This presentation is about urban water demands and assessment for the present and design periods

1. Water Demand

2. Water Demand
• Designed capacity of the water supply system (WSS)
– Meeting water demands at the end of the design period
– Design period: service life of different components of a water
supply system (varies from 15 years to 100 years)
• Water demands at the end of the design periods are basis for
the water supply systems design
– Water demands at each of the supply nodes may be needed
• Average Day Demand (ADD); Maximum Day Demand (MDD);
and Peak Hour Demand (PHD) are actually required
– ADD is annual water consumption divided by 365 days
– MDD is taken as 1.8 times the ADD
– PHD is taken as (1.5/24) MDD (distribution pumps, reservoirs
and system are designed for the PHD)
• Water demand = (Per capita demand)EDP x (Population)EDP
• Using urban population history, (Population)EDP is forecasted

3. Design Period
• Usually taken as 30 years after completion of the project
– 50 years for certain components and 15 years for certain other
components
– Time lag between design and completion of project can be 2 to 5 years
• Future expansion and duplication provisions can be incorporated
into the project
• Water supply should match with water demand at the end of design
period
– Water requirements at the end of the design period should be known
– Requires population and its spatial distribution at the end of the
design period.
• Commercial, institutional and industrial development patterns of
the city should be known
• Life styles and Improvements in living standards affect the water
demands
• Water conservation measures (source minimization and recycling
and reuse of treated effluents) minimize water demands

6. Per capita water demand
• Diverse urban water demands need expression as per capita
water demands
– Residential, commercial, institutional, industrial, public &
ecological, and fire water (and unaccounted for water!)
• Assorting the water demands between the duel water supply
systems may also be needed
– Virgin water supply systems
– Reclaimed and local water supply systems
• Per capita water demand is dynamic and changing
– Currently increasing but may show a decreasing trend in future
• Per capita demand varies widely among the urban population,
and average per capita demand must be considered
• Water demands are also influenced by
– Water availability and supplies
– Water costs and water charging
– Water conservation measures

7. Water demands of urban population
• Residential water demands
– Indoor uses: Toilet flushing, Bathing, Washing clothes, Kitchens
(cooking and drinking), Wash basins (miscellaneous washing),
Desert coolers and Miscellaneous (house cleaning!) uses.
– Outdoor uses: Kitchen gardening and irrigation of lawns and
hedges; Car wash and vehicle cleaning; Yard/road wetting, etc.
• Commercial and institutional water demands
– Shops, molls and markets
– Food joints, restaurants and hotels
– Clinics, nursing homes, health centers and hospitals
– Cinema houses, concert halls and theaters
– Temples and other religious places
– Schools, colleges, institutions and universities
– Offices and administrative buildings
– Railway stations, bus stations, air ports and sea ports

8. Water demands of urban population
• Industrial water demands (including animal keeping)
– Number, type and size of industries and their water intensities
• Public and ecological water demands
– Public taps
– Public urinals and community toilets
– Swimming pools and community baths
– Street washing/wetting
– Sewer flushing
– Irrigation of public parks and gardens
– Public fountains
• Fire water
• Unaccounted for water
– Leaks
– Wastage of water
– Unauthorized and illegal connections

9. Factors affecting per capita water demands
• Size of the city:
– Demand increases with size
– Fluctuations in demand are larger with lower population size
• Climate conditions (temperature, precipitation, wind) and season
– Water demands peak during summer months
– Fire demands are higher in summers (hourly demands increase)
• Commercial, institutional and industrial development and activities
• Population density and urban landscaping: Public and ecological
uses of water are influenced.
• Housing: Slums, independent houses and multistoried buildings;
Ground floor dwellings or dwellings in the other floors; Per capita
floor area and plot area.
• Income groups (low, middle and high income groups, and EWS) and
Standard of living
– High income households consume 250-400 LPCD
– For EWS (economically weaker sections) 135 LPCD requirement
– Some households consume as low as 40 LPCD water

10. Factors affecting per capita water demands
• Social and cultural conditions and life styles: Habits, social
status, and customs of people
• Time of the day and day of the week
– Normal days, weekend days, and festive days or special days
– Most of the day’s water is consumed between 6 – 10 AM and
between 4 – 8 PM (demand for the rest 16 hrs is negligible)
• Quality, quantity and availability of water
– Reliability of water supply
– Water supply patterns (continuous and intermittent supplies)
– Water pressure in the water distribution system (Increasing
pressure increases wastage and leaks)
– Water metering and charging
• Water conservation measures
– Use of water efficient taps, showers, washing machines, toilet
flushes, garden hoses, etc.

11. 1. For communities of <20,000 population
Water supply through stand posts 40 LPCD
Water supply though house service connections 70 LPCD
2. For communities with 20,000 to 1,00,000 population
(with full flushing system)
100 to 150 LPCD
3. For communities with >1,00,000 population (with full
flushing system)
150 to 200 LPCD
Of the 150-200 LPCD 45 LPCD is meant for toilet flushing
For LIG (low income group) and EWS (economically weaker section) housing
water requirements are reduced to 135 LPCD
IS 1172 (1993, Reaffirmed 2007): Code of basic requirements for
water supply, drainage and sanitation (4th revision).
Typical domestic water demand in India: 135 LPCD
Bathing: 55 LPCD (20) Toilet flushing: 30 LPCD (40)
Cloths washing: 20 LPCD (25) Utensil washing: 10 LPCD (20)
Cooking and Drinking:10 LPCD (7) House washing/cleaning: 10 LPCD
Urban water requirements
(Outdoor uses, and uses like desert coolers not considered; Too much water
for bathing and relatively less water for toilet flushing and utensil cleaning)

12. 1. Factories with bath room facilities 45 LPCD
Factories with no bathroom facilities 30 LPCD
2. Hospitals with <100 beds (including laundry facilities) 340 LPCD
Hospitals with >100 beds (including laundry facilities) 450 LPCD
Nurses’ homes and medical quarters 135 LPCD
3. Hostels 135 LPCD
Hotels 180 LPCD
Restaurants 70/seat
4. Offices 45 LPCD
5. Cinema houses, concert halls and theaters 15/seat
6. Day schools 45 LPCD
7. Boarding schools 135 LPCD
8. Railway (no express/mail stops), bus stations and sea ports* 45/25# LPCD
Junction railway stations & stations with express/mail stops* 70/45# LPCD
Terminal stations* 45/45# LPCD
9. Air ports (international and domestic)* 70/70# LPCD
* Average number of passengers handled and staff and vendors are considered
# Requirement for without bathing facilities
Commercial and institutional water requirements (IS 1172)

13. Fire Water Requirements
For cities/towns with population <1,00,000 3600 L/min/50,000
population for 2 hr duration
For cities with population 1,00,000 to
3,00,000
1800 L/min./50,000
population for 2 hr duration
For cities with population >3,00,000 1800 L/min./1,00,000
population for 2 hr duration
Sufficient fire water should be available within 1 Km2 area.
For civil defense towns/cities the fire water requirements are doubled.
High rise buildings areas should have at least one fire water tank of 220 m3
capacity in every 1 km2 area.
IS 9668 (1990, Reaffirmed 2010): Provision and maintenance of
water supplies for fire fighting – code of practice (1st revision).
High risk areas (bazars, commercial centers, high rise buildings,
warehouses, industrial complexes, etc.
Extra high risk areas (petrochemical complexes)
Kuiching’s formula for fire water
demand estimation in Indian cities
populationisP
minisQHere
P
Q .min/,
1000
128.3 3


14. Public use demand: 5% of the total consumption
Public parks: 1.4L/m2./day
Street washing/wetting): 1.0 to 1.5 L/m2/day
Sewer cleaning: 4.5 LPCD
Industrial water demand: 20-25% of the total city water demand
Allowances for leaks, wastes and thefts: 15%
Average Indian town water demands
Domestic: 135 LPCD – 50% (65-300: 160 – 35%)
Commercial, institutional and industrial: 40 LPCD – 15% (45-450: 135 – 30%)
Public use: 25 LPCD – 9% (20-90: 45 – 10%)
Fire demand: 15 LPCD – 6% (fire + public use)
Losses, Wastage and thefts: 55 LPCD – 20% (45-150: 62 – 25%)
Total: 270 LPCD (402 LPCD)
Other water requirements (IS 1172?)

15. Population Forecasting
• Population projections are needed at the end of the design
period and for the intermediary period (+15, +30 & +50 years)
• Area wise population projections may be needed
• Trends in population growth in the recent past become basis
for future population projections
• Population to be served depends on population influx and
outflux; birth and death rates; annexation of new areas
• Many methods can be used
– Graphical methods
– Sigmoid growth (logistic growth model)
– Arithmetical increase method
– Incremental increase method
– Geometrical increase method
– Decreasing rate of growth method
– Method of density
• Selection of the method of forecasting is very important

16. Sigmoid growth (logistic growth model)
• Gives complete trend of growth of the city right from the
beginning to saturation limit of population
Population forecasting

17. Geometrical increase method / uniform rate of increase method
– Applicable for growing towns with vast scope for expansion
– Assumes uniform rate of increase
– Find decadal rate of increase and obtain geometric mean
– Uniform rate of increase: take average decadal rate of increase
Population forecasting

18. Decreasing rate of growth method
– Find saturation population size, find population growth rate
constant and forecast population
– Alternatively find average decrease of the rate of the population
growth is calculated and used
Population Forecasting

19. Population Forecasting
Arithmetical increase method
– Applicable to large old cities that achieved saturation conditions
and showing constant population growth rate
– Valid if approximately equal incremental increases have
occurred between recent censuses.
– Average increase of population per decade is calculated from
the past population records

20. Population Forecasting
Incremental increase method
• Increment in the arithmetical
increase is determined and
used
• Average of increase in
population is taken as per the
arithmetic method and to this,
average of the net incremental
increase (one for every future
decade) is added
• a progressive decrease in the
average increase can also be
adopted
 
2
1
030
Ynn
nXPP


‘n’ is number of decades
‘X’ average arithmetic increase
‘Y’ is average incremental increase

21. Graphical method
The city in question considered
The cities similar are taken into
consideration
Population Forecasting

22. Water Demand Assessment
Area/sector/zone wise demand assessments needed
Average Day Demand (ADD), Maximum Day Demand MDD) and
Peak Hour Demand (PHD) needed
Can be done from the forecasted population, per capita water
consumption and service factor values
Wdn = (Pn x C x F ) + Dn
Wdn = water demand at the end of year “n”
Pn = projected population at the end of year “n”
C = per capita consumption at the end of year “n”
F = service factor at the end of year “n” (population fraction served)
Dn = additional demand at the end of year “n”
– Knowing per capita water demand is a problem
– Only domestic demands (commercial and institutional
demands!) assessed – assessment of Dn is a problem
Demographic data, stock data and end use data all influence the
water demand – technology influences

23. Water Demand Assessment
Clearly delineate the service area
– Current service area and proposed expansion of the service area
are shown on a map
Make population projections
– Subtract the population that will not be served (other on-site
sources of water – rainwater, borewell water may be used)
Find current per capita water use
– Historical data may be used ( preferably of last 5 years)
Find per capita water use to be used in the assessment
– Make conservation corrections to per capita water use
– Make adjustments to the unaccounted for water (UFW)
Consider large independent users (industrial, institutional and
commercial users) separately
– Population equivalents or equivalent residential units
Make water demand assessments

24. Water Demands
The demand assessment should include
• Residential, Commercial, Institutional and industrial demands
• Public water, ecological water and other special water demands
• Fire fighting demand
• Unaccounted for water (wastage, leakage, illegal taping, damaged
meters)