Quantity of Water

Quantity of Water
Group members
Chandan, 055
Chitra, 056
Dashrath, 057
Deepak, 058
Devesh, 059
Dinesh, 060
2075-09-15
Tutor
Asst. Prof. Shukra Raj Paudel
Department of Civil
Engineering
IOE, Tribhuvan University
1

Objectives of the Presentation
Factors determining the quantity of water to be supplied
Loss and wastage during water supply
Determination of total water demand
Variation in water demand
Factors affecting demand of water
Population forecasting and its different methods
2
Students will be able to learn the following things:

Presentation Outline
3.0 Introduction
3.1 Per Capita Demand of Water
3.2 Base and Design Periods
3.3 Types of Water Demands
3.4 Variation in Demand of Water
3.5 Peak factor
3.6 Factors Affecting Demand of Water
3.7 Population Forecasting
3.8 Problems on Population Forecasting
3

Introduction: Quantity of Water
Why to study about Quantity of Water?
 To estimate the water demand for the community
 To design the water supply system with long term benefits
 To determine the capacity of the reservoir used in water
supply system
 To find the suitable water resources that can meet the
demand.
4

Factors to be known before Designing Water Supply
System
Population
Per Capita
Demand of Water
Base and Design
period
5

3.1 Per Capita Demand of Water
 Average quantity of water consumption or water demand for various
purposes per person per day
 Usually expressed in liters per capita per day(lpcd)
 Per Capita demand in lpcd =
Q
P ×365
Where,
Q= total quantity required per year in litres
P= per capita demand of water
 It varies from person to person, place to place and time to time
 Water demands in liters/d= Per capita demand ×Population
6

3.2 Base and Design Periods
Base Period:
 Period required for the surveys, design and construction of a water supply
system
 The base period of 2-3 years is normally adopted
Design Period:
 Future period for which a provision is made while planning and designing a
water supply project
 It is generally adopted as 15 to 20 years for rural water system and upto 30
years for urban water system
 In communities with rapid development, low design period is adopted
7

3.2.1 Typical Base and Design Periods
Community Base Period
(Years)
Design Period
(Years)
Rural water supply system with
low population growth rate
2-3 20
Rural water supply system with
high population growth rate
2-3 15
Urban water supply system 2-3 Up to 30
8

3.2.2 Base Year:
The year in which water is delivered to the community by a water supply system
after the completion of its construction is known as base year
9
Survey
year
Base
period
Base
year
3.2.3 Design Year:
The year for which a water supply system is designed is known as design year.
Base
year
Design
period
Design
Year

Here’s a Question…???
Q) Should Water Supply System be designed only in the areas
where there is scarcity of Water or necessity to maintain the Water
Demands?
 The answer is No. Because water supply system doesn’t only helps to
maintain the water demands but also maintain the quality of water. It helps to
provide good quality of water suitable for drinking purpose which is in
accordance with WHO and National Drinking Water Quality Standards
10

Selection Basis
Of Design
Period
Population
Growth
Rate
Developmen
t of
Community
Useful Life
Of
Component
Structures
Availability Of
Water At
Source
Rate Of
Interest On
Borrowings
Availability
Of Funds
11

3.2.4 Selection Basis of Design Period
1) Population Growth Rate
 For high population growth rate shorter
design period is adopted and vice versa.
12
2) Development of Community
 If the community is rapidly developing
there will be high population growth rate
so shorter design period is adopted.

3) Useful Life of Component Structures
 The design period should not exceed the
useful life of the component structures which
depends on the quality and type of materials
used.
4) Availability of Funds
 When limited funds are available shorter
design period is adopted and vice versa.
Source: nextcity.org
Source:en.wikipedia.
org
13

5) Rate of Interest on
Borrowings
 If the money to be borrowed for a
water supply project is available at
a lower rate of interest, then a
longer design period may be
economically justified and
selected.
6) Availability of Water at
Source
 When water available at the
source is limited shorter design
period is adopted and vice versa.
14

Uses of Water in Different Sectors 16
Source: pub.gov.sg

3.3.1 Domestic Water Demand 17
Drinking Washing
Cooking Source: shutterstock.com

3.3.1 Domestic Water Demand
 This includes the water required for use in private residences apartment
houses, etc for drinking, cooking, bathing, washing of clothes, washing of
utensils, washing and cleaning of houses and sanitary purposes, etc.
 Amount of water consumption depends upon living conditions of consumer.
 In Nepal, we use generally use following value:
112 lcpd for fully plumbed houses;
65 lcpd for partly plumbed houses;
45 lcpd for rural areas served by public stand posts.
18

3.3.2 Livestock Demand
 Water consumed by horses, cows, pigs, goats, sheep, chickens, etc.
 Many of livestock utilize natural rivers, streams, and ponds for the water
during grazing.
 The livestock demand in Nepal is generally taken as follows:
19
S.N Type of Animals Examples Daily Consumption
1. Big animals Cows, horses 45 liters/animal/day
2. Medium sized animals Goats, sheep, pigs 20 liters/animal/day
3. Small animals Ducks, chickens 20 liters/100animal/day
Source: Water supply Engineering book writer prof. Dr. Bhagwan Ratna
Kansakar
 Livestock demand should not be more than 20% of domestic demand.

3.3.2 Livestock Demand 20
Source: gettyimage.com
Natural source unavailable Natural source available

3.3.2 Livestock Demand 21
Q) Why livestock demand is to be considered?
 The major reason behind this is the increasing demand of animal products
for which animals are to be reared and livestock demand are to be
considered in addition to the natural source available.

3.3.2 Livestock Demand
Q) Why is only 20% of domestic demand is considered for livestock
demand even if livestock demand>20% of domestic demand?
22
The reason behind this are
 Many of the livestock will utilize natural rivers streams and ponds for water
during grazing.
 In urban areas the number of livestock is low and hence can be neglected.

3.3.3 Commercial Demand
 This includes the water demand of commercial establishment such as
educational institutions, offices, hotels, hospitals, restaurants, etc.
 The quantity of water required for this purpose will vary considerably with
nature and type of the commercial establishments.
 The commercial demand should be considered for water supply systems in
both the rural and the urban areas.
 The reason behind this is the presence of commercial establishments both
in rural and urban areas.
 The commercial water demand in Nepal is generally taken as:
23

3.3.3 Commercial Demand
24
S.N. Commercial Establishment Water Demand
1. Day-scholars in educational institutions 10 liters/pupil/day
2. Boarders in educational institutions 65 liters/pupil/day
3. Offices(depending upon size) 500-1000 liters/day
4. Hospitals with bed 500 liters/bed/day
5. Hospitals without bed and health clinics 2500 liters/day
6. Hotels with bed 200 liters/bed/day
7. Hotels without bed 500-1000 liters/day
8. Restaurants and tea stalls 500-1000 liters/day
Kansakar

3.3.4 Public/Municipal Demand
 This includes the water required for public or municipal utility purposes.
 A provision of 5 to10 percent of total consumption is made for these demands
(No specific guidelines).
25
Source :lehiut.govconserveparks-
schedule
Source: nextcity.org

26
Road washing, sprinkling of water on
dusty roads and washing markets.
Cleaning of sewers
3.3.4 Public/Municipal Demand
Source: alamystock.com

3.3.5 Industrial Demand
 It represents the water consumed by the industries.
 For a city with fans and factories, a provision of 20 to 25%of total
consumption may be made for this purpose.
 The forecast for this demand will be based on nature and magnitude of each
industry and the potential for its expansion.
 Considered for urban communities only.
27

3.3.5 Industrial Demand 28
Source: blog.ipleaders.org

3.3.6 Fire Demand
 Quantity of water required
for fire fighting purpose.
 Considered only in urban
communities.
29
Source : firedemand.rar

Fire Demand is usually determined by using empirical
formula:
30
S.N Empirical Relation Name Empirical Relation
1. Indian water supply manual and
treatment formula
Q(kiloliters/day)=100√P
2. Buston's Formula Q(liters/min)=5663√P
3. Kuichling’s Formula Q(liters/min)=3182√P
4. Freeman’s Formula Q(liters/min)=1136(p/3+10)
5. National Board of Fire Underwriters’
Formula
Q(liters/min)=4637√P(1-0.01√P)
Where, P=Population in
thousands
Source: Water supply Engineering book writer
prof. Dr. Bhagwan Ratna Kansakar

3.3.6 Fire Demand(Continued…)
 DWSS design guideline recommends Indian Water Supply Manual and
Treatment Formula in Nepal for the determination of the water required for
the fire fighting purpose.
 Guideline recommends that Fire demand should be less than one lpcd.
31

Problem 1:
Q) Calculate the water required for fire demand in a city of
population 100,000 using various formulae.
Solution:
Given;
P=population in thousands=100
32

33S.N
.
Empirical Relation
Name
Empirical Relation Water Demand
1. Indian water supply
manual and
treatment formula
Q=100√100=1000
kiloliters/day=0.011574cums
ecs
2. Buston's Formula Q=5663√100=56630
liters/min
3. Kuichling’s Formula Q=3182√100=31820
liters/min
4. Freeman’s Formula Q(liters/min)=1136(p/
3+10)
Q=1136(100/5+10)=34080
liters/min
5. National Board of
Fire Underwriters’
Formula
Q=4637√100(1-
0.01√100)=41377liters/min

3.3.7 Loss and Wastage of Water
 Caused due to leakage in
mains, valves and other
fittings, worn or damaged
meters, theft of water through
the various unauthorized
connections, etc.
 Cannot be precisely predicted.
34
Source: valleywaterservices.com

3.3.7 Loss and Wastage of Water
 Only considered in urban communities as the allowance for it has been
already made in domestic demand for rural water supply system.
 In general, water loss occurs at the following ways :
35
S.N
.
Water Supply System Water Loss
1. Well maintained and fully metered supply
system
15% of total supply
2. Partly metered and partly unmetered supply
system
Up to 50% of total system
Kansakar

3.3.8 Total Water Demand
36
TWD=DD+LD+CD+PD+ID+FD+LW

Water Consumption for Different Countries:
37
Source: wikepedia.org

Water Demand Pie Charts for Different Areas
Source: researchget.net
39

3.4 Variation in Demands of Water
40

a) Seasonal Variation
 The rate of demand of water varies from season to season. In Nepal, the
variation in rate of demand due to season is very low, so the seasonal
variation is generally neglected in Nepal.
 Maximum seasonal demand
= seasonal peak factor * Annual average demand
The seasonal peak factor is assumed as 1 in Nepal
41

b) Daily Variations
 The demand of water varies from day to day. This is due to change in the day
to day climatic conditions, or due to the festival day or due to the day being
holiday. The rate of demand on Saturday is more than other days because
more water is used for washing, bathing, etc.
Similarly, the rate of water demand will be more on festival day than other
days.
Maximum daily demand,
=Daily peak factor * Annual average demand
42

c) Hourly Variations
 Maximum hourly demand,
=Hourly peak factor * Annual average
demand
The hourly peak factor of 2 to 4 is adopted
in Nepal while the hourly peak factor of 1.5
is generally adopted in India.
43
Source: prof .Dr.B R K,water supplyengineering

3.5 Peak Factor
 Peak factor is the ratio of maximum or peak demand of water to that of
annual average demand of water. In other words, the maximum or peak
demand of water is calculated multiplying the annual average demand of
water by the peak factor.
 Peak Factor(PF) =
Maximum Water Demand
Annual average demand of water
Peak factor= Seasonal peak factor * Daily peak factor * Hourly peak factor
44

Factors Affecting Demand of Water
Size and type of
community
Climatic conditions
Standard of living
Quality of water
System of supply
Pressure in the distribution
system
Sewerage System
Metering
Cost of water
45

3.6.1) Size and Type of Community
 In general, bigger is the community, higher is the demand of water
 Large quantity of water is required for public or municipal purposes
 Small community has less per capita consumption of water because there
are limited uses.
46

3.6.2) Climatic Conditions
 Requirement of water is more in summer than in winter.
 Water requirement is more in communities having hot and dry climates
than in communities having cold climates
 Used for washing, bathing, air conditioning, etc in communities with hot
and dry climate
 Taps are kept open to avoid the freezing of pipes which increases the rate
of consumption.
47

3.6.3) Standard of Living
 Higher the standard of living, greater the water demand because people can
afford luxury and use more water.
48
Source: shuterstock.com

3.6.4) Quality of Water
 Water consumption will be more if the quality of water supplied is good
 Consumers will feel safe to use water and use it liberally
49
S.N Types of Supply Demand Cause
1. Continuous- 24 hours High Sufficient Supply
2. Intermittent -limited Low Limited water is
supplied
3.6.5) System of Water Supply

3.6.6) Pressure in the Distribution System 50
Low
Pressure
Moderate
Pressure
High Pressure
Source: www.plumbingsupply.com

3.6.7) Sewerage System
 Sewerage system increases water demand.
 Water is required for: flushing urinals, cleaning closets
51
suyapi.com

3.6.7) Metering
 Meters are fitted at the head of the individual house connections, which
records the quantity of water consumed.
 Water consumption is less if consumers are charged for water consumed.
 To check loss and leakage of water.
 Also reduces water demand
52
Source:
en.wikipedia.org

3.6.8) Cost of Water
 Higher the cost of water, less is the demand of water
 In Kathmandu Valley, the average cost of water is 20 per
unit
53
Source:
shutterstock.com

54
3.7) Population Forecasting
Q) What is Forecasting?
 Forecasting is the process of making predictions of the future based on past
and present data and most commonly by analysis of trends.
 Forecasting has applications in a wide range of fields where estimates of
future conditions are useful.
 Not everything can be forecasted reliably, if the factors that relate to what is
being forecast are known and well understood.

Q) Why is the Population Forecasting carried out?
 Population of a certain area , either town or a village is always a dynamic
parameter. So, one need to consider the future demand of water, most often
the greater one, so as to avoid the subsequent changes in water supply
system that needs to be considered for a dynamic population which may be
uneconomic and unsustainable.
55

 To calculate water demand for present as well as future requirements.
 Information about the population of a city or town is obtained from census.
 Census is conducted at an interval of 10 years.
56
Arithmetical Increase Method
Decreased Rate Of Growth
Method
Incremental Increase Method
Geometrical Increase MethodMethod Of
Population
Forecasting

575757Some other methods of Population Forecasting
 Simple Graphical Method
 Graphical Comparison Method
 Master Plan/ Zoning Method
 Ratio and Correlation Method

3.7.1) Arithmetical Increase Method
 Simplest method of population forecast.
 Gives lower results.
 Increase in population from decade to decade is assumed constant.
 Generally adopted for large and old cities which have practically reached
their maximum development.
 The future population Pn after n decades is given by the expression given
below.
Pn = P + nI
Where Pn = future population at the end of n decades
P = present population
I = average increase in population for a decade
59

3.7.2) Geometrical Increase Method 60
 Gives higher results.
 Percentage increase in population from decade to decade is assumed
constant.
 Generally adopted for new industrial town at the beginning of
development for only few decades.
below.
Pn= P 1 +
r
100
n
r = average percentage increase in population per decade

3.7.3) Incremental Increase Method
 Gives average results.
 Suitable for an average size town under normal condition where the growth
rate is found to be in increasing order.
 Incremental increase in population from decade to decade is calculated
which may be either positive or negative.
below.
Pn = P + nI +
n(n + 1)
2
x
I = average increase in population per decade
61

3.7.4) Decreased Rate of Growth Method
 Also known as changing rate of increase method.
 Decreasing value of the percentage increase in population from decade to
decade is assumed to be constant.
below.
Pn=P 1+
r−r′
100
1+
r−2r′
100
…… 1+
r−nr′
100
r = percentage increase in population in the last decade
62

The population actually grows according to the logistic or
S-curve.
63
Fig: Logistic or S- Source:
study.com
Source: prof .Dr.B R K,water supply
engineering

Numerical on Population Forecasting and Water
Demands
Q. Estimate the population of a town for design year 2030 AD by all four
methods. The census data are as follows.
64
Year Population
1970 40000
1980 45000
1990 55000
2000 62000

65
Year Population
Increase in
population
Percentage
increase in
population
Incremental
increase in
population
Decrease
in
percentage
increase in
population
1970 40000
1980 45000 5000 12.50
1990 55000 10000 22.22 5000 9.72
2000 62000 7000 12.73 -3000 -9.49
Total 22000 47.45 2000 0.23
Average 7333 15.82 1000 0.115
Solution:

1) Arithmetical Increase Method
Here,
P = present(2000) population = 62000
I = average increase in population per decade = 7333
We have,
Pn = P + nI
So, P(2030) = 62000 + 3*7333 = 83999
66

2) Geometrical Increase Method
Here,
r = average percentage increase in population per decade =
15.82
We have,
Pn= P 1 +
r
100
n
So, P(2030) = 62000 *(1+15.82/100)^3 = 96326
67

3) Incremental Increase Method
Here,
I = average increase in population per decade = 7333
x = average incremental increase in population per decade = 1000
We have,
Pn= P+nI+
n n+1
2
x
So, P(2030) = 62000 + 3*7333 + 3*((3+1)/2)*1000 = 89999
68

4) Decreased Rate of Growth Method
Here,
r = percentage increase in population in the last decade = 12.73
r’= average decrease in percentage increase in population per decade = 0.115
We have, Pn=P 1+
r−r′
100
1+
r−2r′
100
…… 1+
r−nr′
100
So, P(2030) = 62000*(1+(12.73-0.115)/100)*(1+(12.73-2*0.115)/100)
*(1+(12.73- 3*0.115)/100)
= 88277
69

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