The document outlines the critical need for protected water supply systems, emphasizing the various types of water demand, including domestic, industrial, institutional, and public needs. It highlights the importance of planning and designing water supply schemes to ensure the availability of safe, adequate, and quality water, along with emergency provisions for fire safety. Various factors affecting water demand and consumption, as well as methodologies for calculating these demands, are also discussed extensively.

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 WATER DEMAND
 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. INSTITUTIONALAND 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 50l/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 fighting isgenerally calculated by
using different empirical formulae.
 For Indian conditions Kuichling’s formula gives satisfactory results.
 Q=3182 √p
 Where ‘Q’isquantity of water required in litres/min
 ‘P’ispopulation of town or cityin 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%of total
quantity of water ismade 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 --------55 litres/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
SL NO POPULATION PER CAPITA DEMAND
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. VARIATION IN WATER DEMAND
 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 in summer
season, lesser use in winter, and
much less in rainy season.
Day to day variations ie daily
variations reflect household and
industrial activity
 People draw out more water on Sundays
and Festival days, thus increasing
demand on these days.

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 requirement istaken.
 It will be much higher than the average
daily demand. Where peak demands occur
in the morning and evening

32. VARIATION INWATER DEMAND

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.  Consumption in the early hours of morning is
generally small, increases sharply as the day
advances, reaching a peak value between 8 –
11 AM
 Then decreases sharply upto about 1PM,
remains constant upto about 4PM, again
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 known as
the designperiod.
Designperiodshould neitherbetoolongnorit
shouldbetooshort,usuallywaterworksaredesigned
for22-30years

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 at
future dates. For example, more difficult expansions mean choosing a higher
value of the design period.
 Amount and availability of additional investment likely to be incurred for
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 fewdecades 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 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.