Unit-1
WATER
SUPPLY SYSTEM
Sources of Water

Surface Water:
Example: River, Pond, Lake, Reservoir, etc.

Ground Water:
Example: Well, Tube well, Aquifers, Springs etc.
Water Supply System
WATER SUPPLY SYSTEM
System components
Catchment
Treatment
4
Water supply and quality
Land use
Abstraction method and location
Filtration
Coagulation
Clarification
Disinfection
Distribution
User
Networks
Service reservoirs
Tankers
General public
Potable
Supply flow diagram
Tropical
forest
5
River
catchment 1
Run-off
Abstraction
from river
Intake
Structure
Raw water
transfer
Water
treatment
Pipe mains to
distribution system
Service Reservoir
Distribution system
Users
City 1
Water Demand
Content
1.
Introduction to Water Demand
2.
Types of Water Demand
3.
Factors affecting to water demand
1. Introduction to Water Demand
 The quantity of water required in order to meet
all water needs in community is known as water
demand.
 When and why it is required ???
 Per Capita Water Demand :-
It is the annual average amount of daily water
required by one person is called as P.C.D.
2. Various types of Water Demand
A.
Domestic Water Demand
B.
Industry water demand
C.
Institutional & commercial Water Demand
D.
Public Water Demand
E.
Fire Water Demand
F.
Compensate Losses demand
A. Domestic Water Demand
 Water required in residential buildings for : Drinking, cooking, bathing, lawn sprinkling, gardening,
sanitary purposes, etc.
 As
per IS:1172-1993, the minimum domestic
consumption for a town or a city is about 135 lpcd.
B. Industrial water Demand
 The quantity of water required by industries is called as
Industrial water demand
 Mainly depend on type and size of industry
 Normally, 50 lpcd is taken as per capita water required for
industrial needs of a city.
 Water req. by factories, paper mills, cloth mills, cotton mills,
brew mills, sugar refineries etc comes under industrial use.
C. Institutional & Commercial
 The
water required by institution such as; hospitals,
hotels, restaurants, schools, offices, colleges, corporate
buildings, railway stations etc.
 On an average, a per capita water demand of 20
lpcd is usually considered to be enough to meet
demand.
D. Public Use Demand
 The quantity of water required for public utility purpose, such
as watering of public parks, gardening, washing & sprinkling
on roads, use in public fountains, etc.
 Provision of 5% of total consumption is made while designing
the water works for a city.
 10 lpcd is normally added while computing total water req.
E. Fire Water Demand
 It
is required in densely populated city and
industrial areas, where there are chance of fire
Variations in Water
Demand & Fire
Demand
Fire
demand
 1 to 1.5 kg/cm2 – water pressure even after 4 to 5 hours.

3 Jet streams – 1100 liters/minutes.

Total amount of water required = 6 * (3*1100)*(3*60)
 No of fires * (3 jets*discharge) * (3 hours* per minute) = 35,64,000 liters/day

Amount of water required per person = 35,64,000/50 lakhs < 1 l/head/day.

The per capita fire demand is very less on an average basis but the rate at which the
water is required is very large.

The rate of fire demand is sometimes treated as a function of population.
 Q = amount of water required in liters/minute
 P = Population in thousands
Authority
Formulae (P in thousand)
American Insurance Association/ National Board
of Fire
Kuchling's Formula
Q (L/min)=4637 P (1-0.01 P)
Freeman's Formula
Q (L/min)= 1136 (P/10+10)
Buston’s formula
Q (L/min)= 5663 P
Q (L/min)=3182 P
Example-1
Q: Calculate Fire demand Using 4 different formula
for Population: 1,00,000.
Authority
Formulae (P in thousand)
American Insurance Association/ Q (L/min)=4637 P (1-0.01 P)
National Board of Fire
Kuchling's Formula
Q (L/min)=3182 P
Freeman's Formula
Q (L/min)= 1136 (P/10+10)
Buston’s formula
Q (L/min)= 5663 P
Calculate Fire demand Using 4 different formula
for Population: 1,00,000
Authority
Formulae (P in thousand)
Answer key
American Insurance Association/ Q (L/min)=4637 P (1-0.01 P)
National Board of Fire
Q = 41733 L/min
Kuchling's Formula
Q (L/min)=3182 P
Q = 31820 L/min
Freeman's Formula
Q (L/min)= 1136 (P/10+10)
Q = 22720 L/min
Buston’s formula
Q (L/min)= 5663 P
Q = 56630 L/min
Factors affecting to water
demand

Size & Type of community

Standard of Living

Climatic condition

Sewerage

System of Supply

Age of Community

Metering
Calculate daily water requirement
According to IS:1172-1993 daily water
requirement (low living standard)
Drinking
Cooking
Bathing
Clothes washing
Utensils washing
House washing
Flushing of water
closets
TOTAL
•5 litres
•5 litres
•55 litres
•20 litres
•10 litres
•10 litres
•30 litres
•135 litres per day (lpcd)
According to IS:1172-1993 daily water
requirement (high living standard)
Drinking
Cooking
Bathing
Clothes washing
Utensils washing
House washing
Gardening
•5 litres
•5 litres
•75 litres
•25 litres
•15 litres
•15 litres
•15 litres
Flushing water closets •45 litres
TOTAL
•200 litres per day (lpcd)
Variations in Demand

Per capita demand (litre/day per person)
=
𝑇𝑜𝑡𝑎𝑙 𝑌𝑒𝑎𝑟𝑙𝑦 𝑊𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑖𝑡𝑦 𝑖𝑛 𝑙𝑖𝑡𝑟𝑒𝑠
365 𝑋 𝐷𝑒𝑠𝑖𝑔𝑛 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
Variations in Demand
The following are generally adopted

Maximum daily demand = 1.8 X Average Daily demand

Maximum hourly demand = 1.5 X

Peak Factor/fluctuation (p): Ratio of the maximum flow to the
average flow in a water system
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝐷𝑎𝑖𝑙𝑦 𝐷𝑒𝑚𝑎𝑛𝑑
24
Assessment of Normal Variations

Maximum Daily consumption
= 180% of Average daily consumption
= 1.8 * Average daily demand(q)

Maximum hourly consumption
= 150 % 0f Average hourly
consumption of the max. day
= 1.5 * (Max. Daily demand/24)
= 1.5 * (1.8 * q)/24 = 2.7 (q/24)

How this 180% considered????
Goodrichs Equation, (%fluctuation)
p = 180 (t)^-0.10 , when t (days) is
greater than or equal to 1.
where p = percent annual average draft
for the time t in days & t= Time in days

Maximum weekly and monthly
demand??
The peak coefficient is obtained as the volume of the water required at the peak hour over the average,
hourly flow demand volume.
Variations in Water Demand (Draft)

Per capita demand in litres per day per head can be calculated as,
=
𝑇𝑜𝑡𝑎𝑙 𝑌𝑒𝑎𝑟𝑙𝑦 𝑟𝑒𝑖𝑟𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑖𝑡𝑦 𝑖𝑛 𝑙𝑖𝑡𝑟𝑒𝑠
365 ∗𝐷𝑒𝑠𝑖𝑔𝑛 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
For an average Indian city, as per IS 1172 the per capita demand(q) is given as per below table.
Use
Demand in l/head/day
Domestic
200
Industrial
50
Commercial
20
Public
10
Waste & losses
55
Total (Per capita demand)
335
Coincident Draft

Total Draft is generally taken as sum of maximum daily demand and
fire demand or maximum hourly demand and fire demand
whichever is more

The maximum daily demand when added to fire demand for
working out total demand is known as coincident draft.
Effects of variations in demand on design
capacities of different water supply
Source of Supply
scheme
• Maximum daily consumption or sometimes Average daily consumption
Pipe mains
• Maximum daily consumption
Water treatment plant
• 2 times the average daily water demand
Pump
• 2 Average daily demand
Distribution demand
• Maximum hourly or daily or coincident draft whichever is more
Service reservoir
• Average daily consumption
Example 2
Q: Estimate following details for given data:

Daily Water Demand or Average daily water demand

Daily variations in Water Demand or Maximum daily water demand

Hourly Variation or Maximum hourly variation

Fire demand Using 4 different formula
 Coincident Draft
Data: Population of city: 5,00,000 & Average consumption per capita is
250 ltrs/day
Also calculate capacities of various components of water supply
scheme for the given data
Example 2 : Solution

Average Daily Water Demand : 125 MLD
 Maximum Daily Water Demand : 225 MLD

Maximum Hourly Variation : 14 MLD
 Coincident Draft = Max. daily draft + Fire demand
= 225 + {(80501.47*60*24)/10^6} = 340.9 MLD = 341 MLD
Example 2 : Solution
Authority
Formulae (P in thousand)
Answer key
American Insurance Association/ Q (L/min)=4637 P (1-0.01 P)
National Board of Fire
Q = 80501.47 L/min
Kuchling's Formula
Q (L/min)=3182 P
Q = 71151.68 L/min
Freeman's Formula
Q (L/min)= 1136 (P/10+10)
Q = 68160 L/min
Buston’s formula
Q (L/min)= 5663 P
Q = 126628.5 L/min
Example 2 : Solution
Component of water supply
scheme
Intake structure
Answer key
Pipe main
225 MLD
Water treatment
2 * 125 = 250 MLD
Pump
2 * 125 = 250 MLD
Distribution system
341 MLD
225 MLD
Population Forecasting Methods
1.
Arithmetic increase method
2.
Geometric increase method
3.
Incremental increase method
4.
Simple graphical method
5.
Graphical Comparison method
6.
The logistic curve method
7.
Decreased rate of growth method
8.
Zoning method
9.
Ratio & co relation method
Arithmetical Increase Method
Pn = P + ni
Geometric increase method
𝑟 𝑛
Pn = P (1 +
)
100
Where,
Pn = Future Population after n decades
P = Present population
n = number of decades
i = Average of population increase
r = average percentage increase per decade
Incremental increase method
𝑛 (𝑛+1)
Pn = P + nd +
t
2
Where,
Pn = Future Population after n decades
P = Present population
n = number of decades
t = average incremental increase per decade
d = average increase per decade
Example 1: calculate the population of a town after two
decades for following data by (a) Arithmetical Increase
method, and (b) Geometric increase method.
Year
Population
1980
25000
1990
28000
2000
34000
2010
42000
 Example 2: the population of 5 decades from 1960 to
2000 are given below. Find out the population after one,
two, and three decades beyond the last known decade
by using incremental increase method.
Year
1960
1970
1980
1990
2000
Population
25000
28000
34000
42000
47000
Simple graphical method

The population of previous years are plotted in
graph with suitable scale.

The population curve is smoothly extended and
future population is predicted.

This method extension of
experience based judgement.

It will be useful where the population growth will
be consistent.
graph
requires
Graphical Comparison method

In this method the census population of cities already developed under similar conditions are
plotted.

The curve is extended carefully by comparing with the population of some similar cities having
the similar condition of growth.
The logistic curve method

This method uses log curves and it is established long term population trends of large population centres.

𝐿𝑜𝑔𝑒 (𝑃𝑠 − 𝑃) 𝑃 - 𝐿𝑜𝑔𝑒 (𝑃𝑠 − 𝑃𝑜) 𝑃𝑜 = - K Ps t

Ps = Saturation Population

Po = Population at start point

P = Population at given time t

K = Constant
Final Formula for Population to be forecasted is,
P=
𝑃𝑠
1+
𝑃𝑆 −𝑃𝑂
−1 (−𝐾 𝑃𝑠 𝑡)
𝑙𝑜𝑔
𝑒
𝑃𝑂
Decreased rate of growth method
a

Rate of increase in population goes on
reducing, as cities approach towards
saturation.

This method is suitable where the rate of
growth have downward trend.
Zoning method

Master plan of city is prepared

Different zones are identified

Population forecasting is done on the basis of same

Example of common Population Densities which may be taken in master plan
Sr.
No.
Type of Area
No of persons per hectare
1A
Residential Area : Single
family Dwellings
10-40
1B
Residential Area : Multiple
family Dwellings
90-250
2
Commercial Area
40-75
3
Industrial Area
10-40
Ratio & co relation method

Population growth of small town to big town

Local to national population ratio is used

The graph of ratio of local to national population for different
decades are plotted for future prediction and one value of ratio is
selected.

Consistent population growth
Economic
Development
Programme
Social facilities
Communication
link
Tourism
Community
lifestyle
Pandemic
situation