The document discusses the importance of water supply systems in meeting various domestic, public, and industrial needs, emphasizing the significance of water quality and quantity. It outlines the data collection process for designing water supply schemes, including sources of water, demand estimation based on population, and various types of water demand. Additionally, it covers methods for forecasting population growth and their implications on water demand projections.

1. Environmental Engineering- I
By
Akash Padole
Department of Civil Engineering
Water Demand

2. Need for Water Supply Scheme
• People depend on water for drinking, cooking,
washing, carrying away wastes, and other domestic
needs.
• Water supply systems must also meet requirements
for public, commercial, and industrial activities.
• In all cases, the water must fulfill both quality and
quantity requirements
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3. Data Collection for water supply scheme
• Sources of water
• Quantity of water
 Population
 Water demand
 Design period
• Quality of water
• Topographical survey
 Place for Water treatment plant
 Probable sites for ESR
• Map of Serving Area
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4. Sources of water
Sources of
Water
Ground
Water
Infiltration
galleries,
springs, well
Surface
Source
River, Pond,
Lake
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5. Underground water sources
• Underground water is generally available
 Infiltration galleries
 Infiltration wells
 Springs
 Wells including tube wells
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6. Infiltration wells
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7. Surface source of water
River
Pond / Lake
Stream
Reservoir
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8. Selection criteria for Source
 Quality and quantity
 Distance between source and supply area
 Transportation cost ( Source to WTP to Consumer)
 Treatment Cost (depends on quality)
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9. Design Period
• The future period of number of years for which a
provision is made in designing the capacities of the
various components of water supply scheme is
known as the Design Period.
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10. • Design period is estimated based on the following:
– Useful life of the component, considering
obsolescence, wear and tear, etc.
– Expandability aspect.
– Anticipated rate of growth of population,
including industrial, commercial developments &
migration-immigration.
– Available resources.
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11. Design periods of different component of a
water supply scheme
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12. Water quantity requirements
• Basic needs to be satisfied by A piped water supply
include:
– Domestic Needs- Drinking, Cooking, Bathing, Washing,
Flushing of Toilets
– Institutional Needs
– Public Utilities – Street Washing, Flushing Of Sewers,
Watering In Public Parks
– Industrial & Commercial
– Fire Fighting
– Requirement For Livestock
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13. Types of Water Demand
1. Domestic Demand
2. Industrial and Commercial Demand
3. Fire Demand
4. Demand for public use
5. Compensate losses demand
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14. 1. Domestic Demand
• This includes the water required in private building for
drinking ,bathing, gardening, sanitary purpose, etc.
• As per IS : 1175-1983
200 l/c/d (with fully flushing system)
135 l/c/d (for weaker sections and LIG)
• Domestic Water Demand is @ 55 to 60 % of total water
demand
IS : 1175-1983
(Code of Basic requirements of for water supply , drainage and sanitation)
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15. Water Requirements For Domestic Purposes
• IS: 1172 – 1993, GIVES THE BREAKUP AS FOLLOWS:
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16. 2.1 Industrial Demand
• It represents the water demand of industries which are
earlier existing or are likely to be started in future.
• As per IS :
– 50 l/c/d (for normal industries )
– 450 l/c/d (industrial cities)
• The water required by factories such as 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.
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17. IND. TYPE UNIT OF PROD.
WATER REQUIREMENT
(KL / UNIT PROD.)
AUTOMOBILE VEHICLE 40
DISTILLERY KILOLETER OF ALCOHOL 122-170
SUGAR TONNE OF CANE CRUSHED 1-2
STEEL TONNE 200-250
SPL. QLTY PAPER TONNE 400-1000
LEATHER 100M KG (TANNED) 4
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18. 2.2 Commercial demand
• Water requirement for institutions , hotels , schools,
colleges, offices.
• As per IS :
– 20 l/c/d (for normal commercial area)
– 50 l/c/d (highly commercial area)
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19. SR NO TYPE OF INSTITUTION
LPCD
RECOMMENDED
1
HOSPITALS (INCL LAUNDARY)
NO OF BEDS > 100
NO OF BEDS < 100
450 PER BED
340 PER BED
2 HOTELS 180
3 HOSTELS 135
4 NURSES’ HOMES & MEDICAL QUARTERS 135
5 BOARDING SCHOOLS / COLLEGES 135
6 RESTAURANTS 70 PER SEAT
7 AIR PORTS & SEA PORTS 70
8
JUNCTION & INTERMEDIATE STNS (INCL MAIL
& EXPRESS STOPPAGE
70
9 TERMINAL STATIONS 45
10
INTERMEDIATE STNS (EXCL MAIL & EXPRESS
STOPPAGE)
45
11 DAY SCHOOLS / COLLEGES 45
12 OFFICES 45
13 FACTORIES 45
14 CINEMAS, CONCERT HALLS, THEATERS 15
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20. 3. Fire Demand
• In populated or industrial area fires generally
breakout and may lead to serious problem.
• For control that situation require sufficient quantity
water that is called Fire Demand.
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21. Fire Fighting Required Calculation
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22. Akash Padole 22
3.

23. 4. 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.
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24. • The requirements of water for public utility shall be
taken as
Sr.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
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25. 5. Compensate Losses demand
• Wastage of water due to defective pipe joints.
• Careless consumer keep tap open
• Unauthorized water connection.
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26. 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
Quantity (q) = Per capita demand x Population
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27. • 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 -------- 135 litres/c/d
Industrial use -------- 40 litres/c/d
Public use -------- 25 litres/c/d
Fire Demand -------- 15 litres/c/d
Losses, Wastage and thefts ---- 55 litres/c/d
--------------------------
Total : 270 litres/capita/day
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28. • Seasonal variation: The demand peaks during
summer. Firebreak outs are generally more in
summer, increasing demand. So, there is seasonal
variation.
• Daily variation depends on the activity People draw
out more water on Sundays and Festival days, thus
increasing demand on these days.
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29. • 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 is
taken. During other hours the requirement is less.
0
2
4
6
8
10
12
14
16
18
0 4 8 12 16 20 24
Water
demand
Time (Hr.)
Hourly Water demand
Water demand
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30. • Moreover, if a fire breaks out, a huge quantity of
water is required to be supplied during short
duration, necessitating the need for a maximum rate
of hourly supply.
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31. Fluctuations in Rate of Demand
Average Daily Per Capita Demand
= (Volume of water required in a year)/(365 x Population)
• If this average demand is supplied at all the times, it
will not be sufficient to meet the fluctuations.
• Variation of demand is considered as follows:
Maximum Daily demand = 1.8 x Average daily demand
Maximum Hourly demand = 1.5 x Maximum daily demand
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32. • Maximum hourly demand i.e. Peak demand
• Maximum Hourly demand = 1.5 x Maximum daily demand
= 1.5 x (1.8 x Average daily demand)
= 2.7 x Average Daily demand
Maximum hourly demand = 2.7 x ( Average Daily demand)
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33. t = time (>= 1day)
= Max demand/ Average demand
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34. t = 1 day (Daily)
t = 7 days (Weekly)
t = 30 days (Monthly)
t = 365 days (yearly)
Time (in days) p (Max demand/ Average demand)
1 1.80
7 1.50 (1.48)
30 1.28
365 1 (0.99)
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35. Coincident Draft:
• It is extremely improbable that a fire may break out
when water is being drawn by the consumers at
maximum hourly draft.
= (Maximum hourly demand)
= (Maximum daily demand + fire demand)
whichever is more.
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36. Maximum daily demand= 1.8 Avg. daily demand
= 1.8 x q
q = population x per capita
= 75000 x (150 lpcd)
= 11250000 lit /day
MDD = 1.8 x 11250000 lit/day
= 20250000 lit/day
= 20.25 M lit/day
= 20.25 MLDAkash Padole 36

37. Factors affecting per capita demand
• Size of the city: Per capita demand for big cities is
generally large as compared to that for smaller towns.
• Presence of industries
• Climatic conditions
• Habits of people
• Quality of water: If quality of water is good, the
consumption will increase .
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38. • Pressure in the distribution system
• System of water supply (24 hrs)
• Cost of water
• Policy of metering and charging method: Water tax is
charged in two different ways: on the basis of meter
reading and on the basis of certain fixed monthly
rate.
• Efficiency of water works administration: Leaks in
water mains and services; and unauthorised use of
water can be kept to a minimum by surveys.
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39. FACTORE AFFECTING THE WATER DEMAND
Big city
Size of the city Small towns
Example: Delhi 244 l/c/d Sangali 135 l/c/d
Climate condition
less in winter
more in summer
Cost of water
rate demand rate demand
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40. Industry
Quality of water
good demand demand
bad
demand demand
More industries
Less industries
Habit of people
demand demand
EWS MIG
(Living style)
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41. Supply system
Bad Supply
Distribution System
Good supply
demand
Pressure
high
Pressure
low
demand
demand demand
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42. Population Forecasting
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43. Birth, Death, Migration
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44. 1. Arithmetic Increase Method
2. Geometric Increase Method
3. Incremental Increase Method
4. Decreasing Rate of Growth Method
5. Simple Graphical Method
6. Comparative Graphical Method
7. Ratio Method
8. Logistic Curve Method
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45. Arithmetic Increase Method
• This method is based on the assumption that the
population is increasing at a constant rate.
dP/dt= const
• The rate of change of population with time is
constant.
• The Population after ‘n’ decades can be determined
by the formula
Pn = P0 + n. x
where,
P0 → population at present
n → No. of decades
x → average of Population increase of ‘n’ decades
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46. Geometric Increase Method
• In this method, the rate of growth of population is
assumed to be constant.
• But the increase in population is compounded over the
present population to compute the future population.
• The average percentage of growth of last few decades is
determined.
• The Population at the end of ‘n’ decades is calculated by-
where
P0 → population at present
r → average percentage of growth of ‘n’ decades
r = t √ r1.r2....rt
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47. Incremental Increase Method
• In this method, the rate of growth of population is
not constant.
• It may either increase or decrease depending upon
the given past information.
• In this method, average incremental increase over
increase in population is also considered to compute
the future population.
2
x is Average increase in population
y is Average incremental increase over increase in population
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48. • Arithmetic increase method gives the lowest value of
population forecast, hence suitable for old cities or
towns (developed cities)
• Whereas Geometric Increase Method gives the
highest value of population forecast, hence suitable
for young cities or towns.
• GOI manual recommends the use of GM method to
calculate rate of growth of population.
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49. Logistic Curve Method
• Logistic curve method is based on the hypothesis and
based on laws of probabilities that when varying
influences do not produce extraordinary changes, the
population would probably follow the growth curve.
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50. Akash Padole 50

51. Pt = ? t = 60
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52. Akash Padole 52

53. Q : From a given information, compute the population
of a town in 2026 using all the 3 methods.
Year Population
2016 26,000
2017 29,000
2018 35,000
2019 43,000
2020 47,000
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54. P0 = P2020 = 47,000
n = 6 (= 2026-2020)
Pn = ?
Year Population
2016 26,000
2017 29,000
2018 35,000
2019 43,000
2020 47,000
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55. Arithmetic Increase Method:
𝑥 =
21
4
= (5.25) x 1000 = 5250
Year Population
(x 1000)
Increase in
Population
2016 26 -
2017 29 29-26= 3
2018 35 35-29= 6
2019 43 43-35= 8
2020 47 47-43= 4
Total = 21
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56. Pn = P0 + (n. x)
P2026 = 47,000 + (6 x 5250)
= 78,500
P2026 =78,500 …AM
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57. 𝑟 = 11.5 𝑥 20.69 𝑥 22.85 𝑥 9.30
1
Geometric Increase Method:
Year
Population
(x 1000)
Increase in
Popl. (x1000)
Rate of growth of
Population
2016 26 - -
2017 29 29-26= 3 =
3
26
𝑋 100 = 𝟏𝟏. 𝟓𝟑%
2018 35 35-29= 6 =
6
29
𝑋 100 = 𝟐𝟎. 𝟔𝟗%
2019 43 43-35= 8 =
8
35
𝑋 100 = 𝟐𝟐. 𝟖𝟓%
2020 47 47-43= 4 =
4
43
𝑋 100 = 𝟗. 𝟑𝟎%
= 15%
4
𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑖𝑛 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
𝑥 100
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58. P2026 = 47,000 x (1 +
15
100
)
= 1,08,713
P2026 = 1,08,713 …GM
6
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59. Incremental Increase Method:
Year
Populatio
n
(x 1000)
Increase in
Population
(x 1000)
Incremental increase in
population
(x 1000)
2016 26 - -
2017 29 29-26= 3 -
2018 35 35-29= 6 6 - 3 = 3
2019 43 43-35= 8 8 - 6 = 2
2020 47 47-43= 4 4 - 8 = -4
𝑦 =
3 + 2 − 4
3
= (0.333) x 1000 = 333.33
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60. P2026 = 47,000 + (6 x 5250) + {
6(6+1)
2
} x (333.33)
= 85,500
P2026 = 85,500 …IIM
2
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61. AM < IIM < GM
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62. Population in 1991 will be?
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