Unit 1 Introduction of water supply note(Second year second parts)
1.1 Introdution
Water supply engineering is the branch of civil engineering that deals with the supply of safe water for various purposes (eg. domestic, industrial, commercial and public supply) in sufficient amount efficiently.
1.2. Importance of planned water supply
Water is vital for our daily lives. Water is the main component of living cells. In cells, water content can found from nearly 40% in certain species of plants to more than 95% in cells of jellyfishes. The human body contains about 80% of water. A human body of 50 kg is made up of 40 kg of water and 10 kg only of other substances. The brain becomes unable to work properly without water in a day and one can die in 2 or 3 days without water. Five essential requirements for human existence are air, water, food, heat, light (Pancha tatwa). Among them, next to air, water is the most important requirement for the human life to exist. Water is essential not only for human life but also for animals, plants and all other living beings. Unlike many other raw materials, there is no substitute for water in many of its uses. Water is the most important natural resource in the world, as life cannot exist without water. Good sanitation cannot be achieved without adequate water supply. From ancient times human has obtained water from the surface sources such as streams, river, lakes, etc., as well as from the subsurface or ground water sources such as springs, wells, etc. Due to relatively less requirement of water, mainly for domestic purpose in the early times, these sources were deemed sufficient to meet the requirements of the persons residing in the nearby areas. As population increases, there becomes lack of ground and surface water quantity and contamination of water is due to the disposal of domestic and industrial waste in water stream. With the advancement of civilization, the utility of water enormously increased. Now such a stage has come that without well organized public water supply, it is impossible to run present civic life in safe environment and develop towns as well as villages.
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1.3 Objectives of Water Supply System
The broad objective
of the water supply system is to supply safe, wholesome and potable water to
the community in adequate quantity and residual pressure at a reasonable price.
The specific objectives are:
i. To supply safe, wholesome and potable water to consumers;
ii. To supply water in adequate quantity ;
iii.To make water easily available to the consumers;
iv. To supply water to the domesticated animals;
v.To supply water to the industries;
vi.To supply water to the commercial establishments;
vii.To save time in fetching water;
viii.To promote
the personal & household cleanliness;
ix.To provide water for firefighting purposes;
x.To prevent the spread of epidemic diseases; and
xi. To enhance the economic development of
country.
1.4 History of Planned Water Supply System in Nepal
Nepal's drinking
water supply has passed through various stages in history before today's modern
system. Summary of development in water supply system is presented here.
Stone spouts were introduced to the Kathmandu valley during the Lichhavi period, in the fifth to seventh centuries In 1895 A.D., piped water supply system was developed when the first BIR Dhara system was commissioned. Pani GoshowaraAdda was established to provide limited private and public stand pipes. There are 118 stone spouts in Kathmandu, 103 in Bhaktapur and 48 in Patan, which are constructed so many years ago. Department of Water Supply and Sewerage (DWSS) were formally established in 1972 A.D. to develop water supply system throughout Nepal. At present there are 28 Division office of water supply and sanitation under State Government and 7 central level offices under central government, working on development of water supply and sanitation project. Melamchi water supply project is under construction to supply water facility in Kathmandu Valley. Apart from this various government agencies like ministry of local development, Ministry of Urban Development and various nongovernmental agencies like UNICEF World Bank, Asian Development Bank (ADB), JICA etc. are also working in this field.
1.5 IMPACTS DUE TO WATER SUPPLY SYSTEMS.
There are two types of impact due to water supply systems.
A. Positive Impacts:-
a.Immediate Impact :-
i. Fetching time (long go and bring ) is saved so that this time can be used for other productive works.
ii. Improves hygienic condition so that time and money expenses for medicine fare saved.
iii. Safe, reliable, adequate and effective supply is gained.
b.Long Term Impact :-
i.Increases socio- economic activities of individuals, family and then community.
ii. Increases the living standard of the people.
iii.Help in the economic growth of whole nation.
B. Negative Impacts:-
a.Reduces downstream water and effects on aquatic life.
b.Decreases groundwater table.
c. May create dispute between downstream water users.
d.Pollution due to decreased quantity of water at downstream
1.6 Water supply and its impact on public health and environment
In Nepal, due to rapid population growth, unsanitary
disposal of wastes and other human activities, most of the water sources are
becoming polluted. The prevailing practice of open defecation, unscientific
disposal of human wastes and agricultural practices in most of the rural
villages have increased the level of microbiological contamination in the water
from streams, springs and ground sources. Water quality problems caused by
physical and chemical parameters have huge impacts on public health when the concentrations
are high.
In the terai regions, arsenic contamination and the
drawdown of the water table every year is another serious problems, with some
shallow tube wells becoming non-functional. There is a lack of consumer
awareness as well as a lack of proper monitoring systems including repair and
maintenance. Provision of water treatment is beyond affordability in terms of
manpower and cost due to the small size and scattered nature of installations,
and frequent landslides and intensive erosion processes in the hill creates
destruction in transmission and distribution systems.
Water pollution, falling groundwater tables, and
growing demands on limited water resources and need of investment have emerged
as significant challenges to the effective provision of water supply in Nepal.
Pooled impacts of urbanization, climate change and deprived population have
become increasingly vulnerable to water scarcity, waterborne disease, and
social exclusion from access to water. If wholesome water is to be supplied to
the community it can bring down the morbidity rates in Nepal.
Improving access to safe drinking water can result tangible benefits to public health and environment. Safe drinking water means there is reduce in health risk. Safe drinking water is suitable for all usual domestic purposes, including personal hygiene and environmental sanitation. Access to drinking water cannot guarantee access to safe water. The piped water is considered as a source of safe water. If the water quality is not proper, it may cause serious health hazard. In Nepal, piped water is also unsafe in most of areas almost throughout the year. Significant household suffer from water borne disease if they do not use their own disinfection system at household leve. Ensuring water quality is major challenge for municipal water suppliers in Nepa
1.6 Systematic Diagram Of Typical Water supply system
The layout of water
supply system and its component extending from the water source to the consumer
areas is called schematic diagram of a water supply system.
a. In Rural area
1.6 Components of Water Supply System and Their
Functions
The various components of water supply system
with their functions have been described below.
1. Intake
Intake is a structure or device constructed at
the water source for the purpose of drawing water from the source and conveys
it to the other components of the water supply system. Intake mainly comprises
of screen at open end to screen out large and floating materials, conduit to
convey the water from the source , valve to regulate the flow and housing in
the form of chamber or tower. There are many types of intakes depending on the
source types.
2. Pump
Pump is a device to lift the water from the
source. Pumping of water is required when the consumer area is at higher
elevation than the source. It should be avoided as far as possible to minimize
the cost.
3.Transmission
main
It is a pipe laid to convey water from source
to reservoir. It is designed for the flow equivalent to the maximum daily
demand. The transmission main and all other components located in it are
designed for the average flow as daily peak factor is considered to be one in
Nepal.
4.Collection
chamber
Collection chamber is provided either at the
intake site or near the intake site to collect the water from one or more
sources. It breaks the incoming water pressure into atmospheric pressure which
prevents the backflow of water from one source to another.
5. Public
stand Post(PSP):
It is a structure in the pipeline( usually in
the rural water supply system) from where water is distributed to the
consumbers.
6. Valves:
Valves are appurtenances provided in the
pipeline to control and regulate the flow of water , to prevent the flow in
opposite direction, to release the excessive pressure and to conduct other
functions.
7.Valve
Chamber : The chamber in which one or more valves are
located is called a valve chamber .
8.Fittings:
Fittings are those appurtenances that allow pipes to be joined or installed in
the appropriate place and closed where necessary.
9.Distribution
Chamber: It is a tank provided at the junction of the
pipeline when water has to be conveyed in more than one direction at
atmospheric pressure.
10. Distribution chamber: It
is tank provided at the junction of the pipeline when water has to be conveyed
in more than one direction at atmospheric pressure.
11.Interruption Chamber: It
is a tank present in the transmission main to break the excessive internal
water pressure built in the pipeline.
12.Reservoir: It is a tank or a
basin which is used to store water. It may be classified as clean water
reservoir and service reservoir. Clean water reservoir stores water after
treatment has been done and is used for water supply purposes. Service
reservoir stores water that is used for firefighting purposes
13.Distribution System: Distribution system is a network of pipeline that
conveys the water from the service reservoir to the consumer .It is designed
for maximum or peak flow.
14. Break pressure Chamber (BPC) : It is a tank that is located in the distribution system to break the excessive internal water
pressure built up in the pipeline. It reduces the cost as it avoids the
necessary of high pressure rating pipes. It is provided with the float valve.
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