water supply planning

1. LECTURE 1
INTRODUCTION
Instructor : Engr. Beenish Akbar Khan
B.Tech Civil
Iqra National University (INU)
Water Supply & Waste
Water Management

2. WATER SUPPLY PLANNING
It generally consist of :
1. Collection Works
2. Purification Works
3. Transmission Works
4. Distribution Works
Collection Works:
Tape water continuously adequate in volume for present &
reasonable future demands. OR
Convert an intermittently (from time to time) insufficient
source into a continuous adequate supply.
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3. WATER SUPPLY PLANNING
Purification Works:
When the quality of raw water collected is not satisfactory,
purification works are introduced to render (purify) it,
suitable for its intended use.
Transmission Works:
To convey the collected and purified waters to the
community.
Distribution Works:
To supply treated water to the consumers in the desired
quantity and at adequate pressures. 3

4. WATER DEMAND
It is necessary to find total quantity of water (Q) required
for various purposes by the city for the design of water
supply scheme.
 Duty of engineer is to find “Q” & suitable water source.
 For design of water supply scheme: Determine total
yearly demand variations in the demand rates.
 The actual demand can be found by certain empirical
formulas and thumb rule.
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5. ESTIMATION OF DEMAND FOR WATER SUPPLY
1. Design period
2. Design population (population forecasting)
3. Design flow ( or per capita consumption)
4. Design area
1. Design Period:
It is the number of years in future for which the excess
capacity is provided, the proposed system, its component
structures and equipment's are to be adequate.
(Excess capacity = Use larger pipe diameter in advance)
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6. ESTIMATION OF DEMAND FOR WATER SUPPLY
Selection of design period :
1. Physical (useful) life of structure
2. Ease or difficulty of extension of facility
3. Rate of growth of population
4. Rate of interest on the borrowed money
5. Lead time (i.e. time from execution to completion of a
project)
6. Economies of scale “a” (i.e. profit)
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7. ESTIMATION OF DEMAND FOR WATER SUPPLY
2. Design Population:
It is the number of people to be served in future. Increases
in the demand on a water supply system over a period of
years result from;
I. Population growth
II. Increase per capita consumption
III. Industrial development
Since it would be uneconomical & impracticable to augment
(expand) the system year by year to meet the growing
demand. 7

8. ESTIMATION OF DEMAND FOR WATER SUPPLY
Design Population:
Therefore each component is designed to satisfy the
estimated demand at the end of design period. In the early
part of the period , some of the components will therefore
not be operating at their full capacity.
Long design periods (50 yrs) are suitable for dams, tunnels
and large canal's which are difficult to enlarge. Short design
periods (i.e. 10 – 30 yrs) are suitable for pumps, pipelines ,
treatment plants and wells; which can be duplicated,
replaced or extended more easily.
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9. ESTIMATION OF DEMAND FOR WATER SUPPLY
3. Design Flow: (lpcd or gpcd)
It is the rate of water flow in terms of “per capita
consumption”. It is annual average quantity of daily water
required by a person.
It is based on complete one year supply of water.
4. Design Area:
It is the area to be served in future. Eg. Recreational area
(zoo, parks) , residential area, commercial and industrial
area. 9

10. TYPES OF DEMAND
1. Domestic water demand (44%)
2. Commercial (15%) and industrial (24%) demand
3. Demand for public use (9%)
4. Loss and waste (8%)
5. Fire demand
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11. DOMESTIC WATER DEMAND
It includes water for drinking, bathing, cooking &
washing. It depends upon habits, social status, climatic
conditions and customs of people.
In Pakistan average domestic consumption is 125 lpcd.
For developing countries it is 350 lpcd.
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12. COMMERCIAL & INDUSTRIAL DEMAND
Commercial centers : water requirement is 45 lpcd.
 Office building
 Stores and hotels
 Shopping centers
 Schools, cinema houses
 Mosques, railway and bus stations.
Industrial demand is 20 – 25 % of total demand.
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13. Public Use:
Water furnished to public buildings and used for public
services. Water for buildings, sprinkling and cleaning of
roads, sewers, public parks, gardens and fire protection etc.
It is 9 % of total demand.
Loss and Waste:
Water which is “unaccounted for” in the sense that it is not
assigned to a specific user.
Unaccounted for water is due to errors in meter readings,
unauthorized connections, and leaks in the distribution
system.
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TYPES OF DEMAND

14. FIRE DEMAND (F)
 It is the total amount of water in a year to turn off fire.
 The actual amount of water used for fire fighting in a
year is small, the rate of use is high.
 However during a fire, the rate of demand increases.
Thus, it will effect the capacity of pumps, reservoirs and
distribution pipes.
 F is defined as the quantity of water required to turn off
the largest possible fire in the area.
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15. FIRE DEMAND
 It can be found from:
 Minimum number of streams ( 5 at least)
 Discharge (Q) through each stream (200 – 250 gpm)
 Duration of fire (at least 4 hours)
 No. of simultaneous fires.
 F is function of population (p).
 Low risk areas – P ≤ 2500 duration of fire:4-5hrs
 High risk areas - P > 2500 duration of fire:10 hrs
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16. EMPIRICAL FORMULA FOR FIRE DEMAND
1. National board of fire under-writers formula (NBFU):
 𝑄 = 1020 𝑃( 1 − 0.01 √𝑃)
 Q is fire flow / demand in gpm.
 P is population in 1000’s.
2. Insurance services office (ISO) formula:
 F = 18 C√A
 F = Required fire flow in gallon/min or gpm or l/min/3.78
 A = Floor area (ft2) excluding basement (m2 * 10.76)
 C = Co-efficient related to type of construction
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Type of construction Value of C
Wooden frame structure 1.5
Ordinary frame structure 1
Non combustible structure 0.8
Fire resistant structure 0.6

17. EMPIRICAL FORMULA FOR FIRE DEMAND
4. Kuichling Formula:
It is based on fire stream flow of 250 gpm.
𝑄 = 750√P
Q in gpm
P in 1000’s
5. Freeman’s Formula:
𝑄 = 250
𝑃
5
+ 10
Q in gpm
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18. FIRE DEMAND PROBLEMS
1) Calculate the fire demand of water for a town having a
population of 81,000 by National Board of Fire
underwriters formula?
Required: Q = ?
Solution:
𝑄 = 1020 𝑃( 1 − 0.01 √𝑃)
= 1020 81 ( 1 - 0.01 √81)
= 1020 * 9 ( 1 - 0.01 * 9)
Q = 8354 gpm
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19. FACTORS AFFECTING WATER USE
1. Size of city
2. Climatic conditions (summer = increase in water use)
3. Characteristics of population
4. Industrial & commercial activities
5. Quality of water (good quality = high use of water)
6. Pressure (high pressure = greater use)
7. System of water supply ( good system maintenance =
reduce loss & waste)
8. Cost of water (high price = reduce water use)
9. Metering (it reduce water consumption)
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20. THE END
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