INTRODUCTION
Absolutely pure water is never found in nature but the water found in nature contains number of
impurities in varying amounts. The rainwater which is originally pure, also absorbs various gases,
dust and other impurities while filling. This water when moves on the ground further carries silt,
organic and inorganic impurities.
Wholesome water is defined as the water which containing the minerals in small quantities at
requisite levels and free from harmful impurities. The water that is fit for drinking safe and agreeable
is called potable water.
The following are the requirements of wholesome water.
➢ It should be free from bacteria
➢ It should be colourless and sparkling
➢ It should be tasty, odour free and cool
➢ It should be free from objectionable matter
➢ It should not corrode pipes
➢ It should have dissolved oxygen and free from carbonic acid so that it may remain fresh
Water Pollution
Perhaps the most obvious examples of a negative human impact on the environment is
water pollution. It's obvious we need water to survive but few people realize how much we
need and just how much is available. Consider these facts from the United Nations
Environment Programme:
1 Of all the water on Earth, only 2.5% of it is freshwater.
2 Of that 2.5%, less than 1% is available to us.
3 Humans each require up to 13 gallons (50 litres) a day of fresh water for drinking,
cooking and cleaning. This does NOT take into account the countless gallons of
water needed to grow food or care for animals.
4. 70% of all freshwater usage goes to irrigation
Land Pollution
Land pollution, the degradation of the Earth's surfaces and soil, is caused by
human activity and a misuse of natural resources. Causes of land pollution and
degradation include:
1. Urban sprawl: Natural habitats are removed to make room for communities, usually with
inefficient or irresponsible planning. Urban sprawl generally results in a waste of land
area for unused development
2. Poor agricultural practices: Animal manure runoff from CAFO (Confined Animal Feeding
Operations), the use of chemical fertilizers, herbicides and pesticides, the practice of
growing monocultures (only one crop season after season) and the deforestation
required to expand farm land all contribute to degradation and pollution.
3. Personal consumption: Our modern culture's desire to have more, bigger and better
"things", as well as our relationship to and habit of waste, has led to stripping of the
land, excessive mining and pollution from industrial activities.
4. Industrial activities: The production of chemical-laden plastics, poor quality of products,
unethical practices (such as illegal dumping), and extreme emissions affect both
surrounding and far-reaching areas.
Air Pollution
One bit of good news about our human impact on the environment is that air pollution is
lowering and air quality is increasing. According to the U.S. Environmental Protection
Agency, since 1990 to 2008: Ozone decreased 14%, Lead decreased 78%, Nitrogen dioxide
decreased 35% , Carbon monoxide decreased 68%, Sulfur dioxide decreased 59%.
Some important impacts of human activities on environment are outlined below:
1. Deforestation: In order to provide timber and farm land to increased population, large
number of forest trees are cut and forest area is converting to farm lands. The rate of
deforestation is so faster that around 1.5 million hectare of forest cover is lost every year is India
alone. The process of deforestation results in decreasing rainfall, increasing global temperature,
loss of top soil, modification of climatic conditions etc.
2. Industrialization: Although the industrial activities of man provide basic need of the
society, simultaneously the same release a lot of pollutants to the environment. The pollutants
in environment cause loss of raw materials, health hazards, increase in death rate, damage to
crop, making environment unfit for living organisms etc.
3. Loss of ecological balance: The excessive use, misuse and mis-management of biosphere
resources results in disturbance in ecosystem or ecological imbalance.
4. Air pollution: The anthropogenic release of various air pollutants to the environment causes
a number of dreaded phenomena like green house effect, ozone layer depletion, acid rain and
smog formation etc.
5. Water pollution: Human activities in respect of disposal of sewage wastes, solid wastes,
municipal wastes, agricultural and industrial wastes cause the environment unfit for day to day
use. Besides, polluted water spreads or leads to different diseases.
6. Increased consumption of natural resources: Since the starting of industrial era, the
natural resources are constantly utilised for the production of one or more products for the day
to day use of society.
7. Production of waste: Rapid industrialization and unplanned urbanization release a lot of
toxic waste material either in solid or liquid or gaseous state which induces a number of serious
environmental hazards.
8. Extinction of Wildlife: Since forests are natural habitats of wild life (both plants and
animals) deforestation leads to the extinction of valuable wild life and loss of biodiversity.
9. Habitual destruction: The commercial and industrial activities associated with mining,
construction of dams, fishing, agriculture etc. cause habitat destruction which is a pathway to
pollution.
10.Noise pollution: The man-made noise due to mechanized automobile, industries, trains,
aero planes, social functions etc. causes noise pollution which has impact on both biotic and
a biotic components of environment.
11. Radiation pollution: The radiations from radioactive substances used in nuclear reactors
and nuclear weapons can have significant impact on genetic materials of body (DMA, RHA)
12. Soil erosion: The anthropogenic processes like deforestation and overgrazing induce soil
erosion which causes soil moisture reduction, lowering of productivity, decline in soil fertility
etc.
SOURCES OF WATER
All the sources of water can be broadly divided into
1. Surfaces sources
2. Sub surface sources
The surface sources further divided into
i. Streams
ii. Rivers
iii. Ponds
iv. Lakes
v. Impounding reservoirs etc.
The subsurface sources further divided into
(i) Infiltration galleries
(ii) Infiltration wells
(iii) Springs
WATER DEMANDS
➢ While designing the water supply scheme for a town or city, it is necessary to determine
the total quantity of a water required for various purposes by the city.
➢ As a matter of fact the first duty of the engineer is to determine the water demand of the
town and then to find suitable water sources from where the demand can be met.
➢ But as there are so many factors involved in demand of water, it is not possible to
accurately determine the actual demand.
➢ Certain empirical formulae and thumb rules are employed in determining the water
demand, which is very near to the actual demand.
TYPES OF WATER DEMANDS
➢ Domestic water demand
➢ Industrial demand
➢ commercial demand
➢ Demand for public use
➢ Fire demand
➢ Loses and wastes
DOMESTIC WATER DEMAND
As per IS:1172-1963, under normal conditions, the domestic consumption of water in India is
about 135 litres/day/capita. But in developed countries this figure may be 350 litres/day/capita
because of use of air coolers, air conditioners, maintenance of lawns, automatic household
appliances.
Purpose Water Requirement/
Water Demand ( in Litres)
Drinking 5
Cooking 5
Bathing 55
Cloths Washing 20
Utensils Washing 10
House Cleaning/ Washing 10
INDUSTRIAL DEMAND
The water required in the industries mainly depends on the type of industries, which are existing
in the city. The water required by factories, paper mills, Cloth mills, Cotton mills, Breweries,
Sugar refineries etc. comes under industrial use. The quantity of water demand for industrial
purpose is around 20 to 25% of the total demand of the city.
INSTITUTION AND COMMERCIAL DEMAND
Universities, Institution, commercial buildings and commercial centers including office buildings,
warehouses, stores, hotels, shopping centers, health centers, schools, temple, cinema houses, railway
and bus stations etc comes under this category. As per IS: 1172-1963, water supply requirements for the
public buildings other than residences as follows.
Sl.No. Type of Building Construction per capita
per day (litres)
1. a) Factories where bathrooms are
required to be provided. 45
b) Factories where no bathrooms are
required to be provided 30
2. Hospitals per bed
a) No. of beds not exceeding 100 No. 340
b) No. of beds exceeding 100 450
3. No. Nurses homes and medical 135
4. quarters. Hostels 135
5. Offices 45
6. Restaurants (per seat) 70
7. Hotel (per bed) 180
8. Cinema concert halls and theatres (per
seat) 15
9. Schools
a) Day schools 45
b) Boarding schools 135
10. Garden, sports grounds 35 per sq.m
11. Animal/vehicles 45
DEMAND FOR PUBLIC USE
Quantity of water required for public utility purposes such as for washing and sprinkling on roads,
cleaning of sewers, watering of public parks, gardens, public fountains etc comes under public demand.
To meet the water demand for public use, provision of 5% of the total consumption is made designing
the water works for a city. The requirements of water for public utility shall be taken as given in Table,
Sl.No Purpose Water Requirements
1 Public parks 1.4 litres/m2/day
2 Street washing 1.0-1.5 litres/m2 /day
3 Sewer cleaning 4.5 litres/head/day
FIRE DEMAND
During the fire breakdown large quantity of water is required for throwing it over the fire to
extinguish it, therefore provision is made in the water work to supply sufficient quantity of water
or keep as reserve in the water mains for this purpose.
In the cities fire hydrants are provided on the water mains at 100 to 150 m apart for fire demand.
The quantity of water required for fire fighting is generally calculated by using different empirical
formulae.
For Indian conditions kuichings formula gives satisfactory results.
PER CAPTIA DEMAND
If ‘Q’ is the total quantity of water required by various purposes by a town per
year and ‘p’is population of town, then per capita demand will be
Per capita demand = [Q/ (P x 365)] litres/day
Per capita demand of the town depends on various factors like standard of living
and type of commercial places in a town etc.
Domestic purpose : 135
Industrial use : 40
Public use : 25
Fire Demand : 15
Losses, Wastage and thefts : 55
Total : 270 litres/capita/day.)
FACTORS AFFECTING PER CAPITA DEMAND
The following are the main factors affecting for capita demand of the city or town.
➢ Climatic conditions
➢ Size of community
➢ Living standard of the people
➢ Industrial and commercial activities
➢ Pressure in the distribution system
➢ System of sanitation
➢ Cost of water
Climatic conditions: The quantity of water required in hotter and dry places is more than cold countries
because of the use of air coolers, air conditioners, sprinkling of water in lawns, gardens, courtyards,
washing of rooms, more washing of clothes and bathing etc. But in very cold countries sometimes the
quantity of water required may be more due to wastage, because at such places the people often keep
their taps open and water continuously flows for fear of freezing of water in the taps and use of hot water
for keeping the rooms warm.
Size of community: Water demand is more with increase of size for town because more water is required
in street washing, running of sewers, maintenance of parks and gardens.
Living standard of the people: The per capita demand of the town increases with the standard of living
of the people because of the use of air conditioners, room coolers, maintenance of lawns, use of flush,
latrines and automatic home appliances etc.
Industrial and commercial activities: As the quantity of water required in certain industries is much
more than domestic demand, their presence in the town will enormously increase per capita demand of
the town. As a matter of the fact the water required by the industries has no direct link with the population
of the town.
Pressure in the distribution system: The rate of water consumption increase in the pressure of the
building and even with the required pressure at the farthest point, the consumption of water will
automatically increase. This increase in the quantity is firstly due to use of water freely by the people as
compared when they get it scarcely and more water loss due to leakage, wastage and thefts etc.
System of sanitation: Per capita demand of the towns having water carriage system will be more than
the town where this system is not being used.
Cost of water: The cost of water directly affects its demand. If the cost of water is more, less quantity of
water will be used by the people as compared when the cost is low.
POPULATION FORECASTING
When the design period is fixed the next step is to determine the population of a town or city population
of a town depends upon the factors like births, deaths, migration and annexation. The future development
of the town mostly depends upon trade expansion, development industries, and surrounding country,
discoveries of mines, construction of railway stations etc may produce sharp rises, slow growth,
stationary conditions or even decrease the population. For the prediction of population, it is better to
study the development of other similar towns, which have developed under the same circumstances,
because the development of the predicted town will be more or less on the same lines.
DIFFERENT METHODS WITH MERITS AND DEMERITS
The following are the standard methods by which the forecasting population is done.
1. Arithmetical increase method
2. Geometrical increase method
3. Incremental increase method
4. Simple graph method
5. Decrease rate of growth method
6. Comparative graph method and The master plan method
Problem: The following data have been noted from the census department.
YEAR POPULATION
1940 8000
1950 12000
1960 17000
1970 22500
Find the probable population in the year 1980, 1990 and 2000.
ARITHEMATICAL INCREASE METHOD
This method is based on the assumption that the population is increasing at a constant rate.
The rate of change of population with time is constant. The population after
decades can be determined by the formula.
Pn = P + n.c where population at present n No. of decades
Constant determined by the average of increase decades
GEOMETRICAL INCREASE METHOD
This method is based on the assumption that the percentage increase in population from decade to
decade remains constant. In this method the average percentage of growth of last few decades is
determined, the population forecasting is done on the basis that percentage increase per decade will be
the same.
The population at the end of n decades is calculated by, IG Pn
= P (1 + ) 100
Year Population Increase in Percentage increase in
population population
1940 8000 ---
1950 12000 4000 4000 x 100 = 50%
8000
1960 17000 5000 5000 x 100 = 41.7%
12000
1970 22500 5500 5500 x 100 = 32.4%
17000
TOTAL 14500 124.1%
AVERAGE 4833 41.37%
The population at the end of various decades shall be as follows:
YEAR EXPECTED POPULATION
1980 22500 + 41.37 / 100 x 22500 = 31808
1990 31800 + 41.37 / 100 x 31800 = 49935
2000 49935 + 41.37 / 100 x 49395 = 68524
INCREMENTAL INCREASE METHOD
This method is improvement over the above two methods. The average increase in the
population is determined by the arithmetical method and to this is added the average of the net
incremental increase once for each future decade.
Solution:
Year Population Increase in Incremental
population increase
1940 8000 --- ---
1950 12000 4000 ---
1960 17000 5000 + 1000
1970 22500 5500 + 1500
TOTAL 14500 + 2500
AVERAGE 4833 1,250
The population at the end of the various decades shall be as follows:
YEAR EXPECTED POPULATION
1980 22500 + (4833 + 1250) x 1 = 28583
1990 22500 + (4833 + 1250) x 2 = 34666
2000 22500 + (4833 + 1250) x 3 = 40749
1.1 VARIATIONS IN DEMAND
The per capita demand of town is the average consumption of water for a year. In practice it has
been seen that this demand does not remain uniform throughout the year but it various from season to
season, even hour to hour.
INCREMENTAL INCREASE METHOD
The water demand varies from season to season. In summer the water demand is maximum, because
the people will use more water in bathing, cooling, lawn watering and street sprinkling. This demand
will becomes minimum in winter because less water will be used in bathing and there will be no lawn
watering. The variations may be upto 15% of the average demand of the year.
DAILY VARIATIONS
This variation depends on the general habits of people, climatic conditions and character of city as
industrial, commercial or residential. More water demand will be on Sundays and holidays due to more
comfortable bathing, washing etc as compared to other working days. The maximum daily consumption
is usually taken as 180% of the average consumption.
HOURLY VARIATIONS
On Sundays and other holidays the peak hours may be about 8 A.M. due to late awakening where
as it may be 6 A.M. to 10 A.M. and 4 P.M. to 8 P.M. and minimum flow may be between 12P.M. to
4P.M. when most of the people are sleeping. But in highly industrial city where both day and night shifts
are working, the consumption in night may be more. The maximum consumption may be rise upto 200%
that of average daily demand.
The determination of this hourly variations is most necessary, because on its basis the rate of
pumping will be adjusted to meet up the demand in all hours.
1.2 DESIGN PERIOD
The complete water supply project includes huge and costly constructions such as dams,
reservoirs, treatment works and network of distribution pipelines. These all works cannot be replaced
easily or capacities increased conveniently for future expansions.
While designing and constructing these works, they should have sufficient capacity to meet future
demand of the town for number of years. The number of years for which the designs of the water works
have been done is known as design period. Mostly water works are
INCREMENTAL INCREASE METHOD
designed for design period of 22-30 years, which is fairly good period.
Design period is estimated based on the following:
1. Useful life of the component, considering obsolescence, wear, tears, etc.
2. Expandability aspect. Anticipated rate of growth of
population, including industrial,
commercial developments & migration-immigration.
3. Available resources.
4. Performance of the system during initial period
