often making it

to the surface. Two processes, possibly acting together, can lead

to air becoming saturated leading to rainfall: cooling the air or

adding water vapor to the air. Virga is precipitation that begins

falling to the earth but evaporates before reaching the surface;

it is one of the ways air can become saturated. Precipitation

forms via collision with other rain drops or ice crystals within

a cloud. Rain drops range in size from oblate, pancake-like

shapes for larger drops, to small spheres for smaller drops.

Precipitation is a major component of the water cycle, and is

responsible for depositing the fresh water on the planet.

Approximately 505,000 cubic kilometers (121,000 cu mi) of

waterfalls as precipitation each year; 398,000 cubic kilometers

(95,000 cu mi) of it over the oceans. Given the Earth's surface

area, that means the globally averaged annual precipitation is

990 millimeters (39 in). Rain is the primary source of freshwater

for most areas of the world, providing suitable conditions for

diverse ecosystems, as well as water for hydroelectric power

plants and crop irrigation. Rainfall is measured through the use

of rain gauges. Rainfall amounts are estimated actively by

weather radar and passively by weather satellites.

2.4.1 Relation between Rainfall and Groundwater level

Groundwater is the part of precipitation that infiltrates deep

into the ground. It flows downward by gravity until it reaches a

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hard layer of rock that is impermeable to water. Just above this

impermeable rock layer is the saturation zone, where all water

that has soaked deep underground is stored. The pore spaces (tiny

spaces or fractures between pieces of rock or soil) in this zone

are completely filled with water.

Figure 2.3Water cycle (Source: Environment Canada)As a general rule, in natural watersheds, approximately:

60% of the precipitation evaporates or transmigrates back into

the atmosphere,

30% infiltrates the soil and

10% runs off into surface water bodies

.The water balance for the watershed (or sub watershed)

determines the amount of water available for water ecosystem

functioning and the amount available for human uses. It is

necessary to understand this "water balance" in order to maintain

the resource and its environmental and human connections in the

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watershed. The understanding of the water cycle on a watershed

basis is important for developing watershed management policies

and procedures

2.5 Tube wells and Irrigation

A tube well is a type of water well in which a long 100–200 mm (5

to 8 inch) wide stainless steel tube or pipe is bored into the

underground aquifer. The lower end is fitted with a strainer, and

a pump at the top lifts water for irrigation and drinking

purpose. The required depth of the well depends on the depth of

the water table. Shallow and deep tube wells are used for supply

clear and safe water. To provide full clear and safe water supply

in a country install shallow and deep tube wells, and that result

high amount of ground water withdrawal. In every city the

withdrawal amount of ground water is so much than rural area,

because city dweller is fully depended in ground water for

domestic purpose.

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Figure 2.4 Irrigation process by ground water and other

phenomenon (Source: Environment Canada).

Irrigation may be defined as the science of artificial

application of water to the land or soil. It is used to assist in

the growing of agricultural crops, maintenance of landscapes, and

re Vegetation of disturbed soils in dry areas and during periods

of inadequate rainfall.

Additionally, irrigation also has a few other uses in crop

production, which include protecting plants against frost,

suppressing weed growing in grain fields and helping in

preventing soil consolidation. During irrigation some water back

to the ground water table and some are evaporated, but the amount

of back water is so less than amount of withdrawal. The

widespread and often indiscriminate use of this pumping device

has led to depletion of the water table, as ground water is being

extracted much faster than it can be replenished by rainfall.

"Every year, farmers bring another million wells into service,

most of them outside the control of the state irrigation

authorities.

2.6 Overview of Bangladesh

2.6.1 Location

Bangladesh lies between 20"34' and 26"38' North Latitude and

88"01' and 92"41' East Longitude with a total landmass of 1,

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47,570 square kilometers. Bangladesh is surrounded by India on

the west, north and northeast, Myanmar on the southeast, and the

Bay of Bengal on the south. Bangladesh acts as a bridge between

South Asia and Southeast Asia.

2.6.2 Topography of Study area

Bangladesh is the largest deltaic region in the world with most

of its parts, at low elevations.

It is a reverie country crises-crossed by innumerable rivers,

rivulets and their tributaries. It is divided into five physical

regions- the Ganges Delta proper to the southwest, the Para delta

to the northeast, and the southeast undulating Chittagong region.

The Ganges Delta is geologically the most recent compared to

other regions. Mangrove forests thrive in the active lower delta,

which is flooded by fresh tidal waters. The soil base is new

alluvium. The Sundarban, a former site for tiger hunting, is the

largest mangrove forest (around 6000square kilometer) in the

world. The Paradelta, like the delta proper, is a plain, but its

elevations are higher, at 100 to 300 feet (30 to 90 meters) above

sea level. Its soils are varied, silt and sandy clays, and old

alluvium. It lies between the Ganges and the Jumana rivers. The

East Central plains, with the Meghna River almost at its center

consist of plains and active floodplains in which the main

rivers, including the Brahmaputra, have altered their channels in

the past. At the center of this plain lies, Madhupur forest. To

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the northeast is the Meghna depression, part of which is only 10

feet (3 meters) above sea level.

2.6.3 Climate

Bangladesh has a tropical monsoon climate with heavy summer rain

and high summer temperatures. Winters are dry and cool. South and

southwest winds dominate from mid-April to mid-October and bring

enormous amounts of moisture from the Indian Ocean and the Bay of

Bengal: 95 percent of the total rainfall, which averages about

eighty inches (2,040 millimeters), occurs during that period. The

temperatures range from an average of about 68 F (18C) in January

to about 86 F (30°C) in April.

2.6.4 People

Bangladesh is one of the world's mostly densely populated

countries in the world. Its population is 128.1 million people

with an average density of about 755 people per square kilometer.

About 85% of the population lives in rural areas. Bangladesh is a

model of religious harmony and tolerance. Different religious

communities and groups live in peace and the minorities are well

represented in all tiers of society as well as in the government

machinery. Islam is the predominant religion with over eighty

percent of the people adhering to it. Hindus comprise about ten

20

percent of the population. The rest are Buddhists, Christians and

animists

.

2.6.5 Geology

The country occupies major part of the BENGAL DELTA, one of the

largest in the world. The

GANGES-BRAHMAPUTRA Delta basin or the BENGAL BASIN includes part

of the Indian state of West Bengal in the west and Tripura in the

east. GEOLOGICAL EVOLUTION of Bangladesh is basically related to

the uplift of the Himalayan Mountains and outbuilding of deltaic

landmass by major RIVER systems originating in the uplifted

HIMALAYAS. This geology is mostly characterized by the rapid

SUBSIDENCE and filling of a basin in which a huge thickness of

deltaic sediments were deposited as a mega-delta out built and

progressed towards the south. The DELTA building is still

continuing into the present BAY OF BENGAL and a broad fluvial

front of the Ganges-Brahmaputra-Meghna river system gradually

follows it

from behind. Only the eastern part of Bangladesh has been

uplifted into hilly landform incorporating itself into the

frontal belt of the INDO-BURMAN RANGE lying to the east.

Stratigraphic subdivision of the rock sequences in Bangladesh

follows the broad tectonic divisions. In the Precambrian

platform, a thin to limited sedimentary sequence of Permian to

Recent age lies on a CRYSTALLINE BASEMENT conforming to the

relative tectonic stability of the area.21

Stratigraphy of Precambrian platform in northwestern Bangladesh,

Precambrian igneous and metamorphic rocks form the base of all

sedimentary rock units. The Precambrian basement is composed

mainly of granite, granodiorite and gneiss. The basement occurs

at a shallowest depth of 130m below the surface in the Rangpur

area and dips towards southeast with increasing sedimentary cover

ranging in age from Permian to Recent. Permian the oldest

sedimentary unit in Bangladesh is the Gondwana group of Permian

age, resting uncomfortably on the Precambrian crystalline

basement. The Gondwana group is composed of hard sandstone with

some coal and shale layers. The Group is about 1000m thick and is

found in fault bounded grabbed basins.Jurassic-Cretaceous Above

the Gondwana group of sediments lies a sequence of volcanic

basaltic rock layers of Jurassic age called Rajmahal Trap

formation, named after the RAJMAHAL HILLS in adjacent India where

the unit is exposed on the surface. The unit is about 500m thick

and found in the drill holes in the Rajshahi-

Bogra area. The Rajmahal trap is overlain by the ShibganjTrapwash

formation, a relatively thin cover of the weathered product of

volcanic rocks consisting of red ferruginous sandstone and

mudstone. It is Cretaceous in age.

Early Tertiary The next upward sequence of rocks is named the

Jaintia groups, which belongs to the Palaeocene and Eocene age

and were formed under marine conditions. The Jaintia group is

divided into three units, from bottom upward, the Tura formation,22

Sylhet Limestone formation and Kopili Shale. The Tura formation

is composed mainly of whitish sandstone with occasional thin coal

beds near the top. Overlying these lays the Sylhet Limestone

formation, nummuliticfossiliferous limestone units of middle

Eocene age with average thickness of 250m. The Sylhet Limestone

formation is the most extensively developed unit in the

subsurface of northwestern Bangladesh and is a marker horizon in

the seismic section.

The overlying Kopili formation is composed of dark grey to black

fossiliferous shale with a few limestone beds. The unit has a

thickness of 40 to 90m and marks the end of open marine

conditions of deposition.

The Surma group is overlain by the SAND dominating Tipam group of

the Pliocene- Pleistocene age. The Group is subdivided, from

bottom upward, into the Tipam Sandstone formation, Girujan Clay

formation and DupiTila formation. The Tipam Sandstone formation,

about 1,200m to 2,500m thick, is dominantly composed of medium

grained sandstone frequently cross bedded, with little shale and

this indicates deposition under a river environment. The

overlying Girujan Clay formation is a shale unit with a thickness

of 100 to 1,000m and was formed under a lake environment. The

DupiTila Sandstone formation is 2,000 to 3,000m thick and is

composed of medium to coarse loosely compacted cross-bedded

sandstone, occasionally pebbly and this indicates deposition in a

river environment. The above is covered with about 100m of sandy,

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silty and clayey sediment of Bengal Alluvium of Recent age.The

stratigraphic subdivision and nomenclature follow the one

established by the geologist P Evans in 1932 for the rock

sequence in the adjacent Indian State of Assam to the northeast.

Given the complexities of faces and their interrelations in a

deltaic to fluvial regime, the present correlation of Evan's

units over the entire basin in Bangladesh appears to be too

generalized. Many geologists believe, for example, that the litho

logical criteria for the Bhuban and Bokabil formations are not so

explicit that these units can be extended over the entire basin

and their uses should be restricted if not abandoned. The concept

of Diachronism should be incorporated for the deltaic upper

Tertiary basin sedimentary units, which are not isochronous but

do cut time lines and are therefore diachronic in nature. A

stratigraphic committee of Bangladesh has been formed to

formulate a revised classification in the light of the above.

2.7 Groundwater Aquifers

Generally, four major physiographic units exist at the surface of

Bangladesh (Figure 2.2).

These are (a) Tertiary sediments in the northern and eastern

hills; (b) Pleistocene Terraces in the Madhupur and Barind

Tracts; (c) Recent (Holocene) floodplains of the Ganges, the

Brahmaputra and the Meghna rivers and (d) the Delta covering the

24

rest of the country. Most of the present land surface of the

country covered by the Holocene flood plains deposited by the GBM

river systems.

About 6000 year ago sea level was much lower and the major rivers

dissected deep channels adjacent to the Madhupur and Barind Tract

areas. Deltaic floodplains with some Pleistocene terraces

constitute the major part of the Basin. Basinal sediments consist

primarily of unconsolidated alluvial and deltaic deposits except

the complex geology area of prequaternary sediments that cover

the northeastern and southeastern hilly areas of the country.

Together with the tertiary sedimentary sequences the maximum

thickness of the deposit is more than 20km.

The tropical monsoon climate together with favorable geological

and hydro- geologic conditions indicates high potential storage

of groundwater in the country. The unconsolidated near surface

Pleistocene to Recent fluvial and estuarine sediments underlying

most of Bangladesh generally forms prolific aquifers. Thicksemi-

consolidated to unconsolidated fluvio-deltaic sediments ofMiocene

age to the recent form many aquifers. But except the DupiTila

sandstone formation of the Plio-Pleistocene age, others are too

deep to consider for groundwater extraction except in the hilly

region (18 percent of Bangladesh). Most of the groundwater

withdrawn for domestic or agricultural purposes in the Barind and

Madhupur uplands areas is from the DupiTila aquifersThe

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floodplains of the major rivers and the active/inactive delta

plain of the GBM Delta Complex occupy 82 percent of the country.

From the available subsurface geological information it appears

that most of the good aquifers occur between 30 to 130 m depth.

These sediments are cyclic deposits of mostly medium to fine

sand, silt and clay. The individual layers cannot be traced for

long distances, horizontally orvertically. On a regional basis,

three aquifers have been identified and named by BWDB-UNDP

(1982). These are:

Figure 2.5 Aquifer systems in lower delta floodplain, Sreerampur,

Chandpur( Source: BWD,2004)

2.7.1 The Upper (Shallow) or the Composite Aquifer

From Figure 2.5, below the surface clay and silt unit, less than

few to several hundred meters thick very fine to fine sand, in

places inter bedded or mixed with medium sand of very thin layers

are commonly encountered. The thickness of this zone ranges from

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a few meters in the northwest to maximum of 60m in the south.

Over most of the country it represents the upper water bearing

zone.

2.7.2 The Main Aquifer

From ground surface the main water-bearing zone occurs at depths

ranging from less than 5m in the northwest to more than 75m in

the south and most of the country. It is either semi-confined or

leaky or consists of stratified interconnected, unconfined water

bearing formations. This aquifer comprises medium and coarse-

grained sandy sediments in places inter-bedded with gravel. These

sediments occur to depths of about 140m below ground surface.

Presently, groundwater is drawn predominantly from these strata.

2.7.3 The Deeper Aquifer

The deeper water-bearing unit is separated from the overlying

main aquifer by one or more clay layers of varied thickness. Deep

aquifers generally include those aquifers whose waters have no

access vertically upward and downward but flow very slowly along

the dips and slopes of the aquifers. The depths of the deep

aquifers in Bangladesh containing usable water range from 190 to

960 m on the Dinajpur platform and 250 to 1500 m in the basin and

mainly include the sediments of the Gondwana, Jaintia, Surma and

27

Tipam groups and parts of the DupiTila Sandstone Formation (Khan,

1991). This water bearing-zone comprises medium to coarse sand in

places inter-bedded with fine sand, silt and clay. At present the

water-bearing formation deeper than 150-200 m are being exploited

on limited basis in the coastal zone to cater to the need of

municipal water supply and in the rural areas for drinking

purpose. Large scale extraction has not been encouraged due to

possibility of seawater intrusion or leakage of saline or arsenic

contaminated water from the upper aquifer. Considering age,

except the hilly regions, aquifers can be divided into following

two categories for floodplains, delta and terrace areas.

2.7.4 The Holocene Aquifers

Other than the terrace areas, the remaining part of the Bengal

Basin consists predominantly of Holocene alluvial and deltaic

sediments. Below Figure 2.6 The age of Holocene aquifers range

from 100 to more than 3,000 years (Aggarwal et al., 2000). In the

land above tidal inundation, these deposits are composed

primarily of silt and sand of appreciable thickness extending to

depth of more than hundred meters. In the lower delta, they are

principally silt, clay and peat. These sediments contain high

water content and are generally loosely compacted and usually

grey in color. Holocene and Pleistocene alluvium form the

principal aquifers in the country. The Recent alluvium deposits

are of varying characteristics classified from piedmont deposits28

near the foot of the mountains to inter-stream alluvium including

deposits in the interior, merging with swamp and deltaic deposits

approaching the southern shoreline. Stratified deposits of sand,

silt and clay constitute the subsurface formations. The character

of the deposits varies remarkably vertically. Coarse and medium

sand with gravel are found mainly in the northern border areas of

greater Rangpur and Dinajpur districts. The sediments of coastal

areas and northwestern part of Rajshahi district are

predominantly silt, clay and fine sand with occasional coarse

sand. The deeper aquifer consisting of fine to medium sand

vertically extends 180 to more than 250 m depths from the surface

and is separated by 10 to 50 m thick clay layer from the

overlying aquifer (Figure 6) and is promising for groundwater

exploration in Chittagong coastal plain aquifer (Zahid et al.,

2004).Rainwater is the principal source of groundwater recharge

in Bangladesh. Floodwater, which overflows the river and stream

banks, also infiltrates into the groundwater. Water from

permanent water bodies (Rivers, canals, wetlands, ponds,

irrigated fields etc.) that lie above the water table also

percolates to the groundwater. In the Pleistocene terraces, the

recharge occurs through the incised antecedent drainage channels

that cut through near-surface clays into the underlying sands.

29

Figure 2.6 Rangadia coastal plain aquifer, Chittagong (Source:Zahid et al, 2004)

The greatest scope of recharge is within the coarse grained

sediments and the least is within the fine-grained sediments like

clay. The regional hydraulic gradient is low, reflecting the low

topographic gradient. The groundwater flows generally from north

to south. Most of the flow probably takes place through the in-

filled incised channels under the major rivers.

2.8 River and Lakes

Rivers are the most important geographical features in

Bangladesh, and it is the rivers that created the vast alluvial

delta. It's been known that the out flow of water from Bangladesh

is the third highest in the world, after the Amazon and the Congo

systems. The Padma, Jamuna and the lower Meghna are the widest30

rivers, with the latter expanding to around eight kilometers

across in the wet season, and even more during thefloods.

Some rivers are known by different names in various portions of

their course. The Ganges (Ganga), for example, is known as the

Padma below the point where it is joined by the Jamuna River, the

name given to the lowermost portion of the main channel of the

Brahmaputra. The combined stream is then called the Meghna below

its confluence with a much smaller tributary of the same name. In

the dry season the numerous deltaic distributaries that lace the

terrain may be several kilometers wide as they near the Bay of

Bengal, whereas at the height of the summer monsoon season they

coalesce into an extremely broad expanse of silt-laden water. In

much of the delta, therefore, homes must be constructed on

earthen platforms or embankments high enough to remain above the

level of all but the highest floods. In non-monsoon months the

exposed ground is pocked with water-filled borrow pits, or tanks,

from which the mud for the embankments was excavated. Throughout

the country there are bils, haors and lakes that meet the need of

drinking, bathing and irrigating water.

2.9 Flooding

The South Asian country of Bangladesh is prone to the natural

disaster of flooding due to being situated on the Ganges Delta

and the many tributaries flowing into the Bay of Bengal.

31

Flooding normally occurs during the monsoon season from June to

September during the monsoon. The convectional rainfall of the

monsoon is added to by relief rainfall caused by the Himalayas.

Melt water from the Himalayas is also a significant input and

flood every year. Each year in Bangladesh about 26,000 km2,

(around 18%) of the country is flooded, killing over 5,000 people

and destroying 7 million homes. During severe floods the affected

area may exceed 75% of the country, as was seen in 1998. This

volume is 95% of the total annual inflow. By comparison, only

about 187,000 million m3, of stream flow is generated by rainfall

inside the country during the same period. The floods have caused

devastation in Bangladesh throughout history, especially during

the years 1966, 1987, 1998 and 1988. The 2007 South Asian floods

also affected a large portion of Bangladesh. Small scale flooding

in Bangladesh is required to sustain the agricultural industry,

as sediment deposited by floodwaters fertilizes fields. The water

is required to grow rice, so natural flooding replaces the

requirement of artificial irrigation, which is time consuming and

costly to build.

2.10 Drainage System

The rivers of Bangladesh mark both the physiographic of the

nation and the life of the people.

About 700 in number, these rivers generally flow south. The

larger rivers serve as the main source of water for cultivation

and as the principal arteries of commercial transportation.

32

Rivers also provide fish, an important source of protein.

Flooding of the rivers during the monsoon season causes enormous

hardship and hinders development, but fresh deposits of rich silt

replenish the fertile but overworked soil. The rivers also drain

excess monsoon rainfall into the Bay of Bengal. Thus, the great

river system is at the same time the country's principal resource

and its greatest hazard

The profusion of rivers can be divided into five major networks.

The Jamuna-Brahmaputra is 292 kilometers long and extends from

northern Bangladesh to its confluence with the Padma. Originating

as the Yarlung Zangbo Jiang in China's Xizang Autonomous Region

(Tibet) and flowing through India's state of Arunachal Pradesh,

where it becomes known as the Brahmaputra it receives waters from

five major tributaries that total some 740 kilometers in length.

At thepoint where the Brahmaputra meets the Tista River in

Bangladesh, it becomes known as the Jamuna. The Jamuna is

notorious for its shifting sub-channels and for the formation of

fertile silt islands (chars). No permanent settlements can exist

along its banks

The second system is the Padma-Ganges, which is divided into two

sections: a 258-kilometer segment, the Ganges, which extends from

the western border with India to its confluence with the Jamuna

some 72 kilometers west of Dhaka, and a 126-kilometer segment,

the Padma, which runs from the Ganges-Jamuna confluence to where

it joins the Meghna River at Chandpur. The Padma-Ganges is the

33

central part of a deltaic river system with hundreds of rivers

and streams some 2,100 kilometers in length flowing generally

east or west into the Padma.

The third network is the Surma-Meghna system, which courses from

the northeastern border with India to Chandpur, where it joins

the Padma. The Surma-Meghna, at 669 kilometers by itself the

longest river in Bangladesh, is formed by the union of six lesser

rivers. Below the city of Kalipur it is known as the Meghna. When

the Padma and Meghna join together, they form the fourth river

system the Padma-Meghnawhich flows 145 kilometers to the Bay of

Bengal.

This mighty network of four river systems flowing through the

Bangladesh Plain drains an area of some 1.5 million square

kilometers. The numerous channels of the Padma-Meghna, its

distributaries, and smaller parallel rivers that flow into the

Bay of Bengal are referred to as the Mouths of the Ganges. Like

the Jamuna, the Padma-Meghna and other estuaries on the Bay of

Bengal are also known for their many chars.

A fifth river system, unconnected to the other four, is the

Karnaphuli. Flowing through the region of Chittagong and the

Chittagong Hills, it cuts across the hills and runs rapidly

downhill to the west and southwest and then to the sea. The Feni,

Karnaphuli, Sangu, and Matamuhari--an aggregate of some 420

kilometers--are the main rivers in the region. The port of

Chittagong is situated on the banks of the Karnaphuli. The

34

Karnaphuli Reservoir and Karnaphuli Dam are located in this area.

The dam impounds the Karnaphuli River's waters in the reservoir

for the generation of hydroelectric power.

The five mighty river systems flowing through Bangladesh drain an

area of some 1.5 million sq km. During the wet season the rivers

of Bangladesh flow to their maximum level, at about 140,000

cumec, and during the dry period, the flow diminishes to 7,000

cumsec. All the estuaries on the Bay of Bengal are known for

their many estuarine islands

2.11 A Soil Salinity Control

Soil salinity control relates to controlling the problem of soil

salinity and reclaiming Stalinized agricultural land.

The aim of soil salinity control is to prevent soil degradation

by salivation and reclaim already salty (saline) soils. Soil

reclamation is also called soil improvement, rehabilitation,

remediation, recuperation, or amelioration.

The primary man-made cause of Stalinization is irrigation. River

water or groundwater used in irrigation contains salts, which

remain behind in the soil after the water has evaporated.

The primary method of controlling soil salinity is to permit 10-

20% of the irrigation water to leach the soil, be drained and

discharged through an appropriate drainage system. The salt

concentration of the drainage water is normally 5 to 10 times

35

higher than that of the irrigation water, thus salt export

matches salt import and it will not accumulate.

2.11.1 About the Regional Assessment

Freshwater aquifers along the Atlantic coast of the United States

are bounded at their seaward margins by saltwater. Ground-water

withdrawals from these aquifers can cause lateral and vertical

intrusion of surrounding saltwater, and incidences of saltwater

intrusion have been documented throughout the eastern seaboard.

Withdrawals also can change the patterns of ground-water flow and

discharge to coastal ecosystems, which may alter the nutrient

budgets and salinity of coastal waterways and wetlands. Projected

future growth in population along the coastal areas of the United

States will likely increase stresses on coastal aquifers and

ecosystems in the next century. As part of the Ground-Water

Resources Program, the USGS is conducting an assessment of

freshwater-saltwater interactions and issues along the Atlantic

coast, focusing on saltwater intrusion into freshwater aquifers

and ground-water discharge into coastal ecosystems.

2.12 Previous Study on Ground Water level Condition ofBangladesh

1) A.A Kainan and C.E. Hafiz (March 2006) they study on

“Livelihood systems assessment, vulnerable groups profiling and

livelihood adaptation to climate hazard and long term climate

change in drought prone areas of NW Bangladesh”. Some part of

36

this study was described ground water level situation and

development of the Naogaon and chapai-Nawabgonj districts.

They analyzed groundwater level data to assess the groundwater

situation during different months of the year. Data has been

analyzed from 1960 to 2000. The depletion of groundwater table in

the study area shows a remarkable draw down from early eighties.

The groundwater table hydrograph was drawn from a selected number

of wells in the study area. The mean ground water table in

Nachole area shows that it was within 3 to 10 meter from the

surface during 1980’s. Groundwater is depleted more than 8 meters

during the last ten years and recent trend shows the rate of

depletion is much more prominent. During the dry season the

ground water table depleted down to 14–20m in Nachole and

Gomastapurupazila, whereas in Porsha and Sapaharupazila, the

ground water table was within 6–10m.

37

Figure 2.7 Groundwater development in the selected upazillas(Source: Zahid et al., 2004)

Irrigation development in the selected upazilas show that the

both surface and groundwater irrigation practices increased

appreciably from 1980’s to onward. The temporal analysis of

National Minor Irrigation Census (NMIC) irrigation census data

depicts that the irrigation coverage is increased at large scale

from 1985. This is due to the initiation of extensive groundwater

development by BMDA in the region.Shows the trend of groundwater

development of the study areas. Irrigation practices in the

Porshaupazila are highest and in Nacholeupazila is the lowest.

Depletion of groundwater table in Porshaupazila is within the

suction limit of STW/DSSTW whereas in the Nacholeupazila, the

groundwater depletion is more than 20 meters from the ground,

which is beyond DSSTW suction limits.

38

2) S. Sarmin (December 2009) study on “Hydro-geochemistry of the

Lower Dupitila aquifer in Narayanganj city, Bangladesh”. In this

study she was showing the ground water level depletion

inNarayanganj city .The main part of the depletion is shown

below.

Groundwater level beneath the Narayanganj city has started to

decline since two decades ago when rapid urbanization in city

resulted into higher water demand. In the period of 1965-1980,

water level decline to about 3-9m, being maximum at Chasara and

minimum at area. At that time the rate of decline was 1.79

m/year. According to the Water and Sewerage Authority (WASA), the

groundwater table was at 11.3 m below the surface in the 1970s

and at 20 m in the 1980s. 26.6 m in 1996, 28.15 m in 1997, 30.5 m

in1998, 31.86 m in 1999, 34.18 m in 2000, 37.78 m in 2001, 42 m

in 2002. Groundwater level in Narayanganj has dropped to 54.3 m

below the surface putting the sprawling metropolis at risk. A

recent study by the Bangladesh Agricultural Development

Corporation (BADC) has revealed that groundwater table of

Narayanganj has gone down by 35m in the past 11 years. According

to this study groundwater level inNarayanganj was 35.4 in 2003,

38.6 in 2004, 53.2 in 2005, 59.72 in 2006 and 55.4 in 2007.

Hydro geochemistry of the Lower DupiTila Aquifer in Narayanganj

City, Bangladesh

39

Figure 2.8 Declining trend of Water Table from 1969 up to 2007.(Source: Zahid et al., 2004)

Groundwater hydrograph of Upper DupiTila aquifer system

demonstrates a steady down ward slope (At present the depletion

rate is about 2.5-3.5 m/year. (DWASA & IWM, 2008).Lower DupiTila

(deeper) Aquifer haspiezometric level at 18.08 m from ground

surface (Hossain et al., 2007)

2.13 Groundwater Status of Narayanganj City

High population along with increase rate of urbanization has made

Narayangonj city. The population of Narayanganj in 2012 was 2.2

million and projected population is 22.04 millions in 2020 and

Dhaka will acquire 4th position among the fastest growing

megacities assuming annual growth rate 3.79% (United Nations,

1999). Systematic groundwater development started in Dhaka city

in 1949 and available records show that groundwater abstraction

in the city has increased more than several hundred times from

the 1960 to date. Groundwater abstraction was 40.3 MCM in 1964

and it is increased up to 699 MCM in 2004. By the 1960s,

40

groundwater became the principal source for public supply in

Dhaka. In 1963 DWASA was established (Haq, 2006) and by 1966

groundwater abstraction had reached 30 Mm3 per year, with surface

water providing less than 10 Mm3 per year.

Figure 2.9Area Maps

of Narayanganj and Dhaka City (Source: DWASA, 2008).41

The independence of Bangladesh in 1971 stimulated the development

of groundwater (Ahmed et al., 1999). At that time, the city had a

population of less than two million and groundwater abstraction

was less than 50 MCM per year. By 1992, 150 public supply (PS)

boreholes, up to 180 m deep, managed by DWASA and distributed

across the city, were yielding a total of 170 MCM per year. By

1998 this had risen to 190 PS boreholes and 200 private boreholes

abstracting in total 310 MCM (Ahmed et al., 1999), and by late

2000 DWASA was pumping approximately 400 MCM from a total of more

than 330 boreholes (Morris et al., 2003). The increased

population is raising the demand of water and the projected

population and water demand can easily be understood for near and

far future.

As of 2003, DWASA produced 1160 million liters of groundwater per

day through 389 DTWs. The number of private boreholes has also

increased substantially to 970 wells (WASA 2000), and the

quantity of water abstracted through these wells is although

unknown but is likely to be significant. Currently, this

dependence on Groundwater is surprisingly high. About 85.82% of

the present municipal water supply comes from groundwater and

14.2% is from surface water (DWASA, 2008). Presently, the Dhaka

WASA is tapping water between 50-350m of the aquifer materials.

During 2008 DWASA produced 1553 million L of groundwater per day42

through 491 DTW and estimated to increase 4130million L/day in

coming 20 years. From the total production of DWASA i.e.1806

million L/day, only 252.7 million/day is being served by surface

water treatment plant.

Among the present total abstraction,512.26 MCM for domestic water

supply,125.82 MCM for commercial, 27.96 MCM for industrial supply

and 27.96 MCM for community and other supply (Hossain et

al.,2007). The number of deep tube wells increased from 327 in

2001 to 435 in 2005,466 in 2007 and 491 in 2008. Rapid population

growth and so rapid urbanization during the last three decades

has taken place, which creates extra pressure on the land.

43

Figure 2.10 Deep tube wells and water supply pipe network in 10

zones of DWASA and b) the increased built-up area in Dhaka and

Narayanganj City (Source: DWASA, 2008).

Over abstraction is being released from aquifer storage and it is

the mining volume because pumping volume is much higher than

recharge volume and safe yield. It is thought that due to

groundwater depletion from over abstraction around 50% of DTWs in

44

Upper DupiTila Aquifer system will be inoperative and groundwater

production will go down (Carls Bro, 2007). is showing the

position of an abandoned well which was installed in1984 with

housing length 42.6 m and 2 cusec discharge. The new well

(2ndreplacement well) which is still under production, was

installed in 2001 with housing length 91 m and 2 cusec discharge.

There are about 265 abandoned wells like this.

Land subsidence due to groundwater overdraft is one of the most

urgent environmental dilemmas facing the mega cities across the

globe. A recent study shows that land subsidence in Narayanganj

city will be 6.4 cm from 2000 to 2020 (DWASA & IWM, 2008).

Declining ground-water level will greatly increase the risks

during earth quakes. Over abstraction significantly increases the

cost of drilling and pumping of wells and abandonment of many

shallow wells which results in significant loss of saturated

thickness.

45

Figure 2.11 District wise averages Ground Water Level (in Meter)in 2010.

In Barisal, Chittagong, Dhaka, Khulna, Rajshahi and Sylhet

division, average ground water depletion rates are respectively

0.28, 0.46, 0.30, 0.38, and 0.38 ft/year for 1986-2000. And for

that divisions from 2000 to 2010 the average ground water

depletion rate respectively 0.5, 0.5, 0.4, 0.5, 0.5 and 0.4

ft/year.From the ground water level hydrographs in different

divisions, it is found that ground water level is gradually

declining.

Chapter Three

RESEARCH METHODOLOGY

46

3.1 General

Groundwater situation on static water level is an important

parameter for groundwater budgeting, protection of quality

degradation and future project expansion plan. Hydraulic and

distribution also provides valuable information for evaluation of

groundwater availability, flow trends and designing of upper well

casing.

3.2 Data collection sources

In order to study the long term trend of groundwater table variation

in Narayangonj city of Bangladesh, groundwater level data is required.

Mainly ground water table monitoring is carried out routinely by BWDB,

BADC and DPHE. DPHE maintain observation wells at different location

in Bangladesh. All the available data of observation well is collected

from DAWA, BWDB. These data is covered the whole area of Dhaka city.

The population data is collected from BBS and World Bank. Also

required the data of number of tube wells are installation in year,

previous tube wells data is collected from the BADC, DWASA. The data

of ground water withdrawal of Dhaka City is collected from Dhaka WASA.

In these study also required the long-term data of average annual

rainfall data, mainly rainfall is daily monitor by BMD and BWDB. The

required rainfall data is collected from the BWDB and location map

collection Local Government Engineering Department (LGED).

3.3 Ground water survey location

The survey location is various zone of Narayanganj city namely Chasara, Fatulla, and Pagla.

47

Figure 3.1 Location Map Narayanganj (Sources LGED)

3.4 Measurement Ground water levels in wells

• Determine flow directions

• Identify changes in gradients and (or) flow directions (temporal variance)

• Measurements for aquifer testing

48

Pagla

Fatull

Chasara

• Measurements related to ground-water sampling

Figure 3.2 Equipment and methods of manually measuring ground-water levels.

49

Figure 3.3 Pressure transducers and data loggers forautomatically measuring water levels

Figure 3.4 Water level Measuring Tape

3.5 Ground-water data collection system

3.5.1 Steel Tape system

A basic measurement in ground-water studies is that of water

levels in wells. Measurements may be made with several types of

equipment. The choice of equipment depends on several factors

50

including the accuracy or ease of measurement required, water-

quality concerns, type of well (monitoring or water supply), and

pumping activity of well and (or) nearby wells.

For all measurements, a fixed reference point must be established

at the well head. This point usually is the top of the casing or

the access port in water-supply wells. The reference point

typically is surveyed to establish its position above sea level,

to an accuracy of 0.01 ft. To ensure the same reference points

are used for all measurement, a notch or marking is made on the

casing and the location of the point well documented in the site

file. If the well cap is not vented, remove several minutes

before measurement to allow water levels to equilibrate to

atmospheric pressure.

The most accurate measurement (+- 0.01 feet) is obtained with a

chalked steel tape. This method utilizes a graduated tape with a

weight attached to its end. A quality steel tape has limited

elasticity and with sufficient weight hangs vertically in the

well. Older tapes may use a lead weight, but present concerns

about water quality require that the weight be brass or stainless

steel.

The lower 3-4 ft of the tape is coated with carpenter’s chalk,

and the tape is lowered into the water until the lower part of

the tape (about 2 ft) is submerged. By lowering the tape at

intervals of about 2-3 ft the contact of the weight with the

water’s surface can be heard. For wells with deep water levels,

it may be necessary to approximately know the depth to water or

51

to make several measurement attempts to ensure that the tape is

not submerged below its chalked length. The tape is held at the

reference point and the tape position recorded. The depth to the

water level below the reference point is determined by

subtracting the length of wet tape (indicated by wet chalk) from

the total length of tape lowered into the well. To lessen the

possibility of computation errors, the “hold” position should be

either on even foot or 99 ft. The measurement should be repeated

to ensure its accuracy (two measurements of within 0.01 ft) and

that the measured water level is static.

Steel tape measurements usually are required in studies where

horizontal gradients are very low and, thus, are not accurately

determined with less accurate measuring devices. For water-supply

wells, particularly small-diameter (< 6 inches) domestic wells

with pitless adapters, the tapes may be used without the weight

to ensure against entanglement with the wiring and damage to the

contained pump.

3.5.2 Electric Device System

Electric measuring tapes typically consist of a pair of insulated

wires whose exposed ends are separated by an air gap in an

electrode and containing, in the circuit, a source of power such

as flashlight batteries. When the electrode contacts the water

surface, a current flows through the tape circuit and is

indicated by an ammeter-needle deflection, light, and (or)

audible signal. The “hold” depth against the reference point on

52

the well is read directly from the tape as depth to water. Recent

electric tapes are marked at 0.01 ft. Some tapes are marked at to

0.05 to 5 ft intervals, particularly tapes that are used in deep

wells (> about 500 ft). For these tapes the unmarked interval

must be estimated or measured with another device. Because the

tape medium may be easily bent and the weight is often less than

that used on steel tapes, the accuracy of electric tapes is

considered to be +- 0.02, but may be as great as 0.1 ft. The tape

can be calibrated against a steel tape and if several electric

tapes are used in a study, they should all be calibrated against

a reference steel tape. Calibration is especially important when

electric tapes are used in studies of where horizontal gradients

are small. If water levels are affected by nearby ground-water

pumping or previous use of the well (not static), the measurement

is more easily and accurately made with an electric tape.

Special sensing probes with an optical liquid sensor along and

conducting electrodes is used to simultaneously measure the

thickness of hydrocarbon layers floating on ground water and the

depth to water.

Water levels in water-supply wells may not be measurable by steel

or electric tapes if an access port is not present or the well

cap is not easily removed. Such wells, particularly high-capacity

industrial and municipal well use an air line for measurement.

This method involves the installation of a small-diameter pipe or

tube (the air line) from the top of the well to a point about 10

ft below the lowest anticipated water level and a pressure gage.

53

The water level in this pipe is the same as that in the well. To

determine the depth to water, an air pump with a sufficient

pressure rating (1 PSI = 2.31 ft H20) are attached to the top of

the air line (at a noted reference point and gage location). Air

is pumped into the line until all the water is displaced. This

occurs when the pressure indicated on the gage stabilizes. The

gage reading indicates the length of submerged air line. The

result of subtracting the submerged length of the air line from

the total length of the air line is the depth to water below the

measuring point. Air lines generally are accurate to about +- 1

ft.

Measurement of water levels often is intended to represent

“static” levels. For water-supply wells, the well should

generally not be used for a minimum of 30 minutes before

measurements are made. Longer time periods generally are required

for high-capacity wells.

Long term or near-continuous measurement of ground-water levels

is generally done with the use of pressure transducers and

automatic digital data loggers. Pressure transducers use silicon-

based strain gages that generate an electric current. The current

is calibrated to pressure (pounds per square inch) which can be

related to water levels by the equation: 1 psi = 2.31 ft of

water. Pressure transducers generally used vented cables to

eliminate response to atmospheric pressure changes (thus measured

changes do not include aquifer response to barometric pressure

fluctuations). Pressure transducers are selected on the basis of

54

expected water-level change. For example, 0-10 psi (up to 23 ft

change in level); 0-30 psi. The smallest acceptable range

provides the greatest measurement resolution. Accuracy generally

is 0.01-0.1% of the full scale range. For example, for a 0-10 psi

transducer with an accuracy of 0.01%, measurements will be to the

nearest 0.02 ft. Data loggers are use to store measurements.

Logger software allows measurement at various linear and

logarithmic intervals, setting of sensitivity limits for data

storage, and field calibration of the transducers.

Pressure transducers are temperature sensitive and cables are

subject to stretching with time. Thus, the transducers must be

both factory and field calibrated. To measure water levels,

select appropriate psi-range transducer. Submerge to transducer

to about mid-monitoring range (about 12 ft for 0-10 psi). Allow

it to acclimate to ground-water temperature for about 20 minutes.

Set factory-prescribed range, linearity, and offset for proper

quadratic conversion of electric signal to psi/feet of water.

Wrap a small piece of electrical tape on the transducer cable at

the top of the well casing. Using a measuring tape position

vertically on top of the well casing, raise the cable and

transducer 1.00 ft; check water level change using the data

logger. Raise cable another 1.00 ft. Check water level change

again. Lower the cable 1.00 ft, check change and repeat. Each

measurement should be within about 0.02 ft of the 1.00 ft raising

increments. Secure the cable to the well head, so it will not

slip and the reference tape can be used to monitor possible

55

slippage. Measure the depth to water with a steel or electric

tape and set reference depth in data logger (0.00 to record

relative change or depth to water or water-level altitude.

Periodically check the transducer reading with tape measurement

to monitor electronic drift or slippage of the cable. If drift or

slippage reset position and datum and adjust record accordingly

(prorating change in position/depth reading).

Major manufactures of pressure transducers include Druck and In-

Situ, Inc.

Major manufactures of data loggers include In-Situ, Inc. and

Campbell Scientific, Inc.

In-Situ’s Hermit loggers are preprogrammed and easy to use.

Campbell Scientific loggers are programmable and therefore very

flexible in their application, but may be difficult to use

because of the required programming language

3.6 Processing of Groundwater level data

Yearly groundwater level data of observation wells were collected from

BWDB. BWDB measures ground water level data in all season. They

provided the data of last 27 years (1980-2007). It is of every zone of

Dhaka and Narayangonj city. After rearranging the collected data the

missing data is filled by interpolation. Then averaging by arithmetic

mean formula then plotting the data some hydrographs and mappings are

drawn by using the selected data. The hydrograph showed the trend of

ground water level Variation in Dhaka division. And also the trend of

56

ground water level depletion of Dhaka and Narayangonj city shown by

hydrograph. Mapping of ground water level of all districts of whole

country of the year 2010 are shown. Ground water zoning map in 2010

collected from BADC are also shown.

3.7 Processing of population data

Population data is collected from BSS and World Bank. It provides the

population data up to year 2012. After collection data plotting and

drawing a hydrograph.

3.8 Ground water level variation analysis for Narayanganj city

The depletion of ground water level is different in zone

depending on the ground water extraction and recharge condition

for different location. In order to study the trend of ground

water level depletion in Narayanganj City, all the available data

of ground water level for the period 1986 to 2010 were collected

from DPHE and BWDB. The lowest ground water level is considered

for each year in order to plot hydrographs and mapping.

57

Chapter Four

DATA ANALYSIS4.1

Zone wise Ground Water Level analysis in Narayanganj City

Table 4.1 shows the maximum and minimum groundwater table data

has been studied from year 1980 to 2007 in a interval of ten

years for the three different locations of Narayanganj city

namely Chasara, Fatullah and Pagla. It has been observed that the

declining rate is very alarming for all three locations.

Table 4.1 Groundwater Table at Different Parts of Narayangonj

City Measured from Ground Surface (Source: BWDB 2007).

Location1980 1990 2000 2003 2007

Max Min Max Min Max Min Max Min Max MinNarayanganj Chasara

8.5 3.4 15.4

14.1

38.0 32.8

51.6 47.9

55.4 53.2

Fatulla 10.9

5.0 17.1

6.6 22.0 19.8

28.1 29.6

34.9 34.2

Pagla 10.1

7.0 16.1

14.5

25.2 23.3

29.7 27.6

33.7 31.5

4.2 Ground Water level analysis at Narayanganj city

Table 4.2Year wise average lowest GWL different in Dhaka and

Narayanganj city and Bangladesh (Source: BWDB).

Average Lowest Ground Water Level (in Meter)YEAR DHAKA AND

NARAYANGONGBANGLADESH YEAR DHAKA AND

NARAYANGONGBANGLADESH

1986 -19 -16 1999 -24 -161987 -19 -16 2000 -25 -18

58

1988 -20 -16 2001 -22 -211989 -22 -18 2002 -23 -211990 -21 -17 2003 -23 -201991 -21 -18 2004 -22 -201992 -24 -19 2005 -21 -211993 -22 -18 2006 -22 -221994 -22 -18 2007 -24 -201995 -25 -21 2008 -25 -221996 -23 -20 2009 -28 -241997 -24 -16 2010 -29 -261998 -24 -14

Table 4.3 Popular Pump Submersible Lift Capacity

(Source: RFL Water Pump Bangladesh)

59

4.3 Amount of extraction of water in Dhaka and Narayangonj city and whole Bangladesh

Figure 4.1 Amount of extraction in Dhaka and Narayangonj City(Source: BWDB).

Figure 4.2 Rainfall variations in whole Bangladesh (in ft)

Figure 5.9 Shows that the total amount of rainfall is almost same

every year. Although the rainfall is same, the recharge is same

60

but the abstraction is so high that the ground water level is

depleting.

4.4 Recharge Factor analysisRain water is the main recharge factor of ground water. Although

the rate of recharge by rainfall depends on the geology, soil

formation, characteristics of surface area.

61

Figure 4 .3 Ground Water Zoning Map in 2010 (Source: BWDB, 2004)

CHAPTER FIVE62

1980 1990 2000 2007

Chasara Ground Water

RESULTS AND DISCSSION

5.1Ground water level depletion from table 4.1

Figure 5.1 Declining trend of groundwater level at Chasara,Narayanganj.

Figure 5.1 shows the variation of maximum and minimum groundwater

table at Chasara over the period of 27 years from 1980 to 2007.

The sharp slope of the figure suggests that declining rate of

water table was very rapid and alarming. The maximum groundwater

table was 8.5 m below the ground surface in 1980, while in 2007

the water table depleted to a value of 55.4 m. On the other hand,

63

Ground

Water

Tab

le (

m)

Fatulla Ground Water

the minimum groundwater table was 3.4 m below the ground surface

in 1980, while in 2007 the water table depleted to a value of

53.2 m. On an average the water table has depleted by 1.79 m per

year recent few years being most rapid.

Year 1980 1990 2000 2007

Figure 5.2 Declining trend of groundwater level at Fatullah,Narayanganj.

Figure 5.2 shows the variation of maximum and minimum groundwater

table at Fatullah over the period of 27 years from 1980 to 2007.

The sharp slope of the figure suggests that declining rate of

water table was very rapid and alarming. The maximum groundwater

64

Grou

nd Water T

able

(m)

table was 10.9 m below the ground surface in 1980, while in 2007

the water table depleted to a value of 34.9 m. On the other hand,

the minimum groundwater table was 5 m below the ground surface in

1980, while in 2007 the water table depleted to a value of 34.2

m. On an average the water table has depleted by 0.98 m per year

recent few years being most rapid.

Year 1980 1990 2000 2007

65

Grou

nd W

ater

Table

(m)

Pagla Ground Water Table

Figure 5.3 Declining trend of groundwater level at Pagla,Narayanganj.

Figure 5.3 shows the variation of maximum and minimum groundwater

table at Pagla over the period of 27 years from 1980 to 2007. The

sharp slope of the figure suggests that declining rate of water

table was very rapid and alarming. The maximum groundwater table

was 10.1 m below the ground surface in 1980, while in 2007 the

water table depleted to a value of 33.7 m. On the other hand, the

minimum groundwater table was 7 m below the ground surface in

1980, while in 2007 the water table depleted to a value of 31.5

66

Grou

nd W

ater T

able

(m)

m. On an average the water table has depleted by 0.89 m per year

recent few years being most rapid.

Figure 5.4 Averages GWL in Narayangonj City (Source: BWDB)

From Figure 5.4 the above hydrograph of Narayanganj city it is

observed that the ground water level is declining at about a

constant rate (1.22 m/year). It is of great concern that the

recharge is almost zero due to the maximum area is covered by

building and pavement.

5.2 Ground water level analysis in whole Bangladesh

67

Depletion rate 1.22 m/year

Figure 5.5Averages GWL in Bangladesh (Source: BWDB)

The hydrograph of Bangladesh in show the average ground water

depletion rate are 0.3 ft/year (1986-2000) and 0.60 ft/year

(2000-10). In 1998 a great amount of recharge took place due to a

destructive and longtime flood. Ultimately to meet the increasing

demand of irrigation in whole country and domestic demand of

Narayanganj city the ground water level is going down very fast

out of reach of farmers.

Considering long time the declination rate is high in almost all

areas and in some areas the rate is quite alarming and may cause

devastating events like land subsidence and environmental

degradation. This gives an alarming indication that there is an

urgent need to alleviate pressure on the aquifer being exploited

and explore for more suitable and sustainable sources to

supplement the present water supply.

68

Figure 5.7 Amount of extraction of water in Bangladesh (km/year).

(Source: BWDB)

69

Figure 5.8 Refers that amount of extraction of water is

increasing at a rate of 1.26 km/year. Since the amount of

extraction is increasing every year in an alarming rate, so it is

high time to think about develop the source or to find

alternative source.

Chapter SixCONCLUSIONS AND RECOMMENDATION

6.1 Conclusions

In this study, the variation of groundwater table has been

studied from 1980 to 2007 for three different locations namely

70

Pagla, Fatullah and Chasara of Narayanganj city, Bangladesh. It

has been found that the groundwater table has depleted

significantly over this twenty seven years period for all three

locations. The main reason of such alarming depletion is the

increasing water demand of growing population. Another reason is

that the recharge of groundwater table is very low comparing to

extraction for different purposes. The above areas data and

graphical presentation prove that the ground water level is

declining at about an average constant rate (1.22m/year) in

Narayangonj city and the rate is quite alarming. Individually,

the depletion rate for Chasara, Fatullah and Pagla has been found

as 1.79 m/year, 0.98 m/year and 0.89 m/year respectively.It is of

great concern that the recharge is almost zero due to the maximum

area is covered by building and pavement. The depletion rate per

year suggests that it will be difficult to extract water by using

the current well technology within next few years. Even if the

improvement of those technologies can overcome this problem, the

economic feasibility will become questionable.

6.2 Recommendations

Due to time constraints and difficulty of finding required

data, the recent study has been carried out for only three

different locations namely Chasara, Fatullah and Pagla of

Narayanganj city. It is recommended that further study

should be carried out for as many locations as possible for

71

fully understanding the whole scenario of groundwater

variation.

The economic feasibility of abstracting water from gradually

decreasing water table should also be studied.

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