Introduction 1

Chapter 1: Introduction
1.1 Importance of Water

Five most crucial for existence of human life are air, water, food, heat and light, of which next to
air, water is the most important requisite for human life to exit. The availability of a water supply
adequate in terms of both quantity and quality is essential to human existence. Water is perhaps
the most important nutrient in our diets. In fact, a human adult needs to drink approximately 2
liters (8 glasses) of water every day to replenish the water that is lost from the body through the
skin, respiratory tract, and urine. But some water sources cannot safely be used to meet our
requirement for drinking water. In fact, 99.7% of the Earth's water supply is not usable by
humans. This unusable water includes saltwater, ice, and water vapor in the atmosphere. Only
freshwater, which is contained in rivers, lakes, and underground sources, can be used for human
consumption. Furthermore, many freshwater sources are not suitable for humans to drink. Early
humans could judge water quality only through the physical senses of light, taste, and smell. Its
effects on human health and well-being may be vital. World health organization has observes
that 80% of communicable diseases that are transmitted through water. Many serious diseases,
like cholera, gastroenteritis, typhoid, amoebia, diarrhea, polio, hepatitis (Jaundice),
Leptospirosis, Dracontiasis etc. are caused by drinking water that contains parasitic
microorganisms. Water containing large amounts of industrial waste or agricultural chemicals
(e.g., pesticides) can also be toxic and unfit for drinking. Hence, humans have a great need for a
reliable source of clean freshwater for drinking.

In addition to the water needed for drinking, humans use much larger amounts of clean
freshwater in other applications. These other uses of freshwater include household use
(e.g., culinary and cleaning), industry, agriculture (e.g., irrigation), and recreation. Hence, the
quality of the freshwater supply is important for virtually every aspect of our lives.
In response to this need for reliable supplies of clean and usable freshwater, governments at all
levels have formed organizations and passed legislation to monitor, treat, and protect our water
supplies.

1.2 Definition of types of water

1.2.1 Pure and impure water
Pure water contains two parts of hydrogen and one part of Oxygen. Pure water (H20) is colorless,
tasteless and odorless. Absolutely pure water is not found in nature. Even the rain water which is
absolutely pure at the instant it is formed becomes impure because as it passes through the
atmosphere it dissolves certain gases, traces of minerals, dusts and various other substances.
Hence, pure water normally could be available only in laboratory. It is not actually suitable for
drinking purpose due to absence of vital minerals required for the human growth. Impure water
contains substances such as minerals, suspended and dissolved materials etc. In addition to H20
other minerals like Ca, Mg, fluoride, iodine, iron etc. is impure water. Impure water is used for
drinking purposes but substances should be within acceptable limit.

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 Introduction 2

1.2.2 Potable and wholesome water

Water fit for drinking purpose or safe enough to be consumed by humans or used with low risk
of immediate or long term harm is termed as potable water. Potable water is suitable for drinking
purpose having pleasant taste and useable for domestic purpose.
Water containing the minerals in small quantities at requisite levels and free from harmful
impurities is wholesome water minerals harmful to human health but contains useful or
beneficial to human health.
Requirements of wholesome water
1. It should be colorless and sparkling
2. It should be free from microorganisms, radioactive substance, dissolved gas, salts, heavy
metals etc.
3. It should be tasty, odor free and cool
4. It should be free from objectionable matter
5. It should not corrode pipes
6. It should have dissolved oxygen and free from carbonic acid so that it may remain fresh

“Water that is practically clear, colorless, odorless, palatable, sparkling and reasonably free
from objectionable chemical salts in solution and from microscopic organism in suspension is
called wholesome water.”

1.2.3 Polluted and contaminated water

Water containing excess amount of impurities such as minerals, salts, gasses,
microorganisms etc. is called polluted water. It is not fit for drinking purpose. It may contain
various types of impurities (Physical, chemical and bacteriological).

Containing something in water as harmful substances such as bacteria, virus, protozoa, worms,
heavy metals etc. that cause diseases is termed as contaminated water.

1.3 Historical development of water supply system

The process of supplying potable water from source to consumers through the network of pipes,
reservoir, and other appurtenances is known as water supply system or water supply scheme.

Evidence of activity concerned with human health and water supply has been found in
civilizations throughout human history. The human search for potable water supplies must have
begun in prehistoric times. Thousands of years passed before our more recent ancestors
learned to build cities and enjoy the convenience of water piped to the home and drains for
water-carried wastes.

The earliest human settlements were developed near the river bank as availability of plentiful
water. As civilization progressed, population increased and community expanded, small
community transformed into the village, village into town, and town into city. Over the years the
enormous demands being placed on water supply due to rapid increment in population.

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 Introduction 3

The water sources also gradually become polluted due to discharge of large amount of waste into
the sources. The ground water table has ongoing gradual depletion due to inadequate
recharge as infra structure developed by people and massive deforestation, drought as of climate
change, resulting low flow in surface water. The expansion of the community further from the
water source made water collection difficulty and time consuming. Hence a planned scheme with
free from pollution portable water to the consumers premises become necessitated. The provision
of water making within easy access to consumers is water supply system or water supply
scheme.

In Nepal, peoples use to fetching water traditionally from hiti, kuwa, dhunge dhara, pandhero,
streams, rivers in hilly areas and dug wells and tube wells in terai. The construction of well and
'Dhunge Dhara' was started in Lichhivi kaal', in the 5th to 7th centuries and progress found very
much encouraging in 'Malla kaal'.

History of piped water supply system development in Nepal dates back to 1895 A.D., when the
first Bir Dhara system (1891-1893) was commissioned. The system also led to establishment of
Pani Goshowara Adda and it provided limited private and community standpipes in few selected
parts of Kathmandu. The water service were then gradually extended to few other prominent
places like Amalekhgunj, Birgunj, Palpa and Jajarkot . The sector received a fair priority in the
First Five Year Development Plan, which started in 1956, but the sector activities were placed
under the Department of Irrigation for a long while until the Department of Water Supply and
Sewerage (DwSs) was formally established in 1972. DWSS is providing a
Nationwide service through its 5 regional, 48 divisional and 22 Sub-divisional offices spread
throughout the country.

The existing national water supply coverage of 37% in 1990 has been expanded to over 80% as
of today. The supply of potable water has been challenging for water supply authorities in
developing countries like Nepal. Prior to the year 2005, our country Nepal was following the
water quality standard of World Health Organization (WHO). Afterwards, Nepal's own
water quality standard National Drinking Water Quality Standard (NDWOS) has come into
effective.

In Nepal variety of multi and bilateral organizations, NGOs, INGOs, and Civil Society
organizations support and implement water supply schemes and provide services. Major
organizations working in water supply sector are; Department of Water Supply and Sewerage
(DWSS), Nepal Water Supply Corporation (NWSC), Kathmandu Upatekya Khanepani Limited
(KUKL), Rural Water Supply and Sanitation Fund Development Board (RWSSFDB), Water
supply and Sanitation User's Committee (WSUC), Department of Local Infracture Development
and Agriculture Roads (DoLIDAR).

The interim constitution of Nepal has defined access to water as a fundamental right to its
citizens and to support this, the country has set a target to provide all Nepalese with access to
basic water supply and sanitation services by 2017AD.

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 Introduction 4

1.4 Objectives of water supply system

The primary objective of water supply system is to supply water for consumer from the best
available source which will ensure water of good physical Quality, free from unpleasant taste or
odor and containing nothing which might be detrimental to health.

1. To provide safe wholesome water to the consumers in adequate quantity efficiently at

low cost.
2. To make water available within easy access to public.
3. To make adequate provisions for emergencies like fre fighting, festivals, meeting etc.
4. To save time in fetching water.
5. To supply water rich in reliability, quality, quantity in effective and efficient way.

1.5 Schematic diagram of typical water supply system

Typical schematic diagram of w/s scheme for urban area is

shown in figure 1.1. The components are collection works
includes intake and pump, transmission main, purification
works, reservoir and distribution systems. Pump may be
required in case of lifting due to elevated supply area than
the source. Water purification works may also optional as
depends upon source water quality.

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 Introduction 5

The population density of Nepal in rural areas

is low and houses are scattered but also
affordability of consumers for private
connection is low so that in rural area water
supply service is provided by public taps.
Typical schematic diagram of w/s scheme for
hilly rural area is shown in figure 1.2. In hilly
rural area common source is spring and
generally water quality of spring is not
necessary to treat. Hence water treatment is
not provided in hilly areas also power system
is avoided. Sometimes stream may be used in
rural areas as Source so sedimentation and
filtration is used but sedimentation may be
omitted or auxiliary. Break pressure tank
(BPT) also known as pressure releasing tank is
provided in distribution lines to prevent pipes
from bursting due to excess pressure as greater
elevation difference in rural areas and for the
same purpose interruption chamber (IC) is
provided in transmission mains.

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 Introduction 6

In terai either tube well or dug well is used as source for rural water supply system. Dug well
may be used by private households or small community where as tube wells are used by big
community. The water from the well is lifted to
elevated reservoir and provided to consumers through
public tap stand. Typical schematic diagram of w/s for
terai is shown as in figure 1.3.

1.6 Components of water supply system

Water supply system consists of; i) collection, (ii) transmission; (ii) purification and
(iv) distribution work as shown in figure 1-4.
The various components having own specific functions can perform a public water supply
scheme are as indicated below:

1. Source of water
2. Intake for collecting water
3. Pump
4. Collection chamber
5. Transmission main
6. Interruption chamber
7. Treatment/purification works
8. Reservoir
9. Control valves
10. Distribution system
11. BPT
12. Public stand post

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 Introduction 7

1. Source of water
Primary source of water is precipitation which joins to the earth in the form of rain, snow,
hail, etc. Rainfall is the most important source as it occurs is retained in surface depression,
carried away as surface runoff in natural channel in the form of stream or river and some
portion percolates into the. Ground further infiltrated to natural ground water reservoir. This
portion of precipitation that may be utilize for water supply as source of water is available
partly at the ground surface and partly below the ground surface.

2. Intake for collecting water:

These are device or a structure constructed at the source of water to draw off water which
conveys to treatment plant through a conduit. Various appurtenances such as strainer,
operating valve, pump, housing, conduit etc. are provided for operation and maintenance.

3. Pump
Pump is a lifting device commonly required to lift water from source which is operated by
the help of energy. Avoiding the use of this device save the operation and maintenance cost
of scheme but is essential when area to be served is located at a higher elevation than the
source

4. Collection chamber
When demand of water do not met by a single source it may be required. Additions to
collection of water from two or more sources this prevent the backflow of water one source
to another.

5. Transmission mains
Water conveyance from the source to treatment plant is entertained by pipe as known as
transmission main. Water from these pipes is not given to consumers though generally pipe
lay over the ground. Design of transmission pipe is considered for average flow.

6. Interruption chamber
These are the chamber provided in the transmission lines to prevent from bursting pipes
due excessive pressure. Hence function of these chambers is to release high pressure or
convert into atmospheric pressure forming the new static water level.

7. Treatment or purification works

Raw water may contain various impurities. The purpose of water treatment is to remove
those impurities which are objectionable either from taste and odor aspect or public health
aspect. The aim of water treatment is to produce and maintain water that is hygienically safe,
aesthetically attractive and palatable, in an economic manner.

8. Reservoir
Reservoir is used to reserve water. Depending on the purpose of use, it can be clear water
reservoir, balancing reservoir and service or distribution reservoir. Clear water reservoir is

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 Introduction 8

used for storing treated water, balancing reservoir for equalization or to address fluctuation of
demand whereas service or distribution reservoir for equalizes the hourly fluctuations and
Stores the water for break down reserve and fire reserve as for firefighting.

9. Control valves
These are essential appurtenances provided in the pipelines. There are various valves used for
different purposes like to control and regulate the flow of water, releasing valve, air relief
Valve, wash out valves etc.

10. Distribution system

It is a pipe network laying to deliver water to the consumers’ premises from the distribution
or service reservoir. Distribution system is designed for the peak flow. The method of laying
Distribution system is guided by the road network of the city.

11. Break pressure tank (BPT)

These are the tank or a chamber facilitated in the rural water supply distribution system to
overcome the failure by burst of pipes due to excessive pressure. The function of the BPT is
releasing high pressure into atmospheric pressure.

12. Public stand post

These are the last component of water supply system from where consumes collect water to
meet their household demand in rural area. If people cannot afford private connections in
rural area and as of scattered houses in the area a stand post serves to 8 to 10 households.

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