1. The document discusses the need for protected water supply and outlines the various types of water demands that must be considered, including domestic, industrial, institutional, public use, and fire demands. 2. Key factors that affect per capita water demand are discussed, such as climate, cost of water, distribution pressure, standard of living, presence of industries, and the sewerage system. 3. There are wide variations in water demand by season, month, day, and hour that must be accounted for in water supply system design through consideration of peak versus average demand.

1. MODULE 01
Introduction: Need for protected water supply. Demand of Water: Types of water
demands -domestic demand, industrial, institutional and commercial, public use, fire
demand estimation, factors affecting per capita demand, Variations in demand of water, Peak
factor.
Design period and factors governing design period. Methods of population forecasting and
numerical problems

2. NEED FOR PROTECTED WATER SUPPLY
Water is a chemical compound and may occur in liquid, solid or gaseous
form.
All these three forms are extremely useful to man, providing him the luxuries and
comforts in addition to fulfilling his basic necessities of life.
No life can exists without water, since water is essential for life as the air is.
It has been estimated as two third of human body is constituted of water.
Water is essential for all the living beings on the planet.
The water for the use must be good and should not contain unwanted
impurities or harmful chemical compounds or bacteria in it.
So, in order to ensure the availability of sufficient quantity of good quality of water, it becomes
almost imperative in modern society, to plan and built suitable water supply schemes, which may
provide potable water to the various sections of community in accordance with their requirements
and demands.

3. The scheme of water supply should be useful for the purposes like cooking,
drinking, bathing, washing, fountains, gardens etc,.
Also, the scheme should provide sufficient quantity of water for the safety against the fire.
Also, the scheme will help attracting the industries and thereby helping in industrialization and
modernization of the society, consequently reducing the unemployment and ensuring better living
standards.

4. OBJECTIVES OF PROTECTED WATER SUPPLY
SCHEME
To supply safe
and wholesome
water to
consumers
To supply water
in adequate
quantity
To supply water
so that they
meet future
demand
To meet the
demand for
emergencies
To make water
easily available
to consumers so
to encourage
personal and
household
cleanliness

5. DEMAND OF WATER
Whenever an engineer is given the duty to design a water supply scheme for a particular section
of the community, it becomes imperative upon him, to first of all, evaluate the amount of
water available and the amount of water demanded by the public.
In fact, the first study is to consider the demand and then the second requirement is to find the
sources to fulfill the demand.

6. VARIOUS TYPES OF WATER DEMAND
While planning a water supply scheme, it is necessary to find out not only the total yearly water
demand but also to access the required average rates of flow and the variations in these rates.
The following quantities are generally assessed and recorded.
1. Total annual volume (V) in litres or million litres.
2. Annual average rate of flow in litres per day i.e V/365
3. Annual average rate of draft in litres per day per person(i.e litres per capita per day or lpcd)
called per capita demand (q).
4. Average rate of draft in litres per day per service ie. (V/365)* (1/ No of
services)
5. Fluctuations in flows expressed in terms of percentage ratios of maximum or minimum
yearly, monthly, daily or hourly rates to their corresponding average values.

7. It is very difficult to precisely assess the quantity of water demanded by the public, since there are
many variable factors affecting water consumptions. Certain thumb rules and empirical formulas
are generally used to assess this quantity which may give fairly accurate results. The various types
of water demands, which a city may have, may be broken down in to the following classes.
1. Domestic water demand
2. Industrial water demand
3. Institution and commercial water demand
4. Demand for public uses
5. Fire demand
6. Water required to compensate losses in wastes and thefts

8. DOMESTIC WATER DEMAND
This includes the water required in private buildings for drinking, cooking,
bathing, lawn sprinkling, gardening, sanitary purposes etc.
The amount of domestic water consumption per person vary according to the
living conditions of the consumers. As per IS: 1172-1993, the minimum
domestic consumption for a town or a city with full flushing system should
be taken at 200l/h/d; although it can be reduced to 135l/h/d for economically
weaker sections.

9. MINIMUM DOMESTIC WATER CONSUMPTION (ANNUAL AVERAGE) FOR
INDIAN TOWNS AND CITIES WITH FULL FLUSHING SYSTEMS
Use Consumption in litres per head per
day (l/h/d)
Drinking 5
Cooking 5
Bathing 75
Washing of Cloths 25
Washing of Utensils 15
Washing and cleaning of houses and
residences
15
Lawn watering and gardening 15
Flushing of water closets 45
Total 200

10. MINIMUM DOMESTIC WATER CONSUMPTION (ANNUAL AVERAGE) FOR
INDIAN TOWNS AND CITIES FOR WEAKER SECTIONS
Use Consumption in litres per head per
day (l/h/d)
Drinking 5
Cooking 5
Bathing 55
Washing of Cloths 20
Washing of Utensils 10
Washing and cleaning of houses and
residences
10
Flushing of water closets 30
Total 135

11. CONT…
.
The total domestic water consumption usually amounts to 50-60% of the
total water consumption.
The total domestic water demand shall be equal to the total design
population multiplied by per capita domestic consumption.

12. INDUSTRIAL WATERDEMAND
The ‘industrial water demand’ represents the water demand for industries, which are either existing
or likely to be started in future, in the city for which water supply is being planned.
This quantity will vary depending upon the number and types of industries present in the city.
The ordinary per capita consumption on account of industrial needs of a city is generally taken as
50l/h/d for smaller industries.
Separate provisions should be made for specialized industries.
In industrial cities, the per capita water requirement may finally be computed to be as
high as 450l/h/d or to be low as 50l/h/d

13. WATER DEMAND FOR CERTAIN IMPORTANT INDUSTRIES
S.
no
Name of Industry and
product
Unit of
production
Approximate quantity of water
required per unit of
production
1 Automobiles Vehicle 40
2 Distillery (Alcohol) Kilo litre 122-170
3 Fertilizers Tons 80-200
4 Leather Tons 40
5 Paper Tons 200-400
6 Special Quality
paper
Tons 400-1000
7 Straw board Tons 75-100
8 Petroleum refinery Tons 1-2
9 Steel Tons 200-250
10 Sugar Tons 1-2
11 Textile Tons 80-140

14. INSTITUTIONAL AND COMMERCIAL WATER
DEMAND
The water requirements of institutions such a hospitals, hotels, restaurants, schools and colleges,
railway stations, offices, factories etc. should also be assessed and provided for in addition to
domestic and industrial water demands as discussed above.
This quantity will certainly vary with the nature of the city and with the number and types of
commercial establishments and institutions present in it.
On an average, a per capita demand of 20l/h/d is usually considered to be enough to meet such
commercial and institutional water requirements, although of course, this demand may be as
high as 50 l/h/d for highly commercialized cities.

15. WATER DEMAND FOR INSTITUTIONS AND COMMERCIAL
ESTABLISHMENT
S no Type of institution or commercial
establishment
Average water consumption in
l/h/d
1 Offices 45-90
2 Factories
a) Where bathrooms are provided
b) Where no bathrooms are provided
45-90
30-60
3 Schools
a) Day scholars
b) Residential
45-90
135-225
4 Hostels 135-180
5 Hotels 180( per bed)
6 Restaurants 70(per seat)
7 Hospitals
(a) Number of beds less than 100
(b)Number of beds exceeding 100
340(per bed)
450(per bed)

16. Sl no Type of institution or commercial
establishment
Average water
consumption in l/h/d
8 Nurses homes and medical quarters 135-225
9 Railway stations
(a)Junctions and intermediate stations
where express trains will stop
(b)Intermediate stations where express
trains will not stop
70 (with bathing facilities) 45
(without bathing facilities)
45(with bathing facilities)
23(without bathing facilities)
10 Airports- International and domestic 70
11 Cinema halls and theaters (per seat) 15

17. DEMAND FOR PUBLIC USE
This includes quantity of water required for public utility purposes, such as watering of public
parks, gardening, washing and sprinkling on roads, use in public fountains, etc.
A figure of 10l/h/d is usually added on this account, while computing total water
requirement.
Sl no PurposeWater 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

18. FIRE DEMAND
In thickly populated and industrial areas, fires generally break out and may
lead to serious damages, if no controlled effectively.
Big cities, therefore generally maintain full fire fighting squads.
Fire fighting personnel requires sufficient quantity of water so as to throw it over the fire at high
speeds.
A provision should be made in water supply scheme for fighting fires.
Fire hydrants are usually fitted in water mains at about 100-150 meters apart, and fire fighting
pumps are immediately connected in to them by the fire brigade personnel, as soon as fire breaks
out.
These pumps then throws the water on fire at very high pressure, so as to bring it in to control.
The minimum water pressure available at fire hydrants should be of the order of 100 to
150kN/m2 (10 to 15m of water head) and should be maintained even after 4 to 5 hours of
constant use of fire hydrant.

19. Generally in a moderate fire breakout, three jet streams are simultaneously thrown from
each hydrant; one on the burning property, and one each on adjacent property on either
side of the burning property.
The discharge of each stream should be about 1100litres/minute.
Hence in a big city having population of 50lakhs, if six fire breaks out in a day and each
fire stands for 3 hours, the total amount of water required shall be given by
6*(3*1100)*(3*60)= 3564000 litres/day
ie, (Number of fires* Discharge*Time of each fire)
The amount of water required per person= 3564000/ Population
= 3564000/5000000
= <1 litre/person/day

20. The high rate of water consumption during a fire considerably affects the design of
distribution system, and hence while designing the water supply scheme.
 The quantity of water required for fire fightingis generally calculated by using different
empiricalformulae.
 For Indian conditions Kuichling’s formula givessatisfactoryresults.
 Q=3182 √p
 Where ‘Q’isquantity of water required in litres/min
 ‘P’is population of town or city in thousands
 Freeman’s formula
Q=1136(P/5+ 10)
Bustons formula
Q = 5663 √P
National board of fire underwriters formula
Q = 4637 √P (1-0.01 √P )

21. LOSSES AND WASTES
 Losses due to defective pipe joints, cracked and broken pipes, faulty valvesand fittings.
 Losses due to, continuous wastageof water.
 Losses due to unauthorised and illegal connections.
 While estimating the total quantity of water of a town; allowance of 15% oftotal quantity of
water is made to compensate for losses, thefts and wastageof water.

22. WATER CONSUMPTION FOR VARIOUS PURPOSES
Typesof
Consumption
Normal Range
(lit/capita/day)
Average %
1 Domestic
Consumption 65-300 160 35
2 Industrial and
Commercial
Demand
45-450 135 30
3 Public Uses
including Fire
Demand
20-90 45 10
4 Losses and
Waste 45-150 62 25

23. PER CAPITA 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
Q
 Per capita demand =------------------litres/day
P x 365

24.  Per capita demand of the town depends on various
factors like standard of living, no. and type of
commercial places in a town etc.
 For an average Indian town, the requirement of water
in various uses is as under-
Domestic purpose --------
Industrial use --------
Public use --------
Fire Demand --------
135 litres/c/d
40 litres/c/d
25 litres/c/d
15 litres/c/d
Losses, Wastage and thefts --------55litres/c/d
Total : 270 litres/capita/day

25. FACTORS AFFECTING PER CAPITA
DEMAND/ RATE OF DEMAND
 Climatic conditions
 Cost of water
 Distribution pressure
 Standard of living
 Industries
 Policy of metering
 Quality of water
 Sewerage system
 Size of city
 System of supply

26.  Climatic conditions
Requirement of water in summer is more than
that in winter
 Cost of water
Higher the cost, lower will be the rate of
demand
 Distribution pressure
consumption of water increases with the
increase in the distribution pressure
 Standard of living
Rich and upper class community consume more
water due to their living standards

27.  Industries
The presence of industrial and commercial activities
at a particular place increases the water consumption by
large amounts
 Policy of metering
Installation of meters reduces the rate of consumption
 Quality of water
If the quality and taste of the water supplied is good,it
will be consumed more
 Sewerage system
water consumption will be more if city is provided
with flush system

28.  Size of city
smaller the city, lower is the rate of demand
 System of supply
supply of water may be continuous or intermittent
SLNO POPULATION PER CAPITADEMAND
IN
LITRES/DAY/PERSON
1 Less than 20000 110
2 20000-50000 110-150
3 50000- 2 lakh 150-240
4 2 lakh-5 lakh 240-275
5 5lakh-10lakh 275-335
6 over 10lakh 335-360

29. VARIATIONIN WATERDEMAND
 There are wide variations in the use of water in different seasons,
in different months of the year, in different days of the month, in
different hours of the day and even in different minutes of the
hour

30. Seasonal variations occur due to
larger use of water
season, lesser use in
in summer
winter, and
much less in rainy season.
Day to day variations
variations reflect household
ie daily
and
industrial activity
 People draw out more water on Sundays
and Festival days, thus increasing
demand on thesedays.

31.  Hourly variations are very important as they have a wide range.
During active household working hours i.e. from six to ten in the
morning and four to eight in the evening, the bulk of the daily
requirementistaken.
 It will be much higher than the average daily demand. Where
peak demands occur in the morning andevening

32. V
ARIATIONIN W
A
TERDEMAND

33.  Average rate of demand is represented by a
dotted line in graph
 Area above dotted line indicates shortage of
water and below dotted line indicates surplus
water
 Peak demands occur in the morning and
evening
 Slack periods occur early in the morning and
late at night

34.  Then decreases sharply upto about 1PM,
remains constant upto about 4PM, again
 Consumption in the early hours of morning is
generally small, increases sharply as the day
advances, reaching a peak value between 8 –
11AM
increases in the evening reaching a peak
between 7 – 9 PM, finally falling in the late
hours of night

35. EFFECTS OF VARIATION ON DESIGN OF WATER SUPPLY
SCHEME
 Sources of supply
 Pipe mains
 Filter and other units
 Pumps
 Distribution system
 Service reservoir

36.  The sources of supply such as wells, etc., may be designed for maximum
daily consumption or sometimes for average daily consumption.
 The pipe mains taking the water from the source up to the service reservoir
may be designed for maximum daily consumption.
 The filter and other units at water treatment plant may also be designed for
maximum daily draft. Sometimes, an additional provision for reserve is also
made for break- downs and repairs. Therefore, they may be designed for twice
the average daily instead of 1.8 times the average daily.

37.  The pumps lifting the water may be designed for maximum daily draft
plus some additional reserve for break-downs and repairs; say, for twice the
average daily instead of 1.8 times the average daily. Note. When the pumps
do not work for all the 24 hours, such as in small town supplies, the design
draft should be multiplied by24No. of hours in the day for which the pumps
are running
 The distribution system (including the pipes carrying water from service
reservoir to distribution system) should be designed for maximum hourly
draft of the maximum day or coincident draft with fire, whichever is more.
Generally, no provision for reserve is made.

38.  The service reservoir is designed to take care of the hourly fluctuations, fire
demands, emergency reserve, and the pro-vision required when pumps have
to pump the entire-day's water in fewer hours than 24 hours. Only 2 hours
storage may be considered for fire allowance as sufficient. Ordinarily, the
required storage approximates a day's consumption.

40. DESIGN PERIODS
 Water supply scheme includes huge and costly structures which cannot be
replaced or increase their capacities, easily and conveniently because
replacement can cause some other complications
 In order to avoid these future complications of expansions, the various
components of a water supply scheme are purposely made larger, so as to
satisfy the community needs for a reasonable numbers of years to come

41.  The future period for which a provision is made in the water
supply scheme is knownas the designperiod.
 Designperiodshould neitherbetoolongnorit shouldbetooshort
,usuallywaterworksaredesigned for 22-30years

42. FACTORS GOVERNING THE DESIGN
PERIOD
 Useful life of component structures and the chances of their becoming old and
obsolete. Design periods should not exceed those respective values.
 Ease and difficulty that is likely to be faced in expansions, if undertaken a
future dates. For example, more difficult expansions mean choosing a highe
value of the design period.
 Amount and availability of additional investment likely to be incurred fo
additional provisions. For example, if the funds are not available, one has to
keep a smaller design period.

43.  The rate of interest on the borrowings and the additional money invested. For
example, if the interest rate is small, a higher value of the design period may be
economically justified and, therefore, adopted.
 Anticipated rate of population growth, including possible shifts in communities,
industries and commercial establishments

44. POPULATION FORECASTING METHODS
 Population is used to indicate the total number of human beings
residing in a certain area at any particular time
 Water supply project is not designed only for present population but
also made to accommodate the future.
 After fixing the design period ,the next step is to determine the
population of a town or a city which is called as population
forecasting

45.  Arithmetic Increase Method
 Geometric Increase Method
 Incremental Increase Method
 Simple Graphical Method
 Comparative Graphical Method
 Decreasing Rate of Growth Method
 The Master Plan Method or Zoning Method
 The Ratio Method or The Apportionment Method
 Logistic Curve Method
DIFFERENT METHODS OF POPULATION FORECASTING

46. ARITHMETIC 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 ‘n’ decades can be determined by
the formula
Pn =[P+n. ¯x] where
 Pn - Forecasted population after ‘n’ decades from the
present
 Po -Population at present
 n - No. of decades
 x –Average of population increase in the known decades

47.  ADVANTAGES
Suitable for large and old city with considerable
development
 DISADVANTAGES
If it is used for small, average or compatively new
cities, it will give lower population estimate than actual
value

48. GEOMETRIC 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 at the end of ‘n’ decades is
calculated by- Pn = PO [1 +r/100]where
 Po - initial population
 Pn -future population
 r - assumed growth rate

49.  Assumed growth rate can be calculated by,
r= t√P2/P1 − 1
P1 = initial known population,
P2 = final known population
t = no of decades between P1 and P2

51.  ADVANTAGES
Gives better results for old cities which
are not undergoing further development
 DISADVANTAGES
Fixation of percentage in case of
developing cities should be done carefully,
or it may give high results

52. INCREMENTAL INCREASE
METHOD
 This method is improvement over the
above twomethods.
 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.